Imhoff Tank
The Imhoff tank was developed to correct the two main defects of the septic tank.
1. It prevents the solids once removed from the sewage from again being mixed with it, but
still provides for the decomposition of these solids in the same unit
2. It provides an effluent amenable to further treatment.
Contact between the waste stream and the anaerobic digesting sludge is practically eliminated
and the holding period in primary settling compartment at the tank is reduced. The Imhoff tank
may be either circular or rectangular and is divided into three compartments:
1. the upper section or sedimentation compartment
2. the lower section known as the digestion compartment and
3. the gas vent and scum section
It is desirable to be able to reverse the direction of flow to prevent excessive deposition of solids
at one end of the sedimentation compartment. Periodically reversing the flow will result in an
even accumulation of sludge across the bottom of the tank. In operation, all of the wastewater
flows through the upper compartment. Solids settle to the bottom of this sloped compartment,
slide down and pass through an opening or slot to the digestion compartment. One of the bottom
slopes extends at least six inches beyond the slot. This forms a trap to prevent gas or digesting
sludge particles in the lower section from entering the waste stream in the upper section. The
gas and any rising sludge particles are diverted to the gas vent and scum section.
Imhoff Tank Operation
There are no mechanical parts in an Imhoff tank. Attention should, however, be given to the
following:
a. Daily removal of grease, scum and floating solids from the sedimentation compartment.
1
b. Weekly scraping of the sides and sloping bottoms of the sedimentation compartment by a
rubber squeegee to remove adhering solids which may decompose.
c. Weekly cleaning the slot at the bottom of the sedimentation compartment. This can be
done by use of a chain drag.
d. Periodic reversal of flow where provided for in the design of the tank.
e. Control of the scum in the scum chamber, by breaking it up, hosing with water under
pressure, keeping it wet with supernatant from the digestion compartment and removal if
the depth approaches two to three feet.
f. Removal of sludge should be done before the sludge depth approaches within 18 inches of
the slot in the sedimentation compartment. It is better to remove small amounts frequently
than large amounts at long intervals. Sludge should be removed at a slow regular rate to
avoid coning (i.e. the formation of a channel through the sludge) which would permit
partially digested sludge and liquid held in storage above the digested sludge to be
withdrawn from the tank. Before winter temperatures are expected, most of the digested
sludge except that necessary for seeding (about 20 percent) should be removed to provide
space for winter accumulations when digestion is very slow. The height of the sludge in
the sludge compartment should be determined at inlet and outlet end of the tank at least
once a month.
g. After each time that sludge is removed, the sludge pipes should be flushed and drained to
prevent sludge from hardening in and clogging the pipes.
h. Prevention of "Foaming". Every effort should be made to prevent "foaming" because
correction after the condition arises is sometimes difficult. "Foaming" is usually
associated with an acid condition of the sludge and in such cases may be prevented or
corrected by treatment with lime or sodium bicarbonate to counteract the acidity of the
sludge. There are a few simple measures which may, under certain circumstances, remedy
or improve the condition.
1. The use of hydrated lime or sodium bicarbonate added to the gas vents will usually aid
in correction. The pH value of the resulting sludge and lime mixture in the digestion
compartment should not exceed 7.6.
2. Removing the tank from service where possible for a few days and allowing it to rest
will sometimes improve conditions.
3. Agitation of the gas vent area with a water hose or paddles will sometimes help.
The Imhoff tank has no mechanical parts and is relatively easy and economical to operate. It
provides sedimentation and sludge digestion in one unit and should produce a satisfactory
primary effluent with a suspended solids removal of 40 to 60 percent and a BOD reduction of 15
to 35 percent. The two-story design requires a deep over-all tank. Primary tanks with separate
digesters have largely replaced the Imhoff tank for large municipal installations. The Imhoff
tanks is best suited to small municipalities and large institutions where the tributary population is
5,000 or less, and a greater degree of treatment is not needed.
2
1. Imhoff tank
From Wikipedia, the free encyclopedia
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Imhoff tank
The Imhoff tank, named for German engineer Karl Imhoff (1876–1965), is a chamber suitable
for the reception and processing of sewage. It may be used for the clarification of sewage by
simple settling and sedimentation, along with anaerobic digestion of the extracted sludge. It
consists of an upper chamber in which sedimentation takes place, from which collected solids
slide down inclined bottom slopes to an entrance into a lower chamber in which the sludge is
collected and digested. The two chambers are otherwise unconnected, with sewage flowing only
through the upper sedimentation chamber and no flow of sewage in the lower digestion chamber.
The lower chamber requires separate biogas vents and pipes for the removal of digested sludge,
typically after 6-9 months of digestion. The Imhoff tank is in effect a two-story septic tank and
retains the septic tank's simplicity while eliminating many of its drawbacks, which largely result
from the mixing of fresh sewage and septic sludge in the same chamber.
Imhoff tanks are being superseded in sewage treatment by plain sedimentation tanks using
mechanical methods for continuously collecting the sludge, which is moved to separate digestion
tanks. This arrangement permits both improved sedimentation results and better temperature
control in the digestion process, leading to a more rapid and complete digestion of the sludge.
A test for settleable solids in water, wastewater and stormwater uses an Imhoff cone, with or
without stopcock. The volume of solids is measured after a specified time period at the bottom
of a one-liter cone using graduated markings. [1]
Primary Treatment
Primary treatment is designed to remove organic and inorganic solids by the physical processes
of sedimentation and flotation. Primary treatment devices reduce the velocity and disperse the
3
flow of wastewater. In primary treatment the velocity of flow is reduced to 1 to 2 feet per
minute to maintain a quiescent condition so that the material denser than water will settle out and
material less dense than water will float to the surface. Approximately 40 to 60 percent of the
suspended solids are removed from the waste stream (25 - 35% BOD reduction). The solids that
remain in suspension as well as dissolved solids will usually be biochemically treated in
subsequent processes for physical separation and removal in the final (secondary) settling tanks.
The size and number of primary tanks is dependent on the estimated wastewater flow and the
design detention time. Generally, a detention time of 2 to 3 hours will provide a sufficient time
period for most particles to settle out. Further, the settling rate of a particle depends on the
strength and freshness of the wastewater being treated, the weight of the solid compared to the
specific gravity of water, the size and shape of the solid and the temperature of the water. Water
is more dense at lower temperatures; therefore, the required settling time increases. As the
temperatures of the water increases, the required settling time decreases. Equal distribution of
flow throughout the tank is critical. The greater the velocity in one area, the less the actual
detention time. Solids not having sufficient time to settle out will be discharged in the effluent.
Principle primary treatment devices are referred to as sedimentation tanks, primary tanks,
primary clarifiers or primary settling tanks, some of which have the further function of providing
an additional compartment for the decomposition of settled organic solids which is known as
sludge digestion. There are several types of primary tanks in use.
Septic Tanks
The septic tank was one of the earliest treatment devices developed. Currently, septic tanks
provide wastewater treatment for small populations, such as individual residences, small
institutions, schools, etc.
They are designed to hold wastewater at low velocity, under anaerobic conditions for minimum
detention time of 36 hours. During this period, a high removal of settleable solids is achieved.
These solids decompose in the bottom of the tank with the formation of gas which, entrained in
the solids, causes them to rise through the wastewater to the surface and lie as a scum layer until
the gas has escaped, after which the solids settle again. This continual flotation and resettling of
solids carries some of them in a current toward the outlet to be discharged with the effluent. The
final effluent disposal occurs by subsurface methods. The effectiveness of this method is
dependent on the leaching ability of the soil.
These primary type units require a minimum of attention which involves an annual inspection
and the periodic (3 - 5 years) removal of sludge and scum accumulations.
Imhoff Tank
The Imhoff tank was developed to correct the two main defects of the septic tank.
1. It prevents the solids once removed from the sewage from again being mixed with it, but
still provides for the decomposition of these solids in the same unit
2. It provides an effluent amenable to further treatment.
4
Contact between the waste stream and the anaerobic digesting sludge is practically eliminated
and the holding period in primary settling compartment at the tank is reduced. The Imhoff tank
may be either circular or rectangular and is divided into three compartments:
1. the upper section or sedimentation compartment
2. the lower section known as the digestion compartment and
3. the gas vent and scum section
It is desirable to be able to reverse the direction of flow to prevent excessive deposition of solids
at one end of the sedimentation compartment. Periodically reversing the flow will result in an
even accumulation of sludge across the bottom of the tank. In operation, all of the wastewater
flows through the upper compartment. Solids settle to the bottom of this sloped compartment,
slide down and pass through an opening or slot to the digestion compartment. One of the bottom
slopes extends at least six inches beyond the slot. This forms a trap to prevent gas or digesting
sludge particles in the lower section from entering the waste stream in the upper section. The
gas and any rising sludge particles are diverted to the gas vent and scum section.
Imhoff Tank Operation
There are no mechanical parts in an Imhoff tank. Attention should, however, be given to the
following:
a. Daily removal of grease, scum and floating solids from the sedimentation compartment.
b. Weekly scraping of the sides and sloping bottoms of the sedimentation compartment by a
rubber squeegee to remove adhering solids which may decompose.
c. Weekly cleaning the slot at the bottom of the sedimentation compartment. This can be
done by use of a chain drag.
d. Periodic reversal of flow where provided for in the design of the tank.
e. Control of the scum in the scum chamber, by breaking it up, hosing with water under
pressure, keeping it wet with supernatant from the digestion compartment and removal if
the depth approaches two to three feet.
5
f. Removal of sludge should be done before the sludge depth approaches within 18 inches of
the slot in the sedimentation compartment. It is better to remove small amounts frequently
than large amounts at long intervals. Sludge should be removed at a slow regular rate to
avoid coning (i.e. the formation of a channel through the sludge) which would permit
partially digested sludge and liquid held in storage above the digested sludge to be
withdrawn from the tank. Before winter temperatures are expected, most of the digested
sludge except that necessary for seeding (about 20 percent) should be removed to provide
space for winter accumulations when digestion is very slow. The height of the sludge in
the sludge compartment should be determined at inlet and outlet end of the tank at least
once a month.
g. After each time that sludge is removed, the sludge pipes should be flushed and drained to
prevent sludge from hardening in and clogging the pipes.
h. Prevention of "Foaming". Every effort should be made to prevent "foaming" because
correction after the condition arises is sometimes difficult. "Foaming" is usually
associated with an acid condition of the sludge and in such cases may be prevented or
corrected by treatment with lime or sodium bicarbonate to counteract the acidity of the
sludge. There are a few simple measures which may, under certain circumstances, remedy
or improve the condition.
1. The use of hydrated lime or sodium bicarbonate added to the gas vents will usually aid
in correction. The pH value of the resulting sludge and lime mixture in the digestion
compartment should not exceed 7.6.
2. Removing the tank from service where possible for a few days and allowing it to rest
will sometimes improve conditions.
3. Agitation of the gas vent area with a water hose or paddles will sometimes help.
The Imhoff tank has no mechanical parts and is relatively easy and economical to operate. It
provides sedimentation and sludge digestion in one unit and should produce a satisfactory
primary effluent with a suspended solids removal of 40 to 60 percent and a BOD reduction of 15
to 35 percent. The two-story design requires a deep over-all tank. Primary tanks with separate
digesters have largely replaced the Imhoff tank for large municipal installations. The Imhoff
tanks is best suited to small municipalities and large institutions where the tributary population is
5,000 or less, and a greater degree of treatment is not needed.
Mechanically-Cleaned Plain Sedimentation Tanks
Photo Credit: Virginia Department of Health
These tanks may be rectangular, circular or square, but all operate on the same principle of
collecting the settled solids by slow-moving scrapers to the point of removal.
6
In the rectangular tanks the wastewater enters at one end and flows horizontally to the other
end. The scrapers (flights) are attached by their ends to two parallel chains which pass over
sprockets. The flights move slowly along the tank floor, pushing the settled solids to a sludge
hopper at the end of the tank. At the same time, the partially submerged flights, in their return
path, push the floating solids, grease and oils (scum) to a trough at the end of tank.
In the centerfeed circular tanks the wastewater enters at the center and flows radially and
generally horizontally to the periphery. The circular tanks have scraper arms attached to a
central motor-driven shaft. The bottom of the tanks are sloped toward the center and the
scrapers move the settled solids to a sludge hopper at the center. Skimmer arms, if present, are
attached tot he central shaft at the surface for the collection of floating solids, grease and oils
(scum).
In square tanks, the wastewater enters at the center and flows to the four sides. The scraper
mechanism is similar to that in the circular tanks. The major difference is that the rigid arms of
the scraper mechanism are equipped with pivoted corner blades which reach out into the four
corners of the tank and move the solids in these areas to the path of the circular mechanism.
Operation
Collection and removal of sludge from the sedimentation tank, as well as correct maintenance
procedures, are important factors in successful plant operation. The mechanical collection
equipment can be run intermittently but is most often run on a continual basis. This prevents the
excess accumulation of solids on the tank bottom and reduces the load on the collector
mechanisms and thereby helps to prevent equipment damage. Solids left in the tank bottom too
long will gasify and rise to the surface, therefore, sludge should be removed from the tank as
often as necessary. This, in turn, is dependent on waste stream characteristics, volume of flow
and sludge quality. The sludge removal schedule must be worked out for each plant by
observations and tests, keeping in mind that the objective is to remove sludge at the proper rate,
at the proper rate, at the proper concentration and with the proper quality for the receiving
process unit. Concentrating the sludge reduces the volume of water being pumped and
contributes to pumping efficiency. There are, however, pump design limitations to consider.
Seasonal revision of this schedule will probably be necessary. In addition, scum and grease
should be removed daily from the tank surface.
7
A conscientious operator is aware that
mechanical equipment requires
attention and maintenance.
Inspection, cleaning, lubrication,
sampling, testing and record keeping
are important aspects of any
maintenance program.
Photo Credit: Virginia Department of Health
The proper time schedules for preventive and corrective maintenance must be determined at
each wastewater facility. The best rule is to follow the instruction manual provided by the
equipment manufacturer.
Physical Observations
Physical observations at the water surface of each clarifier can provide the operator with
valuable information regarding clarifier efficiency and related plant status. The observed data
can dictate the required operational control necessary to achieve optimum unit efficiency and
subsequent plant performance. These results should be confirmed through laboratory testing.
Observations which should be made daily and the results recorded:
1. Floating solids accumulations should be noted, if present, whether existing as clumps or as
a dispersed accumulation
2. The formation of gas bubbles
3. The absence or presence of odors
4. Distribution of flow to multiple tanks
5. Distribution of flow over weirs
6. Loss of solids in the effluent
Other factors that should occasionally be checked are elevation and placement baffles.
Laboratory Control
Evaluation of primary treatment is dependent on laboratory analysis. The frequency of testing
and the "range" of test results will vary from plant to plant. Waste stream characteristics,
environmental conditions and in-plant operation will affect the test data at each facility.
Laboratory tests commonly associated with primary tanks are shown below.
8
Parameter
Type of Sample
BOD
Composite
Suspended Solids
Composite
Settleable Solids
Grab
pH
Grab
Temperature
Grab
Location
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Comparison of influent versus effluent test results provides information required to calculate and
evaluate clarifier efficiency.
Operational Problems
If visual observations, confirmed by lab analysis indicate poor clarifier operation, then the
problem source must be identified so that corrective and/or preventive action can be taken.
Some common problems and discussed below.
A. Floating Sludge
Cause: Sludge decomposing in tank and floating to surface.
Prevention and Cure: Remove sludge more completely or more frequently by one or more of
the following methods.
1. Operate mechanical scrapers for longer periods or more often.
2. Replace broken or warped wooden flights; or adjust flights closer to the bottom.
3. Remove sludge from hoppers more completely by pumping or gravity withdrawal for longer
periods or at slower rates. Where sludge clings to inclined surfaces, remove by scraping or
jetting.
B. Contents Black and Odorous
Cause: Septic wastewater or strong digester recycled supernatant.
Prevention and Cure For septic wastewater:
1. Correct flow obstructions in the collection system;
2. Modify, pretreat, reduce, or eliminate organic wastes, such as cannery, milk processing,
brewery, tannery, and organic textiles wastes;
3. Pre-Chlorinate in the sewer system; or ahead of sedimentation tank to reduce
decomposition of wastewater; this is particularly effective when time of travel in sewer is
unusually long or wastewater temperatures are high, or when certain industrial wastes are
present;
4. Preaerate wastes of types listed in No. 2 above; or
5. Improve flow of wastewater system to reduce accumulations of solids.
9
For strong recycled digester supernatant:
1. Correct or improve sludge digestion to produce improved quality supernatant;
2. Reduce rate of withdrawal of supernatant to sedimentation tank;
3. Select better quality supernatant from another zone or delay withdrawal until quality
improves, if that is possible.
4. Until quality improves, discharge part or all of supernatant to other points such as lagoon,
sludge drying bed, or aeration tank until quality improves.
5. Presettle the supernatant.
C. Excessive Sedimentation in Inlet Channels
Cause: Velocity too low for cross-sectional area of channel at existing flow rates.
Prevention and Cure:
1. Reduce cross-sectional area.
2. Agitate with air, water, or other means to prevent deposits.
D. Excessive Fouling of Surfaces and Weirs with Wastewater Solids or Growths
Cause: Accumulation of wastewater solids and resultant plant growth.
Prevention and Cure:
1. More frequent and thorough scrubbing of all surfaces in contact with wastewater.
E. Intermittent Surging of Flow
Cause: High intermittent pumping rates.
Prevention and Cure:
1. Adjust controls for pump sequence, pump combinations, and automatic cut-in and cutoff
water surface levels to maintain pumping rates close to rates of inflow.
F. Broken Scraper Chains and Frequent Shear Pin Failure
Cause: Excessive load on mechanical scraper.
Prevention and Cure:
1. Periodically empty tank and examine all metal parts for defects and wear;
2. Replace defective and worn parts, particularly hinge pins, chain links, and wear shoes, and
badly worn, broken, or warped scrapers (flights);
3. Install grit chamber or otherwise reduce entrance of grit to the primary tanks if grit
accumulation is evident; or
4. Operate collector mechanism for longer period and/or pump sludge more often.
G. Sludge Hard to Remove from Hopper
Cause:
1. High content of grit, clay, or other heavy compacted material; or
2. Withdrawal lines too small.
10
Prevention and Cure:
1. Reduce grit content by installing or modifying grit chamber, or locate and correct sources of
grit entering the wastewater system;
2. Loosen compacted material manually or by pressure jetting with air or water hose;
3. Back-flush clogged pipelines;
4. Pump sludge more frequently; or
5. Modify sludge piping
Solids Accumulation
1. Following biological treatment (and), as an integral part of the secondary treatment
process, is the secondary clarifier. The primary and secondary clarifier differ as to
physical location and to the density of the solids handled, as well as in the quality of the
tank effluent. Secondary solids are usually less dense and secondary effluents are
normally of a higher quality than those of primary clarifiers.
2. In both the primary and secondary clarifiers, the sludge (settled solids) is scraped or
drawn to a hopper or sump for removal, treatment and disposal. The sludge removal can
occur separately and independently in each unit, or the sludge from the secondary
clarifier can be pumped to the primary clarifier or to a separate thickener unit and mixed
with the primary sludge. This combination of primary clarifier sludge and secondary
clarifier sludge is collectively referred to as waste sludge and will usually undergo further
treatment for ultimate disposal. Frequency of solids removal is dependent on sludge
quality as well as the design of the related sludge wasting equipment devices.
3. The actual sludge removal and disposal system (for the various types of clarifiers) varies
from plant to plant. In addition, the floatable solids must be skimmed and/or pumped to
be disposed of separately or with the settled solids.
Clarifier Efficiency
1. To calculate the efficiency of any treatment unit it is necessary to measure influent and
effluent parameters. Frequently, the determination of unit efficiency is appraised in
terms of BOD and suspended solids removal.
2. The operator should also be aware that recycled loadings from digesters, vacuum filters,
etc. can impose severe organic and suspended solids loadings on primary clarifiers. The
strength and volume of these recycled waste streams must be added to the influent
wastewater loadings in order to properly calculate unit process efficiencies.
Typical Clarifier Efficiencies
1. Listed below are some range values for primary clarifier efficiencies:
11
Biochemical Oxygen Demand
Settleable Solids
Suspended Solids
Total Solids
Removal Efficiency
25% - 35%
90% - 95%
40% - 60%
10% - 15%
2. Clarifier efficiencies vary depending on influent flow rate and wastewater characteristics
as well as in-plant conditions. The most important structural elements effecting clarifier
efficiency are inlet flow distribution and effluent weir placement. Although effluent weir
configurations are often beyond the control of the operator, there are some minor
alterations that can be made to improve the influent flow patterns so that the affect of
short-circuiting is minimized. These remedial alterations would include the installation
of target baffles or the installation or relocation of a major flow baffle.
Weir Overflow Rate
1. Outlet weirs vary greatly in design. They provide for uniformed removal of clarifier
effluent from the surface of the tank.
Photo Credit: Virginia Department of Health
1. The term "weir overflow rate" is used to express the number of gallons of wastewater that
flow over one linear foot of weir per day.
2. Most designers recommend 10,000 to 20,000 gallons per day per linear foot of weir.
3. Even more important than overflow rate is the proper location of the weir launders so that
upflow velocities are minimized.
Detention Time
1. This the time, expressed in hours, that wastewater is held in a tank based on wastewater
flow and tank volume. (This assumes total displacement and uniform flow through the
tank). Detention periods should be in the 2 - 3 hour range.
12
2. The "Actual" Detention Time in a clarifier is a better indicator of process capabilities,
since it is a direct measure of the short-circuiting flow patterns in that unit. Experience
has shown that the use of a fluorescein dye, introduced as an instantaneous slug at the
influent to the unit and then measured in the unit effluent over a period of several hours,
is the best measure of the actual detention time.
Surface Settling Rate
1. This is expressed as gallons per square foot of tank area based on wastewater flow per
day. The range value for primary tanks varies from 500 - 750 gpd/sq.ft. This is an
important factor directly affecting the settleable solids and removal efficiency.
Chemical Treatment
Chemical treatment is included under primary treatment because it involves chemical and
physical processes as distinct from the biological processes which are the basis of secondary
treatment. Chemical addition has application: (1) in the treatment of industrial wastes which
are sometimes difficult to decompose by biological means, (2) where discharge to receiving
waters require a higher degree of treatment than primary units can achieve, but secondary
treatment is not warranted; (3) after secondary treatment when a higher degree of treatment is
demanded (often referred to as tertiary treatment).
The exact point of chemical application is dependent on design considerations as well as permit
requirements. We are concerned, here, with chemical treatment and its application to primary
treatment.
Chemical treatment involves the addition of one or more chemicals to wastewater to produce
floc, which is an insoluble chemical compound that adsorbs colloidal matter, enmeshes nonsettleable suspended solids and settles more readily. The precipitating chemical also dissociates
or ionizes in the wastewater and neutralizes the electric charges held by colloidal particles
causing them to coagulate to form larger readily settleable solids. The chemicals most widely
used are aluminum sulfate (alum), ferric chloride, lime and polymers.
A chemical treatment plant usually has the following features:
1.
2.
3.
4.
5.
6.
Preliminary Devices - screens, grit chambers, etc.
Chemical Feeders
Flash Mixing Units
Flocculation Tanks
Sedimentation Tanks such as have already been described
Increased Facilities for the Treatment and Disposal of Sludge
13
Chemical Feeders
A large variety of units to feed chemicals, either dry or in solution, in controlled amounts, are
made by a number of manufacturers.
Mixing Units
The chemicals, when added to sewage, must be thoroughly and quickly mixed with it to provide
complete and uniform reactions. This is accomplished by violent agitation for a short period of
time either by mechanical or hydraulic methods. This agitation is carried on in special tanks, in
sections of other tanks, or in the piping system. Such mixing devices are made by a number of
manufacturers.
Flocculators
After the chemical is mixed with sewage it is gently agitated for 15 to 30 minutes to foster the
coagulation of particles. If BOD reduction is desired, the agitation time may be increased to 45
minutes. The colloidal and suspended solids meet and adhere together in large flocculant masses
which settle readily in the sedimentation tank. Different types of equipment to accomplish this
purpose are made by a number of manufacturers and must be designed to operate at varying
speeds as determined by the actual process characteristics.
Sludge
The volume of sludge obtained by chemical treatment is greater than with standard primary
treatment, necessitating a comparable increase in the capacity of the sludge handling facilities
and in the cost of sludge treatment and disposal.
Efficiency
Chemical treatment can effect a reduction up to 90 percent in suspended solids and up to 70
percent in the BOD. It is well adapted to intermittent operation and has value in sewage
treatment to reduce pollution of streams during periods of low flow or to lessen pollution of
bathing beaches and recreational waters during months when these facilities are in use. It is of
value also for the treatment of sewage containing high concentrations of industrial wastes which
will inhibit biological life and interfere with secondary treatment processes. Operational costs
are high due to increase in operator's time, chemical usage and the quantities of sludge to be
treated and disposed of.
Lessons Index
14
For lessons 6 – 20, answer the Even number Discussion and Review questions in your textbooks,
Wastewater Treatment Plant Operations Vols. I and II. Please note that there are no Discussion
and Review questions for Chapter 19 but your assignment for this chapter is to write a Monthly
Report. Refer to page 674 Vol. II, as a reference. When you have completed the assignment for
each chapter, email, mail or fax them assignment to your instructor.
Lesson 1: Wastewater Treatment
Lesson 2: Activated Sludge Process & Food/Microorganism Ratio
Lesson 3: Slime Growth Processes (Trickling Filter & RBC)
Lesson 4: Aerobic and Anaerobic Digestion
Lesson 5: Wastewater Treatment Ponds
Lesson 6: Wastewater
Lesson 7: Wastewater Treatment Methods and Disposal
Lesson 8: Preliminary Treatment
Lesson 9: Primary Treatment
Lesson 10: Secondary Treatment
Lesson 11: Disinfection of Wastewater
Lesson 12: Solids Handling and Disposal
Lesson 13: Advanced Wastewater Treatment
Lesson 14: Sampling and Testing Procedures
Lesson 15: Wastewater
Lesson 16: Sludge from a Sewage Treatment Plant as a Feasible Source of Energy
Lesson 17: Extended Aeration Activated Sludge Plant
Lesson 18: Safety Protocols for Sewer Cameras
*This information was obtained from the New York Water Operations
15