tcxdvn 51 2008

TCXDVN-51:2008

B XY DNG

TCXDVN 51 : 2008THOT NC - MNG LI V CNG TRNH BN NGOI TIU CHUN THIT KDrainage and sewerage - External Networks and Facilities Design Standard

D THO BO CO CUI CNG(Cc bn c th s dng bn ny tham kho trong khi ch bn chnh thc s c pht hnh trong nm 2008)

H NI 1/2008http://www.nuoc.com.vn

1Vui lng ghi r nuoc.com.vn khi pht hnh ti liu ny

TCXDVN-51:2008

THOT NC - MNG LI V CNG TRNH BN NGOI TIU CHUN THIT K

1..

PHM VI P DNG

1.1. Tiu chuNn ny c p dng thit k xy dng mi hoc ci to, m rng v nng cp cc h thng thot nc (mng li thot nc v cng trnh bn ngoi) ca cc th, khu dn c tp trung v khu cng nghip. Ghi ch:Khi thit k cc h thng thot nc cn phi tun theo cc quy chun v tiu chun lin quan khc c Nh nc ban hnh. 2.

QUI NNH CHUNG

2.1

Khi thit k h thng thot nc phi xem xt cc gii php c bn ca s thot nc c la chn ph hp vi thit k qui hoch ca cc th, khu dn c tp trung v khu cng nghip,... Cc phng n thit k phi ch ti kh nng tn dng nc thi c x l ti s dng trong sn xut cng nghip, nng nghip, lm nghip v nui trng thy sn.

2.2

Khi la chn h thng v s thot nc phi nh gi kinh t, k thut, mc m bo v sinh ca cc cng trnh thot nc hin c v kh nng tip tc s dng chng. Khi thit k thot nc cho cc im dn c, cho php s dng cc kiu h thng thot nc: chung, ring mt na, ring hon ton hoc h thng hn hp tu theo a hnh, iu kin kh hu, yu cu v sinh ca cng trnh thot nc hin c, trn c s so snh cc ch tiu kinh t k thut. i vi h thng thot nc ma, nu iu kin cho php c th s dng h thng mng mng h v phi ch x l phn nc ma b nhim bNn. H thng thot nc ca cc x nghip cng nghip thng thit k theo kiu ring hon ton, nhng trong cc trng hp c th c th kt hp thu gom ton b hoc mt phn nc thi sn xut vi nc thi sinh hot. Khi thit k thot nc cho cc c s cng nghip cn xem xt: - Kh nng thu hi cc cht qu c trong nc thi sn xut. - Kh nng gim lng nc thi sn xut x ra mi trng bn ngoi bng cch p dng qu trnh cng ngh hp l, s dng h thng cp nc tun hon ton b, mt phn hoc ly nc thi ca phn xng ny s dng cho phn xng khc.Ghi ch: Ch cho php s dng nc thi sinh hot c x l v kh trng cp nc cho sn xut.

2.3

2.4 2.5

2.6

2.7

Nc s dng qua qu trnh sn xut nu khng b nhim bN cn nghin n cu s dng li. Khi khng th s dng li th cho php x vo ngun tip nhn hoc vo h thng thot nc ma.

http://www.nuoc.com.vn


TCXDVN-51:2008

2.8

Vic x nc thi sn xut vo h thng thot nc v cng trnh x l nc thi th cn phi cn c vo thnh phn cc cht nhim c trong nc thi sn xut, ch tiu kinh t k thut ca h thng thot nc v yu cu v sinh khi x nc thi vo ngun tip nhn. Trong trng hp ny, nc thi sn xut phi m bo cc yu cu sau: - Khng nh hng xu ti s hot ng ca ng cng thot nc v cng trnh x l nc thi. - C nng cht l lng v cht ni khng qu 500 mg/l. - Khng cha cc cht c kh nng ph hy vt liu, dnh bm ln thnh ng hoc lm tc cng thot nc v cc cng trnh khc ca h thng thot nc. - Khng cha cc cht d chy (du, xng ) v cc cht kh ho tan c th to thnh hn hp n trong ng ng hoc cng trnh thot nc. - Khng cha cc cht c c nng nh hng xu ti qu trnh x l sinh hc hoc ti vic x nc thi vo ngun tip nhn.Ghi ch: Nu nc thi sn xut khng m bo cc yu cu ni trn phi x l s b ti ch. Mc x l s b cn phi c chp nhn ca c quan qun l mi trng v n v thot nc a phng.

2.9

Khi ni ng cng thot nc thi ca cc c s sn xut vo mng li ca th th tng c s phi c cng x v ging kim tra ring, t ngoi phm vi c s.Ghi ch: Cho php t cng dn chung nc thi sn xut cc nh my, x nghip sau ging kim tra ca tng c s.

2.10

Nc thi c cha cc cht c hi v vi trng gy dch bnh trc khi x vo mng li thot nc ca th hoc khu dn c phi c kh c v kh trng. Khng cho php x nhiu loi nc thi vo cng mt mng li thot nc, nu nh vic trn cc loi nc thi vi nhau c th to thnh cc cht c, kh n hoc cc cht khng tan vi s lng ln. Khng c x nc thi sn xut c nng cht nhim cao tp trung thnh tng t. Trng hp khi lng v thnh phn nc thi thay i qu ln trong ngy cn phi thit k b iu ho. Ngoi vic tun th cc qui nh nu trong tiu chuN ny, s cng ngh v n phng php x l, cc thng s tnh ton cng trnh x l v bn cn nc thi sn xut cn cn phi da theo cc quy nh, cc tiu chuN thit k xy n dng cc x nghip cng nghip tng ng, cc ti liu ca c quan nghin cu khoa hc v kinh nghim qun l cc cng trnh tng t. 2.14 Mc x l nc thi trc khi x vo ngun tip nhn c xc nh bng tnh ton trn c s m bo cc iu kin v sinh theo quy nh ca cc tiu chuN mi trng Vit Nam v c c quan qun l mi trng chp n thun. Cc cng trnh x l nc thi ca c s cng nghip nn b tr trong phm vi t ai ca c s .

2.11

2.12

2.13

2.15



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2.16

Khong cch v sinh t cc cng trnh x l v trm bm nc thi ti ranh gii xy dng nh cng cng v cc x nghip thc phN (c xt ti kh m nng pht trin ca cc i tng ) c qui nh nh sau: - i vi cc cng trnh x l v trm bm nc thi sinh hot ly theo bng 1-1 - i vi cc cng trnh x l v trm bm nc thi sn xut khng nm trong a gii ca x nghip, nu c bm v x l hoc kt hp bm v x l cng vi nc thi sinh hot th ly theo tiu chuN v sinh qui nh khi thit n k cc cng trnh v sinh theo cc tiu chuN thit k cc x nghip cng n nghip do Nh nc hay cc B ch qun ban hnh, nhng khng thp hn cc qui nh trong bng 2-1.Khong cch ly v sinh tnh bng m, theo cng sut tnh ton ca cng trnh, nghn m3/ngy Di 0,2 T 0,2 n 5 T 5 n 50 >50 150 100 200 150 200 150 15 200 150 300 200 200 200 20 400 300 400 300 400 20 500 400 30

Bng 2-1.Tn cng trnh 1. Cng trnh x l c hc v sinh hc c sn phi bn 2. Cng trnh x l c hc v sinh hc c x l bn cn bng thit b c kh.. 3. Bi lc ngm 4. Cnh ng ti 5. H sinh hc 6. Mng xy ha tun hon 7. Trm bm

Ghi ch: 1. Khi khng m bo c khong cch ti thiu trn, th phi c cc gii php cng ngh ph hp m bo c iu kin v sinh v phi c cc cquan qun l mi trng a phng chp thun . 3. Nu trong a gii ca trm x l nc thi c hc v sinh hc cng sut di 50m3/ngy c bi lc ngm din tch di 0,5 ha th khong cch trn ly bng 100m 4. Khong cch ly v sinh trong bi lc ngm cng sut di 15 m3/ngy ly 15 m 5. Khong cch ly v sinh ca b t hoi 5m, ging thm 8m. 6. Khong cch ly trong bng 1-1 cho php tng ln nhng khng qu 2 ln nu khu dn c xy dng cui hng gi ch o so vi trm x l, cho php gim i nhng khng qu 25% nu khu dn c xy dng v tr c hng gi thun li theo quan im v sinh. 7. Nu lm kh bn cn cha c n nh bng sn phi bn th khong cch v sinh phi c tnh ton ph hp vi cc tiu chun mi trng v c c quan qun l mi trng a phng chp thun. 8. i vi cc cng trnh ci to, ty tng trng hp ngoi l c th p dng khc vi qui nh trong bng ny nhng phi c s chp thun ca c quan qun l mi trng a phng.

2.17

Khng c x nc ma trong cc trng hp sau: - Trc tip vo cc khu vc dng lm bi tm. - Vo cc khu vc trng khng c kh nng t thot nc v d to thnh m ly.



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- Vo khu vc xi mn, nu thit k khng c bin php gia c b. 2.18 Phi xt ti kh nng a cng trnh vo tng giai on xy dng v trng hp cn thit vn hnh ton b cng trnh cng nh kh nng pht trin trong tng lai khi vt qu cng sut tnh ton ca cng trnh.Ghi ch: Cho cng trnh vo s dng theo tng giai on xy dng hay vn hnh ton b xut pht t iu kin m bo mc lm sch nc thi tho mn yu cu ca nguyn tc v sinh khi x nc thi vo ngun tip nhn.

2.19

Cc gii php k thut c bn c thit k phi da trn c s so snh ch tiu kinh t k thut ca cc phng n xut. Phng n c chn l phng n kinh t v m bo kh nng thc hin mt cch thun li.



TCXDVN-51:2008

3.

TIU CHUN THI NC V TNH TON THU LC MNG LI THOT NC

Tiu chun thi nc v h s khng iu ho 3.1 Tiu chuN thi nc th bao gm nc thi sinh hot v dch v xc nh n theo tiu chuN cp nc tng ng vi tng i tng v tng giai on xy n dng. H s khng iu ho ngy ca nc thi th hoc khu dn c Kng ly bng 1,15 -1,3 tu theo c im ca tng th. H s khng iu ho chung ly theo bng 3-1, ph thuc lu lng nc thi trung bnh ngy qtb . Bng 3-1.H s khng iu ho chung K0 K0 max K0 min 5 2,5 0.38 Lu lng nc thi trung bnh qtb (l/s) 10 20 50 100 300 500 1000 2,1 1,9 1,7 1,6 1,55 1,5 1,47 0.45 0.5 0.55 0.59 0.62 0.66 0.69 5000 1,44 0.71

3. 2

Ghi ch: 1. Khi lu lng trung bnh nm gia cc s trong bng 3-1 th h s khng iu ho chung xc nh bng cch ni suy 2. H s khng iu ho K0 ly theo bng 3-1 cho php p dng khi lng nc thi sn xut khng vt qu 45% tng lu lng nc thi th. 3. Khi lu lng trung bnh ca nc thi nh hn 5 l/s th K0 ly bng 5.

3. 3

S phn b lu lng nc thi ca th v khu dn c theo cc gi trong ngy xc nh theo biu dng nc. Nu khng c biu dng nc th s phn b ny c th cn c theo ti liu qun l ca i tng thot nc tng t . Tiu chuN v h s khng iu ho nc thi sinh hot t cc x nghip cng n nghip, t cc nh hoc cng trnh cng cng ring r th xc nh theo tiu chuN thot nc bn trong nh. n Tiu chuN v h s khng iu ho nc thi sn xut t cc c s cng n nghip phi xc nh theo ti liu cng ngh sn xut . Lu lng tnh ton ca nc thi sn xut t cc c s cng nghip c xc nh nh sau: - ng ng thot nc t cc phn xng xc nh theo lu lng gi ln nht; - ng ng dn chung ca ton nh my theo th x nc tng gi; - ng ng dn chung ca mt nhm nh my theo th thi nc tng gi c xt ti thi gian chy ca nc thi trong ng ng. Tnh ton lu lng v iu ho dng chy nc ma

3. 4

3. 5 3. 6

3.7

Lu lng tnh ton thot nc ma ca tuyn cng (l/s) c xc nh theo phng php cng gii hn v tnh theo cng thc: Q= q.C.F (3-1) q - Cng ma tnh ton (l/s.ha ) C - H s dng chy F - Din tch lu vc m tuyn cng phc v (ha)



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H s dng chy C ph thuc vo loi mt ph v chu k lp li trn ma tnh ton P, xc nh theo bng 3-4. 3.8 Cng ma xc nh nh sau: q= A(1+ClgP)/(t+b)n Trong : q- Cng ma (l/s.ha) t - Thi gian dng chy ma (pht) P- Chu k lp li trn ma tnh ton (nm) A,C,b,n- Tham s xc nh theo iu kin ma ca a phng, c th chn theo ph lc II; i vi vng khng c th tham kho vng ln cn. S liu ma cn c chui thi gian lu tr t 20 n 25 nm bng my o ma t ghi, thi gian ma ti a l 150 180 pht. i vi lu vc c din tch ln hn 300 ha cn phi tnh thm h s ma ro, theo ph lc II. Chu k lp li trn ma tnh ton P i vi cng thot nc cp I ph thuc vo iu kin thot nc lu vc v xc nh theo bng 3-2. Bng 3-2. .Tnh cht th - Thnh ph ln, loi I - th loi II, III - Cc th khc iu kin thot nc Thun li Trung bnh 10 5 2 5 2 1 Bt li 2-1 1- 0,5 0,5-0,33

(3-2)

Ghi ch: i vi cc th hay khu vc th a hnh i ni, khi din tch lu vc thot nc ln hn 150 ha, dc a hnh ln hn 0,02 nu tuyn cng chnh nm vt trng ca lu vc th khng phn bit quy m th, gi tr P cn ly ln hn quy nh trong bng, c th chn P bng 10 - 20 nm da trn s phn tch ri ro tng hp v mc an ton ca cng trnh.

i vi cc khu cng nghip tp trung, chu k lp li trn ma tnh ton P ph thuc vo tnh cht khu cng nghip v c xc nh theo bng 3-3. Bng 3-3.Tnh cht khu cng nghip Cng ngh bnh thng Cng ngh c bit Gi tr P 5 - 10 10 -20

Khi thit k tuyn thot nc nhng ni c cc cng trnh quan trng (nh tuyn tu in ngm, nh ga xe la, hm qua ng,) hoc trn nhng tuyn ng giao thng quan trng m vic ngp nc c th gy ra nhng hu qu nghim trng th chu k P ly ln hn so vi quy nh trong bng 3-2, c th gi tr P ly bng 25 nm. i vi khu vc c a hnh bt li c th ly cao hn (50 hoc 100 nm) da trn s phn tch tng hp ri ro v yu cu an ton.



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3.9

i vi thnh ph ln c nhiu trm o ma cn phn tch tng quan ca lng ma ca cc trm xc nh h s phn b ma theo im v din tch. Trong trng hp ch c mt trm o ma th lu lng tnh ton cn nhn vi h s phn b ma ro n. Nu khng c ti liu nghin cu trong nc th c th s dng biu c thnh lp ca c quan, t chc kh tng th gii nm 1983. H s dng chy C xc nh bng m hnh tnh ton qu trnh thm. Trong trng hp khng c iu kin xc nh theo m hnh ton th i lng C, ph thuc tnh cht mt ph ca lu vc v chu k lp li trn ma tnh ton P, c chn theo bng 3-4. Bng 3-4.Tnh cht b mt thot nc Mt ng atphan Mi nh, mt ph btng Mt c, vn, cng vin (c chim di 50%) - dc nh 1-2% - dc trung bnh 2-7% - dc ln Chu k lp li trn ma tnh ton P (nm) 2 5 10 25 50 0,73 0,77 0,81 0,86 0,90 0,75 0,80 0,81 0,88 0,92 0,32 0,37 0,40 0,34 0,40 0,43 0,37 0,43 0,45 0,40 0,46 0,49 0,44 0,49 0,52

3.10

Ghi ch: Khi din tch b mt c nhiu loi mt ph khc nhau th h s C trung bnh xc nh bng phng php bnh qun theo din tch.

3.11

Thi gian dng chy ma n im tnh ton t (pht), c xc nh theo cng thc: Trong : t = to + t1 + t2 (3-3)

to -Thi gian nc ma chy trn b mt n rnh ng, c th chn t 5 n 10 pht. Nu trong gii hn tiu khu c t ging thu nc ma th l thi gian chy n cng ca ng ph (thi gian tp trung b mt) xc nh theo quy nh iu 3.14. Ring i vi khu vc m tnh cht th cha r rt th xc nh theo quy nh iu 3.16. t1-Thi gian nc chy theo rnh ng n ging thu (khi trong gii hn tiu khu khng t ging thu nc ma) xc nh theo ch dn iu 3.12. t2- Thi gian nc chy trong cng n tit din tnh ton xc nh theo ch dn iu 3.13. 3.12 Thi gian nc ma chy theo rnh ng t1 (pht) xc nh theo cng thc:t1 = 0,021 L1 V1

(3-4)

Trong : L1 - Chiu di rnh ng (m) V1 - Tc chy cui rnh ng (m/s) 3.13 Thi gian nc ma chy trong cng n tit din tnh ton xc nh theo cng thc:



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t 2 = 0,017

L2 V2

(3-5)

Trong : L2 - Chiu di mi on cng tnh ton (m) V2 - tc chy trong mi on cng tng ng (m/s) 3.14 i vi khu vc th m h thng thot nc ma cha r rt (khng b tr ging thu, khng c rnh ng) th thi gian tp trung nc ma b mt (t0 + t1) c xc nh theo cng thc sau:1,5n 0,6 L0, 6 t = t0 + t1 = 0,3 0,5 0,3 Z i I

(pht)

(3-6)

Trong :

n H s nhm Maning L - Chiu di dng chy (m) Z H s mt ph, ly theo bng 3-5 I Cng ma (mm/pht) i - dc b mt

Bng 3-5Loi mt ph - Mi nh mt ng nha - Mt ng lt - Mt ng cp phi - Mt ng ghp - Mt ng t - Cng vin, t trng cy ( st) - Cng vin, t cy xanh ( st) - Bi c H s Z 0,24 0,224 0,145 0,125 0,084 0,038 0,020 0,015

Ghi ch: Khi din tch b mt c nhiu loi mt ph khc nhau th h s Z trung bnh xc nh bng phng php bnh qun theo din tch.

3.15 3.16

Din tch thu nc tnh ton cho mi on cng c th ly bng ton b hay mt phn din tch thu nc sao cho lu lng tnh ton l lu lng ln nht. Vn cy v cng vin khng c mng li thot nc ma th khng xt n din tch lu vc v h s dng chy. Nhng nu mt t c dc nghing v pha ng ph ln hn hoc bng 0,008 th di t dc theo ng c b rng 50 - 100 m phi c tnh vo lu vc thot nc. iu ho dng chy nc ma, bao gm c vic lm chm dng chy bng bin php thm v cha, nhm mc ch gim lu lng nh, lu lng ca h thng thot nc, gim tc ng tiu cc do nc ma gy ra, gi n nh nc ngm v to cnh quan mi trng. Cc cng trnh thm bao gm: cng trnh thm t nhin v cng trnh nhn to. Cc cng trnh cha bao gm: b cha, h cha, h iu ho v cc khu t trng trong cc vn cy, bi c, c th cha tm thi trong khi ma. Khi thit k h iu ho cn bo m cc yu cu:

3.17

3.18



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Ca dn nc vo h v x nc ra khi h phi b tr hp l thun tin trong vic khng ch v iu khin mc nc trong h, ph hp vi din bin cn ma v bo m cnh quan h th. Khi vn hnh h iu ha, cn tnh n vic thay nc h m bo cc iu kin v sinh (trung bnh mi nm 2 ln thay nc) su lp nc tnh t mc nc ti thiu n y h khng nh hn 1m. 3.19 Xc nh th tch iu ho ca h W (m3) bng biu lu lng nc ma chy vo v x ra khi h theo mc nc trung bnh v mc nc ln nht. i vi nhng cng trnh nh, khng yu cu chnh xc cao, khi p dng phng php cng gii hn c th tnh ton th tch iu ha cng thc sau: W = K. Qn.tn (3-7) Trong : Qn - Lu lng tnh ton nc ma chy ti h ( m3/s). tn - Thi gian ma tnh ton ca ton b cc lu vc thuc tuyn cng ti ming x vo h (cn c theo bng tnh thu lc mng li thot nc ma) K - H s, ph thuc i lng , ly theo bng 3-6. Bng 3-6. K K K 0,1 0,5 0,4 0,42 0,15 1,1 0,45 0,36 0,7 0,13 0,20 0,85 0,5 0,3 0,75 0,1 0,25 0,69 0,55 0,25 0,8 0,07 0,30 0,58 0,6 0,21 0,85 0,04 0,35 0,5 0,65 0,16 0,9 0,02 Ghi ch: l t l gia lu lng nc ma c iu tit chy vo tuyn cng sau h Qx vlu lng nc ma tnh ton chy vo h Qn: =Qx . Qn

Tnh ton thu lc mng li thot nc thi 3.20 Khi tnh ton thu lc mng li thot nc t chy hoc c p, lu lng tnh ton l lu lng nc thi ln nht. tnh ton thu lc cng c th s dng cng thc Maning. Q = 1/n x A x R2/3 x I1/2 Trong : Q Lu lng tnh ton (m3/s) I - dc thu lc R- Bn knh thu lc (m) A Tit din cng (m2) n H s nhm Manning H s nhm n ly theo bng 3-7http://www.nuoc.com.vn

(3-8)


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Bng 3-7.Loi cng v mng Cng: - B tng ct thp - ng gang - ng thp - ng nha Mng: - Mi c - Mi xy - Mi b tng - Mi b tng v y b tng H s nhm Manning (n) 0,013 0,012 0,012 0,011 0,03 0,025 0,022 0,015

3.21

Khi tnh ton thu lc ng ng dn bn cn c p lc (dn cn ti, cn ln men, bn hot tnh) phi xt n ch chuyn ng, tnh cht l hc v c im bn cn. Tnh ton thu lc mng li thot nc chung, na ring v tnh ton ming x hn hp nc ma v nc thi vo ngun tip nhn

3.22

Mng li thot nc chung phi m bo tiu thot c lng nc ma trong thi gian ma c cng tnh ton. Cc on cng c tng lu lng nc thi sinh hot v nc thi sn sut trn 10 l/s phi kim tra iu kin thy lc trong ma kh. Tc dng chy nh nht ph thuc y ca cng hoc mng, ly theo bng 3-8. Bng 3-8. y tng ng vi lu lng ma kh (cm)10 - 20 21 - 30 31 - 40 41 - 60 61 - 100 100 - 150 > 150

Tc nh nht ca nc thi (m/s)0,75 0,8 1,0 1,1 1,2 1,3 1,5

Ghi ch: Nu cc ngi nh c b t hoi th tc nh nht cho php gim 30%.

3.23

Lu lng tnh ton ca on cng chung trc ming x th nht xc nh bi tng lu lng trong ma kh Qkh (nc thi sinh hot v nc thi sn xut) v lu lng nc ma. Lu lng tnh ton Qn ca on ng pha sau ming x xc nh theo cng thc sau: Qn = Qkh + n0.Qkh + Qm (3-9) Trong :



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Qkh - Tng lu lng trung bnh ca nc thi ca on cng tnh ton. Qkh - Tng lu lng nc thi ca cc lu vc pha trc ming x. n0 H s pha long, xc nh theo iu 3.25, Qm - Lu lng nc ma ca cc lu vc trc tip ca cc on cng pha sau ming x. 3.24 3.25 Khi kim tra iu kin thu lc mng li thot nc chung trong ma kh th lu lng nc thi sinh hot v sn xut xc nh tng t nh i vi mng li thot nc ring hon ton. B tr ming x hn hp nc ma v nc thi v xc nh h s pha long n0 phi cn c theo iu kin v sinh, ch thu vn, kh nng t lm sch v tnh cht s dng ca ngun tip nhn. H s pha long n0 thng chn t 1 n 3, ph thuc vo v tr cng x trn mng li thot nc. i vi cc ming x u lu vc thot nc, n0 chn bng 3; i vi cc ming x cui lu vc n0 chn bng 1. Khi la chn ngun tip nhn b tr ming x hn hp nc ma v nc thi, ngoi vic tun theo cc quy nh theo iu 2.17 cn phi tho mn cc yu cu sau: - Sng (bao gm c cc sng o ln) phi c dng chy lin tc, c bit vo ma kh, vn tc ti thiu khng di 0,3m/s. Lu lng dng sng tham gia pha long (aQ) khng nh hn 5 ln so vi lu lng nc thi. - H t nhin hay nhn to phi c dung tch v chiu su ln, c dng chy lin tc v kh nng thay nc h trung bnh 4 - 5 ln trong mt nm.Ghi ch: Hin nay trong nhiu d n thot nc th b tr cc ming x nc thi vo cc ao h nh, nng nm trong thnh ph li khng c iu kin thay nc, c coi l gii php tm thi, khi c ci to bng h thng cng ring ti cc im x ny phi b tr ging tch nc thi.

3.26 3.27

Lu lng hn hp nc ma v nc thi dn n trm x l v ma ma c th s b ly bng 2 - 2,5 ln lu lng trung bnh ca nc thi v ma kh. Lu lng tnh ton hn hp nc thi qmix (l/s) ca tuyn cng chung trong h thng thot nc ring mt na xc nh theo cng thc: qmix = qcit + qlim (3-10) Trong : qcit Lu lng tnh ton ca nc thi sinh hot v sn xut c tnh n h s khng iu ho (l/s). qlim lu lng nc ma b nhim bN cn c x l, bng tng lu lng n gii hn ca nc ma qlim a vo trong tuyn cng chung t mi ging tch nc n on cng tnh ton (l/s).

3.28

Lu lng nc ma b nhim bN cn x l qlim (l/s) xc nh theo quy nh n ti mc 3.2 ca tiu chuN ny vi chu k lp li trn ma tnh ton P = 0,5-1,0 n nm, iu m bo lng nc ma a x l khng di 70% tng lng nc ma b nhim bN n.



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3.29

Cc tuyn cng thot nc thi v nc ma trong h thng thot nc na ring tnh ton theo tiu chuN ca cc mng li tng ng trong h thng n ring hon ton.

ng knh nh nht ca cng v y tnh ton trong cng v mng 3.30 ng knh nh nht ca cng thot nc qui nh nh sau: Bng 3-9.Loi h thng thot nc- H thng thot nc sinh hot - H thng thot nc ma - H thng thot nc chung

ng knh nh nht D (mm) Trong tiu khu ng ph 150 200 200 400 300 400

- ng ni t ging thu nc ma n ng cng c ng knh D=200mm 300mm.Ghi ch : 1. Cc khu dn c c lu lng nc thi di 500 m3/ngy cho php dng ng D200 mm t ng ph; 2. Trong cc trng hp c bit, ng thot nc thi sn xut cho php c ng knh di 200 mm; 3. Trong iu kin k thut sn xut cho php, cc ng cng nh nht trong h thng thot nc sinh hot v thot nc chung nn p dng kiu c tit din hnh van.

3.31

y tnh ton ln nht ca ng cng ph thuc vo ng knh cng v ly nh sau: + i vi cng D= 200 - 300 mm, y khng qu 0,6 D + i vi cng D= 350 - 450 mm, y khng qu 0,7 D + i vi cng D=500 - 900 mm, y khng qu 0,75 D + i vi cng D trn 900 mm, y khng qu 0,8 D.Ghi ch : 1- i vi mng c chiu cao H t 0,9m tr ln v tit din ngang c hnh dng bt k y khng c qu 0,8 H; 2 - Cng thot nc ma v cng thot chung c thit k chy y hon ton 3. i vi tuyn cng u tin l tuyn cng khng tnh ton, y ca cng khng quy nh.

3.32

Mng thot nc ma xy dng trong phm vi cc nhm nh , chiu su dng nc khng c vt qu 1m, v b mng phi cao hn mc nc cao nht t 0,2 m tr ln. Vn tc tnh ton ca nc thi

3.33

Vn tc dng chy nc thi nh nht ph thuc vo thnh phn v kch thc ca cc ht l lng trong nc thi, bn knh thu lc hoc y ca cng hay mng. - i vi nc thi sinh hot v nc ma, vn tc chy nh nht Vmin ng vi y tnh ton ln nht ca cng qui nh nh sau: Cng c ng knh 150 200 mm Vmin = 0,7 m/s Cng c ng knh 300 400 mm Vmin = 0,8 m/s



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Cng c ng knh 400 500 mm Cng c ng knh 600 800 mm Cng c ng knh 900 1200 mm Cng c ng knh 1300 1500 mm Cng c ng knh > 1500 mm

Vmin = 0,9 m/s Vmin = 1 m/s Vmin = 1,15 m/s Vmin = 1,2 m/s Vmin = 1,3 m/s

- i vi nc thi sn xut, vn tc dng chy nh nht nn ly theo qui nh ca c quan chuyn ngnh hoc theo cc ti liu nghin cu.Ghi ch: 1. i vi cc loi nc thi sn xut, c tnh cht ging vi nc thi sinh hot th vn tc chy nh nht ly theo nc thi sinh hot; 2. i vi nc ma c chu k lp li trn ma tnh ton P nh hn hay bng 0,5 nm, vn tc nh nht l 0,7 m/s. 3. i vi cc loi cng u mng li khng m bo vn tc nh nht nh qui nh hoc y tnh ton di 0,2 D th nn xy dng cc ging ty ra.

3.34 3.35

Vn tc dng chy nh nht trong cng ca nc thi lng hoc x l sinh hc cho php ly bng 0,4 m/s. Vn tc dng chy ln nht ca nc thi trong cng bng kim loi khng qu 8m/s, trong cng phi kim loi khng qu 4 m/s. i vi nc ma ly tng ng bng 10 v 7 m/s. Vn tc dng chy tnh ton ca nc thi trong ng siphon khng c nh hn 1m/s; tc dng chy ca nc thi trong on cng ni vi ng siphon khng c ln hn tc chy trong ng siphon. Vn tc dng chy nh nht trong ng p lc dn bn (cn ti, cn phn hu, bn hot tnh,..) c nn ly theo bng 3-10. Bng 3-10. N ca m bn % 92 93 94 95 96 97 98 Vn tc chy tnh ton trong ng ng p lc dn bn (m/s) ph thuc vo ng knh ng dn bn D (mm) D =150 - 200 D =250 - 400 1,4 1,5 1,3 1,4 1,2 1,3 1,1 1,2 1,0 1,1 0,9 1,0 0,8 0,9

3.36

3.37

3.38

Vn tc ln nht trong mng dn nc ma v nc thi sn xut c php x vo ngun tip nhn ly theo bng 3-11. Bng 3-11. Tn loi t hay kiu gia c-

Vn tc chy ln nht (m/s) ng vi chiu su dng nc H = 0,4-1m.4 4 3-3,5 0,4 0,8

Gia c bng cc tm b tng vi, sa thch lt c va Ct nh, ct va, pha st Ct th, pha st gy



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-

Pha st St Lp c y mng Lp c thnh mng

1,0 1,2 1,0 1,6

Ghi ch: Khi chiu su dng nc H nm ngoi khong gi tr 0,4 - 1m, vn tc bng trn phi nhn vi h s iu chnh K, + Nu H di 0,4 m h sK= 0,85 + Nu H trn 1 m h s K=1,25.

dc cng, mng v rnh thot nc 3.39 dc nh nht ca cng imin phi chn trn c s m bo vn tc dng chy nh nht qui nh. i vi tt c cc h thng thot nc, dc nh nht ng vi y tnh ton qui nh nh sau: - i vi cng D=150 mm imin = 0,008 D=200 mm imin = 0,005 D=300 mm imin = 0,0033 D=400mm imin = 0,0025Ghi ch: - Trong mt s trng hp c bit, cho php ly dc imin =0,004 i vi ng D=200 mm; 0,007 i vi ng D=150 mm; - dc ng ni t ging thu nc ma n cng thot nc ly bng 0,02.

3.40

dc ca rnh ng, mng thot nc ma ly theo bng 3-12. Bng 3-12. Cc hng mc- Rnh ng mt ph atphan - Rnh ng mt ph bng dm hay tng - Rnh ng ri cui, si

dc nh nht ca rnh ng, mng0,003 0,004 0,005

3.41

Kch thc nh nht ca ca cc loi mng c tit din hnh thang ly nh sau: Chiu rng y ly 0,3m su 0,4m. taluy ly theo bng 3-13. Bng 3-13. Loi t lng mng+ Ct mn + Ct nh, va v th a) Loi ri v c cht trung bnh b) Cht + Pha ct + Pha st v st + t si v t ln cui + t v t chu nc + phong ho +

ta luy1:3 1:2 1:15 1:1,5 1:1,25 1:1,125 1:0,5 1:0,25 1:0,1



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4.

S V H THNG THOT NC

S v h thng thot nc cho cc khu dn c 4.1 i vi cc im dn c c th la chn cc kiu h thng thot nc c bn nh quy nh ti iu 2.3 ca tiu chuN ny. Trong thc t, ph thuc vo n iu kin t nhin, hin trng thot nc v tnh cht th, c th p dng linh hot cc kiu h thng: - H thng thot nc chung: ch nn p dng i vi cc th c c mng li thot nc kiu chung hoc cc th c nhng iu kin t nhin thun li. Khi lp quy hoch thot nc cn xem xt kh nng c th ci to cng chung thnh cng ring hon ton trong tng lai. - H thngthot nc ring: p dng cho cc khu vc th mi, th m rng, khu dn c tp trung c mt dn trn 200 ngi/ha. - H thng thot nc hn hp: p dng cho cc thnh ph ln. Trong cc khu th c nc ma trn mi nh, trong sn vn, thng thot chung vi nc thi sinh hot. Vic ci to tch thnh hai h thng ring bit gp nhiu kh khn. Trong trng hp ny ta c h thng ring khng hon ton. -H thng na ring p dng cho cc khu vc th mi, c tiu chuN mi n trng cao, m bo iu kin v sinh cho cc ngun nc, h cha hay bi tm. 4.2 i vi cc im dn c nh di 5.000 ngi, ph thuc vo lng ma hng nm v cc iu kin khc c th p dng kiu ring khng hon ton hoc cng chung n gin.Ghi ch: Cng chung n gin l loi cng hp c y an bng b tng ct thp ch yu thot nc mt ng. Nc thi sinh hot c x l s b bng b t hoi trong tng ngi nh.

4. 3

i vi khu vc i ni c th p dng h thng thot nc ring khng hon ton trong nc ma x trc tip vo ngun tip nhn, nc thi c th vn chuyn t chy hoc bng p lc. C th p dng m hnh qun l tp trung cho mt hoc mt s im dn c hoc mt nhm cc ngi nh bit lp hoc phi hp vi nc thi khu vc sn xut. C th t chc thot nc phn tn khi mt dn c thp (di 200 ngi/ha) v iu kin v sinh cho php, c bit khng c nguy c gy nhim t, ngun cp nc. x l nc thi trong trng hp t chc thot nc tp trung c th p dng cc loi cng trnh: - X l sinh hc trong iu kin t nhin (cc kiu h sinh hc, bi lc ngm, bi thm,..).

4. 4

4. 5

4. 6



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- X l sinh hc trong iu kin nhn to (aeroten thi kh ko di, cc kiu b lc sinh hc, mng xy ha tun hon). 4. 7 x l nc thi trong trng hp t chc thot nc phn tn c th p dng cc loi cng trnh: - B t hoi cc kiu. - B t hoi cng vi cc cng trnh x l trong t. - Aeroten thi kh ko di. - H sinh hc v bi lc trng cy. Nhng c im thit k mng li thot nc cc c s cng nghip. 4.8 S lng mng li thot nc sn xut trong phm vi c s cng nghip c xc nh da vo thnh phn, lu lng, nhit , kh nng s dng li nc thI v s cn thit phi x l s b cc loi nc thi ny. Trong phm vi cc c s cng nghip, ph thuc vo thnh phn ca nc thi c th t ng ng thot nc trong rnh kn, mng h, trong ng hm (tunnel) hoc trn cu dn. Khong cch t thnh ca ng hm (tunnel) n cc cng dn nc thi cha cc cht n mn, cc cht c d bay hi hoc gy chy n (c t trng kh v hi nc nh hn 0,8 so vi khng kh) ly khng di 3m. Khong cch cc ng ng ny n cc tng ngm khng di 6m. Cc thit b kho chn, kim tra v u ni trn ng cng dn nc thi c cha cc cht c, d bay hi, d gy chy n phi m bo kn tuyt i. Tu theo vo thnh phn, nng v nhit ca nc thi sn xut c tnh n mn m s dng cc loi ng (ng snh, s, thu tinh, PVC, composite, thp lt cao su, gang tN nha ng,) cho hp l. mGhi ch:

4.9

4.10

4.11 4.12

Cc loi ng lm bng plyetilen, ng gang tm nha ng, ng lt cao su, c s dng khi nhit nc thi khng qu 60 0 C. Cc loi ng cht do khc phi theo ch dn p dng ca nh sn xut.

4.13 4.14

Xm ming bt ca cng dn nc thi c tnh axt bng si aming tN bi m tum v chn ngoi bng va xi mng chu axt. Phi c bin php bo v cc cng trnh trn mng li thot nc thi c tnh n mn khi tc hi do hi v nc; v phi m bo khng cho nc thN lu m vo t. Lng mng ca ging thm trn cng dn nc thi c tnh n mn phi lm bng vt liu chu n mn. Thang ln xung trong cc ging ny khng c lm bng kim loi d b n mn.Ghi ch: Nu ng knh ng dn nc di 600 mm nn lt lng mng dn bng cc on ng nha b i hoc cc vt liu chng n mn thch hp khc.

4.15



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4.16

Ging x nc thi cha cc cht d chy, d n ca cc phn xng phi c tm chn thu lc, cn trn mng li bn ngoi th phi theo tiu chuN thit n k x nghip cng nghip hoc cc qui nh ca cc c quan chuyn ngnh. cc khu vc kho, b cha nhin liu, cc cht d chy, cc cht c, axt v kim khng c nc thi bN th nc ma nn dn qua ging phn phi c n van. Trong trng hp bnh thng th x vo h thng thot nc ma, khi xy ra s c th x vo b cha d phng. S thot nc b mt b nhim bn ca cc im dn c v khu cng nghip

4.17

4.18

i vi cc khu dn c c h thng thot nc ring nu cha xt n yu cu x l nc mt b nhim bN (nc ma t u, nc ra ng, sn, bi,..), n th khi lp quy hoch tng th thot nc phi xem xt n yu cu ny to kh nng thc hin trong tng lai. Tuy nhin trc mt trong nhng iu kin thun li khuyn khch p dng cc bin php n gin (thm, cha) gim bt mc nhim do nc b mt. i vi khu vc bi tm, nui trng thu sn c bit (tm, c ging,) mun x nc ma vo phi c bin php gim nhim, p ng yu cu s dng nc ca tng i tng. i vi khu cng nghip, cn thc hin yu cu kim sot nghim ngt cc loi nc ma v nc b mt khc. Nc b mt b nhim bN phi c x n l m bo tiu chuN v sinh. Nc b mt tuy c coi l khng b nhim n bN cng cn phi tp trung vo h cha kim sot trc khi x vo ngun n tip nhn.

4.19

4.20



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5.

MNG LI THOT NC V CC CNG TRNH TRN MNG LI

Nguyn tc vch tuyn v lp t cng 5.1 Khi phn lu vc v vch tuyn mng li thot nc cn ch ti iu kin t nhin v qui hoch chung ca th, phi tn dng ti mc ti a iu kin a hnh xy dng cc tuyn cng t chy. i vi th ci to cn nghin cu s dng li mng li thot nc hin c. 5.2 B tr mng li thot nc trn mt bng tng th cng nh khong cch ti thiu tnh t mt ngoi cng ti cc cng trnh v h thng k thut khc phi tun theo Quy chuN xy dng h thng k thut h tng, ph hp vi quy n hoch tng th th ng thi c xem xt n iu kin c th ca tng tuyn ng. Khi b tr tuyn cng thot nc phi nghin cu kh nng s dng c gii thi cng. 5. 3 Khi b tr mt vi ng cng p lc song song vi nhau khong cch gia mt ngoi ng phi m bo kh nng thi cng v sa cha khi cn thit. Khong cch gia cc ng cng B nn ly khng nh hn cc tr s sau, tu theo vt liu ch to, p lc trong cng v iu kin a cht. -Khi ng knh cng n 300 mm: B = 0,7 m -Khi ng knh cng t 400 n 1000 mm: B = 1, 0 m -Khi ng knh cng trn 1000 mm: B=1,5 mGhi ch : Khi cn thit phi gim khong cch B theo qui nh ny th ng cng phi t trn nn b tng.

5. 4

Khi b tr ng cng trn cc tuyn ph phi ng thi b tr cc tuyn cng ph (cng cp 3 hoc cp 4) thc hin vic u ni vo nh. Khi u ni cc cng trong nh vi cng th phi c ging kim tra. Ging kim tra l mc gii quy nh phm vi trch nhim bo tr ca n v thot nc th v h thot nc.

5.5

Trn mng li thot nc thi cn xy cc ming x d phng x nc thi vo h thng thot nc ma hoc vo ngun tip nhn khi xy ra s c. Vic xy dng v xc nh v tr t ming x phi c s tho thun ca n v thot nc v c quan qun l mi trng a phng. Trong phm vi khu dn c, ng ng thot nc p lc khng c t ni hoc treo trn mt t. Ghi ch:Nu cng thot nc i qua cc h su, sng, h hoc khi t ng ng thot nc ngoi phm vi khu dn c, cho php t trn mt t hoc treo trn cu cn.

5.6

Gc ngot ca ng, ni ng, su t ng. 5.7 Gc ni gia hai tuyn cng thot nc khng nh hn 900.Ghi ch:http://www.nuoc.com.vn


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Cho php ly tu gc ni nu ni cng qua ging chuyn bc kiu thng ng hoc ni ging thu nc ma vi ging chuyn bc.

5.8

Nhng ch cng i hng cn xy dng ging thm lng mng ln cong vi bn knh, khng nh hn bn knh ging. Khi ng knh cng t 1200 mm tr ln, cho php xy dng cng ln cong vi bn knh khng nh hn 5 ln bn knh cng v phi c ging thm hai u on cng cong. Ni cng c ng knh khc nhau trong ging thm theo ct nh cng, hoc theo mc nc tnh ton. Ni rnh vi cng kn phi qua ging thm c h lng cn v song chn rc. su t cng nh nht hmin tnh i vi nh ng qui nh nh sau: - i vi cc cng c ng knh di 300 mm t khu vc khng c xe c gii qua li hmin =0,3 m . - ch c xe c gii qua li, hmin =0,7 m. Trong trng hp c bit khi chiu su nh hn 0,7 m th phi c bin php bo v cng.Ghi ch: su t cng ln nht xc nh theo tnh ton, tu thuc vo vt liu lm cng, iu kin a k thut v a cht thy vn, phng php thi cng v cc yu t k thut khc.

5.9 5.10 5.11

ng, gi ng, ph tng v nn t ng 5.12 C th s dng cc loi cng sau y thot nc: a) Cng t chy: cng b tng ct thp khng p, cng b tng, cng fibr xi mng sn xut bng phng php ly tm, cng snh v cc loi cu kin b tng ct thp lp ghp. b) Cng c p: dng ng b tng ct thp c p, ng fibr xi mng, ng gang, ng thp khng r v cc loi ng bng cht do.Ghi ch: - Tt c cc loi cng ngoi vic phi m bo bn c hc, chng thm, cn phi m bo nhn b mt pha trong theo tiu chun quc t. - Khi la chn loi cng thot nc cn tnh n vic dng vt liu a phng lm cng v cc iu kin thi cng ti ch khc (iu kin a k thut, mc nc ngm v.v). - Cho php dng ng gang thot nc t chy v ng thp thot nc p lc trong cc trng hp sau: - Khi t cng nhng khu vc kh thi cng, t ln, t trng n hoc snh ly, khu vc ang khai thc m, c hin tng cast, nhng ch i qua sng h, ng st hoc ng t, khi giao nhau vi ng ng cp nc sinh hot, khi t cng trn cu dn hoc nhng ni c th c nhng chn ng c hc. - Khi t cng trong mi trng xm thc, cn dng cc loi cng khng b xm thc hoc phi c cc bin php bo v cng khi xm thc. - ng thp phi c lp chng n mn kim loi mt ngoi. nhng ch c hin tng n mn in ho phi c bin php bo v c bit.

5.13

Khi s dng ng nha cng cn xem xt bin php bo v ng bng lp bc bn ngoi.



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5.14

Kiu nn t cng ph thuc kh nng chu lc ca t v cc ti trng c hc ln cng. Cng thot nc c th t trc tip trn nn t t nhin c m k. Trong trng hp t yu phi lm nn nhn to t cng. Cn da vo iu kin t nhin, trnh thi cng v kh nng s dng vt liu a phng la chn kiu nn t cng thch hp.

5.15 5.16

Trn ng cng thot nc p lc cn thit phi t cc van, van x, mi ni co gin, trong cc ging thm. dc ng cng p lc v pha van x khng c nh hn 0,001. ng knh ca van x phi m bo tho cn on cng khng qu 3 gi. Nn x nc vo h thng thot nc ma hoc vo ngun nc mt nu m bo cc iu kin v sinh. Trng hp khng th x c th phi xy dng trm bm cc b hoc chuyn nc thi bng t xitec.

5.17

Ti nhng v tr tuyn cng i hng dng chy, nu ng sut khng chuyn c vo ch ni cng th phi dng gi ta.Ghi ch: Trong cc trng hp sau y cho php khng dng gi ta : - ng p lc kiu ming bt vi p sut lm vic ti 100N/cm2 v gc ngot n 100 - ng c p bng thp hn t di t vi gc ngot n 300 trong mt phng thng ng.

Mi ni ng 5.18 5.19 Cng kiu ming bt ni bng giong cao su v cng hai u trn ni bng ai b tng ch s dng vi cc tuyn cng c ng knh nh. Yu cu i vi mi ni cc ng cng thot nc p lc c da theo tiu chuN thit k cp nc. n Ging thm 5.20 Trong mng li thot nc thi, ging thm cn t nhng ch: + Ni cc tuyn cng. + ng cng chuyn hng, thay i dc hoc thay i ng knh. + Trn cc on cng t thng, theo mt khong cch nht nh, ph thuc vo kch thc cng ly theo bng 5-1. Bng 5-1. ng knh ng D (mm) 150-300 400-600 700-1000 Trn 1000 Khong cch gia cc ging thm (m) 20-30 40 60 100

Ghi ch: i vi cc ng ng knh D400-600 mm nu y di 0,5 D v vn tc tnh ton bng vn tc nh nht th cc khong cch gia cc ging ly bng 30 m.

5.21

Trong ging thm, mp mng phi nm ngang vi ct nh cng c ng knh ln nht.



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Trong cc ging thm c cng ng knh t 700 mm tr ln cho php lm sn cng tc mt pha ca mng. Sn cch tng i din khng nh hn 100 mm. Trong cc ging thm c cng ng knh t 2000 mm tr ln cho php t sn cng tc trn dm cng xn; khi kch thc phn h ca mng khng c nh hn 2000x2000 mm. 5.22 Kch thc trn mt bng ca ging thm quy nh nh sau: a) Cng c ng knh nh hn hay bng 800 mm, kch thc bn trong ging thm bng: D = 1000 mm hoc a x b = 1000 x 1000 mm). b) Cng c ng knh D t 800 mm tr ln, kch thc ging thm l chiu di bng 1200 mm v chiu ngang D+500 mm). c) Ming ging c kch thc nh nht l 600x700 mm hoc ng knh 700 mm. ng knh ca ging trn ly nh sau: -n 1000 mm i vi ging c cng ng knh 600mm - n 1250mm i vi ging c cng ng knh 700mm - n 1500mm i vi ging c cng ng knh t 800 -1000mm - n 2000mm i vi ging c cng c ng knh t 1200mm tr ln.Ghi ch: Ging nh c chiu rng khng qu 700mmm, chiu su khng qu 1,20m. Ging c lm bng b tng hoc b tng ct thp. Ging ch xy bng gch i vi cc cng trnh thot nc cc khu dn c hoc th nh.

5.23 5.24 5.25

Kch thc mt bng ging thm nhng ch ngot phi xc nh theo iu kin b tr mng cong trong ging. Chiu cao phn cng tc ca ging (tnh t sn cng tc ti dn c ging) thng ly bng 1,8m. Cc ging c su di 1,8m th khng c c ging. Trong ging phi c thang phc v cho cng vic bo tr. Thang c th gn c nh ln thn ging hoc thang di ng. Khong cch gia cc bc thang l 300mm. Bc thang u tin cch ming ging 0,5m.

5.26

Trong nhng khu vc xy dng hon thin, np ging t bng ct mt ng. Trong khu vc trng cy, np ging cao hn mt t 50-70mm, cn trong khu vc khng xy dng l 200mm. Nu c yu cu c bit (trnh ngp nc ma) np ging c th t cao hn. Ging thm trong h thng thot nc ma c cu to tng t nh i vi nc thi nhng ring phn y ging cn c h thu cn. Tu theo mc hon thin ca cc khu vc c thot nc m chiu su h thu cn ly t 0,3 - 0,5 m. Phi chng thm cho thnh v y ging. Nu ging xy gch th lp chng thm phi cao hn mc nc ngm 0,5 m. Np ging thm v ging chuyn bc c th lm bng gang hoc b tng ct thp, chu c ti trng tiu chuN H30. n Nu dng np b tng ct thp th ming ging phi c cu to thch hp trnh b st, v do va p ca xe c cng nh khi ng m np. Kch thc np b tng ct thp phi m bo vic y, m np thun tin.Ghi ch:

5.27

5.28 5.29



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Trng hp np ging t trn ng c xe ti trng lng ln th phi tnh ton thit k ring.

5.30

Khi tuyn cng nm trn lng ng cao tc c mt giao thng ln, cho php xy dng h thm nm trn h ph v ni vi cng bng ng hm. Chiu cao ca hm bng chiu cao ca cng ln nht, y hm cao hn y cng 0,3 m. Ging kim tra v ging u ni vo cng th

5.31

Ging kim tra (xem iu 5.4) c mt bng hnh trn hoc vung kch thc 400x400mm hoc 600x600mm. Ging ny thng b tr trn h ph t khi m nn np ging c th lm bng b tng ct thp. Ging u ni vo cng th c th cu to n gin. Trong trng hp tuyn ph xy dng theo kiu nh chia l c nhiu cng u ni gn nhau. Ging ra cng

5.32

Cc on cng u mng li ca h thng thot nc ring hon ton thng khng m bo tc t ra sch nn b tr cc ging ra cng t ng. Ging chuyn bc

5.33

Ging chuyn bc c xy dng : + Chuyn nc thi, nc ma xung cng c su ln hn. + m bo tc chy ca nc trong ng khng vt qu gi tr cho php hoc trnh thay i t ngt tc dng chy. + Khi cn trnh cc cng trnh ngm. + Khi x nc theo phng php x ngp.Ghi ch: i vi ng c ng knh nh hn 600mm nu chiu cao chuyn bc nh hn 0,3m cho php thay th ging chuyn bc bng ging thm c p trn dng chy m. .

5.34 5.35

Ging chuyn bc vi chiu cao di 3m trn cc ng cng c ng knh t 600mm tr ln nn xy kiu p trn. Ging chuyn bc vi chiu cao di 3m trn cc ng cng c ng knh di 500mm nn lm kiu c mt ng ng trong ging, tit din khng nh hn tit din ng dn n. Pha trn ng ng c phu thu nc, di ng ng l h tiu nng c t bn kim loi y.Ghi ch: i vi cc ng ng c ng knh di 300mm cho php dng ct nh hng dng chy thay th cho h tiu nng.

5.36

Khi chiu cao chuyn bc ln hn qui nh trong iu 5.34 v 5.35 , cho php cu to ging theo thit k ring. Cc kiu ging thng p dng cho trng hp ny l: ging kiu bc thang, p trn xoy,... Ging thu nc ma

5.37

Ging thu nc ma t rnh ng vi khong cch xc nh theo tnh ton, ngoi ra cn phi b tr ging thu ch trng, cc ng t ng v trc gii i b qua ng



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Khi ng ph rng di 30m v khng c ging thu bn trong tiu khu th khong cch gia cc ging thu c th ly theo bng 5-2. Bng 5-2. dc dc ng ph Nh hn hoc bng 0,004 T 0,004 n 0,006 T 0,006 n 0,01 T 0,01 n 0,03 Khong cch gia cc ging thu (m) 50 60 70 80

Ghi ch: 1. Qui nh ny khng p dng i vi ging thu kiu h b va (ging thu hm ch). 2. Khi chiu rng ng ph ln hn 30m hoc khi dc ln hn 0,03 th khong cch gia cc ging thu khng ln hn 60m. 3. i vi cc th c cng ma ln, ng ph c nhiu l cy hoc rc thi th nn p dng kiu ging thu kt hp (va thu mt ng va thu b va) hoc tng chiu di ging thu gp i so vi loi ging thu thng thng. 4. i vi nhng khu vc thp (thng l cc ng t ng) ni hi t nhiu dng nc th s lng ging thu phi tng ln gp i. 5. i vi khu th vng i ni, ng ph thng c dc ln ti cc im t ging thu cn h thp mt ng khong 0,1m hoc to ra gc ngot tng kh nng thu nc ca cc ging thu.

5.38 5.39 5.40

Chiu di ca on ng ni t ging thu n ging thm ca ng cng khng ln hn 40m. Cho php ni cc cng thot nc ma ca ngi nh vo ging thu nc ma y ca ging thu nc ma phi c h cha cn chiu su t 0,3 - 0,5m v ca thu phi c song chn rc. Mt trn song chn rc t thp hn rnh ng khong 20 - 30mm. i vi h thng thot nc chung trong cc khu dn c, ging thu phi c kho thu lc ngn mi; chiu cao lp nc khng nh hn 0,1m. i vi cc th vng c lng bc hi hng nm ln nn p dng loi kho thu lc kt hp trong ging thm (ging ni vi ging thu). Mc d c kho thu lc nhng trong mi trng hp vn cn ch thng hi cho mng li cng thot nc. Ni mng h vi cng kn bng ging thm c h thu cn, pha ming h phi t song chn rc c khe h khng qu 50mm; ng knh on ng ni xc nh bng tnh ton nhng khng nh hn 300mm. i vi mng li thot nc ma khi chnh ct cc y cng nh hn hoc bng 0,5m, ng knh cng di 1500mm v tc khng qu 4m/s th cho php ni cng bng ging thm. Khi chnh ct ln hn phi c ging chuyn bc. ng lun qua sng, sui, knh

5.41

5.42

5.43

5.44

ng knh ng lun qua sng, sui khng nh hn 150mm.



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S ng lun lm vic bnh thng t nht l hai, ng bng thp c lp ph chng n mn v c bo m khi cc tc ng c hc. Mi ng ng phi c kim tra kh nng dn nc theo lu lng tnh ton c xt ti mc dng cho php. Nu lu lng nc thi khng m bo tc tnh ton nh nht th ch s dng mt ng ng lm vic v mt ng ng d phng. Ngoi hai ng ng lm vic xy dng thm mt ng ng d phng khi cn x s c. Khi thit k ng lun qua sng s dng lm ngun cp nc phi xin php c quan qun l ti nguyn v mi trng hoc c quan v sinh d phng a phng. Khi thit k ng lun qua sng c tu thuyn qua li phi theo cc qui nh an ton ng sng v phi c php ca c quan qun l ng sng.Ghi ch: Khi i qua cc khe, thung lng kh cho php t mt ng ng lun.

5.45

Khi thit k ng lun, nn ly: -nh ng lun nm su, cch y sng ti thiu l 0,5 m. -Trong on sng c tu thuyn qua li nhiu th chiu su khng c nh hn 1m. -Gc nghing ca on ng chch hai b sng khng ln hn 200 so vi phng ngang. -Khong cch mp ngoi gia hai ng lun khng nh hn 0,7 - 1,5m, ph thuc vo p lc nc trong ng. Trong cc ging thm t ca vo, ca ra v ging x s c phi lp t phai chn. B tr ging x s c phi c php ca c quan qun l ti nguyn nc v mi trng a phng. Nu ging thm xy dng cc bi bi ven sng th phi d tnh kh nng khng cho ging ngp vo ma nc ln. i vi h thng thot nc chung th phi kim tra mt ng ng lun m bo iu kin thot nc trong ma kh theo cc tiu chuN qui nh. n ng ng qua ng.

5.46

5.47 5.48

5.49 5.50 5.51

Khi xuyn qua ng st, ng t ti trng ln hoc ng ph chnh th ng cng thot nc phi t trong ng bc hoc ng hm. Trc v sau on cng qua ng phi c ging thm v trong trng hp c bit phi c thit b kho chn. H s thit k cng qua ng phi c s chp thun ca cc c quan lin quan. Cng x nc thi, nc ma v ging trn nc ma.

5.52

Cng x nc thi vo sng h phi m bo iu kin pha long tt nc ngun vi nc thi v khng nh hng n m quan v mi trng khu vc. Cng x vo sng cn b tr nhng ch c th tng cng chuyn ng ri ca dng chy (ch co hp, thc ghnh...). Tu theo iu kin x nc thi



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x l vo sng m p dng kiu x: x ven b hoc x gia lng sng, x tp trung hoc x khuych tn. Khi x nc thi x l vo h cha nc, ming x phi nm ngp su di nc. 5.53 ng dn nc thi x gia lng sng v x ngp su di nc phi bng thp c lp chng n mn v c t trong rnh. Ming x gia lng sng, x ven b v x ngp nc u phi c gia c bng b tng. Cu to ming x phi xt ti cc yu t tu thuyn i li, mc nc sng, nh hng ca sng, iu kin a cht, s thay i lng sng,... 5.54 Cng x nc ma c th p dng cc kiu: 1. Khi khng gia c b - kiu mng h. 2. Khi gia c b - kiu ming x ng kn.Ghi ch : ngn nga hin tng nc chy ngc t ngun tip nhn vo h thng cng (trong cc trng hp mc nc trong ngun tip nhn cao hn mc nc trong cng), ti cc ming x cn phi lp t van ca chng chy ngc.

5.55

Ging trn nc ma ca h thng thot nc chung phi c p trn ngn nc thi. Kch thc v cu to p trn ph thuc vo lu lng nc x vo ngun, cc mc nc trong cng v ngun tip nhn. Ging trn nc ma phi c ngn lng ct v song chn rc. V tr ming x nc thi hoc nc ma v cu to ca n cn phi c s chp thun ca cc c quan qun l ti nguyn v mi trng v c quan qun l ng sng a phng . Thot kh cho mng li thot nc.

5.56

5.57 5.58

Vic thot kh cho mng li thot nc thi c thc hin thng qua ng ng trong nh hoc khe h trn cc ging thm. Cc thit b thot kh c bit c b tr cc ca vo ng lun qua sng, trong cc ging thm ( nhng ch tc dng chy h thp trong cc cng c ng knh ln hn 400mm) v trong cc ging chuyn bc khi cao chuyn bc trn 1m v lu lng nc thi trn 50 l/s. Trong nhng trng hp c bit cho php thit k h thng thot kh cng bc. Trong trng hp thot kh t nhin cho mng li thot nc bn ngoi dn cc loi nc thi c cha cht c hi v cht d gy chy n th ti mi im u ni cng trong nh vo cng bn ngoi phi b tr cc ng ng thot kh c ng knh khng nh hn 200mm.

5.59 5.60



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6.

TRM BM V TRM CP KH.

Yu cu chung 6.1 Theo mc tin cy, trm bm nc thi v trm cp kh c phn bit thnh ba loi, nu trong bng 6.1. Bng 6-1.Phn loi theo tin cy Loi I Loi II Loi IIIGhi ch:

c tnh lm vic ca trm bm Khng cho php ngng hay gim lu lng Cho php ngng bm nc thi khng qu 6 gi Cho php ngng bm nc thi khng qu 1 ngy

Vic ngng bm nc thi quy nh cho trm bm loi II v loi III c xt n iu kin cng ngh sn xut hay l ngng cp nc khng qu 1 ngy cho cc khu dn c di 5.000 ngi.

6.2

Khi thit k trm bm nc thi sn xut l nc nng, nc c cha cc cht d chy n, cc cht c hi th ngoi vic tun th theo quy nh ca tiu chuN ny cn phi tun theo cc tiu chuN ca cc ngnh cng nghip tng n n ng. Trm bm nc thi

6.3

La chn my bm, thit b v ng ng dn nc thi c la chn ph thuc vo lu lng tnh ton, chiu cao ct nc cn bm, tnh cht ho l ca nc thi v cn lng, c tnh n cc c tnh ca my bm v ng ng cng nh vic a cng trnh vo s dng theo tng t. S lng my bm d phng xc nh theo bng 5.2. Bng 6-2.Nc thi sinh hot hoc nc thi sn xut c Nc thi c tnh n mn tnh cht gn vi nc thi sinh hot S my bm S my bm S my bm d phng theo Lm vic D phng p dng lm vic tin cy ca trm bm cho tt c cc loi trm bm Loi I Loi II Loi III 1 2 1 1 1 1 2 2 1 1 2-3 2 3 v nhiu 2 2 1 v 1 4 3 hn trong kho 5 v nhiu Khng nh hn 50% hnGhi ch: 1. Trong trm bm nc ma khng c my bm d phng, tr trng hp khi gp s c m nc ma khng th x c. 2. Khi ci to nhm tng cng sut trm bm i vi trm bm loi III bm nc thi sinh hot, nc thi sn xut c tnh cht gn vi nc thi sinh hot th cho php khng c bm d phng nhng phi c bm sn trong kho.



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6.4

Trm bm nc thi sinh hot v nc mt b nhim phi c xy dng thnh cng trnh ring bit. Trm bm nc thi sn xut cho php xy dng hp khi trong nh sn xut hay trong nh ph tr sn xut. Trong gian my ca trm bm cho php t cc loi bm bm cc loi nc thi khc nhau, tr trng hp i vi nc thi nng, nc thi c cha cc cht d chy n v cc cht c hi. Cho php t my bm bm nc thi sinh hot trong nh ph tr ca trm x l nc thi.

6.5 6.6

Trn tuyn ng dn nc thi vo trm bm phi c van chn v c th ng trn mt t ng m c. S lng ng ng p lc i vi trm bm loi I khng nh hn 2 v phi m bo khi c s c mt ng ng ngng lm vic th ng dn cn li phi m bo ti 100% lu lng tnh ton; khi phi xt n vic s dng my bm d phng. i vi trm bm loi II v loi III cho php ch c mt ng ng p lc. My bm nc thi nn b tr t mi nc. Trng hp my bm b tr cao hn mc nc trong ngn thu th phi c bin php mi nc cho n. Ct trc my bm bn cn lun t thp hn mc bn trong ngn cha bn. Mi my bm cn c mt ng ht ring. Vn tc nc thi hay bn cn trong ng ht v ng N phi m bo y khng gy lng cn. i vi nc thi sinh hot th vn tc nh nht ly theo quy nh ti iu 3.33. Trong cc trm bm bn cn cn phi c bin php ra ng ht v ng N y. Trong trng hp c bit cho php ra cc ng ny bng bin php c hc. bo v my bm khi b tc nghn th trong ngn thu nc thi cn lp t song chn rc th cng, song chn rc c gii hoc song chn rc kt hp nghin rc. Khi khi lng rc di 0,1 m3/ngy cho php s dng song chn rc th cng. B rng ca khe h song chn rc ly nh hn 10 - 20mm so vi ng knh ca vo ca my bm. Khi s dng song chn rc c gii hoc song chn rc kt hp nghin rc, s lng thit b d phng c ly theo bng 6-3 . Bng 6-3.Loi song chn rc 1. Song chn rc c gii c khe h - trn 20 mm - 16 - 20 mm 2. Song chn rc kt hp nghin rc - t trn ng dn - t trn knh mng 3. Song chn rc th cng S lng Lm vic 1 n 3 trn 3 1 n 3 1 n 3 trn 3 1 D phng 1 2 1 (th cng) 1 2 -

6.7

6.8 6.9

6.10 6.11



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6.12 6.13

Vn tc nc thi ng vi lu lng ln nht qua khe h ca song chn rc c gii l 0,8 - 1 m/s, qua song chn rc kt hp nghin rc l 1,2 m/s. Nu trong trm bm s dng song chn rc c gii th phi c my nghin rc. Rc sau khi nghin nh c x vo trc song chn rc. Nu khi lng rc trn 1,0 T/ngy cn c my nghin rc d phng. Khi lng rc ly t song chn rc c th tnh s b theo bng 6-4. Bng 6-4.Chiu rng khe h ca song chn rc (mm) 16 - 20 25 - 35 40 - 60 60 - 80 90 - 100 S lng rc ly ra t song chn rc tnh cho mt ngi (l/nm) 8 3 2,3 1,6 1,2

6.14

Khi lng ring ca rc ly khong750 kg/m3, h s khng iu ho gi ca rc a ti trm bm s s b ly bng 2. 6.15 Quanh song chn rc c gii hoc my nghin rc phi c li i li, chiu rng khng nh hn 1,2 m, cn pha trc song chn rc th chiu rng li i khng nh hn 1,5 m. i vi song chn rc th cng chiu rng ly bng 0,7 m. Khi xc nh kch thc mt bng ca gian my, chiu rng ti thiu ca li i gia cc b phn li nht ca my bm, ng dn v ng c ly nh sau: a) Gia cc t my - nu ng c in c in p nh hn 1000 V th chiu rng nh nht 1m. Nu ng c c in p trn 1000 V th chiu rng 1,2m. b) Gia t my v tng trm bm: -Trong trm bm kiu ging ly bng 0,7m. -Trong cc trm bm kiu khc ly bng 1m. c) Trc cc bng in - 2m d) Gia phn li cc b phn c nh ca thit b: 0,7m. Trong cc trm bm phi c sn lp my, kch thc ca sn phi m bo chiu rng ca li i xung quanh thit b khng nh hn 0,7m, k c khi a thit b nng cN ti v tr lp. uGhi ch: 1. Trong cc trm bm t su s dng ng c in p di 1000 V v ng knh ng ht di 200mm, cho php t cc my bm cch tng gian my nh nht l 0,25m, nhng chiu rng li i gia cc t my phi theo ng qui nh ni trn. 2. Cho php t 2 my bm c ng c in cng sut ti 125 KW in p di 1000 V trn cng mt b mng khng cn li i gia 2 my nhng phi bo m li i xung quanh ca my c chiu rng khng nh hn 0,7m.

6.16

6.17

Chiu cao phn trn mt t ca gian my (tnh t sn lp my ti mt di ca dm mi) ph thuc vo cc thit b nng chuyn, chiu cao ca my bm, chiu di ca dy cp (t 0,5 - 1m), khong cch t sn lp ti t my bm (khng ln hn 0,5m), kch thc ca thit b nng chuyn (tnh t mc ti mt di ca dm mi).



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6.18

qun l cc ph tng v thit b, trm bm cn c trang b thit b nng chuyn: - Nu trng lng thit b di 1 tn th dng palng treo c nh hoc dm cN u treo iu khin bng tay. - Nu trng lng thit b di 5 tn dng dm cN treo iu khin bng tay. u - Nu trng lng thit b trn 5 tn dng cn trc iu khin bng in.Ghi ch :

Khi cu thit b vi chiu cao t 6m tr ln hoc chiu di gian my trn 18m cn dng thit b nng chuyn chy in.

6.19

Sn gian my phi c h thu nc r r v phi c my bm hoc bin php thu nc r r ring. dc ca sn v pha h thu nc r r ly 0,01 - 0,02. Th tch ca ngn thu trm bm xc nh theo lu lng nc thi, cng sut v ch lm vic ca my bm nhng khng c nh hn ca mt my bm cng sut ln nht lm vic trong 5 pht. Ngn thu ca cc trm bm cng sut ln hn 100.000 m3/ngy cn chia ra hai ngn nhng khng c lm tng th tch chung. Th tch ngn thu ca trm bm cn ti, cn ln men hoc bn hot tnh xc nh theo khi lng ca bn cn x ra t cc b lng, b mtan, bn hot tnh tun hon v bn hot tnh d. Th tch nh nht ca ngn thu ca trm bm bn dng bm bn cn lng ra ngoi phm vi trm x l xc nh bng cng sut ca mt my bm lm vic trong 15 pht. Nu bn cn t cc cng trnh x l a ti ngn cha khng lin tc trong thi gian my bm hot ng th th tch ngn cha cho php gim bt. Ngn cha ca trm bm bn cho php s dng lm thit b nh lng hoc cha nc khi thau ra ng ng dn bn. Trong ngn cha bn phi c thit b sc bn v ra b. dc ca y b v pha h thu nc khng c nh hn 0,1. Ngn thu ca trm bm nc thi c th chia thnh nhiu phn ring bit tch cc loi nc thi khc nhau nu nh chng cn x l ring hoc khi xo trn vi nhau to thnh cc loi kh c hoc lng cn. Khong cch t mt ngoi ca ngn thu cc loi nc thi sn xut c cha cc cht d chy n v cht c hi ti cc cng trnh khc c qui nh nh sau: - n nh ca trm bm khng nh hn 10m. - n cc nh xng khc khng nh hn 20m. - n cc nh cng cng khng nh hn 100m. Kt cu ngn thu nc thi c cha cc cht n mn hoc cc cht c hi phi bo m khng cc cht ny ngm vo t; i vi loi nc thi c cht n mn phi c cc bin php chng n mn. Gian my ca trm bm nc thi c tnh n mn cn c cc bin php chng n mn cho cc kt cu xy dng (sn, mng v.v... ). Trong cc trm bm nc thi c tnh n mn, c cc cht d chy, n hoc cc cht c d bay hi nn t ng ng v ph tng trn mt sn v phi

6.20

6.21 6.22

6.23

6.24

6.25 6.26



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thun tin kim tra v sa cha khi cn thit, s lng van nn dng mc t nht.Ghi ch : Khi t ng ng trong rnh cn c bin php thng gi cho rnh hoc lp rnh bng ct .

6.27 6.28

Pha trc trm bm nc thi trong h thng thot nc chung hoc h thng na ring cn phi c b lng ct. Trong trm bm cn c khu vc ph tr sinh hot (thit b v sinh, tm thay qun o). Din tch nh ph tr ph thuc vo cng sut trm bm, quy nh trong bng 6-5. Bng 6-5.Cng sut (m3/ngy) trm bm 8 12 20 Din tch ph tr (m2) Khu phc v Xng 10 15 25 Kho 6 6 10

n 5.000 T 5.000 n 15.000 T 15.000 n 100.000 Trn 100.000

Ghi ch: 1. Khu ph tr trong cc trm bm t trong cc nh my, x nghip v cng trnh x l c th khng cn thit nu c nhng cng trnh tng t trong ngi nh gn . Khi khong cch trn 50m th cn c thit b v sinh b tr trong trm bm. 2. Trong cc trm bm khng c ngi phc v thng xuyn th khng cn c phng ph tr.

Trm cp kh 6.29 Trm cp kh lm sc kh v cung cp xy cho nc thi phi c b tr gn ni s dng v gn thit b phn phi in nm trong phm vi trm x l nc thi. Trong cc nh ca trm cp kh cho php t cc thit b lc khng kh, cc my bm bm nc k thut v x cn b aerten, my bm bn hot tnh, cc thit b iu khin tp trung, cc thit b phn phi, my bin p, cc phng sinh hot v cc thit b ph tr khc. Khi thit k trm cp kh phi xt ti kh nng tng cng sut thit k bng cch t cc my cp kh b sung hoc thay th bng cc my c cng sut ln hn. Trm cp kh phi c cp in lin tc. Cng sut, loi my v s lng my cp kh phi la chn da trn tnh ton cng ngh ca cc cng trnh c cp kh, c ch ti cc c im cu to ca cc cng trnh ny. Khi cng sut ca trm cp kh trn 5000 m3/h t nht phi c 2 my lm vic, khi cng sut nh hn th cho php lp t 1 my lm vic. S my d phng quy nh nh sau: - Khi 3 my lm vic - 1 my d phng. - Khi 4 my lm vic tr ln - 2 my d phng.

6.30

6.31 6.32

6.33



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6.34 6.35

Trong trng hp cn thit c th cp du tp trung cho cc my cp kh Cn phi cp nc lm mt lin tc cho cc trc ca cc cm my v cc b phn lm ngui du ca my cp kh. Cht lng v nhit ca nc lm mt phi m bo theo ng yu cu ca hng sn xut my cp kh. Gian my phi tch ring vi cc phng khc v c ca trc tip thng ra bn ngoi. Khi b tr cc thit b trong gian my cn m bo cc iu kin sau y: a) Li i gia cc t my v tng nh: - T pha my cp kh khng nh hn 1,5m. - T pha ng c in: tho rto. b) Li i gia cc phn li ca cc t my khng t hn 1,5m. qun l cc ph tng v thit b, trm cp kh phi c thit b nng chuyn theo qui nh iu 6.18. Thit b trao i khng kh phi c thit k theo qui nh v thng gi, cp nhit v iu ho khng kh hoc theo s ch dn ca c quan t vn chuyn ngnh. Khng kh phi c lc sch trong b lc kn. B tr cc b lc kh phi m bo kh nng tho g tng chic thay th v phc hi. Khi c 3 b lc kh lm vic th cn mt b lc d phng, nu ln hn ba th cn 2 b d phng. Ghi ch:1. Nu phn phi khng kh trong aeroten bng cc ng khoan l th cho php dng khng kh khng cn lc sch. 2. Khi cng sut ca trm cp kh trn 20 nghn m3/h th mi t my phi c bung thu v lc kh ring bit.

6.36 6.37

6.38 6.39

6.40

Vn tc chuyn ng ca khng kh qui nh: - Trong cc bung lc - di 4 m/s - Trong cc mng dn - di 6 m/s - Trong cc ng dn - t (10 - 25) m/s n 40 m/s Khi tnh ton ng dn nn ch ti hin tng tng nhit ln khi khng kh b nn v m bo chnh p nh nht gia cc ngn ca cng trnh c cp kh.Ghi ch: Tr s tnh ton tn tht p lc trong cc thit b phn phi kh c xt ti sc cn tng theo thi gian s dng.

6.41

6.42

Nu dng ng thp thnh mng, hn in, lm ng dn khng kh c p, cn c bin php chng n v cch nhit cho ng khi t trong nh.



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7.

CC CNG TRNH X L NC THI

Cc qui nh chung 7.1 Phng php v mc x l nc thi ph thuc vo lu lng v thnh phn, tnh cht nc thi, c im ngun tip nhn v cc yu cu v sinh khi x nc thi vo ngun v cc iu kin c th ca a phng,. Nc thi khi x vo ngun phi p ng quy nh ca cc tiu chuN mi trng hin n hnh. Phi c gng tn dng iu kin t nhin sn c nh ao, h, bi t trng cy v.v... x l nc thi. Ch khi cc phng php x l bng iu kin t nhin khng cho php hay khng th p dng, mi xy dng cc cng trnh x l nc thi nhn to. Phi c gng tn dng nc thi x l cho sn xut nng nghip hoc cho cc mc ch kinh t khc. Bn cn ca nc thi phi c x l trc khi s dng lm phn bn hoc cho cc mc ch khc.Ghi ch: Mc x l nc thi sinh hot ti a nn gii hn theo hiu qu x l m cc cng trnh x l sinh hc hon ton trong iu kin nhn to c th m bo c (BOD5 ca nc sau x l thp nht l 8-10mg/l ).

7.2

Hn hp nc thi sinh hot v sn xut khi a ti trm x l sinh hc lun phi bo m cc yu cu sau: - pH khng nh hn 6,5 v khng ln hn 8,5 - Nhit khng di 100C v khng trn 400C - Tng hm lng ca cc mui ho tan (TDS) khng qu 15g/l BOD5 khi a vo b lc sinh hc hoc aeroten N khng qu 500mg/l; Khi y a aerten kiu phn phi nc phn tn khng qu 1000mg/l. - Nng cc cht hu c khng vt qu qui nh ghi trong bng 7-1 v cc cht c hi khng vt qu quy nh nu trong bng 7-2. Nc thi khng cha m khng ho tan, nha v du mazut. - Khng cha cc cht hot ng b mt khng th oxy ho c trong cc cng trnh x l. - Hm lng cc cht dinh dng khng c thp hn qui nh trong bng 73.



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Bng 6-1.Nng Nng cho gii php(mg/l), hn cho Tc xy ho trong nc thi php th (x l trung bnh khi i vi sinh hc hon x l trong nc aerten trn (mg ton trong cc thi x aerten vi BOD5/ g cht l trong kh bn hot liu lng bn cac tnh / gi) 1,8g/l, thi aerten gian thi kh 7 trn gi) (mg/l) 100 9 6 750 12 20 600 28 40 150 14 15 600 15 10 1150 30 90 300 22 25 400 3,5 6 950 23 30 600 18 12 200 8 15 200 26 45 1000 14 15 700 19 14 400 100 6

Cc cht

BOD5 (mg/mg ca cc cht phi xt)

COD (mg/mg ca cc cht phi xt)

1 - Anilin 2 - Axetandehyt 3 - Axeton 4 Axit Benzonic 5 - Butanol 6 Glixrin 7 - Caprolactam 8 Andehit Crotonic 9 - Metanof 10 - Propanol 11 - Toluen 12 - Axit axtic 13 - Phenol 14 - Etanol 15 - Dietyl hecxanol

1,9 1,07 1,68 1,61 1,8 0,86 1,8 1,6 1,05 1,68 1,1 0,86 1,18 1,45 1,55

2,4 1,88 2,17 1,97 2,58 1,23 2,12 2,5 1,5 2,4 1,87 1,06 2,38 2,08 2,55

Ghi ch: 1. Tc xy ho trung bnh ca hn hp gm nhiu cht phi xc nh bng thc nghim. Khi khng xc nh c bng thc nghim th mi c tnh theo gi tr trung bnh cng ca tc xy ho i vi tng cht (tnh theo t l ca khi lng v BOD5 ca cc cht) trong thi gian thi kh. 2. Khi ni cng thot nc ca cc x nghip cng nghip vo h thng thot nc th th nng tnh ton ca cc cht l nng trong dng chy chung.



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Bng 6-2.Nng cho php ca ring tng cht trong nc thi khi a ti cc cng trnh x l sinh hc hon ton (mg/l) 25 Mc loi tr cc cht bN trong qu n trnh x l hon ton (%) 85 - 90

Tn gi cc cht 1 - Du v sn phN du m m(1)

2 - Cc cht hot tnh b mt tng hp (2) 20 -Cht d oxy ho anion 80 50 -Cht d oxy ho khng in 90 20 -Cht trung gian anion 60 20 -Cht trung gian khng in 75 25 3 - Formalhit 80 1 4 - Sunfit 99,5 0,5 5 - ng 80 0,5 6 - Kali 50 0,1 7 - Cadmi 60 2,5 8 - Crm ho tr 3 20 1 9 - Km 70 25 10 - Thuc nhum lu ho 90 25 11 - Thuc nhum tng hp 70 0,1 12 - Asen (3) 50 1,5 13 - Xianua 0,005 14 - Thu ngn 0,1 15 - Ch 50 1 16 - Cban 20 Ghi ch: (1) Sn phm du m l cc cht t vn cc hoc khng vn cc, tan trong dung dch hecxen. (2) Nu trong nc thi c cc hp cht hot tnh b mt anion v khng ln, nng chung ca cc hp cht ny khng vt qu 20 mg/l. (3) Khng k Feroxianua.

Bng 7-3.Hn hp nc thi sinh hot v sn xut Hm lng nh nht phi c ca cc cht dinh dng Tng nit (mg/l) Tng pht pho (mg/l)

BOD5 Tnh cho mi 100 mg/l 5 1 (i vi cng trnh x l sinh hc hiu kh) COD Tnh cho mi 350 mg/l 5 1 (i vi cng trnh x l sinh hc ym kh) Ghi ch: 1. Nng cho php ca cc cht trong bng 7-2 v 7-3 khi cn thit phi ly gim i m bo nng gii hn cho php ca cc cht c trong nc sng, h sau khi x nc thi c x l, trong trng hp ny phi xt n hiu qu x l v mc pha long ca sng, h. 2. Khi cn gim BOD5 ca nc thi a vo cng trnh x l sinh hc th nn dng nc thi lm sch pha long. 3. Khi x nc thi sn xut vo mng li thot nc th, t l COD: BOD5 khng c vt qu 1,5.http://www.nuoc.com.vn


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7.3

Nu cc qui nh nu trong iu 7.2 khng c tho mn th nc thi sn xut trc khi x vo h thng thot nc ca khu dn c, phi c x l s b. Cc yu cu i vi nc thi sn xut cn x l sinh hc trong cc cng trnh x l ring ca c s cng nghip hay trong hn hp vi nc thi sn xut vi nc thi sinh hot c chnh l theo ti liu thc nghim hoc ti liu ca cc c s cng nghip tng t. Khi lng nc thi sinh hot ca th hoc khu dn c a v trm x l c xc nh theo tiu chuN cp nc v ph thuc vo loi h thng thot n nc. i vi h thng thot nc ring, cng sut trm x l nc thi sinh hot th bng 0,7 1,0 ln lng nc cp sinh hot; i vi h thng thot nc na ring bng 1,0 n 1,3 ln v i vi h thng thot nc chung l 1,5 n 2,0 ln. Khi lng nc thi sinh hot v ch a nc ti trm x l phi xt ti bao ph ca h thng thot nc, s pht trin tng lai ca cc khu dn c tng ng vi tiu chuN thi nc, h s khng iu ho chung v biu n thi nc trong ngy.

7.4

7.5

7.6

Cng sut ca trm x l nc thi ca khu cng nghip tp trung c xc nh da vo lng nc thi ca tng nh my a v trm. Trong trng hp khng c s liu ny th cng sut ca trm x l nc thi Q(m3/ngy) c xc nh theo cng thc sau y: Q= qxF Trong : q-Tiu chuN nc thi (m3/ha. ngy), ph thuc vo loi hnh sn xut n trong khu cng nghip; i vi loi hnh sn xut t nc thi, q s b ly bng 15-25 m3/ha.ngy; i vi loi hnh sn xut c lng nc thi trung bnh q ly bng 30 n 40 m3/ha.ngy v i vi loi hnh sn xut nhiu nc thi q ly bng 50 n 70 m3/ha.ngy. F- Din tch khu cng nghip m h thng thot nc thi phc v, ha. (7-1)

7.7

Khi thit k cng trnh lm sch cho cc th xy dng mi th tu theo mc tin nghi v cc iu kin a phng, lng cht bN tnh cho mt ngi n dn xc nh nng cht bN ca nc thi sinh hot c th xc nh s b n theo bng 7-4. S lng v ch thi nc, thnh phn v nng cht bN trong nc thi n sn xut c xc nh theo ti liu cng ngh. Bng 7-4.Cc i lng Cht rn l lng BOD5 ca nc thi lng BOD5 ca nc cha lng Nit ca cc mui amni (N NH4) Pht pht ( P2 O5 ) Clorua (Cl-) Cht hot ng b mt Khi lng (g/ngi. ngy) 60 -65 30 -35 65 8 3,3 10 2- 2,5



TCXDVN-51:2008

Ghi ch: Khi x nc thi sinh hot ca cc x nghip cng nghip vo mng li thot nc ca khu dn c th khng cn tnh b sung cc cht bn cha trong cc loi nc .

7.8 7.9 7.10

Lu lng tnh ton ca nc thi cn xc nh theo biu tng hp lu lng cho c trng hp dng trm bm hay t chy. Tnh ton cc cng trnh x l sinh hc tin hnh theo tng khi lng cht bN hu c biu th bng BOD5. n C th x l c hc chung hoc tch x l c hc ring r i vi nc thi sinh hot v nc thi sn xut a i x l sinh hc chung. Nn p dng x l c hc ring r i vi loi nc thi sn xut c cha cc cht d gy chy n, cng nh khi cn x l nc thi sn xut bng phng php ho hc hoc l hc.Ghi ch: Bt buc phi lm sch c hc ring r trong trng hp phng php x l cn lng ca cc loi nc thi khc nhau.

7.11

La chn cc loi cng trnh x l nc thi ph thuc vo c im v lu lng nc thi a ti trm x l, mc x l cn thit, phng php s dng bn cn v cc iu kin c th khc ca a phng. La chn v tr v din tch khu t xy dng trm x l nc thi phi tun theo cc thit k qui hoch v xy dng ca i tng cn c thot nc, c ch n cc gii php cng trnh th bn ngoi (ng st, ng t, cp nc, hi nhit, in,...). V tr trm x l trm x l nc thi phi p ng quy nh ca iu 2.16 ca tiu chuN ny hoc cc iu quy nh lin quan n nu trong TCVN 7222:2002- Yu cu chung v mi trng i vi cc trm x l nc thi sinh hot tp trung. Khu t xy dng trm x l thng b tr cui hng gi ch o ca ma h so vi khu vc xy dng nh v pha di im dn c theo chiu dng chy ca sng. Khu t xy dng phi c dc m bo nc thi t chy c qua cc cng trnh v thot nc ma thun li, khu t xy dng trm phi b tr ni khng ngp lt v c mc nc ngm thp.Ghi ch: Cho php b tr trm x l u hng gi nhng khong cch ly v sinh phi ly tng ln theo qui nh iu 2.16.

7.12

7. 13

7.14

Quy hoch trm x l nc thi phi bo m s dng hp l khu t cho giai on d tnh cng nh cho giai on pht trin tng lai. B tr cc cng trnh phi m bo: - Kh nng xy dng theo tng t. - Kh nng m rng cng sut khi lu lng nc thi tng. - Chiu di cc ng ng k thut phi ngn nht (mng dn, ng dn v.v...). - Thun tin cho qun l v sa cha. Khi thit k trm x l nc thi cn xt n kh nng hp khi cng trnh cng nh hn ch mi hi lan truyn ra mi trng xung quanh. Cc cng trnh x l nc thi cn b tr ngoi tri, ch trong trng hp c bit v c l do xc ng mi c lm mi che.

7.15 7.16



TCXDVN-51:2008

7.17

Trong trm x l nc thi cn c cc thit b sau y: a) Thit b phn phi u nc thi n cc cng trnh n v. b) Thit b cho cng trnh tm ngng hot ng, tho cn v thau ra cng trnh, ng ng dn khi cn thit. c) Thit b x nc khi xy ra s c trc v sau cc cng trnh x l c hc v phi c li i li d dng ti cc thit b ng m. d) Thit b o lu lng nc thi, bn cn lng, bn hot tnh tun hon v bn hot tnh d, khng kh, hi nc, nng lng v.v... e) Thit b ly mu t ng v dng c t ghi cc thng s cht lng nc thi, v bn cn lng. Mng dn trong trm x l nc thi phi tnh theo lu lng ln nht trong 1 giy nhn vi h s 1,4. Ngoi cc cng trnh cng ngh chnh, tu theo cng sut ca trm v iu kin a phng cn xy dng cc cng trnh ph tr v phc v (tham kho ph lc IV). Khu vc trm x l nc thi phi c hng ro bo v, phi c hon thin v chiu sng. Tu theo iu kin a phng c th c bin php chng xi l b ta luy do ma. Trong trng hp cn thit tu theo mc yu cu ca k thut an ton m c hng ro cho tng cng trnh ring bit. Song chn rc

7.18 7.19

7.20

7.21 7.22

Trong thnh phn cc cng trnh x l nc thi phi c song chn rc, chiu rng khe h ca song chn rc bng 15 - 20mm. S lng v kch thc song chn rc, tc nc chy qua khe h, lng rc ly ra t song chn, khong cch gia cc thit b v.v... theo qui nh iu 6.14 v 6.15. Khi khi lng rc ln trn 0,1 m3/ngy nn c gii ho khu ly rc v nghin rc. Nu lng rc nh hn 0,1 m3/ngy th s dng song chn rc th cng. Rc c nghin nh cho php vo trc song chn rc hoc a v b mtan. Ct sn ca nh t song chn rc phi cao hn mc nc cao nht trong mng dn t nht 0,5m. Tn tht p lc qua song chn rc xc nh theo cng thc i vi song chn rc cn sch ri tng ln vi h s 3. c th thay th khi cn thit, trc v sau song chn rc phi c ca phai v phi c thit b x cn nc cho mng dn.Ghi ch: - Nu dng song chn rc th cng th ch cn lm sn cc khe phai s dng khi cn thit. - Rc vt ln c cha trong thng c np y v chuyn ch n ni x l cht thi rn .. - Rc hu c nghin cng a vo x l cng vi bn cn bn hu c ca trm x l nc thi.

7.23 7.24 7.25 7.26 7.27

7.28

lp rp v sa cha song chn rc my nghin rc v cc thit b khc cn c cc thit b nng chuyn theo qui nh iu 6.18.



TCXDVN-51:2008

7.29

Trong nh t song chn rc nn kt hp b tr my bm ct ca b lng ct. B lng ct

7.30

i vi cc trm x l nc thi cng sut trn 100 m3/ngy cn c b lng ct. La chn loi b lng ct cn da vo cng sut trm, s cng ngh x l nc thi v bn cn. S b hoc s n nguyn lm vic ng thi ca b lng ct khng nh hn 2, khi co ct bng my th phi c b d phng. Tnh ton b lng ct ngang v b lng ct c thi kh theo cc cng thc: 1. Din tch tit din t W (m2): W= Trong :Q V n

7.31 7.32

(7-2)

Q - Lu lng ln nht ca nc thi (m3/s) n - S b hoc s n nguyn V - Vn tc ca nc trong b (m/s) L=K 1000 H n .V U0

2. Chiu di cng tc ca b L (m): (7-3)

Trong : t U0 v U - ln thu lc ca ht (mm/s), xc nh bng tc lng do ca ht ct trng thi tnh v trng thi ng trong b theo bng 7-5. K- H s t l U0 : U chn theo bng 7-6. Hn - Chiu cao tnh ton ca b lng ct. i vi b lng ct thi kh chn bng na chiu cao tng cng ca b. V - Vn tc chuyn ng ca nc thi trong b, mm/s, c chn theo bng 7-7. Bng 7-5..ng knh ht ct (mm) ln thu lc U0 (mm/s) 0,1 5,12 0,12 7,27 0,15 11,2 0,2 17,1 0,25 24,2 0,3 29,7 0,35 35,1 0,40 40,7 0,50 51,6

Bng 7-6.ng knh nh nht ca ht ct cn gi li, (mm) ln thu lc ca ht, U0 (mm/s) Gi tr K tu thuc loi b lng ct v t l B:H ca b lng ct thi kh B lng ct ngang 0,15 0,20 0,25http://www.nuoc.com.vn

13,2 18,7 24,2

1,7 1,3

B lng ct thi kh B:H=1 B:H = B:H = 1,5 1,25 2,62 2,5 2,39 2,43 2,25 2,08 -


TCXDVN-51:2008

Bng 7-7.Loi b lng ct ln thu lc ca ht ct U0 (mm/s ) 18,7-24,2 13,2-18,7 18,7-24,2 Vn tc nc (mm/s) khi lu lng Min Max 0,15 0,3 0,08-0,12 Chiu su Lng ct H (m) gi li (l/ng.ng) 0,5 - 2 0,7 - 3,5 0,5 0,02 0,03 0,02 N m ca ct (%) 60 60 T l ct trong cn (%) 55 - 60 90 - 95 70 - 75

Ngang Thi kh Tip tuyn

Chn kch thc ti thiu ca ht cn gi li trong b tu thuc loi cng trnh x l sau n. i vi cc b lng m cn c x l b mtan hoc b lng hai v, kch thc ht ct ti thiu phi gi li l 0,2 - 0,25 mm. to tc u trong b, li vo b phi xy dng theo kiu knh m rng, li ra theo kiu thu hp v chiu di tng ng . 7.33 Khi thit k b lng ct cn theo cc qui nh sau: a) B lng ct ngang - Vn tc dng chy trong b khi lu lng ln nht l 0,3 m/s; khi lu lng nh nht l 0,15 m/s - ln thu lc ca ct gi li trong b U 0 ly bng 18 n 24 mm/s - Thi gian lng ct khng nh hn 30 s khi lu lng ln nht - Chiu su tnh ton H n bng 0,25 n 1m b) B lng ct c thi kh - ln thu lc ca ht ct U 0 ly 18mm/s, - Cng thi kh 3 - 5 m3/m2 gi, - dc ngang ca y b (v pha mng thu) 0,2 - 04 - Ca a nc vo b phi trng vi chiu quay ca nc trong b v ca a nc ra phi t ngp. - Tng chiu su ca b H ly 0,2 - 3,5 m, - Dn phn phi kh lm bng ng c l, ng knh l 3,5 mm t su 0,7H, - Tc chy khi lu lng ln nht V bng 0,08 - 0,12 m/s, - T l gia chiu rng v chiu su ca b B : H ly 1: 1,5. c. i vi b lng ct kiu tip tuyn: - Chn ti trng b mt q bng 110 m3/m2.h ng vi lu lng ln nht ca nc thi, - Dn nc vo theo kiu tip tuyn, - Chiu su bng na ng knh, - ng knh b khng qu 6 m. Bng 7-8 l cc s liu kch thc nh hnh ca b lng ct ngang nc chuyn ng vng.



TCXDVN-51:2008

Bng 7-8.Lu lng tnh ton ca 1 b ( l/s) 25 - 200 300 ng knh (m) 4 6 Chiu rng mng lng (m) 0,6 - 0,9 1,6 Tng chiu cao mng lng (m) 0,44 - 0,78 1,75 Tng chiu di mng lng (m) 9 13,8

7.34

Lng ct gi li trong b lng ct ph thuc iu kin v sinh mi trng khu vc th, tnh trng lm vic ca mng li thot nc v hiu qu hot ng ca b lng ct. Khi thiu cc s liu thc nghim th c th tnh ton s b lng ct gi li theo cc ch tiu sau y: - i vi h thng thot nc ring hon ton, lng ct gi li l 0,02 l/ngi/ngy; - i vi h thng thot nc chung, l 0,04 l/ngi/ngy; - N ca ct 60%, khi lng ring khong 1,5 T/m3. m Ct x ra khi b lng c th bng: - Phng php th cng khi lng ct ti 0,1 m3/ngy; - Phng php c gii, phng php nng thy lc hay bm v sau vn chuyn bng chuyn khi lng ct trn 0,1 m3/ngy. Lu lng nc k thut qh (l/s) khi x ct bng thit b nng thy lc c xc nh theo cng thc: Trong : qh = vh lscbsc (7-4)

-vh -Vn tc hng ln ca dng nc ra trong mng, chn bng 0,0065 m/s; -lsc - Chiu di y b lng ct, khng k phn h tp trung ct; bsc - Chiu rng ca y di ca b lng ct, chn bng 0,5 m. S b c th ly lng nc k thut bng 20 ln lng ct ly ra khi b 7.35 7.36 Th tch h tp trung ct khng ln hn th tch ct lng c trong 2 ngy, gc nghing ca y thu ct khng nh hn 600 so vi phng nm ngang. n nh vn tc dng chy trong b lng ct ngang, pha cui b cn c p trn nh rng khng.Tnh ton p trn theo cng thc sau: - chnh ct gia y b lng ct v ngng trn (m) P= Trong : Kq - T s ca lu lng ln nht v nh nht (K= qmax:q min ); hmax,v hmin - Chiu su nc trong b ng vi qmaxv q min v vn tc chy V = 0,3 m/s. -Chiu rng p trn b0 (m)http://www.nuoc.com.vn2 hmax K q / 3 hmin 2 Kq /3 1

(7-5)


TCXDVN-51:2008

b0 = Trong :

q max m 2 g ( p + hmax ) 3 / 2

(7-6)

m - H s lu lng ca p trn ph thuc vo iu kin co hp dng chy, ly bng 0,35 - 0,8 7.37 lm kh ct t b lng ct, cn c sn phi ct hay h cha ct. Xung quanh sn phi ct phi c b p cao 1 - 2 m. Kch thc sn phi ct c xc nh vi iu kin l: tng chiu cao lp ct h chn bng 3 - 5 m3/m2.nm. Ct kh thng xuyn c chuyn i ni khc. Nc tch t ct c a v u trm x l Nc thi. B iu ho 7.38 B iu ha dng iu ho lu lng v nng cht bN trong nc thi n sn xut v nc thi th. Th tch b xc nh theo biu lu lng v biu dao ng nng cht bN trong nc thi. nGhi ch: Nu khng c biu thi nc th cho php xc nh th tch b theo lu lng nc thi ca mt ca sn xut.

7.39

Khi t b iu ho trc b lng th phi c thit b chng lng cn trong b. Chn b iu ha (khuy trn bng khng kh nn, bng thit b khuy trn c kh hay b nhiu hnh lang) da trn c s c im dao ng nng cc cht bN (theo chu k, hn lon hay x nc tp trung) cng nh c im v n nng cc cht l lng.

7.40

Trong cc b vi khuy trn bng khng kh nn hay bng c kh, nu nc thi c cha cc cht c hi d bay hi th phi c bin php che y kn v phi c bin php thng hi. S dng b iu ha khuy trn bng khng kh nn iu ha nng nc thi khi nng cht l lng di 500 mg/l vi ln thy lc 10 mm/s . - Th tch b iu ha khi x tp trung nc thi c tnh ton theo cc cng thc sau:Wdh = 1,3qW t Z K yc ln K yc 1

7.41

khi Kyc di 5

(7-7)

Wh = 1,3 qW .ttt Trong :

khi Kyc bng v trn 5

(7-8)

qW - Lu lng nc thi, m3/h ttt - Thi gian x vi lu lng nc thi tp trung , h Kyc - H s iu ha yu cu v bng :K yc = C max CTB CTB C max

(7-9)

Trong :http://www.nuoc.com.vn


TCXDVN-51:2008

Cmax - Nng ln nht ca cht bN khi x tp trung, mg/l n CTB - Nng trung bnh ca cht bN trong nc thi, mg/l n Ccp - Nng cho php ca cht bN sau khi iu ha, ph thuc vo n iu kin hot ng ca cng trnh pha sau, mg/l. 7.42 Th tch b iu ha Wh (m3), khi nng dao ng theo chu k, c xc nh theo cng thc: khi Kyc < 5 (7Wh = 0,21 qt. tck K yc - 1 Wh = 1,3 qt. tck Kyc khi Kyc >= 5 (7-11)

10) Trong : tck Chu k dao ng nng , h. Kyc - H s iu ha yu cu, xc nh theo cng thc (7-9) Khi nng dao ng bt k, th tch b s tnh theo phng php tim cn gn ng. 7.43 Vic phn phi nc thi theo b mt b iu ha sc kh phi m bo ng u. C th dng ng phn phi c l hay mng trn tit din ch V, ch U phn phi. Vn tc dng nc trong mng khng di 0,4 m/s. H thng sc kh ca b iu ha nh sau : - Thit b sc kh : l cc ng c l khoan ng knh l d = 5mm cch nhau 3 - 6 cm, nm mt di ng. ng phi t tuyt i theo phng ngang, dc theo tng dc ca b trn cc gi cao 6 - 10 cm so vi y. - Nu t thit b sc kh ch mt pha v st thnh b th khong cch t thit b ti thnh b i din ly bng 1 n 1,5 H. - ng knh ca thit b sc kh ly bng 50 mm nu cng sc kh nh hn 8m3/h cho 1m di v bng 75mm nu cng sc kh ln hn. B iu ha khuy trn c kh c s dng iu ha vi hm lng cht l lng trn 500 mg/l vi ch nc vo b bt k. Th tch b iu ha khuy trn c kh cng c tnh ton tng t nh b iu ha sc kh. Dung tch b iu ha kiu nhiu hnh lang khi x nc thi tp trung c xc nh theo cng thc :Wdh = qt t tt K yc2

7.44

7.45

7.46

(7-12)

Trong :

qt - lu lng nc thi (m3/h), ttt - khong thi gian x nc thi tp trung, (h), Kyc - h s iu ha yu cu.

7.47

Cu to b iu ha lu lng tng t nh b lng t mt hay b cha thng thng v phi c h tp trung cn v thit b x cn. C th dng my bm bm nc thi sang cng trnh x l nc thi tip theo vo cc gi c lu lng min. Tnh ton th tch b iu ha lu lng tng t nh b cha hay i nc trong h thng cp nc. Chn gi tr ca cc h s khng iu ha sau khi iu ha Kh , th tch b iu ha Wh xc nh theo cc mi quan h sau y :

7.48



TCXDVN-51:2008

yh = Kh / Kh0 h = Wh/ qTB Trong : Khy0 - H s khng iu ha ca nc thi chy vo b, qTB - Lu lng gi trung bnh ca nc thi, S ph thuc gia yh v h c xc nh theo bng 7-9. Bng 7-9. yh h 7.491 0 0,95 0,24 0,9 0,5 0,85 0,9 0,8 1,5 0,75 2,15 0,67 3,3

( 7-13) ( 7-14)

0,65 4,4

Khi cn iu ha c lu lng v nng nc thi th th tch b iu ha lu lng v nng cht bN c tnh ton theo tng bc mt. n S gia ca th tch nc W, m3 v nng C, g/m3, sau mt bc tnh ton c xc nh theo cng thc: W = (qvo qra) t C = [ (Cvo Cra )t]/Wh Trong : qvo, C vo, Cra- Lu lng, nng cht bN trong nc thi thi n im sau mt bc tnh ton. Wh -Th tch nc trong b iu ha tng ng vi thi im tnh ( 7-15) (7-16)

ton.

B lng 7.50 La chn loi b lng phi da theo cng sut, tnh cht nc thi, cc iu kin t nhin v cc iu kin c th khc ca a phng. Ni chung c th s b la chn kiu b lng theo cng sut ca trm x l nc thi nh sau: B lng ng: Di 20.000m3/ngy B lng ngang: trn 15.000m3/ngy B lng ly tm: trn 20.000m3/ngy B lng 2 v v cc loi b lng kt hp ln men bn cn thng p dng cho trm x l nc thi cng sut nh hoc trung bnh, di 10.000 m3/ngy. S b lng khng t hn 2 v tt c cc b phi lm vic ng thi. Tnh ton cc b lng (tr b lng t hai sau cc cng trnh x l sinh hc) da trn c s nghin cu ng hc lng ca cc cn ht l lng c tnh ti hiu qu lng cn thit. Khi x nc thi sau b lng vo sng, h th hm lng cn l lng cn li trong nc thi phi m bo cc iu kin v sinh khi x nc thi vo ngun tip nhn" theo cc tiu chuN mi trng lin quan. n Tnh ton b lng theo cc cng thc sau:

7.51 7.52

7.53



TCXDVN-51:2008

a) Kch thc b: Chiu di b lng ngang l (m) l=V .H K .U 0

(7-17)

Bn knh b lng ng, b lng ly tm R (m) R=Q 3,6K .U 0

(7-18)

Trong : Q - Lu lng tnh ton ca nc thi (m3/h); H - Chiu su tnh ton ca vng lng (k t mt trn ca lp trung ho ti mt thong ca b) ( m), theo ch dn iu 7.58; V - Vn tc tnh ton trung bnh trong vng lng, trong b lng ly tm l tc ti tit din im gia tnh t tm ra bin bn knh (mm/s). i vi b lng ngang v b lng ly tm V ly 5 - 10 mm/s; K - H s ph thuc loi b lng v cu to ca thit b phn phi v thu nc, qui nh nh sau: - 0,5 i vi cc b lng ngang, - 0,45 i vi cc b lng ly tm, - 0,35 i vi b lng ng, U0 - ln thu lc ca ht cn (mm/s) b) ln thu lc U0 (mm/s) xc nh theo cc ng cong ng hc lng hoc theo cng thc sau y: U0 =1000.K .H KH .t h n

(7-19)

Trong : - H s k ti nh hng ca nhit ca nc i vi nht ly theo bng 7-10 - Thnh phn thng ng ca tc ca nc thi trong b ly theo bng 7-11 . t - Thi gian lng (s) ca nc thi trong bnh th nghim hnh tr vi chiu su lp nc h, t hiu qu lng bng hiu qu lng tnh ton; khi thiu s liu thc nghim th t ly theo bng 7-12 ( i vi mt s loi ht nht nh); n- H s kt t, ph thuc vo tnh cht l lng ca cc loi ht ch yu, xc nh bng thc nghim ph thuc vo tnh cht ca cn trong nc thi. Khi thiu s liu thc nghim c th ly s b nh sau: - n ly 0,25 i vi ht l lng c kh nng kt t trong nc thi sinh hot, - n ly 0,4 i vi cc ht khong rn c khi lng ring 2 - 3 g/ cm3; - n ly 0,5 cho cc ht cn nng c khi lng ring 5 - 6 g/ cm3. Tr s KH khi tnh ton cc b lng t mt i vi nc thi sinh hot c th h n

ly theo bng 7-13 .http://www.nuoc.com.vn


TCXDVN-51:2008

Bng 7-10 .Nhit trung bnh tnh theo thng thp nht tnh bng C H s 60 0,45 50 0,55 40 0,66 30 0,8 25 0,9 20 1 15 1,44 10 1,3

Bng 7-11V (mm/s) 5 0 10 0,05 15 0,1 20 0,5

(mm/s)

Bng 7-12Hiu Thi gian lng trong hnh tr c chiu su h = 500mm (s) n = 0,25 n = 0,4 qu lng Nng (mg/l) E (%) 100 200 300 500 500 1000 2000 3000 20 600 300 150 140 100 40 30 900 540 300 180 180 1200 120 50 40 1320 650 450 390 200 180 150 60 50 1900 900 640 450 240 200 180 80 60 3800 1200 970 680 280 240 200 100 70 3600 2600 1830 360 280 230 130 80 5260 1920 690 570 370 90 2230 1470 1080 100 3600 1850 n = 0,6 200 75 120 180 390 3000 300 60 90 120 180 580 400 45 80 75 130 380 -

Ghi ch: 1. Thi gian lng ng vi nhit 200C 2. i vi cc gi tr trung gian ca hm lng cn v hiu qu lng so vi cc gi tr trong bng, thi gian lng xc nh bng phng php ni suy. 3. ng hc lng ca cc cht l lng trong nc thi v h s kt t phi xc nh trong iu kin lng tnh trong bnh th nghim hnh tr c ng knh khng nh hn 120 mm.

Bng 7-13Chiu cao cng tc b lng H 1,0 1,5 2,0 3,0 4,0 5,0http://www.nuoc.com.vn

KH Tr s cho b lng cc kiu h B lng ng B lng ly tm B lng ngang 1,08 1,1 1,11 1,16 1,19 1,21 1,29 1,32 1,29 1,35 1,41 1,46 1,5

n


TCXDVN-51:2008

- Sau khi xc nh L v R th kim tra tc thc t Vth(mm/s) trong phn lng. - i vi b lng ngang: Vth = Trong : B Chiu rng b lng ly trong khong 2 5 H. - i vi b lng ly tm (ti tit din gia bn knh) Vth =Q 3,6RH Q 3,6 HB

(7-20)

(7-21)

Trng hp tr s ca Vth v V khc nhau cn iu chnh li gi tr ca L v R. 7.54 Khi lng cn lng x ra khi b xc nh ph thuc vo hiu qu lng tnh ton. N cn lng ca nc thi sinh hot khong 95% i vi tt c cc loi b m lng t mt khi x cn bng t chy; khong 93,5 94% khi x cn bng bm pistng N cn lng ca nc thi sn xut ly theo ti liu thc nghim. m B lng t hai sau b lc sinh hc c tnh ton theo ti trng thy lc b mt q0 (m3/m2/h) nh sau: qo = 3,6 KSuo Trong : ton uo - ln thy lc ca mng sinh hc. khi x l sinh hc hon uo = 1,4mm/s; KS - H s s dng dung tch, chn theo iu 7.56. Khi xc nh th tch cc b lng phi tnh n lu lng bn tun hon. 7.56 Tt c cc loi b lng t hai sau aeroten u tnh theo ti trng thy lc q0 (m3/m2.h), c tnh ti nng bn hot tnh trong b aeroten a (g/l), ch s bn I (cm3/g) v nng bn phn nc trong at, (mg/l) theo cng thc:4,5 K s H 0,8 (0,1Ia) 0,50, 01at

7.55

(7-22)

q0 =

(7-23)

Trong ,: KS - H s s dng dung tch ca vng lng, chn bng 0,4 i vi b lng li tm, 0,35 i vi b lng ng, 0,45 i vi b lng ng vi x nc t chu vi, 0,4 i vi b lng ngang; a- Nng bn hot tnh trong b aeroten chn khng qu 15 g/l at-Nng bn hot tnh phn nc trong chn khng di 10 mg/l.



TCXDVN-51:2008

7.57

Thi gian lng v vn tc dng chy ln nht tnh ton b lng t hai ly theo bng 7-14. Bng 7-14Cc s liu tnh ton b lng t hai Thi gian lng (h) Vn tc dng chy khi lu lng ln nht ln nht (mm/s) Loi b lng Lng ngang, ly Lng ngang, Lng tm, ng ly tm ng 0,73 1,5 0,75 1 2 5 5 7 5 5 0,5 0,5 0,7 0,5 0,5

Cng dng ca b

Cc b lng ln II a) Sau b lc sinh hc nh git b) Sau blc sinh hc cao ti c) Sau Aeroten lm sch khng hon ton - Khi gim BOD n 20% - Khi gim BOD n 80% d) Sau Aeroten lm sch hon ton

Ghi ch: Ni chung s liu tnh ton b lng t hai sau cc Aeroten phi trn c s thc nghim, ph thuc ch lm vic ca Aeroten.

7.58

Hm lng cht l lng trong nc thi sau b lng t hai i vi nc thi sinh hot ly theo bng 7-15, i vi nc thi sn xut ly theo s liu thc nghim. Bng 7-15.

Hm lng cht l lng trong nc thi sinh hot t b lng t hai (mg/l) Thi gian khi BOD ca nc thi c lm sch (mg/l) bng lng (h) 15 20 25 50 75 100 0,75 21 27 33 66 86 100 1 18 24 29 58 80 93 1,5 15 20 25 51 70 83 2 12 16 21 45 63 75

7.59

x bn cn nc thi sinh hot khi b lng t mt c th dng bm pistng hoc bng p lc thu tnh khng nh hn 1,5 m ct nc. i vi b lng t hai p lc thu tnh khng nh hn 1,2 m i vi cc b lng sau b lc sinh hc nh git hoc cao ti; khng nh hn 0,9m i vi cc b lng sau Aeroten. i vi b lng t mt v b lng t hai sau b lc sinh hc, th tch ngn cha bn cn nn ly bng khi lng bn cn lng khng qu hai ngy, i vi b lng t hai sau Aeroten khng qu 2 gi. Khi x bn cn bng c gii, th tch ngn cha bn ca cc b lng ln I nn ly bng khi lng cn lng trong 8 gi. ng knh ng dn bn ra khi b lng t mt v t hai xc nh theo tnh ton nhng khng nh hn 200 mm. Chiu cao thnh b lng tnh t mc nc tr ln bng 0,3m. Kt cu b lng t mt phi c b phn thu v tch cht ni.



TCXDVN-51:2008

Mng trn thu nc lng trong cc b lng c th lm theo dng phng hoc dng rng ca; ti trng thu lc ca mng khng c qu 10 l/s.m. 7.60 Khi thit k b lng cn tun th cc quy nh sau y: a) B lng ngang: + Chiu su tnh ton ca vng lng H ly 1,5 3m, ph thuc vo cng sut ca cc cng trnh x l nc thi, trong mt s trng hp c th ly n 4m. + T l gia chiu di v chiu su ca b ly 8 12, trong mt s trng hp c th ly 8 20 (i vi nc thi sn xut). + Nc thi vo v ra khi b phi phn phi theo chiu rng b. + Gc nghing ca thnh h thu cn khng nh hn 500. + Phi c thit b x cn b. + dc ca y b khng nh hn 0,005. + Chiu cao lp nc trung ho cao hn y b 0,3m ( cui b). + Chiu cao lp bn ca b lng ln II ly 0,2 0,5m. b) B lng ly tm. + Chiu su vng lng H ly 1,5 5m. T l gia ng knh b v chiu su vng lng ly 6 12 trong mt s trng hp c th ly t 6 30 ( i vi nc thi xut). + ng knh b khng nh hn 1 m. + Chiu cao lp nc trung ho 0,3 m. + Chiu su lp bn trong b lng t hai ly 0,3 0,5m. i vi cc b lng t hai c my ht bn dc y b 0,01 0,03, nhng khi c thit b co bn th dc y b l 0,01. c) B lng ng: + ng knh b D ly = 4 9m + Chiu su tnh ton ca vng lng H ly 2,7 - 3,8 m; i vi b lng t hai, H khng c nh hn 1,5m. + ng trung tm c chiu di bng chiu cao tnh ton ca vng lng, c ming phu v tm ht c nh pha di. + ng knh v chiu cao ca phu ly bng 1,5 ng knh ng trung tm. ng knh tm ht bng 1,3 ng knh ming phu. Gc nghing gia b mt tm ht vi mt phng ngang: 170. Chiu cao t mt di ca tm ht n b mt lp cn l 0,3m. + Vn tc nc trong ng trung tm khng ln hn 30 mm/s; vn tc nc qua khe h gia mp di ca ng trung tm v b mt tm ht b lng ln mt khng ln hn 20 mm/s, b lng t hai ly 15 mm/s. + Mng thu nc lng t trong thnh trong ca b lng. + Gc nghing ca b lng t mt v t hai so vi phng ngang khng nh hn 500. B lng hai v 7.61 7.62 B lng hai v c th l b n hoc b kp. i vi cc b kp phi bo m kh nng thay i thng xuyn hng dng chy trong mng lng. B lng hai v thit k theo cc quy nh nu trong iu 7.50, 7.53 v 7.58, ng thi theo cc quy nh sau y: - Mt thong t do ca b cn ni ln khng nh hn 20% din tch mt bng ca b.



TCXDVN-51:2008

- Khong cch gia thnh ngoi ca cc mng lng khng nh hn 0,5 m. - Gc nghing ca thnh mng lng khng nh hn 500, hai thnh nghing ca mng lng phi trm ln nhau t nht 0,15m, chiu su mng lng ph thuc chiu di ly t 1,2 2,5 m. Chiu rng khe h ca mng lng ly 0,15m. - Chiu cao lp nc trung ho ly t khe h ca mng lng n b mt lp cn trong ngn t hoi l 0,5m. - Gc nghing phn y hnh nn ca ngn t hoi khng c nh hn 300. - N ca cn ly ra khi b 90%. m - Hiu qu lng cht l lng ca b 45 50%. - Hiu qu phn hy cht hu c 40%. 7.63 Th tch ngn t hoi ca b lng hai v c th xc nh cc s liu nu trong bng 7-16 . Bng 7-16.Nhit nc thi trung bnh vo ma ng 10 12 15 20 25 Th tch ngn t hoi trong b lng 2 v tnh bng lt cho 1 ngi 65 50 30 15 10

Ghi ch: 1. Th tch ngn t hoi ca b lng hai v cn phi tng thm 75% nu a bn ca b Aeroten x l hon ton hoc b lc sinh hc cao ti vo, hoc phi tng 30% khi x bn ca b lng sau b lc sinh hc nh git, hoc ca Aeroten x l khng hon ton vo. 2. Khi thiu s liu v thc nghim nhit nc thi th c th ly nhit trung bnh hng nm ca khng kh tnh ton. 3. Th tch ngn t hoi ca b lng 2 v x l nc thi trc khi a vo bi lc cho php gim khng qu 20%.

Thit b thu du 7.64 B thu du c s dng gi li cc ht du th khi nng du ln hn 100mg/l. Tnh ton b thu du hon ton ging nh tnh ton b lng ngang, c ch thm v ng hc ni ca cc loi ht du. Nu khng c cc s liu v ng hc ni ca cc ht du cho php ly: - ln thu lc (tc ni ca ht du) t 0,4 0,6 mm/s. - Vn tc tnh ton trung bnh trong phn nc chy ca b V l 4 6mm/s. Khi lng cc ht du b gi trong trng hp ny vo khong: - 70% khi cc ht du c ln thu lc bng 0,4 mm/s; - 60% khi cc ht du c ln thu lc bng 0,6 mm/s. Khi thit k b thu du nn ly: - Chiu su phn nc chy ca b H ly 2m; - T s gia chiu di v chiu su l 15 20; - Chiu rng ca mt ngn l 3 6m;

7.65



TCXDVN-51:2008

- S ngn ly khng t hn 2; - Lp du ni dy 0,1m; - Lp cn dy n 0,1m; - N ca cn mi lng 95%, khi lng ring 1,1 T/m3; m - N ca cn lng vn cc 70%. Khi lng ring 1,5 T/m3 ; m - Khi lng cn b gi li tnh theo cht kh 80 120 g/m3 nc thi. Cn c cc thit b thu v thit b x cc vng du ni. Siclon thu lc 7.66 Siclon thu lc h c p dng tch cn lng v cc tp cht ni c cu trc thuc h khuych tn th. Siclon thu lc kn (c p lc) dng tch cc hp cht c cu trc ht n nh h khuych tn th. C th p dng 3 loi siclon thu lc sau y: a) Siclon thu lc khng c thit b bn trong, dng tch cc tp cht thuc h phn tn nh v th c ln thu lc t 5 mm/s tr ln. b) Siclon thu lc c mng ngn v vch hnh tr dng khi lu lng ca mi b n 200m3/h, dng x l cc cht thuc h phn tn th v nh vi ln thu lc t 0,2 mm/s tr ln cng nh cc cht l lng kt ta v cc sn phN du m. m c) Siclon thu lc nhiu tng dng khi lu lng mi b ln hn 300m3/h, dng tch cc tp cht khng vn cc thuc h phn tn th v nh vi ln thu lc 0,2mm/s tr ln cng nh cc sn phN du m. m Khi thit k cc siclon thu lc cn ch : - Ly cn bng cc gu mc, thit b nng thu lc hoc bng p lc thu tnh. - Dng tm chn hnh khuyn na chm na ni t trc p trn vi khong cch khng qu 50mm gi li cc tp cht ni. - Tch cc cht ni bng phu t ngc trong nc. Khi thit k cc siclon thu lc nn ly: a) i vi tt c cc siclon thu lc h ti trng thu lc q(m3/m2.gi) xc nh theo cng thc: q = 3,6K.U0 Trong : K H s ph thuc loi siclon. U0 - th thu lc ca ht cn b gi li (mm/s) Tn tht p lc trong siclon thu lc ly bng 0,5m. b) i vi cc siclon thu lc khng c thit b bn trong. - H s K ly 0,61. Chiu cao phn hnh tr H bng ng knh ca siclon. - ng knh vi x ly bng 0,10m. - Gc nghing ca thnh phn hnh nn ly bng 600. c) i vi cc siclon thu lc c mng ngn v vch ngn hnh tr. - H s K ly bng 1,98. - ng knh phn h

tcxdvn 51 2008

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