1. Of bacterial

Some ,'Importan:t.'

.,1,

;_. ,,,:'. ~:;,:,>-:.>~;;,~;.;~i:t~~-:':.~" . .:,L Sanitary field survey.of>~the:i;iource.,'':' whi

adjunc t to a complete 'Sanit;~r'y'~An~lysis~..'2. This is .C1 study of the history: and .env Ylmlll1'~",f'I

source that C3n provide' a 'PI1YSl'Qal pic.water cycle in relation' top t~ritJal.' " c"",.-,:-;...,~,,:"'."."-.:

3. !\ conp Iet e san it ary analys', '0' e ofcell y ovsr.a Ipngp. " .'(b) chemica1and(mi

4. A cons ide r atdonio .vol 'led in 'the'!.U

", 1 ~. ,'.

Basis of Judging Qual.it'y 'o{a:',groposed Wate~,

-'" .~..- - .. '

v- "',

.:.. ' ~,;'.I.(

, .'~'.'I \

.....

l;..~''7-'."""" "'''''i'''''-8Th ...,.....,,'. !~_~ :\ii' V1r!I}/~ ~" i\~~j''', '.', ,,:\;f.'~f~f;::}~~,~~f:~'>. " ..~., . ~. ,~."J~'CAlt.;;~i",Ii-',:;'"....._..,',.,>~;r3\i!t';;~:~f::~~;-:~~"\., :... .'. \.>-t."~

....'.': . '.'.,_-" .. ....... . -'~:.;~;;...

":~:.''':;.:J~,L.~:. : /, ..:

.. '. ~ti:-,;..;.: .

... :~~\:~'~: .. "":.:"':-:"

Def ini t icns : ," .: i" ";;, . : :i~~!."::;;j.. . .1. Potable "Water is one .t'hat do'e~:~p.o.y:;"qontaill~.~pj~ct~o,P~.b"l,p;"..... .

P9,11~ti on., " .... ' ...., \'.,"X ,84, :;Quali t y of Vlater Sources';, :' '..... '" \'... ...' :: .".l;eY,e}l~eryti~I?piBg of air in thesand. . -...... n. c. ' . " - '.

",; '.::~:~.,\ '

60 The sand bed is cleaned by temoving appro~imat~ly I inch of sandfrom surface of bede

Loss of head reaches a maximum.of 4 to 6.ft at whfuh time itis necessary to put the filter out of service and clean the :ped",

Flow rates are controlled manually by ~and-operated valveu inaccordance with ,flow indication and recordi~g instruments,...

Since a coating of organic matter (bacterial slime) play~ animpcrt ant part in the straining action of the fil ter mat, it usual-ly requires s~veral days during which the effluent is wasted intothe filter ;:ipe;'sq .

5. A normal period of operation between c~~anings should be 2 to 3monthr.or longer. .

1. Preparation of water before filtra;~f;,on usually consists of plainsettling only.

2. In. an ordinary slow s3nd filter nc provision is made for tho ad-di tion of any chemical s and no' coaqul ant is required.

3. Operated with Constant depth of 4 feet of'water on tho surfuco ofthe sand. This level is measured and maintained by an autolllaticdevice' which regulates the rate of f l owvto the iilter ,

4" Rate of flow is maintained ut 1':1 mgad with the most conmon ruto ofabout 1:1 mgad.

H. Operation an6 Control:

pumps or gravity conduits.3. Plain settling bas ins ,4~ Filters5. Clearw2ter Stotage basino

60

~.

: . ,,~..,-.:,I -"~::';.,:,-.,!.'-."_;..!:. -; :~I"'~)'..._....-;...;..-r ,.'I:~.i"'

..........

,: .' " ' "0'

1. Lenqt h to d'i amet er ratio should not exceed 60G~~. Per fo rat ions "- J./4 to' 1/2' inch):round in diamet.ez,3,,, Spacing of per f or at ions is 311" forl-1/4" tro"8"V for 1/2"40 Ratio' of t ot al area of perforations ':in unde rd ra in system to totalt~\

c ro ss-cscct Ione I area of laterals should not exceed 0.5 for 1.t2't~;C", "and 0..25 fc r 1/ 4~~~ ::;:;;.:::;\"

~j~ Ratio of total area .o f- per for at ions to entire filter area is .('O~ J;~!.to ,,003 squate inch/xq, ft of f il ter , .

6. Space laterals at 12":o.,c, ',.;'i7. Rate o f washing is ,6-,36:t/minute,'" Trend in us inq CDClI-Sersandwi th "

hiqhcr rates of washing and fi 1t.e r inq, , Y,'o. Cross-isect ional urea of Later al s gr~ater; than 2 -t imes sum ,of ,areas

of perf orat Iona , ,'::ft ,,;"}~"" ;i;:':, ;;, ;v< ~~:,', .: : ..~~i'" . . ":: Jl~P:,.:\' '.'" ....',. ~;:'.:':1 " .f: ~

Ty[)cs 0 f Underdr ai ns : - ,'{,~!,;,A::,':.',': , ~,::.:;,,',I,,J'.':,'\\~,',:.., ",','"." '".,,' "" ~",U;t:A ,,\,,~~,'1. Perforated pipes - ('onsis~~, ~f:c~~,~{ft.~,::,~~i~~if014,'iowhich are Tai~aChe~

series of latera}, pip~s;' pq~;forclt,ed'':'lt;::~'pw~r:'portion., " '2, Pipe ~nd strainers --:--'"simflar"~9'~n.O~f''?'fAted ,P\~,pes except that(~

~t:a 1ne'1'5 with small' op,el1,in:~:,:ar,?:~,~~,er;t)e~ 'lnili" Lateral's ,~t requl arint erval s. 'Y",'" ,

3, Ridge and valley -- consist'\'ofj)ara1l0t ridges' 'f concrete 8'I",to ' ;',12" o~c*, with l~":~forated brass ,sc,rcen"support d.between ridges

4~ Perforated pl at.es -- perf orat ed meta Ll Ic, p.Lates 't

'..~

1.

,'" '.'~

.' '. '. . ' , II .! '~'t'" :~.'

1. Since 'Wash water should not travel more than 3 ft Iat eral Iy, thetroughs are i'!eVer spaced more ,th,an ,6,fee~:, apa~~~ '" ' ,

2~ They are constructed, of concrete, , steel and' are of var Ious cross-sect icn, The U~shaped bot tomsiwr th vertical sides are cO,nunon',torconcrete troughDo " . . , '

3. The edge of wash water troughs' shal l be abQut ',~);):.,::~,.!(d) double unit., ; "Ce) doubIe fil t er .i;'

.,1./.'; .',

. . ';,'

prpe and aut.cmat.ical Iy 'mamt at n: (;J}'WJJ;~Q}]ml:i,~,t.~l~I~,~J)~tlj;~);:b~~g',~9~{",>inc rea ses " '" " ;, ~",;;;jf~' '~:,:t ~:i;dtt~t'\:Si,'v :i,.e;lqet:e,J'IIlilfed.'TheYare ' ~ISef ul i~; i~d~c91Ung'}c~ry,e.con.g;i;Vp,~::{~~:,t.S;:~~ri'ic~;~~\U~r":',a,~q\the '.ceas rt.y of WaShll1g." ",' ..~)7,:';Ji";;;~(1;/ ),;, ,': :

" . " , " ";" , '~~'),~.,~,I"~;,.~,~,';,.,:},,,';':?'";.. . ," , :.

, ,'C, , ,,,' .. - .. "i';,;' "" ,!,~.~",:.~.,'":,:::,~':,:,,.....' ,,'/ 7, . .~:'. .:~,",'";;l\~,;'!',,., . :}r-

N.

.../~/~ M~ Wash Water Troughs:

'" ' ,\2. Sand should be free from dirt, hard and resistant and preferablyof quartz or quart~ite: '

(a) effective size ... 0.35 to 0.5 nm, ~:"(b) uniformity coefficient ",,;,,:1..'35 to'l.'S mm,(c) thickness of sand Layer .':",24" to 9..6"

(a) hard, '(b) durabl.e'.tc) rounded ' ,(d) weigh about lCO pounds/cubiC f'oot.,(e) free 'from, flat" thin,. or long pf'eces "

.Many small size units,0.1 .... OL acres L ".. ,;'

Few but larger.sizes 'up to I acre

5. Subdivision'of units

'100-(125) ..:.150 .mgad4. Rates

3. Pre l irnfnaryTreatment

.'English '''.'' .', ;'r.qechanicalor AmericanLondon fiJ.t:~r~/'Je(;.9;,~~,::t::l~9$'exper iments -.:Albani:!fi~;~~:rS)n89~,:.,;:LittletF:all$' filter 19Cis",,~;~,*&i~~~~(~~:~~~ftyi';:;~,:J;:;;:.~11.~~{(~~0~~~~tig~~...",:"

nonp;:::-spmetimes" '

.. ",: .,i

65

Disadvantages are: high cost , inef.ficient operat ion, relatively poor"quali ty of result obtained. ,. ," .- . '.," . t', . . . -.

Pressure :filters are based~on's~,me p'dncipJe':as:"gravity type . ra-pid sand filters but 'the underd~?i~~.~:'i"gl:~V~ra~d SS;~~;~:\~;~'J:'Q,~Q?",th~:~./~l~:~Jsl'',u,nd~r' pres-sure , UnlIke the graVlty-tYRe\;~f;::lt~r~:~r"~lte"(poag:ul?t~d-?.water.1s' usual-ly appl ied di rectly .to fi1tE-}r'wy;~6~t/~'I1l~::x~~(lcJlq.~,9ula:1i:i6n"or: condi ...t ioni nq, They are used almostvexc Ius Ive ly en .swfl1)!J1ing/poo;ls, small

.later suppl ies, and for ~ndllst'rJa>l,~".,p~,:,::,p>p'se,s,". " i: .... ~ , .

...... ';~

,'\',

. redUged17. Iron:-:/~. Press~r~.: Filters:

few.. ',

I '~.l".

more f0ef,l\le~ti;""r0~oved sometimes,. , - , .

164 Odor and Tastes

brilliant.. ..... e

.clear but clogsreadily

15. Turbidity

30%14. Color remo~al

.g,ood,but irregular .'.~~le'sswel l.supervfsed

Jess than 5 ppm. orsometimes. zero

13, B~ctcrial r~moval

straining, sedimentationchemical .

straining, sodimen-totion, biolog~9allbiochemical' .!.

12~Theory of Filtration

0.2%-0.6% of filtered 1-4-6% of filtered waterwater. .

11_ Amount of wash water

reverse flow,,,;, every24hrs. 18-24-48inches (wash

. 10. Cleaning scraping and wash-ing inside C'r~outside filter1-3 months

4"_6" initial, 9i_12~final

9. Loss of Head 042 initial, 4-7ft.final.' .

1.58, Uniformity coefficient 2.0 - 2

JisDf!VLlntanos are: hiqh ccs t , inef'f ic ient operation, relatively poorQuality of r~sult obtained

Pressure filters arc based on same pr inc ipIr, as gravity type ra-pid sand filters but the underdrains, gravel and sJnd arC placed in~:ylj.ndr ic a I tanks and 'Nr! t er is passed t hrcuch tho f iltel'S under pres-aurc , Unlike the gravi ty-r y-c f i 1tel's, the' ccnqu l at od water is usual-ly ,li~llljcd c'Lrcc t l y to filter \\'i:;'I'.lllL 11Iixlll(! [loccuLltio)J orcol1cli-

-t.icnillO. Th oy :JrL~ us od u Imo s t cxcl us ivo l y C'1l ::;wirrulling pools, smu l lwut cr slll,'lies, nnd for indust rin I P.:PDSCS.,/'

!'Cn1cvcd someti.mes

more Ircqueut

brilliant.

Ics s t hau 5 ~)PIl1. orsometimes zero

~'()f'd but i rrcnu lurunless well sunorvlsud

s t r e in inn, sod i111(;II t uti allchemi C~Jl

rod uced

few

cIear but cluqsrCQdily

Unif crm. ,- good

straining, s dimon-t:;;t ion I lJ in loU iC ill ,b io ch emicn l

O.2%-~.6%of filtered 1-(-6% of filturud waterwCltcr

reverse flow - UVl:ry24 hrs. lO-~~-~Oinch-.;swash

~craping and wash-ing Lnsi doou t s idc HI tel'l-~~ mont hs

tv 2 . it i 1 d '7ft .1"-6" init iaI, ()'_.I~~'" 0" I nIl') , .,- .. . LIfinal f inn l

PressurE. Filters:../ '1".17. Iron16.. OC:OT anrl Tastes

is, JurlJid i.Ly

1.4. ''::;olo~rremoval

I?. Theory d' '~'iltrill:Inil

Ll , /,iIlOlwt of wash water

9. Loss DE Head

G. Unifo~mity coefficient 2.D - 2,5 - ~.O 1.5.35 - .60 mm,

12"-18" ura vel2~"..36" sand

65

c:.~r:i - C.35 1111','.

12" 0ravcl (3/t.1~21l)3'-6' sand,

Slow Sand--~-.~.

7. Sand, ;;;:.3.

60 Filtering M~t:rinl

.. I;\.1i

i:

"~

, i,,

(2) IGr.~ICL1-- slow act In. exnens ive , effective in low DB. -3, rxidizing ~0cnts:

(a) 3ilver -- extremely effective, slow acting, no tastes orodor, but ineffective for waters with organic matter.

(b) Caustic Lime -- for water with pH of 10 or ever.

2. foisons w~ich Teact with cdll to form toxic substances and kill byeither chcmica l poison ino or disruptive structural changes wi th inthe cell.

(0) Eeat -- by be i linq, for hous eho ld use only.(b) Ultraviolet Rays - rays ~re abaorbed by ptotoplasm of

the cell producing death by oxidation of the entymes.AdvBBt2ges.arc: (0) nc tastes or odors in water (b) nodanger of (verdosage.Di sadvant ar-cs: (a) more costly. than usihg chlorine

(b) for small private water supr.lies andbottling works only.

(c) Ultrasonic or nicrowaves -- not commerCially used for water.(d) VibrcJtions ,

1. Fhysical hctien - ~irect application of force or energy which des-troys orqa nisms :;

c. mGt~ods of disinfection or destroying organisms;

/ .".) . . f di . f . . ki11 b . , thr nc pr i mn ry arm or wat er n si n oct1011 IS to 1 act erIa ano usprevent waterborne disease.

B. Furpose:

4. Germicides -- chemic81 compounds or anything to kill micro-organisms,exclusive: of spores . Ultraviolet radiation and oligodynamicsilver are also germicidal.

S. Sanitizing -- rendering an article clean of any aesthetically ob-jectionable material plus removal of contamination.

6. AntiseDtic -- either germicidal or bcictericidal - prevent bacterialmult.i plscat ion,

1. Eactcricide -- anything that destroys bacteria (uot necessarilyspores)

2. Disinfectant -- chemical agent that destroys disease germs.3. Sterilization -- destructiun of all living organisms, pathogenic or

not.

h. :,-:efinit iorrs:Chapter ZIX. ,lISIf'F'SCTIC N-.-.--.

67

E. S;,hlorine Compounds Used:l~l,cnCiling powder (chlorinated 1Ir,1e,chloride of lime) produced by

fOCa'ii1g chlorine and Lime into rotating drum. About 6('%-7::'%CaCC2 tho active ingredient. It losses strencth rapi~ly in moistair; losscs l%/month in closcd containers. AI':~licationis bydissolvirig and f8eding i~ the form of n solution of 0.5 25% C12.The solution dernsit~ slud~e of CaC03 and inert m~terials.

2. Co lcium Hypocb Iorite, C.](0c1)2 j-"'j}], Perchloron -- manufacture ismorc complex than bleaching powder, commercial product about 70%- .... ! , - L1,. - L, 1 .......! ,.. ..... ., ......_ , .', ,...,.1 .....(" r- " 1 11+ ; A 11 1 _ ~

1. Little is known about it - for sometime it was thou~bt thit dis-infection may be dUG to the liberation of ntscent oxygen from thehypoch lorous acid mOCL) but this theory has lost support due tothe feet that chloramines which is also a disinfectant containno oxyqen ,

2. It is now believed that disinfecting action is probably due toinactivation of cell glucose, metabolizing system by oxidationof enzymes. Thus ch!orine destro~by urtiting with material ofcell (cell-enzyme combination), nttncking it and blocking futureactivity.

3. Hypochlorous acid and hypochlorites are specifically toxic tobacteria in ways t~at are ~istinct from oxidation. Just what thistoxic rC2cticn is has been the subject of various speculationand theories, Some recent work (:;recnand Stumff) indicate thatthe prim~ry rGsction is one between chlorine and a certain enzymeessential for b3ctcrial reproduction.

D. Mechanism of chlorine disinfection:

Ca) centrifuging(b) fi \ t r at ionCc) coacr.l e t ion and sediment at ion,

~. Mcchnnical Action - which remove but do not destroy o~gDnisms andpl~cing t~8m ~n less favcrablo environment:

(c) Bromine - Iodine and other halogens.(d) Hydrogen Peroxide - unstable, no taste and odor residual,

difficult to maintaic\~(e) Chlorine - cheapest and mo st common.

(b) Ozone - (03) -_ is an unstable gas that tend to break downinto ndrmal oxygen containing two atoms of oxygen per mo-Lec ule, In the process of breaking down, .it releases nas-c8nt oxygen which is active in oxidizing the organic mat-ter and 1n killing bacteria present in the water.Advantages: no disinfecting chemical remains (n the water,

odors, taste, and color are removed, inexpensive process.Dis~dvantnge3: cost greater than chlorination, apparltus

required Is complicated, absence of residual chemicalprovides no safeguard against subseq~ent contamination.

68

.....

',-.~:-.-:::--~--==,",==--'-"",~""''''''''''''''~-'----------''-----------'-----_._----~.------ --~-,--------- ~----- -:~::_::_:_-~=:::-:-::';:::-:::-':;::;-'~:--:-::--::-:":':":'~:_=:':"~"~:::"":-"-'-~';:'":~=-::-

"'...

1. Crthotolidine -- most widely used, not fco Ipr oof 'since some subs-tances in water like nitri t e; ferric compounds, manqani c COrn-pou~ds, organic iroft::,compound~, F~~qc.equto,se and a~gae tendto mer ease the appar ent :content, :of.;:cllroJ;in~.,.;. .' ". ' .

2. Icdemet rf c Method _..:.f:cr wi3t.ei;of: residua:!' Cihlp'r~ne gr,~ate( thanI ppmr Colorimetric method, of lodomet,ric' chlorine "det.ermi nat ionis al so ava il ahl e, .. , ;",'",)~~~;;~"::'"',":',',:t:>' :~, ." . - .' . , .

3. Amperometr I.c Method - only procedure knownit.hat will dd ffe rent Iat.e :between free chlorine and .free -chl cr ine combined with nitroqenouscompounds. The test is known as Laux !'flash" test 'and is a formof colorimetric test having standardized colors. Not applicablein presence of oxidized manqanese, .

4'1 Drop..Ddl.ut ion test -- rapid field method 'where chlorine cone en- ,tration are gr~ater than 10 ppm~,as . in .water-mam s.ter iHzat.Loni

G. Four Methods of determining residual chl~rine:

1. time of contact.2. concentration of organisms.3. concentration of disinfect~nt.4. tempcratureo5. nature of disinfectanto

F. Factors affecting disinfection efficiency:,

.',""" . "0

4. Chlorine Dioxide: - new method - bactericidal propert.Les may be asgret or greater than chlorine, important in water~ o~high alk~-linity, used for waters with phenol troubles, active oxidizing agent2-1/2 more available chlorine than chlorine gaS~

5, Chlorine-Ammonia: Used where water gives chl om nous taste and odor.

3. Sodf umHypochl.or ite CNaCCl)., manufactured by electrolysis of brines.Pr oduce s an aIkalLne sodium hypochlorite solution containing either3-5% or 10 - 16%by weight of available'chlorine. 'Practical,y1old-1 Ib , chlorine from 8 pounds ,NaC12'using up, to 400,,:,500 ampere - hr s,70-90% effective. Maybe purchased from'manufacturet'or made.direct-ly at pl ants, latter method seldom used now. .Available only forlarge plants which prefer'liquid chlorine. GQO~ '1cii isolated regionwith cheap elettric power. Application of dilutlon is by solutionfeeders~ Advaptages are: simple'dosing equipmentl no sludge, 'hfgh inert per cent aqe but it cannot be,' shipped far economicallyand loses strength when storede

also yiel~s sludgenot so hygroscopic as bleaching powder~dry feed difficult ~ltho~gh practicable.costs more but allows storage and higher strength per pound'and al so stabl.e, . .f

(a)(b)(c)Cd)

69

.... -'

......~ ...........-~...-~~.-."'"" ...-.._'--

Chlorine Man:J} - Chlorine InstituteChlorine EGndbook - Diamond Alkali Co.

Re rer enccs :

(c) s~ronger bacterial effect.(d) longer periods of persistence of the bactericidal

effect~(e) reduction of chlorine requirements.(f)' a reducing action which r ender s its effects in-

dependent of the pre5ence of organic matter~(g) less irritation of the eyes and nose, resulting

in its use in sWimr,lingpool s,(h) cperators, no lcnger fearing to overdose with

chlorine, will feed an a~equate dose.(i) fre~dom fro~ dan]er of overdosage.

71

..,!-.~~.~~~,. '-),:,""~~~-;:r.l:_!.~"~

", M_._ _.., __ ~ ,~ ~._. _ _ n.__. ~_~_.". __ -... _._- ~_ -._

Diffusion

, '1. Temperature of the water.2. Saturation deficit or surplus of gas in water.3. {-irea of contact surface per unit volume of water.

. .F, Factors .det ermi nt nq effecti veness or Aerators.::'

. ,- .c .' _.,,- ,-.:-;"':

Aeration is usually asso(}Aat~q ..\~.itt:PllrJfjic~t.ion. Somet.Imes aera-t?rs are placed only for psYc~H)~o9~CaL',ef~~c:t~.:::At"time,s ::it is jU5-t if l ed also for, no ct,her r eason+t.han to .enhance the attractivenessof the water treatment pl ant , .. ' .. .' ,.: .... ".,' \

1. Oegree of under-saturaticn of water with respect to the gas, orsaturation deficit.

2, Temperature.3. Extent of intermingling of water and g,a5j L, e., the extent to which

int imat e contact ~is ach ieved and to which' immobile film~ are pre-vented at the ga,-watcr inter~aceQ .

110 Total amount of solution depends on time .of cont.act ;

E. Aesthetic Consideration:

The concentration of gases in a liqUid will come to equilibriumwith the atmosphere w_ith which the liquid is in contact in a.ccordancewith Henry+s Law. : So that if a water containing gases is placed incont(lct with an atmosphere other than that with which it is in equi:-Libr ium, B"11 exch~:1ge of gases b~twce~ the wat er and the atmosphere nn..m:"':"i~tely starts and will ccnt inue unt il Eiquflibrium rs reached. '.l:'hesol ut ion may absorb or give up gases depending on whether it is super-saturat ed or under sat urut edo- SOLUBILITY THEOOY.

D: Solution of G'a'B&s~i'" . .The rate at which a ga~ will be 'absorbed in water depends on the

following factors:

c. Theory of Aeration:

(a) Inka(b) Simplex Brush

\

5. Others

(a) Aero-mix(b) C::1'Irit ator(c) Diffusair(d) Others

4. Proprietary Devices

(a) Perforated pipes .(b) Diffusers(c) Air lift pumps.

3. Injection Aerators - air blown into water} as bubbles.

'!

',fiti!....-._._.'._-'_'---" ..~-..--...- .'._.,.,._-----_. __ .__ .._--_ ..__._...... _...,_ ....'....;;-;.............. :._,.

74

Reference:Taste & Cdor Control - Industrial themical Corporation_

'.

(b) slow ao it at ion for 30 to cC minutes to a l Lowcomnl et ion .;

I!

'.~ ,.r, ' ... )

(a) addition of softening and. coagulating -chemi cal s and followed :4.~!~by thorough mixing 'of the. chemicafs wi th water' .,'. , ... '.. '." .. ' ,. . ...

It :.!

i ~.

,;, ,

1. Lime-Soda Pr oi.es s -- this precess ;CP,l}sj,Sts.;of the fo11owiI19,,,steps: " " ::i'~, '.\ .' .'.'"

1. conservation of. spap.,2. reduction cf work~i~t~e laundry.3. prevention of' t.he Jor,mation' ot scales in steam bof l ers,4. p repar at ion of w'at,~r:\for domestic and industrial ~uses ~5. increases efficiencY; of:fi1iraiion~'" " '\ ;;., .' .":6. aids in the removal: of':C!;:: .8. improves the cook inq of foods and is, des ir ab l e for other, domestic

Purposes ',', i-""';:i"":', .. : .: ...,,, . " . ' (:'1,9. increases the efficiency of'\i'~~i9!,,~,!.j}~tr,~Al\9tion When filtr.ation

follows soft en inq, ... ',::,;-:'i,.;:/::>.';>-:. ," -. .' '".,\C, Two General methods Of

(h)

(b)(c)(d)(e)(f)(g)

high opcratInq. '..' .of the reo.u{r,~,d/eglifreedom -.from,tag ..,'~,"',""':,'r c.." ':r.';:;".:;,,,7.;,,.;.;, '.""freedom fromi,'.;j , ....'.J:""" ..,.'."low salt reqlii .avat Lab i l l t y.und ... ' , .dur ab i l ity ,to res is '.... , .. ' 're;wash~ng#freedom from the efJ~'9:t~" of! ...' , ' .

(b) temporary storage to perrni t' discl~arg~'":i:-:t 0, the stream duringhigh-water period , , '. ?, i",'~:'!',; ~ ,the filling of depressions or "excavat ions , as old quarries.the eli scharge into the city sewer s ," throuqh 'the sewage treat-

ment .pl ant , ' .' , .dr y i 111 the sludge and using it for liming, the so,il~reburning for, the production of Lime, i,use as a filler for paintsg

. '3. Disposal of sludge 'accumulated in>the 'lime-soda> process:

2. Types of Pl ant Oper at iom.

(a) continuous type plant -~ continuous appligation of chemigalsduring. the hour the. plant is in operation>. ,The constructioncost is less than other type -- most municipal plants are .of this type,

(b) Intermittent type - consists 'in ba tch or fill-and,..drawoperation in wooden, steel, :,'01' conc re t e tagl.cs';'pf any con ...venient shape, from wh Lch sludg~ ~s,'w~th~~:~wn eithe r; by.grc)Vity'in a conical (Irpyrami~.Fl~~~~.ap~d,:bottom or-bymechanicalsl,;;.capers from flat';';bottom;;ttqnks~:; " .

(c) Conventional type' plant -,;. when;'ch~m!ca~'lyttrcated water .is.mixed andvs et t l ed in separate tanks;;:'P

G. ::':::::::: :: :::e:;:::5::g\;;!~;~~~~~~~;;'~::,(::,~;~ti:,. , .'1. sui table for t.urbfd;: C~li3Jype,a,te':) , , ;:'9I,;ior'W,a:t~r'where zeo If te cannot

be used. " ,:,j;;,:;:;{"f;". 1;,,', ~i,W:Pi;;~;Jff)'i+':":~;?;,", "2. the effluent ccnt a Insi.I'o: er,i~i0 "s,o,lid.s/than" that from zeolite

softening. '" ';>~>: ' "",">':i);;!::;1;:i;;~}!(\:1~;, > ,:'{,:'Y:;r

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