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<br />June 10, 1991
<br />:Mr. John Pritc~ud, To,.!i. 1-f.m2.ger
<br />Town of Grc.nby
<br />Page 2
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<br />The problem stems from the ":'ct that the backwash "'-ater from the .filters and sl''''sc
<br />from the tIlbe settlers ~ di...-ccted directly back into the I4W w-.uu pond wbicl:i. supplies
<br />the plant with w-.,.1er. Tn other words, the turbidity whiciL ~ plant is designed to :remove
<br />via. the.filte.."S and (';~,.;;;.... is n:::ycled back to the h=ad of the plant which degrdies the
<br />IaW water quality. The inter-relationship of the backwash pond, I4W wa%crpond and _
<br />Fnser :River I4W w-Gte: intUe will :equiIe th~t improvements be done to ;l1 th.-=. .-..
<br />. componems.
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<br />Enclosed is a. scnem:>rie plan .'iew of the Town's w-...ter treatment pT~"t wi:!i:l:i. shows the
<br />maior comTVInen1:S.. ,,~c,-,:,,"':
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<br />Water that is used to remove t."-e tu.o.-bidity and >....;;me:lt buildup in the filt:s (c:alled'-;;~;' - I
<br />back..'ZSb. water) is clli'ec'Drl to two smill bac....~-ash ponds'- These ponds also r~e i
<br />water from the c!~r.fler or tube s.-ctler basin. '\Vhe:l these baSins are dr;:ir.ed, the sludge i
<br />builduo in the bottom oi the h~.ns is r::moved and cili:ec::ed to the PO:lds. The b::.c1."W'"..sh. . !
<br />'water -;md clu'.u"ler liPi" ;::.."t-~ is wec:.:::! to a d..lversion .m.ati1.o1e. The di.e=:siell j
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<br />manhole splits the flew to ponds No.1 and 2. i
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<br />Wat:' ;:"om the ;onds ~ c:::pt'..!!e:i b. ml"~:'i=: pipe mcl is, ~<a.b., direc'"~ to the same
<br />:_-=',..._- ,;:.........;en .......'c-'-e "1"T'~~~_ ';..a_ prc-~..:5 ~om the ";;"e:::"'o- s----.-a ,.;:-.~t1:y
<br />~""~~'_,;;",I,, I ...~.... 10......... TY___... .......0.1.... .w.. ' ....,.::........ ~u._1"";,,,;............:..I._
<br />into the int:a..lce :e'''-~on DOlld. Sev~.J. roe:::i:5:c :>roblems have bee:::i. ide:J.ti:B.e:i ;:;:i~ the
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<br />baekl;.'aSh pollds. T.ce mes: seve.e preble:n is rh, the effe::ti:ve volume of the ponds is
<br />reduced be::au.."C of high ~ounci';''ater. Ground'i'o-'ate:' J3DS above the bottom. of the ponds
<br />wbi.ch effec:ively redu= the de-..enrien. time in the ponds.
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<br />Accoremg to as.built in..-=Onnation, the ponds are only four feet d~. The high
<br />~....ll:ldwarer in the polld also does llot ~Iiow the ai= sludge blrildup to de"""'''''. Toe
<br />COu.'\.9entional m,::ooo of d;.-.;.czeri!:g aIm slucge ror S:u,~l1 ~;:r:::to;- ~~:-~e:lt pla!lts is to
<br />isolate or,e cfthe ba.c:"';;1ash pollds and d:-..in the d......,"t water. rne coagcl...,t sludges are
<br />then allowed to dry through the:::al c:::r..ve=cr.. or ~-..,..j~a",. cycles b. the ~in.te.r ii::Le.
<br />Eec::..use of tile ~'gh g:OUD.ciw-~er, the 70"""11 has not bee.!l :ilile to de.~~r t:.1e coag-Jl~t
<br />sludge. As a res.:lr, the sludge has btlilt up ::;. the bottom of the ponds which, ago'n,
<br />reduces me volume aIld det::lticll time.
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<br />Eecall.."C or the s1:ert de::'::ltion times ~"'1 li1e bac:~;"2.Sh ponds, the wa:.:r coes not have
<br />e:lougb. Lime to se:-..l~ out me u.:~iciir-f and >=--=~ille::.:s th..at a..-e pr~~t i.1 t:..e bac1:';;c.sh
<br />W~~p... rr"\..:.. n~":"l.d ~_.:!:-'P tf':e."1 ;s di.~...:.~ fr.l:l.t'"..~y :-." .'!-o:.:a. ;':"I-ke ;~~c....":_,., 'l"'V"'!~.,...; ..'~':c'n'
<br />~. .L~ _.J .::...........,...., . -- -....... .........,J ~.... _.w:..: ._........\,,(.. J:"""~.'" "..LJ.
<br />supplies the pl~t ~~:h r;:.w ,;.-ate:-.
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<br />5C~!.~'':z.s~'::. ::.~ ?::::::::~ ~.~=:"~_ :r..c.
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