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BI GING MN X L NC THI Ging vin: Nguyn Th Hng

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1. Chng 1: NGUN GC, TNH CHT NC THI

1.1. Khi qut v NT 1.1.1. Nc thi

1.1.2. X l nc thi

1.1.3. Cp nc tun hon, ti s dng nc

1.1.4. Qu trnh t lm sch

1.2. Ngun gc pht sinh 1.2.1. Nc thi sinh hot

NTSH l nc c dng cho cc mc ch n ung, sinh hot, tm ra, v sinh nh

ca,... ca cc khu dn c, cng trnh cng cng, c s dch v,...Nh vy, NTSH 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, bp n,.. cng to ra cc loi NT c thnh phn v tnh cht tng

t nh NTSH.

Lng NTSH ti cc c s dch v, cng trnh cng cng ph thuc vo loi cng trnh,

chc nng, s lng ngi.

Lng NT t cc c s thng mi v dch v cng c th c chn t 15- 25% tng

lng NT ca ton thnh ph.

c trng NTSH l: hm lng cht hu c cao (55-65% tng lng cht bn), cha

nhiu vi sinh vt c c vi sinh vt gy bnh, vi khun phn hy cht hu c cn thit cho cc

qu trnh chuyn ha cht bn trong NT.

NTH giu cht hu c, cht dinh dng, l ngun gc cc loi vi khun (c vi

khun gy bnh) pht trin l mt trong nhng ngun gy nhim chnh i vi mi trng

nc.

NTH c thnh phn ging nhau cc th nhng khc v hm lng, phng php

x l ging nhau v x l sinh hc c u tin la chn.

Lu lng NT khng iu ha, ph thuc vo thi im trong ngy (Vd: lng ngi

trong khu th,...). S lng ngi cng ng ch thi cng iu ha. Nc thi cng

nghip

Trong cc x nghip cng nghip thng to thnh 3 loi NT:

+Nc c s dng nh nguyn liu sn xut, gii nhit, lm sch bi v khi thi,...

+Nc c s dng v sinh cng nghip, nhu cu tm ra, n ca ca cng nhn,...

+Nc ma chy trn

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Nhu cu v cp nc v lng nc thi sn xut ph thuc vo: loi hnh, cng ngh

sn xut, loi v thnh phn nguyn vt liu, cng sut nh my,...Cng ngh sn xut nh ln

n lng nc tiu th, lng nc thi to thnh, ch x thi v thnh phn tnh cht

nc thi. p dng cng ngh tin tin v trang thit b cng hin i, lng nc s dng s

gim rt nhiu.

Bng : Nhu cu cp nc v lng nc thi mt s ngnh cng nghip

Ngnh cng nghip n v tnh Nhu cu cp nc Lng NT

Sn xut bia L.nc/ l.bia 10-20 6-12

Cng nghip ng m3 nc/tn ng 30-60 10-50

Cng nghip giy m3 nc/tn giy 300-550 250-450

Dt nhum m3 nc/tn vi 400-600 380-580

Nc thi trong cc nh my, x nghip c chia lm 2 nhm: nhm NT sn xut

khng bn (quy nc sch) v nc bn.

NT sn xut khng bn: ch yu to ra khi lm ngui thit b, gii nhit trong cc trm

lm lnh, ngng t hi nc,...

NT sn xut bn: c th cha nhiu loi tp cht vi nng khc nhau (v c, hu c,

hoc hn hp). Thnh phn, tnh cht NT rt a dng v phc tp. Mt s NT cha cc cht

c hi nh kim loi nng (Vd: NT xi m), cha nhiu vi khun gy bnh,.....

NTCN ph thuc vo qu trnh sn xut, quy trnh cng ngh. XLNT cng nghip kh

khn hn, mc nhim phc tp hn so vi NTSH.

Tnh ton lng NT ti a: da trn cng sut ca nh my v h thng XLNT s khng

b qu ti.

NT sn xut cha nhiu cht bn khc nhau v c s lng ln thnh phn do khng

th c tiu chun v cc ch tiu, thnh phn ha l cho mt loi NT no c.

1.3. Cc ch tiu nhim c trng trong NTT 1.3.1. Cc cht rn trong NT

NT l h a phn tn bao gm nc v cc cht bn. Cc nguyn t ch yu c trong

thnh phn ca NTSH l C, H, O, N vi cng thc trung bnh C12H26O6N. Cc cht bn trong

NT gm c v c v hu c, tn ti di dng cn lng, cc cht rn khng lng c l cc

cht ha tan v dng keo.

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Bng : Khi lng cht bn c trong NTSH, g/ngi. ngy

Thnh phn Cn lng Cht rn khng lng Cht ha tan TC

Hu c 30 10 50 90

V c 10 5 75 90

Tng cng 40 15 125 180

Tng cht rn l thnh phn vt l c trng ca NT. Cc cht rn khng ho tan c hai

dng: cht rn keo v cht rn l lng. Cht rn l lng (SS) c gi li trn giy lc kch

thc l 1,2 micromet (bao gm cht rn l lng lng c v cht rn l lng khng lng

c).

1.3.2. Cc hp cht hu c trong nc thi

Trong nc thin nhin v NT tn ti nhiu tp cht hu c ngun gc t nhin hay

nhn to: protein, hp cht hu c cha nit, cc loi ph gia thc phm,....cht thi ca ngi

v ng vt,....

Cc hp cht hu c c th tn ti di cc dng ha tan, keo, khng tan, bay hi,

khng bay hi, d phn hy, kh khng hy,...Phn ln cc cht hu c trong nc ng vai

tr l c cht i vi vi sinh vt. N tham gia vo qu trnh dinh dng v to nng lng cho

vi sinh vt.

Xc nh ring r tng loi cht hu c l rt kh v tn km, v vy ngi ta thng

xc nh tng cc cht hu c. Cc thng s thng c chn l: TOC, DOC, COD; BOD

Trong NTT v mt s loi NTCN, cc cht hu c ch yu l cacbon hydrat (CHO)

Vic xc nh ring bit cc thnh phn hu c ring bit l kh khn, ngi ta thng xc

nh tng cc cht hu c thng qua ch tiu COD, BOD.

Thng gi tr COD nh hn nhiu gi tr BOD do khng phi bt k cht no oxy ha

cng chuyn thnh CO2.

Nhu cu oxy ha sinh ha BOD l lng oxy yu cu vi khun oxy ha cc cht hu

c c trong NT. Trong thi gian 5 ngy u vi 20oC cc vi khun hiu kh s dng oxy

oxy ha cc cht hu c CBOD, sau trong iu kin d oxy cc loi vi khun nitrit, nitrat

bt u hot ng oxy ha cc hp phn nit thnh nitrit v nitrat NBOD

Gia i lng COD, BOD c mi quan h vi nhau v lin h theo mt t l ph thuc

vo loi NT, nc ngun v c trong qu trnh x l. Thng COD Cr2O72-:BOD20:CODMnO4-:BOD5= 0,95:0,71:0,65:0,48.

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1.3.3. bn sinh hc ca NT

NT c cha nhiu vi sinh vt trong c nhiu vi sinh vt gy hi, cc loi trng giun.

Ngi ta xc nh s tn ti ca 1 loi vi khun c bit : trc khun coli nh gi bn

sinh hc ca NT.

-Chun s coli: th tch NT t nht (ml) c 1 coli. i vi NTSH chun s ny: 1.10-7.

-Tng s Coliform: s lng vi khun dng coli trong 100 ml nc (tnh bng cch m

trc tip s lng coli hoc xc nh bng phng php MPN).

1.4. Q.trnh nitrt ha v kh nitrt. Q.trnh ha tan v tiu th oxy trong NT 1.4.1. Qu trnh nitrt ha v kh nitrt

Trong nc thin nhin v NT, cc hp cht ca nit tn ti di 3 dng: cc hp cht

hu c, amoni, cc hpc ht dng oxy ha (nitrit, nitrat).

Cc hp cht nit l cc cht dinh dng, lun vn ng trong t nhin ch yu nh cc

qu trnh sinh ha.

Trong NT SH, nit tn ti di dng v c (65%) v hu c (35%). Ngun nit ch yu

l nc tiu, khong 1,2 lt/ngi/ngy, tng ng 12 g nit trong nit amoni N-

CO(NH2)2 l 0,7 gam cn li l cc loi nit khc. Ure thng c amoni ha theo phng

trnh sau:

+Trong mng li thot nc ure b thy phn: CO(NH2)2+ 2H2O= (NH4)2CO3

+Sau b thi ra ra: (NH4)2CO3= 2NH3 + CO2 + H2O

Nitrit l sn phm trung gian ca qu trnh oxy ha amoniac hoc nit amoni trong iu

kin hiu kh nh cc loi vi khun Nitrosomonas. Sau nitrit hnh thnh tip tc c vi

khun Nitrobacter oxy ha thnh nitrat.

NH4+ +1,5O2 Nitrosomonas NO2- + H2O + 2H+

NO2- + 0,5O2 Nitrobacter NO3-

Nitrit l hp cht khng bn, n c th l sn phm ca qu trnh kh nitrat trong iu

kin ym kh.

Nitorat l dng hp cht v c ca nit c ha tr cao nht.

Nitorat ha l giai on cui cng ca qu trnh khong ha cc cht hu c cha nit.

Nitorat trong NT chng t s hon thin ca cng trnh XLNT bng phng php sinh hc.

Mt khc, qu trnh nitorat ha cn to nn s tch ly oxy trong hp cht nit cho cc qu

trnh oxy ha sinh ha cc cht hu c tip theo, khi lng oxy ha tan trong nc rt t hoc

b ht.

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Khi thiu oxy v tn ti nitrat ha s xy ra qu trnh ngc li: tch oxy khi nitrat

v nitrit s dng li trong cc qu trnh oxy ha cc cht hu c khc. Qu trnh ny c

thc hin nh cc vi khun phn nitrat ha (vi khun ym kh ty tin). Trong iu kin

khng c oxy t do m mi trng vn cn cht hu c cacbon, mt s loi vi khun kh

nitrat hoc nitrit ly oxy cho qu trnh oxy ha cc cht hu c.

1.4.2. Qa trnh ha tan v tiu th oxy trong NT

1.4.2.1. Qu trnh khong ha cc cht hu c trong NT

Cht hu c trong NT l mi trng cho cc loi vi khun pht trin. XLNT T c

nhim v l: tch cc cht bn hu c, cc cht dinh dng v kh trng nc thi.

Qu trnh khong ha cht hu c nh oxy ha sinh ha xy ra theo 2 giai on:

+oxy ha cc hp cht cha C thnh CO2 v nc

+oxy ha cc hp cht cha N thnh nitrit v sau thnh nitrat

Qa trnh khong ha cc hp cht trong iu kin hiu kh thc t l qu trnh tiu th

oxy ha tan t kh quyn vo nc thi.

1.4.2.2. Qa trnh tiu th oxy v ha tan oxy trong NT

Khi c oxy trong NT, tc oxy ha cht hu c cha C t l thun vi khi lng

cht hu c c trong NT.

1.5. S dng NT v bn cn trong NT 1.5.1. S dng NT v bn cn trong NT ti cy v lm phn bn

1.5.2. S dng NT nui trng thy sn v nui c (trang 26;H)

1.5.3. Dng li NT sau khi x l trong h thng cp nc tun hon ca nh my x nghip

1.5.4. Dng li nc cho qu trnh sau trong SX

1.5.5. Thu hi cht qu

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2. Chng 2: PHNG PHP X L C HC

2.1. Song chn rc hoc li chn rc Loi b tt c cc tp vt c th gy s c trong qu trnh vn hnh h thng XLNT

nh tc ng bm, ng ng hoc ng dn

Trong XLNT th ngi ta dng song chn lc nc v dng my nghin nh cc

vt b gi li, cn trong XLNT cng nghip ngi ta t thm li chn.

SCR c phn loi theo cch vt rc:

+SCR vt rc th cng, dng cho trm x l c cng sut nh di 0,1 m3/ngy

+SCR vt rc c gii bng cc bng co dng cho trm c c.sut ln hn 0,1 m3/ngy

Rc c vt 2-3ln trong ngy v c nghin a v b bn hoc x trc tip

pha trc thit b.

2.2. B iu ha Dng duy tr s n nh ca dng thi, khc phc nhng vn vn hnh do s dao

ng ca lu lng dng nc thi gy ra v nng cao hiu sut ca cc qu trnh cui dy

chuyn x l.

Li ch:

-Lm tng hiu qu ca h thng sinh hc do n hn ch hin tng qu ti ca h

thng v lu lng cng nh hm lng cc cht hu c, gim c din tch xy cc b sinh

hc (do c tnh ton chnh xc hn). Hn na cc cht c ch qu trnh x l sinh hc s

c pha long hoc trung ha mc thch hp cho cc hot ng ca vi sinh vt.

-Cht lng NT sau x l v vic c c bn y b lng th cp c ci thin do

lu lng np cht rn n nh.

-Din tch b mt cn cho h thng lc nc gim xung v hiu sut lc c ci

thin, chu k lm sch b mt cc thit b lc cng n nh hn.

2.3. B lng ct Trong XLNT, qu trnh lng c s dng loi cc tp cht dng huyn ph th ra

khi nc thi. Theo chc nng, cc b lng c phn thnh: b lng ct , b lng s cp, b

lng th cp.Yu cu: c hiu sut lng cao v x bn d dng.

Cng c th s dng b lng nh cng trnh x l cui cng, nu iu kin v sinh ni

cho php.

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+B lng s cp: t trc cng trnh x l sinh hc dng gi li cc cht hu c

khng tan trong NT trc khi cho NT vo cc b x l sinh hc v loi b cc cht rn c kh

nng lng (t trng ln hn t trng ca nc) v cc cht ni (t trng b hn t trng nc).

Nu thit k chnh xc b lng s cp c th loi b 50 -70% cht rn l lng, 25 - 40% BOD

ca NT.

+B lng th cp: t sau cng trnh x l sinh hc.

-Cn c vo chiu nc chy phn bit cc loi: b lng ngang, ng, radian

2.4. Lc Lc c ng dng tch cc tp cht phn tn c kch thc nh khi nc thi m

cc b lng khng th loi chng c, l qu trnh tch cc ht rn ra khi pha lng hoc pha

kh bng cch cho dng kh hoc lng c cha ht cht rn chy qua lp ngn xp, cc ht rn

s b gi li. Lc c th xy ra di tc dng ca p sut thy tnh ca ct cht lng hoc p

sut cao trc vch ngn hay p sut thp sau vch ngn.

-Vt liu:

+Dng vch: lm bng thp tm c c l hoc bng li thp khng r nhm, niken,

ng,.. v c cc loi vi khc nhau (thy tinh, amiang, bng len, si,..).Yu cu: tr lc nh,

bn v ha hc, do c hc, khng b trng n v bi ph hy iu kin lc cho trc.

+B lc vi lp vt liu dng ht: c th l ct thch anh, than cc, si nghin, than nu,

than g,...ty thuc vo loi NT v iu kin kinh t. c tnh quan trng ca vt liu lc l:

xp v b mt ring. xp ph thuc vo cu trc, kch thc cc ht xp, cch sp t

cc ht xp. B mt ring ca lp vt liu xp c xc nh bng xp ca cc ht v hnh

dng ca chng.

Qu trnh lc gm cc giai on sau: 1.di chuyn cc ht ti b mt cc cht to thnh

lp lc. 2.gn cht cc ht vo b mt. 3.tch cc ht bm dnh ra khi b mt.

+Lc qua mng lp b c to thnh trn b mt vt liu lc: cc ht c kch thc

ln hn kch thc mao qun lp vt liu lc b gi li, to thnh lp b v cng tr thnh nh

lp vt liu lc. (c trng cho b lc chm).

+Lc khng to thnh lp mng cc tp cht: qu trnh lc xy ra trong b mt lp

vt liu lc dy, cc ht tp cht b gi li trn cc ht ca vt liu lc bng lc bm dnh. i

lng bm dnh ph thuc vo cc yu t: ln, hnh dng ht, nhm b mt, thnh phn

ha hc, tc dng chy, nhit cht lng,...

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Khi s ht ti b mt lp lc trong mt n v thi gian bng s ht ri khi b mt ,

s bo ha xy ra v lp lc khng cn kh nng lc na.

2.5. ng t v keo t Qu trnh lng ch c th tch c cc ht rn huyn ph nhng khng th tch c

cc cht gy nhim bn dng keo v ha tan v chng l nhng ht rn c kch thc qu

nh.

tch cc ht rn mt cch hiu qu bng phng php lng cn tng kch thc

ca chng nh s tc ng tng h gia cc ht phn tn lin kt thnh tp hp cc ht nhm

lm tng vn tc lng.

Kh cc ht keo rn bng trng lng cn theo 2 bc: 1. trung ha in tch ca

chng. 2. lin kt chng li vi nhau. Qu trnh trung ha in tch: qu trnh ng t. Qu

trnh lin kt to thnh cc bng ln hn: qu trnh keo t.

Cc cht ng t thng dng: cc mui nhm, st hoc hn hp ca chng. Vic la

chn ph thuc vo: tnh cht ha l, chi ph, nng tp cht trong nc, pH, thnh phn

mui trong nc. Hay dng: Al2(SO4)3.18H2O, NaAlO2, NH4Al(SO4)2.12H2O,

KAl(SO4)2.12H2O, FeCl3, Fe2(SO4)3.2H2O trong Al2(SO4)3 c dng nhiu hn v d ha

tan trong nc.

Al2(SO4)3 + 3Ca(HCO3)2 Al(OH)3 + 3CaSO4 + 6CO2

i vi cc mui st cng hay dng:

FeCl3 + 3 H2O Fe(OH)3 + HCl

V n nhiu u im hn so vi cc mui nhm do: tc dng tt hn nhit thp, c

khong pH ti u ca mi trng rng hn, bn ln v kch thc bng keo c khong gii

hn rng ca thnh phn mui, c th kh c mi v khi c H2S. Nhc im: to cc phc

ha tan nhum mu qua phn ng ca cc cation st vi mt s hp cht hu c.

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3. Chng 3: XLNT BNG PHNG PHP SINH HC TRONG CC CNG TRNH NHN TO

3.1. Gii thiu chung Phng php da trn c s : hot ng ca vi sinh vt phn hy cc cht hu c

gy nhim bn trong NT. Cc vi sinh vt s dng cc cht hu c v mt s cht khong lm

cht dinh dng v to nng lng. Chng nhn cc cht dinh dng xy dng t bo, sinh

trng, sinh sn nn sinh khi ca chng tng ln. Qu trnh phn hy cc cht hu c nh vi

sinh vt gi l qu trnh oxy ha sinh ha.

NT c x l bng phng php sinh hc s c c trng bng ch tiu COD v

BOD.

T lm sch: do trong mi trng c cc vi khun gip cho qu trnh chuyn ha, phn

hy cht hu c nn khi XLNT cn xem xt NT c cc vi sinh vt hay khng li dng s c

mt ca n v nu c th to iu kin tt nht cho cc vi sinh vt pht trin.

Phn loi:

+Phng php hiu kh:

+Phng php k kh

3.2. Nguyn l chung ca qu trnh oxy ha sinh ha thc hin qu trnh oxy ha sinh ha, cc cht hu c ha tan, cc cht keo phn tn

nh trong NT cn c di chuyn vo bn trong t bo ca vi sinh vt. Qu trnh ny gm 3

giai on:

1.Di chuyn cc cht gy nhim t pha lng ti b mt ca t bo vi sinh vt do

khuch tn i lu v phn t.

2.Di chuyn cht t b mt ngoi t bo qua mng bn thm bng khuch tn do s

chnh lch nng cc cht trong v ngoi t bo.

3.Qu trnh chuyn ha cc cht trong t bo vi sinh vt vi s sn sinh nng lng v

qu trnh tng hp cc cht mi ca t bo vi s hp th nng lng.

Ba giai on ny c quan h cht ch vi nhau v qu trnh 3 ng vai tr quan trng

trong XLNT. Nng cc cht xung quanh t bo s gim dn. Cc phn thc n mi t mi

trng bn ngoi ( NT) li khuch tn trong mi trng chm hn qu trnh hp th thng qua

mng t bo cho nn nng cc cht dinh dng xung quanh t bo bao gi cng thp. i

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vi cc sn phm do t bo tit ra th ngc li li cao hn so vi ni xa t bo. Mc d hp

th v hp ph l giai on cn thit trong vic tiu th cht hu c ca vi sinh vt song khng

phi c ngha quyt nh trong vic XLNT. ng vai tr ch yu quyt nh l cc qu trnh

din ra bn trong t bo vi sinh vt (giai on 3).

Cc qu trnh sinh ha:

+QT hiu kh: cht hu c + O2 vsv CO2, H2O

+QT k kh: cht hu c + O2 vsv CH4, H2S, NH3, CO2 , H2O(c mi, hm

lng ph thuc vo cht hu c) (coi oxy trong cc lin kt nh NO3-, SO42-,) (ngoi cc

kh ny cn c 1 t cht hu c khng phn hy gi l cht tr ).

3.3. nh hng ca cc yu t khc nhau ln tc oxy ha sinh ha 3.3.1. Cc quy nh i vi NT

3.3.1.1. nh hng ca nhit

3.3.1.2. Hm lng cn l lng

3.3.1.3. Hm lng oxy ha tan

3.3.1.4. nh hng ca kim loi nng

3.3.1.5. Cc nguyn t dinh dng v vi lng

3.3.1.6. Gi tr pH

3.3.1.7. Nng cc mui ha tan

3.3.2. Cc iu kin cng ngh

-Tip xc tt gia nc thi v vi khun trong tp hp cc bng bn hot tnh, mng

sinh vt hoc lp bn l lng.

-Trong iu kin x l sinh hc hiu kh, oxy lun c duy tr v m bo cc qu

trnh oxy ha sinh hc cc cht hu c din ra. Hm lng oxy ha tan trong b bn hot tnh

thng duy tr mc 4 mg/l. Hm lng oxy ha tan trong NT sau b lng t 2 khng nh

hn 2 mg/l.

-Qu trnh khuy trn bn vi NT hoc thi kh qua b lc sinh hc khng c ph v

cu trc bn hot tnh hoc mng sinh vt.

-Thi gian lu ca nc thi v bn hot tnh trong h thng cc cng trnh x l phi

hp th cc cht hu c v oxy ha cc cht hu c.

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3.4. Cc phng php ym kh 3.4.1. C ch phn hy k kh cc cht hu c trong iu kin ym kh

Trong iu kin khng c oxy, cc cht hu c c th b phn hy nh vi sinh vt v

sn phm cui cng l CH4, CO2. Qu trnh chuyn ha cht hu c nh vi khun k kh ch

yu din ra theo nguyn l ln men qua cc bc sau:

Bc 1:Thy phn cc cht hu c phc tp v cc cht bo thnh cc cht hu c n

gin hn nh monosacarit, amino axit hoc cc mui khc. y l ngun dinh dng v nng

lng cho vi khun hot ng.

Bc 2:Cc nhm vi khun k kh thc hin qu trnh ln men axit, chuyn ha cc cht

hu c n gin thnh cc loi axit hu c thng thng nh axit axetic, glixerin, axetat,...

CH3CH2COOH + 2H2O CH3COOH + CO2 + 3H2

Axit prifionic

CH3CH2 CH2COOH + 2H2O 2 CH3COOH + 2H2

Axit butinic

Bc 3:Cc nhm vi khun k kh bt buc ln men kim (ch yu l cc loi vi khun

ln men metan nh methanosarcina v methanothrix) chuyn ha axit axetic v hydro thnh

CH4, CO2.

3.4.2. Cc loi cng trnh XLNT trong iu kin ym kh

-Cc loi b lng NT kt hp ln men bn cn lng: Trong cc cng trnh ny din ra

qu trnh lng cn NT (X l s b hoc x l bc mt) v ln men bn cn lng, l cc

cng trnh: b t hoi, b lng 2 v, b lng trong kt hp vi ngn ln men ng c ng

dng XLNT SH v cc loi NT khc c thnh phn tng t.

-B phn ng ym kh tip xc: NT cha c x l c trn u vi bn ym kh

tun hon theo s

-B lc ym kh: B ny c lp t cc gi th vi sinh vt k kh dnh bm l cc loi vt

liu hnh dng, kch thc khc nhau, ng vai tr nh vt liu lc. Dng nc thi c th i t

di ln hoc trn xung. Cc cht hu c c vi khun hp th v chuyn ha to thnh

CH4 v cc cht kh khc. Cc kh sinh hc c thu gom ti phn trn b.

-B phn ng ym kh c dng NT i qua tng cn l lng

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3.5. Cc phng php hiu kh 3.5.1. C ch phn hy cht hu c trong iu kin hiu kh

Cc qu trnh hiu kh c th xy ra trong iu kin t nhin hay trong cc iu kin x

l nhn to. Trong iu kin x l nhn to ngi ta to ra cc iu kin ti u cho qu trnh

oxy ha sinh ha nn qu trnh x l c tc cao v hiu sut cao hn.

Qu trnh chuyn ha vt cht:

+Qa trnh oxy ha cht hu c :(p ng nhu cu nng lng ca t bo)

CxHyOzN + O2 vsv CO2 + NH3 + H2O + Q (1)

+Qa trnh tng hp t bo:(tng hp xy dng t bo)

CxHyOz + NH3 + O2 vsv C5H7NO2 + CO2 + H2O + Q (2)

(C5H7NO2: Cng thc theo t l trung bnh cc nguyn t chnh trong t bo vi sinh

vt)

+Qa trnh oxy ha ni bo (t oxy ha): nu tip tc tin hnh QT oxy ha th khi

khng cht dinh dng, Qa trnh chuyn ha cc cht ca t bo bt u xy ra qa trnh

t oxy ha:

C5H7NO2 + O2 vsv CO2 + NH3 +H2O + Q (3)

Trong qu trnh oxy ha sinh ha hiu kh, cc cht hu c cha N, S, P cng c

chuyn thnh NO3-, SO42-, PO43-, CO2, H2O.

NH3 + O2 vsv HNO2 + O2 +vsv HNO3 (4)

v (2): lng oxy tiu tn cho cc phn ng ny l tng BOD ca NT.

(1), (2), (3), (4): lng oxy tiu tn gn gp 2 ln lng oxy cho 2 phn ng u.

Khi mi trng cn ngun C hu c, cc loi vi khun nitrt ha (nitrosomonas) v

nitrat ha (nitrobater) thc hin qu trnh nitrat ha theo 2 giai on:

55NH4+ + 76O2 + 5CO2 nitrosomonas C5H7NO2 + 54NO2- + 52H2O + 109 H+

400 NO2- + 19 O2 + NH3 + 2 H2O + 5CO2 nitrobater C5H7NO2 + 400 NO3-

3.5.2. Cc cng trnh nhn to (XLNT theo nguyn tc lc-dnh bm, XLNT bng bn hot

tnh)

3.5.2.1. Lc sinh hc

-C ch XLNT theo nguyn tc lc-dnh bm:

+Sau mt thi gian, mng sinh vt c hnh thnh v chia thnh 2 lp: lp ngoi

cng l lp hiu kh c oxy khuch tn xm nhp, lp trong l lp thiu oxy (anoxic). B

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dy mng sinh vt t 600-1000 micromet trong phn ln l vng hiu kh. Do qu trnh

lc sinh hc thng c xem nh l qu trnh hiu kh nhng thc cht l h thng vi sinh vt

hiu-ym kh.

+Thnh phn: vi khun (ch yu), dng vt nguyn sinh, nm, x khun,Sau

mt thi gian hot ng, mng sinh vt dy ln, cc cht kh tch t pha trong tng ln v

mng b bc khi VLL. Hm lng cn l lng trong nc tng ln. S hnh thnh cc lp

mng sinh vt mi li tip din.

+Cc cng trnh XLNT theo nguyn tc ny chia lm 2 loi: loi c VLL tip xc

khng ngp trong nc vi ch d ti theo chu k v loi c VLL tip xc ngp trong nc

giu oxy.

-B lc sinh hc nh git:

-B lc sinh hc cao ti:

-a lc sinh hc:

-B lc sinh hc c VLL ngp trong nc (b bioten):

3.5.2.2. XLNT bng bn hot tnh

Cc vi sinh vt thng tn ti trng thi huyn ph. B c sc kh m bo yu

cu oxy v duy tr bn hot tnh trng thi l lng. Huyn ph lng ca cc vi sinh vt trong

b thng kh c gi chung l cht lng hn hp v sinh khi (MLSS)

Khi NT i vo b thi kh (b aeroten), cc bng bn hot tnh c hnh thnh m ht

nhn ca n l cc phn t cn l lng.

Cc loi vi khun hiu kh n c tr, pht trin dn cng vi cc ng vt nguyn sinh,

nm, x khun, to nn cc bng bn mu nu sm, c kh nng hp th cc cht hu c ha

tan, keo v khng ha tan phn tn nh.

Vi khun v vi sinh vt sng dng cht hu c v cht ding dng (N, P) lam thc n

chuyn ha chng thnh cc cht tr khng ha tan v thnh t bo mi.

Dn n trong b aeroten lng bn hot tnh tng dn ln, sau c tch ra ti b

lng t 2, mt phn c quay tr li u b aeroten tham gia x l NT theo chu trnh mi

Qu trnh c tip din n khi cht thi cui cng khng th l thc n ca cc vi sinh vt c

na.

Nu trong NT m c cht hu c kh phn hy, cn c thi gian chuyn ha th

phn bn hot tnh tun hon phi c tch ring v sc kh oxy cho chng tiu ha thc n

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hp th. Qu trnh ny gi l ti sinh bn hot tnh.Nh vy qu trnh XLNT bng bn HT

bao gm cc giai on sau:

+Khuy trn to iu kin tip xc NT vi bn HT

+Cung cp oxy vi khun v vi sinh vt oxy ha cht hu c

+Tch bn HT ra khi NT

+Ti sinh bn HT tun hon v a chng v b aeroten

Yu cu chung v vn hnh:

+Cc b aeroten phi m bo b mt tip xc ln gia khng kh, NT v bn.

+Khng kh c cp vo NT bng: nn kh qua b phn khuch tn ngp trong nc

bng sc kh hoc dng khuy c hc thi vo cht lng bng thng kh c hc.

+NT a vo DO 2mg/l, SS150mg/l (i vi hm lng sn phm du m th

25mg/l), pH 6,5-9, nhit 6-30oC, c t: GHCP, khong ha tan: y , BOD (cht hu c

d b phn hy), nng cc cht dinh dng khc: m bo.

Phn loi b aeroten:

+Theo ch thy ng lc c: b aeroten y, khuy trn, trung gian

+Theo phng php ti sinh bn hot tnh: loi c ti sinh tch ring, loi khng c ti

sinh tch ring

+Theo ti lng bn: loi ti trng cao, trung bnh, thp

+Theo s bc: 1 bc, 2 bc, nhiu bc

+Theo chiu dn NT vo: xui chiu, ngc chiu

3.6. Cc cng trnh loi b cc cht dinh dng (mui nit v phtpho) v n nh bn bng phng php sinh hc 3.6.1. C ch qu trnh

3.6.1.1. Cc qu trnh loi b cht dinh dng nit

gim nguy c ph dng trong sng h do x nc thi, cn thit phi gim mui

nit v pht pho trong . N c th tn ti nhiu dng khc nhau trong NT. Loi b N ngha

l chuyn nv dng kh bay ln.

-i vi qu trnh XLNT bng sinh hc hiu kh th

55NH4+ +76O2 +5CO2 nitrosomonas C5H7NO2+54NO2-+52H2O+109 H+

400NO2- + 10 O2 + NH3 + 2H2O + 5CO2 nitrobacter C5H7NO2+ 400NO3-

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-Trng hp thiu oxy, cc loi vi khun kh nitrat denitrificans (dng k kh ty tin)

s tch oxy ca nitrat v nitrit oxy ha cht hu c. Nit phn t to thnh trong qu trnh

ny s thot ra khi nc. Qu trnh chuyn

NO3- NO2- NO N2O N2 (NO, N2O, N2: dng kh)

Nhng cng i hi c ngun C tng hp t bo.

-Do NT c nitrit ha thng cha t vt cht cha C nn i hi phi b sung

thm ngun C t ngoi vo. Trong mt s h kh nitrit sinh hc, NT chy ti hoc t bo cht

thng l ngun cung cp C cn thit. Khi XLNT cng nghip thng thiu C hu c nn

ngi ta thng dung CH3OH ru metylic lm ngun C b sung. NT cng nghip nu ngho

cht dinh dng nhng li cha C hu c th cng c th ha trn vo.

Nh vy cng trnh XLNT cn:

+iu kin ym kh (thiu oxy t do)

+c nitrat v nitrit

+c vi khun k kh ty tin kh nitrat

+c ngun C hu c

+nhit NT khng thp.

u im:

+Kh c nit trong NT dng ra

+Hiu sut kh BOD tng do cc cht hu c tip tc b oxy ha trong qu trnh kh

nitrat.

+Gim c lng bn d trong b lng t hai.

+Lm tng kh nng lng v hn ch trng ca bn HT

+Lm tng pH ca NT sau x l

3.6.1.2. Qu trnh loi b cht dinh dng pht pho

-P xut hin trong NT dng PO43- hoc poli photphat P2O7 hoc dng photpho lin kt

hu c. Hai dng sau chim khong 70% trong NT.

-Cc dng tn ti ca P thng dng cc loi hp cht keo t gc Fe, Al, loi b

nhng gi thnh t, to thnh bn cha tp cht ha hc,

-Vi khun Acinetobater l 1 trong nhng sinh vt u tin c trch nhim kh P, chng

c kh nng tch ly poliphotphat trong sinh khi tng i cao (2-5%).

Kh nng ly P ca vi khun k kh ty tin Acinebacter s tng ln rt nhiu khi cho

n lun chuyn cc iu kin hiu kh, k kh.

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3.6.1.3. Qu trnh thi kh ko di trong aeroten

-u im: (XLNT c quy m va, nh)

+C th gim 85-95% BOD v cn l lng trong NT

+ 1 phn cht hu c d gy thi ra trong bn c kh nh qu trnh h hp

ni bo

+ Hiu qu lm sch cao, lng bn d t nhng din tch cng trnh ln

3.6.2. Mt s cng trnh

3.6.2.1. Knh oxy ha tun hon

-p dng: dng cho vng c 200 -15000 ngi.

3.6.2.2. Aeroten hot ng gin on theo m(Sequencing Batch Reactor-SBR)

+1.Nc thi cho vo b c trn vi BHT (c lu li trong chu k trc)

+2.Hn hp NT v bn c suc kh bc ny vi thi gian ng yu cu. Cc cht

hu c c oxy ha hon ton giai on ny.

+3.Qu trnh lng bn trong iu kin tnh

+4.Sau lng, nc nm pha trn lp bn c x ra khi b

+5.X lng bn d c hnh thnh trong qu trnh thi kh ra khi ngn b, cc ngn

c hot ng lch pha m bo cho vic cung cp NT n trm XLNT lin tc.

-u im:

+Hiu qu xl Nt cao

+BOD NT sau XL < 20 mg/l, CLL 3-25 mg/l; N-NH3 0,3-12 mg/l

+Khng cn b lng t 2, trong nhiu trng hp c th b qua b iu ha, b

lng t 1

+C th loi b c N, P do c th iu chnh c qu trnh hiu kh, thiu kh, k

kh trong b bng vic thay i ch cung cp oxy.

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4. Chng 4: XLNT BNG PHNG PHP SINH HC TRONG IU KIN T NHIN

4.1. Cc cng trnh XLNT trong t 4.1.1. C ch ca qu trnh

4.1.2. Yu cu i vi cc phng php XLNT trong t ngp nc

-t d thm nc, kh nng hp ph cao, mc nc ngm di 1,5m, dc mt t

nh hn hoc bng nh hn hoc bng 0,02 i vi cnh ng ti v nh hn 0,08 i vi

cnh ng lc (khng trng trt).

-Trng cc loi cy c kh nng cc cht hu c cng nh cc mui c cha N, P, K

trong NT.

-NT khi a vo cnh ng ngp nc thng phi p ng: pH 6,5- 8,5; cn l lng <

150 mg/l; BOD5< 150 mg/l, tng mui khng ha tan

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+Khi a cc cng trnh XLNT trong t vo hot ng cn phi kim tra cc thng s

v mc nc ngm, thm nc ca t, ti trng cht bn, cn chn cc loi cy ph hp,

kim tra h thng ti, h thng thu gom NT v c bin php thot nc trong trng hp

ngp cc b trn h thng cnh ng ngp nc pha di.

+Cc thng s cn quan trc trong qu trnh vn hnh l: BOD, tng N, tng P, E.coli,

s lng nc XL, cc loi thc vt bc cao , h ng vt t, nng sut cy trng,

+cc loi rui mui, cn trng gy bnh pht trin nhiu nn c bin php tiu dit hoc

hn ch s pht trin ca n phng nh hng xu n sc khe con ngi.

4.2. H sinh hc 4.2.1. C ch ca qu trnh XLNT trong h sinh hc

H sinh hc l cc thy vc t nhin hay nhn to, khng ln m s din ra qu

trnh chuyn ha cac cht bn. Qu trnh ny tng t nh qu trnh t lm sch trong cc h

t nhin vi vai tr ch yu l cc loi vi khun v to.

Khi vo h, do vn tc dng chy nh, cc loi cn lng xung y. Cc cht hu c

cn li trong NT s b cc vi sinh vt hp th v oxy ha m sn phm to ra l sinh khi ca

n, CO2, cc mui nitorat, nitrit,...Kh CO2, cc hp cht nit, phtpho c rong to s dng

trong qu trnh quang hp, gii phng oxy cung cp cho qu trnh oxy ha cc cht hu c ca

vi khun. S hot ng ca rong to gip ch cho qu trnh trao i cht ca vi khun. Trng

hp NT m c cht hu c, to c th chuyn t t dng sang d dng, tham gia vo qu

trnh oxy ha cht hu c. Nm, x khun cng thc hin cc qu trnh ny.

Cc hp cht nit, photpho, cacbon,...trong h sinh hc cng c chuyn ha theo chu

trnh ring vi s tham gia ca vi khun, to v cc thc vt bc cao khc.

u im: s dng ao h t nhin nn chi ph u t xy dng thp, vn hnh n gin,

c hiu qu x l, kh trng, c th kt hp nui c, trng to. H sinh hc n nh ph hp

vi cc vng kh hu nhit i v cc khu dn c va v nh.

Nhc im: cn din tch ln, kh iu khin qu trnh x l, nc h thng c mi

kh chu i vi cc khu vc xung quanh. Khc phc: lm thong nhn to cung cp oxy cho

h bng cc bin php cng bc (kh nn, khuy c hc,...) nh m cc vng cht trong h

gim, iu kin tip xc gia cht hu c-oxy-vi khun tng ln nn hiu qu x l NT c

m bo.

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4.2.2. Phn loi h sinh hc

4.2.2.1. H sinh hc n nh nc thi

4.2.2.2. H lm thong nhn to

H SH lm thong hiu kh: h c xo trn gn nh hon ton, khng c hin tng

lng cn, hot ng gn ging b aeroten.

H SH lm thong tu tin: cn c nhng vng lng cn v phn hy cht bn trong

iu kin ym kh, mc xo trn NT trong h hn ch.

u im: din tch xy b nh so vi HSH n nh, trong h ny nng BHT nh hn

nhiu (200 400 mg/l) so vi aeroten (2000 6000 mg/l), hiu qu XL c khi n 90% khi

thi gian lu nc t 2 6 ngy. p dng: XL NT sinh hot v NT sn xut. i vi khu dn

c, h c s dng khi HSH ty tin hot ng qu ti hoc din tch t thiu. i vi cc

nh my x nghip, h c dng nh 1 cng trnh x l s b NT trc khi x ra h thng

thot nc chung.

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5. Chng 5: XLNT BNG PHNG PHP HA HC V HA L

5.1. Phng php ng t Mc ch: tng nhanh qu trnh lng cc cht l lng phn tn nh, keo,... ngi ta

dng phng php ng t, khi nng cht mu, mi, l lng s gim xung.

Cc cht ng t thng dng l nhm sunfat, st sunfat, st clorua,...

Al2(SO4)3 khi vo nc s tc dng vi bicacbonat trong nc to thnh Al(OH)3 dng

bng v s hp ph , kt dnh cc ht huyn ph, cc cht dng keo llng trong NT. Cc

bng ny s lng xung y dng cn.

Al2(SO4)3 + 3Ca(HCO3)2 2Al(OH)3 + 3CaSO4 + CO2

Khi dng cc mui st:

2FeCl3 + 3Ca(OH)2 3CaCl2 + 2Fe(OH)3

Hiu sut ng t cao nht khi pH 4-8,5. to cc bng ln, d lng ngi ta dng

thm cht tr ng. l cht cao phn t tan trong nc v d phn ly thnh ion, gm cht

tr ng t loi anion v cation. Hay dng l poliacrylamit (CH2CHCONH2)n , natri silicat

hot tnh,...

Gii hn s dng: chn la ha cht, liu lng ti u, th t cho vo nc, lng cn

to thnh,... phi c tin hnh bng thc nghim, thng dng 1-5mg/l.

iu kin: phn ng din ra hon ton v tit kim, cn phi: khuy u c th s

dng cc loi my trn khc nhau. Loi hay dng: cnh qut c gii th NT s chuyn ng

vng v to bng d dng ton b th tch.

5.2. Phng php trung ha NT sn xut trong nhiu lnh vc c cha nhiu axit hoc kim ngn nga hin

tng xm thc cc cng trnh thot nc v trnh cho cc qu trnh sinh ha cc cng

trnh lm sch v trong h, sng khng b ph hoi, ngi ta phi trung ha cc loi NT .

Trung ha cn vi mc ch lm cho mt s mui kim loi nng lng xung v tch ra khi

nc.

Cng ngh u tin: tnh n kh nng trung ha ln nhau gia cc loi NT cha axit v

kim.

Qu trnh trung ha c thc hin trong cc b trung ha kiu lm vic lin tc hay

gin on theo chu k. NT sau khi trung ha c th cho lng cc h lng tp trung v nu

iu kin thun li, cc h ny c th tch c th tr c cn lng trong khong 10-15 nm.

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Th tch cn lng ph thuc vo nng axit, ion kim loi nng trong NT, vo dng v

liu lng ha cht, vo mc lng trong,...V d: khi trung ha NT bng vi sa ch bin t

vi th trng cha 50% CaO hot tnh s to nhiu cn nht.

Vic la chn bin php trung ha ph thuc vo lng NT, ch x thi, nng ,

ha cht c a phng.

i vi NT sn xut, vic trung ha bng ha cht kh kh khn v thnh phn v lu

lng NT trong cc trm trung ha dao ng rt ln trong ngy m. Ngoi vic cn thit phi

xy dng b iu ha vi th tch ln cn phi c thit b t ng iu chnh lng ha cht

vo. Thng s chnh iu chnh ph bin l i lng pH. Trong thc t cn phi tin hnh

thc nghim vi tng loi NT tin hnh bin php trung ha v trong NT ny cha nhiu

hp cht hu c, axit, mui phn ly yu c nh hng n vic o pH bng in ha hc.

5.2.1. Trung ha bng cch trn NT cha axit v NT cha kim

Phng php ny c dng khi NT ca x nghip l axit cn x nghip gn c NT

kim. C hai loi NT ny u khng cha cc cu t gy nhim khc.

5.2.2. Trung ha NT bng cch cho thm ha cht

Nu NT cha qu nhiu axit hay kim ti mc khng th trung ha bng cch trn ln

chng vi nhau c th phi cho thm ha cht.

Phng php ny thng trung ha axit.

Ha cht s dng: ph liu cng nghip a phng

trung ha axit v c c th dng bt k dung dch c tnh baz no. Ha cht r tin

v d kim l Ca(OH)2, CaCO3, MgCO3, lmit, cn NaOH v xa Na2CO3 ch c dng

khi chng l ph liu.

Liu lng ha cht c xc nh theo iu kin trung ha hon ton axit t do v ly

ln hn tnh ton mt cht.

Vic a dung dch cng tc vo NT c tin hnh nh bm hoc cc thit b nh

lng (kiu phao, nh mc vi p lc c nh,)

5.2.3. Trung ha NT cha axit bng cch lc qua nhng lp vt liu trung ha

S dng cho NT cha HCl, HNO3, H2SO4 vi hm lng di 5g/l v khng cha mui

kim loi nng.

Cch tin hnh: cho NT tip xc cc b vt liu lc l vi, magiezit, hoa cng,

lmit, kch thc ht 3-8 cm vi tc ph thuc vo vt liu nhng khng qu 5m3/h v

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thi gian tip xc khng qu 10 pht, nc thi c th chuyn ng ngang hoc ng trong b

lc.

5.2.4. Dng kh thi, khi t l hi trung ha NT cha kim

y l bin php kh kinh t trung ha NT cha kim v kh t ng khi chy tt

thng cha khong 14% CO2.

5.3. Phng php oxy ha kh Cc cht bn trong NT cng nghip c th phn ra hai loi: v c v hu c.

Cc cht hu c thng l m, m, ng, cc hp cht cha phenol, cha nit,... nn

c th b phn hy vi sinh vt, do c th dng phng php sinh hc x l.

Cc cht v c thng l nhng cht khng x l bng phng php sinh hc c.

Cc ion kim loi nng khng th XL bng VSV cng nh khng loi c di dng cn, ch

1 phn b hp ph bng BHT. Thy ngn, asen,... cn l nhng cht rt c kh XL m cn

tiu dit cc VSV c li trong NT.

5.3.1. XLNT cha xianua bng phng php oxy ha kh

Vic la chn bin php XLNT ph thuc vo tnh cht l ha ca NT. Cch thc

thng dng l oxy ha xianua chuyn sang dng xianat, feri, fero, cc cn kt ta t nhng

xianua n gin, phc cht ri sau tch khi nc thi bng phng php lng hoc lc.

Cn u tin la chn bin php oxy ha xianua c thnh xianat khng c v y l

bin php tt nht. y, nhm CN- b phn hy hon ton v nc s khng nhim bn tr

li bi cc cht xianua.

Mt s cc cht hay dng:

1) Dng hypoclorit:

+ oxy ha xianua n gin, tan c: CN- + OCl- CNO- + Cl-

+ oxy ha xianua phc hp, tan, c

2) Dng clo lng trong mi trng kim:

+ oxy ha xianua n gin, tan c: CN- + Cl2 + 2OH- CNO- + Cl-+ H2O

+ oxy ha xianua phc hp, tan c:

3) Dng permanganat:

+ oxy ha xianua n gin, tan c:

+ oxy ha xianua phc hp, tan c:

Lu :- qu trnh oxy ha l nh oxi nguyn t mi sinh, khng phi l O2 nn nu lm

thong th xianua khng th b oxy ha c m ch mt phn b thi i m thi.

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5.3.2. XLNT cha crom bng phng php oxy ha kh

-Nguyn tc: chuyn Cr6+ s bin v Cr3+, tip tch dng hidroxit kt ta.

-Cc cht kh c th dng: Na2S, Na2SO3, NaHSO3, FeSO4, SO2, khi cha kh SO2,...

-Cc phn ng chuyn Cr6+ v Cr3+:

Cr2O72- + 3S2- + 14H+ 2Cr3+ + 3S0 + 7H2O

Cr2O72- + 3HSO3- + 5H+ 2Cr3+ + 3SO42- + 4H2O

Cr2O72- + 6Fe2- + 14H+ 2Cr3+ + 6Fe3+ + 7H2O

Nu dng nc Na2S th trong dung dch Na2S b thy phn mnh v to kt ta

Cr(OH)3 nn khng cn thm vi: S2- + 2H2O H2S + 2OH-

Nu dng NaHSO3, FeSO4 th cn cho thm vi sa (hoc loi kim no ) kt ta

Cr(OH)3.

-Cng ngh x l nh sau: u tin NT c iu ha lu lng v nng . Sau

kim tra pH nu thy pH > 4 cn iu chnh sao cho pH 2-4 trc khi thc hin phn ng kh,

ng thi cn xc nh lng Cr6+ tnh ton lng cht kh ( thng dng gp 1,25 ln

lng tnh ton theo l thuyt).

Cht kh thng c chun b di dng dung dch 10% v cho vo b phn ng nh

thit b nh lng. Thi gian khuy trn b phn ng di 30 pht, sau khi phn ng kh kt

thc cho vi sa vo ( c chun b vi nng khong 2,5%) cho t pH 9, tip tc khuy

khong 3-5 pht sau cho NT sang b lng vi thi gian khong 2h.

5.3.3. Phng php oxy ha in ha

c dng x l NT vi mc ch phn hy cc cht c trong NT hoc thu hi cc

kim loi qu trn in cc.

p dng: X l NT cc phn xng m niken, m bc, cc nh my lm giu kim loi,

phn xng ty ra g kim loi.

V d: trn cc catot c th thu hi khong 60-70% ng trong NT cha cc hp cht

ng xianua bng oxy ha in ha.

V d: in phn cc dung dch cha st sunfat v axit sunfuaric t do bng mng trao

i anion s phc hi ti 80-90 % axit sunfuaric v thu hi wc bt st vi lng 20-50

kg/m3 dung dch.

Nu dng phng php in phn, NT sau x l c th dng li chun b cho cc

dung dch m v dung dch axit sunfuaric c th dng li cho cc qu trnh in phn sau. Theo

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kinh nghim cc nghin cu v thc t cho thy: nu NT cha xianua vi nng ln hn 1g/l

dng phng php in phn s r tin hn so vi phng php dng ha cht.

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6. Chng 6: KH TRNG V X NC THI RA NGUN

6.1. Kh trng NT 6.1.1. C ch

Cng vi cc giai on x l bc mt, bc hai,... s lm gim nng cc cht nhim

(cn l lng, BOD,..) p ng yu cu quy nh th s lng vi khun gy bnh cng gim c

trng bng ch tiu coliform (t 90-95%). Tuy nhin mt s loi vi khun gy bnh vn cn,

khi vo ngun nc mt, gp iu kin thun li s pht trin nhanh chng. Sau khi x l c

hc, sinh hc trong iu kin nhn to, vi khun gy bnh khng b tiu dit hon ton.

V vy m bo iu kin v sinh, NT th hoc NT sinh hot sau x l c hc

hoc x l sinh hc trong iu kin nhn to cn phi kh trng tip tc.

6.1.2. Kh trng nc thi bng clo

R tin, n gin, hiu qu cao

Thng dng: clo lng, natri hypoclorit lng NaClO, canxi hypoclorit rn

CaCl2(ClO)2.H2O

Tng lng Cl2, ClO- trong nc gi l lng clo hot tnh.

Kh trng c tin hnh theo cc bc:

-Xo trn ha cht kh trng vi NT trong cc b trn 1-2 pht

-Thc hin phn ng tip xc ha cht kh trng vi NT trong cc b tip xc v mng

dn NT ra ngun vi thi gian 15-20 pht, ph thuc vo cc iu kin xo trn v phn ng.

Tuy nhin, nu trong NT cha nhiu cht hu c chng s kt hp vi clo to cc sn

phm c hi,... d gy hi cho ngun nc c bit i ngun nc cp cho mc ch sinh

hot.

-Kh trng bng clo nc: nh lng clo, xo trn clo vi hi nc cng tc, iu

ch v vn chuyn n ni s dng ngi ta thng dng clorat (clorat hot ng lin tc

u, clorat hot ng lin tc t l vi lu lng nc, clorat chn khng). Nguyn tc hot

ng ca clorat: cc banlon clo s dng trn cn theo di lng clo tiu th. i vi clo

hi khi nn vo banlon c th b ln bi v vy trc khi qua lu lng k, clo cn c kh

bi, lu lng c iu chnh bng lu lng k v ha lng bng nc sch. Thng dng

clorat chn khng c p lc thp hn p sut khng kh do hi clo khng bay ra ngoi.

Cc banlon clo c cung cp t cc nh my sn xut.

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-Kh trng NT bng clorua vi: thng c 1 hay 2 thng ha trn, hai thng dch v

my bm nh lng.

Thng ha trn lm nhim v: trn clorua vi vi nc k thut t c dung dch

clorua vi dng sa 10 -15%. Bn cn t thng ny c x ra ngoi v vn chuyn i lm

kh. Sa clorua vi tip tc c pha long trong thng dung dch n nng di 2,5% sau

c my bm nh lng cp v mng trn.

Cc thng pha clorua vi c th lm bng composit, g, btng c bc nha,... dung

dch clo c khuy trn bng cnh khuy v trc chu ha cht.

p dng: cc trm XLNT cng sut < 1000 m3/ngy

6.1.3. Kh trng nc thi bng ozon

Ozon l cht kh, c kh nng oxy ha mnh. Phn ly trong nc:

Trong qu trnh, cc gc t do c hnh thnh, chng c kh nng oxy ha mnh v

tham gia vo qu trnh kh trng, Ngoi ra ozon cn tham gia phn ng vi cc cht nhim

khc trong nc thi, lm tng hiu qu x l.

Ozon c chun b t 2 ngun: ngun t khng kh, ngun t cng nghip c tinh

khit cao.

Do ozon nhanh b phn hy nn cn iu ch ngay ti ni s dng bng cch cho khng

kh hoc oxy kh i qua khe hp gia hai in cc cao th hng chc kV, cn lng in tiu

th ln, sn xut 1kg O3 t khng kh cn 14-20kW.h. Ozon c ha tan vo nc bng 2

cch: ha trn trc tip vi NT trong b tip xc qua thit b khuch tn kh hoc ha lng sau

trn vi NT trong mng trn trc khi vo b tip xc.

ha tan ca ozon trong nc cao gp 13 ln so vi oxy. Khi mi vo nc th ozon

khng phn ng ngay nhng khi lng oxy ha cc cht hu c v kh trng th phn

ng xy ra rt nhanh (3-8 giy) do b tip xc ch cn nh v nh hn nu dng clo x

l, thi gian cn: khong 15 pht.

Hiu qu kh trng bng ozon ph thuc vo cht lng NT.

u: hiu qu cao, t li hiu ng ph nh clo, nhng chi ph lp t h thng iu

ch ozon cao, in nng s dng ln.

6.2. Trn, b tip xc v cng x nc thi ra ngun Ha cht kh trng c a vo mng trn trn u cng nc thi, sau hn hp

ny chuyn qua b tip xc thc hin cc qu trnh v phn ng dit khun.

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B tip xc: to iu kin tip xc tt ha cht vi NT din ra qu trnh kh trng,

Khi nc lu li trong b, cc cht oxy ha tip tc oxy ha cc cht hu c m cc qu trnh

trc cha x l c, thi gian cn thit thc hin cc phn ng oxy ha dit khun 15-20

pht.

Trn quan im coi ngun tip nhn nc thi nh mt cng trnh x l tip tc, cc

cng x nc thi ra sng h phi p ng mt s yu cu:

+To iu kin xo trn tt nc ngun vi nc thi tng cng kh nng t lm

sch ca thy vc.

+Khng nh hng n m quan ca b v iu kin v sinh ca sng h

+D thi cng, lp t

+Dng x thi khng gy nh hng n b v y sng h

Vi cc yu cu nh vy nn cng x phi t ngp trong nc, di mc nc thp nht

trong h ti thiu l 0,3m. m bo dng chy ra khi ming x thi v gim tn tht p lc

th mc nc trong ging pha trccng x phi cao hn mc nc cao nht trong sng t 1-

1,5m. Vn tc dng chy trong cng x nc thi phi ti thiu 0,8m/s.

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7. Chng 9: X L BN CN NC THI

7.1. c tnh bn cn v cc phng php x l bn cn 7.1.1. S lng, thnh phn v tnh cht ca bn cn

Bn cn c hnh thnh:

+Sau x l c hc: Tng lng cn l lng TSS trong NT 50-70 gam/ngi/ngy.m.

Khong 25-50 gam cn/ ngi/ngy.m c gi li trong khu x l bc 1. m ca cn

sau lng 2h l 97,5% sau chng nn dn trong h tp trung n m 92-95%. Trung bnh

th cn lng ny l 0,6-08 lt/ ngi/ngy.m. Do y l thnh phn khng ho tan c sn

trong nc thi nn chng c gi l cn s cp. Trong cn ny c 65-70% l thnh phn hu

c, nhiu vi sinh vt c vi sinh vt gy bnh.

+Sau x l sinh hc (bn hot tnh d sau b aeroten hoc bn mng sinh vt sau b lc

sinh hc): bn th cp. c im: 8-32 gam/ ngi/ngy.m ph thuc vo dy chuyn

XLNT, m 96-99,2%, th tch bn c th t 2,5 lt/ ngi/ngy.m, kch thc tng i

ng nht, thnh phn hu c chim 70-75%, c cha nhiu trng giun sn, vi khun gy

bnh.

Thnh phn ca bn cn rt phc tp, cha nhiu cht hu c v cc nguyn t dinh

dng dng lm phn bn rt tt. Nhng li cha nhiu cht hu c d gy hi thi lm

nhim mi trng khng kh, cha nhiu vi khun c vi khun gy bnh, m ln, s dng

bn cn ti lm phn bn khng c li v kh vn chuyn.

7.1.2. Cc phng php x l bn cn nc thi

Mc ch: - n nh bn cn, kh cc cht hu c d gy thi ra.

- Lm kh bn cn d vn chuyn v s dng

- Kh c bn cn hoc thu hi cht qu

a) Tch nc s b: lm gim m bn cn cc khu x l tip theo din ra c n nh

v gim c khi lng xy dng cc cng trnh cng nh tit kim c ha cht s dng

trong qu trnh x l. Tuy nhin, nu gim qu mc m s to nn bn cn kh, cc iu

kin cng ngh ca cc cng trnh n nh bn cn s kh khn.

b) Qu trnh n nh bn cn:y l qu trnh phn hy sinh ha cc cht hu c ca bn cn

din ra trong iu kin ym kh hoc hiu kh.

c) Qu trnh x l s b bn cn: Hai phng php x l s b bn cn nh sau:

+ X l s b bn cn bng ha cht:l qu trnh ng kt cc ht phn tn tinh v keo

to thnh bng cn ln, ph hy v thay i cc dng lin kt ca nc, thay i cu trc

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cn v kh nng nh nc ca n. Ha cht thng dng l: vi, phn st FeCl3, phn nhm,

cc loi polimer khc.

+ X l s b bn cn khng dng ha cht: s dng cc bin php nhit, lng, keo t

in ha, phi nng,...

7.2. Cc cng trnh lng t 1 kt hp ln men bn cn lng 7.2.1. B t hoi

y l cng trnh XLNT bc 1 (x l s b) ng thi thc hin 2 chc nng: lng

nc thi v len men cn lng.

Vt liu: B t hoi c dng hnh ch nht hoc hnh trn xy dng bng gch, b tng

ct thp, vt liu composite.

Cu to: B c chia thnh 2, 3 ngn. Cn lng tp trung ch yu ngn th nht nn

dung tch ngn ny chim khong 50-75% dung tch ton b, cn li l ngn th 2 (cng c th

thm ngn th 3). B thng su 1,5-3,0 m. Chiu su lp nc trong b: 0,75 1,8 m, chiu

rng nh nht: 0,9; chiu di nh nht: 1,5 m. Cc ngn b t hoi c chia lm 2 phn: phn

lng nc thi (pha trn) v phn ln men cn lng (pha di). Th tch b nh nht: 2,8 m3,

trong th tch phn lng khng nh hn 2,0 m3.

Nc thi lu li trong b t 1-3 ngy. Qua thi gian 3-6 thng, cn lng ln men ym

kh. Qu trnh ln men ch yu din ra trong giai on u l ln men axit, cc cht kh to ra

trong qu trnh phn gii CH4,CO2, H2S,...Cn trong b t hoi c ly ra 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.

p dng: Cu to n gin, d vn hnh v qun l, XLNT ti ch cho cc khu tp th,

cm dn c di 500 ngi hoc lu lng NT di 30 m3/ngy, c khi cng trnh ny cn

kt hp vi cc cng trnh khc nh: ngn lc sinh hc, ging thm,...

7.2.2. B lng 2 v

7.2.3. B lng trong kt hp ngn ln men

7.3. B metan B metan l cng trnh c xy dng ln men (n nh ym kh) cc loi bn cn

trong nc thi. Vt liu: thp, b tng ct thp, dng hnh trn trn mt bng. C s :

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Sn phm ca qu trnh ln men ch yu l CH4 ( chim khong 60% lng kh to

thnh, ngoi ra cn c: CO2, NH3,...) v vy c gi l b metan. Kh ny c th tn dng lm

nhin liu.

Bn cn sau qu trnh ln men (bn cn chn) c mu en ca sunfua st, cc cht hu

c d gy thi ra b phn hy, vi khun gy bnh hu nh khng cn, trng giun sn b

tiu dit trong iu kin ln men nng.

Nhit l mt trong nhng yu t quan trng i vi qu trnh ln men trong b

metan. Nhit cng cao, thi gian ln men cng gim. Lu : cc loi vi khun k kh ln

men mtan c 2 nhm: nhm a m vi nhit ti u 30-35OC, nhm a nng vi nhit

ti u 50-55OC.

Trong b metan ch ln men m, thi gian ln men 20-45 ngy, i vi ch ln

men nng th 10-20 ngy.

Ln men nng c u im: cn chn u, dung tch b b, hu ht trng giun sn trong

bn cn b tiu dit, m bo nhit cn thit , bn cn c sy nng bng h thng cp

nhit, b c lp t di t n nh nhit v cn bng p sut.

Cc yu t km hm qu trnh ln men trong b metan l cc cht hot tnh b mt, kim

loi nng, s thay i pH.

7.4. Nn bn cn Nguyn tc hot ng: Bn sau b lng t 2 thng thng c m 96-99,2% nu a

v b metan th m ln, dung tch b tng, nh hng n hiu qu ln men cng nh khng

kinh t.

tng cng qa trnh nn bn cn, ngi ta b sung thm ha cht ng t, khi

thi gian nn s gim khong 2-3 ln v lng cn l lng trong nc bn gim theo.

7.5. Lm kh bn cn 7.5.1. Sn phi bn

Mc ch: c chc nng lm mt nc bn cn ( m cn khong 80%) trong iu

kin t nhin. Sau qu trnh phi, do tc ng ca tia t ngoi, vi khun gy bnh cn li trong

bn cn cng nh mi hi thi gim i.

7.5.2. Lm kh bn cn bng phng php c hc

i vi cc trm x l c cng sut ln khng din tch lm sn phi bn, nhng

vng kh hu ma nhiu,ngi ta thng lm kh bn cn bng cc thit b c kh: my lc

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chn khng gim m n 75-80%, my p lc bng ti gim m n 70-75%, ly tm lm

gim m n 65-75%, my xung lc gim m n 82-94%.

7.6. Cc bc, phng php XLNT v bn cn trong NTT H thng XLNT thng bao gm tng hp cc phng php c hc, ha hc v ha l,

sinh hc.

Vic p dng cc phng php trn ph thuc vo: tnh cht NT, lu lng NT, kinh

ph, din tch, a hnh, mc ch s dng ca ngun nc tip nhn,...

dng cc bin php nh dit khun, kh tip cc cht bn cn li trong nc thi nh:

- X l bn cn trong NT: bn cn c phi kh v san nn, rc c nghin nh

hoc vn chuyn v bi chn lp. Bn cn c th c dng lm phn bn.

- Giai on kh trng: sau khi lm sch NT th y l giai on bt buc i vi mt s

loi nc thi hoc mt s dy chuyn cng ngh x l trong iu kin nhn to.

Ngoi ra khi trm XLNT b tr gn khu dn c v cc cng trnh cng cng, mt

khong cch no cha m bo th cn lu thm cc bin php, cng trnh kh mi hi t

NT.

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Chng 10: MT S V D V XLNT CN

7.7. C s chn phng php XLNT cc x nghip cng nghip C th phn chia NT cng nghip thnh cc nhm sau: NT rt bn-m c, NT t bn,

long-nc qui c sch, dung dch cng ngh nguyn th, nc dng li hay dng trong h

thng cp nc tun hon, NTSH.

Trong iu kin l tng, mi x nghip nn c mng li thot nc ring bit

dn v x l ring tng loi NT trn. Song hu ht cc x nghip thitkhng th c h thng

thot nc l tng c. Kt qu l: hn hp NT vi s lng nhiu m khng mt

phng php no c th x l c.

V vy, khi XLNT cng nghip phi dng n cc phng php t tin nh phng

php ha hc th phi thn trng vic chn la phng php thch hp, kinh t do trc

ht cn kho st v cng ngh sn xut, v s hnh thnh NT, s lng v thnh phn tnh

cht,vi cc ni dung sau:

+lm quen vi mng li thot nc bn trong v bn ngoi cc phn xng SX, lp s

mt bng ca cc mng li .

+lm quen vi dy chuyn cng ngh SX bit v vic s dng v NT ca my mc

cng ngh.

+chn v tr ly mu phn tch cc ch tiu ha l, vi sinh vt, o lu lng NT.

+lm sng t v c kt lun chung v tnh trng ca x nghip

7.8. S dng nc trong SX v NT cng nghip Nc s dng trong cng nghip cho nhiu mc ch khc nhau: nc tham gia trc

tip hay gin tip vo qu trnh SX chnh gi l nc k thut, nc phc v sinh hot cho con

ngi lm vic trong xi snghip v nc d phng ha hon, s c.

Bng :Phn loi theo mc ch s dng

Nc

Nc sinh hot Nc k thut Nc d phng

Nc nng lng Nc lm ngui Nc cng ngh

Nc b sung Nc tun hon Nc lm MT Nc ra Nc tham gia trc tip vo qt SX

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S lng v thnh phn NT s ph thuc vo loi hnh SX. Nguyn nhn ca s khc

nhau l:

+Cng ngh SX khc nhau, t cc cng on ch bin gia cng nguyn liu n cc

cng on hon thin sn phm.

+Tnh cht nguyn liu u v sn phm khc nhau, iu ny dn n s khc nhau v

cc cht gy nhim NT ca cc loi hnh cng ngghip.

+Phng thc hot ng ca tng c s cng nghip nh lm vic theo chu k hay s

ca lm vic trong ngy.

+Gi thnh nc cp v gi thnh x l nc a phng, nhng ni gi thnh nc

cao i hi phi s dng tit kim v lng NT gim.

Cch tt nht gim lng nc cp l xy dng h thng cp nc tun hon khp

kn.

7.9. Phng php tip cn gii quyt vn nc thi cng nghip Hng chnh gim NT v s nhim i vi cc ngun nc l: cn thit lp h

thng khp kn (nh my hay khu vc). u im: s dng hp l nc trong cc qu trnh

cng ngh, thu hi ti a cc phn t c gi tr trong NT, gim chi ph u t xy dng v vn

hnh, ci thin iu kin v sinh v gim nhim mi trng.

Hng khc: thit lp SX khng nc thi vi ni dung chnh:

+Ch bin lin hp nguyn liu v vt liu ban u

+Thit lp cc qu trnh cng ngh mi SX v ch bin cc sn phm khng c s

tham gia ca nc.

+Gim lng NT v mc nhim bng cch hon thin cc qu trnh cng ngh v

thit b, s dng nguyn liu khng c nc.

+ng dng cc my lm sch bng khng kh.

+lm sch ton din NT ca cc c s cng nghip cng nh NT SH cc trm x l

cc b hay ca thnh ph thu c nc c th s dng trong cc qu trnh cng ngh v

trong cc h thng cp nc tun hon.

+ng dng cc phng php v tin tin lm sch NT

+S dng tt c NT sau khi lm sch v lm ngui trong cc qu trnh cng ngh

trong cc h thng tun hon NT.

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+Duy tr thnh phn mui c nh ca nc trong h thng cp nc tun hon bng

cch ly ra mt phn nc vi mc ch loi mui mt phn hay hon ton phn nc v

tun hon nc khng c mui vo h thng cp nc tun hon.

Phng nga, gim lng NT v cc cht gy nhim nc l phng php tch cc v

ch ng. Phng php ny i vo bn cht ca qu trnh cng ngh, kim tra qu trnh SX,

ngun nguyn liu, tm nguyn nhn, ngun pht sinh ra NT, t c cc bin php gii quyt

tn gc cc cht gy nhim nc, phn lung cc dng thi gy nhim v khi cn thit x

l cc b cc dng ny vi mt lng nh.

u: gim lng nc s dng, gim lng NT cn x l, gim ti lng cc cht gy

nhim, hiu qu kinh t cao do gim cho ph x l NT.

lm sch NT cng nghip c th s dng mt trong cc loi cng trnh x l sau: x

l cc b (x l ti xng), x l chung (ti trm x l chung ca nh my), x l tp trung

cho c thnh ph hay khu vc. Trong cng nghip ha cht thng t khi x l tp trung.

+X l cc b: c dng l sch NT t cc thit b hay phn xng. C th thu ji

c nhng cht c gi tr nn ngi ta thng s dng phng php lm sch nh lng, tuyn

ni, trch ly, chng, hp ph trao i ion,... x l cc b, dng thi cn c phn lung tt.

X l cc b ch cn x l lng NT nh vi hm lng cht nhim cao, trnh c hin

tng lm long vi cc dng thi khc trc khi a vo x l tp trung.

+X l chung: dng x l NT ca ton nh my. Nhng c s sn xut ha cht, ha

du thng c trang b cc cng trnh x l loi ny.

+X l tp trung thnh ph: Nhim v chnh l lm sch c hc v sinh hc i vi

NT. Nc sau khi x l th cp c kh trng bng clo hoc ozon trc khi thi ra ngun

nc t nhin. Bn cn sau khi phi kh c th lm phn bn nu giu N, P, K hoc chn lp,

thiu hy. Trm x l tp trung ca thnh ph dng x l NT th bao gm NTSH v

nc thi cng nghip sau khi x l cc b.

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7.10. Mt s v d 7.10.1. Nc thi trong cng nghip phn bn ha hc

7.10.1.1. Cc cng on sn xut phn m, ngun gc NT

7.10.1.2. Cc cng on sn xut phn ln, ngun gc NT

7.10.1.3. Cc cng on sn xut phn kali, ngun gc NT

7.10.1.4. c im chung v nh hng n MT ca NT ca ngnh SX phn bn

7.10.1.5. XLNT ngnh phn bn

7.10.2. Nc thi trong cng nghip thuc da

7.10.2.1. Cng ngh v ngun pht sinh NT

7.10.2.2. Cc phng n XLNT

7.10.3. Nc thi trong cng nghip dt nhum

7.10.3.1. Cng ngh v ngun pht sinh NT

7.10.3.2. Cc phng n ngn nga v gimNT

7.10.3.3. Cc phng n XLNT

7.10.4. Nc thi trong cng nghip giy

7.10.4.1. Cng ngh v ngun pht sinh NT

7.10.4.2. Cc phng n ngn nga v gimNT

7.10.4.3. Cc phng n XLNT

7.10.5. Nc thi trong cng ngh sn xut bia

7.10.5.1. Cng ngh v ngun pht sinh NT

7.10.5.2. Cc phng n ngn nga v gimNT

7.10.5.3. Cc phng n XLNT

7.10.6. Nc thi trong cng nghip luyn kim, gia cng kim loi

7.10.6.1. Cng ngh v ngun pht sinh NT

7.10.6.2. Cc phng n ngn nga v gimNT

7.10.6.3. Cc phng n XLNT

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Ti liu tham kho:

Trnh Th Thanh, Trn Ym, ng Kim Loan, Gio trnh cng ngh mi trng,

Nh xut bn i hc Quc gia H Ni

Trn c H, X l nc thi th, Nh xut bn Khoa hc v k thut, 2006

Trn Hiu Nhu, Thot nc v x l nc t hi cng nghip, Nh xut bn

Khoa hc v k thut, 1998

Trn Vn Nhn, Ng Th Nga, Gio trnh cng ngh x l nc thi, Nh xut

bn Khoa hc v k thut

Vin Cng ngh mi trng, S tay cng ngh x l nc thi cng nghip,

2009

HongMinhvinaxanhvn

www.vinaxanh.vn