Imhoff Ta Tank nk The Imhoff tank was developed to correct the two main defects of the septic tank. 1. It prevents prevents the solids solids once once removed removed from the the sewage from from again being being mixed mixed with with it, but but still provides for the decomposition of these solids in the same unit 2. It provide providess an effluent effluent amenabl amenablee to further further treatment 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 the uppe upperr secti section on or sedim sedimen entat tatio ion n com compa partm rtment ent
2.
the the lower lower secti section on kno known wn as the the dig digest estio ion n compa compartm rtmen entt and and
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the the gas gas vent ent and and scum scum sect sectio ion n
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. "eriodically 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. #olids settle to the bottom of this sloped compartment, slide down and pass through an opening opening or slot to the digestion compartment. $ne of the bottom slopes extends at least six inches beyond beyond the slot. This forms a trap to prevent gas or digesting 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. %ttention should, however, however, be given given to the following
1
a.
&aily removal of grease, scum and floating solids from the sedimentation compartment.
b.
'eekly scraping of the sides and sloping bottoms of the sedimentation compartment by a rubber s(ueegee to remove adhering solids which may decompose.
c.
'eekly cleaning the slot at the bottom of the sedimentation compartment. This can be done by use of a chain drag.
d.
"eriodic 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.
)emoval of sludge should be done before the sludge depth approaches within 1* inches of the slot in the sedimentation compartment. It is better to remove small amounts fre(uently than large amounts at long intervals. #ludge 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 li(uid held in storage above the digested sludge to be withdrawn from the tank. -efore winter temperatures are expected, most of the digested sludge except that necessary for seeding +about 2 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.
%fter 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.
"revention of /0oaming/. very effort should be made to prevent /foaming/ because correction after the condition arises is sometimes difficult. /0oaming/ 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 p value of the resulting sludge and lime mixture in the digestion compartment should not exceed 3.4.
2.
)emoving the tank from service where possible for a few days and allowing it to rest will sometimes improve conditions.
!.
%gitation 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 5 to 4 percent and a -$& reduction of 16 to !6 percent. The two7story design re(uires a deep over7all tank. "rimary 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 6, or less, and a greater degree of treatment is not needed. 2
3
1.
Imhoff tank
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Imhoff tank The Imhoff tank , named for German engineer 9arl Imhoff +1*34:1;46, 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 re(uires separate biogas vents and pipes for the removal of digested sludge, typically after 47; months of digestion. The Imhoff tank is in effect a two7story septic tank and retains the septic tank
Primary Treatment
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"rimary treatment is designed to remove organic and inorganic solids by the physical processes of sedimentation and flotation. "rimary treatment devices reduce the velocity and disperse the flow of wastewater. In primary treatment the velocity of flow is reduced to 1 to 2 feet per minute to maintain a (uiescent condition so that the material denser than water will settle out and material less dense than water will float to the surface. %pproximately 5 to 4 percent of the suspended solids are removed from the waste stream +26 7 !6? -$& reduction. The solids that remain in suspension as well as dissolved solids will usually be biochemically treated in subse(uent processes for physical separation and removal in the final +secondary settling tanks. The si@e and number of primary tanks is dependent on the estimated wastewater flow and the design detention time. Aenerally, a detention time of 2 to ! hours will provide a sufficient time period for most particles to settle out. 0urther, 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 si@e and shape of the solid and the temperature of the water. 'ater is more dense at lower temperaturesB therefore, the re(uired settling time increases. %s the temperatures of the water increases, the re(uired settling time decreases. (ual distribution of flow throughout the tank is critical. The greater the velocity in one area, the less the actual detention time. #olids not having sufficient time to settle out will be discharged in the effluent. "rinciple 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 !4 hours. &uring 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 re(uire a minimum of attention which involves an annual inspection and the periodic +! 7 6 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.
2.
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 It provides an effluent amenable to further treatment.
5
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
!.
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. "eriodically 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. #olids settle to the bottom of this sloped compartment, slide down and pass through an opening or slot to the digestion compartment. $ne 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. %ttention should, however, be given to the following a.
&aily removal of grease, scum and floating solids from the sedimentation compartment.
b.
'eekly scraping of the sides and sloping bottoms of the sedimentation compartment by a rubber s(ueegee to remove adhering solids which may decompose.
6
c.
d.
'eekly cleaning the slot at the bottom of the sedimentation compartment. This can be done by use of a chain drag. "eriodic 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.
)emoval of sludge should be done before the sludge depth approaches within 1* inches of the slot in the sedimentation compartment. It is better to remove small amounts fre(uently than large amounts at long intervals. #ludge 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 li(uid held in storage above the digested sludge to be withdrawn from the tank. -efore winter temperatures are expected, most of the digested sludge except that necessary for seeding +about 2 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.
%fter 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.
"revention of /0oaming/. very effort should be made to prevent /foaming/ because correction after the condition arises is sometimes difficult. /0oaming/ 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 p value of the resulting sludge and lime mixture in the digestion compartment should not exceed 3.4.
2.
)emoving the tank from service where possible for a few days and allowing it to rest will sometimes improve conditions.
!.
%gitation 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 5 to 4 percent and a -$& reduction of 16 to !6 percent. The two7story design re(uires a deep over7all tank. "rimary 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 6, or less, and a greater degree of treatment is not needed.
Mechanically-Cleaned Plain Sedimentation Tanks
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"hoto Credit irginia &epartment of ealth
These tanks may be rectangular, circular or s(uare, but all operate on the same principle of collecting the settled solids by slow7moving scrapers to the point of removal. In the rectangular tanks the wastewater enters at one end and flows hori@ontally 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. %t 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 hori@ontally to the periphery. The circular tanks have scraper arms attached to a central motor7driven 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. #kimmer 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 maDor difference is that the rigid arms of the scraper mechanism are e(uipped 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 e(uipment 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 e(uipment damage. #olids 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 (uality. The sludge removal schedule must be worked out for each plant by observations and tests, keeping in mind that the obDective is to remove sludge at the proper rate, at the proper rate, at the proper concentration and with the proper (uality 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. #easonal revision of this schedule will probably be necessary. In addition, scum and grease
8
should be removed daily from the tank surface.
% conscientious operator is aware that mechanical e(uipment re(uires attention and maintenance. Inspection, cleaning, lubrication, sampling, testing and record keeping are important aspects of any maintenance program.
"hoto Credit irginia &epartment of ealth
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 e(uipment manufacturer.
Physical Oser!ations
"hysical 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 re(uired operational control necessary to achieve optimum unit efficiency and subse(uent plant performance. These results should be confirmed through laboratory testing. $bservations which should be made daily and the results recorded 1.
0loating solids accumulations should be noted, if present, whether existing as clumps or as a dispersed accumulation
2.
The formation of gas bubbles
!.
The absence or presence of odors
5.
&istribution of flow to multiple tanks
6.
&istribution of flow over weirs
4.
Eoss of solids in the effluent
$ther factors that should occasionally be checked are elevation and placement baffles. "aoratory Control
9
valuation of primary treatment is dependent on laboratory analysis. The fre(uency of testing and the /range/ of test results will vary from plant to plant. 'aste stream characteristics, environmental conditions and in7plant operation will affect the test data at each facility. Eaboratory tests commonly associated with primary tanks are shown below.
Parameter
Type of Sample
-$&
Composite
#uspended #olids
Composite
#ettleable #olids
Arab
p
Arab
Temperature
Arab
"ocation Influent ffluent Influent ffluent Influent ffluent Influent ffluent Influent
Comparison of influent versus effluent test results provides information re(uired to calculate and evaluate clarifier efficiency.
Operational Prolems If visual observations, confirmed by lab analysis indicate poor clarifier operation, then the problem source must be identified so that corrective andFor preventive action can be taken. #ome common problems and discussed below. %.
#loating Sludge
Cause: #ludge decomposing in tank and floating to surface. Prevention and Cure: )emove sludge more completely or more fre(uently by one or more of the following methods.
1.
$perate mechanical scrapers for longer periods or more often.
2.
)eplace broken or warped wooden flightsB or adDust flights closer to the bottom.
!.
-.
)emove sludge from hoppers more completely by pumping or gravity withdrawal for longer periods or at slower rates. 'here sludge clings to inclined surfaces, remove by scraping or Detting.
Contents $lack and Odorous
Cause: #eptic wastewater or strong digester recycled supernatant. Prevention and Cure For septic wastewater:
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1.
Correct flow obstructions in the collection systemB
2.
Godify, pretreat, reduce, or eliminate organic wastes, such as cannery, milk processing, brewery, tannery, and organic textiles wastesB
!.
"re7Chlorinate in the sewer systemB or ahead of sedimentation tank to reduce decomposition of wastewaterB this is particularly effective when time of travel in sewer is unusually long or wastewater temperatures are high, or when certain industrial wastes are presentB
5.
"reaerate wastes of types listed in Ho. 2 aboveB or
6.
Improve flow of wastewater system to reduce accumulations of solids.
0or strong recycled digester supernatant 1. Correct or improve sludge digestion to produce improved (uality supernatantB 2. )educe rate of withdrawal of supernatant to sedimentation tankB !. #elect better (uality supernatant from another @one or delay withdrawal until (uality improves, if that is possible. 5. ntil (uality improves, discharge part or all of supernatant to other points such as lagoon, sludge drying bed, or aeration tank until (uality improves. 6. "resettle the supernatant. C. %&cessi!e Sedimentation in Inlet Channels Cause: elocity too low for cross7sectional area of channel at existing flow rates. Prevention and Cure:
1. )educe cross7sectional area. 2. %gitate with air, water, or other means to prevent deposits. &. %&cessi!e #ouling of Surfaces and 'eirs (ith 'aste(ater Solids or )ro(ths Cause: %ccumulation of wastewater solids and resultant plant growth. Prevention and Cure:
1. Gore fre(uent and thorough scrubbing of all surfaces in contact with wastewater. . Intermittent Surging of #lo( Cause: igh intermittent pumping rates. Prevention and Cure:
1.
%dDust controls for pump se(uence, pump combinations, and automatic cut7in and cutoff water surface levels to maintain pumping rates close to rates of inflow. 11
0. $roken Scraper Chains and #requent Shear Pin #ailure Cause: xcessive load on mechanical scraper. Prevention and Cure:
1. "eriodically empty tank and examine all metal parts for defects and wearB 2. )eplace defective and worn parts, particularly hinge pins, chain links, and wear shoes, and badly worn, broken, or warped scrapers +flightsB !. Install grit chamber or otherwise reduce entrance of grit to the primary tanks if grit accumulation is evidentB or 5. $perate collector mechanism for longer period andFor pump sludge more often. A. Sludge *ard to +emo!e from *opper Cause:
1. igh content of grit, clay, or other heavy compacted materialB or 2. 'ithdrawal lines too small. Prevention and Cure:
1. )educe grit content by installing or modifying grit chamber, or locate and correct sources of grit entering the wastewater systemB 2. Eoosen compacted material manually or by pressure Detting with air or water hoseB !. -ack7flush clogged pipelinesB 5. "ump sludge more fre(uentlyB or 6. Godify sludge piping
Solids Accumulation 1. 0ollowing 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 (uality of the tank effluent. #econdary solids are usually less dense and secondary effluents are normally of a higher (uality 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. 0re(uency of solids removal is dependent on sludge (uality as well as the design of the related sludge wasting e(uipment devices. 12
!. 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 andFor pumped to be disposed of separately or with the settled solids. Clarifier %fficiency
1. To calculate the efficiency of any treatment unit it is necessary to measure influent and effluent parameters. 0re(uently, the determination of unit efficiency is appraised in terms of -$& 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 fficiencies 1. Eisted below are some range values for primary clarifier efficiencies
-iochemical $xygen &emand #ettleable #olids #uspended #olids Total #olids
+emo!al %fficiency 26? 7 !6? ;? 7 ;6? 5? 7 4? 1? 7 16?
2. Clarifier efficiencies vary depending on influent flow rate and wastewater characteristics as well as in7plant conditions. The most important structural elements effecting clarifier efficiency are inlet flow distribution and effluent weir placement. %lthough effluent weir configurations are often beyond the control of the operator, there are some minor alterations that can be made to improve the influent flow patterns so that the affect of short7circuiting is minimi@ed. These remedial alterations would include the installation of target baffles or the installation or relocation of a maDor flow baffle.
!eir "#erflo$ %ate 1. $utlet weirs vary greatly in design. They provide for uniformed removal of clarifier effluent from the surface of the tank.
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&'oto Credit( )ir*inia +epartment of ,ealt' 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. Gost designers recommend 1, to 2, gallons per day per linear foot of weir.
!. ven more important than overflow rate is the proper location of the weir launders so that upflow velocities are minimi@ed.
+etention 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. &etention periods should be in the 2 7 ! hour range.
2. The /%ctual/ &etention Time in a clarifier is a better indicator of process capabilities, since it is a direct measure of the short7circuiting flow patterns in that unit. xperience 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 Settlin* %ate 1. This is expressed as gallons per s(uare foot of tank area based on wastewater flow per day. The range value for primary tanks varies from 6 7 36 gpdFs(.ft. This is an important factor directly affecting the settleable solids and removal efficiency.
Chemical Treatment 14
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 re(uire a higher degree of treatment than primary units can achieve, but secondary treatment is not warrantedB +! 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 re(uirements. 'e 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 non7 settleable suspended solids and settles more readily. The precipitating chemical also dissociates or ioni@es in the wastewater and neutrali@es 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. % chemical treatment plant usually has the following features 1. "reliminary &evices 7 screens, grit chambers, etc. 2. Chemical 0eeders !. 0lash Gixing nits 5. 0locculation Tanks 6. #edimentation Tanks such as have already been described 4. Increased 0acilities for the Treatment and &isposal of #ludge
Chemical #eeders
% large variety of units to feed chemicals, either dry or in solution, in controlled amounts, are made by a number of manufacturers.
Mi&ing ,nits
The chemicals, when added to sewage, must be thoroughly and (uickly 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. #uch mixing devices are made by a number of manufacturers. 15
#locculators
%fter the chemical is mixed with sewage it is gently agitated for 16 to ! minutes to foster the coagulation of particles. If -$& reduction is desired, the agitation time may be increased to 56 minutes. The colloidal and suspended solids meet and adhere together in large flocculant masses which settle readily in the sedimentation tank. &ifferent types of e(uipment 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.
%fficiency
Chemical treatment can effect a reduction up to ; percent in suspended solids and up to 3 percent in the -$&. 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. $perational costs are high due to increase in operator
"essons Inde&
0or lessons 4 : 2, answer the ven number &iscussion and )eview (uestions in your textbooks, 'astewater Treatment "lant $perations ols. I and II. "lease note that there are no &iscussion and )eview (uestions for Chapter 1; but your assignment for this chapter is to write a Gonthly )eport. )efer to page 435 ol. II, as a reference. 'hen you have completed the assignment for each chapter, email, mail or fax them assignment to your instructor.
"esson 1 "esson "esson / "esson 0 "esson "esson 2 "esson 3
'astewater Treatment %ctivated #ludge "rocess J 0oodFGicroorganism )atio #lime Arowth "rocesses +Trickling 0ilter J )-C %erobic and %naerobic &igestion 'astewater Treatment "onds 'astewater 'astewater Treatment Gethods and &isposal
16
"esson 4 "reliminary Treatment "esson 5 "rimary Treatment "esson 16 #econdary Treatment "esson 11 &isinfection of 'astewater "esson 1 #olids andling and &isposal "esson 1/ %dvanced 'astewater Treatment "esson 10 #ampling and Testing "rocedures "esson 1 'astewater "esson 12 #ludge from a #ewage Treatment "lant as a 0easible #ource of nergy "esson 13 xtended %eration %ctivated #ludge "lant "esson 14 #afety "rotocols for #ewer Cameras
KThis information was obtained from the New York Water Operations
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