SANITARY DRAINAGE SYSTEM
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Individual Vents - the individual venting technique is defined as the
installation of a vent pipe for every trap or trapped fixture.
- design a system to dispose of the sanitary waste and wastewater.
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It is the easiest method of ensuring the preservation of a trap seal
Wastewater - sometimes referred to as sewage, is used water. It comes from
but the most costly because of the number of vent pipes required
almost all sections of the building, including bathrooms, kitchens, and laundry
in the venting system.
areas, and in commercial projects, equipment being serviced.
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Common Vents - The common venting method serves two fixtures located
on the same floor; it is essentially an individual vent that serves no more
One of the primary objectives of the sanitary drainage system is to dispose
of decaying wastes rapidly, before they cause objectionable odors or become
than two traps or trapped fixtures.
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hazardous to health.
venting for all of the fixtures of one or two bathroom groups that are located
on the same floor.
Conventional sanitary drainage and vent
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- Sometimes referred to as the drain, waste, and vent (DWV) system, is a network
of pipes that remove wastewater from a building.
Wet Vents - The wet venting method uses a single vent pipe to provide
Circuit Vents - A circuit venting system is a horizontal venting pipe serving
up to eight fixtures.
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Combination Drain and Vent - system allows the distance from trap to
vent to be extended infinitely, provided the drain stays in the horizontal
Gravity - is the driving force behind wastewater flow, so the sanitary drainage
orientation and there is a vent somewhere within the horizontal branch.
system is known as a gravity system.
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Relief Vent - is a continuous pipe of lesser or equal diameter running
Vent system - introduces and circulates air in the system to maintain atmospheric
parallel and alongside the soil and waste stack in a multistory plumbing
pressure in the drain lines and ensure adequate gravity flow of wastewater.
system.
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Chief Components of Sanitary Drainage and Vent System
Vent Stack extends vertically through the building and up
through the roof to the exterior of the building.
Trap - U-shaped pipe that catches and holds a small quantity of wastewater that
is poured down a fixture drain.
Air Admittance Valve (AAV) - is a pressure-activated, one-way mechanical
venting port used to eliminate the need for expensive venting and roof penetration.
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Integral Trap is built in as part of the fixture.
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Floor drains which are used to take away the water after washing
floors.
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Positive Air Pressure Attenuator (PAPA) - - is a product developed to protect
buildings of 10 or more stories against the unwanted positive pressures generated
in the DWV system.
Building Trap was located at the end of the building drain.
Interceptors – are passive devices designed into a plumbing system that trap,
separate, and retain these toxic or undesirable substances from wastewater before
Sovent® Drain and Vent System - The Sovent® system is a system that
combines the drain stack, branches, and vents into one pipe system by using
patented Sovent® fittings.
it is discharged into the sewer line.
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Sewage Ejection - wastewater must be lifted to the level of the main drain or
Grease interceptor - can solidify and coat the inner walls
sewer by a pumping system.
of pipes, creating a stoppage.
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- sewage ejector system consists of the sump basin, a motor-
Oil-sand interceptor - separate and remove floatable
material (oils) and settleable materials (sands and metals)
pump assembly, and a system of automatic electrical controls.
from wastewater before it is discharged to the municipal
sewer system.
Fixture Branches - each plumbing fixture is connected horizontally to the
DRAIN AND VENT PIPE DESIGN
sanitary drainage system by a drain line.
Drainage Fixture Units
Stacks – soil stack, the fixture branches feed into a vertical pipe.
- The draining rate for plumbing fixtures is based upon the drainage fixture unit
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When the stack will carry all wastes except human waste, it is
referred to as a waste stack.
(DFU).
- The minimum pipe diameter is based on the total connected DFU.
Building Drain - The soil or waste stacks feed into a main horizontal pipe.
Building Sewer - is an extension of the building drain that carries wastewater
WASTEWATER TREATMENT STANDARDS
from the building drain to a community sanitary sewer main or an individual onsite sewage treatment (OSST) system. Also known as House or Building
Connection, or Sanitary Sewer Lateral.
- Wastewater and Sewage are used interchangeably, sewage technically contains
waste products or excrement from human beings or animals and wastewater may
not.
Sanitary Sewer Main - is a pipe through which the wastewater flows as it is
conveyed from a building to the wastewater treatment plant.
Gray water - is wastewater that typically contains the residues of washing
processes.
Cleanouts - are screw-type fittings with a cap that can unscrew to allow access to
gray water reuse systems that safely recycle household gray water for
the inside of the sanitary drain pipes.
reuse in toilets or for irrigation to conserve water and reduce the flow to treatment
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Floor cleanouts (FCO) are found in horizontally positioned
systems.
building drain or sewer lines that are installed in the floor or in
the ground.
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Wall cleanouts (WCO) are placed in vertically positioned
Black water - is wastewater that contains fecal matter and urine. It is produced in
water closets (toilets), urinals, and bidets.
stacks. All cleanouts in vertical stacks should be located no
Commercial wastewater - is nontoxic, nonhazardous wastewater from
higher than 48 in (1.2 m) above the floor.
commercial and institutional food service operations and beauty salons
Venting - Vents are pipes that introduce sufficient air into the drainage system to
Industrial wastewater - is process and non-process wastewater from
reduce air turbulence (from siphoning or back pressure) and to release sewer gases
manufacturing, commercial, laboratory, and mining operations.
to the outside
Wastewater Constituents
Types of Venting Methods
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- The wastewater constituents of most concern are those that have the
potential to cause disease or detrimental environmental effects.
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because it remains in the water after the treatment.
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Organisms - Many different types of organisms live in wastewater and some
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to break down certain carbon-based (organic) pollutants in wastewater.
Corrosion Removal - to balance the pH (acidity) of the treated
water to prevent corrosion damage to pipes, remove odors, and
Pathogens - Many disease-causing viruses, parasites, and bacteria are
improve taste; and to soften the water.
present in wastewater.
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Aeration - the exposure of treated water to air, which removes
odors and improves taste.
are essential contributors to treatment. Bacteria, protozoa, and worms work
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Chlorination - has become the standard method of disinfection
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Organic Matter - Organic materials that originate from plants, animals, or
Softening Process - removes calcium and magnesium that have
dissolved in water, making the hard water soft.
synthetic organic compounds are found everywhere in the environment.
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Oil and Grease - Bacteria do not quickly break down fatty organic materials
ON-SITE INDIVIDUAL SEWAGE TREATMENT
from animals, vegetables, and petroleum.
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Inorganics - Inorganic minerals, metals, and compounds, such as sodium,
potassium, calcium, magnesium, cadmium, copper, lead, nickel, and zinc,
- Individual sewage treatment systems are used in areas not served by a
are common in wastewater from both residential and nonresidential sources.
community wastewater treatment plant.
Nutrients - Wastewater often contains large amounts of the nutrients
nitrogen and phosphorus, which promote plant growth.
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Solids - Solid materials in wastewater can consist of organic or inorganic
materials and organisms.
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On-Site Sewage Treatment
Gases - Many gases in wastewater can cause odors or are dangerous. For
- traditionally called septic systems, usually consist of the building sewer, which
leads from the building into a septic tank and then into a distribution box that feeds
the fluid (effluent) into a drainage field or disposal field
Primary treatment component
example, methane gas, a by-product of anaerobic biological treatment, is
highly combustible.
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Septic tank
Primary disposal component
Other Important Wastewater Characteristics
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Temperature - The best temperatures for wastewater treatment range from
77° to 95°F.
Drainage field
Effluent - , anaerobic and aerobic bacteria convert the wastes into minerals, gases,
and a liquid waste.
pH - The acidity or alkalinity of wastewater affects both treatment and the
environment.
Clarified effluent - leaves the septic tank and flows in a pipe to a drainage field.
Flow - Whether a system serves a single residence or an entire community,
it must be able to handle fluctuations in the quantity and quality of
wastewater it receives to ensure proper continuous treatment.
Primary Treatment Equipment - Wastewater from a building is first treated in
primary treatment equipment such as tanks or filters.
Types of primary treatment equipment
COMMUNITY WASTEWATER TREATMENT AND DISPOSAL
Septic Tank - is a watertight, covered container designed to settle out
Wastewater Removal
and hold solid wastes and partially treat wastewater with beneficial
- Community Wastewater Treatment and Disposal System, a network of
bacteria.
pipes that transport wastewater to treatment plants where it is treated and
released to the environment.
Aerobic Tanks - are a substitute for a septic tank. They consist of a
trash tank, an aeration chamber, and a settling chamber.
Storm water mains - are similar in design to sanitary sewers except that
they have a much larger diameter.
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Force Mains - Certain types of sewers, such as inverted siphons
clarified effluent before it flows into a drainage field. Wastewater is
and pipes from pumping stations, flow under pressure.
first treated in an aerobic or septic tank.
Urban Sewer Mains - generally discharge into interceptor sewers that join
to form a large trunk line, which discharges wastewater into the community
sewage treatment plant where it is treated.
Sewage treatment - multistage process designed to restore the quality of
wastewater before it reenters a body of water such as a stream, river, or lake.
Processes in large wastewater treatment plants
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Pump Tank - is a watertight container used to temporarily store
Sand Filter - is a lined, impermeable container containing a bed of
granular material that provides additional treatment of effluent as it
flows from the primary treatment tank to the drainage field.
Trash/Grease Tank - occasionally used in conjunction with an
aerobic tank.
Cesspool - is a covered underground container that receives untreated
Preliminary Wastewater Treatment - Preliminary treatment to screen out,
sewage directly from a building and discharges it into soil.
grind up, or separate debris is the first step in wastewater treatment.
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Primary Wastewater Treatment - Primary treatment is the second step in
High-Level Alarm - is used to alert the homeowner or building
wastewater treatment. It separates suspended solids and greases from
operator if liquid inside a tank reaches a level that is higher than it
wastewater.
would be if the pump were operating normally.
Secondary Wastewater Treatment - Secondary treatment is a biological
treatment process to remove dissolved organic matter from wastewater.
Sewage microorganisms are cultivated and added to the wastewater.
- drainage field provides secondary treatment and is the final disposal
Three approaches are used to accomplish secondary treatment:
location for clarified effluent from wastewater
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Fixed film systems - grow microorganisms on substrates such as
rocks, sand, or plastic.
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Types of primary treatment equipment
Suspended film systems - stir and suspend microorganisms in
Absorption Drainage Field - consists of rows (called lines) of
wastewater.
underground pipes through which the clarified effluent passes.
Lagoon systems - are shallow basins that hold the wastewater
for several months to allow for the natural degradation of sewage.
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Secondary Treatment and Disposal Equipment
Final Treatment (Disinfection) - Final treatment involves disinfection; the
removal of disease causing organisms from wastewater.
Gravel-Less Drain Field - distributes effluent into the soils through
gravel-less drain pipe instead of gravel.
Evapotranspiration (ET) Bed or Evapotranspiration Trench
Drainage Field - treats wastewater by evaporating the water from the
soil and by transpiring the water into the air through plants and
Membrane Filter-technique provides a direct count of colonies
Grasses.
trapped and then cultured.
Low-Pressure Dosing (LPD) Drainage Fields - typically consist of
Multiple tube fermentation method-provides an estimate of the
narrowly cut 6 to 12 in wide trenches, containing small-diameter PVC
most probable number (MPN) per 100 milliliters from the number of
dispersion pipes.
test tubes in which gas bubbles form after incubation.
Absorption Mounds - consist of septic tank(s), a pump tank, effluent
pump and controls, and an above-grade drainage system.
Spray Distribution - systems spray the disinfected effluent onto the
ground surface in a manner similar to a lawn irrigation system.
Leaching Chambers - are proprietary, commercially produced plastic
chambers pre-molded into a dome shape.
Subsurface Drip - systems consist of a septic tank, a pump tank, a
filtering device, and a drip distribution system. An aerobic tank is
typically used for the primary treatment process.
Seepage Pit - is a deep underground container that receives clarified
effluent from a septic tank.
GENERAL REGULATIONS
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Typically, an OSST system should not be installed, repaired, or
rehabilitated where a community sanitary sewer system is available or
where a local ordinance requires connection to a community system.
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OSST system is generally not permitted when a building site is located
within 200 ft from any community sewer.
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It is illegal to discharge any wastewater from OSST systems (except
under a governmental permit) to any ditch, stream, pond, lake,
waterway, or drain tile, or to the surface of the ground.
TESTING FOR SOIL AND WATER FOR DRAINAGE
Soil- is an important part of an OSST system because it treats and disposes
of the septic tank effluent.
Soil evaluation- is an assessment of subsurface soil conditions at a specific
site that is conducted under the supervision of a professional engineer or
professional geologist.
Limiting layer- may be an impervious soil layer, bedrock, or a high-water
table.
Soil percolation test-is a subsurface soil test at a depth of a proposed
absorption system to determine the water absorption capability of the soil.
Percolation Test- is conducted by boring a series of test holes at the site
under consideration and observing water seepage rates in holes placed
throughout the intended area of the drainage field.
PERCOLATION TEST PROCEDURES
1.
Number and location
2.
Results
3.
Type of hole
4.
Preparation
5.
Procedure of presoaking
a.
Initial presoak
b.
Final presoak
6.
Determination of measurement interval
7.
Measurement
BOD TEST- measures the amount of dissolved oxygen organisms are likely to
need to degrade wastes in wastewater.
COLIFORM TEST- determines whether wastewater has been adequately treated
and whether water quality is suitable for drinking and recreation.
Coliform bacteria- are used as indicator organisms for the presence
of other, more serious pathogens.
TWO METHODS FOR DETERMINING THE PRESENCE
AND DENSITY OF COLIFORM BACTERIA