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ENGINEER MANUAL EM 1110-3-162 April 1984 ENGINEERING AND DESIGN Water Supply, Water Treatment Mobilization Construction DEPARTMENT OF THE ARMY CORPS OF ENGINEERS OFFICE OF THE CHIEF OF ENGINEERS

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Page 1: WaterSupply, Water Treatment Mobilization Constructionasktop.net/wp/download/26/EM 1110-3-162 Water Supply Water Treatment.pdf · provided. Pressure differential devices of the Venturi

ENGINEER MANUAL EM 1110-3-162April 1984

ENGINEERING AND DESIGN

Water Supply, Water Treatment

Mobilization Construction

DEPARTMENT OF THE ARMYCORPS OF ENGINEERS

OFFICE OF THE CHIEF OF ENGINEERS

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DEPARTMENT OF THE ARMY

EM 1110-3-162U .S . Army Corps of Engineers

DAEN-ECE-G

Washington, D .C. 20314

Engineer ManualNo . 1110-3-162

9 April 1984

Engineering and DesignWATER SUPPLY, WATER TREATMENT

Mobilization Construction

1 . Purpose . This manual establishes water quality standards and designcriteria for water treatment processes at U .S . Army mobilization facilities .

2 . Applicability. This manual is applicable to all field operatingactivities having mobilization construction responsibilities .

3 .

Discussion .

Criteria and standards presented ~herein apply to constructionconsidered crucial to a mobilization effort . These requirements may bealtered when necessary to satisfy special conditions on the basis of goodengineering practice consistent with the nature of the construction . Designand construction of mobilization facilities must be completed within 180 daysfrom the date notice to proceed is given with the projected life expectancy offive years . Hence, rapid construction of a facility should be reflected inits design. Time-consuming methods and procedures, normally preferred overquicker methods for better quality, should be de-emphasized. Lesser gradematerials should be substituted for higher grade materials when the lessergrade materials would provide satisfactory service and when use of highergrade materials would extend construction time . Work items not immediatelynecessary for the adequate functioning of the facility should be deferreduntil such time as they can be completed without delaying the mobilizationeffort.

FOR THE COMMANDER :

PAUL -F .'

ANAUGHColone , Corps of EngineersChief of Staff

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Engineer ManualNo . 1110-3-162

CHAPTER 1 .

Engineering and DesignWATER SUPPLY, WATER TREATMENTMobilization Construction

CHAPTER 2 .

CHAPTER 3 .

CHAPTER 4 .

DEPARTMENT OF THE ARMY

EM 1110-3-162US Army Corps of EngineersWashington, DC 20314

Paragraph Page

9 April 1984

GENERAL

Purpose and scope . . . . . . . . . 1-1 1-1Consultation with Government

agencies . . . . . . . . . . . . 1-2 1-1Water quality criteria and

standards . . . . . . . . . . . . 1-3 1-1Definitions . . . . . . . . . . . . 1-4 1-1

WATER TREATMENT SYSTEMS

General design criteria . . . . . . 2-1 2-1Plant siting . . . . . . . . . . . 2-2 2-1Process selection and design . . . 2-3 2-2Reliability . . . . . . . . . . . . 2-4 2-2Operating considerations . . . . . 2-5 2-2Plant capacity . . . . . . . . . 2-6 2-2

WATER TREATMENT PROCESSES

Process selection factors . . . . . 3-1 3-1Preliminary treatment processes . . 3-2 3-1Aeration . . . . . . . . . . . . . 3-3 3-3Coagulation and flocculation . . . 3-4 3-4Sedimentation basins . . . . . . . 3-5 3-5Filtration . . . . . . . . . . . . 3-6 3-8Disinfection . . . . . . . . . . . 3-7 3-13Taste and odor control . . . . . . 3-8 3-17Softening . . . . . . . . . . . . . 3-9 3-17Iron and manganese control . . . . 3-10 3-21Corrosion and scale control . . . . 3-11 3-22Special processes . . . . . . . . . 3-12 3-23

MEASUREMENT AND CONTROL

Measurement of process variables . 4-1 4-1Control . . . . . . . . . . . . 4-2 4-1Design of instruments and

controls . . . . . . . . . . . 4-3 4-1

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EM 1110-3-1629 Apr 84

CHAPTER 5 .

WATER TREATMENT CREMICALS

Chemical properties . . . . . . . .

5-1

5-1Chemical standards . . . . . . . .

5-2

5-1Chemical handling; and storage . . .

5-3

5-1Chemical application . . . . . . .

5-4

5-2

CHAPTER 6 .

WATER TREATMENT PLANT WASTES.

Quantities and characteristicsof wastes . . . . . ., . . . . . .

6-1

6-1Waste management . . . . . . . . .

6-2

6-l

APPENDIX A.

DESIGN EXAMPLES

A-1

APPENDIX B .

LABORATORIES AND LABORATORY ANALYSES

1

APPENDIX C.

REFERENCES

C-1

LIST OF FIGURES

Figure 3-1 .

Rectangular sedimentation basin..3-2 .

Circular sedimentation basin .3--3 .

Schematic of rapid sand filter operational controls .3-4 .

Minimum chlorine residuals.A-1 .

Flow schematic - water clarification plant .A-2.

Schematic of iron and manganese removal plant .

Paragraph Page

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CHAPTER 1

GENERAL

EM 1110-3-1629 Apr 84

1-1 . Purpose and scope . This manual, intended for planners and designengineers, presents information on water quality standards and designcriteria for water treatment processes at Army mobilization facilities .This manual also establishes criteria to be followed in determining thenecessity for and the 'extent of treatment, and on procedures applicableto the planning of water treatment projects .

1-2 . Consultation with Government agencies . State health department,state water resource, and U.S . Environmental Protection Agencypersonnel as appropriate, should be consulted in the early stages ofproject planning regarding supply sources and associated watertreatment needs . State agencies have established design guidelinesbased on local conditions and experiences . Information regarding theseguidelines is available from the division of engineering within thestate agency responsible for environmental protection . Consultationwith state engineers will provide valuable information relative toplant design and water treatment experience in the state or region . Itis also advisable to confer with management and operating personnel ofnearby water supply utilities .

1-3 . Water quality criteria and standards . Information on currentcriteria and standards for raw and potable water are presented inTB MED 576 .

1-4 . Definitions . Definitions for water treatment works will be aspresented in EM 1110-3-160 .

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2-1 .' General design criteria .

CHAPTER 2

WATER TREATMENT SYSTEMS

a . Water treatment plants . Water treatment plants at mobilizationfacilities must produce water of sufficient quality and quantity forall intended purposes . If the water is to be used for humanconsumption, it must be free of organisms or substances posing healthhazards at all times. The overall water quality objective can be metif the water delivered to service meets the drinking water standardspresented in TB MED 576 . Typical design examples can be found inappendix A.

b . Water storage and distribution . The quality of water obtainedat the user's tap is not determined solely by water treatmentoperations . Raw water quality and conditions in treated water storageand water distribution systems also affect the quality of tap water .Consequently, protection of raw water quality and finished waterstorage and delivery systems to the maximum practicable extent isessential . Excellence in water treatment is partially nullified unlessother water system components are adequately designed, maintained, andoperated . General considerations on water supplies can be found inEM 1110-3-160 . Information on water sources is contained inEM 1110-3-161 ; on water storage in EM 1110-3-163 ; and on waterdistribution in EM 1110-3-164 .

2-2 . Plant siting . The following items will be considered in choosinga plant site .

- Proximity to the source of raw water .

- Proximity to the area to be served .

- Ability to locate intake upstream of wastewaterdischarges .

Land availability and costs .

Potential for flooding of the site .

Availability and reliability of electric power .

Geology and topography of the site .

Availability of transportation facilities .

Legal obligations or restrictions .

EM 1110-3-1629 Apr 84

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EM 1110- 3-162g Apr 84

2-3 . Process selection and design . The selection and design ofthe water treatment,processes, to be used at a particular facilityare dictated by practicability, reliability, flexibility, and overalleconomics . Engineers experienced in water treatment plant design areneeded to determine the best treatment system for any particularsituation, and their advice should be obtained in the early stages ofproject planning . Detailed information about major treatment processesis given in chapter 3 .

2-4 . Reliability .

a . Duplicates of essential items, including pumps, settling basins,flocculators, filters, and chemical feeders should be provided asappropriate to allow periodic maintenance and repair . The degree ofimportance of each item must be evaluated on a case-by-case basis,considering that safe water has to be supplied at all times . One trainof essential items may be constructed initia

if this would allow thefacility to be operational within the allotted mobilization time .Backup units can be constructed subsequently .

b . Installation of emergency generating facilities at the watertreatment plant will be required if lengthy power outages are probable .Likewise, if the delivery of crucial chemical supplies is uncertain,larger than normal stores of these chemicals must be kept on hand,which would necessitate larger than normal chemical storage areas .

2-5 . Operating considerations . To simplify plant operations, thefollowing guidelines should be observed during the design stage .

a . Eliminate any unnecessary equipment and operations .

b . Locate operations requiring frequent operator attentionreasonably close together . Filters, flocculators, and chemical feedingequipment generally require the most attention .

c . Simplify chemical handling and feeding as much as possible .Unloading and storage areas for chemicals .should be easily maintained,readily accessible, and close to the point of application ofchemicals

d . Design flexibility into plants treating surface water to handleraw water quality changes .

2-6 . Plant capacity . The water treatment plant will be sized totreat sufficient water to meet the requirements given in EM1110-3-160 . Care should betaken not to underestimate specialwater demands .

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CHAPTER 3

WATER TREATMENT PROCESSES

EM 1110- 3-1629 Apr 84

3,-1 . Process selection factors . The design of treatment facilitieswill be determined by considering all engineering, labor, materials,equipment, and energy factors .

3-2 . Preliminary treatment processes .

Surface waters typicallycontain fish and debris which can clog or damage pumps, clog pipes, andcause problems in water treatment . Surface waters may also containhigh concentrations of suspended matter . Preliminary treatment isemployed for removal of debris and part of the suspended materials .

a . Screens .

(1)

Coarse screens or racks .

Coarse _s~reens, often termed barscreens or racks, must be provided to intercept large, suspended orfloating material . Such screens or racks are made of 1/2-inch to3/4-inch metal bars spaced to provide 1 to 3 inch openings .

(2) Fine screens . Surface waters require screens or strainersfor removal of material too small to be intercepted by the coarse rack .These may be basket-type, in-line strainers, manually or hydraulicallycleaned by backwashing, or of the traveling type, which are cleaned bywater jets . Fine-screen, clear openings should be approximately 3/8inch . The velocity of the water in the screen openings should be lessthan 2 fps at maximum design flow through the screen and at minimumscreen submergences which occur at minimum anticipated flows .

(3) Ice clogging . In northern areas, screens may be clogged byfrazil or anchor ice . Exposure of racks or screens to cold air favorsice formation on submerged parts and should be avoided to the maximumpracticable extent . Steam or electric heating, diffusion aeration,,andflow reversal have been used to overcome ice problems .

(4) Disposal of screenings . Project planning must includeprovisions for the disposal of debris removed by coarse and finescreens .

b . Flow measurement . Water treatment processes, such as chemicalapplication, are related to the rate of flow of raw water . Therefore,it is essential that accurate flow-rate measurement equipment isprovided . Pressure differential devices of the Venturi type arecommonly used for measurement of flow in pressure conduits . Analternative selection for pressure conduits is a magnetic flow meter ifthe minimum velocity through the meter will be 5 fps or more . AParshall flume can be used for metering in open channels . Flow signalsfrom the metering device selected should be transmitted to thetreatment plant control center .

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EM 1110- 3-1629 Apr 84

c . Flow division . While not a treatment process, flow division .(flow splitting) is an important treatment plant feature that must beconsidered at an early stage of design . To insure continuity ofoperation during major maintenance, plants are frequently designed withparallel, identical chemical mixing, and sedimentation facilities . Norigid rules can be given for the extent of duplication required becausea multiplicity of factors influence the decision . Normally, aeratorsare not provided in duplicate . Presedimentation basins may not requireduplication if maintenance can be scheduled during periods of.relatively low raw water sediment load or if the following plant unitscan tolerate a temporary sediment overload . If it is determined thatpresedimentation at all times is essential for reliable plantoperation, then the flow division should be made ahead of thepresedimentation basins by means of identical splitting weirs arrangedso that flow over either weir may be stopped when necessary . Duringnormal operation, the weirs would accomplish a precise equal divisionof raw water, regardless of flow rate, to parallel subsequent units :rapid-mix, slow-mix, and sedimentation . The water would then becombined and distributed to the filters . If presedimentation units arenot provided, then the flow is commonly split ahead of the rapid-mixunits . If flow division is deemed necessary, the design should allowflexibility in construction such that at least one system, or train, ofunits can be constructed first .

Duplicate trains can then beconstructed after the first train is in operation .

d . Sand traps . Sand traps are not normally required at surfacewater treatment plants . Their principal application is for the removalof fine sand from well water . The presence of sand in well water isusually a sign of improper well construction or development . If sandpumping cannot be stopped by reworking the well, the sand must beremoved from the well water . Otherwise, it will create seriousproblems in the distribution system by clogging service pipes, meters,and plumbing . Centrifugal sand separators provide an effective meansof sand removal .

e . Plain sedimentation . Plain sedimentation, also termed"presedimentation," is accomplished without the use of coagulatingchemicals . Whether'plain sedimentation is essential is a judgmentdecision influenced by the experience of plants treating water from thesame source . Water derived from lakes or impounding reservoirs rarelyrequires presedimentation treatment . On the other hand, water obtainedfrom notably sediment-laden streams, such as those found in parts ofthe Midwest, require presedimentation facilities for removal of grosssediment load prior to additional treatment . Presedimentationtreatment should receive serious consideration for water obtained fromrivers whose turbidity value frequently exceeds 1,000 units .

(1) Plain sedimentation basins . Plain sedimentation orpresedimentation basins may be square, circular, or rectangular and areequipped with sludge removal mechanisms .

3-2

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EM 1110-3-1629 Apr 8 4

(2) Design criteria . Detention time should be approximately 3hours . Basin depth should be In the approximate range of 10 to 15feet, corresponding to upflow rates of 600 to 900 gpd per square foot .Short-circuiting can be minimized by careful attention to design ofInlet and outlet arrangements . Weir loading rates should not exceedapproximately 20,000 gpd per foot . Where presedimentation treatment Iscontinuously required, duplicate basins should be provided .

3-3 . Aeration . The term "aeration" refers to the processes In whichwater Is brought Into contact with air for the purpose of transferringvolatile substances to or from the water . These volatile substancesInclude oxygen, carbon dioxide, hydrogen sulfide, methane, andunidentified volatile organic compounds responsible for tastes andodor . Aeratlon Is frequently employed at plants designed for Iron andmanganese removal . The oxygen added by aeration oxidizes dissolvedIron and manganese to insoluble forms which can then be removed bysedimentation and filtration .

a . Purposes of aeration . The principal objectives of aeration are :

(1) Addition of oxygen to water for the oxidation of iron,manganese, and hydrogen sulfide and to a limited extent, organicmatter .

(2) Partial removal of substances that may interfere with or addto the cost of water treatment . Examples : Removal of hydrogen sulfideprior to chlorination; removal of carbon dioxide prior to limesoftening .

(3) Reduction of the concentration of taste-and-odor producingsubstances such as hydrogen sulfide, and to a limited extent, volatileorganic compounds .

b . Types of aerators . Three types of aerators are commonlyemployed . These are : (1) waterfall aerators exemplified by spraynozzle, cascade, and multiple-tray units, (2) diffusion or bubbleaerators which involve passage of bubbles of compressed air through thewater, and (3) mechanical aerators employing motor-driven Impellersalone or in combination with air Injection devices . Of the threetypes, waterfall aerators, employing multiple trays, are the mostfrequently used in water treatment . The efficiency of multiple-trayaerators can be increased by the use of enclosures and blowers toprovide counterflow ventilation . The use of diffusion or bubbleaerators will be discouraged because of the complexity of compressedair equipment .

c . Use of aeration . Aeration will be considered only when treatingground water with high levels of dissolved Iron, manganese, hydrogensulfide, or other dissolved gases and volatile organic compounds whichcreate odor or taste problems . Aeration will be considered for the

3-3

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EM 1110-3-1629 Apr 84

removal of carbon dioxide in ground water if lime softening is to beused . A laboratory,test to determine the efficiency of aeration isusually required .

3-4 . Coagulation and flocculation . Coagulation means a reduction inthe forces which tend to keep suspended particles apart . The joiningtogether of small particles into larger, settleable, and filterableparticles is flocculation, . Thus, coagulation precedes flocculation,and the two processes must be considered conjunctively .

a . Purposes of coagulation and flocculation . Raw water supplies,especially surface water supplies, often contain a wide range ofmatter, including minerals, organic substances, and microscopicorganisms ranging in size from about 0 .001 to 1 .0 micrometer.Particles in this size range are often referred to as "colloidal"particles . Larger particles, such as sand and~ ~ilt, readily settle outof water during plain sedimentation, but the settling rate of colloidalparticles is so low that removal of colloidal particles by plainsedimentation is not practicable . Chemical coagulation andflocculation processes are required to remove these smaller particlesin sedimentation basins .

b . Chemical coagulants . The most frequently used chemical coagulantis aluminum sulfate : (A12(SO4)3 " 14H20), which averages about 17percent A1203 and is also called "alum" or "filter alum ." Otheraluminum compounds used as coagulants are potash alum and sodiumaluminate, principally the latter . Other coagulants include ferricsulfate, chlorinated copperas (ferrous sulfate), and ferric chloride .Organic polyelectrolyte compounds, alone or in combination withconventional chemical coagulants, are also employed . Thecoagulation-flocculation processes are accomplished step-wise byshort-time rapid mixing to disperse the chemical coagulant followed bya longer period of slow mixing to complete the flocculation process .Laboratory jar tests will normally be performed to determine the typeand quantity of coagulant(s) best suited to the water requiringtreatment .

c . Design criteria for mixing . Criteria for rapid- and slow-mixprocesses have been developed on the basis of detention time, powerinput, velocity gradient (G) and the product (Gt) of velocity gradientand detention time . The values of G and Gt are computed from thefollowing equations :

G=C

p\1/2UV)

Gt

and

_ _1 _PV 1/2Q (u

3-4

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where :

EM 1110- 3-1629 Apr 84

Gt = product of G and t, a dimensionless numberG = velocity gradi'ent (fps/foot ; or second -1 )P = the power dissipated in the water (ft-lb/second)u = water viscosity (poundf-seconds/square feet) (u = 2 .73 x

10-5 at 50 degrees F .)Q = flow through the sedimentation unit (cfs)V = volume of mixing basin (cubic feet)t = mixer detention time (seconds)

(1) Rapid mixing . The coagulant is introduced into the water byrapid mixing and coagulation is initiated . Detention periods forrapid-mix units usually range from 10 to 30 seconds with installedmixer power approximately 0 .25 to 1 .0 hp per mgd . Power and detentiontime should be matched so that values of G will be in the approximaterange : 500 to 1,000/second . A wire-to-water dfficiency of 80 percent,a water temperature of 50 degrees F ., a power input of 1 .0 hp per mgdand a detention time of 10 seconds, yield a G value of about 1,000/second and a Gt value of 10,000 . Similarly, a 30-second detention timegives a G value of about 600 and a Gt value of 18,000 . Long detentionperiods for rapid-mix basins should be avoided because of higher powerrequirements and inferior coagulation results . The rapid-mix basinshould be designed to minimize short circuiting .

(2) Slow mix . Flocculation is accomplished by slow mixing .Detention periods should range from 30 minutes to 60 minutes, withinstalled mixer power of approximately 0 .1 to 3 .5 hp per mgd . G valuesin the range of 20/second to 100/second are commonly employed .Corresponding Gt values will, therefore, be in the range of 36,000 to360,000 . Tapered, slow mixing with G decreasing from a maximum ofabout 90/second down to 50/second and then to 30/second can be used andwill generally produce some improvement in flocculation . Somewhathigher G values, up to 200/second, are employed in some water softeningplants . For normal flocculation, using alum or iron salts, the maximumperipheral speed of the mixing units should not exceed about 2 .0 fpsand provisions should be made for speed variation . To control shortcircuiting, two to three compartments are usually provided .Compartmentation can be achieved by the use of baffles . Turbulencefollowing flocculation must be avoided . Conduits carrying flocculatedwater to sedimentation basins should be designed to provide velocitiesof not less than 0 .5 fps and not more than 1 .5 fps . Weirs produceconsiderable turbulence and should not be used immediately followingflocculation .

3-5 . Sedimentation basins . Sedimentation follows flocculation, andthe most common types of sedimentation basins in general use are shownin figures 3-1 and 3-2 . A minimum of two basins should be provided toallow one unit to be out of service for repair, but construction of thesecond unit may be delayed until the first unit is operational . The

3-5

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EM 1110-3-1629 Apr 84

design must include arrangements that permit use of a single basin whennecessary .

a . Design criteria . Basins may be rectangular, square, or circularin plan . Basin depths generally are from 10 to 16 feet . Undercomparable conditions, deeper basins usually perform better thanshallow ones .

In general, the basins should be sized to' provide aminimum detention time of 2 to 4 hours . For conventional coagulationplants, basin overflow rates commonly range from roughly 500 to 1,500gpd per square foot with weir loading rates at 20,000 gpd per foot orless . Higher overflow rates may be used at some plants employingupflow clarification units . Sedimentation basin inlets, outlets, andbaffles must be carefully designed to minimize short circuiting . Thesolids (sludge) which settle to the bottom of the basin must be removedbefore the depth of the sludge becomes great'enough to interfere witheffective sedimentation . In general, mechaniccl sludge removalequipment is a requirement . All basins must be provided with drainsand overflows. Basin covers, usually in the form of a superstructure,will be required in northern localities where ice is a problem .

b . Flocculation-sedimentation basins . Unitscircular, combine the functions of flocculation,sludge removal . Flocculation is accomplished inwell . Sedimentation occurs in the annular spaceflocculation section and the perimeter effluent weir .are generally similar to those applicable to separate

of this type, usuallysedimentation, anda circular centerbetween the

Design criteriaunits .

c . Suspended solids contact basins . Basins of this type combinerapid-mixing, flocculation, sedimentation, and sludge removal in asingle unit . Coagulation and flocculation take place in the presenceof a slurry of previously formed precipitates which are cycled back tothe mixing and reaction zone . Upflow rates at the point of slurryseparation should not exceed about 1 .0 gpm per square foot for unitsused as clarifiers following coagulation .

3-6 . Filtration . Filtration of water removes colloidal and largerparticles from water by passage through a porous medium, usually sandor granular coal . The suspended particles removed during filtrationrange in diameter from about 0 .001 to 50 micrometers and -larger .Several different types of medium arrangements and rates of flowthrough filters can be used . The filtration process most commonly usedis rapid-sand filtration, but pressure filters and diatomite filtersare used at smaller installations .

a . Rapid sand filters .

(1) Filtration rate . Rapid sand filters commonly operate atrates between approximately 2 and 8 gpm per square foot . The usualrate is about 3 to 5 gpm per square foot . Adequate pretreatment andfilter design will allow application rates of up to 6 gpm per square

3-8

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EM 1110-3-1629 Apr 84

foot with little difference in water quality . If high rates are to beused in design, great care must be taken to insure that allprefiltration treatment processes including coagulation, flocculation,and sedimentation will perform satisfactorily and consistently .High rate filter operation definitely requires excellence inpre- .filtration treatment, especially in the case of surface waters . Itis recommended that data from laboratory or pilot studies be utilizedwhenever possible rather than an arbitrary selection of criteria .

(2) Filter medium .

(a) Sand . Silica sand is the most commonly used filter mediumand its depth should be at least 24 inches and not more than 30 inches .When sand is employed, its "effective size" should fall in the range of0 .35 to 0 .5 millimeter with a uniformity coefficient of 1 .3 to 1 .7 .Filter sand usually ranges in size from that~p~ssing a 16-mesh (U .S .Series) sieve to that retained on a 50-mesh (U .S . Series) sieve .Approximately 100 percent by weight of the sand should pass the 16-meshsieve and 90 to 100 percent be retained on a 50-mesh sieve . Filtersand should be clean silica sand having a specific gravity of not lessthan 2 .5 . The hydrochloric acid solubility of the sand should be lessthan 5 percent .

(b) Anthracite . Anthracite is an alternative medium con-sisting of hard anthracite coal particles . Its depth is usually bet-ween 8 inches and 3 feet . The effective size commonly ranges fromabout 0 .45 millimeter to 0 .6 millimeter with a uniformity coefficientnot to exceed 1 .7 . The hardness should not be less than 2 .7 on the Mohscale and the specific gravity not below 1 .4 . Also, the anthraciteshould be visibly free of clay, shale, and dirt .

(c) Multimedia . Multimedia filters employ two or threelayers of media of different size and specific gravity . A commonarrangement, the dual media filter, is 20 inches of anthraciteoverlaying a sand layer of approximately 8 to 12 inches . The anthra-cite layer has a size range of about 0 .8 to 2 .0 millimeter ; the sandlayer, about 0 .4 to 1 .0 millimeter . Tri-media filters employ an18-inch anthracite layer, an 8-inch sand layer, and an underlying4-inch layer of garnet or ilmenite having a size range of 0 .2 to 0 .4millimeter . Garnet has a specific gravity of about 4 and ilmeniteabout 4 .5 .

(3) Filter gravel and underdrains . The filter media is commonlysupported by a 10 to 18-inch layer of coarse sand and graded gravel .The gravel depth may range from 6 to 24 inches, depending on the filterunderdrain system chosen . The gravel should consist of hard, roundedstones having a specific gravity of at least 2 .5 and a hydrochloricacid solubility of less than 5 percent . A 3 to 4-inch transition layerof coarse (torpedo) sand, having a size range of about .05 to 0 .1millimeter, is placed on top of the filter gravel . Gravel size usually

3-9

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EM 1110-3-1629 Apr 84

ranges from about 0 .1 inch to about 2 .5 inches ; fine material thenincreasingly coarser material in the direction of flow for filtration .Filter underdrains may be constructed of perforated pipe - grids orvarious commercial underdrain systems .

(4) Number of filters . Not less than two filters should beinstalled regardless of plant size . For large plants, rough guidanceas to the number of filters to be provided may be obtained from thefollowing equation :

N = 2 .7 (Q)1/2

where :

N = number of filter unitsQ = design capacity in mgd

Thus, a 9 mgd plant would require eight filters .

(5) Size of filter units . The maximum filter size is related towash water flow rate and distribution . Normally, individual filtersizes do not exceed about 2,100 square feet corresponding to a capacityof about 6 mgd,.at a flow rate of 2 .0 gpm per square foot . A unit ofthis size would require a maximum backwash water rate of about 60 mgd,which is excessive . Consequently, it should be divided into two partsof equal size arranged for separate backwashing . Total filter boxdepth should be at least 9 feet .

(6) Filter backwash . Backwash facilities should be capable ofexpanding the filter media 50 percent . This will require wash rates inthe range of 10 to 20 gpm per square foot . Backwash water can besupplied by a backwash pump or from elevated storage providedspecifically for this purpose . Filter down-time during wash periodscommonly average 10 to 20 minutes including a 5- to 15-minute washperiod . For a 15-minute backwash of a single unit, at maximum rate,the wash water volume will be 300 gallons per square foot of filtrationarea in that unit . This aids in cleaning the filter and is commonlyaccomplished by rotary or fixed surface-wash equipment located near thetop of the bed . It is operated for a time period equal to that of thebackwash . Water pressures of 40 to 100 psi are required forsurface-wash operation at a rate of 0 .5 gpm per square foot . If anindependent wash water storage tank is used, it must refill betweenwashes . Tank capacity should be at least 1 .5 times the volume requiredfor a single wash .

(7) Wash water troughs . Wash water troughs equalize the flow ofwash water and provide a conduit for removal of used water . Two ormore troughs are usually provided . The elevation of the trough bottomsshould be above that of the expanded bed . The clear horizontaldistance between troughs should not exceed 5 to 6 feet, and the top of

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the troughs not more than 30 inches above the top of the non-expandedbed .

(8) Filter piping and equipment . Essential filter controlvalves, etc ., are shown schematically in figure 3-3 . Each filtershould be equipped with a rate-of-flow controller plus associatedequipment for automatic filter water-level control . The latter sensesthe water level in the main influent conduit and transmits a signal tothe flow controllers . The controllers, in response to this signal,adjust filtration rates to match the inflow from the sedimentationbasins . Thus, within practical limits, total filter outflow alwaysequals total inflow and the filter water level remains virtuallyconstant . A device that will sense maximum permissible clearwell levelshould also be provided . This should be arranged so that at maximumallowable clearwell water level a shut-off signal will be transmittedto all filter controllers and also to an audible alarm . Other designs,not involving rate controllers, such as "influent flow splitting" and"variable declining rate" have been developed and may be employed atthe discretion of the designer . In general, each filter must have fiveoperating valves : influent, wash water, drain, filtered water, andfilter-to-waste . It is emphasized that the filter-to-waste piping mustnot be directly connected to a plant drain or sewer . An effluentsampling tap must be provided for each filter . Valves can be manually,electrically, hydraulically, or pneumatically operated . Butterfly typevalves are recommended for filter service . Design velocities commonlyemployed for major filter conduits are as follows :

EM 1110-3-1629 Apr 84

The filtered water conduit must be trapped to prevent backflow of airand provide a seal for the rate controllers . The filter pipe galleryshould have ample room, good drainage, ventilation, and lighting .Dehumidification equipment for the gallery should receiveconsideration . Filters should be covered by a superstructure exceptunder favorable climatic conditions . Drainage from the operating floorinto the filter should be prevented by a curb . Access to the entirebed should be provided by a walkway at operating floor level around the

disposal facility . Regulatory agencies generally view filter wash

3- 1 1

ConduitDesign Velocity- fps - .

Influent 1-4Filtered water 3-6Wash water 5-10Drain 3-8Filter-to-waste 6-12

filter . Filters may be manually or automatically controlled from localor remote locations . Facilities permitting local, manual control arerecommended irrespective of other control features . Used backwashwater should be discharged to a wash water recovery basin or to a waste

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EM 1110-3-1629 Apr 84

FILTER TOWASTE(FILTERDRAIN)

U . S . Army Corps of Engineers

FILTERED WATER TO CLEARWELL

MAXIMUM WATER LEVELDURING FILTERING .

FILTER UNDER DRAINMEDIA

FIGURE 3-3 . SCHEMATIC OF RAPID SAND FILTER OPERATIONAL CONTROLS

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water as a pollutant and forbid its direct discharge to the naturaldrainage .

(9) Essential Instrumentation . Minimum essentialinstrumentation for each filter will be provided as follows :rate--.of-flow Indicator, loss-of-head indicator, wash water rate-of-flowindicator, and totalizing meter . If a wash water storage tank isprovided, It must be equipped with a water-level indicator .

b . Pressure filters . Pressure filters are similar in constructionand operating characteristics to rapid sand filters ; however, in apressure filter the media, gravel bed, and underdraIns are enclosed Ina steel shell . An advantage of a pressure filter is that any pressurein the waterlines leading to the filter Is not lost, as in the case ofgravity filters, but can be used for distribution of the filteredwater . Between 3 and 10 feet of pressure head are lost through thefilter . The primary disadvantage of a pressure filter is that, due tothe filter being enclosed in a steel shell, access to the filter bedfor normal observation and maintenance Is restricted . Also, the steelshells require careful periodic maintenance to prevent both internaland external corrosion . The use of pressure filters Is notadvantageous In most systems ; however, if the pressure requirements andconditions in a particular system are such that repumpIng of filteredwater can be eliminated, cost savings will be realized .

3-7 . Disinfection . Disinfection Involves destruction or deactivationof organisms which may adversely affect the health of the waterconsumer . The preferred method of disinfecting water supplies is byapplication of chlorine to water (chlorination) .

a .

Definitions .

Terms frequently used in connection withchlorination practices are defined as follows :

(1) Chlorine demand . The difference between the concentrationof chlorine added to the water and the concentration of chlorineremaining at the end of a specified contact period . Chlorine demandvaries with the concentration of chlorine applied, time of contact,temperature, and water quality .

(2) Chlorine residual . The total concentration of chlorineremaining in the water at the end of a specified contact period .

(3) Combined available residual chlorine . Any chlorine in waterwhich has combined with nitrogen .

(4) Free available residual chlorine . That part of the chlorineresidual which has not combined with nitrogen .

b . Chlorination practice .

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(1) Breakpoint chlorination . If water contains ammonia orcertain nitrogeneous organic matter which reacts with chlorine, theaddition of chlorine causes the formation of chloramines until theratio of elemental chlorine to ammonia compounds is about 5 to 1 .Further addition of chlorine results in the oxidation of chloramines togaseous nitrogen and nitrogen oxides, which decreases the quantity ofchloramines present . After all of the chloramines have been oxidized,additional chlorine added to the water forms only free availablechlorine . The point at which all of the chloramines have been oxidizedand only free chlorine is formed is called the "breakpoint ." If noammonia is present in the water, there will be no breakpoint . Thechlorine required to reach the breakpoint is usually about 10 times theammonia nitrogen content of the water . However, in certain waters,because of the presence of other chlorine consuming substances, as muchas 25 times the ammonia nitrogen concentration may be required . Enoughchlorine should be added past the breakpoint to insure an adequate freechlorine residual .

(2) Marginal chlorination . Marginal chlorination involves theapplication of chlorine to produce a desired level of total chlorineresidual regardless of the relative concentrations of free or combinedchlorine present .

In marginal chlorination, the initial chlorinedemand has been satisfied, but some oxidizable substances remain .

(3) Chlorine dosages . Figure 3-4 provides minimum cysticidal andbactericidal free chlorine residuals and minimum bactericidal combinedchlorine residuals for various pH and temperature levels . Sincewaterborne bacteria are the major concern at fixed installations,minimum bactericidal levels will be maintained in treated water in allparts of the distribution system under constant circulation . Even atlower pH levels, free chlorine residuals should not fall below 0 .2 mg/land combined chlorine residuals should not fall below 2 .0 mg/l . Ifmarginal chlorination is practiced, the total chlorine residual mustnot be less than 2 .0 mg/l . Whenever epidemological evidence indicatesan outbreak of a nonbacterial waterborne disease such as amebiasis,infectious hepatitis, or schistosomiasis, cysticidal free chlorineresiduals must be maintained in the water supply .

c . Other effects of chlorination . In addition to the disinfectionachieved with chlorination, many other effects should be noted . Sincethe oxidizing power of chlorine is high, in the presence of freechlorine, hydrogen-sulfide is oxidized, nitrites are oxidized tonitrates, and soluble iron and manganese are oxidized to theirinsoluble states . Free chlorine also destroys many taste and odorproducing substances . Many organic substances will react with chlorineto form chloro-organic compounds which may be objectionable eitherbecause of resultant tastes and odors or because of possible healtheffects .

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1,000

500

vOEIHv

0 100WHz

0MW_WU-4JQO

100

50

5

20.5

z

0.

005

0.0 5 7

U . S . Army Corps of Engineers

pH 8 9

FIGURE 3-4 . MINIMUM CHLORINE RESIDUALS

3-15

10

EM 1110-3-1629 Apr 84

CURVE

A : Cysticidal Free Chlorine, 2 ° -5 ° CB : Cysticidal Free Chlorine, 22 ° =25 ° CC : Bactericidal Combined Chlorine, 0°-25°CD : Bactericidal Free Chlorine, 0 ° -25°C

PFF

NEW7

MINIMUMCHLORINE

RECOMMENDEDRESIDUAL f2mg./l

COMBINED

D

MINIMUM RECOMMENDEDCHLORINE RESIDUAL-

LFREE

0.2mg/L

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EM 1110-3-1629 Apr 84

d . Application of chlorine . Chlorine may be applied to water inone of two forms :

as elemental chlorine or as hypochlorite salts .Hypochlorite salts should be-used for water disinfection at all fixedinstallations unless it can be demonstrated that the use of elementalchlorine is more advantageous .

(1) Point of application . Chlorine may be applied to water in avariety of locations in the water treatment plant, storage facilities,or distribution system . It is absolutely essential that the chlorineapplied to the water be quickly and thoroughly mixed with the waterundergoing treatment . If required, special chlorine mixing facilitiesshould be provided . In conventional water treatment plants, chlorinemay be applied prior to any other treatment process (prechlorination),following one or more of the unit treatment processes(postchlorination), or in the more distant points of the distributionsystem (rechlorination) .

(2) Chlorination equipment . Hypochlorite salts must be appliedto the water in solution form . Hypochlorite solutions are pumped by adiaphragm pump through an injection system into the water to bechlorinated . If elemental chlorine is used for disinfection, it shouldbe injected by solution-type chlorinators . Since chlorine solutionsare corrosive, many components of a chlorination system must beconstructed of corrosion resistant materials such as glass, silver,rubber, or plastics . Maintaining the chlorination apparatus in atrouble-free state is essential ; therefore, key spare parts and repairkits for chlorination systems will be kept on hand .

(3) Automatic control . If automatic chlorination control isutilized, the chlorine feed rate should be controlled primarily by therate of flow of water, with a signal from a downstream residualchlorine analyzer used to adjust the feed rate . Provision for manualcontrol during emergency situations must be included .

e . Superchlorination and dechlorination . Superchlorination may benecessary if there are large variations in chlorine demand or ifavailable contact time is brief . Water which has been superchlorinatedgenerally requires dechlo'rination before delivery to the distributionsystem . Dechlorination may be achieved through the application ofsulfur dioxide, sodium bisulfite,

or sodium sulfite, or by passing thewater through granular activated carbon filters . The dechlorinationprocess (and subsequent rechlorination, if necessary) should becontrolled so that the free residual chlorine remaining in the water isat least 0 .2 mg/l .

f . Safety precautions for chlorination . The AWWA M3 containssafety recommendations regarding the use of chlorine . Theserecommendations will be followed at all Army water treatmentfacilities .

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3-8 . Taste and odor control . Most taste and odors in surface waterare caused by low concentrations of organic substances derived fromdecomposing vegetation, microscopic organisms, sewage and industrialwaste pollution, etc . Treatment for taste and odor removal involvesdestruction of the odorous substance by chemical oxidation or itsretioval by aeration or adsorption by activated carbon .

a . Chemical oxidation . Chemical oxidizing agents which have beenfound effective and which can be used in the treatment of potable waterare chlorine, chlorine dioxide, potassium permanganate, and ozone . Nosingle chemical is completely effective under all operatingconditions .

b . Aeration . Aeration is helpful in eliminating odor caused byhydrogen sulfide and other dissolved gases, but is ineffective insignificantly reducing odor associated with 'dissolved organics .

c . Adsorption . Powdered activated carbon is commonly used forremoval of odor by adsorption . The carbon can be applied to the waterat any point in the treatment plant prior to filtration, but it isusually advisable to apply it early in the treatment process .Sometimes a split feed of carbon is employed with a portion applied tothe raw water and a smaller amount to the filter influent . For maximumeffectiveness, carbon should be applied well ahead of chlorination .The influent to a presedimentation basin is normally an effectivecarbon application point . Powdered carbon dosages usually range from 5to 10 mg/l, but as much as 50 mg/1 may be required under adverseconditions . Granular carbon has also been used for taste and odorremoval . It has been employed as a separate treatment step in the formof carbon columns and as a substitute for sand in the filtrationprocess . Used in this way, the granular carbon serves in a dualcapacity as a filtration medium and for taste and odor removal .

3-9 . Softening .

a . Applications . Softening of the entire base water supply will beconsidered only if the hardness exceeds 400 mg/l, expressed asequivalent CaC03 . In thin case, conventional softening techniques,which can be found in standard textbooks on water treatment processesshould be considered . Softening to levels below 400 mg/1 will only beperformed on waters intended for the applications outlined inparagraphs (1) through (3) below . The cation ion exchange or zeoliteprocess should be considered here unless other treatment methods aremore feasible or necessary .

(1) Laundries . Water for laundries should have a hardness of 50mg/l or less .

(2) Boilers . Boiler water for power plants and heating plantsmay require softening, but satisfactory results can often be obtained

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EM 1110-3-1629 Apr 84

by application of corrosion and scale inhibitors such as sodiumsulfite, sodium hexametaphosphate, and trisodium phosphate . Dependingon the pressure at which the boiler is to operate, partialwater-demineralization may also be necessary . See paragraph 3-12a foradditional information on demineralization .

(3) Hospitals . When the water supplied to a hospital has ahardness of 170 mg/l or more, the water will be softened toapproximately 50 mg/l . Where critical equipment requires water havinga hardness of less than 50 mg/l, the most feasible means of obtainingthat water quality will be used . Zero hardness water may be piped fromthe main softener or may be supplied from small individual softeners,whichever is the more feasible . The sodium content of the treatedwater must be taken into account when selecting a softening method forhospitals .

b . Cation exchange softening . Hardness is caused principally bythe cations of calcium and magnesium, and cation exchange softening isaccomplished by exchanging these ions for a cation, usually sodium,which does not contribute to hardness . This exchange is achieved bypassage of the water through the bed of a granular sodium cationexchanger . This reaction is reversible and the exchanger can beregenerated with a strong solution of sodium chloride common salt) .

(1) Media used for ion exchange softening . Ion exchange watersofteners should use polystyrene resins as the softening media . Suchresins must have a hardness exchange capacity of at least 25,000 grainsof hardness per cubic foot of resin .

(2) Regeneration of ion exchange softeners . The regenerationprocess generally involves three steps : (1) backwashing, (2)application of regenerating solutions, and (3) rinsing .

(a) Backwashing . The purposes of water softener backwashingare generally the same as the purposes of filter backwashing . Anyturbidity particles filtered out of the water during softening areremoved by the backwashing process . For polystyrene resin media, bedexpansions of from 50 to 100 percent are normally required, whichinvolve backflow rates of 4 to 10 gpm per square foot of bed area.Backwash periods generally range from 2 to 5 minutes . Ion exchangewater softeners which operate upflow rather than downflow will notrequire backwashing, but the water to be softened must be virtuallyfree of suspended matter .

(b) Application of salt brine . After the unit has beenbackwashed, a salt solution is applied to the medium in order toregenerate its softening capabilities . Regeneration brines should be10 to 15 percent solutions of salt . The more salt used in theregeneration of a softener, the more complete the regeneration will be,and the greater the exchange capacity of the regenerated medium will

3- 1 8

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EM 1110-3-1629 Apr 84

be . Salt consumption commonly ranges from about 0 .3- to 0 .5-pound ofsalt per 1,000 grains of hardness removed . The contact time of thebrine with the softening medium also has a direct effect on theexchange capacity of the regenerated medium . Contact times of 20 to 35minutes will generally be used .

(c) Rinsing . After regeneration, the brine must be rinsedfrom the unit before softening is resumed . Backwash water, spentregenerant, and rinse water must be disposed of properly .

(3) Ion exchange water softeners . Although most Ion exchangesofteners at Army installations will be downflow pressure softeners,softening can also be achieved upflow . Larger Ion exchange softeningfacilities are often operated upflow in order to avoid the necessity ofbackwashing . In general, ion exchange softeners are of two types :open gravity softeners and pressure softeners .

(a) Open gravity softeners . Open gravity softeners areconstructed in much the same manner as rapid sand filters, and themodes of operation are very similar . However, the ion exchange mediumused in open gravity softeners is much lighter than the sand used infilters, so backwash rates for open gravity softeners may also beoperated upflow, but the softener will not achieve any filteringeffects so the Influent water must be virtually free of suspendedmatter .

(b) Pressure softeners . A polystyrene resin medium used forpressure softening should have a minimum bed depth of 24 inches andphysical properties approximately the same as the following :

Shipping weightDensityMoisture contentVoid volumeScreen gradingEffective sizeUniformity coefficientFines through 50 mesh screen

3-1 9

45-55 pcf, net48-53 pcf42-48 percent40 percent16-50 mesh0 .45-0 .55 millimeter<1 .70<1 percent

If downflow softening Is used, the flow rate through the softeningmedium may vary from 2 to 8 gpm per square foot but must not exceed 10gpm per square foot under the most severe loadings . Severe reductionsin exchange capacity are experienced if the softener operates at ratesof flow in excess of 10 gpm per square foot for sustained periods oftime . With upflow softening, the rate of flow should be adjusted tomaintain a bed expansion of from 40 to 60 percent . The degree of bedexpansion Is a function of both the flow rate and the temperature ofthe Influent water, so the flow rate must be decreased as watertemperature decreases If a constant bed expansion is to be maintained .

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(4) Blending . An ion exchange softener operating properly willproduce a water having a hardness approaching zero . Inasmuch as it isnot generally economical nor desirable to soften all water to this lowhardness level, provisions for blending the softened water with theunsoftened water are desirable .

(5) Other factors affecting ion exchange softening .

(a) Turbidity . Turbidity particles present in the waterinfluent to the softener are deposited on the softening medium and maycause losses of exchange capacity and excessive head losses through thesoftener . If turbidity levels are excessive, the particles must beremoved from the water prior to softening or special backwashingprocedures must be implemented .

(b) Bacterial slimes . Unless proper disinfection ispracticed, bacterial slimes can form in the softening medium and causeexcessive head losses and loss of exchange capacity . These slimes canbe prevented or removed through chlorination of feedwater orregeneration water .

(c) Temperature . The loss of head through a water softeneris strongly affected by water temperature, with lower head lossesoccurring at higher temperatures . For example, at similar flow rates,the head loss through a softener at 122 degrees F . is only about 35percent of what it would be at 36 degrees F . Also, the watertemperature affects the exchange capacity of the softener, with a 10 to15 percent increase at high operating temperatures (>86 degrees F .)over the exchange capacity at low temperatures (32 to 50 degrees F .) .

(d) Iron, manganese, and aluminum . If iron, manganese, andaluminum are present in the influent water, precipitates may be formedwhich coat the ion exchange media particles and cause a loss ofexchange capacity . This problem can be avoided through treatment toremove the iron, manganese, and aluminum from the water prior tosoftening .

(e) Total hardness and sodium concentration . If the totalhardness exceeds 400 mg/l or the sodium salts, expressed as mg/l CaC03,exceed 100 mg/l, the softener should be sized on the basis of the"compensated total hardness" rather than the total hardness .Compensated hardness is calculated from the equation :

THc = (TH) (9,000)

where :

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THc = compensated hardness in mg/l as CaC03TH = total hardness In mg/l as CaC03TC = total cations in mg/l, all expressed as CaC03

Compensated hardness (THc ) in mg/l is converted to grains per gallon bymultiplying by 0 .0584 or dividing by 17 .1 .

3-10 . Iron and manganese control .

a . Occurrence of iron , and manganese . Dissolved iron and manganeseare encountered principally in ground waters devoid of dissolvedoxygen . Normally, oxygenated surface waters do not contain significantconcentrations of these metals ; however, stagnant water, found in thebottom of thermally-stratified reservoirs, sometimes contains dissolvedIron and manganese . Their presence in solution Is associated withanaerobic conditions near the bottom of the reservoir .

b . Effects of iron and manganese . Dissolved Iron In excess of 1 or2 mg/l will cause an unpleasant taste, and on standing, the water willdevelop a cloudy appearance . Iron concentrations appreciably greaterthan 0 .3 mg/l will cause red stains on plumbing fixtures and laundry .Similarly, manganese will cause black stains If present to the extentof more than about 0 .05 mg/l . Deposits of Iron and manganese can buildup In water distribution systems and periodic "flush-outs" of thesedeposits result In objectionable color and turbidity at the consumer'stap .

c . Removal by oxidation and filtration . Oxidation can beaccomplished with dissolved oxygen, added by aeration, and by theaddition of an oxidizing chemical, such as chlorine, chlorine dioxide,potassium permanganate, or ozone . Manganese Is more difficult thaniron to oxidize and precipitate . In the absence of manganese, iron canoften be removed with minimum treatment, consisting of aerationfollowed by direct filtration . In general, aeration alone will notoxidize manganese unless the pH Is raised to about 9 .5 .

Strongoxidants, such as chlorine or potassium permanganate, are effective atlower pH values . To Insure oxidation, precipitation, and agglomerationof iron and manganese and their essentially complete removal, at leastthree treatment steps are usually necessary : aeration, contact time,and filtration . An aerator containing trays of coke, limestone, etc .,Is commonly used . Reaction time is provided by a contact orcontact-sedimentation basin having a detention period of at least 30minutes . Filtration is accomplished by conventional single ormultl-media filters designed for a filtration rate of at least 3 .0 gpmper square foot . The aeration step Is frequently supplemented by achemical oxidant, such as chlorine or permanganate . Flocculation Isadvantageous in the contact basin, particularly if Iron exceeds about 2mg/ :s . .

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EM 1110-3-1629 Apr 84

3-11 . Corrosion and scale control . "Corrosion" can be defined as thedeterioration of metal by direct chemical or electrochemical reactionwith its environment . "Scale" refers to an accumulation of solidsprecipitated out of the water . In water treatment, corrosion and scaleare closely associated . Both must be considered in connection with thedesign and operation of the treatment works . Thin scale may bedesirable because it can provide a measure of protection againstcorrosion . However, thick layers of scale are detrimental in both hotand cold water systems . It is desirable to produce a "balanced" waterthat is neither highly corrosive nor excessively scale forming .

a . Corrosion .

(1) The extent and nature of corrosion reactions depend uponmany factors . Among the most important are the chemical and physicalnature of the water, its velocity, pipe metallurgy, and pipe coating .Controllable factors are principally calcium content, alkalinity, andpH . Certain corrosion inhibitors can also be used, but relatively feware suitable for potable water systems .

(2) Treatment to insure deposition and maintenance of a thinlayer of calcium carbonate on the pipe interior is one widely usedmeans of corrosion control . The rate of formation of calcium carbonateis favored by high concentrations of calcium and bicarbonate andcarbonate alkalinity . Protection of this type cannot be attained inwaters containing very low concentrations of calcium and alkalinity .

(3) Corrosion rates may also be reduced by the use of certaininhibitors . For potable water systems, the most practicable inhibitorsare silicates and certain polyphosphate compounds .

(4) Dissolved oxygen and carbon dioxide have a significanteffect on corrosion rates . Carbon dioxide lowers the pH and makes thewater more aggressive .

(5) Corrosion rates are influenced to some extent by all mineralsubstances found in water, but corrosion effects are so interrelatedthat it is not possible to isolate the quantitative influence ofindividual ions. It is known that high concentrations of chloride andsulfate ions will produce increased corrosion rates . However, theiradverse effects are somewhat mitigated by alkalinity (carbonate,bicarbonate) and calcium ions . Excessive calcium and alkalinity willoften result in objectionable scale formation . It is, therefore,necessary to seek a compromise between corrosion on the one hand' andscale formation on the other .

(6) Based on the corrosion accelerating effects of chloride andsulfate and the corrosion inhibiting effects of alkalinity, thefollowing ratio, termed the "Corrosion Index," has been developed .

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Corrosion Index = [ .02821] [C1- ] + [ .02083] [S042-]

where :

[C1- ] - mg/l chloride ion as C1-

[ .01639] [HC03- 1

[S042-] = mg/l sulfate ion as S042-

[HC03 -] = mg/l bicarbonate ion as HC03-

EM 1110-3-1629 Apr 84

For a pH range of about 7 to 8, and in the presence of dissolvedoxygen, an index below about 0 .1 indicates probable general freedomfrom corrosion . An index higher than 0 .1 is indicative of corrosivetendencies . The higher the index, the greater the probability ofcorrosion .

b . Scale . Scale problems in distribution systems are causedprincipally by calcium carbonate, magnesium hydroxide, aluminumhydroxide, and the oxides and hydroxides of manganese and iron .

(1) Aluminum . Aluminum hydroxide deposits can result fromexcessive alum use for coagulation and/or improper coagulationpractice, such as poor mixing and flocculation and incorrectcoagulation pH .

(2) Magnesium. Magnesium hydroxide deposits have caused seriousdifficulties in distribution systems and hot water heaters . Magnesiumsolubility is highly sensitive to pH and temperature and failure toexercise careful control over its stabilization following softeningwill usually lead to deposition problems . It is advisable to maintainmagnesium hardness below 40 mg/l and pH below 9 .8 . Hot water heatersshould be operated so that water temperatures will not exceed 140degrees F .

c . Chemical control of scale and corrosion . Corrosion protectionof water system components can be achieved through the use ofcorrosion-resistant materials including plastics, copper, concrete, andcement-asbestos ; the use of galvanized pipe ; and the use of cement orcoal-tar or calcite lined pipe . . Chemical control by pH adjustment,and/or the addition of sodium silicate or polyphosphates to the watermay be employed to supplement these protective measures if it isprobable scale and/or corrosion will pose major problems to the watersystem components over the project design life . Chemical control canbe expected to alleviate the problems but not necessarily eliminatethem.

3-12 . Special processes . In some cases, it will be necessary to use

raw water supplies containing unacceptably large concentrations of

constituents that cannot be removed by conventional treatment

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EM 1110-3-1629 Apr 84

processes . The most common of these objectionable constituents aremineral salts, such as sulfates and chlorides, dissolved organicsubstances, and excess fluorides . Special treatment processes arenecessary to remove these materials .

a . Demineralization . The presence of excessively highconcentrations of dissolved materials in water is indicated by highchloride (Cl - ), sulfate (S042- ), and total dissolved solids (TDS)levels . The limits for'these substances for mobilization work are 250mg/1, 250 mg/1, and 500 mg/1, respectively . These limits are based onesthetic considerations, and considerably higher concentrations, whilenot desirable, can be tolerated . Where demineralization is required,processes commonly employed are electrodialysis, reverse osmosis,distillation, and ion exchange . Waste brine solutions derived fromthese processes must be disposed of properly : All demineralizationprocesses are energy intensive, and alternative water sources should bethoroughly investigated before a commitment to a demineralizationproject is made . If the demineralization process selected requireslarge inputs of electricity, consideration should be given to itsoperation principally during "off-peak" hours with storage of desaltedwater until needed .

b . Removal of dissolved organics . An effective means of removingdissolved organics is by their adsorption on granular activated carbon .Periodically, the granular carbon must be removed from the treatmentsystem and reactivated in a special furnace . The carbon can serve as afilter medium as well as an adsorbent and is sometimes installed inconventional filters in place of the sand filter medium .Alternatively, the granular carbon may be employed in a special carboncontactor following conventional filtration . The granular carbon'seffective size should be 0 .7 to 1 .0 millimeter ; its uniformitycoefficient, <1 .9 . When used in a filter, the carbon bed depth shouldbe at least 2 feet and the corresponding hydraulic loading about 2 gpmper square foot . Where specially designed carbon contactors areprovided following conventional filtration, 2- to 10-foot bed depthsand hydraulic rates of about 5 gpm per square foot can be employed .The longer contact time provided by the deeper beds reducesreactivation frequency .

c . Excess fluoride removal . Fluoride concentration in excess ofthe limits stipulated in TB MED 576 pose a health hazard and must beremoved . Fluoride removal can be accomplished by passage of the waterthrough beds of activated alumina, bone char, or tricalcium phosphate,electrodialysis, reverse osmosis, or ion exchange . All removalprocesses produce liquid wastes and suitable provisions must be madefor their disposal . Guidance as to the fluoride removal process to beemployed can be obtained from laboratory studies of processeffectiveness and fluoride removal capacity, using samples of the waterthat is to be treated .

3-24

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CHAPTER 4

MEASUREMENT AND CONTROL

EM 1110-3-1629 Apr 84

4-1 . Measurement of process variables . In order to determine thedegree of effectiveness of the different treatment processes, severalphysical and chemical parameters associated with water treatment mustbe measured . After they are measured, the information must beevaluated so that necessary adjustments can be made in the treatmentprocess .

a . Minimum analyses . The minimum type, number, and frequency ofanalyses for water treatment plants will conform to paragraph B-1 ofappendix B .

b . Laboratories . Provisions should be made for laboratoryfacilities either on or off the mobilization site . If feasible, theservices of private laboratories or laboratories at nearby municipalwater plants should be solicited .

c . Records of analyses . Results of laboratory analyses will berecorded and maintained in an orderly filing arrangement .

4-2 . Control . Water treatment plant processes may be controlled bymanual, semiautomatic, or automatic methods, which are defined asfollows .

a . Manual control . Manual control involves total operator controlof the various water treatment processes . The personnel at the watertreatment plant observe the values of the different variablesassociated with the treatment processes, and make suitable adjustmentsto the processes .

b . Semiautomatic control . Semiautomatic control utilizesinstruments to automatically control a function or series of functionswithin control points that are set manually . The operator manuallystarts the automatic sequence of operations . An example ofsemiautomatic control is the, automatic backwashing of a filter afteroperator initiation of the program .

c . Automatic control . Automatic control involves the use ofinstruments to control a process, with necessary changes in the processmade automatically by the controlling mechanisms . When a processvariable changes, the change is measured and transmitted to a controldevice which adjusts the mechanisms controlling the process . Automaticcontrol systems have been developed which are reliable, but provisionsfor emergency manual control must be included .

4-3 . Design of instruments and controls . All instruments and controldevices should be placed in readily accessible locations in order to

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EM 1110- 3-1629 Apr 84

facilitate observation, maintenance, repair, and replacement .Instruments should not be located in environments which might lead topremature failure of the instruments . Examples of such environmentsare areas subject to high temperatures or corrosive vapors . Provisionsshould be made for many of the instruments to actuate alarms ifcritical process variables exceed or fall below predetermined tolerablelevels . Such alarms should include both audio and visual signals .

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CHAPTER 5

WATER TREATMENT CHEMICALS

EM 1110-3-1629 Apr 84

5-1 . Chemical properties . Chemicals are used for a variety ofpurposes in conventional water treatment practice, includingcoagulation and flocculation, disinfection, taste and odor control, andpH adjustment . The most common chemicals and some of theircharacteristics are listed in table 5-1 .

5-2 . Chemical standards . Chemicals used at Army water treatmentplants will meet the applicable standards of the American Water WorksAssociation (AWWA) . If chemicals meeting the AWWA standards are notavailable, then substitute materials may be used after they areevaluated and determined by the Surgeon General of the Army to be safefor drinking water .

5-3 . Chemical handling and storage . In the design of water treatmentfacilities, the selection of methods of chemical handling and storagemust be based primarily on ease of operation, operating flexibility,and safety considerations . If chemicals are to be received in shipping.containers such as bags, boxes, drums, or canisters, equipment requiredfor chemical handling may include carts, dollies, fork lifts, cranes,etc . If chemicals are shipped in bulk quantities, the mode ofunloading depends on the physical characteristics of the chemical .Bulk liquids are usually unloaded by pumping from the tank truck orrailroad car to the storage tanks at the treatment plant . Bulk powderscan be unloaded by pneumatic unloading and conveyance devices, or ifthe powder is to be mixed or dissolved in water, It can be unloadeddirectly into a water eductor in which the powdered chemical and thewater are mixed as the water is flowing to the storage tank . Chemicalcrystals or granules are usually unloaded by mechanical devices, suchas bucket elevators and conveyor belts . All three forms of bulkchemicals can be unloaded by gravity if the chemical storage tanks orbins are located below ground near railroad tracks or roadway .Chemicals shipped in bags, drums, barrels, or other shipping containerscan usually be stored by placing these containers in a specifiedstorage area . The supply of chemicals in storage at a water treatmentplant should always be at least equal to the projected 30-dayrequirements . Under some circumstances, it may be desirable tomaintain larger supplies of essential chemicals, such as disinfectantsor coagulants, and smaller supplies of nonessential chemicals . Extremecaution must be used when handling and storing most water treatmentchemicals . Mishandling may cause death, injury, or at the very least,may render chemicals ineffective . Hazardous chemicals, such aschlorine gas, must be stored in separate rooms to avoid reaction ofchemical vapors . When doubt exists as to the proper handling ofcertain chemicals, advice from the manufacturer or other technicallycompetent authority should be sought .

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EM 1110-3-1629 Apr 84

5-4 . Chemical application .

a . Dry chemicals . Dry chemicals are usually converted to asolution or slurry prior to application to the water . Measurement ofthe chemical application rate is accomplished by the dry-feed machine .The measured quantity of chemical is then dissolved or slurried in asmall amount of water for transport to the feed point, where thesolution or slurry must be rapidly and thoroughly mixed with waterbeing treated .

b . Liquid chemicals . Chemical solutions or slurries are applieddirectly, or after dilution, to the water being treated by volumetricliquid feeders such as metering pumps or rotating wheel feeders .Rapid, thorough mixing of the chemical solution or slurry with thewater is essential .

c . Chlorine application . Hypochlorite solution will be fed by aninjector, diaphragm pump, or centrifugal pump system . The point ofdischarge of the chorine solution must be at least 2 feet below thewater surface .

d . Corrosion . Special attention should be directed to thematerials used for the critical parts of chemical feeders . Manychemicals form corrosive environments for common metals .

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90to

ntank

cars,

tank

trucks

(about

15-1

6to

ns)

Table

5-1

.Pr

inci

pal

chemicals

Used

inWater

Trea

tmen

t

Chem

ical

Name

Common

orShipping

Suitable

Han-

Bulk

Density

Solu

bili

tyCo

mmer

cial

and

Formula

Trade

Name

Purpose

Containers

dlin

gMa

terials

lb/c

uft

lb/gal

Strength

Characteristics

Alum

inum

sul-

Liquid

alum

Coagulation

Tank

trucks

Lead

orrubber-

(11.047

lbs/

5.3

6lb

adry

pHof

1%solution

is3.4

fate

solu

tion

ortank

cars

line

dsteel,

316

gal)

alum

per

stainless

steel,

gallon

plastic

Alum

inum

sul-

Alum,

filter

Coagulation

100-200

lb.

Dry-

Iron

,st

eel

.4.2

at60°F

15-22%

A1203

pHof

1%solution

is3.4

fate

(dry

),alum,

sulfate

bags

,300-

Solution-lead-

Powder

38-4

5A12(SO4)3

ofalumina

400

16.

lined

rubb

er,

Granule

60-63

-14

H2O

barr

els,

bulk

sili

con,

asph

alt,

Lump

62-67

(carloads)

.31

6stainless

stee

l

Sodi

umalumi-

Soda

alum

Coagulation

100-150

lb.

Iron

,plastics,

50-60

Highly

70-80%

Hopper

agitation

required

nate

Na20A1203

bags

;250-

rubb

er,

stee

lsoluble

Na2A

1304

,-

for

dry

feed

440

lb.

32%

Na2A1304

drums

;solu-

minimum

tion

.

Ferrous

sulfateCopperas,

Coagulation

Bags

,As

phal

t,concrete,

63-66

0.5

at32°F

55%

FeS04

Hygroscopic

;cakes

inFeS04

-7H

20green

vitriol

barrels,

bulk

lead

,tin,

wood

1.0

at68°F

20%

Fest

orag

e;op

timu

mpH

is1.4

at86°F

8.5

-11.0

Ferr

icch

lori

deFerrichlor,

Coagulation

5-13

gal

.Glass,

ston

ewar

e,(1

1.2

-12.4

lbs

37-47%

FeC1

3Very

corrosive

FeC1

3(37-47%

chloride

ofca

rboy

s,synthetic

resi

ns/g

al)

13-16%

Fesolution)

iron

truc

ks,

tankcars

Ferr

icsulfate

Ferr

iflo

c,Co

agul

atio

n50

-175

lb.

Ceramics,

lead

,56-72

Soluble

in66

%Fe2SO4

Mildly

hygroscopic,

Fe2(SO4)3

'Ferrisul

bags

,20

0-42

5pl

asti

c,ru

bber

,2-

4parts

20%

FeCoagulant

atpH

3.5

-11.0

9H20

lb.drums

18-8

stainless

wate

rst

eel

Sodi

umsi

lica

teWater

glass

pHcont

rol

Drum

s,bulk

Cast

Iron

,ru

bber

,(1

1.6

lbs/

gal)

Highly

28.7%

Si02

Variable

ratioof

Na20

toNa20SiO2

(tank

truc

ks,

stee

lsoluble

Si02

.pH

of1%

solution

tank

cars)

is12

.3.

Chlo

rine

Chlorine

gas,

Disinfection

100-150

16.

Dry

-bl

ack

iron

,91

.70.063

at50

°F99

.8%

C12

Toxic

gas

.Solutions

inliquid

cylinders,

copp

er,

steel

.(l

iqui

dat

0.047

at86

°Fwa

terhighly

acidic

and

chlorine

1to

ncon-

Wet

gas-

glas

s,32

°F)

corrosive

.tainers,

16-

hard

rubb

er,

silver,

30-55-85

and

earthenware

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U.S

.Army

Corp

sof

Engi

neer

s

Characteristics

able" Danger

ofexplosion

oncontact

with

organic

matter

pHof

saturated

solution

is12

.4

pHof

satu

rate

dsolution

at68°F

isapprox

.4.0

.

Corrosive

when

mois

t.

pHof

1%solution

is6.7-7

.2

toM rI ON N

Tabl

e5-

1.

Principal

Chemicals

Used

inWa

ter

Treatment

(Continued)

Chemical

Name

Common

orShipping

Suitable

Han-

Bulk

Density

Solubi

lity

Comm

erci

aland

Form

ula

TradeName

Purpo se

Containers

dlin

gMaterials

16/cu

ftlb

/gal

Strength

Calciumhypo-

"HTH",

"Per-

Disinfection

516

.ca

ns,

Glas

s,ru

bber

,48

Approx

.on

e70

%"avai

chlo

rite

chlo

ron"

,100-300-800

ston

ewar

e,wood

chlorine

Appr

ox.

"Pittchlor"

lb.drums

Ca(O

Cl)2

"4H20

Pota*s-ium

Purple

salt

Tast

e-od

orBulk,

Iron

,steel,

90-1

000.5

at70°F

98%

perm

anga

nate

control

barrels,

plastics

KMng4

drum

s

Acti

vate

d-Po

wder

edTasteodor

Bags,

bulk

Dry-Iron,

steel,

8-28

Insolu

ble

carb

onactivated

control

Wet-rubber,

sili

-(u

sed

asa

(:po

wder

ed)

carbon'

constainless

steel

116/gal

slurry)

Activated

Granular

Taste-odor

Bags,

bulk

Dry-Iron

steel,

.22-36

Insolu

ble

carb

onactivated

control

Wet-rubber,

sili-

(grafiul'ar)'

carbon

con

iron

,stainless

steel

Calcium

oxid

eQu

ickl

ime,

pHcontrol

SOlb

.bags

;As

phal

t,cement,

55-60

Slak

esto

75-99%

CaO

CaO

burnt

lime

,10

016

.ir

on,

rubb

er,

form

hydrated

chem

ical

barrels,

bulk

steel

lime

lime

,un-

(carloads

orslaked

lime

truc

ks)

Carb

ondioxide-

Carbon

phco

ntro

l,20

-50

lb.

Dry-iron,

stee

l63

.7at

0°F

0.0

3at

32°F

99.9X00

2C0

2dioxide

cylinders,

Wet-

rubb

er,

(liq

uid)

0.014

at68°F

10-20

orceramics

0.008

at104°F

18-20

ton

tank

trucks,

30-4

3-to

ntank

cars

-

Sodi

umchloride

Common

salt

,Sodi.

maBa

gs,

Bron

ze,

ceme

nt,

Rock

50-60

2.9

at32

°F

96%

NaCl

NaCl

salt

zeol'ite

re-

barrels,

bulk

rubb

erFine

58-70

3.0

at68

°F

gene

rati

on(carloads)

3.0

at86°F

Sodi

umhe

xa-

Polyphos-

Corrosion

100

lb.ba

gs,

Hard

rubb

er,

Crys

tal

78Hi

ghly

-67%

P205

meta

phos

phat

ephate,

glassy

inhibitor

100-320dr

ums

plastics,

stain-

Flake

81soluble

phosphate,

less

steel

Powd

er64

vitr

eous

phosphate

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CHAPTER 6

WATER TREATMENT PLANT WASTES

EM 1110-3-1629 Apr 84

6-1 . Quantities and characteristics of wastes . In connection withwater'treatment plant location and design, the disposal of the wastesgenerated during the various treatment processes must receiveconsideration . Among these wastes are sludge from presedimentationbasins, coagulation sludge, filter wash water, spent regenerant andrinse water from ion-exchange softeners, and mineral wastes fromdesalination facilities .

6-2 . Waste management .

a . Water-treatment sludges .

(2) Coagulation sludge .

(1) Presedimentation sludge . Presedimentation sludge may bedisposed of by returning it to the stream from which the raw water wastaken, provided the sludge is deposited in such a manner that it willnot impede flow . The sludge could be dewatered in lagoons or sludgedrying beds and then hauled to landfills or spread on land as analternative .

(a) Lagoons . If land is available near the treatment plant,alum sludge can be placed in lagoons to affect further concentration ofsolids . Depending on the local climate and the properties of thesludge, the final solids content in the lagoon may be as low as 1percent or as high as 17 .5 percent . Water should be removed from thelagoon by decantation . The decanted water may be returned to naturalwatercourses if deemed safe, and is sometimes returned to the treatmentplant for recycling . Lagoons should be of sufficient size to containthe sludge generated per day for 1,825 days (5 years), plusprecipitation less any decantation, evaporation, disposed sludge, orother losses . At least two lagoons should be provided so that freshalum sludge can be placed in one while the alum sludge in the other isallowed to concentrate . After sufficient drying, the sludge should beremoved from the lagoon and placed in a landfill or spread on suitableground . The minimum solids content which should be attained beforealum sludge can be removed from lagoons is generally about 10 percent .In colder climates, the freeze-thaw cycles to which the liquid in thelagoon is subjected will aid materially in concentrating the solids .Sludge lagoons should be enclosed by adequate fencing to excludechildren and animals .

(b) Discharge to sanitary sewers . Alum sludges may also bedischarged to sanitary sewers if disruption of wastewater treatmentprocesses is not anticipated . If this procedure is chosen, precautionsmust be taken to insure that the sludge does not create a hydraulic

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EM 1110-3-1629 Apr 84

overload in the sewers or form significant deposits in the sanitarysewer . Inasmuch as a large portion of alum sludge is notbiodegradable, the addition of alum sludge to wastewater will increasethe sludge production at the wastewater treatment plant . Disposal ofalum sludge to storm sewers is equivalent to disposal in naturalwatercourses and should not be attempted .

(c) Sludge beds . Another method of dewatering is applicationof the sludge to special sludge beds . These beds are usually composedof 6 to 12 inches of sand ranging in size up to 0 .5 millimeter, with anunderdrain system of graded gravel 6 to 12 inches deep . Drain pipes 6to 8 inches in diameter are placed in the gravel to carry away thewater from the beds . Sand beds can usually achieve a 20 percent solidsconcentration in alum sludge within 100 hours at a loading rate of 0 .8psf . However, the results are highly dependent on the characteristicsof the sludge and local climatic conditions . Warm, dry climates arebest suited to the use"of sand drying beds . The water passing into thedrain pipes should be suitable for disposal into natural watercourses .The dewatered sludge is usually removed from the sand bed by mechanicalmeans, but a minimum solids content of approximately 20 percent must beattained before mechanical handling is practical . After removal, thedewatered sludge is usually hauled to a landfill .

(d) Mechanical dewatering devices . Several mechanical deviceshave been used for dewatering of alum sludge, including pressurefilters, centrifuges, freeze-thaw devices, vacuum filters, anddual-cell gravity solids concentrators . Two or more of these processescan be used within the same system to obtain a higher degree of solidsconcentration than would be attainable using only one process .

b . Filter wash water . Wash water volumes range from about 1 to 3percent of the raw water processed . Disposal of filter wash water maybe by discharge to natural receiving waters, by recovery and reuse ofthe wash water, by lagooning, or by discharge to a sanitary sewer .

(1) Discharge to natural receiving waters . This means ofdisposal may be practiced if it does not affect other water usersadversely .

(2) Recovery and reuse . Recovery and reuse are accomplished bymixing the filter wash water with the influent raw water before or atthe rapid-mix basin . In most cases, the wash water is collected in arecovery basin from which it is pumped into the plant raw water inflow .Suspended solids in the wash water settle along with other solids inthe plant basins and the only wastewater discharged from the plant isthat associated with basin sludge removal . The recycling of filterwash water serves as a water conservation technique and may haveeconomic advantages over other means of disposal . In some instances,the suspended particles in the filter wash water may not settle outeasily, and recycling may, under some circumstances, cause abbreviated

6-2

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EM 1110-3-1629 Apr 84

filter runs . Another potential drawback of wash water recycling,particularly if the raw water has a high plankton count, is a build-upof algae In the recycled suspended matter and consequent increase oftaste and odor in the water .

(3)y Lagooning . Lagooning is an accepted means of managing filterwash water flows . If a separate lagoon Is used for the wash water, thesupernatant from the lagoon may be recycled through the water treatmentplant .

(4) Discharge to sanitary sewer . Filter wash water may also bedischarged to a sanitary sewer . Rate of flow. regulation generally willbe required to avoid sewer surcharge . This mode of disposal is mostapplicable if the characteristics of the wash water make it unsuitablefor recycling .

c . Waste brines . Two types of brine flows can be generated atwater treatment plants, regeneration brines from cation-exchangesofteners and waste brines from desalination processes . These brinesare very similar as far as disposal techniques are concerned . Methodsof brine disposal include regulated discharge to surface waters,"evaporation" pond disposal, and discharge to a sanitary sewer . Ifpond disposal is utilized, the ponds must be lined to prevent seepageof brine Into the ground water . Depending on the location of the watertreatment plant and the . volume of brine generated, these methods mayvary widely in cost, reliability, and environmental acceptability .

(1) Discharge to surface waters . Unregulated discharge tosurface waters is usually unacceptable . An exception Is that wastebrines from a desalting plant near the ocean can probably be dischargedto the ocean if precautions are taken in the design of the outfall toinsure that the brine is adequately diluted . On large rivers, It maybe possible to store wastes in watertight ponds during low-flow periodsand release them at a controlled rate during high flows . This may bean acceptable procedure if it can be shown that the wastes do notsignificantly affect water quality when released during the high-flowperiod .

(2) Evaporation ponds . Evaporation ponds can be used fordisposal of waste brines If evaporation rates are high, precipitationis minimal, and land costs are low . In most localities, precautionsmust be taken to insure that brine ponds do not overflow or leak intothe ground water . Watertight ponds are required for most situations .

(3) Discharge to a sanitary sewer . Disposal by regulateddischarge to a sanitary sewer may be practiced if wastewater treatmentplant operating personnel and regulatory authorities approve .Conventional wastewater treatment processes do nothing to removedissolved minerals from water . Hence, all of the dissolved salts

6-3

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EM 1110-3-1629 Apr 84

discharged to the sanitary sewer will eventually be present in theeffluent from the wastewater treatment plant .

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b . Population served .

c . System design capacity .

d . Preliminary treatment .

APPENDIX A

DESIGN EXAMPLES

A-1 . Clarification .. This design example is based on the followingconditions : river water source ; no softening required ; turbidity ofraw water is variable, but rarely exceeds 1,000 units . See plant flowschematic, figure A-1, showing two-stage clarification treatment .

a . .Facility to be served . The water treatment plant will serve apermanent installation .

- Resident

6,000- Nonresident

1,800- Effective population - 1,800 + 6,000 = 6,600

3

Capacity factor : 1 .42 (based on effective population)Design population = (1 .42)(6,600) - 9,372System design capacity, based on population = (9,372)(150)= 1,405,800 gpd . Use 1 .41 mgd - 980 gpm = 2 .18 cfs

Special design capacity for industrial processes,independently determined : 0 .79 mgdTotal system design capacity = 1 .41 + 0 .79 - 2 .20 mgd

- 1,530 gpm= 3 .40 cfs

(1) Rack and strainers . Provide coarse rack with 3-inch clearopening followed by hydraulically cleaned basket strainers with 3/8Inch clear openings ahead of each pump . Strainers sized to providevelocity of less than 2 fps through 3/8 inch openings .

(2) Pumps . Provide three pumps rated at 1 .10 mgd each . Thisgives firm pumping capacity of 2 .20 mgd . Maximum capacity is 3 .30 mgd .

(3) Meter . Provide Venturi-type flow meter in pipeline fromintake works to treatment plant . Meter should be sized to coverexpected flow range, minimum to maximum . Flow meter should be equippedwith flushing lines and bayonet cleaning rods .

(4) Presedimentation basins . Not required .

( 5) Aeration . Not required .

EM 1110-3-1629 Apr 84

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EM 1110-3-1629 Apr 84

TO SERVICEU . S . Army Corps of Engineers

A-2

INTAKE (WITH RACK AND. STRAINER)

FIRST-STAGE FLOW DIVISION STRUCTURE

SECOND STAGE FLOW DIVISION STRUCTURE

FIGURE A-1 .

FLOW SCHEMATIC WATER CLARIFICATION PLANT

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(6) Flow division . Normally, flow division is to be maintainedthrough the second-stage of treatment . Provide first-stage flowdivision structure with two identical rectangular weirs which willsplit flow into two equal parts . Hydraulic design of divisionstructure should be such that flow, corresponding to maximum pumpingcapacity (3 .3 mgd), can be carried through either half . Provide platesor gates so that either half of flow from division structure can bestopped .

e . First-stage mixing and sedimentation .

(1) Rapid mix . Provide two identical rapid-mix basins, eachproviding a detention time of 20 seconds at 50 percent of design flow .Volume of each basin is (20)(0 .5)(3 .4) or 34 cubic feet . Provide oneelectric motor-driven, rapid-mix unit in each basin which will yield aG value of approximately 700/second at a water temperature of 50degrees F .

(2) Flocculation-sedimentation . Provide twomechanically-equipped, circular flocculator-clarifiers, each sized for50 percent of design . flow . These units will normally operate inparallel .

- Detention time in flocculation zone : 30 minutes .

- Detention time in peripheral sedimentation zone : 3hours .

- Basin side-water depth : 12 feet .

- Flocculator depth : 10 feet .

- Flocculator volume = (30)(60)(0 .5)(3 .4) = 3,060 cubicfeet .

- Flocculator .area = 3,060/10 = 306 square feet .

- Flocculator diametver : 19 .7 feet .

- Volume of sedimentation zone : (3)(60)(60)(0 .5)(3 .4) _18,360 cubic feet .

- For 12 foot basin depth, sedimentation area = 1,530 squarefeet .

- Total basin area = 306 + 1,530 = 1,836 square feet .

- Upflow rate in sedimentation zone =

A-3

EM 1110-3-1629 Apr 84

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EM 1110-3-1629 Apr 84

( .5)(2 .2)(106) = 719 gpd/square foot or 0 .5 gpm/1,530

square foot, a satisfactory value

- basin diameter = 1,836_V 7T/4

Use double, V-notch, effluent weirs withlaunder .

Approximate total weir length, each basin :(48 .3 - 4 .3) (7r) (2) - 51 = 225 feet . The 4twice the distance of the weir from the tankfeet is the allowance made for non-effectiveas obstructions or supports .

( .5)(2 .2)(106)- Weir loading =

225

= 48 .3 feet

g . Second' stage mixing and sedimentation .

inboard,

= 4,890 gpd/feet

effluent

.3 feet representswall . Fifty-oneweir length such

Flocculator units should have variable speed drives which will yield aG value of approximately 50/second at mid-speed and a water temperatureof 50 degrees F . Provide piping and valves so that either basin can bebypassed while maintaining following secondary units in service .Provide basin overflow and basin cover structure if climatic conditionsrequire . Provide basin sludge withdrawal piping to point of sludgedisposal . Sludge pumps will be required if gravity sludge flow is notfeasible .

f . Second-stage flow division structure . Provide second-stage flowdivision structure identical to first-stage . This structure allowscombining the flows from the two, parallel-operating, first-stagesedimentation units followed by their division into two equal flows,which are then directed to the second-stage rapid-mix basins . Use ofthis flow-division structure provides maximum flexibility and optimumuse of plant facilities when one first- or second-stage rapid mix orflocculator-clarifier is out of service for repair or maintenance .

(1) Rapid mix . Provide two second-stage rapid-mix unitsidentical to those used for first-stage rapid' mixing .

(2) Flocculation-sedimentation . Provide two mechanicallyequipped, circular, flocculator-clarifiers identical in size to thoseused in the first-stage . These units will provide 30 minutesflocculation time and 3 hours sedimentation time . Total time forflocculation, both stages, is 60 minutes . Total sedimentation time,both stages, is 6 hours .

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h . Filtration . Determine number of filter units .

N = 2 .7 (Q)1/2

Q = 2 .2 mgd

N = 2 .7 (2 .2) 1 / 2 = 4 units

Filter configuration will consist of two filters, side by side, alongboth sides of a gallery sized to accommodate filter piping, valves,controls, etc . Main influent header pipe will. b e sized for a velocitynot to exceed 1 .5 fps . Calculated pipe diameter is 20 .4 inches . Use24-inch pipe giving actual velocity of 1 .08 fps . Use 12-inch pipes tosupply individual filters . At a rate of 2 gpm per square foot, totalfiltration area required will be 1,5 .30/2 or 765 square feet or 191square feet of medium area per filter . Provide 14 feet by 14 feetmedium area . Use dual-media filters with 8 inches of filter-gradesand, 4 inches of coarse sand, and 20 inches of filter-gradeanthracite, equipped with rotary surface .;ash capable of producing 0 .5gpm . Actual filter cells, including gullet, will be approximately 14feet by 18 feet . Use vitrified clay tile or similar underdrains andgravel layer as recommended by manufacturer . Provide rate controllersand filter level control equipment . Establish overall depth of filtercell at 15 feet . Assume an arbitrary operating floor elevation of 15feet . Significant filter elevations and related depths will beapproximately as follows :

Bottom of surface wash equipment (plus 2 inches) 4 .50

Bottom of troughs (plus 14 inches)

5 .67

Operating water level (7 feet above anthracite) 11 .33

EM 1110-3-1629 Apr 84

Depth of water above bottom of filter cell = 11 .33-0 .00 = 11 .33 feetFreeboard = 15 .00-11 .33 = 3 .67 feet . All four filters, each operatedat 2 gpm per square foot, theoretically will produce

A-5

Elevation (feet)

Filter cell bottom 0 .00

Top of underdrains (plus 10 inches) 0 .83

Top of gravel (plus 10 inches) 1 .67

Top of coarse sand (plus 4 inches) 2 .00

Top of filter sand (plus 8 inches) 2 .67

Top of anthracite (plus 20 inches) 4 .33

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FM 1110-3-1629 Apr 8 4

(4)(14)(14)(2)(1,440) or 2,257,920 gallons of water in 24 hours .Assuming two filters washed at 15 gpm per square foot for 15 minuteseach in each 24-hour period, wash water requirements will be(2)(14)(14)(15)(15) or 88,200 gallons for normal backwash, or about 4percent of production . Surface washing will require an additional(2)(14)(14)(0 .5)(15) or 2,940 gallons . Total downtime, each filter, isassumed to be 20 minutes . The theoretical net water production fordelivery to service will be as follows :

Under actual operating conditions, with the filter-rate and levelcontrol equipment specified, the filters remaining in service willautomatically compensate for production lost as a result of a filterbeing out of service for washing or repair . Level control insures thatfilter outflow will always match inflow .

In addition to flow and levelcontrol equipment, provide automatic filter shut-off and alarmequipment to be activated at maximum allowable clearwell level and alsoprovide filter high-level alarm . Provide all essential piping, valves,surface and backwash facilities, and operating consoles . Provideessential instrumentation for each filter . Provide sampling taps foreach filter . Plant layout and hydraulic design should be such thatadditional filters can be readily added as required .

i . Clearwell . Clearwell (filtered water storage) capacity shouldbe related to the available or proposed distribution system storage(ground and elevated) . As an approximation for this design example,clearwell capacity of at least 0 .6 million gallons could be provided .This is about 25 percent of the plant's daily production when operatingat 2 .2 mgd (design capacity) . Greater clearwell capacity may proveadvantageous depending on water demand patterns and plant operatingschedule . The clearwell is commonly located adjacent to the filtersand at an elevation permitting gravity flow to it . This usuallyrequires an underground structure . An alternative arrangement consistsof a sump following the filters, equipped with automatically controlledtransfer pumps,-which discharge to an above-ground tank or basin .Underground clearwells are commmonly constructed of reinforcedconcrete . For above-ground installations, steel tanks can be used .Regardless of the arrangement, the clearwell should be an independentstructure,'watertight, and protected against birds, animals, andinsects . Vents must be installed and protected against surface andrainwater entry, birds, insects, and animals . A protected,

A-6

- Theoretical total production 2,2'57,920 gallons

- Loss due to filter down-time 15,680 gallons

- Less wash water required 91,140 gallons

- Net theoretical productionavailable for service 2,151,100 gallons

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free-discharge, overflow should also be provided . The overflow mustnot be connected to any sewer or drain. Access to the interior of theclearwell is required . The access opening should be curbed at least 6Inches above the roof surface and be equipped with a hinged,overlapping, watertight, locking cover . As a general rule, theclearwell should be located at least 50 feet from sewers or drains .The area around the clearwell should be fenced and the site graded sothat surface drainage is away from the structure. Where winters aresevere, special consideration must be given to the design of vents andoverflows to prevent freeze-up as a result of vapor condensation . Awater level sensing instrument with readout In the plant control centershould be provided . This can operate In conjunction with thepreviously described maximum level control-alarm circulation andlengthened chlorine contact time .

Hydraulic profile . The hydraulic Interrelationship of majorplant units must be carefully considered . In general., the hydraulicdesign of the plant should be on the side of ample flow capacity sothat, under emergency conditions, water can be treated and filtered atconsiderably more than the normal rate with all filters In service .The approximate elevation data, given In the following tabulation,establish the emergency-operation hydraulic profile :

A-7

EM 1110-3-1629 Apr 84

LocationElevation(feet)

Water level upstream, first-stage flow division weir 100.00

Water level downstream, first-stage flow division weir 99 .00

(Loss : raw water pipe friction + velocity head in pipe 0 .42)

Water level In first-stage rapid-mix basin 98 .58

(Loss : rapid--mix to first-stage flocculator-clarifier 0.50)

Water level In first-stage flocculator basin 98 .08

(Loss : flocculator to sedimentation basin 0.01)

Water level in first-stage sedimentation basin 98 .07

First-stage sedimentation basin emergency overflow level 98 .57

(Loss : sedimentation basin weirs, launder and pipingto second-stage division structure 1 .50)

(Loss : second-stage division structure 1 .00)

(Loss :. division structure to second-stage rapid mix 0.50)

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EN 1110-3-1629 Apr 84

ElevationLocation

(feet),

Water level in second-stage rapid-mix basin

95 .07

(Loss : rapid-mix to second-stage flocculator clarifier

0 .50)

Water level in second-stage flocculator

94 .57

(Loss : flocculator to sedimentation basin

0.01)

Water level in second-stage sedimentation basin

94 .56

Second-stage sedimentation basin emergency overflow level

95.06

(Loss : sedimentation basin weirs, launder and filterinfluent piping

1 .80)

Water level in filters

92.76

Top of anthracite (7 .00 feet below filter water level)

85.76

Filter operating floor level (3 .67 feet above filter waterlevel)

96 .43

(Filter freeboard at second-stage basin overflow level

1 .37)

Bottom of filter cells (15 .00 feet below filter operatingfloor level)

81 .43

(Maximum loss through filter media, gravel underdrains,effluent piping and controls

10 .00)

Maximum water level in clearwell

82 .76

(Overall head loss during emergency operation :first-stage division structure - maximum clearwell level

17 .24)

By utilizing higher-than-normal chemical dosages, the plant can beoperated under emergency overload conditions and still produce watermeeting drinking water standards . In deriving the above data, thefollowing emergency conditions were assumed :

(1) All raw water pumps are operated, giving a raw water flow of3 .3 mgd, which is 1 .5 times nominal design rate .

(2) Both first- and second-stage rapid mix, flocculation, andsedimentation units on one side of plant are out of service .

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(3) Reference elevation of water in first-stage flow divisionstructure upstream from flow division weirs is arbitrarily establishedat the 100 foot mark .

(4) Raw water transmission pipe is assumed to be a flow divisionst-ructure to first-stage rapid mix with a 44 .5 foot, 16-inch pipehaving a C value of 100 .

(5) Plant units in service :

- Half of first-stage flow division structure

- First-stage rapid mixer and first-stageflocculator-clarifier .

Half of second-stage flow division structure .

Second-stage rapid mixer and second-stageflocculator-clarifier .

(6) Filters are to be washed when head loss exceedsapproximately 8 feet .

A-9

EM 1110-3-1629 Apr 84

All (4) filters, with filter level control equipment, etc .,operating normally .

k . Wash water . Water supply for filter backwash can be supplied bya special pump, sized to provide the required flow. If used, backwashpumps should be provided in duplicate . An alternative is an elevatedwash water storage tank providing gravity flow .

The-capacity of thistank should be at least 1 .5 times maximum wash water requirement for asingle filter . For this example, it is assumed that two filters willbe washed in succession, each for 15 minutes, at maximum rate . A watertank having a capacity of three times the wash requirement for a singlefilter is recommended . Its capacity will be : (3)(15)(14)(14)(15) or132,000 gallons . The wash water storage tank is refilled by pumpingfiltered water from the clearwell . Duplicate,automatically-controlled, refill pumps should be provided . A singlepump should be capable of refilling the wash water tank inapproximately 4 hours . A wash water rate-of-flow controller should beprovided on the main wash water line serving the filters . Rate of washwater flow and totalizing instrumentation with readout visible duringthe washing process should also be provided .

1 . Wash water recovery . Filter wash water can be recovered andrecirculated through the plant . Solids contained in the wash water areremoved in the plant sedimentation basins . Wash water recoveryrequires the construction of a basin into which the wash water isdischarged . The basin bottom should slope steeply toward the suctionpipe of the recycling pump . The capacity of the basin should be

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EM 1110-3-1629 Apr 84

approximately equal to the value of two, maximum rate, 15-minute filterwashes, or about 90,000 gallons . For an assumed schedule of two filterwashes every 12 hours, the recycle pump should have a capacity of about125 gpm so that the recovery tank will be emptied in about 12 hours .The recycle pumps should be provided in duplicate . The recovery tankshould be equipped with an overflow and a drain connection, bothdischarging to the plant waste disposal system . Under unusualcircumstances, associated with raw water quality, it may be undesirableto recycle wash water . For such a situation, the wash water can bedischarged to the recovery basin and then drained slowly to the plantwaste disposal system .

m . Chemical application . Table A-1 summarizes major features ofchemical application and related factors .

n . Chemical storage space . Chemical storage space requirementsmust be analyzed in terms of required application rates, shippingschedules and quantities . In general, a 30-day supply of a givenchemical, based on estimated average feed rate, is the minimum storagevolume that should be provided . If chemicals are purchased in bulk,the minimum storage volume available should be 150 percent of thevolume of one bulk shipment, or about 30 days of storage at averagefeet rate, whichever is greater . For example, if the chemical purchasecontract is for liquid alum, depending on local conditions, themanufacturer may elect to ship as follows : rail tank cars, 7,000 to10,000 gallons ; tank trucks, 3,600, 4,000 or 5,000 gallons . For raildelivery, minimum storage should be 1 .5 x 10,000 or 15,000 gallons .For tank-truck delivery, minimum storage should be 1 .5 x 5,000 or 7,500gallons . If the estimated average alum feed rate is 30 mg/l and theplant is operated at design rate, 2 .2 mgd, daily requirements, in termsof dry alum, are (30)(8 .34)(2 .2) or 550 pounds per day . Liquid alum,as furnished by the manufacturer, normally contains 5 .4 pounds of dryalum per gallon of solution . The daily alum solution requirement will,therefore, be about 102 gallons . A storage volume of 15,000 gallonsprovides about 150 days of storage at average feed rate and design flowrate ; a storage volume of 7,500 gallons, about 75 days . In thisexample, standard shipping volumes determine storage capacity . If thealum supply is to be purchased and stored in 100 pound bags, minimumbag storage space equivalent to (30)(550) or 16,500 pounds of alumshould be provided .

Loosely-packed, dry alum has a bulk density ofabout 50 pcf . The minimum bag storage volume should, therefore, beabout 330 cubic feet arranged so that bags can be handled and stored onpallets . Suppliers should be consulted in advance of design regardingshipping quantities, schedules, and costs . It may be possible toreduce overall-shipping and handling costs by providing plant storagecapacity that will permit the manufacturer to ship in largerquantities .

A-2 . Iron and manganese removal . Source of raw water - ground water,containing approximately 3 .0 mg/l of iron and 0 .'25 mg/l of manganese .

A- 10

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No sulfide present . The pH of the raw well water is 7 .5 . Laboratorystudies have indicated that iron and manganese oxidation andprecipitation can be readily accomplished by aeration and chlorination,followed by a short period of flocculation . (Prediction of theperformance of an iron-manganese removal treatment plant, based only onthe chemical characteristics of the raw water, is difficult due to thevariety of factors that can influence the removal processes . For thisreason, laboratory and possibly pilot plant tests are desirable priorto the design of the treatment plant .)

a . Facility to be served . The water treatment plant will serve anArmy boot camp . .

b . Population served .

c . System design capacity .

Capacity factor : 1 .43

Design population = (1 .43)(6,400) = 9,152

System design capacity, based on population =(9,152)(150) = 1,372,800 gpd . Use 1 .37 mgd

Special design capacity for industrial processes andlandscape irrigation : 0 .30 mgd

Total system design capacity : 1 .37 + 0 .30 =1 .67 mgd = 1,160 gpm = 2 .58 cfs

EM 1110-3-1629 Apr 84

d . Aeration . Provide flow-division structure followed by twonatural-draft, multiple-tray aerators . Flow is divided equally betweenaerators . Each aerator has a distributor tray, three coke trays, and acollector tray, with the coke and collector trays spaced 18 inchesapart . Dimensions of trays are 7 .5 feet by 7 .5 feet . Hydraulicloading is 10 gpm . per square foot . Each tray is filled to a depth of 6inches with 2 inch pieces of coke . The distributor tray orifices aresized and spaced to insure 2 inches of head on the orifices . In a mildclimate, aerators can be located outdoors where good, naturalventilation will be obtained . If severe freezing conditions arelikely, aerators must be housed and mechanical ventilation provided .Flow-division structure ahead of aerators must be designed so that

A-1 1

- Resident 5,200

- Nonresident 3,600

- Effective population = 5,200 + 3,600 = 6,4003

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EM 1110-3-1629 Apr 84

either aerator can be taken out of service for maintenance while plantcontinues to operate at full capacity . See figure A-2 .

e . Chlorination . Provide two identical solution-type chlorinators,each capable of applying up to 5 .0 mg/l of chlorine to the aeratedwater . For a 5 mg/l dosage, the total daily chlorine requirement willbe (5)(8 .34)(1 .67) or 69 .6 pounds of chlorine per day . Apply chlorineto effluents from aerators .

f . Flocculation-sedimentation . Provide flow division structure foraerated water and two identical, circular, flocculator-clarifiersequipped for mechanical flocculation and sludge removal . Flocculatorzone, located in center of the basin, should have a detention time ofapproximately 30 minutes at 50 percent of design flow . Peripheralsedimentation zone should have a detention time of approximately 2hours, and an upflow rate of approximately 0 .75 gpm per square foot(1,080 gpd per square foot) . These requirements can be met by aflocculator-clarifier basin with an overall diameter of 36 feet and aside water depth of 12 feet . Clarifier effluent should be collected bymeans of a weir and launder along the periphery of the basin . Aeratoreffluent division structure allows either basin to be out of servicewhile utilizing both aerators, or both basins in service while only oneaerator is operating . Provide basin overflow piping and sludgewithdrawal piping . Provide cover structure for basins if severefreezing conditions are anticipated .

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WELLS

EM 1110-3-1629 Apr 84

U . S . Army Corps of Engineers

TO SERVICE

FLOW DIVISION STRUCTURE

FIGURE A-2 . SCHEMATIC OF IRON AND MANGANESE REMOVAL PLANT

A-13

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EM 1110-3-162

A-. 14

9 Apr 84

Table A-1,. Chemical Application

' FeedChemical Storage Equipment Feed Points

Aluml Chemical storage area Dry First- andsecond- stagerapid-mix

Elevated hopper in Drychemical feeder room

Tanks in bldg . Solution

Ferric Chemical storage area Dry First- andsulfatel second-stage

rapid-mixbasins

Elevated hopper in Drychemical feed room

Poly- Chemical storage area Solution First-stageelectro- rapid-mix'lyte2 basins

orCombined filterinfluent

Chlorine4 Separate ventilated Solution 3 Rapid-mixroom in chemical feed basins and/orarea Combined filter

influentand,/orCombined filtereffluent

Potassium Chemical storage area Solution First-stageperman- rapid-mganate .- basins

Activated Chemical storage area Dry First-stagecarbon s area rapid-mix basins and

Combined filterinfluent

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Notes :

EM 1110-3-1629 Apr 84

1 Alum (or ferric sulfate), the principal coagulant, andassociated feed systems are critical to plant performance andwater safety . Therefore standby feeding facilities and amplereserve coagulant storage must be provided .

Alternative feed points are provided in the interest oftreatment flexibility . Normally, polyelectrolyte will be appliedat the first-stage rapid-mix basins ; but under some raw waterquality conditions, it may provide advantageous to feed anadditional small quantity, 0 .1 mg/l or less, of polyelectrolyte tothe combined filter influent . Polyelectrolyte, so applied, actsas a filter aid and improves turbidity removal by the filtrationprocess .

Chlorine and the chlorine feed systems are critical to theproduction of safe water . Standby chlorination equipment andample reserve chlorine storage space must be provided .

Alternative feed points are provided in the interest oftreatment flexibility . Normally, sufficient chlorine will be fedat the second-stage rapid-mix basins to provide a free chlorineresidual in the effluent from the filters . The residual is thenadjusted upward as necessary by application of a small amount ofchlorine to the combined filter effluent . Chlorine will beapplied to the combined filter influent only when little or nochlorine residual is present in the sedimentation basineffluents .

Alternative feed points are provided in the interest oftreatment flexibility . Activated carbon will be used on anintermittent basis, as required, for taste-and-odor reduction .When it is necessary to apply large quantities of carbon, itshould be applied to the first-stage rapid-mix basins . For sometast-and-odor conditions, the effectiveness of the carbon may beincreased by splitting the carbon dosage between the first-stagerapid-mix basins and the combined filter influent . When using asplit carbon feed, the bulk of the carbon should be applied to therapid-mix basins with no more than about 10 percent of the totalcarbon application going to the combined filter influent . Underthese conditions, it probably will be necessary to increase thechlorine dosage to the combined filter effluent in order toprovide disinfection and an adequate residual in the waterdelivered to service .

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APPENDIX B

LABORATORIES AND LABORATORY ANALYSES

EM 1110-3-1629 Apr 84

B-l . Minimum analyses for Army water treatment plants . The minimumnumber and frequency of analyses to insure drinking water of acceptablequality are determined by the size of the system and the treatmentrequired . The frequency of analyses must also be adjusted locally to

establishinghave-beenplant is anyplant is anyfrequencies

meet changing raw water characteristics . For purposes ofthe required analytical frequency, water treatment plantsdivided into two classes, Class A and Class B . A Class Aplant employing treatment beyond chlorination . A Class Bplant which provides only chlorination . Minimum analysisare listed in table B-l .

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EM 1110-3-1629 Apr 84

(where chemicaladdition isemployed)

Table B-1 . Minimum Analysis Frequencies

1 Where controlled .

2 The installation medical authority is responsible forbacteriological sampling of the potable water supply . However, insome instances (e .g ., dueNto the remoteness of medical laboratorysupport), it may be desirable to have bacteriological surveillancecapability available at the water treatment plant . Facilitiesengineering personnel should coordinate such instances with theinstallation medical authority to prevent needless duplication ofequipment .

U . S_ . Army Corps of Engineers

-

CLASS MINIMUM CONSTITUENT/ANALYSESA B ANALYTICAL FREQUENCY

R X 2/day Chlorine residualX X 2/day-plant, 2/week-system FluoridelX X 8/mon.th for first 1,000 Total Coliform2

population . One additionalsample/month for each 1,000additional population .

X X 2/month Total Plate Count 2X X 1/day Turbidity (surface

water)1/day Hardnessl1/day Alkalinityl

X X . 2/day pH% 2/month TemperatureX 2/month Calcium

2/month Total FiltrableResidue

1/week Iron1X 1/week

MIanganesel

X 1/day to 2/month Coagulation Test

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Government Publications .

Department of the Army .

APPENDIX C

REFERENCES

EM 1110-3-160

Water Supply, General Considerations .

1

EM 1110-3-161

Water Supply, Water Sources .

EM 1110-3-163

Water Supply, Water Storage.

EM 1110-3-164

Water Supply, Water DistributionSystems .

EM 1110-3-1629 Apr 84

TB MED 576

-

Sanitary Control and Surveillance of WaterSupplies at Fixed and FieldInstallations .

Nongovernment Publications .

American Water Works Association (AWWA), 6666 West QuincyAvenue, Denver, . Colorado

80235

Manual .

M3

Safety Practice for Water Utilities .