REPUBLIC OF BULGARIA
MINISTRY OF REGIONAL DEVELOPMENT AND PUBLIC WORKS
2013 0075 BG- EN- ------ 20130308 --- --- PROJET
REGULATION No …
(date) ……………………..……..
For the Design, Construction and Operation of Sewer Systems
Section One
GENERAL TERMS
Article 1. (1) This Regulation defines the terms of reference in the design, construction and
operation of new sewer systems, as well as in the reconstruction of already existing sewages on urban
territories with more than 200 EI (equivalent inhabitants).
(2) For urban territories with up to 200 EI the terms will be applied as per the requirements of the
employer.
(3) Sewer systems consist of:
1. Sewage grids and related installations in urban territories;
2. Sewage collectors conveying sewage outside urban territories
3. Sewage pump stations;
4. Waste water treatment plants;
5. Waste water discharge plants.
(4) Sewer systems shall be designed and constructed in accordance with the current detailed Site
Development Plans pursuant to Article 110(1) of the Territorial Development Act (TDA), the
indispensable requirements for construction sites pursuant to Article 169 of TDA), approved investment
projects and other construction documents issued in compliance with TDA, as well as the rules and
standards of the present Regulation.
Article 2(1) This Regulation will be applied parallel to the regulatory acts and technical
specifications defining sewer systems requirements with regard to environmental protection, water and
waste management, human health protection and healthy and safe work conditions.
(2) Waste waters from industrial and agricultural buildings will be discharged into the sewer
systems in strict observance of the regulatory requirements for waste water discharge of industrial waste
waters into the sewer systems on inhabited territories, as well as in accordance with the requirements of
licences for use of water bodies for waste water discharge into the surface waters of the local sewer
system.
(3) In cases where an emergency plan is in place for parts of the sewer system under Article 35 of
the Disaster Protection Act, the requirements of the latter will be taken into consideration in the design
and operation of the system.
(4) The sewer system units are built on land plots identified in compliance with Needed Land
Regulations pursuant to the rules and standards of Regulation 7/2003 for different categories of territories
and regulated zones (revised, OG No 3/2004).
(5) Minimum protection zones are provided in compliance with Appendix 1 for water treatment
equipment and pump sewer systems, which are not subject to environment risk assessment under the
environment regulation act.
Article 3. (1) In designing, constructing and operating sewer systems, the following should be
guaranteed:
1. protection of adjacent territories from overflow; reduction of risk and of possible flood
damage under extreme conditions;
2. pollution protection of water basins/gully waters in compliance with the requirements of the
waste water discharge licence issued for the sewer system;
3. compliance with the regulatory requirements for protection of underground waters from
pollution;
4. lasting building constructions and equipment, and firm ground soil, in consideration of all
geographic, climatic and seismic factors;
5. protection of waste water treatment plants from hydraulic overloading, which might result in
reduction of their treatment capacity;
6. prevention of waste water decay and foul odours release;
7. adequate measures to offset harmful effects such as noise, vibrations, hazardous substances
release, etc.;
8. energy saving measures;
9. keeping within the prescribed economically justified operation period allowing for future
expansion and changes in the system;
10. hydraulic conductivity and functionality of the system in cases of reconstruction, changes
and/or total overhaul;
11. conditions needed for the maintenance of, and access to, parts of the system;
12. regulatory requirements for health and safety of the staff working on the system;
13. an adequate use of the planned and used construction products taking into consideration the
requirement for minimum energy consumption during system operation and their possible reuse at a
minimum harm to the environment.
(2) Sewer systems are designed for economically justified operation periods as identified by the
employer, during which the hydraulic and technological functioning of the system, as well as the specific
effect on the environment and on the system itself, should be guaranteed.
(3) The design and construction of sewer systems will be done taking into consideration the
specific features of the corrected river beds in urban territories, to guarantee normal performance of the
overflow equipment in cases of rain, and to prevent overflow of river water into the sewer system.
Article 4. Sewer systems and waste water treatment plants will be designed, constructed and put
into operation while taking into consideration their interaction and their total effect on the water quality in
water basins.
Article 5. (1) Products used for the design, construction and operation of sewer systems should be
wear-proof and resist the effects of waste waters, surface waters, soil and underground waters, as well as
the calculated internal and external pressure thereby preserving their normal function and watertight
qualities in the course of the entire operation period.
(2) In designing, building and operating sewer systems, construction products should be used
whose properties guarantee the implementation of the construction requirements pursuant to
Article 169(1) of the TDA and comply with the technical terms of reference under the Regulation on
Major Requirements for Construction Sites and the Assessment of Construction Products Compliance
with Decree 325 of the Council of Ministers of 2006 (OG No 106/2006) and EU Regulation 305/2001 of
the European Parliament and Council on Harmonized Conditions for the Marketing of Construction
Products and for cancellation of Directive 89/106/EEC (EU OJ No L88/04.04.2011).
(3) The products used in sewer systems, produced and/or marketed in EU member states and
Turkey, or legally produced in an EFTA member state, which is a party to the Agreement on the
European Economic Area (EEA), can be used for the purposes of the present Regulation if they guarantee
an identical or higher safety level pursuant to the requirements defined in the present Regulation.
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Article 6 (1) The hydraulic conductivity (capacity) of sewer systems (household and industrial) in
dry weather will take into consideration the water consumption capacity of the related water pipe systems
as well as the readings for each individual case.
(2) The period of a single overload of the sewer systems conducting rain waste water will be
identified depending on the type of urban territory and the drained site according to Table 1 of Appendix
2.
Article 7. The minimum scope and contents of the feasibility study and the investment project for
sewer systems will be done according to Appendix 3 and 4.
Article 8. A list of applicable Bulgarian standards for the design, construction and exploitation of
sewer systems can be found in Appendix 5.
DESIGN OF SEWAGE GRIDS AND RELATED INSTALLATIONS, AND OF DISCHARGE
SEWAGE COLLECTORS
Part One
GENERAL TERMS
Article 9. Sewage grids and discharge sewage collectors shall be designed to absorb and convey
the following types of waste water:
1. household waste water;
2. industrial waste water complying with the standard requirements for maximum admissible
concentration of substances at the time of their discharge into the sewer systems of inhabited places, and
with the requirements of the discharge licence;
3. rainfall waste water;
4. Infiltrating (drain and others) water
Article 10. (1) Depending on the manner of operation, the following types of sewer grids shall be
designed:
1. gravity sewer grids;
2. vacuum sewer grids;
3. pressure sewer systems
(2) Depending on their structure and technological properties, the following types of gravity sewer
grids shall be designed:
1. mixed;
2. separating;
3. semi-separating;
4. combined (mixed and separating grid)
(3) The sewer grid type shall be selected for each separate case, taking into consideration factors
such as:
1. estimations of the existing general development plan or, when there is no general
development plan in place, of the regional and/or municipal development plans;
2. assessment of the need for development of water- and sewer systems and installations in the
general development plan;
3.
type and hydraulic capacity of the existing sewage system;
4.
terrain slopes, soil types, local geological, hydrogeological, etc. conditions in urban territories;
5. presence of water basins and the typical water elevation;
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6. building density;
7. type, size and foundation depth of buildings;
8. presence of waste water treatment plants (technological scheme, current technological state of
the equipment, hydraulic and technological capacity;
9. need of sewer pump stations and their capacity;
10. standard requirements for water quality protection in water basins, including waste water
discharge licences;
11.
feasibility study data and results from the technological and economic analyses of related
variants;
12.
standard requirements for the layout of sewage pipelines and equipment;
Article 11. (1) To oversee the results in the designed separating rainwater grids, and mixed sewer
grids covering water basins of over 200 ha, computer simulation of the run off shall be used in
compliance with Appendix 6 in cases when the feasibility study has identified, and the employer has
asked for the following technical data:
1. electronically carried digital data for the existing sewer grid (i.e. type of sewer grid, type of
sewer grid system, degree of completion, spatial layout, pipe material, grid equipment, technical state,
hydraulic capacity of grid and equipment, drainage standard in l./h.d., at the initial stage of the design
period and by the end of the operation period);
2. electronically carried digital data on the existing water supply system (i.e. degree of completion,
spatial layout, technical state, physical water losses, water supply standard in l/h.d. at the initial stage of
the design period and by the end of the projected operation period of the sewer system;
3. electronically carried digital data on surface water installations (wаste water gullies) i.e. typical
water volumes, still water areas, guaranteed permanent water levels, type and spatial layout of river bed
corrections or embankment fortifications, function of the gully;
4. electronically carried digital data on simulation studies (in case such studies exist as a general
rule or have resulted from a specific assignment) on the hydraulic capacity of the existing sewer grid (in
designing reconstructions, transformations or overhauls) at typical hydraulic loads, through the use of
computer simulation models of the run off in compliance with Appendix 6
5. a digital model of the urban territory terrain reflecting developments, planning, hydrological
and hydraulic properties;
6. hydrological study data from multiannual observations updated by the hydraulic properties at
the date of design (e.g. the synchronized readings for at least one spring-summer period, by pluviographs
installed in the urban territory and complete with adjustment microprocessor for continuous reading,
storage and transfer of data on the speed and water volume in sections specifically identified for
calibration and checking of the simulation model).
(2) In cases when the design requires specific technologies and computer runoff simulation
models in compliance with Appendix 6, yet major technical data pursuant to paragraph 1 are absent, the
employer shall commission their formulation.
(3) When planning reconstruction and/or overhaul of the existing sewer grids, parallel to the
requirements inherent to their design pursuant to the present Regulation, an additional report shall be
made on the specific period of operation, the venue and the type of sewer grid and the construction
material used, as well as on all existing data regarding the operational capability of the grid in
emergencies and/or flooding of adjacent territories and the effect thereof to the environment.
Part Two
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DESIGN REQUIREMENTS FOR GRAVITY SEWERS AND SEWAGE COLLECTORS
Chapter І
General Terms
Article 12. (1) Gravity sewer grids shall be designed as branch- or ring collectors.
(2) Ring gravity sewer grids shall be designed when the design assignment requires enhanced
reliability of waste waters discharge through real-time redistribution of rainfall waste waters. This also
goes for the design of real-time redistribution system of water flows.
Article 13. In designing gravity sewer grids the following shall be taken into consideration:
1. terrain topography and spatial layout of the fairways and watersheds in natural water basins;
2. layout, width, development and vertical planning of the streets and street grid;
3. building techniques used in regulated land property plots, foundations depth of the buildings
and presence of underground spaces;
4. presence, type and hydraulic conductivity of the existing sewer grids;
5. presence, level and composition of underground waters;
6. availability of suitable water basins and their hydraulic parameters;
7. geological conditions and technical properties of the construction soils, presence of landslide
zones and loess soils;
8. layout of the existing underground pipelines, communication facilities and equipment, as well
as of those currently under design.
9. requirements to the sewer grid and its related equipment pursuant to the conditions in the
waste water discharge licence;
10. conditions for mechanical digging of pipeline trenches, and for laying and covering of the
pipelines.
Article 14. (1) When sewage pipes are laid in a trench, the latter’s width shall be determined
depending on the diameter and the depth of the pipelines in compliance with Appendix 7, so as to provide
for strengthening of the reverse bank between the pipe external ends and the slope face.
(2) The minimum width at the bottom of trapezoidal open sewers, as well as the width of
rectangular open sewers shall be 0.3 m.
Article 15. If necessary, protection sewers shall be designed parallel to the sewer grids, to prevent
the influx of external surface waters into the sewer grid.
Chapter II
Hydraulic size references for gravity sewer grids
Article 16. (1). The average 24-hr volume of household waste waters from urban territories
(including public buildings) shall be determined on the basis of the maximum number of inhabitants for
an economically justified period of operation. The average 24-hr drainage level shall be fixed at
90 per cent of the average 24-hr consumption of drinking and household water, including that from public
buildings.
(2) The maximum hourly volume of household waste waters from urban territories shall be
determined by multiplying the average 24-hr volume of household waste water by the maximum
coefficient of general unevenness (Ко,max), according to the following formula
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Ko,ìàêñ  1 
2.5
Qñð.äåí
0.22
,
(1),
where Q average/day is the average 24-hr water volume of household waste waters from urban
territories, l/s. The maximum value of Ко,max is 3.5.
(3) The minimum hourly volume of household waste water from urban territories shall be
determined by multiplying the average 24-hr water volume of the household waste water by the minimum
coefficient of general unevenness (Ко,min), identified according to the formula:
Ko,ìèí  0.25Qñð.äåí
0,1
(2),
where Q average/day is the average 24-hr water volume of the household waste water l/s
(4) The reference volumes of industrial waste water shall be determined on the basis of:
1. direct readings;
2. estimated water supply for production needs;
3. data from analogous industries;
4. (at the discretion of the designing engineer): data on the production type and technologies,
staff numbers and debit volumes according to the production technological data;
5. data on the used water volumes from own water sources;
6. data on the future development of the plants.
Article 17. (1) The volume of underground water entering the sewer grid shall be determined
through direct readings.
(2) In case of absence of specific data, the general volume of the infiltrated underground and other
types of water shall be considered to be within the range of 0.05–0.15 l/s. ha in the case of impermeable
drained areas. This can be calculated by multiplying the total drained area by the average drain
coefficient.
(3). Infiltration can be considered zero if the hydrologic studies show that the sewer grid is
planned to be installed above the level of underground water.
Article 18. The reference rainfall values in the hydraulic sizing of sewer grids shall be determined
according to Appendix 2.
Article 19. (1) The reference household water volume in separating sewer grids shall be
determined as a total of the maximum hourly output of household and industrial waste waters multiplied
by 2.
(2). The reference water volume in separating rainwater sewer grids shall be determined according
to Article 18.
(3) The reference water volume for mixed type sewer grids shall be defined as the sum total of the
maximum hourly volume of household and industrial waste water and the reference rainfall volume as
identified in Article 18.
Article 20. (1) The hydraulic reference size of the sewerage shall be decided according to the
technical specification data of the designed pipeline, using the well-established practical hydraulic
formulae of Colebrook and/or Manning.
(2) The waste water conduits shall be hydraulically sized in a way as to limit to an utmost degree
suspended substance deposits at the bottom, as well as to guarantee longitudinal movement of the already
deposed sediments (i.e. to provide conditions for a self-cleansing speed of the waste water in the
conduits).
(3) The admissible min and max waste water speed while sizing gravity sewers shall be compliant
with Appendix 8.
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Article 21. (1). In designing gravity sewer grids the minimum internal diameter of the pipes shall
be 250 mm.
(2). The minimal diameter of inbuilt sewage branches shall be accepted in compliance with the
requirements of Regulation 4/2005 for the design, construction and operation of inbuilt water- and waste
water pipelines (revised in OG No 53/2005).
(3) A minimal internal diameter of 200 mm shall be admissible in pipeline gradients bigger than
0.01 when the diameter used matches the sizable waste water volume.
Article 22. The hydraulic sizing of the gravity sewer grids shall be done in the absence of water
pressure, with waste water being sized in water levels coinciding with the pipe head in the sized section,
i.e. complete filling.
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Chapter ІІІ
Inspection Manholes in Gravity Sewer Grids
Article 23. (1) In designing sewer grid manholes for inspection by the staff, access shall be
provided for maintenance work. The smallest internal size of the manhole main body shall be as follows:
1. 1 000 mm for ring/chamber manholes;
2. 750 х 1 200 mm for rectangular section manholes;
3. 900 х 1 100 mm for ellipse section manholes.
(2) The smallest diameter of the entrance level of the manholes shall be designed with a 600 mm
internal diameter
(3) The size of the lower part of the manhole providing access for inspection by the staff shall be
designed so as to allow for an easy and quick cleaning, washing and mounting of closure devices and
measuring gauges (if needed), as well as for other work that might be needed during the period of
operation.
(4) In sewer grids belonging to a specific land property (in situ grids) it may be possible to design
inspection manholes without access by operating staff. The nominal diameter of the inspection manhole
in this case shall have an internal size of 400 to 800 mm.
Article 24. (1) Inspection manholes providing access to inspection staff shall be designed for sites
where plans are on-going for horizontal or vertical corrections in the pipeline/sewage path, and in view of
planned changes in the cross-section/slope of the adjacent branching pipes, as well as in areas of a single
sewage, or sewage pipe junction.
(2) The maximum distance between two adjacent inspection manholes, depending on the internal
diameter of the sewer branch, shall be as follows:
1. 200–450 mm – up to 60 m;
2. 500–600 mm – up to 80 m;
3. 700–900 mm – up to 100 m;
4. 1 000–1 500 mm – up to 150 m;
5. more than 1 500 mm – up to 200 m.
(3) Except in cases of a pressure gush in a secondary branch, no switch-on of a sewage branch
running against the receiving branch shall be allowed into the latter.
(4) Linking of sewage units of different diameter in the direction of waste water movement shall
be designed so as to achieve identical top elevations of the sewage profiles in the inspection manhole, or
to make the water elevations identical in both sewage profiles of reference water volumes.
(5) In steep terrains where there is a rise in the collector slope, and depending on the hydraulic
calculations, a reduction in the pipe profile size shall be allowed, by a “bottom-to-bottom” design of the
pipe junctions.
(6) Connection of built-in sewages to street sewer grids without inspection manholes shall be
allowed if the deviation length is less than 20 m. Connection in the absence of inspection manholes
should not result in changes in the light sections of the sewage, or in operational hitches.
Article 25. (1) The inspection manholes shall be tested for resistance against influx of high
underground water (if any).
(2) The inspection manholes shall be resistant to external loads such as soil pressure, vehicles, etc.
(3) The pipe-to-manhole junctions should be watertight.
Article 26. (1) Under-street-level inspection manholes shall have tops on street level and shall
meet the following requirements:
1. to be adequate to the street load category;
2. to guarantee road safety and to offset vandalism;
4. to prevent fall-through;
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(2). Inspection manholes in household sewages shall be designed with vent openings.
(3) When inspection manholes are planned in green zones, their openings, including tops shall be
designed at a distance of 0.20 m above elevation. In arable land regions, the distance shall be 0.80 m
above elevation.
(4). Ladder steps in inspection manholes shall be corrosion-resistant.
(5) The inspection manhole cunettes shall be designed so as to create the best hydraulic conditions
for waste water movement and for safe operation.
Chapter ІV
Rain Gullies in Gravity Sewer Grids
Article 27. Rain gullies shall be designed in consideration of their location (rain manholes) or as
linear facilities.
Article 28. (1) Rain gullies shall be planned at the following locations:
1.along the streets, taking into consideration the lowest points defined by the vertical street-and
square planning, as well as the pedestrian zones, subways and public transport stops;
2. at the street crossings, so as to guarantee water drainage before the zebra crossings and at the
lowest points defined by the vertical crossings.
3. across the streets at slopes higher than 8 per cent, with the grids being secured against
accidental opening, or forming a monolithic integral part of the gully;
(2) Rain gullies shall be designed to have a lid and a sediment section.
(3) The lid shall be designed in view of the street load category and shall guarantee safety and
resistance to vandalism.
(4) In first grade street grid, rain gullies shall be guaranteed against fall-through and accidental
opening of the lid;
(5) Rain gullies will be sized on the basis of the sizeable rain volumes they can hold, and of their
maximum hydraulic conductivity;
(6) Rain manholes shall be connected to the rain water-, or mixed waste water sewer grids,
through a pipeline of a smallest internal diameter of 150 mm and a length up to 40 m.
Chapter V
Sloping Manholes in Gravity Sewer Grids
Article 29. (1) Sloping manholes shall be designed to:
1. prevent increase of the maximum admissible speed in the pipelines in sloping terrains;
2. guarantee safe transition of the pipelines under the existing underground grids and equipment
of the technical infrastructure or other obstacles;
3. guarantee a submerged drainage of water from the sewage profiles, collectors or rain drain
pipes into the gullies.
(2) In pipelines with a nominal diameter DN ≤ 600 mm and a slope height up to 0.50 m, design of
inspection manholes with suitable cunette shapes shall be allowed, to guarantee a smooth passage;
Article 30. (1) At a 3 m slope height and pipes of more than 500 mm diameter, the sloping
manholes shall be designed as “practical profile” spillways.
(2) At up to 6 m slope height and pipes of up to 500 mm diameter, the manholes shall be designed
with two junctions of the conveying pipe, namely:
1. along the slope of the conveying pipe with a diameter equal to the diameter of the latter;
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2. with a 250 mm vertical pipe outside the manhole into a concrete block, and a bottom water
discharge hole with a guiding arm.
(3) In slope height exceeding 6 m, cascade manholes, speed flow canals and similar energy
annihilation equipment shall be designed.
Chapter VI
Rainwater Spillways
Article 31. (1) Rainwater spillways (rainwater spillway manholes) shall be planned in the case of
mixed-type sewer grids in order to reduce their hydraulic load in cases when the water volumes are bigger
than the reference volumes, and in registering the accepted dilution degree.
(2) The number and location of rainwater spillways shall be determined on the basis of technical
and economic analyses and of comparisons of variants using a different number of rainwater spillways
and depending on the terrain characteristic, the gully location and the standard requirements to the latter,
with the aim of reducing pollution in water basins.
Article 32. (1) The elevation of the spill over rim in rainwater spillways shall be designed to be
higher than the water elevation in surface water sites (water basins) at a guaranteed maximal average
annual water volume of 1 %. When justified, a lower value can be accepted.
(2) In cases of discharge of inflow sewage conduit into an open water basin, measures shall be
planned to offset the danger of destruction of the water basin bottom and bank.
Article 33. (1) The hydraulic sizing of rainwater spillways shall be done taking into consideration
the hydraulic and structural characteristics of the spillway, as well as the type and parameters of the
uneven flow movement in the unit and the adjacent pipeline sections.
(2) In the hydraulic sizing of rainwater spillways, consideration shall be taken also of the
overflowing water volume, the filling heights in the incoming and conveying section of the sewage
matching the steady water volume, and the related sizeable water volumes, as well as the hydraulic and
structural characteristics of the spillway.
(3) The steady water volume during rain shall be determined depending on the maximum hourly
water volume in dry weather, and the degree of its dilution by rain water (n о being the ratio of rain waste
water and the maximum hourly volume in dry weather in the steady part of the mixed flow). The volume
of steady water during rainfall shall be determined according to the formula:
Q steady. = (1+ nо ) Q max.h.
(4) The dilution degree shall be determined by the quantity and quality of the waste water and the
spillway itself. In the absence of other stricter requirements, the following values shall be valid for the
dilution degree:
1. at least 5 for rainfall spillways inside an inhabited place;
2. 1 or 2 for rainfall spillways in front of pump stations;
3. 1 for rainfall spillways beyond urban territories or in front of water treatment plants.
(5) River bed correction projects on urban territories, and investment projects for rainfall spillway
sewer grids shall be interdependent and coordinated in a way that shall allow minimum length of the
rainfall spillways conduits, and waste water discharge after the threshold of the corrected river bed.
Chapter VII
Inverted Siphons in Gravity Sewer Grids
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Article 34. (1) Inverted siphons shall be designed in case of a need to lay pipelines with gravity
water movement though a pressure area of natural or man-made obstacles such as rivers, ravines, canals,
already existing pipelines or other equipment.
(2) The inverted siphons shall be designed to have at least two operational pipelines. When
passing under dry ravines and other similar obstacles, a single pipeline may be designed, with the
necessary provisions for its regular washing.
(3) In mixed sewages rainfall spillways shall be installed, wherever possible, in front of the
inverted siphons so that the spillway canal shall discharge the waste water in the direction of the water
basin flow.
Article 35. (1) In mixed sewer grids one of the inverted siphon pipes shall be sized for a
maximum hourly water volume in dry weather while the other shall be sized for the difference between a
standard water volume and the water volume passing through the first water pipe when it rains.
(2) In separating household and/or industrial water sewer grids, each water pipe of the inverted
siphon shall be sized for half of the sizeable water volume, with its hydraulic conductivity controlled for
its capacity to conduct the total water volume in case of damage of the second water pipe. When the
hydraulic sizing confirms that in both inverted siphon water pipes the speed is less than the admissible
minimum, one of the pipes shall be set aside as an emergency water pipe.
(3) In the hydraulic sizing of the inverted siphon water pipes, the target speed shall prevent the
formation of sediments and/or blockages, as well as substantial pressure losses, provided that waste water
speed in the inverted siphon is bigger than the speed in the preceding section of the inverted siphon.
(4) The waste water speed in the inverted siphons shall be acceptable if it remains in the 1.2–
1.5 m/s range.
(5) The inverted siphon pipes shall be designed with a nominal diameter not smaller than 200 mm,
while the maximum slope of their conveying section shall be 20 degrees compared to the horizon.
(6) Displacement of water levels in the entrance and exit manhole shall be determined on the
basis of the total longitudinal loss, and local obstacles (entrances, bends, exits, etc.).
Article 36. (1) When the inverted siphons pass under rivers, ravines, canals, etc., pipeline covers
of at least 0.50 m shall be designed. When passing under quick flow river or rainfall ravine, covers shall
be at least 1 m., and protection shall be planned for the inverted siphon against water erosion in the
direction of the river flow immediately following the pipeline.
(2) In mixed-type sewer grids, a spillway shall be designed at the inverted siphon entrance
manhole, to separate water volumes when it rains.
(3) An emergency shaft shall be designed at the entrance of the inverted siphon to provide for a
direct waste water discharge into the surface water basin.
(4) Closing devices shall be designed at the inverted siphon entrance, to provide for the on/off
switching of the operational pipelines.
(5) When the inverted siphons pass under rivers, entrance and exit shafts need to be built in the
influx part of the river. The entrance openings shall be designed at an elevation higher than the river water
level, in compliance with the requirement for a guaranteed 1 per cent water volume. When proper
justification is available, the guaranteed value could be lower.
(6) The inverted siphon manholes shall be designed so as to guarantee adequate access to the
closing devices for their manipulation, and for cleansing and washing of the pipes.
(7) Operation sites shall be designed in inverted siphon manholes with an elevation higher than
the maximum water level in the manhole.
(8) A grid to catch floating matter shall be included in the design of the inverted siphon entrance.
Chapter VIІІ
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Retention tanks in Gravity Sewer Grids
Article 37. Retention tanks shall be designed in cases of separating sewer grids for waste rain
water and in cases of mixed type sewer grids when there is a technically justified need to:
1. reduce the hydraulic load of the sewage collector after a certain point through retaining part of
the water volume in a cistern during rainfall and its continuous discharge, for a period not longer than
24 hrs., into the grid after the rain has stopped;
2. retain part of the suspended substances in the waste water discharged from the sewer grid into
the water basin, in order to comply with the requirements regarding water basins;
3. unload overloaded collectors or switch on new ones in cases of expansion of urban territories;
4. reduce the influx before the water treatment plants when it rains;
5. protect the adjacent territories from flooding using the results from analyses and studies on the
effects and consequences of floods on people and their property.
Article 38. (1) Retention tanks shall be designed as open or closed depending on the type of sewer
grid, sanitary-hygienic requirements, terrain, detailed territorial development plans for urban territories,
qualities of waste water, etc. Ventilation shall be planned for the closed retention tanks.
(2) In locating plots for compulsory retention tanks, the design shall take into consideration the
terrain slope and the danger from sedimentation in the sewer segments preceding the retention tanks, as
well as the danger from flooding of the lowest premises of the buildings as a result from underground
blockage.
(3) In designing retention tanks, measures shall be planned to guarantee access to and cleaning
and/or washing of, the sediments.
(4) Emergency spillways shall also be designed as part of the retention tank.
Article 39. (1) In determining retention tanks volumes, the following factors shall be considered:
1. shape and size of the standard sizing retention tank hydrograph, i.e. the hydrograph
guaranteeing the retention tank volume;
2. the highest point (peak, water volume) of the standard sizing retention tank
hydrograph;
3. volume of the flow from the retention tank to the sewer grid located immediately after it.
(2) The working load of the retention tanks shall be determined in accordance with Appendix 9
Article 40. (1) To reduce the hydraulic load of the sewage systems, and to balance the waste water
flow into the waste water treatment plants, an analysis shall be made of the possibility of retaining and
conveying non-polluted surface rain water into infiltration drainage systems next to the zone of their
accumulation, or their direct discharge into surface water basins.
(2) No connection of waste water other than the draining of non-polluted rain water from adjacent
surface covers shall be allowed onto the systems under paragraph 1.
(3) In the design of infiltration systems, the following requirements shall be observed:
1. a study shall be made on the underground water level, in order to guarantee a controlled release
of accumulated rain water without a direct link with the underground water;
2. the retained volumes shall depend on the hydraulic properties of the soil, the size of the drained
plot, the rain intensity and the terrain topography;
3. Access for maintenance of the system shall be guaranteed.
(4) To maintain the admissible values of polluting substances as regulated by the relevant control
bodies, waste water from parking lots shall be discharged into infiltration drainage systems only after
additional treatment by oil products/ heavy metal separators.
Chapter ІX
Gravity Sewer Grids under Roads and Railway Lines
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Article 41. (1) Sewer grid sections passing under roads and railway lines shall be made of pipes
laid in protective pipelines or mounting shafts.
(2) Sewer grid sections may pass under roads and railway lines without protective pipeline or
mounting shafts if measures have been taken to prevent damages to the road or railway line by the water
flow in case of an accident, and if the sewer pipelines are guaranteed against destruction by static and
dynamic loads.
(3) Sewer pipeline paths shall be designed so as to cross the road or railway lines in a direct line
and if possible under an angle of approximately 90 degrees.
(4) The internal diameter of the protective pipelines of any sewage collector under a road or a
railway line shall be designed to be bigger than the external diameter of the sewer pipelines, by at least
200 mm. The external diameter of exposed protective pipelines shall be designed depending on the
technology used in the construction, and the diameter and type of the sewage pipes.
(5) Inspection manholes shall be designed at both ends of the sewer grid sections built under
roads or railway lines, to allow shutting of those sections during operation.
Article 42. Sewage pipelines shall pass over roads or railway lines via scaffold- and canal bridges,
or using already existing bridges and pedestrian crossings, with consideration of all needed anti-freezing
measures, as well as of access for operating, cleaning, washing and insulation of the pipeline, and for
maintenance and operation of the engineering equipment.
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Chapter X
Pump Stations at Gravity Sewer Grids
Article 43. (1) Sewage pump stations shall be designed when it is necessary to:
1.
avoid excessive depths in laying the canals;
2.
pump out waste water from low-lying areas;
3.
cross heights, water currents, roads, railway lines, etc.,
4.
pump out water from retention tanks;
5.
pump waste water into water treatment plants, water basins, etc.
(2) The design of sewage pump plants shall take into consideration:
1.
the total expenditure;
2.
the electric energy expenses;
3.
the requirements for their maintenance and operation;
4.
the risks from, and consequences of operational disruptions;
5.
the effects on the environment;
6.
the standard regulation requirements for a guaranteed safety of the work of the staff
(prevention of job accidents, adequate lighting, reduction in noise and vibrations, etc.);
7.
the sanitary and hygienic requirements (supply of drinking water, easy to clean surfaces,
etc.);
8.
the standard regulation requirements for fire safety.
Article 44. (1) In determining the location of the sewage pump stations, the following shall be
taken into consideration:
1.
the topographic features of the terrain;
2.
the electricity source and the need of building transformer stations;
3.
the geological and hydrological conditions;
4.
access facilities for the vehicles;
5.
flood danger.
(2) The location of the sewage pump stations shall be determined in view of a possible expansion
of the pump stations and the need for suitable access by operating staff and transport vehicles in all
weather conditions. It also has to allow for the building of retention tanks, grids, sand protecting lids, etc.,
if and when necessary.
(3) If possible, the locations of the sewage pump plants shall be determined in view of the nearest
water basin.
(4) To avoid blockages in pipelines, grids or crushers shall be mounted before waste water is
discharged into the draw tank.
(5) If possible, emergency sewage pipelines shall be mounted in front of the sewage pump
stations, to convey waste water to the nearest water basin in cases of accidents or electricity cuts.
Article 45. (1) In the design of draw tanks in the sewage pump stations, measures shall be planned
to avoid waste water decay and accumulation of toxic and explosive gas mixtures, and to counteract the
possible danger for the operating staff through warning systems, ventilation, etc.
(2) The functional requirements for the design of draw tanks in sewage pump stations are as
follows:
1. the maximum water level in the draw tank shall be lower than the bottom elevation of the
incoming pipeline or canal;
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2. the entrances of the suction pipelines shall be located and shaped so as to avoid air suction;
they shall be at a safe distance from the entrance;
3. easy and safe access shall be guaranteed for cleaning and repairs, and contact with other pump
station sections shall be avoided.
(3). The draw tank volume of the sewage pump stations shall be determined depending on the
volume of incoming and pumped out waste water for a period of 24 hrs. at the maximum hourly volume
of the incoming waste water. When there is no drain chart, the minimum volume of the draw tank may be
determined on the basis of a five-minute-output of the highest capacity pump.
(4). Washing pipeline systems shall be designed for the cleaning of draw tanks.
(5). In draw tanks with submerged pump plants, elevating transporters shall be designed to
submerge and draw out pump plants of over 50 kg.
(6) To supervise and clean draw tanks, permanent levers shall be maintained to guarantee safe
descend and ascend.
(7) In fixed steps or ladders longer than 10 m, rest landings shall be erected at every 6 m. The step
width shall be at least 0.65 m in vertical, and 1.10 m in declining ladders.
Article 46. (1) Pump types shall be chosen depending on the waste water sizing volume, physical
and chemical composition and re-pumping height (i.e. total pressure necessary).
(2) The smallest number of spare plants for simultaneously operating pump plants shall be
determined as follows:
1. one spare plant for up to two operating plants;
2. two spare plants for three or more operating plants.
Article 47. (1) The centrifugal and pressure pipeline diameters shall be determined depending on:
1.
waste water sizing volumes;
2.
speeds at minimum total expenditure;
3.
prevention of waste water decay in cases of longer periods of retention in the pipelines;
4.
Blockage prevention.
(2) The pipe type shall be adequate to the required pressure, resp. vacuum, the physico-chemical
composition of the waste water and the properties of the soil.
(3) The pipelines shall be designed to be watertight and resist external and internal loads.
(4) Centrifugal pipelines shall be designed with a minimum length so as to prevent air cushion
formation.
Article 48. (1) Pressure pipelines outside pump stations shall be designed with consideration of
the following:
1. when above ground, they shall be fortified by supporting blocks, clamps and stretchers, and
shall be thermo-insulated.
2. access for operation and maintenance in all types of weather shall be guaranteed.
(2) When defining the pressure pipelines path outside pump stations, rough ground shall be
avoided.
Article 49. (1) The size of premises or manholes where pump plants are to be installed, will be
determined in consideration of:
1. the number, type and size of pump plants;
2. the need to provide for adequately large space around the pump plants, pipelines, structures,
etc., to guarantee easy and adequate supervision, overhaul or replacement.
(2) In the “dry” installation sites the pump plants shall be installed on an elevation which shall
guarantee their natural inundation.
(3) To facilitate mounting and dismounting of pump plants, all structural, facial, etc. sections shall
be transported by elevators.
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Article 50. (1) A heating installation shall be designed in the operational premises of the sewage
pump stations, to guarantee the needed air temperature in winter. Ventilation shall also be installed, to
guarantee the needed air circulation in compliance with the requirements of Regulation No 15/2005 for
technical rules and standards in designing, construction and operation of production plants and
equipment, in carrying and distribution of heating energy (revised, OG No 68/2005).
(2) In premises where toxic and/or explosive gas mixtures are possible, an emergency installation
shall be designed to secure ventilation periods in explosive zones and/or according to the degree of
toxicity of the released gas mixtures. An emergency gas signal device shall be installed, with gas
transducers to trigger off the emergency ventilation system and alert the staff on duty.
(3) To control odours in the pump station, measures shall be taken to stall off decay processes.
Article 51. (1) The following structures shall be designed in addition to the centrifuge pipelines:
1. reverse valves, at the mouth of the pipelines when pump inundation is done through deliberate
water filling of their body;
2. suspension valves, in front of the pumps when their natural inundation from draw tanks has
been secured.
(2) The following structures shall be designed in addition to pressure pipelines:
1. reverse valves after the pumps;
2. suspension valves after the reverse valves;
3. discharge devices at the lower pipeline points to secure the discharge from some of their
sections and to evacuate sediments;
4. adequate vents in the highest points and in points identified by hydraulic shock analysis.
Measures to reduce its effect shall also be identified.
(3) The structures outside the pump stations shall be installed in shafts providing access for the
operation staff and vehicles.
Article 52. In structural sizing of the pump station buildings, the standard construction regulations
apply, providing for:
1. structural stability accounting for possible external and internal loads, elevator and vehicle
loads and seismic loads;
2. watertight properties of the building;
3. resistance of the building in cases of water upsurge;
4. structural stability against waste water and soil pressure.
Article 53. (1) The design of electricity supply and the electric installations shall be in compliance
of the requirements of Regulation No 3 for the installation and use of electric installation and electric
grids (revised, OG No 90 and 91/2004).
(2) Each sewage pump station shall have emergency electric supply installation.
Article 54. (1) Each pump plant shall have its own control panel which will switch on a protective
engine breaker in cases of operational disruptions; it shall also have measuring devices and control
indicators, and shall allow for control of water level, water capacity and water pressure produced by the
pumps, of engine revolutions, electricity pressure and strength, of reactive power factors, gas mixture
concentrations, operational hours of the pump plants, etc.
(2) In cases of a simultaneous operation of two or more pump plants the control system shall
provide for changes in the alternating switching on- and off of the plants.
(3) The control system shall guarantee a serial switching on of the operational and spare pump
plants.
Article 55. The design of sewage pump stations shall involve a simultaneous study of the
possibility of a hydraulic shock and of possible effective means of prevention or reduction of the shock
effect on the pumps, pipelines and structures.
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Section three
DESIGN OF VACCUM SEWER GRIDS
Article 56. (1) Vacuum sewer grids shall be designed to collect and discharge household waste
water under the requirements of the present Regulation and in compliance with BSS EN 1091 on
“Vacuum Sewer Systems outside Buildings”.
(2) Vacuum sewer grids can be designed under the following conditions:
1. on flat terrains;
2. in separating sewer grids for household waste water;
3. in inhabited places with a lower building density and complete street underground and ground
grids and installations;
4. in unfavourable soil conditions such as a high level of underground water, fall-through danger,
rock soil, etc.;
5. in the presence of natural and/or man-made obstacles such as water currents, communication
and service installations, etc.
6. in seasonal facilities such as resorts, etc.
Article 57. In designing vacuum sewer grids, the following functional requirements should be
taken into consideration:
1. prevention of suction valve, and vacuum pipeline blockages;
2. prevention of overflowing or reduction of the overflow occurrences to a pre- calculated
number;
3. reduction in the overload of the built-in collection shafts and the vacuum pipelines down to a
pre-calculated number;
4. prevention of unfavourable effects of the vacuum sewer grids on the surrounding buildings
and equipment;
5. guarantees for the watertight- and airtight properties of the grid;
6. measures to reduce odours;
7. compliance to the standard requirements for fire safety and explosion prevention;
8. compliance with the admissible noise level standards in and outside the buildings;
Article 58. (1) Built-in collection shafts shall be expected:
1. to collect household waste water from the buildings and convey it via suction valves into the
vacuum sections of the vacuum sewer grids;
2. to be watertight;
3. to be designed from construction materials which are resistant to corrosion and suitable to be
in contact with waste water;
4. to have smooth internal surface;
5. to prevent the formation of “dead ends”;
6. to resist internal and external load;
7. to be protected against surface water infiltration.
(2) More than one built-in sewage branch may be gathered in a single built-in
collection shaft.
(3) The collection tank of the built-in collection shafts shall be designed to have a spare volume
amounting to at least 25 per cent of the average 24 hr.- water volume, in case of electric power cuts and
other emergency situations.
(4) In designing collection tanks for built-in collection shafts, their ventilation shall be guaranteed,
to prevent vacuum in the built-in sewage installation and water suction by the siphons during the
operation of the street vacuum sewer grid.
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Article 59. (1) The suction valves in the built-in collection shafts shall be designed with a control
panel to open and shut them after the passage of sucked-in waste water, and air from the collection shafts.
(2) When the built-in collection shafts are complete with suction valves, they shall be designed to
open at a minimum vacuum value of 15 kPa and to stay open until the total working water volume of the
collection shafts has been absorbed. With vacuum values dropping under 15 kPa, the suction valves close
automatically.
(3) The vent pipes of the suction valves should not be submerged.
Article 60. (1) The vacuum stations shall be designed as standard pump stations but will
incorporate additionally at least two vacuum devices of identical capacity and a closed vacuum or pump
draw tanks.
(2) Access shall be guaranteed to the internal section of the vacuum or pump draw tanks to allow
for maintenance and cleaning.
(3) In the design of vacuum stations, spare electricity supply installation shall be provided as a
second independent energy source.
Article 61. (1) Depending on the manner and site of their installation, vacuum tanks can be
designed as:
1. horizontal;
2. vertical;
3. in the same building as the vacuum pump and the pressure pump;
4. outside the vacuum station building.
(2) The minimum volume of the vacuum tanks shall be determined in
consideration of the maximum frequency of switching-on of the vacuum pumps and the operational range
of the vacuum.
(3) The pump draw tanks shall be designed for a minimum volume of 0.4 m3 for each mounted
pump.
(4) To create a vacuum, suitable pumps shall be used to comply with the waste water parameters
and the specific hydraulic conditions.
(5) The number, and the productivity of the operating vacuum pumps shall be chosen to secure the
transportation of the maximum sizing volumes of the mixture of waste water and air from the built-in
collection shafts to the vacuum stations.
(6) The vacuum pumps shall be designed for continuous operation and, alternatively, for
switching-on for at least 12 times/hr.
(7) Vacuum plants shall be controlled by switch-on devices installed in the vacuum tanks which
will be activated within the required vacuum values.
Article 62. (1) Waste waters shall be conveyed from the vacuum tanks via:
1. pressure pumps installed outside the tanks, or inside (submerged);
2. hydro-pneumatic system (compressors and pressurized devices).
(2) The waste water from draw tanks shall be conveyed via pressure pumps or
under gravity.
(3) The pressure pumps and pneumatic systems shall be designed of adequate capacity to cover
the entire sewerage, including the waste water treatment plants.
(4) Pressure pumps shall be waste water pumps capable of working in vacuum without cavitation
and of switching on at least 12 times/hr.
(5) When cavitation is to be expected, pipeline junction will be designed between the pressure
flange of the pump and the vacuum tank, to equalize pressure. Alternatively, measures shall be taken to
keep the suction pipeline constantly full of waste water.
(6) In case one vacuum sewer grid covers more than 20 buildings, at least two pressure pumps
shall be designed.
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(7) A stopper shall be designed for each pump plant, to switch it off for routine repairs or
overhaul, without the need of stopping the entire operation process.
Article 63. (1) In case hydro-pneumatic systems are designed to pump waste water out of the
vacuum tanks, their design will guarantee a minimum vacuum of 25 kPa when the system is not
operating.
(2) The time for restoring vacuum shall not exceed 30 min.
Article 64. (1) A system to control the following water levels shall be designed for vacuum and
pump draw tanks:
1. a switch-off level in cases of emergency, stopping the vacuum plant while the pressure pump
continues to operate
2. a switch-on level at which the pressure pump starts operating;
3. a switch-off level at which the pressure pump stops operating;
(2) In the design of vacuum and pump tanks the following alarm devices with remote warning
signals shall also be designed:
1. low vacuum warning: gets into operation when the vacuum in the system drops under the
preliminary selected minimum value;
2. high waste water level warning: gets into operation when the waste water level in the vacuum
or pump draw tanks exceeds its maximum value;
3. emergency warning: gets into operation when a major part of the system is out of operation,
the maximum continuous work period has been exceeded, or there is an electric power cut.
Article 65. (1) The pipelines will be so designed as to resist soil and vehicle load, operational
vacuum and that of tests, as well as periodical loads and water rise load.
(2) The plastic pipes shall be designed to resist a pressure of at least 600 kPa.
Article 66. (1) In their section from their mouth to the suction valves the suction pipelines shall
have a diameter equal or smaller of that of the suction valves.
(2) The minimum diameter of the vacuum pipeline section from the built-in collection shafts to the
street vacuum pipeline (vacuum built-in deviations) shall be DN/ID 50 and not smaller than that of the
suction pipelines next to the suction valves.
(3) Street vacuum pipelines shall be designed to have minimum diameters as follows:
1. DN/ID 65 – when elimination of larger hard substances by vacuum sewages is not permissible;
2. DN/ID 80 – when the above elimination is permissible.
(2) The suction pipeline diameter of the suction valves in the built-in collection tanks shall be
equal to, or smaller than the diameter of the suction valves, as well as than the diameter of the built-in
sewage deviation.
Article 67. (1) The built-in sewage deviations of the vacuum sewer grids shall be designed to
connect the built-in collection shafts to the vacuum station.
(2) The built-in sewage deviations shall be designed with a dropping slope from the suction valve
to the vacuum sewage branches of the sewage.
(3) Waste water discharge from built-in sewage deviations into the vacuum sewage branches shall
be done in the branch upper part next to the cross-section area defined by a central 120о angle
symmetrically orientated with regard to the vertical axis, and under an acute angle with regard to the
horizontal axis of the pipeline.
Article 68. (1) Reverse valves shall be designed for the sewage branches of the vacuum tanks, as
well as for each pressure pump. This will prevent the return of waste water to the tanks.
(2) Stoppers shall be designed for the vacuum sewer grids to isolate some of their sections for
repairs and maintenance.
(3) Stoppers shall be designed for:
1. the vacuum sewer grid, at a maximum distance of 450 m from each other;
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2. the built-in sewage deviations, when their length exceeds 200 m.
(4) The stoppers and reverse valves shall be designed to waste water use and vacuum up to
80 kPa.
Article 69. (1) Vacuum sewage branches shall be designed with a minimum descending slope of
1:500 so as to facilitate to the maximum the self-cleansing movement of waste waters, and to prevent
lasting deposit of sediments.
(2) When it is necessary to design ascending sections up to 10 m long, a level decrease not bigger
than 1.5 m on the pipe heads shall be made at the end and the mouth of the sections, to allow for vacuum
distribution without substantial loss.
(3) The distances between two adjacent ascending sections shall not be shorter than:
1. 1.5 m for the built-in sewage deviations;
2. 6.0 m. for the vacuum branches of the sewage.
(4) The vacuum sewer conduits shall be laid deep under street level depending on the specific
conditions (presence of other underground infrastructure, underground water, shallow rock foundation,
maximum depth at which the soil freezes, the relief alterations alongside the sewage, etc.)
Section Four
DESIGN OF PRESSURE SEWER GRIDS
Article 70. (1) Pressure sewer grids shall be designed to collect and convey household waste
water under the requirements of the present Regulation and in compliance with BSS EN 1671 on
“Pressure Sewer Grids outside Buildings”
(2) Pressure sewer grids shall be used on:
1. flat terrains;
2. separating sewer grids for household waste water;
3. urban territories with a smaller building density and developed street underground- and ground
grids and equipment;
4. unfavourable soil conditions such as a high level of underground water, fall-through danger,
rock soils, etc.;
5. natural and/or man-made obstacles such as water currents, communication or service
installations, etc.
6. seasonal facilities such as resorts, holiday villages, villa areas, etc.;
7. uneven terrains, rough country.
(3) Pressure sewer grids shall:
1. not pose any danger to human health and the environment;
2. shall be designed in consideration for the standard requirements for safety and health in the
working conditions of the staff;
3. shall guarantee normal operation of the grid (without blockages) while complying with the
planned requirements and instructions for construction and operation;
4. shall prevent overflowing of the built-in collection tanks from incoming unpressurized sewer
branches;
5. shall prevent damage to the existing buildings, equipment and other technical infrastructure;
6. shall observe the requirements to sewage systems and related equipment, as identified in the
sewage system discharge licence;
7. shall be watertight;
8. shall not create conditions for odour release;
9. shall guarantee safe access for maintenance and operation of the grid.
(4) The pressure sewer grid shall be designed with branches.
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(5) Automatic switch-on of the emergency power supply in cases of power cuts shall be
envisaged.
(6) Sound and/or optic alarm system shall be designed to warn for operational disruptions.
Article 71. The following elements shall be incorporated in the design of pressure sewer grids:
1. built-in collecting shafts for waste water collection from the built-in installation;
2. pumps to guarantee the needed pressure for conveying waste water;
3. compressed air systems (if needed to clean the grid by compressed air);
4. pressure pipelines.
Article 72. (1) The built-in collection shaft shall be designed to collect, by gravity,
waste water from one or more buildings, depending on the chosen pump capacity.
(2) In the design of built-in collection shafts, the following elements shall be incorporated:
1. adequate ventilation;
2. permanent electricity supply;
3. control devices and a warning system;
4. Level control device in the collection tank, for automatic pump control.
(3) The working volume of the collection shafts, and the estimated waste water volume remaining
after the pump-out operation shall be designed to be at a minimum so that the normal operation regime of
the pumps should not be disrupted.
(4) The emergency volume can be guaranteed in the collection shafts or in the gravity sewage
branches incorporated in them. The emergency volume shall be equal to at least 25 per cent of the average
24 hr. volume of the waste water and determined above the pump switch-on level.
(5) The following equipment shall be mounted on the suction pipelines in the collection shafts:
1. a reverse valve at the pipeline mouth when pump inundation is artificially done;
2. a stopper in front of the pump when inundation is natural.
(6) The collection shaft bottom shall be designed to guarantee sediment
movement toward the suction opening of the pumps.
(7) The collection shafts shall be designed to resist external load, and to be watertight. The
structure and the top shall not allow surface water infiltration.
(8) Collection shafts may be in-built if measures are taken to build, cover and insulate them in a
way to prevent noise, odour and vibration throughout the buildings.
Article 73. (1) Pumps for pressure sewage systems shall be chosen depending on the waste water
parameters and specific hydraulic conditions.
(2) The pumps shall be mounted in the collection shafts and outside them depending on whether
they work separately or in parallel. To protect pump plants, grids or breakers (cutting devices) shall be
provided.
(3) To guarantee continuous operation of the pumps, emergency electricity supply from a second
independent energy source shall be provided.
(4) The following devices shall be mounted in pressure pipelines:
1. a reverse valve, after the pump;
2. a stopper, after the valve;
3. discharge devices, at the lowest point, to discharge individual sections of the pipelines;
4. in- and out air valves, or combined air valves shall be mounted in high points or points
identified by testing the pipelines against hydraulic shock.
(5) In designing pump plants, the requirements of Part Two, Chapter X shall be in force.
Article 74. (1) Fixed and removable compressor plants can be installed at the mouth of the
pressure pipelines, to guarantee waste water movement.
(2) Compressed air plants shall be installed in underground or ground premises. When they are
designed as ground equipment, measures shall be taken for the reduction of noise, for the heat insulation
of the plant, and to provide thermal and ventilation installations to guarantee normal air temperature.
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(3) In the design process, instructions for the installation, tests, control and operation of the
compressed air plants shall be formulated.
Article 75. (1) Pressure pipelines shall be designed with a slope equal or approximately equal, to
the terrain slope.
(2) Airlets shall be designed in the high points, suitable to use in waste water.
(3) The pressure pipelines shall be made of corrosion-resistant construction material designed to
use waste water, and resist internal hydrostatic pressure of at least 600 kPa.
(4) Washing tubes shall be installed at the start of each sewage section. Care shall be taken to
avoid contact points with the water supply system.
(5) In danger of freezing of any sewage section, heat insulation shall be provided. Alternatively, it
shall be laid in an insulated shaft.
(6) Pressure sewage conduits shall be laid deep under the street depending on the specific
conditions (presence of another underground infrastructure, underground water, shallow rock foundation
and on the maximum soil freezing depth, relief changes alongside the sewage, etc.)
Article 76. (1) Hydraulic sizing of the pressure pipelines shall be done on the basis of the
identified volume of pumped out waste water depending on the capacity and frequency of switching-on of
each pump, the number of simultaneously operating pumps and the waste water influx to each of the
collection shafts.
(2) The minimum waste water speed in sizing of the pressure pipelines shall be 0.7 m/s. When
pump operation cannot guarantee this minimum, a system for periodical washing of the pipelines shall be
planned.
(3) The internal diameter of the pressure pipelines shall be estimated to be equal or bigger than
the internal diameter of the pressure flange of the pumps. No reduction shall be allowed of the diameter
along the pipeline length.
(4) The time that the waste water stays in the pressure sewage systems shall not exceed 8 hrs. to
prevent sewage gas release. When this cannot be guaranteed, suitable measures shall be taken to prevent
odour release.
Chapter Five
CONTROL, MANAGEMENT AND AUTOMATION OF SEWER GRIDS
Article 77. (1) The systems for control, management and automation of sewer grids shall be
designed to match the periods of their maintenance and operation.
(2) The type and technological level of the systems for control, management and automation shall
be analysed and assessed at the initial stage of sewer grid design.
(3) The systems for control, management and automation shall incorporate, when possible,
management of both sewer grids and waste water treatment plants.
Article 78. (1) In gravity sewer grids, control, management and automation will cover the work
of:
1. pump stations;
2. control structures, spillways and measuring devices;
3. retention tank tanks and other separating tanks;
4. rain spillways in front of pump stations and waste water treatment plants;
5. inverted siphons, etc.
(2) In vacuum sewer grids, control, management and automation shall incorporate the operation
of:
1. controls opening the section valves at the required minimum vacuum;
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2. water level transducers in the collection tanks, linked to the suction valves;
3. closing devices which switch off sections of the vacuum pipelines;
4. vacuum breakers controlling the vacuum devices;
5. water level control devices in the vacuum and pump draw tanks;
6. devices which switch on the spare vacuum pumps, pressure pumps and warning systems;
7. devices for switching onto a different electric supply system;
8. measuring devices.
(3) In pressure sewer grids, control, management and automation include the operation of:
1. water level control transducers in the collection tanks;
2. pump plants management devices;
3. devices for switching onto a different electric supply system;
4. warning systems against disruptions in the operation;
5. measuring devices, etc.
Part three
DESGIN OF WATER TREATMENT PLANTS
Chapter Six
GENERAL CONDITIONS
Article 79. (1) Methods and technological schemes complying with the standard requirements,
modern knowledge and the best practices shall be used in water treatment plants.
(2) The design of waste water treatment plants shall comply with the standard requirements for:
1. protection of water and water basis from pollution, including identified individual emission
restrictions;
2. protection of the environment and implementation of measures needed
to offset harmful effects on the water, air and soil;
3. guaranteed healthy and safe conditions of work for the staff;
4. safe use and treatment of waste products in observance of the standard acts requirements for
control of waste;
5. planning of energy efficiency measures and their implementation in the processes of
construction and operation.
(3) The following factors shall be considered in the design of waste water
treatment plants:
1.
category and demographic characteristics of the inhabited place;
2.
estimations of the current development schemes and the plans for social, economic,
engineering, technological and territorial improvement of urban territories, and of the general plans for
development of water supply and sewage systems and equipment.
3.
technical parameters of the existing water supply and sewage infrastructure;
4.
data on the operating waste water treatment plants and equipment;
5.
morphological, hydrological and hydro-dynamic parameters of the water basin;
6.
climatic and meteorological characteristics of the region;
7.
geological and hydro-geological conditions on the territory of the waste water treatment
plant;
8.
future expansion and changes;
9.
possibilities for joint treatment of industrial and household waste water from inhabited
places;
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10.
possibilities for the reuse of the treated waste water;
11.
possibilities to treat, detoxify and use the sediments;
12.
possibilities for a follow-up use of substances and/or raw materials from waste water or
sediments;
13.
possibilities for optimization of energy expenditure of the plant, also through own
production of electric or heat energy;
14.
possibilities for a simultaneous treatment of waste water and/or sediment treatment from
adjacent urban territories;
15.
measures guaranteeing maintenance and normal operations;
16.
guaranteed general expenditure (investment and operational) efficiency;
17.
specific requirements of the owner and/or the operator of the sewage system;
18.
available data on the differences in the waste water flow by the hour, week or season.
Article 80. The design of waste water treatment plants will comply with the requirements of the
BSS EN 12255 series on “Waste Water Treatment Plants”.
Article 81. (1) The waste water treatment plant capacity and the reference water volumes of the
equipment will be determined in accordance with Appendix 10.
(2) Where there are no real-time data from readings and/or analyses, the load of the treatment
plant may be determined on the basis of EI data according to Appendix 11.
Article 82. (1) The technology of waste water treatment shall be selected depending on:
1. the capacity of the waste water treatment plant;
2. the load and concentration of water pollutants;
3. the requirements for treated waste waters;
4. the follow-up use and/or detoxification of the sediments;
5. the best technological practices.
(2) The technology for treatment of waste waters includes treatment of sediments and sediment
waters, individually and/or directing them back to the main flow.
Article 83. (1) In conspicuous 24 hr. peak loads such as quality and/or volume of the incoming
waste water (in the existence of major industrial enterprises and/or other similar entities) and if justified
beyond doubt, retention tank tanks shall be designed at the plant entrance. The design shall provide for
their gradual discharge, at equal intervals into the treatment equipment for a period of up to 24 hrs., and
during the lesser load periods.
(2) If needed, average values shall be calculated for the composition and/or volume of waste
water, to justify the design of average volume tanks.
(3) In determining the pollutant concentrations at the input of the waste water treatment plants, the
effect of the sediment flows released from sediment treatment technologies shall be taken into
consideration.
Article 84. (1) To guarantee flexible operation in all technological treatment schemes,
simultaneously operating identical equipment/sections of the same technological step shall be planned,
alongside by-pass links allowing for the switching-off of the equipment and/or sections and technological
steps thereof, and of the entire treatment plant. In switching-off of some sections of the equipment, the
overall treatment capacity of the plant shall be preserved.
(2) Treatment plants for under 10 000 EI may have their mechanical processes replaced by
manual ones if technical and economic justification is in place; they may also exclude the possibility of
having simultaneously operating identical equipment from the same technological step.
(3) If necessary, the treatment plant shall include equipment for pre-treatment of additionally
transported waste water and/or sediments external to the system, and adequate measures shall be planned
to analyse their properties.
Article 85. (1) The treated waste water discharge into water basins shall be done through specially
designed equipment which meets:
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1. the hydraulic conditions in the water basin;
2. the standard requirements for the quality of water in the water basin;
3. the need to secure optimal merging of the discharged treated waste water into the target water
basin depending on the fairway of the basin, in order to avoid uneven loads.
(2) In discharging treated water into the sea, standard requirements shall be observed for purity of
beaches, coasts and ports. The location, length and depth of discharge shall be determined on the basis of
the discharge licence, to guarantee optimal merging through recirculation with sea water, and to avoid
uneven loads.
Article 86. In using treatment technologies recommended by the best existing techniques, for
which no sizing methods and/or sizing technological parameters exist, model laboratory and/or pilot
studies shall be undertaken to prove their effect in real conditions.
Article 87. Measuring devices shall be designed for the input and output of the treatment plants.
Chapter seven
EQUIPMENT REQUIREMENTS IN WASTE WATER TREATMENT PLANTS
Part І
Design Requirements for Mechanical Treatment Equipment
Article 88. (1) Mechanical treatment of waste water is used to eliminate large mechanical
admixtures, unsolved substances and suspensions, thereby guaranteeing efficient operation of the rest of
the equipment in the technological scheme.
(2) To eliminate hard, large and floating substances from waste water, grids and sieves shall be
designed.
(3) To eliminate unsolved substances, sand-traps and/or precipitators shall be planned.
(4) Non-precipitating non-solving substances such as fats, oil products and others shall be
eliminated individually, or by combined mechanical treatment equipment.
Article 89. (1) Sand-traps shall be sized for mineral particles as well.
(2) Sand-traps shall have eliminating devices for sand and/or retained fats/oil.
(3) In treatment plants for over 10 000 EI, sand-washing equipment shall be designed to eliminate
organic matter.
Article 90. (1) Organic matter separated by washing and draining of sand, shall be discharged into
the waste water flow for further treatment, while the sand shall be eliminated from the treatment plant
with adequate measures to avoid unfavourable effects on the environment and human health.
(2) Fats and oil retained in the sand-traps shall be collected for a follow-up treatment and use.
Article 91. The need to design primary precipitators and their type shall be determined depending
on the treatment plant capacity, the technological treatment scheme, the volume and composition of the
waste water, the geological and hydrological conditions on the construction site, the techniques to extract
and treat sediments, etc.
Part ІІ
Design Requirements for Biological Treatment Equipment
Article 92. (1) Biological treatment of waste water shall be used to eliminate biologically
degradable organic pollutants in soluble, colloidal and/or fine dispersion state, as well as ammonium
nitrogen and/or phosphates.
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(2) Biological treatment equipment shall be used after the mechanical treatment equipment.
Article 93. (1) To achieve active biological treatment, bio chambers are sized and made to use
biomass in a solid state, in suspension or in a fluid state; alternatively, a combination of all three types can
be used.
(2) The main biological treatment chambers may be complete with equipment to separate the
treated water from the biomass, such as secondary precipitators.
(3) The type and number of bio chambers and secondary precipitators in the technological scheme
of the treatment plant shall be determined depending on the type of pollutants to be eliminated and the
needed degree of treatment.
Article 94. (1) Extensive biological treatment shall be done in conditions approximating natural
conditions, in specially designed biological ponds or wet zones.
(2) The bottom and banks of the biological ponds and wet zones shall be watertight by design.
(3) The biological ponds and wet zones shall be used individually, or in combination with other
biological treatment methods.
Article 95. (1) Depending on their purpose, the biological ponds shall be designed as anaerobic,
optional and aerobic.
(2) To eliminate the suspended substances and to reduce the biological consumption of oxygen
down to 30 per cent, as well as to trigger off biological decay of the accumulated sediments, anaerobic
and optional biological ponds are used.
(3) To reduce the biological consumption of oxygen down to 90–95 per cent and to nitrify the
ammonium nitrate to 90–95 per cent, as well as to execute additional waste water treatment, aerobic
biological ponds are used.
Article 96. (1) For treatment in wet zones, higher water-loving plants such as reeds, willows,
bulrush, etc., shall be used.
(2) Wet zones shall be horizontally, or vertically structured to provide for the run-off of the waste
water.
Part ІІІ
Chemical, and physico-chemical treatment of waste waters
Article 97. (1) Chemical waste water treatment shall be undertaken to eliminate dissolved nonorganic compounds of phosphor, for pH correction, for treated water disinfection, etc.
(2) Physico-chemical waste water treatment in inhabited places shall be undertaken to achieve a
high degree of elimination of suspended substances and colloids.
(3) The type and quantity of the reagents shall be determined in laboratory tests or pilot studies, or
during operation, depending on the waste water characteristics.
Part ІV
Disinfection
Article 98. (1) A technological step for disinfection of treated waste water shall be designed, built
and maintained ready for operation, if one of the following conditions is in place after discharge:
1. the water basin is linked to water supply sources;
2. the water in the water basin is used for agricultural purposes (irrigation, mussel breeding, etc.)
3. the water in the water basin is used for bathing.
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(2) In cases different from those under paragraph 1, a disinfection technological step shall be
designed only if there is a specific requirement for it in the discharge licence.
Part V
Requirements for the design of sediment treatment equipment in waste water treatment
plants
Article 99. Treatment plant sediments shall be used to achieve safe final products that can be
transported, used and/or made safe.
Article 100. (1) The choice of technology to treat sediments shall depend on:
1. the way to guarantee safety of, or use the sediments and to meet the requirements for their
quality;
2. the mass of sediments and their seasonal unevenness;
3. the chemical composition and properties of the sediments;
4. their technical and economic significance;
5. the possibility for simultaneous treatment with other sediments and organic waste;
6. the need to separate and break rough particles that can cause blockage or other operational
problems;
7. the presence of heavy mineral particles, e.g. sand;
8. the possibility of dangerous gas emissions and release, including those producing unpleasant
odours and/or enhancing the greenhouse effect;
9. the possibility to create conditions for corrosion, or abrasion of the building structures;
10. the additional loading of the treatment plants by elements such as nitrogen
and phosphorus, introduced by sediment water released during the sediment treatment processes;
11. the chemical reagents used in the waste water treatment process and their role in the use of
sediments;
12. the measures for the safety and health of the operational staff and the society
in general;
13. the possibilities to produce electric and/or thermal energy by treating
individual sediment types, or sediments in general.
(2) To measure the treated sediment mass and take samples from the supplied and released
sediments and sediment water, suitable equipment shall be used.
Article 101. (1) In the design of sediment treatment equipment, all requirements shall be taken
into consideration, and measures shall be taken to reduce odours, noise, vibration and chances for
explosion.
(2) In small-size waste water treatment plants it shall be necessary to check on the possibility for
additional sediment treatment, such as mechanical drainage, drying and burning. In near vicinity of larger
waste water treatment plants and a technically and economically more advantageous variant shall be
chosen.
Chapter Eight
DESIGN REUIREMENTS FOR PUMP AND COMPRESSOR STATIONS, AND FOR
TECHNOLOGICAL BUILDINS IN THE WASTE WATER TREATMENT PLANTS
Article 102. In designing pump and compression stations, the following general terms shall apply:
1. pump and compressor stations, pumps, compressors, pipelines and structures
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shall be so designed as to display a construction resistant to the chemical and biological effects of waste
water, sediments and gases, as well as the temperature changes;
2. pump and compressor stations shall be designed so that the noise and vibration emissions shall
match the admissible standard requirements;
3. the machine halls of the pump and compressor stations shall be designed with an entrance sized
for access of heavy transport and/or elevating equipment for supply and replacement of the main
technological equipment;
4. before, and after the design of pumps and compressors, the needed dismounting devices,
stoppers, reverse valve and/or other equipment shall also be designed, and adequate distance to facilitate
their maintenance shall also be foreseen;
5. the material, face sections and structures used shall be selected to match the estimated pressure,
temperature and characteristic of transportation.
Article 103. In the design of waste water pump stations in water treatment plants, the main
requirements for the design of pump station in sewer grids shall be valid, in accordance to Chapter Two,
Part X.
Article 104. (1) Sediment pump stations in waste water treatment plants shall be designed if it is
impossible to guarantee a minimum speed of 1.0 m/s at a gravity unpressurized flow.
(2) In choosing sediment pumps, the dry substance concentration and sediment viscosity shall be
taken into account.
(3) In pumping out mixtures of water and sand, or sediments, the minimum acceptable pipeline
diameter shall be at least DN 80.
Article 105. (1) Low-pressure compressors with a high-degree of air circulation (blowers) shall be
designed so as to guarantee adequate air volumes devoid of dust and/or oil for the technological
processes.
(2) In sizing of the technological conduits in the compressor stations, the standards in the design
of heating, ventilation and air conditioning installations shall be observed.
Article 106. For all simultaneously operating pump and compressor plants the following spare
plants shall be planned, especially if required by the employer:
1. one spare plant for up to two operating plants;
2. two spare plants for three or more operating plants.
Article 107. (1) In the technological buildings the needed distances to the walls and from one
plant to another shall be planned, to facilitate mounting, dismounting and access during operation.
(2) Suitable machinery shall be planned to guarantee mounting and dismounting of the plants.
Chapter Nine
WASTE WATER TREATMENT PLANT GENERAL PLAN
Part І
General Terms
Article 108. (1) The choice of location of the waste water treatment plant shall be made
depending on:
1. the possibility to guarantee gravitational movement of the waste water in the
incoming collectors, treatment plants and dispatching collector;
2. the technical and economic requirements as to the length of the incoming and
dispatching sewer collectors;
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3. the ownership and category of the terrain;
4. the speed and prevailing direction of winds, and the location of the adjacent urban territories or
other sites;
5. the requirements of the current development plan;
6. the recommendations from the assessment of the effect on the environment for the smallest
needed distances of the waste water treatment plant from urban territories and other plants; when the
competent authorities have decided that no such assessment is necessary and in the absence of specific
health requirements and standards for protected areas, or related studies and risk assessment, the
minimum protection zones are determined depending on the equipment capacity and in compliance with
Appendix 1;
7. the presence of significant infrastructures (roads and transport grid, water
pipelines, incoming and dispatching sewer collector, etc.) next to the site of the treatment plant;
8. engineering, geological and hydro-geological characteristics of the location;
Article 109. (1) The treatment plant general plan shall contain the location of:
1. the treatment equipment along the technological path of waste water and sediments;
2. the planned buildings on the treatment plant territory (e.g. pump and compressor stations,
administrative buildings, laboratories, transformer points, workshops, storage facilities, garages, etc.),
green territories, etc.;
3. the technical conduits for waste water and sediments;
4. the terrain paths.
(2) The general plan will be structured so as to take into consideration all standard and project
requirements for fire safety, health and work safety and environmental protection.
(3) The general plan shall be structured to allow for:
1. stage-by-stage construction;
2. future expansions and changes of the treatment plant;
3. minimal lengths of sewers and pipelines for waste water, sediments and technical water, air
suction pipes, gas pipelines, electric power grids and roads;
4. convenient and safe access for maintenance and operation of the equipment.
Article 110. An emergency roundabout or pipeline shall be planned for the treatment plant and the
individual equipment.
Part ІІ
In-situ technical infrastructure and buildings in waste water treatment plants
Article 111. Depending on the treatment plant capacity, treatment technology, type of
technological control and local requirements for the major technological equipment and premises,
auxiliary equipment and premises, as well as in-situ technical infrastructure are foreseen.
Article 112. (1) The treatment plants shall be provided with drinking and household water
pipelines, as well as with fire protection water containers.
(2) When use of hydro-elevators and equipment for washing of pipelines and for other technical
needs is planned, technical water pipelines shall also be designed. The use of treated waste water shall be
admissible in case of technical water.
(3) Sanitary premises shall be foreseen depending on the estimated staff number.
(4) To collect household waste water from water treatment plants, a sewer grid shall be designed
to convey it to the station entrance.
(5) For waste water from sediment treatment of spillways, emergency spills emptying or washing
of the equipment, a sewer grid shall be designed to convey it to the entrance of the treatment plant or to
the biological treatment equipment. If necessary, an equalizing tank shall be built.
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(6) To collect and convey rain water from the treatment plant territory, a sewer grid shall be
designed; the pollution degree shall determine the place of its incorporation into the technological
scheme.
Article 113. (1) The slopes of the pipes for waste water, sediments or gas digesters and the speed
of the treated medium shall be so designed, as to prevent deposits of hard substances and/or gas
accumulation, and condensed liquid in the gas and air pipelines; measures shall be foreseen to eliminate
deposits and/or gas or condensate accumulation.
(2) If there is a risk of freezing, tanks and gas pipelines shall have adequate thermal insulation.
(3) The pipelines shall be secured against water and gas penetration.
Article 114. (1) In designing the electric power supply and the electric equipment for waste water
treatment plants, the requirements shall be observed of the current regulations for use of electric power
equipment and grids.
(2) Waste water treatment plants shall be equipped with a second category electric power supply
in compliance with the requirements of Regulation No 3/2004 for use of electric power equipment and
grids.
(3) Emergency electric power supply shall incorporate all measuring and control devices, waste
water pumps and sediments, as well as the air conditioning equipment.
Article 115. (1) In the design of roads on the treatment plant territory, their estimated load during
construction and operation shall be taken into consideration, and measures shall be planned for safety of
movement of vehicles and staff.
(2) To guarantee safe and convenient access to the buildings, equipment, work places and control
points, pedestrian paths shall be foreseen.
(3) When roads and paths are crossed by open canals, suitable crossing points shall be identified.
(4) In cases of reverse movement direction for the vehicles in the process of the technical
operation of the treatment station, suitable spaces shall be identified and enlarged.
Chapter Ten
ODOUR CONTROL
Article 116. (1) The probable release of odours and their effect and treatment shall also be
considered at the design stage of the waste water treatment plants. The main odour releasing sources shall
be divided into groups to apply common measure to offset their effect.
(2) The main odour sources shall be designed at the greatest distance possible from the sensitive
zones around the treatment zones. Account shall be taken of the prevailing direction, and speed of wind.
(3) The choice of adequate protective measures against odour release shall take into consideration
the size of the treatment plant, the distance and size of the adjacent zones (regions), as well as the
prevailing speed, direction and presence of wind.
Article 117. (1) When odour sources are in buildings or covered sites, adequate ventilation shall
be designed for both, complete with odour treatment equipment.
(2) Depending on the emissions released, measures shall be planned for:
1. protection against corrosion;
2. healthy and safe conditions of work for the staff;
3. possible access to the odour source.
(3) Strong smelling emissions shall be suitably treated depending on the specific conditions.
(4) The capacity of odour treatment equipment shall be determined on the basis of the expected
release volume, the input and the required odour concentration.
(5) Easy access shall be provided to the odour treatment equipment to make it possible to measure
the airflow and take air samples for analysis.
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(6) In case of air flows from the treatment plant technological steps of expected contents of
harmful and dangerous components, a system for control, elimination and treatment shall be designed,
and provisions shall be made to have sound and light signals in compliance with the regulations for fireand explosion safety.
Article 118. (1) In the design of ventilation for the production halls and other working premises,
the standard requirements for the design of ventilation and air conditioning shall be observed.
(2) Adequate ventilation in the production halls shall be designed on the basis of the data for the
released polluters and heat release from the equipment. In case of absence of data from test studies on
equipment of analogical effect, the ventilation-air temperature ratio may be determined in accordance
with Appendix 12.
Chapter eleven
CONTROL AND MANAGEMENT OF WASTE WATER TREATMENT PLANTS
Article 119. (1) To control and manage the operation processes, automated dispatch systems shall
be foreseen.
(2) Measuring devices shall be put on suitable places, to measure:
1. volumes of recirculated technological flows;
2. other indexes such as water and sediment level, pressure, temperature, dissolved oxygen
concentration, pH values, etc.
Article 120. (1) The control and management systems shall be designed if a technological
assignment is in place.
(2) The control and management systems shall be built as a subsystem grid operated and
maintained by one or several central stations which control and manage all processes and treatment
equipment.
(3) All control and management systems shall be designed to allow changes in the management
programmes, parameter adjustment and work schedule amendments, and will provide for future
expansion of the plants.
(4) In designing grids from several subsystems, all requirements on data transfer speed, transfer
protocols and plant functions shall be taken into consideration.
(5) In the design of control and management systems, provisions shall be made for control of
aeration systems, biological processes for reduction of the biological consumption of oxygen, nitrification
and de-nitrification processes, phosphor elimination, recirculation flows, sediment treatment, measuring
of chemical treatment reagents, detoxification of waste water, etc., all depending on the selected treatment
technology.
(6) Equipment shall be operated automatically and manually. The needed selection of operational
regimes and remote switching on/off of the equipment shall be taken into consideration. Lights indicating
the state of the equipment (in order/out of order/emergency) shall also be put in place.
Article 121. (1) For measurements and control, a specially designated place and/or laboratory
shall be foreseen.
(2) For treatment plants in inhabited places of over 10 000 EI, and in the remaining cases only if
it is considered necessary, the following facilities shall be foreseen:
1. laboratories for chemical, biological and microbiological analyses;
2. chemical storage halls.
(3) The laboratories shall be designed in accordance with the requirements for operation and
storage of equipment and chemical substances.
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Article 122. The central dispatch point for control and management of technological processes in
the treatment plant shall be located on its territory.
Part Four
CONSTRUCTION, TESTING AND OPERATION OF SEWAGE SYSTEMS
Chapter twelve
GENERAL REQUIREMENTS
Article 123. (1) Sewage systems shall be constructed and brought into operation in accordance
with the construction documents issued, in compliance with the requirements of this order, and also in
accordance with the instructions for the use, installation and manufacturers' testing of the relevant
products, facilities and devices.
(2) Sewage systems shall be constructed in compliance with the requirements of Order No 2 of
2004 for the minimum requirements for healthy and safe working conditions in the performance of
construction and installation work (promulgated, State Gazette, ed. 37, 2004) and the specific
requirements set out in the health and safety plan.
(3) In addition to the requirements of this order, the construction of buildings and facilities for
sewage systems shall also comply with the requirements of the legislative acts which set out the rules for
the implementation of construction and installation work (CIW) and the approval of the relevant types of
construction work.
Article 124. (1) Before the construction of sewage system elements, acceptance tests shall be
carried out upon the construction materials, devices and facilities envisaged in the plan as well as an
inspection of the integrity of the packaging, labelling, surfaces and technical documentation: pursuant to
which the relevant protocols of acceptance shall be issued.
(2) The use of any buildings projects, devices or facilities which do not comply with the
requirements of Article 5, or any such containing technical defects, cracks or deviations from the
admissible values indicated in their technical specifications shall be prohibited.
(3) During the construction of sewage systems only building materials, devices and facilities
whose operational parameters comply with those set out in the approved investment plan shall be used.
Article 125. (1) Ground work required for the construction of sewage systems shall be carried out
in compliance with the Rules for approval of earth works and earth facilities (published in the Bulletin of
Construction and Architecture (BCA), Volume 6, 1988).
(2) In the case of ground work below the level of subterranean waters, the method used to drain
these waters must be established in advance, as well as the method for strengthening and supporting
foundations in the case of weak soils.
(3) Installations, machinery and facilities for the drainage of surface waters and for the purposes of
reducing the level of subterranean waters must function during the entire construction process.
Article 126. (1) The foundations of buildings and facilities in silt (loess) soils when building
sewage systems shall be constructed in accordance with the requirements of Order No 1996, for the
design of flat foundations (promulgated, State Gazette, ed. 85, 1996).
(2) Excavation works shall be stopped when a section of sudden land subsidence is encountered
until the sources of water ingress are removed and the works shall not recommence until the subsidence
has been stabilised.
(3) Subterranean or semi-subterranean facilities for sewage systems, notwithstanding their size
and soil conditions, shall be constructed after prior strengthening of the soil in accordance with the
planned volume mass of the soil skeleton.
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(4) Cementing operations during the construction of facilities in silt zones shall be carried out
without interruption.
(5) After the construction and testing of facilities in ground foundations of type II subsidence, the
gaps formed between the wall of the excavation and the facility shall be filled with layers of loess soil and
shall be fortified up to the planned volume mass of the soil skeleton.
Article 127. (1) The construction of facilities in conditions of high subterranean water levels shall
be carried out after the construction of a drainage system to reduce the level of subterranean waters in
compliance with the design plan.
(2) Immediately before the commencement of construction work, additional assessment must be
carried out, in order to reduce the level of subterranean waters and their drainage from the construction
trench.
(3) After the completion of the water drainage work, all temporary construction drains shall be
removed or plugged.
(4) The construction of pipelines, channels and facilities in subsidence regions shall be carried out
only after the completion of the technical measures set out in the design plan aimed at strengthening the
ground.
Article 128. The facilities and pipelines built in construction trenches shall be covered over only
after the successful completion of the relevant tests for strength and water impermeability; the relevant
acceptance and approval acts and protocols shall be issued in accordance with the relevant legislative
documentation.
Article 129. When constructing the zone around the pipes, the trench bed and for the purposes of
reverse filling, the materials used shall comply with the requirements of the design plans and the
manufacturer as well as the following requirements:
1.
they must possess such strength characteristics that after their sealing the design profile of
the sewage pipeline will not be changed;
2.
must not attract corrosion, damage or breach to the mechanical qualities of the pipes, pipe
covering and those parts with which they are in contact;
3.
they must be impermeable to the effect of chemicals and must not cause harmful reactions
when in contact with the soil or subterranean waters;
4.
must not contain organic materials, frozen soil, large stones, rock fragments or tree roots;
5.
when constructing the area around the pipes materials which freeze at low temperatures
must not be used;
6.
materials which are used for the preparation and construction of the pipe bed must comply
with the requirements of the manufacturer; in the absence of other instructions they must not contain any
particles larger than 25 mm.
Article130. Building materials, facilities and devices used in the construction of sewage systems
shall be transported and stored in accordance with the instructions of their manufacturers.
Article 131. (1) When issuing approvals for completed CIW of sewage system elements, the
necessary certification examinations and testing for their compliance with the construction documents and
CIW regulations shall be carried out, and the necessary acts and protocols arising from Order No 3, 2003,
relating to the issuing of acts and protocols during construction work (promulgated, State Gazette, ed. 72,
2003) shall be complied with.
(2) Technical reports and protocols for the approval and commencement of operation shall be
compiled before each specific element of the sewage system is brought into test operation.
Article 132. The issuing of permits for the operational use of the sewage systems and the
guarantee periods for completed CIW works, as well as permits for facilities and construction work
necessary for the repair of concealed defects after acceptance and commencement of operations, shall
comply with the conditions and procedure of Order No 2 of 2003 for the commencement of operations of
construction works in the Republic of Bulgaria and the minimum guarantee periods for the completed
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construction and installation works, facilities and construction sites (promulgated, State Gazette, ed. 72,
2003).
Article 133. (1) The parameters of the sewage system elements envisaged in the design plan, used
in the construction work and approved upon commencement of operations shall be maintained by means
of technical operations during the process of their normal operation.
(2) The sewage system operator shall appoint persons who shall take responsibility for the
technical operation of individual elements.
(3) During the technical operation of the sewage system, a system of technical servicing and
equipment repair shall be created and the corresponding technical documentation shall be kept.
(4) During the technical operation of the sewage systems, the requirements of Order No 9, 2004,
which guarantee healthy and safe working conditions during the operation and maintenance of water
supply and sewage systems (promulgated, State Gazette, ed. 93, 2004) shall be complied with.
Chapter thirteen
THE CONSTRUCTION OF SEWAGE NETWORKS AND FACILITIES AND SEWAGE
DRAINAGE PIPELINES
Section I
Construction of trenches and sewage pipelines
Article 134. (1) Excavation work for the purposes of laying pipes shall comply with the legislative
requirements for distances from foundations, subterranean facilities and technical conduits and the
necessary measures shall be taken to avoid damage to them.
(2) When determining the size and shaping of the trench for pipe-laying, and the height of the
back-filling the design requirements shall be complied with. All deviations from the design plan shall be
agreed with the designer.
(3) Before the laying of pipes, the depth, angles, width and condition of the bottom of the trench
shall be verified.
(4) The foundation of the trench shall be shaped in such a way as to allow for the unhindered
laying of pipes along its entire length. If necessary, indentations shall be made for the pipe connectors.
(5) During the excavation of the trenches all stones, parts of plants and debris which might
damage the pipes shall be removed from the trench.
Article 135. The width of the trench shall be determined in accordance with the diameter and
pipe-laying depth in accordance with Appendix 7.
Article 136. (1) The stability of the trenches shall be ensured by the use of systems for
strengthening and angling of their walls or other suitable means depending on the specific conditions. The
disassembling the trench strengthening systems must be carried out in such a way as to avoid
displacement or damage to the pipes.
(2) When pipes are laid directly upon the bottom of the trench, it must be levelled, inclined and
shaped to ensure that the pipes remain in contact with the bottom along their entire length.
(3) If the bottom of the trenches cannot be sufficiently levelled, then it shall be covered with a
layer of granular material or fine soil with good sealing qualities. The height of the layer shall be deemed
equivalent to 100 + DI/10 mm (DI is the internal diameter of the pipes in mm) in rocky conditions, but no
more than 25 cm.
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(4) When laying pipes with flanges at the bottom of the trench or in the lower part of the bed,
indentations shall be made for the flanges. The length of the depth of the indentations depends on the
sizes of the pipe connections and the method of their connection.
(5) When the bottom of the trench is unstable or the soil is of low load-bearing capability, the soil
shall be removed and replaced with a suitable material for the trench bed.
Article 137. When carrying out CIW the trenches shall be dried. The method of water drainage
must not affect the zone around the pipes or the pipes themselves.
Article 138. The type and granularity of the material used for the zone around the pipes and for
their support shall be selected in accordance with the design plan requirements and shall take into account
the material of the pipes and the width of the pipes, as well as the soil parameters.
Article 139. (1) The pipes envisaged in the design plan must be connected in accordance with the
manufacturer’s requirements, in such a way as to ensure water impermeability of the pipeline and its
resistance to the working design loads.
(2) In the event that pipe-laying needs to be interrupted for an extended period of time the ends of
the pipes shall be plugged with protective seals.
(3) Connections between pipelines and inspection shafts, inspection apertures or other facilities
shall be constructed in such a way as to be water impermeable.
(4) Should there exist a risk the pipes may float to the surface during installation, the relevant
method of fixation shall be used in accordance with the designer's instructions.
Article 140. The pre-manufactured assembly elements of the sewage network shall be constructed
in compliance with the requirements of the design plan and the manufacturers' requirements.
Article 141. (1) The pipes shall be covered by back-filling with layers of suitable materials: lower
level, upper level, lateral and initial filling or parts of them.
(2) The sealing quality and the level of the covering material for the pipes shall be determined in
compliance with the design plan and shall depend on the location of the pipeline (green area, road surface,
industrial site, etc.).
(3) The minimum thickness of the initial covering shall be 150 mm above the body of the pipes
and 100 mm above the pipe connectors.
(4) The primary covering shall be mechanically sealed when the total height of the covering above
the upper part of the pipes is at least 300 mm — in the case of pipes with a diameter up to DN200
inclusively and 500 mm in the case of pipes with a greater diameter.
(5) The primary and lateral covering may be sealed by means of water saturation only in the case
of non-connected soils.
(6) When support or strengthening is required for individual parts of the pipeline, these activities
shall be carried out before the covering of the zone around the pipes.
(7) The removal of the support structure, when such exists, shall be carried out gradually during
the covering of the zone around the pipes.
(8) Warning tapes shall be placed at a distance of 0.3 m above the sewage conduit as indications
before the final restoration of the upper surface of the excavation, with the exception of gravity sections.
(9) After the completion of back-filling, the ground surface shall be restored in accordance with
the requirements of the design plan.
Section II
Trenchless Construction of sewage pipelines
Article 142. When determining the method for trenchless sewage pipe-laying and unhindered
implementation, the following factors shall be taken into account:
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1. the location of existing subterranean buildings and subterranean networks and technical
infrastructure facilities along the design route of the sewage pipeline to be laid;
2. the technical characteristics of the pipes, including:
a) internal and external diameters;
b) length;
c) permissible operational loads;
d) type and manufacturing characteristics of the pipe connectors;
e) permissible curve radius or angle deviation of the pipeline connectors;
3. the type and parameters of the ground layers through which the pipeline is to be laid; additional
detailed hydro-geological assessments shall be carried out for this purpose;
4 the operational loads and transport vehicle loads;
5. permissible deviations along the pipeline route.
Article 143. Trenchless laying methods for waste water pipelines and pipeline testing shall
comply with Bulgarian standards for the requirements of trenchless pipeline construction.
Article 144. (1) The main and interim shafts for trenchless pipe laying shall be designed and
constructed in such a way as to withstand static and dynamic loads during the laying process.
(2) The location of the main shafts shall take into account the locations of connections with
existing sewage pipelines and/or any change to the direction of the pipeline route.
Article 145. (1) During trenchless pipeline construction, the following data shall be registered and
documented:
1. in the case of micro-tunnel construction — the direction and depth of pipe-laying, the
maximum force used in laying, the speed or length of laying, the quantity of the resources used for
fixation and lubrication, the adjustments made during pipe laying, etc.; and registration of data shall be
carried out at every 0.20 m of the length of the pipe-laying route at the most;
2. in the case of methods requiring service personnel — the maximum force used in laying, the
direction and depth of laying, the speed or the length of laying, the quantity of resources used for fixation
and lubrication, etc.; the registration of data shall be carried out for each pipe;
3. in the case of the direct insertion method — the direction, length and depth of laying, the
quantity and quality of the washing fluids, the maximum force of extrusion, etc.; the registration of data
shall be carried out for each pipe.
(2) When pipe-laying is directed by a laser or other system, it shall be installed in such a way as
not to be affected by tremors which might take place during the pipe laying process.
Article 146. (1) The maximum permissible deviations from the direction and depth of pipe-laying
shall be indicated in the design plan and shall take into account:
1. the requirements for operation and maintenance;
2. pipeline incline;
3. the capabilities of the method used for pipe laying;
4. the presence of existing buildings, facilities and subterranean networks and technical
infrastructure facilities;
5. geological and hydrogeological conditions, etc.
(2) Deviations from the pipeline design route in the case of trenchless pipe-laying shall be noted
during the pipe-laying process. It shall not be permitted to exceed permissible design plan values.
Section III
Construction of vacuum sewage networks
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Article 147. (1) The laying and installation of vacuum pipelines shall be carried out in compliance
with the design requirements and the requirements for the construction of pipelines which are set out in
section I of this chapter.
(2) When the incline of the pipelines is less than 1:150, they must not deviate vertically by more
than +2 mm from the horizontal profile of the design plan.
(3) During the construction process the horizontal profile of the pipelines shall be assessed to be
within the limits of the permissible deviations, in order to ensure the normal functioning of the network in
compliance with the design parameters.
Section IV
Construction of pressurised sewage networks
Article 148. (1) The laying and installation of pressurised pipelines shall be carried out in
compliance with the design requirements and the requirements for the construction of pipelines which are
set out in Section I of this chapter.
(2) During the construction of pressurised pipelines, they shall be strengthened in places where
connections, stopcocks and joints are envisaged.
Article 149. Pumping engines shall be affixed rigidly to the foundations and shall be precisely
centred.
Chapter fourteen
TESTING OF SEWAGE SYSTEMS AND FACILITIES
Article 150. (1) The testing of sewage systems and facilities shall be carried out after the
completion of the CIW and before they are finally covered over.
(2) The initial testing can be carried out before lateral back-filling. The pipeline shall be tested for
final approval after backfilling and the removal of any support structure.
(3) The testing of the sewage systems shall be carried out for each section independently between
two inspection shafts and for each facility in accordance with the design plan requirements and in
compliance with the manufacturer’s instructions.
Article 151. (1) The monitoring and testing of elements from the sewage networks shall include
the following procedures:
1. testing of the density of the foundation and back-filling of the pipelines;
2. visual and instrumental monitoring;
3. inspection by means of a self-propelled television camera;
4. testing for impermeability.
(2) The density level of the backfilling around the pipe and the foundation filling referred to in
paragraph 1(1) shall be tested for their compliance with the design plan requirements using suitable
resources of instruments and methods.
(3) The visual and instrument monitoring referred to in paragraph 1(2) shall include tests for the
following:
1. direction, linearity and incline of the pipe sections;
2. elevation measurement of the bottom of the pipes at the ends of the pipeline sections;
3. typical elevations of facilities along the sewage networks;
4. functional quality of the pipe connectors;
5. damage and deformation to the pipe sections;
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6. connection levels of pipes with different dimensions (diameters);
7. functional quality of insulation, screeding and surface coverings.
(4) Testing of impermeability of the pipelines and facilities referred to in paragraph 1(4) shall be
carried out in accordance with the recommendations of the approved investment project.
(5) The video film acquired during the video filming referred to in paragraph 1(3) shall be deemed
an indivisible part of the documentation related to the approval of the sewage network.
(6) When during testing, the level of the subterranean waters is above the crown of the pipeline,
the need for infiltration testing shall be assessed, depending on the specific conditions.
Article 152. (1) Testing for impermeability of gravity sewage pipelines up to DN 1 000,
inspection shafts and inspection apertures shall be performed with air or water in accordance with the
design plan requirements, pipe manufacturers' instruction and in compliance with Appendices 13 and 14.
(2) In the event of a single or repeated unsuccessful test using air, then it is permitted to test using
water, and the guiding results shall be those of the water tests.
(3) When sewage pipelines are laid within protective pipes, then testing shall be carried out
separately for each sewage pipeline.
(4) Protocols shall be compiled with the results of the tests.
Article 153. (1) The testing of vacuum sewage systems shall include the testing of the induction
valve components (induction valve, valve control and level sensor) in order to establish their functional
suitability in compliance with the requirements of the technical specifications for vacuum sewage systems
and the design plan requirements.
(2) The durability and reliability of induction valve components shall be guaranteed by their
manufacturers in accordance with specified operational conditions and envisaged use.
(3) Prior to vacuum testing, all the sewage branches to buildings and the common vacuum
pipelines must be cleaned and their impermeability from surface water must be guaranteed.
(4) Vacuum tests shall be carried out at every stage of their construction, as well as for the entire
vacuum sewage system after their final construction.
(5) Interim tests shall be carried out after the laying of vacuum pipelines with a length of 450 m at
the most.
(6) When testing has been unsuccessful for a given section, the tested section shall be examined,
the defects shall be removed and the testing shall be repeated, until the values of the vacuum fall within
the values specified.
(7) The final testing of the vacuum sewage system shall be carried out after the construction of all
vacuum pipelines and branch connections to buildings and the vacuum station.
(8) Upon commencement of the operations of the vacuum sewage systems, the additional
functioning of the control system and warning system in the vacuum stations must be verified.
Article 154. (1) The testing and commencement of operation of pressurised sewage systems must
comply with the requirements of the technical specifications setting out the requirements for pressurised
sewage systems and the relevant design requirements.
(2) Prior to testing and commencement of operation, pressurised sewage systems shall be cleaned
and their impermeability from surface waters must be guaranteed.
(3) Pressurised sewage systems shall be tested for water impermeability in compliance with the
requirements for water pipeline testing.
(4) Upon commencement of operations of the pressurised sewage systems, the additional
functioning of the control system and warning system in the vacuum stations must be verified.
Chapter fifteen
TECHNICAL OPERATION OF SEWAGE NETWORKS AND FACILITIES
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Section I
Requirements for technical operation
Article 155. (1) The maintenance and technical operation of sewage networks and facilities shall
include previously planned, on-going and extraordinary (incidental) measures and activities aimed at
maintaining the system in the necessary constructional and functional conditions, as follows:
1. local repairs or replacement of the damaged pipes or elements;
2. removal of sediment, plant roots and other obstructions;
3. repair and maintenance of machines and installation equipment;
4. combating pests (rodents and insects).
(2) The implementation of the measures and activities referred to in paragraph 1 shall be carried
out with the minimum personnel and technical equipment in accordance with the instruction referred to in
Article 198о(7) and (8) of the Law on Waters.
Article 156. During the operation and maintenance of sewage networks and facilities the
following requirements must be implemented:
1. the safe and economically effective operation within the limits of the permissible adverse
effects upon the environment;
2. operation without blockages;
3. restriction of the frequency of hydraulic overloading to values set out in the design plan and in
the instructions for use in compliance with Table 1 in Appendix 2;
4. restriction of the overflow frequency during rainfall within the operational values set out in the
design plan and instructions, as well as the absence of waste water flow in dry weather;
5. safeguarding of the health and life of the general public;
6. provision of healthy and safe working conditions for personnel during maintenance and
operation;
7. safeguarding of the surrounding buildings and facilities from waste water flooding from the
sewage network (water retention);
8. maintenance of the integrity and functionality of the system within the operational period set
out in the design plan;
9. provision and maintenance of water impermeability of the pipelines and facilities;
10. prevention of the formation of odours, aggressive and toxic substances;
11. provision of suitable access to system elements for inspection, maintenance and operation;
12. provision of natural ventilation of the network by means of rain drainage shafts and apertures
on the lids of inspection shafts.
Article 157. During technical operation the necessary monitoring, control or redistribution of
waste waters shall be guaranteed by means of:
1. switching on and off the pumps;
2. other equipment and measures;
3. installation of devices for measuring water volumes.
Article 158. (1) The technical operation and maintenance of the sewage networks and facilities
shall be carried out in accordance with the established document system for technical and repair
servicing.
(2) The effective operation and maintenance of the sewage systems require the following:
1. operation and maintenance plan;
2. sufficient qualified personnel;
3. excellent knowledge of the system;
4. availability of suitable facilities and devices;
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5. complete technical documentation, including subterranean cadastre.
Article 159. (1) The operation and maintenance plan for sewage networks and facilities shall
contain at least:
1.
detailed graphic and digital data about the characteristic features of the urbanised territories
and sewage network;
2.
detailed description of the type of measures used to maintain the planned operational
parameters of the system;
3.
the requirements for the frequency of inspections (monitoring) of the sewage network and
facilities, their type, frequency and technical equipment required for their performance;
4.
planned maintenance activities (on-going and major repairs);
5.
planned activities in the case of breaches or emergencies;
6.
types of operational problems which could occur and the methods and resources used to
resolve them.
7.
allocation of responsibilities for the implementation of the planned measures and sanctions
for non-compliance;
8.
evaluation of the risk of interruption of operation of system elements and the resulting
consequences when complying with the legislative requirements for water management;
9.
detailed financial account aimed at ensuring the activities and technical equipment set out
in the plan;
10.
strategy for maintaining the sewage network;
11.
planned activities for the monitoring of infiltrated subterranean waters in mixed sewage
networks, as well as in sewage networks for domestic waste water in separate sewage networks.
(2) Plans for the technical operation of individual sections of the system shall include at least the
following basic elements:
1. pumping stations;
2. vacuum and pressurised equipment and devices, if such exist;
3. stop valve equipment and fittings;
4. holding tanks;
5. siphons and connected equipment;
(3) Plans for technical operation and maintenance shall be updated on a regular basis, taking into
account the data collated for past periods on the condition and development of the sewage network.
Article 160. (1) During the operation and maintenance of the sewage network, the reasons for any
problems which occur shall be established, and the following shall be analysed:
1. route of the pipeline;
2. place of the blockage and reason for the blockage or breakage of the pipes;
3. reasons for ground subsidence;
4. place and quality of the construction of the connections incorporated into the network;
5. the origin and places of unregulated connections to sewage sections and surface waters to the
sewage network;
6. quality of the repair and reconstruction works;
7. condition of the pipeline, the size of sediment and fatty substances adhering to the inner
surfaces of the pipes resulting from the cleaning of the pipeline;
8. quality and quantity of the waste waters;
9. water impermeability of the sewage network;
10. hydraulic conductivity of the sewage network or individual sections thereof;
11. reasons for the formation of sediment and the places of such, etc.
(2)Methods used to examine the sewage network include:
1. examination by coloration;
2. electronic determination of the location of the emergency;
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3. inspection by television camera;
4. visual control;
5. examination by mirror reflection;
6. measurements of the quantity of waste waters by means of electronic measurements and
registration devices installed at specific places along the sewage network;
7. determination of the quantities of waste waters by means of automatic sampling and
registering devices, installed at specific places along the sewage network;
8. determination of the volume of infiltrated waters;
9. determination of the level of water impermeability, etc.
Article 161. (1) In the event of a breach to the functional capability of the sewage network during
operation the following activities shall be carried out:
1. Review of the data collated from the periodical inspections of network functioning;
2. Determination of that part of the network where more detailed examinations and measures will
be carried out;
3. Prioritisation of matters which need to be resolved;
4. Systemisation and evaluation of the available information (legislative requirements, location,
material, sizes and condition of the pipelines, activities carried out to resolve problems, previous
inspections, hydraulic calculations and environmental assessments, type and quantity of discharged
industrial waters, subterranean waters, soil conditions, etc.);
5. Updating of the sewage network cadastre.
(2) In order to remedy operational problems in the event of obstructions to the normal functioning
of the sewage network, one or a number of the following aspects shall be inspected:
1. Hydraulic assessment (measurement of the waste water quantities, preparation and examination
of a hydraulic model — especially in the case of mixed sewage networks or separate sewage networks for
rain waters, an assessment of the hydraulic capability in the case of different types of rain fall and
ascertainment of hydraulic conductivity problems);
2. environmental impact assessments (registration of industrial water discharge, water
impermeability tests of the network and ascertainment of problems);
3. durability and load-bearing strength of the building structures (performance of inspections of
the building constructions, evaluation of their condition and ascertainment of defects and deformations).
(3) Depending on the reasons for the obstructions to the functioning of the sewage network the
corresponding actions shall be taken for their removal.
Article 162. During the technical operations of the sewage networks the following activities shall
be carried out periodically in accordance with the operation and maintenance plan:
1. the lids, steps or ladders and the bottom parts of the inspection shafts and inspection apertures
shall be cleaned from pollutants and if necessary repairs, reconstruction and renewal of shafts shall be
carried out and steps and ladders replaced;
2. Rainfall collector shafts shall be cleaned at least once per year and the quantity of collected
waste shall be examined and if necessary removed;
3. The condition of the structures of cascade shafts, lids and steps or ladders shall be constantly
monitored; the cascade shafts shall be regularly mechanically or hydraulically cleaned;
4. The water levels and frequency of overflow of the rainfall overflow shafts shall be monitored in
order to observe their effectiveness and the condition of their structures and cleaning from pollutants shall
monitored regularly.
5. The conditions of closure devices (stop valves or sluice gates) of the siphons shall be checked,
and if necessary they shall be repaired or replaced with new ones; a visual inspection of the pipelines
shall be carried out periodically and the entry and exit shafts of the siphons shall be cleaned and the
pipelines flushed out;
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6. The condition of the structure of the holding tanks, access facilities to their bottom levels, lids
and entry apertures, etc. shall be monitored regularly;
7. Open holding tanks shall be monitored regularly to ensure stable fixation of safety rails, ropes,
etc.;
8. Regular monitoring and maintenance of the pumping engines, electrical power supply,
pipelines, fixings, the building of the pumping station, etc. shall be carried out.
9. After emptying the holding tanks mechanical cleaning of their bottom levels and/or hydraulic
washing of the sediments shall be carried out;
10. Upon entering the enclosed facilities of the sewage network the necessary measures to ensure
the health and safety of operational personnel shall be carried out in accordance with the requirements of
the legislation for healthy and safe working conditions.
Article 163. (1) After each commencement of operations (after the initial construction and after
major repairs, renewals and reconstruction) each vacuum sewage system shall be subjected to the
following tests in compliance with the requirements of the Bulgarian standards for vacuum sewage
systems:
1. Noise;
2. Minimum vacuum in system branches;
3. Ratio between air and waste waters;
4. Vacuum restoration time;
5. Ability of the system to automatically restore its functionality;
6. Functioning of the control and alarm systems in the vacuum stations;
7. Time necessary for replacement of the induction valves and pumping engines
(2) During the technical operation of the vacuum sewage systems the following major activities
shall be carried out:
1. Internal inspection of the building sewage shafts and the devices therein at least once every six
months; once every year the collection tanks, fitting and ventilation pipes shall be cleaned and washed;
2. At least once every five years a major inspection of the induction valves shall be carried out and
if necessary they shall be replaced with new ones;
3. Every 1–2 weeks a visual inspection of the vacuum stations shall be carried out;
4. The working hours of the vacuum devices and the pressure pumps shall be recorded and the
consumption of electrical energy shall be accounted for.
5. Regular examinations of the mechanical and electrical equipment shall be carried out.
Article 164. During the technical operation of pressurised sewage systems the following major
activities shall be carried out:
1. If necessary network branches shall be purged with air or water through purging valves at the
beginning of each branch;
2. Feed tanks shall be examined and cleaned regularly;
3. Constant monitoring of the pumping engine control systems shall be carried out;
4. Unused sections of the pressurised sewage networks shall be excluded from operation, in order
to avoid a reduction of the pressure created by the pumps, and in order to prevent the infiltration of
subterranean waters into the network;
5. Regular examination of the functioning of the automatic air ducts.
Article 165. (1) During the technical operation of the pumping stations, periodical monitoring of
the condition of the pumping engines shall be carried out for the purposes of checking:
1. wear to the impeller and other moving parts of the pumps
2. seals between the shaft and body of the pumps;
3. pump and engine bearings;
4. fixation to base;
5. centring, etc.
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(2) Pumps and pipelines shall be cleaned and purged on a regular basis.
(3) The bottom and walls of the pumping stations shall be cleaned with a water jet.
(4) The flow, pressure, consumption of electrical energy and duration of the work of the pumping
engines shall be monitored and recorded every day.
(5) Every interruption to the functioning of the pumping engines or emergency shall be recorded
and measures shall be taken for their rapid resolution.
(6) The condition of the cooling and lubrication systems, control and monitoring devices, alarm
systems, ventilation system, and electrical installations for high and low tension, etc. shall be monitored
every day.
(7) In compliance with the requirements of the legislative acts, safe access shall be guaranteed for
personnel to any premises or shafts in which there is a possibility of toxic or explosive gaseous mixtures.
(8) Sewage pumping stations shall be provided with:
1. drinking water;
2. signs indicating dangerous locations;
3. emergency medical aid resources
4. personal safety items, etc.
Section II
Collection, storage, processing and updating of information relating to
the condition, technical operation and maintenance of sewage networks
Article 166. (1) During the operation of sewage networks information shall be collected,
processed and stored for the following purposes:
1. normal operational functioning;
2. preparation of reports on the condition of the network, the need for on-going maintenance,
repairs and reconstruction of the sewage network and the related facilities, incidental damages and
emergencies, the healthy and safe working conditions for the personnel and risk assessment for hydraulic
overloading and flooding;
3. preparation and maintenance of the cadastral plan of the sewage system;
4. preparation of plans for the operation and maintenance of the sewage network;
5. inspection of the sewage network in the event of any interruption to its functioning.
(2) The information referred to in paragraph 1 shall contain at least the following information:
1. list of the elements of the system including pipelines and waste water drains, shafts, pumping
stations, rainfall overflows, holding tanks and other facilities;
2. relating to the actions carried out during regular technical operation and relating to the
condition of the sewage network and related facilities;
3. detailed data about permitted connections to the sewage system — industrial waste waters,
danger substances, etc.;
4. detailed data about permitted connections to the water collector — overflow drains after
rainfall overflow collectors, holding tanks and pumping stations;
5. reports containing results from inspections of the sewage network, including results from
inspections with a television camera;
6. reports relating to incidental damages — blockages, pipe breakages, interruptions to the
operations of the pumping stations and pressurised pipelines, flooding of buildings and territories,
inadmissible incidental pollution of water collectors, etc.;
7. relating to model simulation inspections carried out under the conditions of suitable scenarios,
in order to determine the behaviour and hydraulic capacity of the sewage network in periods of intense
rainfall, and if necessary the need for reconstruction of the network shall be considered;
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8. data from the network of simultaneous monitoring stations and recording of rainfall and water
quantities in the sewage network for the purposes of calibrating and examining the network simulation
models;
9. reports relating to work carried out during the planned maintenance of the sewage network;
10. reports relating to actions carried out and the reaction time for the resolution of emergencies
along the sewage network;
11. reports relating to reconstructions and extensions to the sewage network and related facilities
carried out;
12. data relating to the type of work and time required to lay the pipes, fixings and attachments
during repair, reconstruction or extension of the sewage network;
13. data relating to the costs of resolving the consequences of emergencies and for the
maintenance of the network;
14. data relating to sickness, injuries or fatal accidents to persons from the operational personnel
and members of the public;
15. data relating to complaints about the spread of acute odours from the sewage network;
16. data relating to complaints about the flooding of buildings and ground caused by the
hydraulic overloading or inadequate functioning of sections of the sewage network;
17. data relating to the condition and functioning of the pumps, electromechanical and electronic
devices and control systems of the sewage system;
18. reports relating to risk assessment of hydraulic overloading of the sewage system and
flooding of urbanised territories.
(3) The information referred to in paragraph 2 shall be included in a timely manner in the cadastral
plan of the sewage system.
Chapter sixteen
REQUIREMENTS DURING THE CONSTRUCTION OF WASTE WATER PURIFICATION PLANTS
Article 167. (1) The primary and auxiliary facilities and plants, auxiliary, service and
administrative buildings and infrastructure within the territory of waste water purification plants shall be
constructed in accordance with the building documents, regulations and legislative provisions of this
order and the legislative provisions which set out the rules for the implementation of the CIW for types of
building constructions.
(2) Facilities which are built into excavation trenches shall be back-filled after the successful
completion of tests for strength and water impermeability after the compilation of the relevant acceptance
acts.
(3) In the event of the presence of high levels of subterranean waters, suitable drainage systems
shall be envisaged in order to reduce the water levels and these shall be in constant operation during
construction work, and if necessary during the operation of the WWPP.
Article 168. (1) The installation of pumping engines, compressors, pipelines and fixing shall be
carried out in accordance with the design plan requirements and the requirements of the relevant
manufacturers.
(2) During installation of reverse valves the flow direction noted on the cover shall be complied
with.
(3) During the installation of pipelines their designation as envisaged in the design plan shall be
taken into account.
(4) Sound insulation shall be fitted to the compressors in accordance with the design plan and they
shall be located in sound-insulated premises.
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(5) Pumping and compressor engines shall be installed after precise centring and stable attachment
to the foundations.
Article 169. The construction of waste water purification plants upon landslide territories, mine
workings and construction site scree shall commence after the final completion of all technical measures
required to strengthen the ground.
Article 170. (1) Pipelines and drains shall be constructed in accordance with the design
requirements and the corresponding manufacturer.
(2) The type and designation of the pipelines shall be marked indelibly and clearly for the
purposes of their identification during the technical operation of the water purification plant.
Chapter seventeen
REQUIREMENTS FOR THE TESTING AND COMMENCEMENT OF OPERATION OF WASTE
WATER PURIFICATION PLANTS
Section I
General Requirements
Article 171. (1) Every facility for water and sediment treatment shall be subjected to hydraulic
testing to determine the planned strength and water impermeability.
(2) The testing of machines and devices connected to the technological facilities for the purposes
of determining their integrity, durability, functionality and technical parameters shall be carried out in
compliance with the design plan requirements and the corresponding manufacturer's requirements.
Article 172. For the purposes of the approval of waste water and sediment treatment plants,
evidence must be provided of their hydraulic conductivity and technological functionality in accordance
with the legislative requirements and technological parameters set out in the design plan by means of
performing the relative tests and presentation of the acts and protocols issued during their construction.
Article 173. (1) Waste water purification plants shall be approved and their operation commenced
in phases, in accordance with their separate technological stages and technological establishments.
(2) The commencement of operation for each technological stage or technological plant shall be
carried out after the commencement of operation or approval of the preceding technological phases or
plants along the route of the water or sediment correspondingly.
(3) When commencing the operation of each technological phase or technological plant, single
tests (for individual engines or facilities) and multiple 72-hour tests of their technological functioning
shall be carried out, and a protocol thereof shall be complied.
(4) The activities required for commencement of operations at every technological phase or
technological establishment as well as their sequence and duration must comply with the requirements of
the technical instructions in the design plan and the instructions for operation.
Article 174. (1) The biological phase of the purification plant shall be brought into operation after
the sediment treatment plants are completely ready for operations.
(2) Bioreactors and secondary settling tanks shall be brought into operation after the completion of
the necessary adjustments of the mechanical equipment and related devices.
Article 175. (1) The approval of purification plants or their technological stages and technological
establishments shall be carried out after the overall assessment of their construction in compliance with
the building documents and their suitability for the commencement of operation.
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(2) For the purposes of approving purification plants or their technological stages or technological
establishments, the acts and protocols compiled in compliance with Order No 3 of 2003 for the
compilation of construction acts and protocols shall be presented.
(3) The issuing of an approval and permission for use of purification plants or their technological
stages and technological establishments shall be carried out in compliance with the legislative
requirements.
Section II
Testing of Purification Plants
Article 176. (1) The hydraulic testing of water or sediment treatment plants shall be carried out
upon completion of all CIW, when the design plan strength of the concrete has been achieved and when
there are no registered defects in the structure or deviations from the design plan.
(2) The hydraulic testing of the plants shall be carried out by initially filling them with water up to
a depth of 1 m for a period of 24 hours, in order to assess the bottom of the structure for water
impermeability, after which the water filling shall continue until the design plan elevation of the
maximum water level.
(3) The results of the hydraulic testing of the plant for water impermeability shall be measured no
earlier than 5 days after it has been filled with water.
(4) The plants shall be deemed water-impermeable, if the daily loss of water is no more than 3
2
l/m from the wet surfaces of the walls and bottom, no leakage is observed through the walls and joints
and the foundations are not damp. When testing open-air plants, losses due to evaporation of the open
water surface shall be recorded.
Article 177. (1) Pressurised vessels (tanks and plants) shall undergo tests for strength and water
impermeability under pressure equal to the nominal operational pressure multiplied by a ratio of 1.5.
(2) Testing of pressurised vessels for strength and water impermeability shall be deemed
successful if no leakages or damage to them or the related pipe connectors, fixings and attachments is
observed for a period of 10 minutes at test pressure.
Section III
Testing of technological sites and communications
Article 178. (1) Water supply pipelines, sewage and technological pipelines on waste water
purification plants shall be tested for strength and impermeability in accordance with the instructions in
the design plan and the requirements of this order.
(2) Testing of pressurised site pipelines laid in trenches, inaccessible tunnels or channels shall be
carried out in two stages:
1.
Preliminary testing (strength tests) before back-filling of the trench and installation of
fittings;
2.
Final testing (testing for water impermeability) — after covering the trench and
completion of all CIW in the given section of the pipeline, but before the installation of the hydrants,
safety and air valves; during testing these shall be tightly sealed.
(3) In the case of mechanically constructed steel pipelines, the two stages referred to in
paragraph 2 can be carried out simultaneously after covering the pipeline. Testing of steel pipelines shall
be carried out when positive results from the quality control of the welds are available.
Article 179. (1) Strength-testing of pressurised sewage pipelines shall be carried out under
conditions of internal pressure as set out in the design plan, and in the absence of such data, the pressure
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shall be deemed equal to operational pressure increased by 0.5 MPa but no less than the hydrostatic
pressure increased by 0.2 MPa. Prior to undertaking strength testing the pressurised pipelines shall be
filled with water at least 72 hours in advance. A pressurised pipeline shall be deemed to have successfully
passed the strength test, if no leakages or damp spots are registered on the pipes or connectors for a period
of 30 minutes.
(2) Water-impermeability testing of pressurised sewage pipelines shall be carried out under
conditions of internal pressure, equal to operational pressure for a period of 24 hours for steel pipelines
and 72 hours in the case of steel-concrete pipelines. A pressurised pipeline shall be deemed to have
successfully passed water-impermeability testing, if at the end of the corresponding test period the
pressure has fallen by no more than 0.1 MPa.
(3) On-site water pipelines for drinking water shall be tested and disinfected in accordance with
the requirements of Order No 2, 2005, for the design, construction and operation of water-supply systems
(promulgated, SG, ed. 34, 2005).
(4) Unpressurised sewage pipelines and inspection shafts and apertures shall be tested for water
impermeability in accordance with the design plan requirements and the requirements of this order.
(5) Protocol records shall be compiled in relation to the preliminary and final tests.
Article 180. (1) The shafts shall be tested for water impermeability no earlier than 24 hours after
they are filled with water.
(2) The preliminary testing of shafts for water impermeability shall be deemed successful if there
is no leakage of water. Final testing for water impermeability shall be deemed successful, if the level of
water in the shaft falls by no more than 0.2 m over a period of 30 min.
(3) Protocol records shall be compiled in relation to the preliminary and final tests.
Article 181. Hydraulic testing of heating pipes on waste water purification plants shall be carried
out in compliance with the corresponding legislative acts, design plan requirements and the instructions of
the manufacturers of the pipes.
Chapter eighteen
TECHNICAL OPERATION OF PURIFICATION PLANTS
Article 182. During the technical operation of waste water and sediment treatment plants the
design plan requirements for technical operation shall be complied in accordance with the attached
technological processes in the aims of ensuring a sustainable hydraulic and technical regime under
dynamic conditions throughout their entire operational period in accordance with the requirements of the
design plan and the applicable legislative acts for conservation of water and the environment.
Article 183. (1) During technical operation of the plants referred to in Article 182, any harmful
effects as a result of odours, noise, toxic substances, aerosols and foam shall be monitored and limited.
(2) Unauthorised persons shall not be admitted to the sites of purification plants.
Article 184. (1) During the technical operation of waste water purification plants, healthy and safe
working conditions shall be provided and guaranteed for all the personnel in accordance with the
requirements of the legislative acts and the risks and dangers arising from the technological processes
relating to the purification of waste water shall be set out.
(2) In the performance of activities connected with taking of samples at the entry and exit points
of the individual plant units or sewage currents, safe working conditions for the personnel and the
corresponding sampling equipment shall be provided.
(3) Laboratory analyses shall be carried out in accordance with the plan for in-house monitoring of
WWPP.
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(4) In-house monitoring for the purposes of implementing the requirements of a discharge permit
shall be carried out in accordance with the requirements of the order referred to in Article 135(1)(12) of
the Law on Waters.
Article 185. In enclosed premises where there is a possibility of a damp atmosphere, polluted air
or danger of explosion, suitable ventilation, gas warning system and a signal system shall be envisaged.
Article 186. In order to provide the necessary conditions for technical operation, measures shall
be taken to prevent freezing and icing of roads and paths on the territory of the purification plant.
Article 187. During the storage and transportation of dangerous chemicals or fuels, the necessary
measures to prevent harmful effects upon the environment from accidental spillage and evaporation shall
be taken.
Article 188. Welding work on the facilities and pipelines containing easily flammable and/or
explosive liquids, fuels or gases, or pressurised vessels, etc. shall be carried out by highly qualified
personnel with a documented licence and with the use of equipment designed to indicate possible leaks
and gas intoxication.
Article 189. (1) During the technical operation of pumping and compressor plants the following
shall be monitored:
1.
flow;
2.
pressure;
3.
duration of work over a 24-hour period;
4.
electricity consumption;
5.
air temperature in the pipelines after the compressors, etc.
(2) During operation any damages or incidents shall be recorded.
(3) In the case of compressors with low pressure and high air exchange (air fans) the content of
dust and/or oil in the air shall be monitored.
Article 190. (1) Monitoring of the condition of the pumps, compressors, motors, fixings,
measurement devices, etc. shall be carried out every day.
(2) During the operation of pumps and compressors, the hermitic seals of the pipelines and fixings
shall be inspected.
Article 191. (1) Upon commencement of operation after repair or replacement of a pump or
compressor engine the direction of rotation of the impeller shall be checked for compliance with the
requirements.
(2) At least once every six months the distance between the impeller and the body of the pump or
compressor shall be inspected.
(3) Cleaning, lubrication and monitoring of the water or oil in the hydraulic enclosures of the shaft
seals shall be carried out on a regular basis.
(4) Replacement of oil, filters, bearings and other parts shall be carried out in accordance with the
instructions for operation and maintenance of the WWPP.
Article 191. Pumps and compressors shall be started, stopped and inspected in compliance with
the manufacturers' instructions.
Article 192. (1) During technical operation of on-site technical infrastructure, its condition shall
be monitored and if necessary repairs and/or cleaning shall be carried out.
(2) In the case of large open-air channels, safety railings, lifebelts, ropes and other suitable
protective equipment shall be installed.
Article 193. (1) Pipelines shall be examined for accidental leakages and for damage to heat
insulation (if such is envisaged).
(2) Metal pipes subject to the risk of corrosion shall be cleaned from rust and repainted on a
regular basis.
(3) In those cases when the pipeline is not used in the winter, it shall be emptied and the stop
valves shall be left open.
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(4) Markings indicating the type and designation of the pipelines shall be kept clear and legible.
(5) When the stop valves are not used every day, their technical condition shall be periodically
examined.
Article 194. During the technical operation of gas pipelines they shall be regularly inspected for
hermeticity by means of suitable methods and measurement devices.
Article 195. (1) Roads, sites and paths to the buildings and plants shall be kept clean and the any
registered damage shall be timely rectified.
(2) During the winter snow and/or ice shall be cleaned from the roads, sites and paths.
Additional Provisions
Section 1. According to the meaning of this Order:
1. “Water volume in dry weather” is the quantity of water which is not affected by rainfall or snow
melt.
2. “Water collector” is every water object into which waste or rain water is discharged.
3. “Walter collection area” is an area drainable into a drainage system, sewage system or water
current.
4. “Protected zone” is the territory between pumping stations or waste water purification plants
and the boundary of the residential zone of urbanised territories, resorts, tourist or other inhabited regions.
5. “Gravity sewage system” is a system in which the flow is caused by gravitational forces and the
pipeline is planned to operate under normal conditions of partial filling.
6. “Mixed sewage network” is a system in which residential, industrial and rain water is collected
and transported in one common pipe network.
7. “Separate sewage network” is a system in which residential and industrial waste water is
collected and transported in one common pipe network, while rain water is collected in a separate pipe
network and between the two networks there is no hydraulic connection.
8. “Semi-separate sewage network” is a system in which residential and industrial waste water is
collected and transported in one common pipe network, while rain water is collected in a separate pipe
network and between the two networks there is a specific hydraulic connection which allows the first
(most polluted) rain waters to be taken to a waste water purification plant.
9. “Combined sewage network” is a combined mixed and separate system in certain regions for a
given residential area.
10. “Rain intensity” is the height of rain fall over a unit time, or volume of rainfall for a unit of
time upon a unit of ground area.
11. “Flood” is a condition in which waste and/or industrial waters escape from a given drainage or
sewage system or cannot enter it, thus remaining on the surface or entering buildings;
12. “Flow ratio” is a ration which depends on the surface covering and by which the quantity of
rain water must be multiplied, in order to receive the expected flow which is drained into the drainage or
sewage system.
13. “Economically justified operational period” is in accordance to Section 5(65) of the
supplementary provisions of the Law on Territorial Development.
14. “Inspection aperture” is an aperture with a mobile cover built upon a pipeline or waste water
channel, which allows for a cleaning or monitoring device to be inserted from ground level but does not
allow access to personnel.
15. “Self-cleaning” is the capability of the flow in the pipeline or waste water channel to remove
solid particles which otherwise would have precipitated inside them.
16. “Flow simulation” is the modelling of flows in the sewage systems.
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17. “Pressurised sewage network” is a sewage network in which waste water is transported under
pressure by means of pumping.
18. “Vacuum sewage network” is a sewage network in which waste water is transported under
vacuum created by the relevant devices and facilities.
19. “Hydraulic overloading (overfilling)” is a condition in which waste water is transported under
pressure in an unpressurised pipe system without flooding the surface or causing a flood.
20. “Technologies” “Technology” in waste water purification includes all technology used as well
as the manner in which a given installation is designed, built, maintained, controlled and removed from
operation.
21. “Current knowledge” is the level of technology used in waste water purification, developed to
a scale which allows its application in real economic and technological conditions, taking into account the
costs and benefits, experience of its use and its degree of suitability and affordability for the sewage
system operator.
22. “Best available technologies” are the most effective and advanced stage in the development in
activities and methods used for waste water purification which display practical suitability of the relevant
techniques in the aims of guaranteeing the relevant values of admissible emissions, in such a way as to
prevent, or when this is practically impossible, to reduce emissions and effects upon the environment.
23. “Best practices” are purification methods or technologies in relation to which experience and
research have shown that they lead to the desired results, are used as a basis for comparison and
consistently give good results in comparison with those achieved by other means. In the aims of the
successful and reliable use of the best practices all available knowledge and technologies shall be used.
24. “Equivalent inhabitant” is a term used to compare organic pollution load from industrial
waters to organic pollution load from residential waters. Equivalent inhabitants are fictitious residents
who would have caused a load on the purification plant equivalent to the load caused by industrial waters.
Section 2. In the event of breaches of this order the administrative provisions of the Law on
Territorial Planning and the Law on Administrative Contraventions and Sanctions, unless a more serious
sanction is envisaged in another law.
Interim and Final Provisions
Section 3. This order is issued on the basis of Section 18(1) of the LTP and replaces the
“Standards for the design of sewage systems” set out in Instruction No RD-02-14-140 of the 17.IV.1989
of the Chairman of the Committee of Territorial and Residential Planning (Published in the Bulletin of
Construction and Architecture, ed. 9 and 10, 1989; amended, ed. 1, 1993) and the Rules on the
Implementation and Approval of CIW for sewage systems in the Rules for Implementation and Approval
of Construction and Installation Work — External networks and facilities for water supply, sewage and
heat supply (published in the Bulletin of Construction and Architecture, ed. 4, 1984; amended, ed. 3 and
4, 1985; amended, ed. 1, 1993).
Section 4. (1) All procedures relating to the approval of an investment plan and issuing of
permission for construction which have already begun shall be completed in the current manner.
(2) The date of a commenced procedure for approval of an investment project and the issuing of
permission for construction shall be the date on which the investment project was submitted for approval
by the competent body. The existence of an approved ideal investment project shall be deemed a
commenced procedure.
Section 5. This order shall be applicable for sewage systems planned after promulgation in the
“State Gazette”.
Section 6 This order has completed the procedure for exchange of information in the area of
technical regulations in accordance with Decree No 165 of the Council of Ministers, 2004, on the
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organisation and coordination of exchange of information about technical regulations and rules for the
purposes of information society services and for the purposes of establishing procedures connected with
the application of certain national technical rules for products legally offered for sale on the Bulgarian
market (promulgated, State Gazette, ed. 64, 2004), which introduces Directive 98/34/EC, amended by
Directive 98/48/EC.
Section 7. This order comes into force one month after its promulgation in the “State Gazette”.
MINISTER:
LILYANA PAVLOVA
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Appendix I
to Article 2(5) and Article 108(1)(6)
Minimum protective zones for pumping stations and for waste water purification plants under
150 000 EI
No
per
row
Type of facilities
1.
Facilities for mechanical and
biological purification in
combination with drying fields
for stabilized sediment and for
individually located drying
fields
Facilities for mechanical and
biological purification in
combination with mechanical
desiccation of sediment in
enclosed premises or without
mechanical sediment treatment
Filtration fields
Irrigation fields
Biological lakes
Oxidation channels
Pumping stations
2.
3.
4.
5.
6.
7.
From 200 EI
to 400 EI
100
Protective zones, m
From 400
From 100 EI to
EI to 1 000
25 000 ЕI
EI
150
200
From 25 000
EI to 150 000
EI
400
75
100
150
300
100
70
100
70
15
200
150
200
150
15
300
200
200
20
500
20
Notes:
1. In the case of pumping stations an 80 % reduction in the distances stated is permitted on the
condition that the technological equipment of the facilities does not allow the production of harmful
emissions and unpleasant odours.
2. In the case of purification plant facilities an 80 % reduction of the distances stated is permitted
after a technical report that the purification technologies, facilities and/or technological equipment used
are fitted with the relevant methods for restricting harmful Emissions and unpleasant odours or preventing
the formation of such.
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Appendix 2
to Article 6(2), Article 18 and Article 156(3)
Determining the quantity of rainfall for the purposes of the hydraulic measurement of gravity
sewage networks, based on the rational method
1. When using the rational method, the quantity of waste water rainfall (Qr) measured is based on
the following formula:
Qr = qt ψ av. F, l/s
(1.1),
In which:
qt is the intensity of the rainfall measured, l/s.ha;
ψ av. - the average flow ration of the territory served by the sewage pipeline;
F – the area served by the sewage pipeline, ha.
1.1 The intensity of the rainfall measured is determined by means of a hietogram with specific
repetition, created from the correspondingly processed data from the closest pluviograph in the national
network of rainfall stations with a monitoring period of no less than 40 years. In the absence of such data
the rainfall used for measurement can be determined on the basis of processed and published data as well
as empirical dependencies valid for the territory of the Republic of Bulgaria, as well as on the basis of the
method shown at the end of this appendix.
1.2 Single load period in the sewage network P is determined in accordance with Table 1
Table 1
No,
Single network load period *
per
Type of urbanized territory
P, year
row
and its elements
1. Rainfall drainage
0.5
2. Residential regions with up to 10 000 residents
1–2
Residential regions with more than 10 000 residents
3. Residential territories
2–3
4. Industrial territories
1–3
5. Mixed central territories, public service territories in
2–5
urbanised territories
6. Subterranean road facilities
10
* Hydraulic overload must not occur during rainfall measurement
Notes:
1. The single load period for sewage networks is selected in relation to the type of sewage system,
the extent of built-up land, ground configuration and the specific local conditions, taking into account the
initial capital investment in proportion to the damages from overloading and the need for possible future
unforeseen extensions.
2. Given justifications a deviation from the indicated values is permissible.
1.3 The value of intensity of the rainfall measured for the particular section of the sewage network
qt is determined by the hietogram based on the drainage time (t0) of the rainfall water from the most
distant point of the water collection area to the particular section. Drainage time t0 in minutes is
determined on the basis of the following formula:
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t 0  5  a t k
(1.2),
In which:
A is the retention ratio which reflects the retention capability of the network; a = 1.2  2, and in
steeper grounds a lower value is recommended;
 t k is the sum of the drainage times used for calculations according to sewage network sections
along the water current from the most distant point of the relevant water collection point to the section
being measured.
1.4 The average drainage ratio ψ av. is determined on the basis of the values of the drainage ratio
for the separate types of surface coverings and their surface area within the territory served by the sewage
network. In the absence of specific data on the values of the drainage ratio ψ for the separate types of
covering, its value is considered to be that shown in Table 2.
Table 2
No,
per
row
1.
2.
3.
4.
5.
6.
7.
8.
Type of surface covering
Coverings – all types
Dense coverings - asphalt, jointed paving, pavements and tiled ground
Paving with unfilled joints and crushed stone gravel coverings
Cobbles
Crushed stone coverings
Untiled yards, station, warehouse and sports grounds
Grass areas, parks and gardens, including alleys and paths within them
Cultivable grounds
Values of
drainage ratio ψ
0.90–0.95
0.85–0.90
0.50–0.70
0.35–0.50
0.30 – 0.40
0.15 – 0.30
0.10 – 0.20
0.10
2. Method of determining the intensity of measured rainfall
2.1 Depending on the intensity of the rainfall measured and given the same degree of frequently,
the country is divided into two zones - I and II, which are shown on the following map.
During a period of a single overloading of the sewage network, one year q5 = 255 l/s.ha – for zone
I, and q5 = 255 l/s.ha – for zone II.
2.2 The intensity of the rainfall measured qt в l/s.ha in the relevant zone is determined on the basis
of the following formulae:
- For zone I
q t,I p = [9.4771-3.1359 lg (t+5)]3(1-lg.p)+[11.2883-3.5422 lg (t+5)]3 lg. p, l/s.ha (1.3);
- For zone II
q t,II p = [9.0899-3.0077 lg .(t+5)]3 (1-lg.p)+[10.8270-3.3974 lg.(t+5)]3 lg p, l/s.ha
(1.4),
In which:
t is the duration of the rainfall in minutes;
p – is the period of frequency of rainfall in years, correspondingly the period of single overload
of the sewage networks.
Formulae (1.3) and (1.4) are valid for t from 5 to 90 minutes and for p – from 0.5 to 100 years.
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When the residential area is situated on the border between two zones, the intensity of the rainfall
measured is equal to the average data for both zones.
Map of the intensity of the rainfall measured give one and the same degree of frequency
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I зона
II зона
Зона = Zone
Zone I: Novo Selo, Vidin, Gramada. Lom, Ruse, Razgrad, Gen. Toshevo. Varna, Cape
Kaliakra, Malko Tarnovo, Elhovo, Harmanli, Svilengrad, Ivailovgrad, Haskovo, Karzdhali,
Srednogortsi, Plovdiv, Batak reservoir, Gotse Delchev, Sandanski, Dupnitsa, Samokov, Iskar reservoir,
Studena reservoir, Pernik
Zone II: Vratsa, Knezha, Roman, Dragoman, Sofia, Vakarel, Ikhtiman, Botevgrad,
Koprivshtitsa, Chiflik, Ivailo, Karlovo, Sevlievo, Pavlikeni, Veliko Tarnovo, Kazanlak, Stara Zagora,
Chirpan, Sadovo, Targovishte, Omurtag, Sliven, Yambol, Samuil, Shumen, Liulyakovo, Karnobat
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Appendix 3
to Article 7
Requirements for the investment project for sewage systems in relation to the sewage
systems and attached facilities
1. The development stages of investment projects for sewage networks and attached
facilities shall be determined by the investor in accordance with the legislative requirements
and contractual conditions for its construction.
2. The minimum volume of pre-investment studies shall include:
a) data relating to the existing situation and the project requirements for the territorial
planning of the residential area (planning, cadastral and/or elevation plans);
b) climatic and meteorological data for the region of the residential area;
c) geological and hydrogeological data about the residential area;
d) demographic data about the residential area at the moment of planning and
forecast data for the end of the economically justified operational period in accordance with
the requirements of the investor;
e) data about the industrial, communal residential and agricultural enterprises within
the territory of the residential area at the moment of planning and forecast data for the end of
the economically justified operational period;
f) data about the potential of territories with specific and preventive planning
protection (if such exists) in connection with nature preservation regimes and cultural and
historic heritage sites;
g) other data (circumstances) required by the type and specific nature of the local
conditions;
h) forecasts for developments of Water and Sewage systems in general structure
plans;
i) data about existing water supply systems;
j) data about existing sewage systems (sewage network and WWPP);
k) data about water collector – in accordance with the requirements of the current
legislative and administrative acts;
l) requirement for the replacement, reconstruction or new construction of a sewage
system (sewage network and WWPP).
3. Detailed clarification of the investment intention shall include:
a) clarification of the territorial scope of the investment intention;
b) examination of alternative solutions for the sewage network and drainage
collectors to the WWPP;
c) clarification of the need for preparation/amendment to the detailed territorial plan;
d) determination of the indicative value of the alternative solutions;
e) determination of responsibilities of the participants in the investment process;
f) risk assessment of the investment intention;
g) explanation of the social requirement and effectiveness of the investment
initiative, including improvement to the territorial planning, hygiene and ecological
conditions, creation of employment and provision of public services;
h) drawings: general situation to a suitable scale showing the territorial scope of the
investment intention and the basic elements of the alternative solutions for the sewage system
( sewage network and WWPP).
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4. The minimum scope of the conceptual project for the sewage network and attached
facilities shall include:
a) explanatory note including information (data and studies) described in Point 2; the
explanatory note shall explain the proposed project solutions and their compliance with the
requirements of Article 169 of the Law on Territorial Planning; the technological solutions
shall examine at least two comparable options of the sewage network and attached facilities;
when grounds are given the project can consist of a single option;
b) hydraulic calculations of the sewage network and attached facilities in accordance
with the requirements of the project design;
c) construction phases;
d) the quantitative and value calculations based on summarized indicators and
generalized values as per options, which clearly reflect the construction phases;
e) technical and economic comparison of the options and proposal for selection of an
option for the subsequent phase of planning;
f) drawings:
General situation of the urbanized territory to a suitable scale with clear indication of
the location of the territory included in the project;
 Situation in M 1:2000 (1000) – plan with allocation of areas;
 Situation in M 1:2000 (1000) – plan with measurement data;
 Situation in a suitable scale with clear indication of the construction phases;
 Lateral profile in M 1:2000 of the main collectors;
 Horizontal and vertical cross section of the facilities to a suitable scale;
 Cross section profiles of the streets at typical points with clear marking of the
existing and planned subterranean infrastructure.
5. The planned parts of the technical and/or working design plan of the sewage
networks shall be developed in accordance with Order No 4, 2001, on the scope and content
of investment projects (promulgated, State Gazette, ed. 51, 2001).
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Appendix 4
to Article 7
Requirements for the investment project in relation to waste water purification
plants
1. The stages of the development of the investment projects for waste water
purification plants shall be determined by the investor in accordance with the legislative
requirements and contractual conditions for its construction.
2. The minimum volume of pre-investment studies shall include:
a) calculation of the water volumes and pollutant loads at the present moment and at
the end of the operational period;
b) necessary purification level based on the requirements of the discharge permit;
c) choice of purification technology, taking into account the possibilities for the
making safe, disposal and use of sediments;
d) choice of a suitable site, data for the site and adjacent technical infrastructure
(transport, water supply, energy supply, etc.) accompanied by geodesic, engineering and
hydro-engineering reports about the site and adjacent infrastructure;
d) hydrological data about the water collector designated for discharge of purified
waste water;
e) summarised indications of quantity and value calculations;
f) forecast values of operational costs and price per 1 m3 of purified water;
g) social tolerability of the investment;
h) data about any existing waste water purification plant; in the event of an existing
WWPP the technical and operational parameters at the moment of the investment shall be
analysed and grounds shall be given for a choice between reconstruction of the existing
WWPP and/or construction of a new WWPP;
j) construction phases;
k) development of two or more options of waste water treatment or sediment
treatment technologies;
l) graphics containing at least:
 Flow chart of the proposed technological schemes;
 General plan with clearly marked communications between the buildings and
facilities;
 In the event of an existing WWPP – technological diagram and general plan of
the existing WWPP.
3. The minimum volume of the “Technology” part of the conceptual project shall
contain the following components at least:
a) explanatory note containing a description of the technologies and processes being
considered;
b) technological and hydraulic measurement of the basic facilities and technological
measurement of the buildings;
c) specification of the main machinery and technological equipment;
d) specification of the main electricity consumers and calculations of operating hours
and expected total level of annual electricity consumption; energy balance;
e) summary indications of quantitative and value calculations;
f) forecast values of operational costs and price per 1 m3 of purified water;
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g) plans to a suitable scale – general plan, lateral profile along the water flow
direction, technological diagram;
j) planning requirements for all design plan areas with the minimum technological
requirements (in the event that a preliminary phase has not been prepared).
4. The minimum volume of the “Technology” part of the conceptual project shall
contain the following components at least:
a) explanatory note containing a detailed description of the technologies and
processes being considered;
b) technological calculations and measurements which give more specific details to
those set out in the conceptual project;
c) specification of the main machinery and technological equipment with detailed
data about the technical parameters with accompanying technical documentation;
d) specification of the main materials and products required;
e) specification of the main electricity consuming sources and calculations of
operating hours and expected total level of annual electricity consumption; energy balance;
f) specification of the main measurement devices and apparatus;
g) specification of the main pipe connectors with a description of their length,
diameter and material;
e) instructions for the commencement of operations and technical operations of the
individual technological phases, facilities and technical conduits;
f) main drawings to a suitable scale:
 detailed technological diagram clearly showing all the monitoring and measuring
devices showing specific features;
 general plan clearly showing all the purification facilities along the technological
flow route of the waste water and sediment, including the discharge point for
purified waters into the water collector, pumping stations, technical conduits
(from all planned sections), roads and paths, planned buildings, and green areas,
etc.;
 hydraulic profile along the water flow;
 technological diagram;
 plans, horizontal and vertical cross-sections of all buildings and facilities with
clear marking of the pipe networks and fittings with the corresponding
elevations, as well as the elevations of the existing ground (in the event of an
existing WWPP, clear indications of what shall be kept and what shall be
changed);
 details of the facilities and details of non-standard elements;
 other plans and diagrams – to a suitable scale, when these are required by the
specific nature of the technology used;
 cross sections at typical points clearly showing the subterranean infrastructure;
 in the case of buildings and facilities – detailed schematics, cross-sections,
façades – to M 1:100 or M.1:200.
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Appendix No 5
to Article 8
List of Bulgarian standards applicable in the design, construction and operation of
sewage systems
1. BDS EN 752 “Sewage systems outside buildings”.
2. BDS EN 476 “General requirements for elements used in sewage system pipelines”
3. BDS EN 1091 “Vacuum sewage systems outside buildings”
4. BDS 1295-1 “Static measurement of underground pipelines given different load
conditions. Part 1: General Requirements”
5. BDS EN 1610 “Construction and testing of sewage systems”
6. BDS EN 1671 “Pressurised sewage systems outside buildings”
7. BDS EN 12255-1 “Waste Water Purification Plants. Part 1: General construction
principles”
8. BDS EN 12255-3 “Waste Water Purification Plants. Part 3: Preliminary water
purification”
9. BDS EN 12255-4 “Waste Water Purification Plants. Part 4: Primary precipitation”
10. BDS EN 12255-5 “Waste Water Purification Plants. Part 5: Waste water
purification in lakes (lagoons)”
11. BDS EN 12255-6 “Waste Water Purification Plants. Part 6: Purification methods
with active sediments”
12. BDS EN 12255-7 “Waste Water Purification Plants. Part 7: Fixed biological film
reactors”
13. BDS EN 12255-8 “Waste Water Purification Plants. Part 8: Treatment and
disposal of sediments”
14. BDS EN 12255-9 “Waste Water Purification Plants. Part 9: Monitoring of odours
and ventilation”
15. BDS EN 12255-10 “Waste Water Purification Plants. Part 10: General safety
principles”
16. BDS EN 12255-11 “Waste Water Purification Plants. Part 11: Required general
data”
17. BDS EN 12255-12 “Waste Water Purification Plants. Part 12: Control and
automation”
18. BDS EN 12255-13 “Waste Water Purification Plants. Part 13: Chemical cleaning.
Waste water purification by means of coagulation/flocculation”
19. BDS EN 12255-14 “Waste Water Purification Plants. Part 14: Disinfection”
20. BDS EN 12255-15 “Waste Water Purification Plants. Part 15: Measurement of
oxygen supplied to clean water in aeration pools of biological plants”
21. BDS EN 12255-16 “Waste Water Purification Plants. Part 16: Physical
(mechanical) filtration”
22. BDS EN 13380 “General requirements for elements in the refurbishment and
repair of sewage systems outside buildings”
23. BDS EN 135080-1 “Condition of sewage systems outside buildings Part 1:
General Requirements”
24. BDS EN 135080-2 “Condition of sewage systems outside buildings Part 2: Visual
control coding system”
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25. BDS EN 14457 “General requirements for elements designed especially for use in
the trenchless construction of sewage networks”
26. BDS EN 14654-1 “Control and monitoring of activities connected with the
cleaning of sewage channels and pipelines. Part 1: Cleaning of pipelines”
27. BDS EN 14801 “Conditions for the pressure classification of products used in
water and sewage pipelines”
28. BDS EN 12889 “Trenchless construction and testing of waste water pipelines and
channels”
29. BDS EN 124 “Covers for water collectors, siphons and inspection shafts for
transport and pedestrian zones. Requirements in the design and testing for type, marking and
quality control”
30. Series of standards BDS EN 295 “Stoneware pipes, fittings and pipe connections
for sewage systems”.
31. Series of standards BDS EN 588 “Fibre cement pipes for sewage systems”.
32. Series of standards BDS EN 1123-1 “Pipes and fittings for hot zinc steel pipes
with lateral weld, with angled end and flange, for sewage systems”
33. Series of standards BDS EN 1124-1 “Pipes and fittings for corrosion-proof steel
pipes with lateral weld, with angled end and flange, for waste water systems”
34. BDS EN 1433 “Drainage channels for transport and pedestrian zones.
Classification, requirements for design and testing, marking and compliance assessment.”
35. BDS EN 1916 “Concrete pipes and fittings made from unstrengthened concrete,
concrete with steel threads and strengthened concrete.”
36. BDS EN 1917 “Inspection shafts and inspection aperture made from
unstrengthened concrete, concrete with steel threads and strengthened concrete.”
37. BDS EN 12380 “Air valves for sewage systems. Requirements, testing methods
and compliance assessment.”
38. BDS EN 13101 “Steps for the entrances to underground shafts. Requirements,
marking, testing methods and compliance assessment.”
39. BDS EN 14396 “Fixed steps for shafts”.
Notes:
1. This list is for information only. It has been created in order to provide participants
in investment planning and construction with information about current standards for the
planning, construction and technical operation of sewage systems.
2. The standards quoted in this appendix may be changed and it is recommended that
the latest versions be used.
3. The list of standards was prepared as of the date when this instruction was approved
and should not be considered final, especially with regard to the products and devices
envisaged to be inserted in sewage systems.
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Appendix 6
Article 11(1) and (2)
Modelling methods for the hydraulic measuring of gravity sewage networks
1. Methods for the modelling of rainfall can be classified in the following three basic
groups:
1.1. Simplified (empirical) methods
In these methods the sewage flow is considered even and stationary. In the case of a
complete profile speed can be used to calculate drainage time. These methods are used
predominantly to establish the maximum quantity of surface rain water from water collection
areas up to 200 ha or a drainage time of up to 15 min., in the conditions of constant rain
intensity. The rational method (extreme intensity method) is related to empirical methods, in
accordance with Appendix 1(1).
1.2 Hydrological methods (kinematic wave methods)
In these methods, in addition to even and stationary sewage flow, uneven stationary
flow can be simulated and they can also take into account the delaying and accumulating
function of the sewage network, but not of reverse sewage flows caused by the occurrence of
hydraulic overloading of the sewage network. The methods area suitable for the planning of
large sewage networks, for the assessment of the hydraulic capacity (not including hydraulic
overloading) of existing sewage networks or when simulating the action of a sewage network
during a long period of intense rain fall over an extended period.
1.3 Hydrodynamic methods (dynamic wave methods)
These methods can be used to simulate uneven, non-stationary sewage flow, even in
conditions of overloading and surge. These methods can be used to record both the retention
and accumulating function of the sewage network, as well as the reverse sewage flows caused
by the occurrence of hydraulic over-loading of the sewage network as a result of overfilling
and surge. Thus they can be used when assessing the condition of the sewage networks with
regard to the conditions and frequency of their overfilling and flooding.
In the hydrological and hydrodynamic methods the surface rain flow can be modelled
in a simplified way (S) or detailed (D) The applicability of the methods is given in the
following table:
Application
Simplified
(empirical)
Planning of sewage networks for urbanized
S
territories, including water collection areas up to
200 ha
a
Planning of sewage networks for urbanized
territories, including water collection areas over
200 ha
Hydraulic simplified street sewage networks
S
a
Assessment of action in the event of flooding
a
Assessment of existing sewage networks
a
Planning of exhaust/overflow valves
a
Effect upon the quality of the water collector
a
Effect upon the volume of the water collector
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Methods
Hydrological
methods
S
Hydrodynamic
methods
S
S or D
-
S or D
S or D
S or D
S or D
S or D
a
S or D
S or D
S
S
b
a
Real time system monitoring
Notes:
S is a hydrological process assessed in a simplified way;
D – hydrological process, assessed in a detailed way;
a means that it is not applicable;
b
means that it is not normally recommended.
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S or D
S or D
Appendix 7
to Article 14(1) and
Article 135
Trench widths in the construction of sewage conduits
In the planning of sewage networks constructed in trenches, the width of the trench is
determined in accordance with Table 1 depending on the nominal diameter of the pipeline and
the depth of the trench.
Nominal diameter
DN
mm
Trench width (OD + x + 2*b)
Unstrengthened trench
Trench wall incline
Trench wall incline
Width of strengthened
angle in relation to
angle in relation to
º
trench
horizon ß > 60
horizon ß ≤ 60º
m
≤ 225
OD + 1.00 +2*b
OD + 1.00
> 225 to ≤ 350
OD + 1.10 +2*b
OD + 1.10
OD + 1.00
> 350 to ≤ 700
OD + 1.20 +2*b
OD + 1.20
OD + 1.00
> 700 to ≤ 1 200
OD + 1.30 + 2*b
OD + 1.30
OD + 1.00
> 1 200
OD + 1.40 + 2*b
OD + 1.40
OD + 1.00
OD is the external diameter of the pipelines, m;
X is the clear distance between the wall of the pipe and the trench walls in the case of an unstrengthened
trench or between the pipeline and the strengthening system in the case of a strengthened trench.
b is the thickness of the strengthening system.
Notes:
1. The thickness of the strengthening system (b) for one wall is considered to be 0.l5 m
to 0.30 m. If technical and economic grounds are given, other thicknesses of strengthening
system are permitted.
2. If technical and economic grounds are given, then clear distances other than those
indicated in the table are permissible, but they should be no less than those indicated in EN
476 “General requirements for elements used in pipeline and sewage systems”.
3. In the case of a bottom depth (external diameter) of the pipeline greater than:
- 4 metres, the total sum of clear distances is increased by 0.20 m:
- 5 metres, the total sum of clear distances is increased by 0.40 m:
- 6 metres, the total sum of clear distances is determined in accordance with the
plan.
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Figure 1
Incline angle in the case of an unstrengthened trench wall
Appendix 8
To Article 20(3)
Admissible speeds in gravity sewage networks
1. The admissible minimum speeds for the hydraulic measurement of gravity sewage
networks are given in the following table:
Pipe
diameter
mm
Minimum
speed, m/s
From
DN150 to
DN250
From
DN300 to
DN400
From
DN450 to
DN500
From
DN600 to
DN800
From
DN900 to
DN1200
From
DN1200 to
DN1500
Above
DN1500
0.70
0.80
0.90
0.95
1.00
1.05
1.10
*
In the case of pipes with a non-round cross-section, the minimum speed is considered
to be that shown in the table, equivalent to the conductivity of a pipe with a round cross
section.
2. The admissible maximum speeds of the waste water pipelines and channels are as
follows:
a) in the case of domestic waste water – 4 m/s;
b) in the case of rain and mixed waste water – 7 m/s.
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Appendix 9
to
Article 39(2)
Measurement of retention tanks in gravity sewage networks
1. The working volume of holding tanks is calculated by means of contemporary
measurement methodology and software products, accepted and applicable in world practice.
2. The volume of the holding tanks (Vt) in m3 is calculated on the basis of the
following general formula:
V p  Qop .t от .K p ,
In which:
Qmeas. is the measured water quantity for the cross section of the sewage network
directly before the retention tank, m3/min;
Tdrain – the time required for waste water to drain from the most distant point of the
water collection area to the cross section under examination of the sewage network directly
before the retention tank, min;
Kt – tank coefficient.
3. The tank coefficient Kt is calculated for the standard form of hydrograph with
accepted ratings with regard to the measured cross section of the sewage network directly
before the retention tank and depending on the accepted water volume discharged by the tank
during rainfall in the section after it Qt.
A standard hydrograph is that which gives the maximum possible volume of the
retention tank with accepted ratings.
4. When there is no other data available, the coefficient of the tank Kt can be
calculated in accordance with the following table, given values for the period of single
overload (P) and chosen ratio of α= Qt/Qmt:
Values of
coefficient
  Q p / Qop
0.5
1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.01
0.68
0.50
0.36
0.25
0.16
0.10
0.04
0.01
1.16
0.74
0.51
0.36
0.25
0.16
0.09
0.04
0.01
Single overload Period P
2
5
1.28
0.78
0.53
0.37
0.25
0.16
0.09
0.04
0.01
1.40
0.82
0.55
0.38
0.25
0.16
0.09
0.04
0.01
10
15
1.46
0.84
0.56
0.38
0.25
0.16
0.09
0.04
0.01
1.49
0.85
0.56
0.38
0.26
0.16
0.09
0.04
0.01
Note: Values of coefficient of tank Kt are related to a linear hydrograph with a
standard trapezoid form.
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Appendix 10
to Article 81(1)
Determination of hydraulic capacity of waste water purification plants
1. The average daily water volume Qav. day in m3/d is calculated in accordance with
the following formula:
Qav. day. = QRWW, av. da.+ Qind., av. day +. Q infiltration,
In which:
is the average daily volume of residential waste water as determined in
accordance with Article 16, m3/d;
Qind., av. day - the average daily volume of industrial waste water which is discharged into
the municipal sewage system, calculated on the basis of industrial data, m3/d;
Q infiltration., - the water volume as a result of external and/or infiltrated waters in the
sewage system, calculated in accordance with Article 17, m3/d.
QRWW, av. day
2. Maximum hourly water volume (Qmaxh) in m3/h is calculated on the basis of the
formula:
Qmaxh = QRWW, maxh+ Qind., maxh+ Qinfiltrat.,
In which:
is the maximum hourly volume of residential waste water determined in
accordance with Article 16, m3/h;
Qind, maxh – the maximum hourly volume of industrial waste water which is discharged
into the sewage system, determined on the basis of industrial data, m3/h;
Qinfilt, maxh – the volume of infiltrated waters during the hours with a maximum hourly
drainage, m3/h.
QRWW, maxh
3. The minimum hourly water volume (Qminh) in m3/h is calculated on the basis of the
formula:
Qminh = QRWW, minh+ Qind, minh+ Qinfiltrat.,
In which:
QRWW, minh is the minimum hourly volume of residential waste water determined in
accordance with Article 16, m3/h;
Qind, minh – the minimum hourly volume of industrial waste water which is discharged
into the sewage system, determined on the basis of industrial data, m3/h;
Qinfilt, minh – the volume of infiltrated waters during the hours with a maximum hourly
drainage, m3/h.
4. Measurement water volumes (Qmeas)
a) for grills, sand tanks, secondary precipitators and disinfection facilities:
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Qmeas = 2(QRWW, maxh+ Qind, maxh);
b) for primary precipitators, biological and physiochemical cleaning:
Qmeas= Qmaxh.
5. Additional requirements for the calculation of measurement water volumes in a
mixed and/or combined sewage system:
a) in the case of primary precipitators a reduction of efficiency is permitted during rain
fall;
b) distribution and collection channels, conduits and pipelines are measured for
Qmeas, wherein their conductivity capability in increased by 20 %;
c) the operation of facilities for biological and/or physiochemical cleaning is examined
for the hydraulic conductivity of the water volume during rain fall.
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Appendix 11
to Article 81(2)
Calculation of equivalent number of residents
1. The recommended values of specific daily loads for basic pollutants are given in the
following table:
No,
per
row
1.
2.
3.
4.
5.
Parameter
BOD5
COD
HB
Ngeneral (as per Keldal)
Pgeneral
Raw waste water
60
120
70
11
1.8 ÷ 2.5
After primary precipitation with
a precipitation time of
Qdry.2h.max
0.5 to 1.0 h
1.5 to 2.0 h
45
40
90
80
35
25
10
10
1.6 ÷ 2.2
1.6 ÷ 2.2
The volume of specific daily loads of the basic pollutants from visitors and/or resident
population inhabiting regions not served by sewage systems is deemed to be 33 % of those
indicated in the above table.
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Appendix 12
to Article 118(2)
Frequency of air and temperature in industrial premises in waste water purification
plants
No,
Name of facilities or premises
per
row
1. Sewage pumping stations (machine
room) for the re-pumping of:
- Residential and similar industrial
waste water and sediments;
- Aggressive or explosive industrial
waste water.
Air
temperature
°С
Frequency of air exchange
h
5
Depending on the calculated
heat creation, but no less than
3
5
In the event of possible
creation of explosive or
poisonous vapours or gases,
an additional emergency
ventilation system shall be
designed to provide for an
eight-fold exchange of air per
hour.
The
emergency
induction ventilation system
shall operate automatically
by means of gas analysers
and shall be fitted with a
sound and light warning
system.
2.
Feed tanks and premises fitted with
grills in pumping stations for the
purposes of re-pumping:
- Residential and similar industrial
waste water and sediments
- Aggressive or explosive industrial
waste water.
5
5
5
In the event of possible
creation of explosive or
poisonous vapours or gases,
an additional emergency
ventilation system shall be
designed to provide for an
eight-fold exchange of air per
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3.
Air blowing stations
5
4.
5.
Buildings fitted with grills
Biofilters in buildings
5
5
6.
Methane tanks
- Pumping station;
hour.
The
emergency
induction ventilation system
shall operate automatically
by means of gas analysers
and shall be fitted with a
sound and light warning
system.
Depending on the calculated
heat creation
5
Depending on the calculated
humidity creation
5
12
Eight-fold
emergency
ventilation (if required)
- Gas ejection and collection plants
7.
Mechanical flood drainage plant
8.
Reagent values for preparation of
solutions of:
9.
5
5
- ferric chloride, ammonium sulphate,
caustic soda, chlorine;
16
6
- lime, superphosphate, ammonium
nitrate,
sodium
carbonate,
polyacrylamide
Reagent plants for dosages of ready
solutions stored in enclosed vessels:
16
3
5
5
- lime, superphosphate, ammonium
nitrate,
sodium
carbonate,
polyacrylamide
Stores for:
5
3
- sodium bisulphite, ferric chloride,
ammonium sulphate, caustic soda,
chlorine;
5
6
ferric
chloride,
aluminium
ammonium sulphate, caustic soda,
chlorine
10.
12
In the event of humidity
creation and heat creation
with harmful and dangerous
emissions (if required)
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- superphosphate, ammonium nitrate,
sodium carbonate, polyacrylamide.
5
5
Notes:
1. The heating and ventilation of buildings and facilities in purification plants
operating at normal operating conditions shall be planned in compliance with the legislative
requirements for the planning of heating, ventilation and climate control installations.
2. In pumping stations and machine rooms for re-pumping residential and similar
waste water and sediment, air induction shall be carried out in the low zone.
3. In pumping stations where there is a possibility of explosive or poisonous vapours
and gases, an additional emergency inducted ventilation system shall be installed to ensure an
eight-fold exchange of air per hour. The emergency inducted ventilation shall operate
automatically by means of gas analysers, whereupon a sound and light warning system shall
operate.
4. In the case of rooms where there are no servicing personnel, the ventilation must
provide a temperature in the summer no more than 5 °C higher than the outside temperature,
and in winter heated season — no lower than 5 °C than the outside temperature. When the
rooms are envisaged for service personnel, the room temperature shall be determined in
accordance with the legislative requirements.
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Appendix 13
to Article 152(1)
Testing of sewage pipes with air
1.
The duration of testing of sewage pipelines depends on the nominal diameter of
the pipelines and test methods (LA, LB, LC and LD).
2.
Suitable hermetically sealed devices must be used for testing.
3.
When testing pipes with large nominal diameters, special safety measures must
be taken.
4.
For the first 5 minutes a pressure 10 % higher than the required test pressure ро
is maintained, after which it is adjusted in accordance with the test pressure given in the table,
depending on the test method.
5.
When the measured fall in pressure after the duration of the test is less than the
value of ∆р, as given in the table, the pipe is deemed to comply with the requirements.
6.
The devices used to test the fall in pressure must allow for measurement with
an accuracy of 10 % of ∆р.
Time measurement must be precisely 5 s.
7. Testing of inspection shafts and inspection apertures can be tested with air for a
length of time equal to half that for a pipe with a diameter equivalent to the diameter of the
inspection shaft, or correspondingly the inspection aperture.
Material
Non-wet
concrete pipes
Wet concrete
pipes and all
other materials
Testing
method
LA
LB
LC
LD
LA
LB
LC
LD
Testing
pressure,
Fall in
pressure
∆р, kPa
DN
100
1
5
10
20
1
5
10
20
0.25
1
1.5
1.5
0.25
1
1.5
1.5
5
4
3
1.5
5
4
3
1.5
DN
200
Test length L, min
DN
DN
DN
300
400
600
DN
800
5
4
3
1.5
5
4
3
1.5
5
4
3
1.5
7
6
4
2
14
11
8
4
19
15
11
5
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7
6
4
2
10
7
5
2.5
11
8
6
3
14
11
8
4
DN
1 00
0
18
14
10
5
24
19
14
7
Appendix 14
to Article 152(1)
Testing of sewage pipelines with water
1. The test pressure is attained by filling the test section from the crown of the pipe to
ground level. The maximum admissible pressure is 50 kPa, and the minimum – 10 kPa
In the case of pipelines which are designed to be in operation under constant or
temporary increased pressure, higher test pressures may be determined.
2. After the pipelines and/or inspection shafts have been filled with water and the
required test pressure has been applied, the pressure is maintained for about one hour.
2.1 The pressure shall be maintained within the limits of ±1 kPa in relation to the test
pressure established when filled with water.
2.2 In order to maintain the required pressure within the limits indicated, water shall
be added.
2.3 The volume of added water, as well as the pressure height at required pressure
shall be measured and recorded.
3. The test requirements are considered fulfilled when the volume of added water is no
less than:
a) 0.15 15 l/m2 over a period of 30 min – for pipelines;
b) 0.20 l/m2 over a period of 30 min – for pipelines, including inspection shafts;
c) 0.40 l/m2 over a period of 30 min – for inspection shafts and inspection apertures.
The surface area in m2 refers to the wet inner surface.
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