XLNT Quy mo nho

8/7/2019 XLNT Quy mo nho

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PGS.TS Trn c H

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Cng ngh v cng trnh X l nc thi quy m nhTS.Trn c H

.1. c im h thng thot nc thi quy m nh.

.1.1.H thng thot nc thi phn tn .i vi nc thi th , dng thot nc c th l tp trung hoc phn tn.

Khi thot nc tp trung , nc thi t cc tuyn cng cp 2 ( tuyn cng lu vc )a v tuyn cng chnh ( tuyn cng cp 1 ), sau bm v trm x l nc thi tptrung . Nh vy nc thi s c dn ra khi khu vc th , x l n mc yu cu , sau x ra ngun nc mt c kh nng t lm sch ln. Dng thotnc tp trung m bo cho mi trng c an ton cao , t b nhim. X l ncthi (XLNT) tp trung d kim sot v qun l. Tuy nhin vic u t thot ncthi tp trung rt tn km do vic xy dng tuyn cng chnh ln, di v su, slng trm bm chuyn bc nhiu ... Mt khc khi th pht trin khng ng b

theo khng gian v thi gian ,vic xy dng trm XLNT tp trung v tuyn cngchnh s khng ph hp. u tkinh ph ln ngay t ban u cho cc cng trnh nyrt kh khn.

Trong cc th ln do kh khn v khng kinh t trong vic xy dng cctuyn cng thot nc qu di khi a hnh bng phng v mc nc ngm cao,ngi ta thng quy hoch thot nc thi thnh h thng phn tn theo cc lu vcsng, h. Do c im a hnh v s hnh thnh cc knh h trong cc th ncta, h thng thot nc thng phn ra cc lu vc nh v c lp . Thot ncphn tn s l hnh thc ph hp i vi a s th nc ta. Cc trm XLNTphn tn thng l loi quy m nh , cng sut t vi trm n vi nghn m3/ngyhoc quy m va cng sut t 2.000 n 10.000 m3/ngy. Xy dng cc trm XLNT

cho cc th nh v cho cc lu vc c lp ca cc th ln, hoc cc trmXLNT bnh vin, cc cng trnh cng cng, dch v... quy m cng sut t 50 n500 m3/ngy s tn dng c cc iu kin t nhin cng nhkh nng t lm schca sng, knh, h chuyn ho cht bn. Mt khc vic xy dng ny cng phhp vi kh nng u tv s pht trin ca th. S nguyn tc thot nc vXLNT phn tn c nu trn hnh .1. Nc thi sau khi x l t tiu chun chophp c x vo cc cng thot nc chung hoc cc sng, mng, h trong khuvc.

Trong nhiu trng hp mc XLNT ca h thng thot nc phn tn yucu khng cao do tn dng c kh nng t lm sch ca cc sng h . Tng githnh u t cho h thng thot nc thi phn tn gim xung do khng phi xydng cc tuyn cng thot nc thi tp trung. Cc cng trnh ca trm XLNT phntn thng c b tr hp khi, d vn hnh v qun l .

Nhc im chnh ca h thng nc thi phn tn l d lm mt cnh quando vic xy dng trm x l nc thi bn trong th. Nu thit k thi cng v vnhnh trm x l khng ng cc yu cu k thut, nc thi c th gy mi hi thi ,nh n mi trng khu dn c v th xung quanh. Mt khc nu hm lng ccnguyn t dinh dng nh N v P trong nc thi sau x l cn cao, trong iu kinquang hp tt, cc sng h th tip nhn nc thi c th b ph dng

(Copyright Vietnam Water Forum - www.VinaWater.org)


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(eutrophication) v dn n nhim bn th cp. Mt s kt qu nghin cu /8/ chothy, trong cc sng h tip nhn nc thi th hm lng cht hu c (tnh theoBOD5) b sung do nhim bn th cp thng dao ng t 1,4 n 4,5 mg/l. Cc trmXLNT phn tn c quy m , mc v cng ngh x l khc nhau . Vic kimsot, qun l vn hnh chng rt phc tp. Tm kim t ai cho vic xy dng trm

XLNT trong ni thnh thng rt kh khn . T chc thot nc phn tn thngthch hp cho cc th c h thng thot nc chung hoc h thng thot nc naring, nm trong cc vng a hnh bng phng nhiu knh, h. V d h thng thotnc thi H ni c chia thnh 7 vng theo phng n quy hoch ca T chc hptc Quc t Nht bn (JICA) nm 1994 hoc thnh ph lt thnh 4 khu vc theoD n thot nc v v sinh nm 1999 (hnh ..2) .

Ngun nc sch b cp pha longnc thi trong h thng knh h

Lu vc 1

Ging tch nc

Nc ma

Nc thi Trm XLNT 1

H 1

Lu vc 2

Ging tch nc

Nc ma

Nc thi Trm XLNT 2

H 2

Lu vc i

Ging tch nc

Nc ma

Nc thiTrm XLNT i

H i

H u mi

Hnh .1 S nguyn tc t chc thot nc v XLNT phn tn .



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.1.2. H thng thot nc thi cc b.Trong trng hp cc i tng thot nc ( cm dn c, cng trnh cng

cng, dch v, nh ...) nm v tr ring r, c lp hoc cch xa h thng thotnc tp trung, ngi ta thng t chc h thng thot nc thi cc b kt hp xl ti ch. H thng thot nc thi cc b c th c ng cng hoc khng c

ng cng. Nc thi sau khi x l m bo tiu chun v sinh mi trng, ccho thm vo t , thi trc tip vo sng h ln cn hoc s dng ti cy, nuic... Trong mt s trng hp ,trc khi x vo cc ng cng thot nc tp trung,cc loi nc thi c cha vi khun gy bnh dch hoc cht bn c bit ( nc thibnh vin, nc thi cng nghip...) phi c kh trng hoc kh c trong cccng trnh x l cc b, m bo iu kin khng nh hng xu n hot ng cah thng thot nc th v sc khe ca con ngi khi tip xc vi n.

Nh vy, cc trm XLNT cc b thng c xy dng i vi cc trnghp sau:

1.Cc th trn, th t c quy m dn s di 50.000 ngi .2.Cc cm dn c, khu nh , ngi nh hoc cng trnh cng cng, dch v

nm ring r, cch xa h thng thot nc tp trung .3.Cc cng trnh cng cng, dch v c yu cu x l c bit nh bnh vin,

b bi ...Cc trm XLNT cc b thng c cng sut t vi chc n vi dm nghn

m3 trong mt ngy. Trng hp th nht thng l cc trm x l nc thi quy mva ( cng sut t 1000 n 10.000 m3/ngy ); cc trng hp th hai v th ba lcc trm quy m nh (cng sut di 1.000 m3/ngy). T chc thot nc khu vcLinh m - nh cng- Php vn pha Nam H Ni l mt v d v cc h thngthot nc thi cc b cho cc trng th hai. Mt s th ( v d thnh ph lt, Hi dng, Vnh yn ... ) c th t chc thot nc theo h thng hn hp ph

thuc vo a hnh, ch thu vn sng h, c im s dng n

c.....X l nc thi ti ch vi cng trnh ch yu l b t hoi hoc b lng haiv rt thch hp v cc ngi nh, cm dn c hoc cng trnh cng cng ring r,cch xa mng li thot nc tp trung. Cc cng trnh ny va lng nc thi kthp ln men cn lng nn hiu qu x l cao, qun l vn hnh n gin. Nc thiv bn cn sau qu trnh ny c th tip tc x l trong t, ao h hoc ti s dng ti rung v lm phn bn. Tuy nhin do cng trnh b tr gn nh v khu dnc nn iu kin v sinh ca n cn hn ch.



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Khu vc Thi phin

Nc thiB t hoi Bi lc ngm

ti hoara sui

Khu vc p Chi lng

Nc thi B t hoi Bi lc ngmh Than th

Khu vc h Xun hng H Xun hng

Khu vc sui Cam ly

1 2

Khu vc trung tmsui Phan nh Phng

Thc Cam ly

Hnh ..2. S t chc thot nc thnh ph lt n nm 2010.1.Trm bm thot nc tp trung; 2.Trm XLNT Q=11.000m3/ngy



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.2 S lng, thnh phn v tnh cht nc thi ca cc i tngthot nc quy m nh.

.2.1. Cc loi nc thi ca cc i tng thot nc quy m nh.Cc loi nc thi sinh hot c hnh thnh trong qu trnh sinh hot ca con

ngi. Mt s cc hot ng dch v hoc cng cng nh bnh vin, trng hc, nhncng to ra cc loi nc thi c thnh phn v tnh cht tng t nh nc thisinh hot. tin cho vic la chn phng php dy truyn cng ngh v tnh tonthit k cc cng trnh x l nc thi quy m nh, nc thi sinh hot c phnloi theo cc du hiu sau y:

a.Theo ngun gc hnh thnh, trong cc h gia nh c th c cc loi ncthi sau y (hnh .3) :

Ngun nc thi t cc ngi nh

Nc thi phn Nc tiu Nc tm, git, ra Nc thi nh bp Cc loi ncthi khc

Hnh .3. S hnh thnh cc loi nc thi trong cc ngi nh hoc cng trnh cngcng.

Cc loi nc thi c hnh thnh theo s hnh .3 c s lng v thnh

phn v tnh cht khc nhau.Tuy nhin thun tin cho x l v ti s dng, ngita chia chng thnh ba loi:-Nc thi khng cha phn, nc tiu v cc loi thc phm t cc thit b

v sinh nh bn tm, chu git, chu ra mt.Loi nc thi ny ch yu cha chtl lng, cc cht ty git v thng gi l nc xm . Nng cc cht hu ctrong loi nc thi ny thp v thng kh phn hu sinh hc. Trong nc thinhiu tp cht v c.

-Nc thi cha phn, nc tiu t cc khu v sinh (toilet) cn c gi lnc en. Trong nc thi tn ti cc loi vi khun gy bnh v d gy mi hithi. Hm lng cc cht hu c (BOD) v cc cht dinh dng nh nit, pht phocao. Cc loi nc thi ny thng gy nguy hi n sc kho v d lm nhim bn

ngun nc mt. Tuy nhin chng thch hp vi vic s dng lm phn bn hoc tokh sinh hc.

- Nc thi nh bp cha du m v ph thi thc phm t nh bp, my rabt. Cc loi c hm lng ln cc cht hu c (BOD,COD) v cc nguyn t dinhdng khc (ni t v pht pht). Cc cht bn trong nc thi ny d to kh sinh hcv d s dng lm phn bn.

Mt s ni ngi ta nhm hai loi nc thi th hai v th ba , gi tn chungl "nc en".



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b.Theo i tng thot nc, ngi ta phn ra 2 nhm nc thi:-Nhm nc thi cc h gia nh, khu dn c.-Nhm nc thi cc cng trnh cng cng, dch v nh nc thi bnh vin,

nc thi khch sn, nc thi trng hc, nc thi nh n.Mi nhm, mi loi nc thi c lu lng, ch x nc v thnh phn

tnh cht c trng ring.c. Theo c im h thng thot nc s hnh thnh nn hai loi nc thi:-Nc thi h thng thot nc ring. Nc thi t cc thit b v sinh c

thu gom v vn chuyn v trm x l theo tuyn cng ring.-Nc thi h thng thot nc chung. Cc loi nc thi sinh hot (nc

xm v nc en) cng vi nc ma t u trong khu vc thot nc c thugom v vn chuyn theo ng cng chung v trm x l. S lng thnh phn vtnh cht nc ma t u trong cc khu dn c th c nu trong ph lc.Trong mt s trng hp nc en c x l s b ti ch qua cc cng trnh nhb tch du m, b t hoi , sau cng nc xm x vo tuyn cng thot ncchung ca thnh ph.

Vic phn loi nc thi theo h thng thot nc ph thuc vo i tngthot nc, c im h thng thot nc ca th hoc khu dn c v cc iukin t nhin, iu kin kinh t x hi khc ca th.

.2.2. Lu lng nc thi v ch thi nc .Lu lng nc thi trong mt khu vc th, cm dn c, ngi nh hoc

cng trnh cng cng c xc nh trn c s tiu chun dng nc. i vi khuvc dn c, tiu chun thi nc t 120 n 180 l/ngi.ngy, xc nh theo Quychun xy dng Vit nam nm 1996/1/. Tiu chun thi nc bnh vin thngthng c xc nh theo ''Tiu chun thit k bnh vin a khoa'' (TCVN 4470-87 )l 300 n 400 l/ng.ngy. Tuy nhin theo kt qu nhiu nghin cu / 7,8 / cho thy ,

do s l

ng cn b cng nhn vin v ng

i nh n chm nom bnh ln, tiu chundng nc thc t tng ln rt nhiu v n cng ph thuc vo quy m cng nhchc nng ca bnh vin , dao ng t 500 n 1000 l/ging.ngy. d xc nhlu lng v nng cht bn trong nc thi sinh hot ca cc cng trnh cngcng hoc dch v ngi ta thng tnh ton, chuyn i cng sut (quy m) cngtrnh sang ch s dn tng ng. l s n v phc v ca cng trnh cngcng, dch v c lng cht bn hoc nc thi x vo h thng thot nc tngng vi ca mt ngi dn th. Cc i lng tng ng ny ca mt scng trnh cng cng v dch v c th xc nh theo bng .1 sau y.



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Bng .1. Ch s dn tng ng v tiu chun nc thi ca cc cng trnhcng cng, dch v.

Cng trnh n v tnh Ch s dntng ng

Tiu chun thi nc,l/n v tnh.ngy

-Khch sn, nh ngh-Nh n-Qun c ph, gii kht-Cu lc b; nh vn ho-Trng hc-Nh tr-Bnh vin

GingCh ngiChCh

Hc sinhTr em

Ging bnh

1315

51010

230,40,5

200-30050-8010-158-2515-2550-100300-600

Mt yu t c bn khc lin quan n vic tnh ton thit b mng li thotnc v cc cng trnh x l nc thi l ch thi nc. Lu lng nc thi chyn cc cng trnh x l nc thi quy m nh khng n nh trong mt ngy m

(hnh .4) cng nh trong tng ma. Ban m do t thit b v sinh hot ng, lngnc thi rt nh. Trong thi gian cao im, lu lng nc thi c th ln gp 6-8ln thi im trung bnh. Trng hp nhiu thit b v sinh cng hot ng ng thith nc thi chy lin tc ti trm x l. Ch thi nc c trng bng h s thinc khng iu ho chung Kch. l t s gia lu lng nc thi trong gi dngnc ln nht ca ngy dng nc ln nht (qh,max) vi lu lng nc thi trong gidng nc trung bnh ca ngy dng nc trung bnh (qh,tb). Nhvy:

tbh

hch

q

qK

,

max,= (.1).

0

2

4

68

10

12

14

16

0 4 8 12 16 20 24

A B C

Hnh . 4. Biu thi nc khu dn cA- Th t; B- Khu nh 200 ngi;C- Khu th 50.000 ngi

Gi tr Kch ph thuc vos ngi s dng h thng thotnc, tiu chun dng nc,iu kin trang thit b v sinhv iu kin kh hu. Lu lngnc thi cng ln h s Kchcng nh. Da vo h s Kch cth xc nh c lu lngnc thi tnh ton ca h thngthot nc v cc cng trnh xl nc thi. i vi h thng

nc thi quy m va v ln, hs Kch c th xc nh theo cccng thc sau.

tbch QK 5,25,1 += ( ..2).

Trong : Qtb -Lu lng trung bnh, l/s



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Thng thng cc cng trnh x l nc thi quy m nh, lu lng nc tnhton Qh,max bng khong 1/10 lu lng ngy m Qng.

Ch thi nc ca bnh vin khng n nh theo thi gian trong ngy,trong tun v ph thuc vo cp v quy m bnh vin. Thng thng, lng nc sdng ln nht vo u gi bui sng khi bnh nhn dy v bt u qu trnh khm

bnh. H Kch ca bnh vin thng ln hn ca khu dn c vi tiu chun cp nctng ng t 2 n 3 ln.Theo cc tiu chun thit k cp thot nc hin hnh, hs Kch ca bnh vin l 2,5. Cc yu t k trn nh hng r rt n vic tnh ton,xc nh cng sut cc cng trnh thot nc v x l nc thi cng nh thit lpquy trnh qun l, vn hnh chng.

.2.3. Thnh phn v tnh cht nc thi.Cc ch tiu c bn c trng cho thnh phn cc cht bn trong nc thi

sinh hot l hm lng cn l lng (SS) , nhu cu xy ho sinh hc (BOD ), nng nit amn, s coliform.... Lng cht bn tnh theo ch tiu cht l lng, BOD5 ... domt ngi trong mt ngy x vo h thng thot nc sinh hot ca mt s ncc nu trong tiu chun xy dng ( 20TCN 51-84 ) . i vi cc ngi nh hoc

cm n c c lp, hm lng cc cht bn trong nc thi sinh hot c th xcnh theo bng .2.

Bng ..2. Ti lng v nng cht bn trong nc thi sinh hot t cc ngi nhhoc cm dn cc lp / 25,28 /.

Thng s Ti lng ,g/ngi.ngy

Nng * , mg/l

Tng cht rn 115-117 680-1.000Cc cht rn d bay hi 65-85 380-500

Cn l lng 35-50 200-290Cn l lng d bay hi 25-40 150-240BOD5 35-50 200-290COD 115-125 680-730Tng nit 6-17 35-100Nit amn 1-3 6-18Tng pht pho 3-5 18-29Pht pht (tnh theo pht pho ) 1-4 6-24Tng coliform 1011-4x1012** 108-1010***Fecal coliform 107-109***

Ghi ch:* Nng tnh khi tiu chun thi nc l 170 l/ngi.ngy** S coli*** S coliform/100 ml

Nc thi bnh vin c thnh phn v tnh cht gn ging nc thi sinh hot th, tuy nhin nng cht bn c thp hn do tiu chun s dng n c ln.Lng cht bn tnh theo n v 1 ging bnh thi vo h thng thot nc trongmt ngy l:

-Cht bn l lng : 130g(Copyright Vietnam Water Forum - www.VinaWater.org)


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-BOD5 : 70g-Nit amn : 16g-Clorua : 18gNng cc cht bn trong nc thi cc bnh vin c th xc nh theo

bng .3.

Bng .3. Cc ch tiu nhim trong nc thi cc bnh vin nc ta / 8 /.

Ch tiu Nng Min Trung bnh Max

PHCht l lng, mg/lBOD5 , mg/lCOD , mg/lTng s coli form, MPN/100ml

6.2100110140106

7.4160150200107

8.1220250300109

Trong nc thi bnh vin cn cha cc cht thi ty ra, d lng dcphm v mt s cht c hi c trng t qu trnh chn on, xt nghim bnhnhn... c trng ca nc thi bnh vin l s xut hin ca cc loi vi khun gybnh nhSomonella, Leptospira,Vibrio Choleral, Mycobacterium Tuberculosis...

.3. Cc phng php x l nc thi .

.3.1. Mc x l nc thiMc x l nc thi c xc nh da trn quy m i tng thot nc

v cc yu cu v sinh ca ngun tip nhn. Nc mt c th tip nhn nc thi

c chia thnh hai loi: ngun n

c mt loi A vi mc ch s dng cho cp n

csinh hot v cng nghip thc phm v ngun nc mt loi B vi vic s dng nccho cc mc ch khc. Nng gii hn cho php ca cc cht nhim trong ccloi ngun nc ny c quy nh theo tiu chun mi trng TCVN 5942-1995 .iu kin cn khi xc nh mc XLNT cn thit l nc thi khi x c tnhn kh nng t lm sch ca ngun khng c lm cho nng cht bn ti imkim tra s dng nc vt nng gii hn cho php. iu kin , khng ch ivi nc thi khi x vo ngun nc mt c quy nh theo tiu chun thit knc th 20TCN 51-84 hoc tiu chun mi trng TCVN 5945-1995, TCVN6772:2000 (ph lc 1).Theo cc quy nh ny, nc thi mt s ch tiu trong sinhhot khi x vo ngun nc phi p ng yu cu nu trong bng .4..

Bng .4. Nng gii hn cho php ca mt s cht nhim trong nc thi sinhhotkhi x vo ngun nc (Theo TCVN6772:2000)

TT Thng s Gi tr gii hnMc I Mc II Mc III Mc IV Mc V

1 pH 5-9 5-9 5-9 5-9 5-92 BOD5, mg/l 30 30 40 50 2003 Cht rn l lng, mg/l 50 50 60 100 100



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4 Cht rn c th lng, mg/l 0,5 0,5 0,5 0,5 KQ5 Tng cht rn ho tan, mg/l 500 500 500 500 KQ6 Sun phua(theo H2S), mg/l 1,0 1,0 3,0 4,0 KQ7 Nitrt (NO3

-), mg/l 30 30 40 50 KQ8 Du m (thc phm), mg/l 20 20 20 20 100

9 Phosphat (PO43-

), mg/l 6 6 10 10 KQ10 Coliform, MPN/100ml 1.000 1.000 5.000 5.000 10.000Ghi ch:KQ- Khng quy nh gi tr;

Cc mc I,II,III,IV v V: theo loi hnh v quy m cng trnh dch v.

Nh vy vic xc nh mc x l nc thi cn thit ca i tng thinc sinh hot quy m nh v va cng phi da trn hai iu kin cn v nutrn. Vic kim sot nhim xc nh mc XLNT cn thit cho khu dn choc th c thc hin theo s nu trn hnh .5.

Nc thi ccx nghip cng nghip

Nc thi khu dn c Kim sot theo20TCN51-84 i tng

s dng nc

Kim sot theo tiu chuncht lng nc s dng

Trm XLNTTrm cp nc

Kim sot theoTCVN6772:2000 hoc TCXD 188:196

im x im ly nc

im kim tra

Kim sot theoTCVN 5942-1995

Hnh . 5. S kim sot nhim nc ( c s xc nh mc XLNT cn thit).

Nc thi sinh hot thng c s l theo 3 bc ( mc ) nu trn hnh .6sau y:

-Bc th nht ( x l bc mt hay x l s b ): Lm trong nc thibng phng php c hc loi cn v cc cht rn ln. y l mc btbuc i vi tt c cc dy chuyn cng ngh XLNT. Hm lng cn l lngtrong nc thi sau khi x l giai on ny phi b hn 150 mg/l nu nc



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thi c x l sinh hc tip tc hoc b hn cc quy nh nu trong bng .6.nu x nc thi trc tip vo ngun nc mt.

Nc thi sinh hot Nc thi bnh vin Nc thi sn

xut

Hnh .6. Cc bc x l nc thi th

Kh trng din vi khungy bnh dch (cc bin

php ho hc hoc vt l)

Tch rc, ct v cnlng trong nc thi

(cc bin phpc hc)

Kh cc cht c hi v mbo iu kin lm vic bnh

thng ca cc cng trnh x lsinhhc nc thi (Cc bin

php c hc, hohchoc ho l)

Tch cc cht hu c trongnc thi (binphp sinh

hc)

Kh cc cht dinh dng (N-P) v kh trngnc thi (Cc bin php sinh hc, ho hc

hoc hocho l)

X nc thi ra ngun v tngcng qu trnh t lm schcangun nc

T lm sch cangun nc

X l trit (X l Bc ba)

X l bc hai

X l s b

(X l bc mt)



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-Bc th hai ( x l bc hai hay x l sinh hc): XLNT bng phng phpsinh hc. Giai on x l ny c xc nh trn c s tnh trng s dng v qutrnh t lm sch ca ngun nc.

-Bc th ba (x l bc ba hay x l trit ): loi b cc hp cht nit vpht pho khi nc thi. Giai on ny rt c ngha i vi cc nc kha hu nhit

i, ni m qu trnh ph dng nh hng su sc n cht lng nc mt.Giai on kh trng sau qu trnh lm sch nc thi l yu cu bt buc ivi mt s loi nc thi hoc mt s dy chuyn cng ngh x l.

Mc x l nc thi ca cc i tng thot nc cng sut nh c thxc nh theo cc nghin cu /7,31/, nu trong bng .5.

Bng .5. Mc XLNT ca cc i tng thot nc cng sut nh

TT i tng thot nc Ngun tip nhnnc thi

Mc XLNTCht l lng,

mg/lBOD5, mg/l Coliform

MPN/100ml

1 Lu vc c lpQ=10005000

m3/ng

Sng h th


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PGS.TS Trn c H

13

Cc trm x l nc tha cng sut nh v va phi m bo mt lot cc yucu nh xy dng n gin, d hp khi cc cng trnh, din tch chim t nh, dqun l v vn hnh v kinh ph u t xy dng khng ln. Yu t hp khi cngtrnh l mt trong nhng yu t c bn khi xy dng cc trm x l cng sut nh vva iu kin nc ta. Cc cng trnh x l nc thi c hp khi s hn ch

c vic gy nhim mi trng khng kh, din tch xy dng nh m bo mquan th Nc thi sinh hot c th x l ti ch trong cc cng trnh lm schs b ( tch du m, tch v x l cn trong nc en), trong cng trnh x lcc b i vi h thng thot nc c lp hoc trong cng trnh x l tp trung titrm x l khu vc. XLNT ti ch s lm gim chi ph u t xy dng cc tuyncng thot nc.

Theo c ch qu trnh lm sch, cc phng php XLNT sinh hot quy mnh v va c phn ra nh sau:

1.XLNT bng phng php c hc trong cc cng trnh v thit b nh songchn rc, b lng ct, b tch du m. y l cc thit b, cng trnh x l s bti ch tch cc cht phn tn th nhm m bo cho h thng thot nc hoc cc

cng trnh x l nc thi pha sau hot ng n nh.2.XLNT bng phng php sinh hc k kh. Qu trnh x l c da trn c

s phn hu cc cht hu c gi li trong cng trnh nh s ln men k kh. i vicc h thng thot nc quy m nh v va ngi ta thng dng cc cng trnh kthp gia vic tch cn lng (lm trong nc ) vi phn hu him kh cc cht hu ctrong pha rn v pha lng. Cc cng trnh c ng dng rng ri l cc loi b thoi, ging thm, b lng hai v (b lng Imhoff), b lng trong kt hp vi ngn lnmen, b lc ngc qua tng cn k kh ( UASB).

3.X l nc thi bng phng php sinh hc hiu kh. Qu trnh x l ncthi c da trn s xy ho cc cht hu c c trong nc thi nh xy t do ho

tan. Nu xy

c cp bng thit b hoc nh cu to cng trnh, th l qu trnhx l sinh hc hiu kh trong iu kin nhn to. Ngc li, nu xy c vnchuyn v ho tan trong nc nh cc yu t t nhin th l qu trnh x l sinhhc hiu kh trong iu kin t nhin. Cc cng trnh x l sinh hc hiu kh trongiu kin nhn to thng c da trn nguyn tc hot ng ca bn hot tnh ( bacroten trn, knh xy ho tun hon.) hoc mng sinh vt (b lc sinh vt, a sinhvt ). X l sinh hc hiu kh trong iu kin t nhin thng c tin hnh trongh ( h sinh vt xy ho, h sinh vt n nh) hoc trong t ngp nc ( cc loi bilc, m ly nhn to).

4.XLNT bng phng php ho hc. l cc qu trnh kh trng nc thibng ho cht (cc cht clo, zn), kh nit pht pho bng cc hp cht ho cht ho

hc hoc keo t tip tc nc thi trc khi s dng li. XLNT bng phng phpho hc thng l khu cui cng trong dy chuyn cng ngh x l trc khi xra ngun yu cu cht lng cao hoc khi cn thit s dng li nc thi.

5.X l bn cn nc thi. Trong nc thi c cc cht khng ho tan nhrc, ct, cn lng...Cc loi ct ( ch yu l thnh phn v c v t trng ln) cphi kh v san nn, rc c nghin nh hoc vn chuyn v bi chn lp rc.Cn lng c gi li trong cc b lng t mt ( thng c gi l cn s cp ) chm lng hu c ln c kt hp vi bn th cp ( ch yu l sinh khi vi sinh vtd ), hnh thnh trong qu trnh x l sinh hc nc thi, x l theo cc bc tch



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14

nc s b, n nh sinh hc trong iu kin ym kh hoc hiu kh v lm kh. Bncn sau x l c th s dng c lm phn bn .

chn c phng php x l sinh hc hp l cn phi bit hm lngcht hu c ( BOD,COD) trong nc thi. Cc phng php ln men k kh thngph hp khi nc thi c hm lng cht hu c cao. i vi nc thi hm lng

cht hu c thp v tn ti ch yu di dng cht keo v ho tan, th x l c chcho chng tip xc vi mng sinh vt l hp l. S chn la cc phng php xl sinh hc nc thi c nu trong bng .6.

Bng .6. Phm vi ng dng cc phng php x l sinh hc nc thi.

Hm lng BOD canc thi

Cht hu c khngho tan

Cht hu c dngkeo

Cht hu c hotan ho tan

Cao(BOD5>500 mg/l) X l sinh hc k kh

Trung bnh(BOD5=300-500 mg/l) X l sinh hc bng bn hot tnh

Thp(BOD5< 300 mg/l) X l sinh hc bng bn hot tnh

X l sinh hc bng mng sinh vt

Cc nguyn t dinh dng nh N,P c trong nc thi cng c th x l bngphng php sinh hc. Cc mui nitrat, nitrit to thnh trong qu trnh phn hy hiu

kh s

c kh trong iu kin thiu kh (anoxic) trn c s cc phn ng phnnitrat. Trn c s nghin cu s hnh thnh h thng thot nc quy m nh nh vva, c im cc ngun nc thi th v iu kin t nhin kinh t x hi nc tac th thit lp s t chc XLNT cho cc khu dn c, th trn th x, cc cngtrnh cng cng v dch v ( hnh .7 ).

Theo s hnh .7, nc thi cc i tng thot nc u phi x l quagiai on tch cc cht rn ln nh rc, ct, cn lng. Cc loi cn lng c x lch yu bng cch ln men k kh. Cc giai on x l tip theo khng bt buc,c thit lp trn c s cng sut, thnh phn tnh cht nc thi, yu cu mc x l v ngun tip nhn.



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PGS.TS Trn c H

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Nc thi ngi nh hoc khudn cc lp Q


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PGS.TS Trn c H

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.4.Mt s cng trnh c trng x l nc thi quy m nh.

.4.1.B t hoi .B t hoil cng trnh x l nc thi bc mt ( x l s b ) ng thi thc

hin hai chc nng: lng nc thi v ln men cn lng. S cu to b t hoi nu

trn hnh .8 . B t hoi c dng hnh ch nht hoc hnh trn trn mt bng, xydng bng gch, b tng ct thp, hoc ch to bng vt liu Composite. B cchia thnh 2 hoc 3 ngn. Do phn ln cn lng tp trung trong ngn th nht nndung tch ngn ny chim 50 n 75% dung tch ton b. Cc ngn th hai hoc thba ca b c dung tch bng 25% n 35% dung tch ton b. B thng su 1,5 n3,0m, chiu su lp nc trong b t hoi khng b hn 0,75m v khng ln hn1,8m, chiu rng ca b ti thiu l 0,9m v chiu di ti thiu l 1,5m. Th tch bt hoi khng nh hn 2,8m3 trong th tch phn lng khng nh hn 2,0m3. Cuto mt s loi b t hoi hai ngn hoc ba ngn c nu trn cc hnh .8.

Hnh .8.S cu to b t hoia.B t hoi hai ngn; b.B t hoi ba ngn

Cc ngn b t hoi c chia lm hai phn : phn lng nc thi (pha trn )v phn ln men cn lng ( pha di ). Nc thi vo vi thi gian lu li trong b t1 n 3 ngy. Do vn tc trong b b nn phn ln cn l lng c lng li. Hiuqu lng cn trong b t hoi t 40 n 60% ph thuc vo nhit v ch qunl, vn hnh b. Qua thi gian 3 n 6 thng, cn lng len men ym kh. Qu trnhln men ch yu din ra trong giai on u l ln men axit . Cc cht kh to nntrong qu trnh phn gii (CH4,CO2,H2S...) ni ln ko theo cc ht cn khc c thlm cho nc thi nhim bn li v to nn mt lp vng ni trn mt nc. Chiudy lp vng ny c th t 0,3 n 0,5m.



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dn nc thi vo v ra khi b ngi ta thng dng cc ph kin t (T)vi ng knh ti thiu l 100 mm vi mt u ng t di lp mng ni, u khcc nh ln pha trn tin kim tra v ty ra. Cn trong b t hoi c ly ratheo nh k. Mi ln ly phi li khong 20% lng cn ln men li trong b lm ging men cho bn cn ti mi lng, to iu kin thun li cho qu trnh

phn hy cn.Do b t hoi c hai phn: phn lng v phn cha cn nn kch thc b ctnh nh sau.

a. Th tch phn lng ca b t hoi ( W1, m3).

1000

.. 11

TNaW = , m

3 (.3).

b. Th tch phn cha v ln men cn (W2, m3)

1000

.. 22

TNbW = , m3 (.4).

c. Tng th tch ca b t hoi ( W, m3 )

W=W1+W2 (.5).Trong : a- tiu chun thi nc ca mt ngi trong mt ngy, l/ng.ngy; b- tiuchun cn lng li trong b t hoi ca mt ngi trong mt ngy; gi tr ca b phthuc vo chu k ht cn khi b; nu thi gian gia hai ln ht cn di 1 nm th bly bng 0,1 l/ng.ngy, nu trn 1 nm th b ly bng 0,08 l/ng.ngy; T1- thi giannc lu li trong b t hoi; T2- thi gian gia hai ln ht bn cn ln men thngly t 1 n 3 ngy; N - s ngi b t hoi phc v.

Th tch ca b t hoi cng c th c chn theo quy nh ca Quy chuncp thot nc cho nh v cng trnh / 4 / nh sau ( Bng .7).

Bng .7. Th tch b t hoi ca nh

Ngi nh gia nh c lp Ngi nh c nhiu gia nhv cn h

Th tch ti thiu ca b thoi , m3

1 hoc 2 phng ng3 hoc 2 phng ng4 hoc 2 phng ng5 hoc 6 phng ng

2 cn h3 cn h4 cn h5 cn h6 cn h7 cn h8 cn h9 cn h10 cn h

2,83,84,55,77,68,59,510,511,412,313,3

. Kch thc ca mt s loi b t hoi BTCT thng c ng dng Vitnam c nu trong bng .8.



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PGS.TS Trn c H

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Bng .8. Kch thc c bn ca b t hoi b tng ct thp.

Dung tch cng Kch thc b ,mtc ca b W,

m3Chiu di ngn

th nhtChiu di

ngn th haiChiu rng Chiu su cng

tc

234510

2,42,62,22,43,0

-1,01,11,21,5

0,91,01,11,21,5

1,01,01,11,21,5

B t hoi c th a vo s dng ngay sau khi xy dng. N khng cn mtyu cu c bit no trc khi a vo vn hnh. Tuy nhin s ln men bn cn phibt u sau vi ngy. Bn cn ln men phi c ht sau 1 n 3 nm b hot ng.Ti thi im ht, phn bn cn cha ln men nm pha trn v th ng ht ca mybm phi t su xung y b. Thng thng ngi ta gi li khong 20% lng

bn cn ''

gy men''

cho bn cn ti t sau. Khi ht bn cn ra khi b, hn hpbn cn nc thng c BOD5 khong 6.000mg/l, tng cc cht rn (TSS) khong15.000 mg/l, tng nit khong 700 mg/l ( trong N-NH3 l 400 mg/l), tng phtpho khong 250 mg/l v tng du m khong 8.000 mg/l. Bn cn ln men clm kh trn sn phi bn, trong hm lm phn compot hoc x l tip tc trongcc bi lc ngp nc trng cy pha trn.

Khi ra khi b COD ca nc thi gim t 25% n 50%. Nng cc chtbn trong dng nc thi ra khi b t hoi nm trong gii hn sau y :

-BOD5 : 120-140 mg/l-Tng cc cht rn: 50-100 mg/l-Nit amn (N-NH3 ):20-50 mg/l

-Nit nitrat ( N-NO3) :


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PGS.TS Trn c H

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Cng trnh XLNT H thng thot nc XLNT tip tc hoctip nhn nc thi

V tr xydng cng

trnh v iu

kin t aithun li

B t hoiNc thi t chy,

gin onGing, ho, b

hoc bi thm hot

ng gin ontheo chu k

V tr xydng v iukin t aikh khn

B t hoi tiptheo l h thng

x l sinh hc hiukh hoc b lc ct

hot ng ginon

Nc thi cbm v phn phi,

nh lng theochu k

Ho hp ph, hohoc bi bay hi

nc, bi lc ngpnc, kh trng v

x nc thi rangun nc mt

Hnh .9. S ng dng b t hoi XLNT ti ch.

Thnh phn t, h s thm v vn tc thm cc loi t, mc nc ngm, dc a hnh, din tch t s dng XLNT... l nhng yu t cn phi tnh n khila chn cc cng trnh XLNT tip sau b t hoi. S hot ng ca b t hoikt hp vi mt s cng trnh XLNT khc trong iu kin t ai thun li v t aikh khn c nu trn cc hnh .10a v .10b.

a.

b.Hnh .10. S kt hp hot ng gia b t hoi vi cc cng trnh XLNT khc.

a.Trong iu kin t ai thun li; b.Trong iu kin t ai kh khn.(Copyright Vietnam Water Forum - www.VinaWater.org)


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PGS.TS Trn c H

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Hin nay ngi ta thng xy dng b t hoi kt hp vi cc ngn lc k

kh.Ngn lc k kh ca b t hoi hot ng theo nguyn l lc ngc t di lnvi chiu dy lp vt liu 0,5m n 0,6m phn b t trn xung di nh sau:

-Lp si hoc dm ng knh 36mm dy 0,10,2m

-Lp cui , si hoc ng knh trung bnh 1218mm dy 0,4m.S ngn lc k kh c th mt hoc nhiu ngn. S cu to b t hoi c cc

ngn lc k kh c nu trn hnh .11.

Hnh .11..S cu to b t hoi vi cc ngn lc k kh.

.4..2. Ging thm v bi lc ngm.a.Ging thm. Ging thm l cng trnh trong nc thi c x l bng

phng php lc qua lp c t , si v xy ho k kh cc cht hu c c hp phtrn lp ct si . Nc thi sau khi x l c thm vo t . Do thi gian nclu li trong t lu , cc loi vi khun gy bnh b tiu dit hu ht .

m bo cho ging hot ng bnh thng , nc thi phi c x lbng phng php lng trong b t hoi hoc b lng hai v . Ging thm cng chc s dng khi mc nc ngm trong t su hn 1,5 m m bo c hiuqu thm lc cng nh khng gy nhim nc di t . Cc loi t phi d thmnc , t 34 l/m2.ngy n 208 l/m2.ngy .

Ging thm, s cu to nu trn hnh .11 c hnh trn trn mt bng ,ng knh ti thiu 1,2 m , c xy dng bng gch hoc b tng ct thp . Gingthm cng c th c lp t bng cc ng ging . Thnh ging b tng b dy tithiu 100 mm, c b tng mng vng chc .



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PGS.TS Trn c H

21

d

lp nc

>=300

200

six

dm

A AA-A

0 = 150

Hnh .11. S cu to ging thm.

Din tch ging thm c xc nh gia vo loi t v loi i tng thotnc . Din tch thm cn thit tnh cho mt ngi c nu trong bng .9.

Bng .9. Din tch thm lc cn thit tnh cho mt ngi m h thng thot ncphc v, m2/ngi .

Loi tLng nc hp

th ln nhttrong 24h, l/m2

Nh ,q=200

l/ng.ngy

H gia nhq=100

l/ng.ngy

Trng hcq=65

l/ng.ngyCt th hoc si 205 0,93 0,23 0,14

Ct mn 163 1,4 0,37 0,23Ct pha st 102 2,3 0,6 0,37St ln nhiu cthoc si

45 3,7 0,93 0,6

St ln t ct hocsi

33 7,1 1,85 1,25

St nng , t cng hoc cc loit khng thmnc khc

Khng s dng .

Ging thm c lt si , dm .. c nh dn t di ln . Lp trn cngc bng c t mn v c chng xi nc bng tm chn . tng kh nngthm nc ca ging, bn ngoi ging thm si.Vic thng thong c thc hinqua ng thot nc hoc dng ng thng hi ring .

b.Bi lc ngm. Nu nc ngm gn mt t v khng th xy dng gingthm th c th xy dng h thng bi lc ngm . Nc thi trc khi qua bi lcngm phi c lng s b trong cc cng trnh x l c hc . Khi i qua lp t bilc ngm , cc cht bn trong nc thi s c hp ph theo con ng thm lc ,



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PGS.TS Trn c H

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sau c xy ho sinh ho. Thng thng trong lp t pha trn din ra qutrnh xy ho hiu kh v trong lp t pha di din ra qu trnh h hp k kh cccht hu c . Do lp t khng ln ( t 0,6 n 0,9 m ) nn vo thi k pht trinca cy trng , mt khi lng ln nc thi c r cy hp th v ch mt phnnc chy vo ngun . S hot ng ca cy trng cng gp phn cung cp xy cho

t . Cu to bi lc ngm bao gm phn : ngn phn phi nc thi , h thngphn phi bi lc v h thng thu nc. Trn bi lc ngm c b tr ng thng hi .S cu to ca bi lc ngm c nu trn hnh .12. Trong bi lc ngm, hthng phn phi t cch mc nc ngm khng nh hn 1 m v thng b tr trongho. Cc thng s cu to ca bi lc ngm c nu trong bng .10.

0.20~0.25%

A

A

600-900

500

>=50

0 100

A-A

Hnh .12. S cu to bi lc ngm .

Bng .10. Cc thng s cu to ca bi lc ngm

Thng s cu to Gi trTi thiu Ti a

S ng ng phn phi nc 1Chiu di mi ng ng , m - 30Chiu rng y ho , m 0,46 0,9Khong cch gia cc tuyn ng , m 1,8 - dy lp t lp trn ng , mm 300 -

dc cc tuyn ho ,mm/m Ngang bng 25 dy lp vt liu lc di ng phn phi nc,mm

300 -

dy lp vt liu lc trn ng phn phi nc,mm

50 -

Qu trnh XLNT trong bi lc ngm ph thuc vo mt lot yu t nh ti

trng thu lc h thng phn phi , nhit nc thi, chiu dy v loi t lc,



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PGS.TS Trn c H

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chiu dy lp t ph, m ca t ... Theo cc nghin cu ca Vin nghin cua cht thu vn v cp thot nc Lin x / 16 /, hiu qu x l nc thi c thxc nh theo biu thc thc nghim sau y :

( .6)Trong : La v Lt l BOD ca nc thi trc v sau khi x l trong bi lc ngm,mg/l; T-nhit ca nc thi,0C; q-ti trng thu lc ca h thng phn phi (ti)nc thi, l/m.ngy; H- chiu dy lp vt liu lc ngm tnh t mp mng ti nmp mng thu nc hoc n mc nc ngm, m; h-chiu dy lp t ph pha trnvt liu lc, m; a-khong cch gia cc ng ti,m; a-ng knh trung bnh ca htvt liu lc,mm; W- m ca vt liu lc,%.

Din tch hu ch ca bi lc ngm ph thuc vo loi t v c xc nh

theo cng thc ( .6) hoc theo bng .9 ging nh

i vi ging thm ..4.3. a lc sinh hca lc sinh hc c dng x l nc thi bng phng php sinh hc

theo nguyn l dnh bm. a lc l cc tm nha, g... hnh trn ng knh 2- 4 m,dy di 10mm ghp vi nhau thnh khi cch nhau 30-40mm. a lc c b trthnh dy ni tip quay u trong b cha nc thi. S b tr h thng a lcc nu trn hnh .13.

t mtB lng

N

c thi vo

H thng a lc sinh hc

t haiB lng

Nc thi saukhi x l

Hnh 5.11. S h thng a lc sinh hc

Hnh .13. S hot ng ca h thng a lc sinh hc.

Tc quay ca a t 1 n 2 vng/pht v m bo dng chy ri, khng cho bncn lng li trong b nc thi. Trong qu trnh quay, phn di ca a ngp trong

2,05,0825,0

62,07,0

t

1,1a )

hWad(

qHT450

LL =



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PGS.TS Trn c H

24

nc thi. Qu trnh hp ph v dnh bm cc cht hu c dng ho tan, keo v vybn ln mng sinh vt hnh thnh trc , c din ra. Khi quay ln pha trn, vikhun s ly xy xy ho cht hu c v gii phng CO2. Mng sinh vt dy 2-4mm, ph thuc vn tc quay ca a. Do sinh khi tng, mng sinh vt bm trnmt a dy ln dn sau t tch ra khi a. Bn cn mng sinh vt c lng li

trong b lng t hai.a lc sinh hc c s dng rng ri x l nc thi sinh hot vi cngsut khng hn ch. Tuy nhin ngi ta thng s dng h thng a lc sinh hc cho cc trm XLNT cng sut di 5.000 m3/ngy. a lc sinh hc c tnh tonda vo ti trng thy lc q, m3/m2 b mt a. ngy v c xc nh theo biu nu trong hnh . 14 theo nghin cu ca Mc.Neil, 1978/ 33 /. Gi tr q thay i,ph thuc vo BOD ca nc thi trc v sau khi x l. c tnh k thut ca alc sinh hc c nu trong bng .11.

Hnh .14. Biu xc nh ti trng thy lc q ca a lc sinh hc dng XLNTsinh hot.

Tng din tch b mt a lc A c xc nh theo biu thc sau:

q

QA = , m

2 (.7)

Trong : Q- lu lng nc thi, m3/ngy.



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PGS.TS Trn c H

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Bng .11.c tnh k thut ca a lc sinh hc

c tnh Gi trTi trng thy lc q, m3/m2 b mt a.ngy 0,03-0,16Vn tc quay ca a, m/s 0,3

T l th tch b cha/din tch b mt a, m3

/m2

0,005Phn din tch a ngp nc, % 40S dy a 4Khe h gia cc a, cm 2-3ng knh a, m 1-4

.4.4.Aeroten hot ng gin on theo m (h SBR).Aeroten hot ng gin on theo m ( Sequencing Batch Reactor - SBR) l

mt dng cng trnh x l sinh hc nc thi bng bn hot tnh, trong tun tdin ra cc qu trnh thi kh, lng bn v gn nc thi. Do hot ng gin onnn s ngn ca b ti thiu l 2. S hot ng ca h thng b nu trn hnh .15.

B chn rc

Song chn rc

Nc thi

B SBR2B SBR1

Kh trng

X nc thi ra sng, h

X bn hot tnh d

t mt

B lng

Hnh .15. S hot ng ca h thng aeroten hot ng gin on SBR.

Cc giai on hot ng din ra trong mt ngn b (hnh .16) bao gm: lmy nc thi, thi kh, lng tnh, x nc thi v x bn d.

Trong bc mt, khi cho nc thi vo b, nc thi c trn vi bn hottnh lu li t chu k trc. Sau y hn hp nc thi v bn c sc kh bchai vi thi gian thi kh ng nh thi gian yu cu. Qu trnh din ra gn vi iukin trn hon ton v cc cht hu c c xy ho trong giai on ny. Bc thba l qu trnh lng bn trong iu kin tnh. Sau nc trong nm pha trn lp



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PGS.TS Trn c H

26

bn c x ra khi b. Bc cui cng l x lng bn d c hnh thnh trongqu trnh thi kh ra khi ngn b, cc ngn b khc hot ng lch pha m bocho vic cung cp nc thi ln trm x l nc thi lin tc.

Nc thi vo

Lm y nc thi1

2 Thi kh

Lng3

5 X bn d

X nc thi4

Hnh .16. Cc giai on ca b aeroten hot ng gin on.

Cng trnh hot ng gin on, c chu k. Cc qu trnh trn nc thi vibn, lng bn cn ... din ra gn ging iu kin l tng nn hiu qu x l ncthi cao. BOD ca nc thi sau x l thng thp hn 20 mg/l, hm lng cn llng t 3 n 25 mg/l v N-NH3 khong t 0,3 n 12 mg/l. B aeroten hot nggin on theo m lm vic khng cn b lng t hai. Trong nhiu trng hp,ngi ta cng b qua b iu ho v b lng t mt.

H thng aeroten hot ng gin on SBR c th kh c nit v pht pho

sinh ho do c th iu chnh c cc qu trnh hiu kh, thiu kh v k kh trongb bng vic thay i ch cung cp xy. Cc ngn b c sc kh bng my nnkh, my sc kh dng Jet hoc thit b khuy trn c hc. Chu k hot ng cangn b c iu khin bng rle thi gian. Trong ngn b c th b tr h thngvt vng, thit b o mc bn, ...

B aeroten hot ng gin on c thit k theo cc ch tiu sau y(bng.12 )



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PGS.TS Trn c H

27

Bng .12. Cc ch tiu thit k h aeroten hot ng gin on (SBR)

Ch tiu thit k Gi trTng th tch 0,2-2,0 ln lu lng trung bnh 1 ngyS b 2

Chiu su cng tc 3-6 mT l lng cht bn huc/lng bn

0,04-0,2 kg BOD/kg bn.ngy

Thi gian 1 chu k 4-12 gic im cp kh Cp kh cho bc lm y v khuy trn bn vi

nc thiLng xy Cp cho qu trnh xy ho cht hu c v

nitrat ho nhi vi cc aeroten truyn thng

B aeroten h SBR c u im l cu to n gin, hiu qu x l cao, khc cc cht dinh dng nit, d vn hnh. S dao ng lu lng nc thi t nhhng n hiu qu x l. Nhc im chnh ca b l cng sut x l nc thinh. b hot ng c hiu qu ngi vn hnh phi c trnh v theo dithng xuyn cc bc x l nc thi.

.5.S dng nc thi v bn cn trong nc thi.

.5.1.Cc h thng thot nc kt hp ti s dng nc thi v bn cntrong nc thi.

Nc thi sinh hot cha lng ln cc cht hu c v cc cht dinh dngcn thit cho cy trng, vt nui ... Thnh phn chnh ca nc thi sinh hot cnu trong bng .13 sau y.

Bng .13.Thnh phn chnh ca nc thi sinh hot v nguyn tc x l, s dng li.

Thnh phn Ti lng, Trong , %kg/ngi.n

mNc xm Nc tiu Nc phn

Nit 4-5 3 87 10Pht pho 0,75 10 50 40Kali 1,8 34 54 12

COD 30 41 12 47Nguyn tcx l v tis dng

X l sau ti sdng hoc x vongun nc

X l v lmphn bn trctip cho cy

X l, snxut kh sinhhc v cungcp chtdinh dngb sung chot



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PGS.TS Trn c H

28

T l cc nguyn t dinh dng trong nc thi sinh hot c nu trong bng1.18. Trong nc thi t l N:P:K l 5:1:2, trong lc tron phn chung l 2:1:2,4 .

Bng .14. T l nguyn t dinh dng trong nc thi sinh hot v trong phn bn.

Dng phn bn Hm lng , g/l hoc g/kg.N P2O5 K2O CaO Nc thi khi tiu chun

thot nc l 150l/ng.ngy

Phn chung0,087

5

0,014

2,5

0,030

6,3

0,12

-

Trong nc thi th, hm lng tng nit thng thng t 20 n trn 100mg/l , ph thuc vo tiu chun dng nc , loi nc thi , c im cng trnhcng cng ...Nit ban u ch yu tn ti di dng nit hu c, nit amn v nit

nitrat. T l hm l

ng cc dng nit ny quyt nh th t

u tin x l n

c thitrong t.Hm lng pht pho tng s trong nc thi sinh hot v nc thi th

cng dao ng ln, t 5 n 50 mg/l. Trong qu trnh x l s b nc thi v vnchuyn nc thi vo t , pht pho hu c s b chuyn ho sinh hc thnh phtpht. Trong mi trng t kim tnh , pht pht s kt hp vi in canxi to thnhcanxi pht pht . V ngc li, trong mi trng axit, pht pht s tc dng vi xit st hoc xit nhm to thnh cc hp phn khng ho tan.

Phn ln nit v hu ht kali tn ti trng thi ho tan v cy trng d hpth. Pht pho thng b lng ng trong bn cn.

Nh vy, nc thi sinh hot cha hm lng ln Nit, Pht pho, Kali l

nhng cht cn thit cho cy trng. V vy xu th s dng nc thi ti cy vbn cn ca n lm phn bn ngy cng tng. Hin nay, ngi ta thng c ccquan im phn chia h thng thot nc phn tn quy m nh v va ra cc loi :h thng thot nc khng ti s dng nc thi , ti s dng mt phn nc thi vti s hon ton nc thi. H thng thot nc phn tn c ti s dng nc thi(Decentralised Sanitation and Reuse - DESAR) c nu trn hnh .17.

Nc thi sau khi lng s b c th s dng ti cho cy trng. Cng tiph thuc vo c im t, cy trng v nng cc cht trong nc thi v daong t 0,1 n 0,2 m/nm (1000m3/ha n 20000m3/nm ). Phng php ti lti ngp hoc ti phun khi dng nc thI ti sn lng cy trng s tngthm 20% n 30%.

Qu trnh x l nc thi sinh hot s to nn lng ln bn cn ( bng khong1% th tch nc thi x l ). Gi tr phn bn ca tng loi bn cn nc thi cnu trong bng .15 v hm lng cc nguyn t vi lng c nu trong bng . 16.



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PGS.TS Trn c H

29

S dng nc ma

ti ch

Nc cp Khu dn c Nc thi sau x l

Cng trnh XLNT ti ch Cc cht dinh dng

Trng cy ti ch S dng li nc thi ti ch

Thm canh nng nghip

Hnh .17. S h thng thot nc phn tn c ti s dng nc thi.

Bng .15. Thnh phn cc cht dinh dng trong cc loi bn cn nc thi,% trng lng kh

Nguyn t dinhdng

Cn ti Bn cn lnmen

Bn hottnh

Phnchung

NiPht phoKali

1,6-4,00,6-5,20,2-0,6

1,7-6,00,9-6,60,2-0,5

2,4-6,52,3-8,00,3-0,4

2,0-2,61,6-1,31,8-1,9

Bn cn , nc thi cha phn ln cc cht hu c, Nit v pht pho. Hmlng kali tng i thp nn ngi ta thng b sung thm kali trn cngbn cn lm phn bn. Ngoi ra hm lng CaO trong bn cn cao nn nthch hp trong vic ci to t chua phn.

Trong nc thi v bn cn ca n c cha cc loi vi khun gy bnh, trnggiun sn . Nc thi sinh hot l mi trng tn ti ca cc loi vi sinh vt trong c vi khun gy bnh. c tnh c khong 7.000 vi khun Salmoella, 6.000-7.000 vikhun Shigella v 1.000 vi khun Vibrio cholera trong 1 lt nc thi. Cc loi vikhun Shigella v Vibrio cholera nhanh chng b tiu dit trong mi trng ncthi nhng vi khun Salmoella c kh nng tn ti lu di trong t. Cc loi virutcng xut hin nhiu trong nc thi. Ngoi ra trong nc thi sinh hot cn cnhiu cc loi trng giun sn nhAncylostoma, Ascaris,Trichuris v Taenia... v



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PGS.TS Trn c H

30

thng gy ra cc hu qu nghim trng khi s dng trc tip nc thi ti rau,nui c ...Trong 1 gam bn cn cha t 5 n 67 trng giun sn . Trng giun sn cth tn ti trong t n 1,5 nm. V vy nn hn ch ti nc thi trong ma thuhoch. i vi cc loi rau n sng th khng c ti nc thi.

Vi mt mc no , nc thi th c th lm tng hm lng kim loi

nng trong t khi dng n ti cy.. Hm lng kim loi nng trong nc thicc th trn v th c sn xut cng nghip ln hn trong phn b t 5 n 15 ln.Hm lng Cd, Zn, Cu, Pb. trong t ti nc thi th thng cao hn trongcc mu i chng ti nc sng h t 3 n 20 ln .

Bng .16. Hm lng kim loi nng trong cc loi phn bn

Nguyn t Bn cn nc thi Phn m Phn chungAs, mg/kgCd, mg/kgCu, mg/kg

Hg, mg/kgPb,mg/kgZn, mg/kg

2-262-150050-3300

0,1-5550-3000700-49000

2,2-1200,05-8,5


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PGS.TS Trn c H

31

.5.2. S dng nc thi nui trng thy sn v nui c.Nc thi sinh hot cha nhiu cht hu c v nguyn t dinh dng, l mi

trng cho to v cc loi sinh vt khc pht trin. Theo chu trnh dinh dng trongvc nc, n l ngun thc n cho c v cc loi thy sn khc.

To v cc thc vt nc pht trin trong cc h sinh vt n nh hoc cc ao

h tip nhn nc thi khng nhng cung cp xy cho cc loi vi khun xy hotip tc cc cht hu c m cn tng hp nn prtin trong sinh khi. Trong h, tov vi khun quan h vi nhau qua chu trnh O2 v CO2. Theo O.N.Rixuna / 18 /,trong h sinh vt khi xy ho khong 180 n 280 mg/l cht hu c ho tan, vikhun tiu th 289347 mg/l cht hu c ho tan v gii phng 313473 mg/l CO2.Trong lc to s tiu th 360558 mg/l CO2, gii phng 322496 mg/l O2 v tonn sinh khi l 200310 mg/l sinh khi giu protein. Khong 50% tng protin sinhkhi ca cc ao h c ngun gc t to. To s dng nng lng t nh sng mttri, CO2 v cc nguyn t khong khc nh N,P,K tng hp sinh khi. Snlng nui cy to cao hn sn lng trng hoa mu khc rt nhiu ( Bng .17). Cc

loi to lc n bo nh

Cholorella, Scenedesmus hoc to lam a bo nh

Spirulina. giu protein ,m, cc bon, hydrat v vitamin cng cc cht hot tnhsinh hc khc ang c nui trng rng ri trong nc thi sinh hot Nht Bn ,cc nc Trung SNG, o.

Bng .17. Sn lng protein ca cc loi hoa mu khc nhau

Loi hoa mu Sn lng protin,kg/ha.nm

u tng 650Ng 270

La m 150La 55To ( trong h sinh vt) 82.000

To c nui trong cc b ngoi tri ng knh n 20m su t 1,0m n

5,0m. B nui to c khuy trn thng xuyn v cung cp thm CO2. Vi trnggy bnh trong nc thi c nui trng to c th b dit n 99,9%. Dch to cthu hi bng cc phng php c hc lm dc phm, lm thc n cho gia schoc bm vo cc ao h nui c.

S lm sch nc thi kt hp vi nui cy, thu hi to ca trm x l

nc thi quy m va v lm sch nc thi kt hp vi nui to, nui c, ti vn(H sinh thi VAC) c nu trong cc hnh .18 v .19.i vi trm x l nc thi quy m va, b nui to phi c cp thm CO2

ly t ngun t nhin liu v kh sinh hc ca h thng ni hi cp nhit (hnh .19).Vic nui trng to y mang tnh cht cng nghip v sinh khi cu n mang tnhsn phm cao .



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PGS.TS Trn c H

32

nh sng

Nc thi

Sinh hot

Bn hot tnh CO2tun hon

Bn cn

CH4 nhinCO2 liu

Bn cn ln men s Nng lngdng bn rung

Hnh .18. S h thng x l nc thi kt hp vi nui to.

i vi tng ngi nh hoccm ngi nh, ao nui to l mt trong cc nt cah sinh thi vn-ao-chung (VAC). To khng cn thu hi m c s dng trctip lm thc n cho cc ng vt nguyn sinh, c vt . Phn ln cc loi vi khungy bnh, cc cht hu c c trong nc thi sinh hot c lm sch nn ncthi c th s dng t rau hoc ra chung tri.

S dng nc thi nui c mang li hiu qu kinh t cao, tuy nhin lng xy, ngun thc n d thu nhn v hp th l cc yu t cn thit c pht trin .V vy, c thng c nui giai on cui ca h thng h sinh vt. Cc loi cc sn lng cao thng c nui trong mi trng nc thi l c trm, m, rphi Sn lng c nui cc vng nc thi nc ta cng nh mt s nc khcnhn , Thi Lan, Philipin/ 23 / dao ng t 1,0 n 3 tn/ha.nm. S hthng h sinh vt x l nc thi kt hp nui c nu trong hnh .19.

Yu cu c bn i vi vic nui c bng nc thi l m bo ch xy .

C chp pht trin trong ngun nc c hm lng xy ho tan ln hn 4 mg/l; cnc hi i hi lng oxy trn 6 mg/l. Tuy nhin hm lng xy ho tan ph thucvo ti lng BOD trong h. Trong iu kin nhit i ti lng ny khng ln hn1gBOD/m2.ngy. Gi tr pH ca nc thi nui c nm tong khong t 7 n 8.Thng thng ao h nui c c thu gian lu nc thy lc t 3 n 10 ngy v su t 0,5m n 0,8m. Vi vic nui c trong bc cui cng ca h thng h sinh vtba bc nguy c nhim vi khun gy bnh trong c gim hn Theo Marais, 1974 /23/ , s lng fecal coliform c th gim xung di 1000 coli/100ml trong h sinhvt bc ba p ng yu cu cho php vi ngun nc nui c theo quy nh ca t

B lngt 1

BAroten

B lngt 2

H nuito Tch

to

Nc nuic hoc

ti rung

B ln menk kh

Bchakh

X l kh thi

Phtin

Lmkh

Trittrng

Snphm

to



33/46


34/46

PGS.TS Trn c H

34

kim tra xong mi c dn nc thi vo cng trnh. Khng nn x kit nc khicng trnh m nn li mt t nc sch ri dn nc thi vo

Ty theo c ch v quy m cng trnh x l nc thi m quy nh thi giana cng trnh vo hot ng, thi gian khi ng... Cng vic ny cn cc chuyngia c kinh nghim theo di v tin hnh hiu chnh. Thi gian khi ng mt s

loi cng trnh x l nc thi c th tham kho theo bng .18.

Bng .18. Thi gian a cc cng trnh x l nc thi vo hot ng

Tn cng trnh Thi gian khi ng Yu cu qun l vn hnh trong thigian khi ng

B t hoi Lng cn: Sau 1 3 ngyLn men cn lng: Sau 3thng

a lng cn ln men bngkhong 15 20% dung tch phncha cn gy men

B lng hai v Lng cn: Sau 3 5 ngyLn men cn lng: Sau 3thng

a lng cn ln men bngkhong 15 20% dung tch phncha cn gy men

B lc k kh T 2 3 thng Lu lng nc thi cp cho b trongthi gian khi ng tng dn t 25%n 100% lu lng thit k

B lc sinh hc T 2 3 thng cho n khixut hin nitrat trong ncthi sau x l

Tng dn lu lng nc thi t 10n 25% lu lng thit k. Thigian 1 chu k ti t 5 n 6 pht

B Aeroten T 1 n 2 thng cho n khich s bn o trong bnhImhoff l 200 300 ml/l

(nu c bn hot tnh t nikhc a v th thi gian nygim xung cn t 2 tunn 1 thng)

Cho bn hot tnh ly t ni khc sc kh vi khong 30% lu lngnc thi trong thi gian u. Sau

tng dn cng sut cp nc thi chon khi ch s bn l 200 300 ml/l

H sinh hc T 2 n 3 thng sau khihnh thnh h sinh vt trongh

Giai on u c th bm nc sngvo y h, sau x nc thi dndn vo h

Bi lc ngp nc T 2 n 3 thng sau khi cypht trin pha trn b mt

Trong thi gian

a cng trnh vo hot ng, cn tin hnh nghin cu, phntch nc thi xc nh c l cng trnh c m bo lm sch theo yu cuhay khng. Cc s liu thu nhn c trong giai on ny c b sung vo quytrnh vn hnh cng trnh XLNT. Nc thi a v cng trnh trong giai on ny clu lng v nng thp hn gi tr thit k .

Hiu qu v thi gian ca giai on khi ng ch yu ph thuc vo trnh chuyn mn v thc trch nhim ca cng nhn vn hnh. Cng nhn trc tipqun l cng trnh XLNT phi nm c cc qu trnh c bn din ra cng trnh



35/46

PGS.TS Trn c H

35

..iu kin qun l vn hnh cc cng trnh XLNT rt nghim ngt v vy i hingi cng nhn phi c tinh thn trch nhim i vi cng vic ca mnh.

.6.2. Nguyn tc qun l vn hnh mt s cng trnh x l nc thiCc cng trnh x l nc thi c vn hnh theo tiu chun Vit Nam

TCVN 5576-91 H thng cp thot nc- Quy phm qun l k thut / 3 / v Quy

chun H thng cp thot nc trong nh v cng trnh / 4 /. Nguyn tc vn hnhcc cng trnh phi ph hp vi cc qu trnh XLNT din ra trong . Yu cu vtrnh vn hnh cc cng trnh XLNT ph thuc vo loi cng trnh XLNT ti chhay l XLNT tp trung.

a. Qun l vn hnh cc cng trnh XLNT ti ch. Cc cng trnh XLNT tich nh b t hoi, ging thm, bi lc ngm, b thu du m... c xy dng trongkhun vin cc ngi nh, cc cng trnh dch v cng cng. Cc cng trnh XLNTloi ny pi c qun l, vn hnh theo mt s yu cu c bn sau y.Bn cn trong b t hoi phi c thng xuyn ly ra khi b t hoi vi chu k t6 thng n 1 nm. Khi ly bn phi li khong 20% bn ln men lm micho qu trnh phn hu chu k sau. Khi ht bn, u ng ht my bm phi choxung tn y b. Vng cn trong b phi c ph v vt thng xuyn chngtc ng dn nc thi. Trn np b t hoi khng c trng cy hoc xy dng cccng trnh khc. Nu mi kh chu do qu trnh ln men axit trong b bc ln thphi cho thm vi cng nc thi chy vo b trong mt vi ngy.Nc thi trc khi x vo ging thm phi c tch rc, c t v cn. Ging thmc bo dng chu o bng cch m np ra theo di thng xuyn. Nu kh nngthm b hn ch th phi xc lp ct pha trn ra sch. Khi thm nc khng mbo c na th phi o ging mi v tr khc.

Du, m v cc loi cht ni khc phi c vt thng xuyn ra khi b thudu m. Sau mi ln ng b 4 gi, cn ra b bng nc sch. Lng nc ra b

thng th

ng bng 15% dung tch hu ch ca b. M phi

c vt ra khi b vch li mt lp dy khng qu 15 cm.b. Cc cng trnh ca trm XLNT tp trung. Cc cng trnh ca trm XLNT tp

trung thng c xy dng hp khi chia thnh hai nhm: nhm cc cng trnhlng kt hp ln men bn cn v nhm cc cng trnh x l sinh hc nc thi.

B lng hai v (b lng Imhoff) bao gm hai phn: mng lng v ngn bn.Nc thi chy vo mng lng phi c phn b u khp tit din ngang camng. Pha cui mng lng phi c tm chn ni (t su di mc nc khong 10- 15 cm). Cc cht ni, vng bn.... phi c vt thng xuyn. Khi lp cn trongngn bn ch cch khe h mng lng 1,0m th x cn ln men t u ra khi b.C sau 10 ngy th x cn mt ln. Lng bn gi li sau mt ln x ti thiu l 30%

tng lng bn trong b. Cn chn c m l 90% v trocao. Nu c bn niln trong vng lng hoc c bt kh trong vng mt thong ca b th iu chngt qu trnh ln men khng n nh v phi thc hin mt trong cc bin php sauy:

- Thay cn ln men khng n nh bng cn chn ca ngn bn hot ng tt;- Cho b ngng hot ng mt thi gian v b sung vi sa vo sau khuy

trn u.i vi b lng hai v kp cn phn phi u trong hai ngn bn, nh k

hai ngy mt ln phi thay i chc nng ca vo v ca ra ca mng lng.(Copyright Vietnam Water Forum - www.VinaWater.org)


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36

b lc sinh vt lm vic bnh thng cn phi:- Thng xuyn xem xt v ty ra thit b phn phi nc;- Thng xuyn xem xt khong khng y b, cc knh dn v phn phi

kh, cc mng thu nc. Trong trng hp b tc mng thu th phi ra bng nccp t h thng cp nc vo v thng r b;

- Loi tr lp bn thi ra trn b mt lp vt liu lc bng cch xc ra v rasch, sau xp li; Thng xuyn b sung vt liu thiu ht trong qu trnh ny;- Kim tra lng khng kh cp vo b, hiu sut thng gi... bng cch phn

tch mu nc (xc nh cc ch tiu ho l nhpH, xy ho tan...).i vi b aeroten, iu kin b lm vic n nh l phi bn hot tnh.

Nng th tch bn hot tnh, xc nh bng phng php o trong ng Imhoff,phi trn 200ml/l th b mi c th hot ng c. Khi nng th tch bn hottnh t 300 n 600 ml/l th b hot ng tt. Hm lng xy ho tan trong baeroten phi thng xuyn c m bo t 2 n 4mg/l. cc qu trnh sinh hotrong aeroten din ra n nh, cc my bm bn v my sc kh phi lm vic tcng sut yu cu v lin tc. Nc thi v bn hot tnh phi c trn u ti tt c

mi v tr trong b. Hiu qu XLNT trong b c xc nh qua cc ch tiu chtlng nc, nng xy ho tan, liu lng bn hot tnh. Khi ti lng hu c(BOD) trong b tng, bn hot tnh c th b trng, d to thnh cc ht nh, ri rcv kh lng. Trong bn xut hin nhiu vi sinh vt hnh si. Khi xy khng hocc cht c hi trong nc thi, hin tng ny cng thng xy ra. Mt s binphp khc phc hin tng bn trng nh sau:

- Tng cng sc kh;-X bn d;- Tm thi gim ti trng thu lc ca b;-Pha long nc thi bng nc sng, h;

- Tho kit, c sch v x t n

c thi mi vo b.Trng hp bn hot tnh trong b aeroten b ni c th do ti lng hu c quthp dn n qu trnh nitrat ho xy ra. Trong b lng t hai li din ra qu trnhkh nitrat, km theo vic ni bt kh nit. Mt bn gim xung n mc bn cth ni ln mt nc v trn ra khi b lng t hai. khc phc hin tng bnni, cn gim thi gian sc kh v c ra bn y v thnh b lng t hai.

i vi cc loi aeroten thi kh ko di, yu cu vn hnh v bo dng rtnghim ngt. V vy cc cng trnh ny i hi phi c cng nhn trnh cao theodi, qun l. Knh xy ho tun hon, mt dng aeroten thi kh ko di, c nng th tch bn hot tnh tun hon di 200ml/l. Bn tha phi thng xuyn a rakhi mng. Vic x bn v tho kit mng nn lm trong ma nng bn hot

tnh mi hnh thnh nhanh hn. Cc thit b c kh nhmy khuy, gung quay, mybm, van, kho... phi thng xuyn bo dng, bi du m...Trong trm XLNT phi c phng th nghim phn tch nc kim tra hiu

qu lm vic ca cc cng trnh. i vi cc trm XLNT cng sut di 1400m3

/ngy th mu nc c th c kim nghim ti cc phng phn tch nc ca cquan qun l mi trng a phng. Cc ch tiu phn tch thng l lu lng pH,nng xy ho tan, hm lng cn l lng, BOD, kim, liu lng bn hottnh, nng th tch bn hot tnh, hm lng nitrat, nit amn, photphat, fecalcoliform ... trong nc thi dng vo, dng ra v ngay ti cc cng trnh XLNT.



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PGS.TS Trn c H

37

Cng nhn vn hnh cc cng trnh XLNT phi c hng dn v quy trnhvn hnh cc cng trnh, cc nguyn tc v an ton lao ng v phng chy, chachy, cc bin php phng nga v khc phc s c ... Cc cn b k thut ca trmc nhim v:

- Bo m ch lm vic bnh thng ca tng cng trnh v ca ton trm;

- Bo m vic sa cha thng k v sa cha ln cc cng trnh v thit b;- Theo di vic ghi s trc ca cng nhn vn hnh cng trnh;- Lp cc bo co k thut v qun l cng trnh hng thng v hng nm;- Bo qun cc h s k thut tt c cc cng trnh v b sung cc tnh nng k

thut cc thit b, cng trnh vo cc h s ny trong qu trnh qun l;- Nghin cu ch hot ng ca tng cng trnh hon thin v ci tin

quy trnh vn hnh, bo dng ...- T chc cc lp hc nng cao trnh cho cng nhn, gii thiu cc nguyn

tc v an ton lao ng, phng chy, cha chy ....6.3.Xc nh chi ph qun l v vn hnh cc trm XLNT quy m va v nh.Cc trm XLNT quy m va v nh ph hp vi vic x l nc thi phn tn

hoc x l nc thi ti ch. Cng tc vn hnh k thut ca cc cng trnh XLNTquy m va v nh khng phc tp v khng i hi trnh cao nh i vi cctrm XLNT cng sut ln. Tuy nhin chi ph u t xy dng v chi ph qun lvn hnh cc trm nh xt trn tng th th th c th cao hn cc chi ph catrm XLNT cng sut ln. Mt khc, i vi h thng thot nc phn tn, mi trmXLNT c mt cng ngh ring nn vic qun l v vn hnh khng c thngnht, kim sot cht lng nc cng gp kh khn. Tuy nhin trong iu kin Vitnam v cc nc ang pht trin khc, h thng x l nc thi phn tn v x lnc thi ti ch ph hp vi kh nng u t theo tng giai on cng nh iukin t nhin ca mn.

Khi xc nh hiu qu kinh t ca trm XLNT cn phi xc nh sut u t

tnh cho mt m3 nc thi hoc tnh cho mt ng dn m h thng thot ncphc v. Song cng rt kh dn ra c cc gi tr tng qut do cc khon chi phlun thay i do gi c bin ng, mc thu khng n nh v iu kin mi aphng, mi khu vc mt khc. Chi ph u t cng ph thuc vo cng sut hthng thot nc v cng ngh trin khai. Mi quan h gia mc XLNT yu cuv chi ph x l tnh cho mt m3 nc thi c biu din trn hnh .21 sau y.

Chi ph C

4X l trit Kh BOD,N v P

3

2X l bc hai X l bc hai

1 bng bn hot tnhX l bc 1

30 70 100E ,% BOD c kh

Hnh .21. Biu quan h gia chi ph v hiu qu XLNT.(Copyright Vietnam Water Forum - www.VinaWater.org)


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Chi ph u t c lp theo nguyn tc lp h s d ton xy dng c bn ctnh n tt c cc yu t nh din tch t xy dng, chun b mt bng, san nn vh mc nc ngm,xy lp cng trnh, cc thit b lp t, ho cht v in nng vn hnh chy th , cc chi ph xy dng c bn khc v thu gi tr gia tng. Chiph xy dng gia cc cc cng trnh XLNT xy dng hp khi v khng hp khi

cng khc nhau rt nhiu. Khi xy dng hp khi cc cng trnh, din tch t xydng gim nhng chi ph cho kt cu cng trnh li tng ln rt nhiu. Kt hp ccao h, ng rung , bi t c sn XLNT th gi thnh xy dng trm s gim irt nhiu. Trong iu kin cho php , sau khi qua b t hoi, nu nc thi x l tich trong ao h sinh vt, bi lc ngm, ging thm ... th chi ph u t xy dng sgim i rt nhiu.Gi thnh x l nc thi bao gm chi ph khu hao v chi phqun l. Chi ph khu hao l c nh . Ngi ta thng ly chi ph khu hao trungbnh l 2,5% cho cc cng trnh thot nc v x l nc thi. i vi cng trnhtrn mt t chi ph khu hao ly l 1,25% v cng trnh di mt t l 5% chi phu t. i vi cc cng trnh XLNT hp khi gi thnh x l c th phn b nhsau / 6 /:

-Chi ph khu hao : 20-30%-Chi ph nng lng ( in , gas...): 25-40%;-Chi ph ho cht : 10-15%;-Chi lng v cc ph ph khc : 30-50%;-Sa cha thng k v bo dng thit b: 5-10%.

Quy m cng trnh cng nh, s ngi s dng trm XLNT cng t th chi phxy dng v chi ph qun l tnh cho mt ngi dn hoc cho mt mt khi ncthi x l cng tng. Chi ph vn hnh, qun l cc cng trnh XLNT l yu t cnphi tnh n khi la chn dy chuyn cng ngh XLNT. Cc biu thc xc nhgi thnh x l mt mt khi nc thi th C , c thit lp trn c s tng hp

cc s liu v chi ph vn hnh cc trm XLNT ca cc d n trong v ngoi n

ctrong nhiu nm qua / 7, 8/, nh sau.-XLNT bc 1 trong b lng v kh trng nc thi:

C=10,2Q-0,36 ,cent/m3 ( .9)

-XLNT bng phng php sinh hc v kh trng nc thi vi hiu sut xl < 90% khi BOD5 ca nc thi ban u di 250 mg/l :

C=23,8.Q-0,36 , cent/m3 ( .10)

-XLNT bng phng php sinh hc v kh trng nc thivi hiu sut xl < 90% khi BOD5 ca nc thi ban u t 250 n 500 mg/l :

C=34,8.Q-0,37

, cent/m3

( .11)

-XLNT bng phng php sinh hc v kh trng nc thi vi hiu sut xl >90% khi BOD5 ca nc thi ban u di 250 mg/l :

C=34.Q-0,36 , cent/m3 ( .12)

-XLNT bng phng php sinh hc v kh trng nc thivi hiu sut xl < 90% khi BOD5 ca nc thi ban u t 250 n 500 mg/l :

C=46,8.Q-0,37 , cent/m3 ( .13)(Copyright Vietnam Water Forum - www.VinaWater.org)


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-XLNT trong h sinh vt :

C=1,76.Q-0,41 , cent/m3 ( .14)

Trong cc biu thc trn y C l gi thnh x l 1m3 nc thi tnh theo cent v Q

l cng sut trm XLNT tnh theo nghn m3

/ngy.Chi ph nhn cng N, la M/nm , bao gm lng cng nhn trc tip vnhnh cng trnh, chi ph gim st, chi ph hnh chnh, bo him x hi, cng tcphng th nghim ..., theo T chc Bo v mi trng M EPA/ 28 / , xc nh nhsau:

N =8,31.Q0,717 ( .15)

Trong : Q- lu lng nc thi trung bnh trong ngy, m3/ngy.

Gi thnh xy dng v chi ph qun l vn hnh cc cng trnh thot nc v

x l nc thi sinh hot theo nghin cu ca T chc Bo v mi trng M ( EPA)/ 28 / c nu trong bng .19 sau y.

Bng .19. Gi thnh xy dng v chi ph qun l, vn hnh cc cng trnhthot nc v x l nc thi th theo nghin cu ca EPA.

Cng trnh Gi thnh xy dng C Chi ph vn hnh,qun l M

Thi hnphc v T

Cng thot nc t chy 4.512Q0,568 97Q0,301 50Trm bm chuyn bc 0,00004Q2+34Q+316.261 0,80Q+18.526 15X l s b bng b lng ct

v thit b chn rc

674Q0,611 0,96Q+25.038 30

X l s b bng b lng ctv khng c thit b chn rc

531Q0,616 0,96Q+25.038 30

Lng t mt c bm bn -0,00002Q2+19,29Q+220.389

1,69Q+11.376 50

B aeroten truyn thng 72Q+368.043 4,58Q+36.295 40B aeroten c ngn kh nit 90Q+612.777 93Q0,834 40B lng t hai sau aeroten 2941Q0,609 3,32Q+5.842 40B lc sinh hc cao ti -0,00007Q2+56,89Q

+244,791278Q0,505 50

B lng t hai sau b lc

sinh hc cao ti (k c bmtun hon)

-0,0000Q2+44,77Q

+323.702

-0,000003Q2+5,2Q

+5733

40

Ngn nitrat ho v b lng -0,00006Q2+77Q+636.567 -0,000005Q2+3Q+52.683

40

Ngn kh nitrat v b lng -0,00004Q2+45Q+398.838 14,5Q+61.827 40H thng clorat kh trng 795Q0,958 -0,000001Q2 +

2,36Q+24.81315

Trm bm bn -0,0000Q2+44,77Q+323.702

-0,000003Q2

+5,2Q+573310



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40

B nn bn trng lc 177Q0,68 -0,0000003Q2

+0,18Q+413650

B n nh hiu kh bn -0,00002Q2+23,7Q+208.627

8,54Q0,916 40

Sn phi bn 89Q0,854 -0,00002Q2

+2,57Q+800320

Thit b p lc bn cn 10.255Q0,481 3165Q0,348 15Cc cng trnh ph tr khc 1438Q0,567 -0,000003Q2

+1,97Q+57.34950

Ghi ch : Q- lu lng nc thi trung bnh trong ngy, m3/ngy; C- gi thnh xydng (xy lp v thit b ) ca cng trnh, la M; M- chi ph qun l v vn hnh cngtrnh, o la M/nm; T-thi gian hot ng ca cng trnh, nm.

Ti liu tham kho chng .

1. B Khoa hc,Cng ngh v Mi trng. Cc tiu chun Nh nc Vit nam v mitrng.Tp 1: Cht lng nc. NXB Khoa hc v K thut,1995.

2. B Xy dng. 20TCN 51-84: Thot nc, mng li bn ngoi v cng trnh-Tiuchun thit k. NXB Xy dng, H ni, 1989.

3. TCVN5576-91.H thng cp thot nc-Quy phm qun l k thut. H ni, 1992.4. B Xy dng. Quy chun h thng cp thot nc trong nh v cng trnh. NXB Xy

dng, H ni, 2000.5. TCXD 188: 1996. Nc thi -Tiu chun thi. NXB Xy dng,1996.6. Grul I. Cng trnh lm sch nc thi loi nh. NXB Xy dng,H ni, 1985.7. Trn c H. Bo co ti NCKH B94-16-6D-37.M hnh cc trm x l nc thi

cng sut nh trong iu kin Vit nam. Tr

ng i hc Xy dng,H ni, 1995.8. Trn c H. Bo co ti NCKH B96-34-06 X l nc thi v ph thi rn bnhvin. Trng i hc Xy dng, H ni, 1998.

9. Hong Hu. X l nc thi.NXB Xy dng, H ni,1996.10.Trnh Xun Lai.Tnh ton thit k cc cng trnh x l nc thi.NXB Xy dng,2000.11.Trn Hiu Nhu, Lm Minh Trit.X l nc thi. Trng i hc Xy dng,1978.12.Trn Hiu Nhu. X l nc thi bng phng php sinh hc. Trng i hc Xy

dng, 1990.13.U ban Nh nc Lin x v xy dng. Thot nc - H thng thot nc bn ngoi v

cng trnh ( Quy phm CII2.04.03-85CII2.04.03-85 ). Matscva,1986 (tingNga).

14.Karelin Ia.A. Jucp D.D. Jucp V.N.Repin B.N. X l nc thi cng nghip trongaeroten.NXB Xy dng , Matscva ,1973 ( ting Nga).15.Siphrin X.M. Thot nc.NXB i hc,Matscva,1970 ( ting Nga).16.Sinhep O.P.Tng cng x l sinh hc nc thi.NXB K thut , Kip,1983( ting Nga).17.Jacvlev X.V.Karelin J.A. v cc ngi khc. Thot nc.NXB Xy dng

Matscva,1975 (ting Nga).18.BS 629/:1983.British Standard Code of practice for Design and installation of small

sewage treatment works and cesspools. BSI,London,1983.



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41

19.Barnes D.,Wilson F. The Design and Operation of Small Sewage Works . E and F.N.Spon, London,1976.

20.Decentralised Wastewater Treatment in Developing Countries ( DEWATS). BORDA,Bremen,1998.

21.Degremont. Water Treatment Handbook. Paris,1979.22.

Eckenfelder W.W.Activated Sludge Treatment of Industrial Wastewater . EckenfelderInc., Tennessee, 1975.

23.Mara D.D. Sewage Treatment in Hot Climates. ELBS,1975.24.Mark.J. Hammer .Water and Wastewater Technology .Prentice Hall

International,Inc.,1996.25.Melcalf and Eddy Inc. Wastewater Engineering: Treatment, Disposal and Reuse, 3rd

edition, McGraw-Hill,Inc.,New York ,1991.26.Robert A.Corbitt. Standard Handbook of Environmental Engineering. McGraw -Hill,

Inc., New York,1990.27.Ronal L. Droste. Theory and Practice of Water and Wastewater Treatment. John

Wiley&Sons,Inc. New York,1997.28.Syed R. Qasim. Wastewater treatment plants. Technomic Publishing Co.Inc..1999.29.The Handbook on Water Treatment. Kemira Kemi AB,Helsingborg,1998.30.US EPA. Design Manual : On-site wastewater treatment and disposal systems. EPA

625/1-80-012, Office of water program operation . Washinton D. C., 1980.31.US EPA. Manual : Wastewater treatment / Disposal for Small Communities.Washinton

D. C., 1980.32.US EPA. Operation of Wastewater Treatment Plant . EPA Office of water program

operation. Washinton D. C., 1980.33.Veestra Ir.S.Wastewater Treatment. ZHE-DELF , 1995.34.Techniques et economie de l'epuration deseaux rsiduaires. Cahiers techniques de la

prventation des pollutions, Paris, 1980.



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th Trn 25.000 m2 Mc I8.Ch thc phm ti sng T 500 n 1.000 m2 Mc IV

T 1.000 n 1.500 m2 Mc IIIT 1.500 n 25.000 m2 Mc IITrn 25.000 m2 Mc I

9.Nh hng n ung, nh ncng cng, ca hng thcphm

D

i 100 m

2

Mc VT 100 n 250 m2 Mc IVT 250 n 500 m2 Mc IIIT 500 n 2.500 m2 Mc IITrn 2.500 m2 Mc I

10.Khu chung c Di 100 cn h Mc IIIT 100 n 500 cn h Mc IITrn 500 cn h Mc I

Ghi ch: i vi cc thng s khng c trong bng 1 th nng gii hn cho php ca nc xc nh theo TCVN 5945-1995.



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Ph lc 2.TCXD 188:1996- Nc thi th - Tiu chun thi

Urban Wastewater - Discharge Standards

1.Phm vi ng dng: Tiu chun ny quy nh nng gii hn cho php ca cccht nhim ch yu c trong nc thi th khi x vo ngun nc mt phc v lmngun cung cp cho trm x l nc nc n ung v sinh hot ( ngun loi A ) v voHTTN chung ca thnh ph ( ngun loi B).

2. Gi tr gii hn cc thng s nhim trong nc thi th.

TT Thng s n v Gi tr gii hnLoi A Loi B

1 Nhit oC 40 402 pH 6-9 5-93 mu Pt/Co 20 50

4 c NTU 50 1005 Tng cht rn l lng (SS) mg/l 50 1006 Tng cht rn ho tan mg/l 1.000 3.0007 COD mg/l 50 1008 BOD5 mg/l 20 509 Clorua (Cl-) mg/l 250 1.00010 Sunpht ( SO4

2-) mg/l 200 1.00011 Nitrit ( NO2

-) mg/l 0,1 2,012 Nitrat (NO3

-) mg/l 50 -13 Du m khong mg/l 0,001 1,014 Clo d mg/l 1,0 2,0

15 Coliform MPN/100ml 5.000 10.000Ghi ch: Nng gii hn ca cc ch tiu nhim khc khng nu trong bng ny c thxc nh theo TCVN 5945-1995.



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45

Ph lc 3.Nng gii hn mt s ch tiu nhim

trong cc thu vc nc mt theo quy nhca B Khoa hc, Cng ngh v Mi trng.

TT Thng s TCVN 5942-1995 TCVN5943-1995

TCVN6774:2000

TCVN6773:2000Loi A Loi B

1 pH 6-8,5 5,5-9 6,5-8,5 6,5-8,5 5,5-8,52 BOD5, mg/l 4 25 20 103 COD, mg/l 10 354 xy ho tan, mg/l 6 2 4 5 25 Cht rn l lng (SS),

mg/l20 80 25 100

6 Amonic ( tnh theo N),mg/l

0,05 1 0,1 1,49(pH=6,5)0,93(pH=8)

7 Nitrat( tnh theo N),

mg/l

10 15

8 Nitrit ( tnh theo N),mg/l

0,01 0,05

9 Du m, mg/l khng 0,3 khng khng10 Cht ty ra, mg/l 0,5 0,511 St, mg/l 1 2 0,112 Xianua, mg/l 0,01 0,05 0,01 0,00513 Asen, mg/l 0,05 0,1 0,05 0,02 0,05-0,114 Phenol tng s, mg/l 0,001 0,02 0,00115 Tng ho cht bo v

thc vt, mg/l0,15 0,15 0,05

16 Tng cht rn ho tan,mg/l 1.000 Theo ch sSAR17 Coliform, MPN/100 ml 5.000 10.000 1.000 200

cho vngtrng rau

Ghi ch: TCVN 5942-1995-Cht lng nc-Tiu chun cht lng nc mt ( loi A-ngun cung cp nc cho trm x l nc cp, loi B- ngun cung cp nc cho cc mcch khc ); TCVN 5943-1995 - Cht lng nc - Tiu chun cht lng nc bin ven b( trng hp dng lm bi tm); TCVN 6774:2000-Cht lng nc-Cht lng nc ngtbo v i sng thu sinh; TCVN 6773:2000-Cht lng nc- Cht lng nc dng chothu li.



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XLNT Quy mo nho

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