xlnt quy mo nho _tranducha

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Cng ngh v cng trnh X l nc thi quy m nh TS.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 tp trung . 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 thot nc tp trung m bo cho mi trng c an ton cao , t b nhim. X l nc thi (XLNT) tp trung d kim sot v qun l. Tuy nhin vic u t thot nc thi tp trung rt tn km do vic xy dng tuyn cng chnh ln, di v su, s lng 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 cng chnh s khng ph hp. u t kinh ph ln ngay t ban u cho cc cng trnh ny rt kh khn. Trong cc th ln do kh khn v khng kinh t trong vic xy dng cc tuyn 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 vc sng, h. Do c im a hnh v s hnh thnh cc knh h trong cc th nc ta, h thng thot nc thng phn ra cc lu vc nh v c lp . Thot nc phn tn s l hnh thc ph hp i vi a s th nc ta. Cc trm XLNT phn tn thng l loi quy m nh , cng sut t vi trm n vi nghn m3/ngy hoc 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 trm XLNT bnh vin, cc cng trnh cng cng, dch v... quy m cng sut t 50 n 500 m3/ngy s tn dng c cc iu kin t nhin cng nh kh nng t lm sch ca sng, knh, h chuyn ho cht bn. Mt khc vic xy dng ny cng ph hp vi kh nng u t v s pht trin ca th. S nguyn tc thot nc v XLNT phn tn c nu trn hnh .1. Nc thi sau khi x l t tiu chun cho php c x vo cc cng thot nc chung hoc cc sng, mng, h trong khu vc.

Trong nhiu trng hp mc XLNT ca h thng thot nc phn tn yu cu khng cao do tn dng c kh nng t lm sch ca cc sng h . Tng gi thnh u t cho h thng thot nc thi phn tn gim xung do khng phi xy dng cc tuyn cng thot nc thi tp trung. Cc cng trnh ca trm XLNT phn tn 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 quan do vic xy dng trm x l nc thi bn trong th. Nu thit k thi cng v vn hnh 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 cc nguyn t dinh dng nh N v P trong nc thi sau x l cn cao, trong iu kin quang hp tt, cc sng h th tip nhn nc thi c th b ph dng

www.tainguyennuoc.vn

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(eutrophication) v dn n nhim bn th cp. Mt s kt qu nghin cu /8/ cho thy, trong cc sng h tip nhn nc thi th hm lng cht hu c (tnh theo BOD5) b sung do nhim bn th cp thng dao ng t 1,4 n 4,5 mg/l. Cc trm XLNT phn tn c quy m , mc v cng ngh x l khc nhau . Vic kim sot, 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 thng thch hp cho cc th c h thng thot nc chung hoc h thng thot nc na ring, nm trong cc vng a hnh bng phng nhiu knh, h. V d h thng thot nc thi H ni c chia thnh 7 vng theo phng n quy hoch ca T chc hp tc Quc t Nht bn (JICA) nm 1994 hoc thnh ph lt thnh 4 khu vc theo D n thot nc v v sinh nm 1999 (hnh ..2) .

Ngun nc sch b cp pha long nc 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 thi

Trm 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 thot nc tp trung, ngi ta thng t chc h thng thot nc thi cc b kt hp x l 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, c cho thm vo t , thi trc tip vo sng h ln cn hoc s dng ti cy, nui c... 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 thi bnh vin, nc thi cng nghip...) phi c kh trng hoc kh c trong cc cng trnh x l cc b, m bo iu kin khng nh hng xu n hot ng ca h 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 trng hp 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 m va ( cng sut t 1000 n 10.000 m3/ngy ); cc trng hp th hai v th ba l cc trm quy m nh (cng sut di 1.000 m3/ngy). T chc thot nc khu vc Linh m - nh cng- Php vn pha Nam H Ni l mt v d v cc h thng thot 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 nc..... X l nc thi ti ch vi cng trnh ch yu l b t hoi hoc b lng hai v 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 kt hp ln men cn lng nn hiu qu x l cao, qun l vn hnh n gin. Nc thi v 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 dn c nn iu kin v sinh ca n cn hn ch.


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Khu vc Thi phin Nc thi B t hoi Bi lc ngm ti hoa ra sui Khu vc p Chi lng Nc thi B t hoi Bi lc ngm h Than th Khu vc h Xun hng H Xun hng Khu vc sui Cam ly 1 2 Khu vc trung tm sui 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 tng thot 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, nh ncng to ra cc loi nc thi c thnh phn v tnh cht tng t nh nc thi sinh hot. tin cho vic la chn phng php dy truyn cng ngh v tnh ton thit k cc cng trnh x l nc thi quy m nh, nc thi sinh hot c phn loi theo cc du hiu sau y: a.Theo ngun gc hnh thnh, trong cc h gia nh c th c cc loi nc thi 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 nc thi khc

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

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, ngi ta 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 cht l lng, cc cht ty git v thng gi l nc xm . Nng cc cht hu c trong loi nc thi ny thp v thng kh phn hu sinh hc. Trong nc thi nhiu tp cht v c. -Nc thi cha phn, nc tiu t cc khu v sinh (toilet) cn c gi l nc en. Trong nc thi tn ti cc loi vi khun gy bnh v d gy mi hi thi. Hm lng cc cht hu c (BOD) v cc cht dinh dng nh nit, pht pho cao. 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 to kh sinh hc. - Nc thi nh bp cha du m v ph thi thc phm t nh bp, my ra bt. Cc loi c hm lng ln cc cht hu c (BOD,COD) v cc nguyn t dinh dng khc (ni t v pht pht). Cc cht bn trong nc thi ny d to kh sinh hc v d s dng lm phn bn. Mt s ni ngi ta nhm hai loi nc thi th hai v th ba , gi tn chung l "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 thu gom v vn chuyn theo ng cng chung v trm x l. S lng thnh phn v tnh 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 nh b tch du m, b t hoi , sau cng nc xm x vo tuyn cng thot nc chung ca thnh ph. Vic phn loi nc thi theo h thng thot nc ph thuc vo i tng thot nc, c im h thng thot nc ca th hoc khu dn c v cc iu kin 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 khu vc dn c, tiu chun thi nc t 120 n 180 l/ngi.ngy, xc nh theo Quy chun xy dng Vit nam nm 1996/1/. Tiu chun thi nc bnh vin thng thng 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 lng cn b cng nhn vin v ngi nh n chm nom bnh ln, tiu chun dng nc thc t tng ln rt nhiu v n cng ph thuc vo quy m cng nh chc nng ca bnh vin , dao ng t 500 n 1000 l/ging.ngy. d xc nh lu lng v nng cht bn trong nc thi sinh hot ca cc cng trnh cng cng hoc dch v ngi ta thng tnh ton, chuyn i cng sut (quy m) cng trnh sang ch s dn tng ng. l s n v phc v ca cng trnh cng cng, dch v c lng cht bn hoc nc thi x vo h thng thot nc tng ng vi ca mt ngi dn th. Cc i lng tng ng ny ca mt s cng 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 trnh cng cng, dch v.

Cng trnh n v tnh Ch s dn

tng 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

Ging Ch ngi

Ch Ch

Hc sinh Tr em

Ging bnh

1 3 15

510 10

23 0,40,5

200-300 50-80 10-15 8-25 15-25 50-100 300-600

Mt yu t c bn khc lin quan n vic tnh ton thit b mng li thot nc v cc cng trnh x l nc thi l ch thi nc. Lu lng nc thi chy n 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, lng nc thi rt nh. Trong thi gian cao im, lu lng nc thi c th ln gp 6-8 ln thi im trung bnh. Trng hp nhiu thit b v sinh cng hot ng ng thi th nc thi chy lin tc ti trm x l. Ch thi nc c trng bng h s thi nc khng iu ho chung Kch. l t s gia lu lng nc thi trong gi dng nc ln nht ca ngy dng nc ln nht (qh,max) vi lu lng nc thi trong gi dng nc trung bnh ca ngy dng nc trung bnh (qh,tb). Nh vy:

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 c

A- Th t; B- Khu nh 200 ngi; C- Khu th 50.000 ngi

Gi tr Kch ph thuc vo s ngi s dng h thng thot nc, tiu chun dng nc, iu kin trang thit b v sinh v iu kin kh hu. Lu lng nc thi cng ln h s Kch cng nh. Da vo h s Kch c th xc nh c lu lng nc thi tnh ton ca h thng thot nc v cc cng trnh x l nc thi. i vi h thng nc thi quy m va v ln, h s Kch c th xc nh theo cc cng 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 tnh ton 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 s dng 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 nc tng ng t 2 n 3 ln.Theo cc tiu chun thit k cp thot nc hin hnh, h s 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 lp quy 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 ... do mt ngi trong mt ngy x vo h thng thot nc sinh hot ca mt s nc c 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 xc nh theo bng .2.

Bng ..2. Ti lng v nng cht bn trong nc thi sinh hot t cc ngi nh

hoc cm dn c c 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 65-85 380-500Cn 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 nc ln. Lng cht bn tnh theo n v 1 ging bnh thi vo h thng thot nc trong mt ngy l: -Cht bn l lng : 130g


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-BOD5 : 70g -Nit amn : 16g -Clorua : 18g Nng 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

PH Cht l lng, mg/l BOD5 , mg/l COD , mg/l Tng s coli form, MPN/100ml

6.2100 110 140 106

7.4160 150 200 107

8.1220 250 300 109

Trong nc thi bnh vin cn cha cc cht thi ty ra, d lng dc phm v mt s cht c hi c trng t qu trnh chn on, xt nghim bnh nhn... c trng ca nc thi bnh vin l s xut hin ca cc loi vi khun gy bnh nh Somonella, Leptospira,Vibrio Choleral, Mycobacterium Tuberculosis... .3. Cc phng php x l nc thi . .3.1. Mc x l nc thi Mc 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 nc mt loi A vi mc ch s dng cho cp nc sinh hot v cng nghip thc phm v ngun nc mt loi B vi vic s dng nc cho cc mc ch khc. Nng gii hn cho php ca cc cht nhim trong cc loi 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 tnh n kh nng t lm sch ca ngun khng c lm cho nng cht bn ti im kim tra s dng nc vt nng gii hn cho php. iu kin , khng ch i vi nc thi khi x vo ngun nc mt c quy nh theo tiu chun thit k nc th 20TCN 51-84 hoc tiu chun mi trng TCVN 5945-1995, TCVN 6772:2000 (ph lc 1).Theo cc quy nh ny, nc thi mt s ch tiu trong sinh hot 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 sinh

hotkhi x vo ngun nc (Theo TCVN6772:2000)

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

1 pH 5-9 5-9 5-9 5-9 5-9 2 BOD5, mg/l 30 30 40 50 200 3 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 KQ 5 Tng cht rn ho tan, mg/l 500 500 500 500 KQ 6 Sun phua(theo H2S), mg/l 1,0 1,0 3,0 4,0 KQ 7 Nitrt (NO3

-), mg/l 30 30 40 50 KQ 8 Du m (thc phm), mg/l 20 20 20 20 100 9 Phosphat (PO4

3-), mg/l 6 6 10 10 KQ 10 Coliform, MPN/100ml 1.000 1.000 5.000 5.000 10.000

Ghi 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 thi nc sinh hot quy m nh v va cng phi da trn hai iu kin cn v nu trn. Vic kim sot nhim xc nh mc XLNT cn thit cho khu dn c hoc th c thc hin theo s nu trn hnh .5.

Nc thi cc x nghip cng nghip

Nc thi khu dn c Kim sot theo 20TCN51-84 i tng s dng nc Kim sot theo tiu chun cht lng nc s dng Trm XLNT Trm cp nc Kim sot theo TCVN6772:2000 hoc TCXD 188:196 im x im ly nc im kim tra Kim sot theo TCVN 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 .6 sau y: -Bc th nht ( x l bc mt hay x l s b ): Lm trong nc thi bng phng php c hc loi cn v cc cht rn ln. y l mc bt buc i vi tt c cc dy chuyn cng ngh XLNT. Hm lng cn l lng trong 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 khun gy bnh dch (cc bin

php ho hc hoc vt l)

Tch rc, ct v cn lng trong nc thi

(cc bin php c hc)

Kh cc cht c hi v m bo iu kin lm vic bnh

thng ca cc cng trnh x l sinh hc nc thi (Cc bin

php c hc, ho hc hoc ho l)

Tch cc cht hu c trong nc thi (bin php sinh

hc)

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

hoc hoc ho l)

X nc thi ra ngun v tng cng qu trnh t lm sch

cangun nc

T lm sch ca ngun 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 php sinh hc. Giai on x l ny c xc nh trn c s tnh trng s dng v qu trnh t lm sch ca ngun nc. -Bc th ba (x l bc ba hay x l trit ): loi b cc hp cht nit v pht 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 i vi 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 th xc 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 nhn

nc thi Mc XLNT

Cht l lng, mg/l

BOD5, mg/l Coliform MPN/100ml

1 Lu vc c lp Q=10005000

m3/ng

Sng h th

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Cc trm x l nc tha cng sut nh v va phi m bo mt lot cc yu cu nh xy dng n gin, d hp khi cc cng trnh, din tch chim t nh, d qun l v vn hnh v kinh ph u t xy dng khng ln. Yu t hp khi cng trnh l mt trong nhng yu t c bn khi xy dng cc trm x l cng sut nh v va 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 m quan th Nc thi sinh hot c th x l ti ch trong cc cng trnh lm sch s b ( tch du m, tch v x l cn trong nc en), trong cng trnh x l cc b i vi h thng thot nc c lp hoc trong cng trnh x l tp trung ti trm x l khu vc. XLNT ti ch s lm gim chi ph u t xy dng cc tuyn cng thot nc.

Theo c ch qu trnh lm sch, cc phng php XLNT sinh hot quy m nh v va c phn ra nh sau: 1.XLNT bng phng php c hc trong cc cng trnh v thit b nh song chn rc, b lng ct, b tch du m. y l cc thit b, cng trnh x l s b ti 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 vi cc h thng thot nc quy m nh v va ngi ta thng dng cc cng trnh kt hp gia vic tch cn lng (lm trong nc ) vi phn hu him kh cc cht hu c trong pha rn v pha lng. Cc cng trnh c ng dng rng ri l cc loi b t hoi, ging thm, b lng hai v (b lng Imhoff), b lng trong kt hp vi ngn ln men, 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 nc thi 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 trnh x l sinh hc hiu kh trong iu kin nhn to. Ngc li, nu xy c vn chuyn v ho tan trong nc nh cc yu t t nhin th l qu trnh x l sinh hc hiu kh trong iu kin t nhin. Cc cng trnh x l sinh hc hiu kh trong iu kin nhn to thng c da trn nguyn tc hot ng ca bn hot tnh ( b acroten trn, knh xy ho tun hon.) hoc mng sinh vt (b lc sinh vt, a sinh vt ). X l sinh hc hiu kh trong iu kin t nhin thng c tin hnh trong h ( h sinh vt xy ho, h sinh vt n nh) hoc trong t ngp nc ( cc loi bi lc, m ly nhn to). 4.XLNT bng phng php ho hc. l cc qu trnh kh trng nc thi bng 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 php ho hc thng l khu cui cng trong dy chuyn cng ngh x l trc khi x ra 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 nh rc, ct, cn lng...Cc loi ct ( ch yu l thnh phn v c v t trng ln) c phi 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 ) c hm lng hu c ln c kt hp vi bn th cp ( ch yu l sinh khi vi sinh vt d ), hnh thnh trong qu trnh x l sinh hc nc thi, x l theo cc bc tch


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nc s b, n nh sinh hc trong iu kin ym kh hoc hiu kh v lm kh. Bn cn 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 lng cht hu c ( BOD,COD) trong nc thi. Cc phng php ln men k kh thng ph 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 ch cho chng tip xc vi mng sinh vt l hp l. S chn la cc phng php x l 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 ca

nc thi Cht hu c khng

ho tan Cht hu c dng

keo Cht hu c ho

tan 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 bng phng 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 phn nitrat. Trn c s nghin cu s hnh thnh h thng thot nc quy m nh nh v va, c im cc ngun nc thi th v iu kin t nhin kinh t x hi nc ta c th thit lp s t chc XLNT cho cc khu dn c, th trn th x, cc cng trnh cng cng v dch v ( hnh .7 ). Theo s hnh .7, nc thi cc i tng thot nc u phi x l qua giai on tch cc cht rn ln nh rc, ct, cn lng. Cc loi cn lng c x l ch 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.


PGS.TS Trn c H

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Nc thi ngi nh hoc khu dn c c lp Q

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16

.4.Mt s cng trnh c trng x l nc thi quy m nh. .4.1.B t hoi . B t hoi l 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, xy dng bng gch, b tng ct thp, hoc ch to bng vt liu Composite. B c chia thnh 2 hoc 3 ngn. Do phn ln cn lng tp trung trong ngn th nht nn dung tch ngn ny chim 50 n 75% dung tch ton b. Cc ngn th hai hoc th ba ca b c dung tch bng 25% n 35% dung tch ton b. B thng su 1,5 n 3,0m, chiu su lp nc trong b t hoi khng b hn 0,75m v khng ln hn 1,8m, chiu rng ca b ti thiu l 0,9m v chiu di ti thiu l 1,5m. Th tch b t hoi khng nh hn 2,8m3 trong th tch phn lng khng nh hn 2,0m3. Cu to mt s loi b t hoi hai ngn hoc ba ngn c nu trn cc hnh .8.

Hnh .8.S cu to b t hoi a.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 t 1 n 3 ngy. Do vn tc trong b b nn phn ln cn l lng c lng li. Hiu qu lng cn trong b t hoi t 40 n 60% ph thuc vo nhit v ch qun l, vn hnh b. Qua thi gian 3 n 6 thng, cn lng len men ym kh. Qu trnh ln men ch yu din ra trong giai on u l ln men axit . Cc cht kh to nn trong qu trnh phn gii (CH4,CO2,H2S...) ni ln ko theo cc ht cn khc c th lm cho nc thi nhim bn li v to nn mt lp vng ni trn mt nc. Chiu dy 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 khc c nh ln pha trn tin kim tra v ty ra. Cn trong b t hoi c ly ra theo 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 c tnh nh sau.

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

1000.. 1

1TNaW = , m3 (.3).

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

1000.. 2

2TNbW = , 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- tiu chun cn lng li trong b t hoi ca mt ngi trong mt ngy; gi tr ca b ph thuc vo chu k ht cn khi b; nu thi gian gia hai ln ht cn di 1 nm th b ly bng 0,1 l/ng.ngy, nu trn 1 nm th b ly bng 0,08 l/ng.ngy; T1- thi gian nc lu li trong b t hoi; T2- thi gian gia hai ln ht bn cn ln men thng ly 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 chun cp 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 nh

v cn h Th tch ti thiu ca b t

hoi , m3 1 hoc 2 phng ng 3 hoc 2 phng ng 4 hoc 2 phng ng 5 hoc 6 phng ng

2 cn h 3 cn h 4 cn h 5 cn h 6 cn h 7 cn h 8 cn h 9 cn h 10 cn h

2,8 3,8 4,5 5,7 7,6 8,5 9,5 10,5 11,4 12,3 13,3

. Kch thc ca mt s loi b t hoi BTCT thng c ng dng Vit

nam c nu trong bng .8.


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

Dung tch cng Kch thc b ,m tc ca b W,

m3 Chiu di ngn

th nht Chiu di

ngn th hai Chiu rng Chiu su cng

tc 2 3 4 5 10

2,4 2,6 2,2 2,4 3,0

- 1,0 1,1 1,2 1,5

0,9 1,0 1,1 1,2 1,5

1,0 1,0 1,1 1,2 1,5

B t hoi c th a vo s dng ngay sau khi xy dng. N khng cn mt

yu cu c bit no trc khi a vo vn hnh. Tuy nhin s ln men bn cn phi bt 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 my bm 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 hp bn cn nc thng c BOD5 khong 6.000mg/l, tng cc cht rn (TSS) khong 15.000 mg/l, tng nit khong 700 mg/l ( trong N-NH3 l 400 mg/l), tng pht pho khong 250 mg/l v tng du m khong 8.000 mg/l. Bn cn ln men c lm kh trn sn phi bn, trong hm lm phn compot hoc x l tip tc trong cc bi lc ngp nc trng cy pha trn.

Khi ra khi b COD ca nc thi gim t 25% n 50%. Nng cc cht bn 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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Cng trnh XLNT H thng thot nc XLNT tip tc hoc tip nhn nc thi

V tr xy dng cng

trnh v iu kin t ai

thun li

B t hoi

Nc thi t chy,

gin on

Ging, ho, b

hoc bi thm hot ng gin on

theo chu k

V tr xy

dng v iu kin t ai kh khn

B t hoi tip theo l h thng

x l sinh hc hiu kh hoc b lc ct

hot ng gin on

Nc thi c

bm v phn phi, nh lng theo

chu k

Ho hp ph, ho hoc bi bay hi

nc, bi lc ngp nc, kh trng v

x nc thi ra ngun 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 khi la chn cc cng trnh XLNT tip sau b t hoi. S hot ng ca b t hoi kt hp vi mt s cng trnh XLNT khc trong iu kin t ai thun li v t ai kh 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.


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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 ln vi 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 ct , si v xy ho k kh cc cht hu c c hp ph trn lp ct si . Nc thi sau khi x l c thm vo t . Do thi gian nc lu 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 l bng phng php lng trong b t hoi hoc b lng hai v . Ging thm cng ch c s dng khi mc nc ngm trong t su hn 1,5 m m bo c hiu qu thm lc cng nh khng gy nhim nc di t . Cc loi t phi d thm nc , 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 . Ging thm cng c th c lp t bng cc ng ging . Thnh ging b tng b dy ti thiu 100 mm, c b tng mng vng chc .


PGS.TS Trn c H

21

d

lp nc

>=300

200

si x

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 thot nc . 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 nc phc v, m2/ngi .

Loi t

Lng nc hp th ln nht

trong 24h, l/m2

Nh ,q=200

l/ng.ngy

H gia nh q=100

l/ng.ngy

Trng hc q=65

l/ng.ngy Ct th hoc si 205 0,93 0,23 0,14Ct mn 163 1,4 0,37 0,23Ct pha st 102 2,3 0,6 0,37St ln nhiu ct hoc si

45 3,7 0,93 0,6

St ln t ct hoc si

33 7,1 1,85 1,25

St nng , t cng hoc cc loi t khng thm nc khc

Khng s dng .

Ging thm c lt si , dm .. c nh dn t di ln . Lp trn cng c bng ct mn v c chng xi nc bng tm chn . tng kh nng thm nc ca ging, bn ngoi ging thm si.Vic thng thong c thc hin qua ng thot nc hoc dng ng thng hi ring . b.Bi lc ngm. Nu nc ngm gn mt t v khng th xy dng ging thm th c th xy dng h thng bi lc ngm . Nc thi trc khi qua bi lc ngm phi c lng s b trong cc cng trnh x l c hc . Khi i qua lp t bi lc ngm , cc cht bn trong nc thi s c hp ph theo con ng thm lc ,


PGS.TS Trn c H

22

sau c xy ho sinh ho. Thng thng trong lp t pha trn din ra qu trnh xy ho hiu kh v trong lp t pha di din ra qu trnh h hp k kh cc cht hu c . Do lp t khng ln ( t 0,6 n 0,9 m ) nn vo thi k pht trin ca cy trng , mt khi lng ln nc thi c r cy hp th v ch mt phn nc 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 thng phn 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, h thng phn phi t cch mc nc ngm khng nh hn 1 m v thng b tr trong ho. 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 tr Ti thiu Ti aS 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,


PGS.TS Trn c H

23

chiu dy lp t ph, m ca t ... Theo cc nghin cu ca Vin nghin cu a cht thu vn v cp thot nc Lin x / 16 /, hiu qu x l nc thi c th xc 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 n mp mng thu nc hoc n mc nc ngm, m; h-chiu dy lp t ph pha trn vt liu lc, m; a-khong cch gia cc ng ti,m; a-ng knh trung bnh ca ht vt 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 hc a 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 tr thnh dy ni tip quay u trong b cha nc thi. S b tr h thng a lc c nu trn hnh .13.

t mtB lng

Nc thi vo

H thng a lc sinh hc

t haiB lng

Nc thi sau khi 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 bn cn 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 )

hW

ad(

q

HT450

L

L =


PGS.TS Trn c H

24

nc thi. Qu trnh hp ph v dnh bm cc cht hu c dng ho tan, keo v vy bn ln mng sinh vt hnh thnh trc , c din ra. Khi quay ln pha trn, vi khun 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 trn mt 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 cng sut 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 ton da 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 a lc sinh hc c nu trong bng .11.

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

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

q

QA = , m2 (.7)

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


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25

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

c tnh Gi tr Ti 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 0,005 Phn din tch a ngp nc, % 40 S dy a 4 Khe h gia cc a, cm 2-3 ng 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 t din ra cc qu trnh thi kh, lng bn v gn nc thi. Do hot ng gin on nn 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: lm

y 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 hot

tnh lu li t chu k trc. Sau y hn hp nc thi v bn c sc kh bc hai vi thi gian thi kh ng nh thi gian yu cu. Qu trnh din ra gn vi iu kin trn hon ton v cc cht hu c c xy ho trong giai on ny. Bc th ba l qu trnh lng bn trong iu kin tnh. Sau nc trong nm pha trn lp


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26

bn c x ra khi b. Bc cui cng l x lng bn d c hnh thnh trong qu trnh thi kh ra khi ngn b, cc ngn b khc hot ng lch pha m bo cho 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 vi bn, lng bn cn ... din ra gn ging iu kin l tng nn hiu qu x l nc thi cao. BOD ca nc thi sau x l thng thp hn 20 mg/l, hm lng cn l lng t 3 n 25 mg/l v N-NH3 khong t 0,3 n 12 mg/l. B aeroten hot ng gin 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 trong b bng vic thay i ch cung cp xy. Cc ngn b c sc kh bng my nn kh, my sc kh dng Jet hoc thit b khuy trn c hc. Chu k hot ng ca ngn b c iu khin bng rle thi gian. Trong ngn b c th b tr h thng vt vng, thit b o mc bn, ...

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


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 hu c/lng bn

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

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

nc thi Lng xy Cp cho qu trnh xy ho cht hu c v

nitrat ho nh i vi cc aeroten truyn thng B aeroten h SBR c u im l cu to n gin, hiu qu x l cao, kh

c cc cht dinh dng nit, d vn hnh. S dao ng lu lng nc thi t nh hng n hiu qu x l. Nhc im chnh ca b l cng sut x l nc thi nh. b hot ng c hiu qu ngi vn hnh phi c trnh v theo di thng 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 cn trong nc thi. Nc thi sinh hot cha lng ln cc cht hu c v cc cht dinh dng cn thit cho cy trng, vt nui ... Thnh phn chnh ca nc thi sinh hot c nu 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.nm

Nc xm Nc tiu Nc phn

Nit 4-5 3 87 10Pht pho 0,75 10 50 40Kali 1,8 34 54 12COD 30 41 12 47Nguyn tc x l v ti s dng

X l sau ti s dng hoc x vo ngun nc

X l v lm phn bn trc tip cho cy

X l, sn xut kh sinh hc v cung cp cht dinh dng b sung cho t


PGS.TS Trn c H

28

T l cc nguyn t dinh dng trong nc thi sinh hot c nu trong bng 1.18. 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 150 l/ng.ngy

Phn chung 0,087

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 100 mg/l , ph thuc vo tiu chun dng nc , loi nc thi , c im cng trnh cng cng ...Nit ban u ch yu tn ti di dng nit hu c, nit amn v nit nitrat. T l hm lng cc dng nit ny quyt nh th t u tin x l nc thi trong 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 vn chuyn nc thi vo t , pht pho hu c s b chuyn ho sinh hc thnh pht pht. Trong mi trng t kim tnh , pht pht s kt hp vi in canxi to thnh canxi 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 hp th. 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 v bn cn ca n lm phn bn ngy cng tng. Hin nay, ngi ta thng c cc quan 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 v ti 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 ti ph thuc vo c im t, cy trng v nng cc cht trong nc thi v dao ng t 0,1 n 0,2 m/nm (1000m3/ha n 20000m3/nm ). Phng php ti l ti ngp hoc ti phun khi dng nc thI ti sn lng cy trng s tng thm 20% n 30%.

Qu trnh x l nc thi sinh hot s to nn lng ln bn cn ( bng khong 1% th tch nc thi x l ). Gi tr phn bn ca tng loi bn cn nc thi c nu trong bng .15 v hm lng cc nguyn t vi lng c nu trong bng . 16.


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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 dinh dng

Cn ti Bn cn ln men

Bn hot tnh

Phn chung

Ni Pht pho Kali

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

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

2,4-6,5 2,3-8,0 0,3-0,4

2,0-2,61,6-1,3 1,8-1,9

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

Trong nc thi v bn cn ca n c cha cc loi vi khun gy bnh, trng giun 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 vi khun Shigella v 1.000 vi khun Vibrio cholera trong 1 lt nc thi. Cc loi vi khun Shigella v Vibrio cholera nhanh chng b tiu dit trong mi trng nc thi nhng vi khun Salmoella c kh nng tn ti lu di trong t. Cc loi virut cng xut hin nhiu trong nc thi. Ngoi ra trong nc thi sinh hot cn c nhiu cc loi trng giun sn nh Ancylostoma, Ascaris, Trichuris v Taenia... v


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 c th tn ti trong t n 1,5 nm. V vy nn hn ch ti nc thi trong ma thu hoch. 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 thi cc 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 trong cc 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/kg Cd, mg/kg Cu, mg/kg Hg, mg/kg Pb,mg/kg Zn, mg/kg

2-26 2-1500 50-3300 0,1-55 50-3000 700-49000

2,2-1200,05-8,5

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 trong vc 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 ho tip tc cc cht hu c m cn tng hp nn prtin trong sinh khi. Trong h, to v 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, vi khun 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 to nn sinh khi l 200310 mg/l sinh khi giu protein. Khong 50% tng protin sinh khi ca cc ao h c ngun gc t to. To s dng nng lng t nh sng mt tri, CO2 v cc nguyn t khong khc nh N,P,K tng hp sinh khi. Sn lng 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 tnh sinh 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 270La 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 trng gy bnh trong nc thi c nui trng to c th b dit n 99,9%. Dch to c thu hi bng cc phng php c hc lm dc phm, lm thc n cho gia sc hoc 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 tnh sn phm cao .


PGS.TS Trn c H

32

nh sng Nc thi Sinh hot Bn hot tnh CO2 tun hon Bn cn CH4 nhin CO2 liu Bn cn ln men s Nng lng dng 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 ca h sinh thi vn-ao-chung (VAC). To khng cn thu hi m c s dng trc tip lm thc n cho cc ng vt nguyn sinh, c vt . Phn ln cc loi vi khun gy bnh, cc cht hu c c trong nc thi sinh hot c lm sch nn nc thi 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 c c sn lng cao thng c nui trong mi trng nc thi l c trm, m, r phi Sn lng c nui cc vng nc thi nc ta cng nh mt s nc khc nh n , Thi Lan, Philipin/ 23 / dao ng t 1,0 n 3 tn/ha.nm. S h thng 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; cn c hi i hi lng oxy trn 6 mg/l. Tuy nhin hm lng xy ho tan ph thuc vo ti lng BOD trong h. Trong iu kin nhit i ti lng ny khng ln hn 1gBOD/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 vt ba 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 sinh vt bc ba p ng yu cu cho php vi ngun nc nui c theo quy nh ca t

B lng t 1

B

Aroten

B lng t 2

H nui to

Tch to

Nc nui

c hoc ti rung

B ln men k kh

B cha kh

X l kh thi

Pht in

Lm kh

Trit trng

Sn phm

to


PGS.TS Trn c H

33

chc y t th gii. Khi s dng h t nhin hoc h th nui c cn phi bit c hot ng nh mt cng trnh x l hay ngun tip nhn nc thi.

Hnh .19. S h thng x l kt hp s dng nc thi quy m nh

( h sinh thi VAC).

Nc thi

Hnh .20. S h thng x l nc thi bng h sinh vt kt hp nui c. .6. Cc quy nh chung v qun l,vn hnh cc cng trnh x l nc

thi quy m nh

.6.1. a cng trnh vo hot ng Yu cu i vi cc cng trnh x l nc thi l phi hot ng n nh, ng quy trnh. a cng trnh vo hot ng, cn c cc h s k thut sau y: - Cc vn bn nghim thu cng trnh; - Giy tho thun mi trng cho php a cng trnh vo hot ng; - Cc bn v hon cng; - Cc ti liu hng dn lp t v s dng cc thit b, cng trnh x l nc thi. Trc khi a cng trnh vo s dng phi thu dn sch s cc vt, t ... Sau tin hnh kim tra s hot ng ca cng trnh bng nc sch. u tin tin hnh th kn kht ca cng trnh, sau kim tra cc thng s thy lc, s lm vic ca cc van, phai chn nc cng nh tng b phn ca thit b. Ch sau khi

B lng

H k kh

H ty tin H nui c

(Lm thong t nhin)

Nc thi sinh hot v

B t hoinc thi chung tri

Nc thmTi rau

Nc rachung tri

Ao nui to Ao nui c v vt

Nc pha long Mthane


PGS.TS Trn c H

34

kim tra xong mi c dn nc thi vo cng trnh. Khng nn x kit nc khi cng 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 gian a cng trnh vo hot ng, thi gian khi ng... Cng vic ny cn cc chuyn gia 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 thi

gian khi ng B t hoi Lng cn: Sau 1 3 ngy

Ln men cn lng: Sau 3 thng

a lng cn ln men bng khong 15 20% dung tch phn cha cn gy men

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

a lng cn ln men bng khong 15 20% dung tch phn cha cn gy men

B lc k kh T 2 3 thng

Lu lng nc thi cp cho b trong thi gian khi ng tng dn t 25% n 100% lu lng thit k

B lc sinh hc T 2 3 thng cho n khi xut hin nitrat trong nc thi sau x l

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

B Aeroten T 1 n 2 thng cho n khi ch s bn o trong bnh Imhoff l 200 300 ml/l (nu c bn hot tnh t ni khc a v th thi gian ny gim xung cn t 2 tun n 1 thng)

Cho bn hot tnh ly t ni khc sc kh vi khong 30% lu lng nc thi trong thi gian u. Sau tng dn cng sut cp nc thi cho n khi ch s bn l 200 300 ml/l

H sinh hc T 2 n 3 thng sau khi hnh thnh h sinh vt trong h

Giai on u c th bm nc sng vo y h, sau x nc thi dn dn vo h

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

Trong thi gian a cng trnh vo hot ng, cn tin hnh nghin cu, phn tch nc thi xc nh c l cng trnh c m bo lm sch theo yu cu hay khng. Cc s liu thu nhn c trong giai on ny c b sung vo quy trnh vn hnh cng trnh XLNT. Nc thi a v cng trnh trong giai on ny c lu 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 tip qun l cng trnh XLNT phi nm c cc qu trnh c bn din ra cng trnh


PGS.TS Trn c H

35

..iu kin qun l vn hnh cc cng trnh XLNT rt nghim ngt v vy i hi ngi 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 thi Cc 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 hnh cc cng trnh phi ph hp vi cc qu trnh XLNT din ra trong . Yu cu v trnh vn hnh cc cng trnh XLNT ph thuc vo loi cng trnh XLNT ti ch hay l XLNT tp trung. a. Qun l vn hnh cc cng trnh XLNT ti ch. Cc cng trnh XLNT ti ch nh b t hoi, ging thm, bi lc ngm, b thu du m... c xy dng trong khun vin cc ngi nh, cc cng trnh dch v cng cng. Cc cng trnh XLNT loi 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 t 6 thng n 1 nm. Khi ly bn phi li khong 20% bn ln men lm mi cho qu trnh phn hu chu k sau. Khi ht bn, u ng ht my bm phi cho xung tn y b. Vng cn trong b phi c ph v vt thng xuyn chng tc ng dn nc thi. Trn np b t hoi khng c trng cy hoc xy dng cc cng trnh khc. Nu mi kh chu do qu trnh ln men axit trong b bc ln th phi 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, ct v cn. Ging thm c bo dng chu o bng cch m np ra theo di thng xuyn. Nu kh nng thm b hn ch th phi xc lp ct pha trn ra sch. Khi thm nc khng m bo 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 thu du m. Sau mi ln ng b 4 gi, cn ra b bng nc sch. Lng nc ra b thng thng bng 15% dung tch hu ch ca b. M phi c vt ra khi b v ch 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 trnh lng 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 ca mng. 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 trong ngn 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 tro cao. Nu c bn ni ln trong vng lng hoc c bt kh trong vng mt thong ca b th iu chng t qu trnh ln men khng n nh v phi thc hin mt trong cc bin php sau y:

- 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.


PGS.TS Trn c H

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 nc cp 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 ra sch, 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 nh pH, 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 hot tnh t 300 n 600 ml/l th b hot ng tt. Hm lng xy ho tan trong b aeroten phi thng xuyn c m bo t 2 n 4mg/l. cc qu trnh sinh ho trong aeroten din ra n nh, cc my bm bn v my sc kh phi lm vic t cng 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 cht lng 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 rc v kh lng. Trong bn xut hin nhiu vi sinh vt hnh si. Khi xy khng hoc c cht c hi trong nc thi, hin tng ny cng thng xy ra. Mt s bin php 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 nc thi mi vo b. Trng hp bn hot tnh trong b aeroten b ni c th do ti lng hu c qu

thp dn n qu trnh nitrat ho xy ra. Trong b lng t hai li din ra qu trnh kh nitrat, km theo vic ni bt kh nit. Mt bn gim xung n mc bn c th ni ln mt nc v trn ra khi b lng t hai. khc phc hin tng bn ni, 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 rt nghim ngt. V vy cc cng trnh ny i hi phi c cng nhn trnh cao theo di, 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 ra khi 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 nh my khuy, gung quay, my bm, 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 c quan 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 hot tnh, nng th tch bn hot tnh, hm lng nitrat, nit amn, photphat, fecal coliform ... trong nc thi dng vo, dng ra v ngay ti cc cng trnh XLNT.


PGS.TS Trn c H

37

Cng nhn vn hnh cc cng trnh XLNT phi c hng dn v quy trnh vn hnh cc cng trnh, cc nguyn tc v an ton lao ng v phng chy, cha chy, cc bin php phng nga v khc phc s c ... Cc cn b k thut ca trm c 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 XLNT quy m va v nh khng phc tp v khng i hi trnh cao nh i vi cc trm XLNT cng sut ln. Tuy nhin chi ph u t xy dng v chi ph qun l vn hnh cc trm nh xt trn tng th th th c th cao hn cc chi ph ca trm XLNT cng sut ln. Mt khc, i vi h thng thot nc phn tn, mi trm XLNT c mt cng ngh ring nn vic qun l v vn hnh khng c thng nht, kim sot cht lng nc cng gp kh khn. Tuy nhin trong iu kin Vit nam v cc nc ang pht trin khc, h thng x l nc thi phn tn v x l nc thi ti ch ph hp vi kh nng u t theo tng giai on cng nh iu kin 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 nc phc v. Song cng rt kh dn ra c cc gi tr tng qut do cc khon chi ph lun thay i do gi c bin ng, mc thu khng n nh v iu kin mi a phng, mi khu vc mt khc. Chi ph u t cng ph thuc vo cng sut h thng thot nc v cng ngh trin khai. Mi quan h gia mc XLNT yu cu v chi ph x l tnh cho mt m3 nc thi c biu din trn hnh .21 sau y.

Chi ph C 4 X l trit Kh BOD,N v P 3 2 X l bc hai X l bc hai 1 bng bn hot tnh X l bc 1 30 70 100 E ,% BOD c kh

Hnh .21. Biu quan h gia chi ph v hiu qu XLNT.


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38

Chi ph u t c lp theo nguyn tc lp h s d ton xy dng c bn c tnh n tt c cc yu t nh din tch t xy dng, chun b mt bng, san nn v h 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. Chi ph 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 xy dng gim nhng chi ph cho kt cu cng trnh li tng ln rt nhiu. Kt hp cc ao h, ng rung , bi t c sn XLNT th gi thnh xy dng trm s gim i rt nhiu. Trong iu kin cho php , sau khi qua b t hoi, nu nc thi x l ti ch trong ao h sinh vt, bi lc ngm, ging thm ... th chi ph u t xy dng s gim i rt nhiu.Gi thnh x l nc thi bao gm chi ph khu hao v chi ph qun l. Chi ph khu hao l c nh . Ngi ta thng ly chi ph khu hao trung bnh l 2,5% cho cc cng trnh thot nc v x l nc thi. i vi cng trnh trn mt t chi ph khu hao ly l 1,25% v cng trnh di mt t l 5% chi ph u t. i vi cc cng trnh XLNT hp khi gi thnh x l c th phn b nh sau / 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 ph xy dng v chi ph qun l tnh cho mt ngi dn hoc cho mt mt khi nc thi x l cng tng. Chi ph vn hnh, qun l cc cng trnh XLNT l yu t cn phi tnh n khi la chn dy chuyn cng ngh XLNT. Cc biu thc xc nh gi 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 nc trong 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 x l < 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 x l < 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 x l >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 x l < 90% khi BOD5 ca nc thi ban u t 250 n 500 mg/l : C=46,8.Q-0,37 , cent/m3 ( .13)


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39

-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 vn hnh cng trnh, chi ph gim st, chi ph hnh chnh, bo him x hi, cng tc phng th nghim ..., theo T chc Bo v mi trng M EPA/ 28 / , xc nh nh sau:

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 trnh

thot 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 hn phc v T

Cng thot nc t chy 4.512Q0,568 97Q0,301 50 Trm bm chuyn bc 0,00004Q2+34Q+316.261 0,80Q+18.526 15 X 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 ct v 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 40 B aeroten c ngn kh nit 90Q+612.777 93Q0,834 40 B lng t hai sau aeroten 2941Q0,609 3,32Q+5.842 40 B lc sinh hc cao ti -0,00007Q2+56,89Q

+244,791 278Q0,505 50

B lng t hai sau b lc sinh hc cao ti (k c bm tun 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 40 H thng clorat kh trng 795Q0,958 -0,000001Q2 +

2,36Q+24.813 15

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

-0,000003Q2

+5,2Q+5733 10


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40

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

+0,18Q+4136 50

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+8003 20

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

+1,97Q+57.349 50

Ghi ch : Q- lu lng nc thi trung bnh trong ngy, m3/ngy; C- gi thnh xy dng (xy lp v thit b ) ca cng trnh, la M; M- chi ph qun l v vn hnh cng trnh, 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 mi

trng.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-Tiu

chun 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. Trng 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 bnh

vin. 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 CII 2.04.03-85CII 2.04.03-85 ). Matscva,1986 (ting Nga).

14. Karelin Ia.A. Jucp D.D. Jucp V.N.Repin B.N. X l nc thi cng nghip trong aeroten.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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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 . Eckenfelder

Inc., 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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Ph lc 1. TCVN 6772:2000-Cht lng nc -Nc thi sinh hot -Gii hn

nhim cho php Water Quality - Domestic Wastewater Standards 1.Phm vi p dng: Tiu chun p dng i vi nc thi sinh hot cc loi c s dch v, c s cng cng v chung c khi x vo cc vng nc quy nh nhng ni cha c HTTN v XLNT tp trung. 2.Gii hn nhim cho php:

Bng 1. Thng s nhim v gii hn cho php

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

1 pH 5-9 5-9 5-9 5-9 5-9 2 BOD5, mg/l 30 30 40 50 200 3 Cht rn l lng, mg/l 50 50 60 100 100 4 Cht rn c th lng, mg/l 0,5 0,5 0,5 0,5 KQ 5 Tng cht rn ho tan, mg/l 500 500 500 500 KQ 6 Sun phua(theo H2S), mg/l 1,0 1,0 3,0 4,0 KQ 7 Nitrt (NO3

-), mg/l 30 30 40 50 KQ 8 Du m (thc phm), mg/l 20 20 20 20 100 9 Phosphat (PO4

3-), mg/l 6 6 10 10 KQ 10 Coliform, MPN/100ml 1.000 1.000 5.000 5.000 10.000

Ghi 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 sau.

Bng 2. Cc mc p dng i vi cc c s dch v , cng cng v khu chung c.

Loi hnh Quy m Mc p dng theo bng 1

Ghi ch

1.Khch sn Di 60 phng Mc III T 60 n 200 phng Mc II Trn 200 phng Mc I

2.Nh tr, nh khch T 10 n 50 phng Mc IV T 50 n 250 phng Mc III Trn 250 phng Mc II

3.Bnh vin nh, trm x T 10 n 30 ging Mc II Phi kh trng nc thi Trn 30 ging Mc I

4.Bnh vin a khoa Mc I 5.Tr s cc c quan hnh chnh, vn phng i din...

T 5.000 n 10.000m2 Mc III Din tch tnh l khu vc lm vic T 10.000 n 50.000m2 Mc II

Trn 50.000 m2 Mc I 6.Trng hc, vin nghin cu v cc c s tng t

T 5.000 n 25.000m2 Mc II Trn 25.000 m2 Mc I

7.Ca hng bch ho, siu T 5.000 n 25.000 m2 Mc II


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th Trn 25.000 m2 Mc I 8.Ch thc phm ti sng T 500 n 1.000 m2 Mc IV

T 1.000 n 1.500 m2 Mc III T 1.500 n 25.000 m2 Mc II Trn 25.000 m2 Mc I

9.Nh hng n ung, nh n cng cng, ca hng thc phm

Di 100 m2 Mc V T 100 n 250 m2 Mc IV T 250 n 500 m2 Mc III T 500 n 2.500 m2 Mc II Trn 2.500 m2 Mc I

10.Khu chung c Di 100 cn h Mc III T 100 n 500 cn h Mc II Trn 500 cn h Mc I

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


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44

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 cc cht nhim ch yu c trong nc thi th khi x vo ngun nc mt phc v lm ngun cung cp cho trm x l nc nc n ung v sinh hot ( ngun loi A ) v vo HTTN 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 hn Loi A Loi B 1 Nhit oC 40 40 2 pH 6-9 5-9 3 mu Pt/Co 20 50 4 c NTU 50 100 5 Tng cht rn l lng (SS) mg/l 50 100 6 Tng cht rn ho tan mg/l 1.000 3.000 7 COD mg/l 50 100 8 BOD5 mg/l 20 50 9 Clorua (Cl-) mg/l 250 1.000 10 Sunpht ( SO4

2-) mg/l 200 1.000 11 Nitrit ( NO2

-) mg/l 0,1 2,0 12 Nitrat (NO3

-) mg/l 50 - 13 Du m khong mg/l 0,001 1,0 14 Clo d mg/l 1,0 2,0 15 Coliform MPN/100ml 5.000 10.000 Ghi ch: Nng gii hn ca cc ch tiu nhim khc khng nu trong bng ny c th xc nh theo TCVN 5945-1995.


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

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

TT Thng s TCVN 5942-1995 TCVN

5943-1995TCVN

6774:2000 TCVN

6773:2000 Loi A Loi B 1 pH 6-8,5 5,5-9 6,5-8,5 6,5-8,5 5,5-8,5 2 BOD5, mg/l 4 25 20 10 3 COD, mg/l 10 35 4 xy ho tan, mg/l 6 2 4 5 2 5 Cht rn l lng (SS),

mg/l 20 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 khng 10 Cht ty ra, mg/l 0,5 0,5 11 St, mg/l 1 2 0,1 12 Xianua, mg/l 0,01 0,05 0,01 0,005 13 Asen, mg/l 0,05 0,1 0,05 0,02 0,05-0,1 14 Phenol tng s, mg/l 0,001 0,02 0,001 15 Tng ho cht bo v

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

16 Tng cht rn ho tan, mg/l

1.000 Theo ch s SAR

17 Coliform, MPN/100 ml 5.000 10.000 1.000 200 cho vng trng 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 mc ch 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 ngt bo v i sng thu sinh; TCVN 6773:2000-Cht lng nc- Cht lng nc dng cho thu li.


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