Nhom 1,5-Xu Ly Sinh Hoc Cac Hop Chat Chua N

8/2/2019 Nhom 1,5-Xu Ly Sinh Hoc Cac Hop Chat Chua N

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CC QU TRNH SINH HC TRONG X L NC ti:X L SINH HC CC HP CHT CHA NITO

Trng:H KHTNLp: 09CMT

GVHD: Trng Thanh CnhNhm thc hin: Nhm 1,5

Danh sch thnh vin nhm:

STT H V TN MSSV1 Lu Th Thanh Phng 09221992 inh Th Kim Ngn 09221613 Phm Th Lin 09221224 c Th Mai 0922143

5 Phm Th Vn 09222976 Thn Th Minh Sng 09222177 L Hiu Thy Anh 09220038 Nguyn Th Hng Anh 09220049 Chu Th Thanh Thy 0922255

10 Phm Dip Linh Hng 092211211 Trn Thin Thin Thanh 092222812 ng Th Minh Tm 092222013 Phan Tn Dng 092204614 Danh Phm Hong Anh 092200115 Trnh Xun i 092205016 Nguyn Th Kim Anh 082200917 V Trng Thnh 0822253

Ti liu tham kho: + Environmental Biotechnology: Principles and Applications(Bruce E,Rittmann Perry L.McCarty)

+Sinh ha mi trng; PGS.TS Trng Thanh Cnh; Nh xut bn Khoahc v K thut

DANH MC VIT TTVSS : Volatile suspended solids ( cht rn l lng d bay hi)MLVSS : mixedliquor volatile suspended solids ( cht rn l lng hn dch d bay hi)MLSS : mixedliquor volatile suspended solids (cht rn l lng hn dch)SRT : Sludge retention time ( Thi gian lu bn)SBR : Sequencing batch reactor ( B hiu kh gin on)RBC : Rotating biological contactor (a quay sinh hc)TKN : Total Kjeldahl Nitrogen ( tng Nit dng ammoniac/amoni)SMP :Soluble microbial products (sn phm vi khun ha tan)


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MC LCTng Quan1. Trng thi tn ti Nit trong nc thi2. Tc hi ca Nit trong nc thi

2.1Tc hi ca Nit i vi sc khe cng ng2.2Tc hi him Nit n mi trng2.3Tc hi ca Nit i vi qu trnh x l nc

I. C s cc qu trnh x l nit bng phng php sinh hc1. Qu trnh Nitrate ha

1.1Cc vi khun tham gia qu trnh Nitrate ha1.2Qu trnh Nitrate ha bn hot tnh

1.2.1 Qu trnh Nitrate ha bn bc 11.2.2 Qu trnh Nitrate ha bn bc 2

1.3Mng sinh hc qu trnh Nitrate ha1.4Vai tr ca t s BODL/TKN

2. Qu trnh phn Nitrate ha2.1Cc vi khun tham gia qu trnh phn Nitrate ha2.2Qu trnh phn Nitrate ha bc 3

2.2.1 Qu trnh phn Nitrate ha bc 3 vi bn hot tnh2.2.2 Qu trnh mng sinh hc

2.3Qu trnh phn Nitrate ha bn bc 12.3.1 Cc qu trnh c bn bn bc 12.3.1.1Lu gi v tng hp sinh khi2.3.1.2Tin kh Nitrate2.3.1.3Kt hp qu trnh nitrate ha v phn Nitrate ha

2.3.2 Qu trnh bin i c bn bn bc 12.3.2.1Qu trnh Barnard2.3.2.2B phn ng hng lot2.3.2.3H thng mng sinh hc

Qu trnh ANAMMOX

II.Kt Lun


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I. Tng quan1. Trng thi tn ti Nit trong nc thi

Trong nc thi, cc hp cht ca nit tn ti di 3 dng: cc hp cht hu c, amoni v cchp cht dng xy ho (nitrit v nitrat).

+ Hp cht hu c cha Nit l 1 phn cu thnh phn t protein hoc l thnh phn phn hu

protein nh l cc peptid, axit amin, ur.+ Hm lng amoniac (NH3) chnh l lng nit amn (NH

+4) trong nc thi sinh hot, nc

thi cng nghip thc phm.......

Trong nc thi sinh hot nit tn ti di dng v c (65%) v hu c(35%). Ngun nit ch

yu l tnc tiu. Mi ngi trong mt ngy x vo h thng thot nc 1,2 lt nc tiu,

tng ng vi 12 g nit tng s. Trong s nit trong ur (N-CO(NH2)2) l 0,7g, cn li lcc loi nit khc. Ur thng c amoni ho theo phng trnh nh sau.

Trong mng li thot nc ur b thu phn:CO(NH2)2 + 2H2O = (NH4)2CO3 (1.2)


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Sau b thi ra:(NH4)2CO3 = 2NH3 + CO2 + H2O (1.3)

Nh vy NH3 chnh l lng nit amn trong nc thi. Trong iu kin ym kh amoniac cng

c th hnh thnh t nitrat do cc qu trnh kh nitrat ca vi khun Denitrificans.Lngcht bn Nit amn (N-NH4) mt ngi trong mt ngy x vo h thng thot nc: 7

g/ng.ngy

+ Nitrit (NO2-)

Sn phm trung gian ca qu trnh xy ho amoniac hoc nit amoni trong iu kin hiu kh

nhcc loi vi khun Nitrosomonas. Sau nitrit hnh thnh tip tc c vi khun Nitrobacterxy ho thnh nitrat.

Cc qu trnh nitrit v nitrat ho din ra theo phn ng bc I:

NH4+ kn

NO2- km

NO3-

Trong : kn v kml cc hng s tc nitrit v nitrat ho.

Cc phng trnh phn ng ca qu trnh nitrit v nitrat ho c biu din nh sau:

NH4+

+ 1,5O2Nitrosomonas

NO2-+ H2O + 2H

+

NO2-

+ 0,5O2Nitrobacter

NO3-

NH4+

+ 2O2 NO3-+ H2O + 2H

+

Qu trnh nitrat ho cn 4,57g xy cho 1g nit amn. Cc loi vi khun Nitrosomonas v

Nitrobacterl cc loi vi khun hiu kh thch hp vi iu kin nhit t 2030oC.

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

kin ym kh.

Ngoi ra, nitrit cn c ngun gc tnc thi qu trnh cng nghip in ho. Trong trng thicn bng mi trng nc, nng nitrit, nitrat thng rt thp, n thng nh hn 0,02

mg/l. Nu nng amoni, gi tr pH v nhit ca nc cao, qu trnh nitrit ho din ra thun

li, v nng ca n c tht n gi tr ln. Trong qu trnh xl nc, nitrit trong nc stng ln t ngt.

+ Nitrat (NO3-) l dng hp cht v c ca nit c ho tr cao nht v c ngun gc chnh t

nc thi sinh hot hoc nc thi mt s ngnh cng nghip thc phm, ho cht,... cha mtlng ln cc hp cht nit. Khi vo sng h, chng tip tc b nitrat ho, to thnh nitrat.

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

trong nc thi chng t s hon thin ca cng trnh xl nc thi bng phng php sinh

hc.


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Mt khc, qu trnh nitrat ho cn to nn s tch lu xy trong hp cht nit cho cc qu

trnh xy ho sinh ho cc cht hu c tip theo, khi lng xy ho tan trong nc rt t hoc b

ht.

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

s dng li trong cc qu trnh xy ho cc cht hu c khc. Qu trnh ny c thc hin nh

cc vi khun phn nitrat ho (vi khun ym kh tu tin). Trong iu kin khng c xy t do mmi trng vn cn cht hu c ccbon, mt s loi vi khun kh nitrat hoc nitrit ly oxy cho

qu trnh xy ho cc cht hu c. Qu trnh khnitrat c biu din theo phng trnh phn

ng sau y:

4NO3-+ 4H

++ 5Chu c 5CO2 + 2N2 + 2H2O

Trong qu trnh phn nitrat ho, 1g nit s gii phng 1,71g O2 (kh nitrit) v 2,85g O2 (khnitrat).

2. Tc hi ca Nit trong nc thi2.1Tc hi ca Nit i vi sc khe cng ng

Trn bnh din sc kho Nit tn ti trong nc thi c th gy nn hiu ng v mi trng. Sc mt ca Nit trong nc thi c th gy ra nhiu nh hng xu n h sinh thi v sc kho

cng ng. Khi trong nc thi c nhiu Amnic c th gy c cho c v h ng vt thu

sinh, lm gim lng xy ho tan trong nc. Khi hm lng nit trong nc cao cng thm

hm lng phtpho c th gy ph dng ngun tip nhn lm nc c mu v mi kh chu

c bit l lng xy ho tan trong nc gim mnh gy ngt cho c v h sinh vt trong h.

Khi x l nit trong nc thi khng tt, hp cht nit i vo trong chui thc n hay trong

nc cp c th gy nn mt s bnh nguy him. Nitrat to chng thiu Vitamin v c th kthp vi cc amin to thnh cc nitrosamin l nguyn nhn gy ung th ngi cao tui. Tr

s sinh c bit nhy cm vi nitrat lt vo sa m, hoc qua nc dng pha sa. Khi lt vo

c th, nitrat chuyn ha thnh nitrit nh vi khun ng rut. Ion nitrit cn nguy him hnnitrat i vi sc khe con ngi. Khi tc dng vi cc amin hay alkyl cacbonat trong c th

ngi chng c th to thnh cc hp cht cha nit gy ung th. Trong c th Nitrit c th xy

ho st II ngn cn qu trnh hnh thnh Hb lm gim lng xy trong mu c th gy ngt, nn,khi nng cao c th dn n t vong.

2.2Tc hi ca nhim Nit i vi mi trngNit trong nc thi cao, chy vo sng, h lm tng hm lng cht dinh dng. Do vy n

gy ra s pht trin mnh m ca cc loi thc vt ph du nh ru, to gy tnh trng thiu oxytrong nc, ph v chui thc n, gim cht lng nc, ph hoi mi trng trong sch ca

thy vc, sn sinh nhiu cht c trong nc nh NH4+, H2S, CO2, CH4... tiu dit nhiu loi

sinh vt c ch trong nc. Hin tng gi l ph dng ngun nc


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2.3Tc hi ca Nit i vi qu trnh x lnc thi

S c mt ca Nit c th gy cn tr cho cc qu trnhx l lm gim hiu qu lm vic ca cc cng trnh.

Mt khc n c th kt hp vi cc loi ho cht trong x l to cc phc hu c gy c

cho con ngi.

II.C s cc qu trnh x l Nit bng phng php sinh hc1. QU TRNH NITRATE HA

- Khi nim: Qu trnh nitrate ha l qu trnh oxy ha sinh ha nit ca cc mui amonu tin (NH4

+-N ) thnh nitrit (NO2-N) v sau thnh nitrat (NO3

-N) nh hot ngca vi sinh vt (VSV) trong iu kin thch ng (c oxy v nhit trn 4oC) : NH4

+-N NO2-N NO3-N

- Tm quan trng ca qu trnh nitrate ha:o V nhu cu oxy ( ln n 4,57g O2/g NH4+-N) v c t sinh ra t cc sinh vt

trong nc, nn s chuyn ha NH4+-N l bc cn thit vi mt s loi nc

thi.o Ngoi ra, x l nc thi cng lin quan n qu trnh kh nitrate bin i

NH4-N thnh NO3-N

o Qu trnh nitrate ha loi b NH4-N t ngun nc cp cng c thc hin lm cho nc bn vng v mt sinh hc.

1.1 Cc vi khun tham gia qu trnh Nitrate ha

- Vi khun nitrate ha gm: sinh vt t dng, ha t dng, vi sinh vthiu kh

bt buc.

o Vi sinh vtt dng:chng c nh v kh carbon v c. y l mt qu trnhtiu tn nhiu nng lng, qu trnh ny gip Vi sinh vt nitrate ha tch ly mt

gi tr fs0

v Y (nh hn Vi sinh vt d dng hiu kh)-lun gy nhim hthng bn hot tnh v mng sinh hc.

o Vi sinh vtha t dng: lm v Y nh hn bi v ngun cho in tcachng gii phng t nng lng trn mt e tng ng so vi ngun cho in thu c.

o Vi sinh vthiu kh bt buc: dng O2 h hp nh mt cht phn ng trctip cho s oxy ha NH4

+ thnh NH2OH (hydroxylamin). Cht sau cng s dngoxy c th l l do ti sao Vi sinh vt nitrate ha li lin quan n s khng dung


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np ca nng thp oxy ha tan; qu trnh d ha thp do s gii hn nng oxy khng tng tc vi Vi sinh vtd dng.

Nitrate ha t dng (autotrophic nitrification)- Qu trnh nitrat ha gm 2 giai on:

+ Giai on 1: NH4+c oxy ha thnh NO2

-

1/6NH4+ + 1/4O2=1/6NO2

- + 1/3H+ + 1/6H2O [9.1]

G0= -45,79kJ/e-eq

Chng vi khun thng dng trong bc 1 l Nitrosomonas; tuy nhin, Nitrosococcus,Nitrosopira,Nitrosovibrio vNitrosolobuscng c th oxy ha NH4

+ thnh NO2-. Nitrifiers oxy

ha chng amoni- c tin t l Nitroso. Chng Nitrosomonasv nhng loi thuc chng nykhng nht thit l loi u th.

+ Giai on 2: S oxy ha NO2- thnh NO3-

NO2- + O2 = NO3

- [9.2]

G0= -37,07kJ/e-eq

Mc dNitrospira,Nitrospina,Nitrococcus vNitrocystisvnhin din trong phn ng giaion 2, nhngNitrobacter l chng vi sinh oxy ha NO2

-ph bin nht. Trong chngNitrobacter, nhiu loi ph d nhn thy, ngoi trnhng loi c mi lin h di truyn trongcng chi alpha ca proteobacteria (Teske et al.,1994). Nhng nghin cu gn y dng my d

oligonucleotide ch ra on 16S rARN ca Nitrobacter, vic ny cho thy rng Nitrobacterkhng phi l chng oxy ha nitrite quan trng nht trong qu trnh x l ncthi.Nitrospirac bit nh mt nitrifier tri hn.


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Nitrobacteria Nitrospira

Khi nitrifiers tn ti trong mi trng c mt nhng hp cht hu c nh nhng nh my x lnc thi, k l l chng khng pht trin bng cch s dng nhng phn t hu c nh lngun carbon ca chng. Trong khi l do sinh ha m ngun carbon hu c c loi tr vn

cha c bit n th s duy tr tnh l thuc t dng ca chng c l nh vo s lin kt tinha vi Vi sinh vt quang ha.

Cc phn ng oxy ha ammonia thnh nitrite hay oxy ha nitrite thnh nitrate l cc qu trnhsinh nng lng. Nng lng gii phng t qu trnh nitrate ha c vi khun s dng cho qutrnh tng trng ca chng.

Nitrate ha d dngQu trnh nitrate ha cc hp cht hu c cha Nit c th c thc hin bi 1 s vi khun ddng nhArthrobacter, Flavobacterium, Thiosphaera.

Phng trnh phn ng Nitrate ha d dng

R-NH2R-NHOHRNONO3-Khc vi vi khun nitrate ha t dng oxy ha trc tip NH3, cc vi sinh vt nitrate ha ddng oxy ha cc hp cht Nit dng kh nh hydroxylamine, aliphatic v hp cht chanhn thm. Mt im khc nhau na l, qu trnh nitrate ha d dng khng sinh nng lng.Do vy cung cp nng lng cho qu trnh trao i cht, vi sinh vt phi phn gii c chthu c khai thc nng lng.

Bng 9.1 v 9.2 tm tt nhng thng s gc v c bn, m t ha hc lng php v ng nngca tc nhn oxy ha amoni v nitrit mt cch trnh t.

Bng 9.1: Gi tr thng stc nhn oxy ha amoni t 5 n 25oCGi tr ti T=

Thng s 5oC 10oC 15oC 20oC 25oC 0.14 0.14 0.14 0.14 0.14Y, mg VSSa/mg NH4

+-N 0.33 0.33 0.33 0.33 0.33Qn, mgNH4

+-N/mg VSSa-d 0.96 1.3 1.7 2.3 3.1q02, mg O2/mg VSSa-d 2.9 3.8 5.1 6.8 9.2

,d-1

0.32 0.42 0. 58 0.76 1.02KN, mgNH4

+-N/1 0.18 0.32 0.57 1.0 1.50


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KO,mgO2/1 0.50 0.50 0.50 0.50 0.50B,d-1 0.045 0.060 0.082 0.11 0.15[]lim, d 3.6 2.8 2.1 1.5 1.2SminN, mg NH4

+-N/1 0.029 0.053 0.094 0.17 0.26SminO, mgO2/1 0.081 0.083 0.084 0.085 0.085

Bng 9.2: Gi tr thng s tc nhn oxy ha nitrit t 5 n 25oCGi tr ti T=

Thng s 5oC 10oC 15oC 20oC 25oC 0.10 0.10 0.10 0.10 0.10YN, mg VSSa/mg NO2

--N 0.83 0.8 3 0.83 0.83 0.83Qn, mgNO2

- -N/mg VSSa-d 4.1 5.5 7.3 9.8 13.0q02, mg O2/mg VSSa-d 4.2 5.6 7.5 10.1 13.5

,d-1

0.34 0.45 0. 61 0.81 1.1KN, mgNO2

--N/1 0.15 0.30 0.62 1.3 2.7K Omg O2/1 0.68 0.68 0.68 0.68 0.68B,d-1 0.045 0.060 0.082 0.11 0.15[]lim, d 3.5 2.6 1.9 1.4 1.1SminN, mg NO2

--N/1 0.024 0.047 0.10 0.20 0.42SminO, mgO2/1 0.11 0.11 0.12 0.11 0.11

Quan st thy mi bng rt thp. So snh vi gi tr in hnh 0.6 0.7 ca Vi sinh vthiu kh, ta thy Nitrifiers d tr rt t trong sinh khi. Gi tr thp lin quan trc tip ti gitr Y thp.Trong khi tr s Y ca tc nhn oxy ha amoni khng thp hn nhiu so vi Vi sinhvt hiu kh, ta thy gn bng nhau l do o gic bi vic dng n v khc nhau trong muthc. Trong n v g VSSa /g OD Y- tc nhn oxy ha amoni xp x 0.1 so vi khong 0.45Visinh vtd dng.Tc tng trng cc ica c hai nhm u thp, vic hai t hn1/ d 20oC. Vi cc gitr ca nh nh vy , gi tr gii hn ca phi ln: Tt c cc gi tr ln hn 1d. Mtkhc,nitrifiers c th tc ng nng hoc n mc rt thp, v gi tr Smin di 1mg/ l.

Nh vy, qu trnh nitrat ha c th c hiu qu cao, min l SRT c duy tr trn v oxy ha tan. Cc gi tr nh lng K0 tng i cao m nitrifiers khng hp nng DO thp.Tip tc hot ng vi mt D.O.di K0 s tng cho nitrifiers v c th dn n ra tri,cng nh -N trong dng thi.Cc tc dng nhit c hin th trong bng 9.1 v 9.2 l kh quan trng, bi v qu trnhnitrat ha i khi khng th xy ra khi nhit nc thp. Trong thc t, qu trnh nitrat ha nnh c th c duy tr mc 50C hoc thp hn, min l SRT vn cn cao. i vi 50C,mt yu t an ton ch c 5 yu cu rng xc 3.6x5= 18d. Mt vn ca qu trnh nitratha nhit thp l tr nn rt nh, lm cho s phc hi qu trnh nitrat ha sau khi ra tridin ra chm.V vy, trnh nitrifier ra tri do bn d tha hoc DO thp, hoc c ch phil mt u tin tuyti, c bit l i vi nhit thp.So snh trc tip cc thng s, chng hn nh f0s , , [xmin] lim, v Smin, tng tcho cc loinitrifiers.Trng hp ny l hon ton hp l,v c hai u l ha t dng hiu kh oxy ha

N. Hn na, chng hu nh lun lun cng tnti trong cng mtmi trng sng, tri qua


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cng SRT v nng oxy. Cc thng s gii hn tng ng phn nh s tng ng ca sinhha v sinh thi.Phng trnh sau yl mtphnngcn bngtng th cho qu trnh oxy ha hon ton :

+ 1.815 O2 + 0.1304 CO2 = 0.0261 C5H7O2N + 0.973 + 0.921 H2O +1.973H+ [9.3]

Bn cnh vic hnh thnh mng li nitrifier thp (Ynet = 0.21g VSSa/g N),phng trnh nyminh hahai tnh nngquan trng khcca qu trnh nitrat ha. u tin, qu trnh nitrat hato ra mt nhu cu oxy ln.Trong v d ny, lng oxy cn thit l 1.815 x 32/14 = 4.14 g O2 /g NH4 +-N . Th hai, qu trnh nitrat ha gn nh sinh ra 2 acid mnh sau khi loi b NH4

+.Trong cc n v khi lng thng thng, kim tiu th l 1.973 x 50/14 = 7.05 g CaCO3 /g NH4

+ -N. Bc u tin, qu trnh oxy ha amoni, chu trch nhim cho vic sn xut acid.Nitrifiers sn xutcc sn phmvi khun ha tan, c th c tiu thbi cc vi khunddng (Rittmann, Regan, Stahl, nm 1994; deSilva v Rittmann, 2000a, b). iu th hinrng hu ht SMP m nitrifier sn xut l BAP. SMP ni chung rt quan trng: y l mtphnca qu trnhphn hy ca cc nitrifiers v gimlng tng hpca nitrifiers. Ngoi ra

nitrifiers to e cho sinh vt d dng v tngsinh khid dng.Nitrifiers c cho l rt nhy cm vis c chha hc. Tc tng trngrt chmcanitrifiers lm tng tcng tiu cccas c ch, theo mt hng no c v nh l nitrifiersth nhy cm hn so vi nhng sinh vt sinh trng nhanh. Hn na, mt s cht c ch rrng l ngun cung cp e c qu trnh oxy ha lm cn kit DO v c th l nguyn nhn lmgim oxy. Tuy nhin, nitrifiers nhy cm vis c cht nhiuhp cht hu cc v v c.Trong snhng vn c lin quan nht l: mng li NH3 ( pH cao hn), khng phn lyHNO2(thng l pH thp),b mt anion, kim loi nng, ha chtkh trng bng clohu c,v pH thp.Mt vn gy tranh ci l mixotrophy (Ngun gc ca trao i nng lngts kt hpca

qu trnh quang ha v mtngunnng lng bn ngoi), trong nitrifiers s dng mt nguncarbon hu cv mt ngun e v c.Mixotrophys lm gimngknng lng- chi phtnghpt bo, do lm tng Y v . Cc trng hp tng trng mixotrophic cho thygi trgia tngca Ynet v , nhng khngphittc cc kt qul chc chn. Hn na, s trao initrifiers khng c nhimt sinh vt d dng l cc kkh khn. Mc d mixotrophy khngth gim, khinghin cuk, qu trnh nitrat ha s phn ng theo mt kiu ph hpvi s tdng ng ha hon ton.

1.2Qu trnh Nitrate ha bn hot tnh1.2.1Qu trnh nitrat ha bn bcmt

- L qu trnh trong vi khund dng v vi khun nitrat cng tn ti trongmt hn hpng nht, ti oxy ha ngthi amoni v BOD hu c. Bn bc mt cha cc VI KHUNnitrat ha v sinh vt d dng, thc hin ng thi s chuyn ha.


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Low BODLowNH4

+

BODo High NO3-

TKNo

Areation

Sludge recycle Sludgewaste

C mtbphn ng v mt b lng cho cc loi sinh khi .Nitrat ha one-sludge cn gi lnitrat ha bn mt giai on, bi v n ch c mt giai on phn ng. Chng ta s dng thutng one sludge nhn mnh mi quan h sinh thi gia VI KHUNnitrat ha v sinh vtd dng: chng hin cng nhau trong one sludge, hay mt nhmVI KHUN)Thit k bn bc 1Chng ta thit k s b h thng nitrate ha bn bc 1 cho nc thi c nhng c im sauy:Q=500m3/dBODL

o=500mg/lTKNo=60mg/lInertVSSo=25mg/lT=150C

Ch rng nng np vo c biu dinbng TKN, thay v NH4+N. Nc thi thng gm1 phn ng k lng nit dng khnhnit hu c. Trong hu ht cc giai on ca qu trnhnitrt ha, nit hu c thy phn thnh NH4

+N, hp cht cn cho qu trnh nitrt ha. Do vy,i lng o chnh xc lng nit dng khca dng vo phi l TKN, khng phi NH4

+N.u tin ta phi chn gi tr . V [min]limqu ln cho qu trnh nitrt ha, chng ta ch sdng mt gi tr xp x cho qu trnh. Bng 9.1 v 9.2 cho bit rng [min]lim xp x 2 d T =15C. p dng mt h s an ton l 10 ta c:= 10 x 2 d = 20 d.

Th 2, ta tnh ton nng trng thi cn bng ca BODL, NH4+N, NO2

-N t cc thng sng lc hc c bn.

BODL = 10

= 0.34 mg BODL/l

NH4+

= 0.57

= 0.18 mg NH4+ -N/l

NO2

--N= 0.62

= 0.17 mg NO2N/l

Aerobic BOD

OxidationNitrification > 15 days


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Th 3, tnh ton sn phm VSS c lng ca tt c cc dng sinh khi . Ta bt u vi cc qutrnh d dng hiu kh.

=

. 10-3

= 52.5 kg VSS/d

i vi qu trnh oxi ha NH3ta cn iu chnh lng S0 tnh ton lng NH4

+-N ng hatrong nhng sinh vtd dng hiu kh. l gi tr NH4+- mc nits dng trong qu trnh nitrt ha (mg N/l). do vy, mt phnln lng TKN u vo b ng ha thnh sinh khi d dng, ch khong 80% trong s bnitrt ha (tt nhin lng nh ny ph thuc vo SRT v t l ca BODL dng vo). Sn phmVSS c lng dng cho oxi ha ammoni l:

=

. 10-3

= 3.9 kg VSS/d

Da vo ha cht to thnh v gi tr TKN ca dng thi, ta thy lng sn phm ca qu trnhoxi ha ammonium l rt t so vi cc qu trnh d dng. l mt trng hp c trng, c

bn.Trong oxi ha nitrt, ta lp li cc qu trnh ging nh vi oxi ha ammonium, No2 l gi trNO2

-N s dng cho bc 2 ca qu trnh nitrt ha 103/5000.18

= 45.8 mg NO2N/l

=

. 10

-3

= 0.95 kg VSS/dVSS tr i qua VSSi/d

Tng s VSS ra khi h thng cui cng l:

tng = 52.5 + 3.9 + 0.95 + 12.5 = 69.8 kg VSS/dTh 4, ta tnh nhu cu oxi tng ng cho sinh khi trng thi cn bng. Ta b qua SMPtrong v d ny n gin ha phng trnh v trong tnh ton. SMP gm c nhu cu oxi vnhu cu oxi gim.

ng lng oxy u vo:= 500 m3/d . *

+ . 10-

3

= 404.9 kg OD/dGii c ng lng O2 u ra:= 500 m3/d .

*

+ . 10-3

= 0.68 kg OD/d


13/36

ng lng O2u ra:

= 1.42

. 12.5

+ 1.98

( 52.5 + 3.9 + 0.95

)= 131 kg OD/dTrong vic tnh ton khi lng oxy u ra tng ng, gi tr 1.98 mg OD/mg VSS c

dng xc nh 20 e-/mol ca C5H7O2N trong C v 8 e- trong N. (c th hin trong phngtrnh C-2 trn bng 2.4). m lng N trong trng hp ny cn thit, v lng oxy u votng ng lng N gim. Lng VSS u vo v u ra l bng nhau. Ta s dng 1.98 mgOD /mg VSS, nh khi c s dng trong u vo v u ra.V vy, tng lng oxy cn thit l: = 404.90.68131 = 273 kg O2/d

Nm, ta phi tm tng th tch ca h thng. Nh thng l, ta chn nng VSS hay thi gianlu nc. Trong trng hp ny, ta chn Xv = 3.000 mg/L. Ta c:

V =

total

= ()

)= 465 m3

=

= 0.93 d hay 22 hVi trng hp c thnh qu trnh xl trong nc thi sinh hot(gn 1 d), iu ny lunto iu kin trong nitrat ha h thng bn bc mt.Cui cng ta thit k b lng cp 1 da trn vn tc dng v dng vt rn trong h thng hiukh, vn tc dng c c trng bi mt gi trn nh, 8 n 16 m/d (nhc li phn cc thams ti chng 6). Ta dung gi tr trung bnh 12m/d. Da vo tiu chun ny, nc mt trongb lng cn thit xp x (ta b qua phn vn tc ng k ca dng bn trong nc thi).

As = = 41.7 m2

Dng rn trong b hiu kh mrng c duy tr n nh, khong 70kg/m2-d (xem bng chng 6). tnh ton dng vt cht rn, ta cn mt sxc nh ca vn tc dng ti s dng,vn tc ny quyt nh nng ca cht rn di y.Xrv. Ta gi s X

rv=8.000 mg VSS/l. Lc ny, s dng phng trnh 6.14a:

Qr = Q

= 500 m3/d

= 286 m3

/d (hay R = 0.57)C Qr, ta c thxc nh c khu vc nc mt da trn dng vt cht rn.

As =

=

= 33.7 m2Vn tc dng chy trn kim sot trong iu kin ny As = 42m

2.1.2.2 Qu trnh Nitrate ha bn bc 2

- L qu trnh nitrat ha trit nhm gims cnh tranh gia sinh vtd dng v VI KHUN

nitrat habng cch oxy ha hu ht BOD huctrong giai onu tin, trong khi ammoniboxy ha trong giai on hai.


14/36

BODo Low BOD Low BOD

TKNo HighNH4- Low NH4+

High NO3-

Thng khBn tun hon

Hiu kh

AerationAeration

Sludge recycleSludge recycle Sludge

Sludge wastewasteBao gm hai h thng bn hot tnh han chnh. V sinh khi trong mi giai on c gi liv hon li, mi giai on pht trin sinh khi ring ca n.Thit k bn bc 2Thit k s b h thng nitrate ha bn bc 2Bc u tin, ta chn qu trnh nitrate ha bng cch s dng x. ta chn 4d, mc bnh thngkhng cho php nitrate ha. Kn, ta tnh ton lng bn, nhu cu oxy v kch thc theo mhnh v d trn (V ln na, ta li bqua SMP n gin ha)

BODL = 10

= 0.84 mg BODL/1 = 500(5000.84)0.45

x 10

-3

= 86.6 kg VSS/d = 500 . 25 .10

-3 = 12.5 kg VSSi/d

tng = 86.6 + 12.5 = 99.1 kg VSS/dNp vo O2ng lng = 500 *

+. 10-3

= 267.8 kg OD/dSn xut ra O2ng lng = 500 . 0.84 . 10

-3 + 99.1 . 1.42

= 141.1 kg OD/d

- Gi nh Xv= 3,000 mg VSS/l c lng V v :V =

103

= 132.1 m3

= 132.1/500 = 26 d (6.3 h)

Aerobic BODoxidation = ca. 5 days Nitrification> 15 days


15/36

i vi mt nng ti lng,

- = 12.5 m2- t Xrv = 10,000 mg/l v GT= 140 kg/m2-d.

Qr = 500

= 200 m3/dR = 0.4As = = 15 m2

- Trong trng hp ny, As = 15m2- i vi giai on th hai, gi nh rng s oxi ha BOD v s tng trng d dng l

khng ng k. y l mt s n gin ha ng k, bi v (1) giai on th hai c sinhvt d dng hot ng v SMP t giai on u tin thi ra, v (2) nhng sinh vt nitrateha trong giai on th hai sn xut SMP to thun li cho s pht trin cho i sng ddng.Tuy nhin, nhng bin i ny yu cu mt s gi nh quan trng v cc yu tkhng chc chn, c bit l thc hin ca cc cht rn d bayhi v s hnh thnh SMP

bi nhng sinh vt nitrate ha. B qua nhng yu t ny c th to s nh gi thp caXv, iu ny nh hng n khi lng ca h thng v khu vc nh c.

- t = 20d cho giai on 2 SRT. NH4+ -N v NO2- -N cn li tng ng 0.18 v 0.17mg/l. Nh trc y, chng taphiiu chnh cc TKN u voa vo N ng hathnh sinh khid dngtrong giai on u v gii thot ts suy gim sinh khiddngtgiai on u tin l 0,52 kg NH4+ - N / d (tnh ton sau v c s dng y).

- S oxy ha ammonia :N01 = 6086.6 . 0.124.10

3/500 + 0.52 . 103/500= 6021.5 + 1.1 = 39.6 mg NH4

+ -N/1

=500 . (39.60.18). 0.33 . . 10-3

- S oxy ha nitrite:N02 = 6020.40.124 . 3.3 . 10

3/5000.17 = 38.6 mgNO2N/1 =500 . (38.60.17). 0.083 .

. 10

-3

=0.80kg VSS/d- Gi nhrng 20mg VSS/l khngb loi b tronggiai onu tin vbc vo giai

onth hai, n cha 80% sinh khihot ng, v sinh khihot ng ny phn r vimtt l l 0,1 / d.T l u vo l:

( = 0.2 x 20 x 500/1,000 = 2 kg VSS i/d(

= 0.8 x 20 x 500/1,000 = 8 kg VSSa/d

- Vi 20-d SRT, phn r u vo sinh khi hot ng cn li Xa, sn xut Xinhiu hn, vsinh ra NH4 + - N

( d =

= 2.7 kg VSSa/d

( tng=0.2(8 2.7) = 1.1kg VSSi/d

- V vy,

d= 2+ 2.7 +.1 + 5.8 kg VSS/d

- Lng VSS tng cng phi c giai on 2 l: = 5.8 + 3.3 + 0.80 = 9.9 kg VSS/d


16/36

- S gia tng NH4+-N dophn hy casinh khid dng l:(

tng=0.124(8 2.71) = 0.52kg NH4+ - N/d

- Lu y rngVi sinh vtnitrate ha hot ngkhong mt phn ba VSS tng, mcd b qua cc u voca BODtcht nnhoc SMP. iu ny cho thyrng giaionth haithngc hon ton thc hinbiVi sinh vtnitrate ha.

- Lng oxy cn thit c tnh nh sau:u vo O2tng ng = 500[4.57 . 39.6 + 1.42 . 4 + 1.98 .16] . 10

-3=109 kg OD/d

Sn lng O2ha tan tng ng =500[4.57 . 0.18 + 1.14 . 0.17] . 10-3

Sn lng O2rn tng ng=1.42 . 2 + 1.98 . (2.7 + 1.1 + 3.3 + 0.8)=18.5 kg OD/d

- Do , Tng lng O2cn cho giai on 2 l: =1090.518.5 = 90 kg O2/d

- tnh ton khi lng tng th cho giai on th hai, gi nh MLVSS tp trung. Vicsn xut thp VSS ni chung ngn chn c cc gi tr tiu biu khi cc vi khun ddng chim u th.V vy, chng ti gi nh rng Xv = 1.000 mg / LL. Sau ,

V=

(9.9).103 = 198 m3

V

= =0.40d(hay 9.5h)- i vi b lng, s dng cc gi trsc khmrngtl trn v thng lngcht

rn.Vi t l trn 12 m / dAs=

=41.7 m

2

- Thng lng cht rn c th c s dng sau khi gi nh mt gi tr X rv 5.000 mg / L:Qr = 500

= 123 m

3/d

V R = 0.25

As=

= 8.9 m2

- Mt ln na, kim sott l trn, As = 42 m2Bng 9,3 so snh one-sludge v two-sludge tv d 9.1 v 9.2.N th hins cn bngtng hpgia haiphng php .H thng one-sludgebn thi t hn, SRT cho BOD oxi-dation ln, nhng nhu cu oxyca n ln

So snh thit k bn bc 1 v thit k bn bc 2

H thng bn bc 1 c t bn thi hn, v thi gian lu bn cho oxi ha BOD ca n ln,nhng nhu cu oxy ca n ln hn

Table 9.3 So snh one-sludge v two-sludge t v d 9.1

Tham s one-sludge two-sludgeGiai on 1 Giai on 2 Tng


17/36

x, d 20 4 20Lng chtthi rn, kgVSS/d

69.8 99.1 9.9 99*

Lng oxy

cn thit, kgO2/d

273 127 90 217

Th tch, m3 465 132 198 330Din tch, m2 42 15 42 57

*Lng cht thi rn tng cng trong h thng bn bc 2t hn so vi tng ca giai on 2, v10kg/d t giai on 1 l chuyn giao cho giai on 2, ni n phn r hu ht.Nh vy, 10 kg / dc tr vo tng s loi b s tng gp i

- Tng th tch hthng bn 1 ln hn, mt ln na do SRT di cho nhng sinhvt d dng

1.3 Mng sinh hc qu trnh Nitrate ha

Tt c cc qu trnh mng sinh hc hu ch cho qu trnh oxy ha hiu kh BOD cng c thc s dng thc hin qu trnh nitrat ha, min l thit kca quy trnhthch hp tc tng trng chm nht nhvn c ca vi khun nitrate ha v s cnh tranh gia vi khunnitrate ha v Vi sinh vt d dng v oxy v khng gian sng.Cc thng s ca qu trnh nitratha tiu biu c lit k trong bng 9,4.

Bng 9.4Cc thng s c bn vc ngun gc t qu trnh oxy ha NH4+ - N

Tham s Gi tr

Cht nn hn chY,mg VSSa/mg NH4+ -N

q,mg NH4+ -N/mg VSSa/d

K,mg NH4+ -N/l

b, 1dbdet, 1d

b, 1dx, dD, cm2/dDf, cm

2/dX

f,mg VSS

a/cm3

L, cmSmin, mg NH4

+ -N/lS*minK*JR, mg NH4

+ -N/cm2-d

NH4+

-N2

0.331.70.570.080.0530.13201.31.04100.0040.170.301.850.072

Ghi ch:1. Gi tr chung cho T=15oC2. Cht nn hn ch l NH4+ -N, trong gi nh rng bc u tin ca qu trnh nitrat

ha l hn ch.


18/36

3. Gi nh rng vi sinh vt nitrate ha tn ti ch yu l su bn trong mt mng lc sinhhc trnh b tch ri.

- Hnh 9.2 trnh by ng cong sc ti in hnhcho cc vi khun nitrate ha v ch ra rngqu trnh nitrat ha mng sinh hc thnh cng nhthot ng trong khu vc chuyn tip gia ti

trng thp v ti cao, c ngha l, J / JRt:0.2 n 1.1 ( xem li phn tiu chun ha sc chab mt trong chng 4). Bi v Sminrt nh (0.17mg NH4

+-N trong bng 9.4). Khong phm visccha tiu chun chung lm cho t l S/Sminc gi tr t 1.6 6 gi cho S phi nh hn1mg NH4

+-N/l.

Hnh 9.2Kt qu th nghim v kinh nghim cho thy Vi sinh vt nitrate ha c xu hng tp trung nhiuhn b mt dnh bm, trong khi Vi sinh vt d dng chim u th pha pha ngoib mtca mng sinh hc. S phn chia ny l h qu tt yu ca mc tng trng nhanh hn cavi sinh vt d dng, cho php chng tn ti n nh ti nhng vng xy ra s tch ri ln camng sinh hc. Mt khc, Vi sinh vt nitrate ha tp trung su bn trong mng sinh hc, nich 1 phn nh c bo v khi s tch ri.Vic cc Vi sinh vt nitrate ha su pha trong mng sinh hc, gip chng n nh s pht trinchm, chng li s ra tri, ncn lm tng s nhy cm ca chng i vi lng oxy, v oxyha tan phi khuch tn qua lp vi sinh vt d dng trc khi n vi Vi sinh vt nitrate ha.Khi iu ny kt hp vi nhy vi lng oxy tng i cao ca Vi sinh vt nitrate ha (vd:Ko=0.1mg/ l cho nhiu sinh vt d dng trong khi n khong 0.5 mg/l cho vi sinh vt Nitrtha), s c th v hiu nhng li ch ca s bo v, tr khi nng D.O trong cht lng cduy tr cao. V d nh, Furumai v Rittmann (1994) m t s gim st trong s lng vi sinhvt Nitrt ha v gia tng trong nng NH4+ -N v NO2- cho ra khi tng nng D.O. gimxung khong 3 mg/l, ngay c khi nhng vi sinh vt Nitrt ha c bo v su bn trongmng sinh hc. Gi lng ti b mt thp s c th loi b nhng tc ng xu ca s cn kitD.O.Trong thc t, p t mt lng ti b mt ti a BOD hoc COD, trong khong t 2 n 6 kg

BODL/1000 m2-d, s kim sot s cnh tranh bi sinh vt d dng. Gi lng ti hu c di2 n 6 kg BODL/1000 m

2-d s cho php ta gi mt nng D.O. lng va v ngn chn tc


19/36

nghn va, chp mch, trc b v/hoc nhu cu cho vic bm ngc qu mc bi qu nhiutng trng d dng. 2 nguyn nhn trn c th dn n tc tch nhanh n mc cc vi sinhNitrt ha khng bao gi thit lp c nhng lp bo v v b cun tri.Bng 9.5 tm tt thnh cng lng ti b mt ca N v BODLc s dng cho nhiu quytrnh khc nhau trn mng sinh hc, c cp trong chng 8. Phm vi ca lng ti N v

BODL l tng i hp. Lng ti ca BODL cho qu trnh nitrate ha gi ln lng ti BODLs dng cho qu trnh oxy ha hiu kh nghim ngt. iu gii thch ti sao cc qu trnh trnmng sinh hc, s dng ch yu cho oxi ha BOD thng l qu trnh nitrate ha, min l mtti BOD nm trong phn di ca phm vi thng. Bi v N hu c thng c thy phn cho ra NH4

+-N, lng ti N nn c biu hin bng TKN ch khng ch NH4+-N.

Khi m lng BODLtrong nc thi: TKN c t l qu ln cho php 2 lng ti b mt tiuchun t n cng mt lc, liu php bc c th c s dng lm gim lng ti BODcho qu trnh nitrate ha. My lc tia 2 giai on l 1 v d tt. Giai on thng trong RBCs lmt v d khc, bnh thng, s nitrate ha din ra trong giai on sau ca RBCs, sau khilng BOD gim trong nhng giai on trc. S gim sinh trng ca Vi sinh vtd dng

trong giai on nitrate ha ca RBCs cho php mt cht trung gian c s dng ti aha din tch b mt loi.Bng 9.5: Lng ti nito v BOD c s dng thnh cng trong cc qu trnh nitrat hakhc nhau trn mng sinh hc.Loi qu trnh Sc ti nito b mt

kgN/1000m2-dSc ti BOD b mtkgBODL/1000m

2-dMng lc nh git(trickling filters)

0.5-0.8


20/36

Th nh, chng ta thc hin thit k 2 bc. Chng ta bt u vi Oxi ha BODL. T Chng 8chng ta chn mt mt ti tng i ln l 7 kg BODL/1000 m

2-d. iu ny cho ta din tchbc mt l:A1 = (300 kg BODL/d)/(7 kg BODL/1000 m

2-d) = 4,3 * 104 m2Sau ta tnh din tch cho bc Nitrt ha th 2. Trc khi ta tnh din tch, ta phi iu chnh

lng ti TKN gii thch cho N c s dng trong tng hp d dng trong bc u.Lm theo phng php trong V D 9.1 v 9.2, ta s c mt php tch chnh xc , min l tc tch c c lng. Cho v d ny, ta gi nh rng mt mt ti t thn trng hn: 0,8 kg N/1000 m2-d (bng 9.5) v tnh din tch bc 2:A2 = (40 kg N/d)/(0,8 kg N/1000 m

2-d) = 5 * 104 m2Tng din tch b mt cho c 2 bc l 9.3*104 m2, iu gip ta tit kim thm mt din tchso vi bc 1. V mt khc, ta phi thit k, xy dng, v thc hin 2 h thng khc nhau.

1.4 Vai tr ca t s BODL/TKN:Qu trnh nitrate ha chu nh hng ca t s BODL/TKN theo ba cch. Th nht, nh cminh ha Vd 9.1 v 9.2, y l mt qu trnh ng ha to ra sinh khi d dng c thu nhn

nito, v gim lng nito trong ammonium to ra nitrite v nitrate. Nu BODL/TKN ln, tcl ln hn 25 g BODL/gTKN th lng nito to ra t ammonium s khng c cung cpcho qu trnh nitrate haTh hai, BODL/TKN xc nh hm lng sinh khi hot tnh gm cc Vi sinh vtnitrate ha. Vgi tr fS

0 thp ca cc Vi sinh vtnitrate ha, nn khi lng sinh khi to thnh ca chngcng thp. T s BODL/TKN c trng ca nc thi th khong t 5 n 10g BOD L/gTKN-kh thp, nn lng Vi sinh vtnitrate ha cng t hn 20% sinh khi hot tnh v mt phn nhhn ca VSSCui cng, BODL/TKN tc ng kim sot s cnh tranh cc ngun oxy ha tan, ch trn flochay mng biofilm ca sinh vt t dng v Vi sinh vtnitrate ha vi nhau. Trong thi gian di,

t s BODL/TKN cao buc cc Vi sinh vtnitrate ha phi xung su hn trong floc haymng biofilm. iu ny lm cho cc cht nn ca cc Vi sinh vtnitrat ha phi chu mt skhng c vn chuyn sinh khi ln hn, c th l NH4

+ v O2 (Rittmann and Manem, 1992) .Trong thi gian ngn, tc sinh trng mnh ca cc sinh vt d dng c th to ra nhhng xu n cc Vi sinh vtnitrate ha nh cnh tranh nito, tiu th oxy hay s ginh ch trnfloc v mng biofilm.

2. QA TRNH PHN NITRATE HAKh nitratel qu trnh kh nitrate (NO3

-) hay nitrite (NO2-) thnh kh N2. Hay ni cch khc

NO3- hay NO2

-ng vai tr nh cht nhn e trong qu trnh h hp m bo v khai thc nnglng. Qu trnh kh nitrate c th c thc hin bi c vi khun t dng v d dng. Nhiuvi khun hiu kh c kh nng chuyn t t, qu trnh trao i cht theo kiu oxy ha (c stham gia ca oxy) sang dng s h hp nitrate.Trong cng ngh sinh hc mi trng, qu trnh kh nitrate c ng dng khi c yu cu loi

b hon ton N.V d quan trng l x l nc thi ra lu vc sng lm gim nguy c ph dng; x lcht thi N, nh nc t nng nghip v nc thi t ni nui gia sc; v x l nc ung cnng NO3

- + NO2-cao, bng cch c th gim s nguy him n tr em. Trong tng ng

dng ny, N c th ha tan v bin i thnh kh N2, v tr li kh quyn. c qu trnh khnitrate, N phi l cc dng oxy ha ca n, NO3

- v NO2-.

V nhiu nc thi chaN dng kh, qu trnh kh nitrate ha xy ra ng thi vi qu trnhnitrate ha, cn to N dng oxi ha.

2.1Cc vi khun tham gia qu trnh phn Nitrate ha


21/36

Pseudomonas Alcaligenes

Paracoccus Thio-bacillusQu trnh phn nitrate ha ph bin trong t nhin. Vi khun phn nitrateph bin l vi khungram m Proteobacteria, nh Pseudomonas, Alcaligenes, Paracoccus, v Thio-bacillus. 1 s vikhungram dng, c th kh nitrate, bao gm Bacillus. Thm ch 1 vi thc vt a mnArchaea, nh Halobacterium, cng c th kh nitrate. Tt c cc vi khunkh nitrate l vi sinhvt hiu kh ty nghi, c ngha l chng thay i s h hp nitrate hoc nitrite khi gii hn nng O2.Vi khunphn nitrate c s dng trong cng ngh sinh hc mi trngc tnh hng hacht, c th s dng ngun e t cht v c hoc hu c. Nhng vi sinh vts dng ngun e vc l sinh vtd dng v ph bin l Proteobacteria. Mt nhm t sinh vtt dng c th tn

dng H2v S dng kh. Bi v chng to nn tnh trao i cht a dng. Vi sinh vt phn nitratethng c tm thy trong t, trm tch, nc b mt, nc ngm, nh my x l nc thi.Qu trnh kh nitrate ha thc hin theo tng bc, trong gim tun t t NO3

-NO2

-NON2ON2.

Mi bn phn ng v enzyme xc tc c th hin bn di:NO3

- +2e+2H+NO2-+H2O Enzyme: nitrate reductase

NO2-+e+2H+NO+H2O Enzyme: nitrite reductase

2NO+2e+2H+N2O+H2O Enzyme: Nitric Oxide reductaseN2O+2e+2H

+N2+H2O Enzyme: Nitrous oxide reductase

Nng Oxy kim sot h hp hiu kh ty nghi N. Oxy kim sot qutrnh phn nitrate theo 2

cch:+ u tin l ngn chn mt vi enzyme nitrogen-reductase. Nghin cu vi Pseudomonasstutzeri cho bit nhng enzyme ny b kim hm bi nng DO ngoi 2.5 n 5mg O2/l.+ Th 2, c ch kim sot l hn ch s hot ng ca enzyme kh nitratebi nng DO lnhn 1/10 mgO2/l.Thc t l nng DO kim hm loi enzyme reductase cao hn nhiu l kim ch hat ngca chng, ngha l qu trnh nitrate ha c th xy ra khi nng DO trn O. Tnh hnh nyc nng cao khi vi khunphn nitrate c t bn trong flocs hoc mng sinh hc, ni mnng oxy thp hn trong cht lng (Rittmann and Langeland, 1985)

Nng ngun e rt thp hoc nng DOqu cao c th dn n s tch ly trung giangia NO2-, NO2, N2O. 2 cht sau l kh nh knh, cn ngn nga s gii phng 2 cht . Nng


22/36

thp ca ngun cho e hn ch cung cp e n bn phn ng kh. Nng O2 cao c khuynhhng kim hm enzym nitrite v nitrous oxide reductase trc khi enz nitrate reductasebkim hm.Mc d vi khunphn nitrate khng nhy cm vi pH, gi tr pH ngoi phm vi ti u(7 n 8)dn n s tch ly cht trung gian.Trong nc kim thp, cn thit phi kim sot pH (tng

pH), v sn phm qu trnh phn nitrate ha bn bazo. S sn sinh bazo c minh ha bi phnng cn bng khi acetate v H2l cht cho e cho vi khunt dng hoc d dngCH3COOH+8/5NO3

-+4/5H2O4/5 N2+2H2CO3+8/5 OH-

4H2+8/5NO3-4/5 N2+8/5 OH

-+16/5 H2OTrong c 2 trng hp, kim ca nc tng bi to ra 8/5bazo mnh trong khi mt 8/5 molNO3

-tng ng.Bng 10.1 Biu din ha hc lng php v cc thng s ng hc ca vi khun khNitrateCht cho e Methanol BOD H2 S

oNgun C Methanol BOD CO2 CO2

fs0

0.36 0.52 0.21 0.13Y, g VSSa/g donor 0.27 0.26 0.85 0.10gVSSa/g OD 0.18 0.26 0.11 0.07

q^, g donor/g VSSa-d 6.9 12 1.6 8.1g OD/g VSSa-d 10.4 12 11.8 11.2

K, mg donor 9.1 1 1 ?Mg OD/l 13.7 1 0.13 ?

b, d-1 0.05 0.05 0.05 0.05[]lim 0.55 0.33 0.76 1.3Smin, mg donor/1 0.25 0.017 0.04 ?

Smin, mg OD/1 0.38 0017 0.005 ?D, cm2/d 1.3 1.0 0.9 _JR, kg OD/l,000 m

2-d 1.5 0.5 1.2 ?S*min (no detachment) 0.027 0.017 0.040 0.066

(bdet=0.2/d) 0.15 0.087 0.23 0.45K* 1.8 0.4 2.2 ?Bng 10.1 m t nh lng v thng s ng lc ( 20oC) cho sinh vtd dng s dng khmethanol, cc vt liu hu c khc, H2, S c bn nh 1 cht cho e cho qu trnh kh nitrat .Bng 10.1 s dng nhiu khi nim hu ch ca OD. OD tng ng vi khi lng ca cht choe th hin tng ng vi oxy. N tng t nh khi lng ca O2cn thit oxy ha honton cht cho e. 8 gr OD bng 1e-. Cht cho e hu c, OD bng vi BOD

L.

Gi tr bng 1a n quan st v vi khun kh nitratv nn lm th no cc qu trnh lin quann qu trnh kh nitrat thc hin

1. Khi gi tr fo sinh vtd dng s dng BOD chung ch hi nh hn f0sinh vtd dnghiu kh ( khong 0.6 e tng hp/ e cht cho), gi tr f0sinh vtt dng th nh hnnhiu, tng t nh vi khunnitrat ha. Gi tr f0sinh vt oxy ha C bc 1 tiu thmethanol th thp hn nhiu vi sinh vtd dng khc.

2. Khi gi tr v b tng t nhau (cf 12g OD/g VSSad v 0.05/d), limc kimsot ch yu bi Y

3. Gi tr Sminthp hn 1 mg DO/L, c ngha BOD cn li cao trong dng thi khng phil 1 vn c bit.


23/36

4. Qu trnh mng sinh hc, tt c cc vi sinh vtcho thy tim nng tng trng cao (Sminthp) khi tch ri l khng ng k. Mt khc, qu trnh t dng c th hn ch tc tng trng nh bdettng.

5. Gi tr K* cho qu trnh mng sinh hc l khng ln. C ngha bn ngoi khi lng vnchuyn kim sot thng lng cht nn khi ti mng sinh hc trong khu vc trung bnhhoc cao.

Tm li, sinh vtd dng c nhng c im tng t nh sinh vtd dng hiu kh. Biv chng l hiu kh ty , chuyn t h hp O2sang h hp NO3

-hoc NO2-gy ra ch gim

nh fov Y, ch tng va phi lim V th, qu trnh kh nitrate nn thc hin tng tnh qu trnh hiu kh s dng loi b BOD.Mt khc, c im ng hc ca vi khunphn nitrate d dng v vi khun nitrate tdng l rt khc nhau. Vi khun nitrate ha c gi tr fothp, tng chm hn v v cn bnyu cu thi gian lu cht rn lu hn. Hn na, t l qu trnh nitrate ha ti a yu cunng DO cao, trong khi nng DO cao lm chm hoc dng qu trnh kh nitrate ha.V qu trnh nitrate ha cn thit cungcp NO3-hoc NO2-cho qu trnh kh nitrate ha,qu trnh hot ng v thit k phi iu ha nhng c tnh sinh l xung t. l viciu ha nhucu ca vi khun nitrate ha v phn nitrate ha d dng phn bit cc

phng php tip cn khc nhau kh N trong cng ngh sinh hc mi trng.1 c im quan trng ca vi khunphn nitrate ha l s dng NO3

-hoc NO2-nh ngun

N cho tng hp t bo. Tng s mt in tgim ngun N n trng thi oxi ha -3 lmgim f v nng sut tht. V d, s dng NO3

-nh ngun N yu cu thm 8 e tng ngmi mol ca sinh khi, i din nh C5H7O2N. nh trong bng 2.4, C5H7O2N yu cu 20 e oxihoa1 C n trng thi 0 trong tt c cc t bo (phn ng C1), nhng yu cu 28 e oxy ha C v N khi ngun N l NO3

-(phn ng C-2). V th, khi NO3-l ngun N, oxy yu

cu cho sinh khi l (28e eq/mol cells) (1 mol cells/113 g cells) (8 g O2/e- eq)=1.98 g OD/gcells, khng phi 1.42 g OD/g cells..

2.2Qu trnh kh Nitrate bc 3Qa trnh kh nitrat c th chia thnh 2 loi chnh: x l bc 3 vi bn bc 1. iu khc bitgia 2 loi da vo vic c cho thm cht cho in t ngoi sinh hay khng. Kh nitrat bc 3i hi s thm vo ca cht cho in t ngoi sinh, trong khi bn bc 1 s dng cht choin t c sn trong nc thi.Kh nitrat bc 3 th thch hp cho bt c loi nc cn x l c cha NO3

-hoc NO2-. Kh

nitrat xy ra trong t nhin nhng vng nng nghip b nhim phn m, ngun cung cpnc ung nhngvng nng nghip ny cha nng NO3

-cao nhng rt t cht hu c.

Kh nitrat bc 3 xy ra sauqu trnh sinh hc hiu kh ca nc thi. Trong x l bc 2 th tt ccc gc cho in t c mt c oxi ha hon ton, cc hp cht cha nito c oxi hanNO3

-, trong khi cc hp cht cacbon b khong ha. Kt qu ca x l bc 2 l N b chuynthnh NO3

-nhng khng c cht cho in t. Trong thc t kh nitrate bc 3 theo sau x l bc2.Cc cht hu c thng thng c cho vo qu trnh nh nhng cht cho in t, Chng lmtng s tch ly ca sinh vt d dng (lm tng sinh khi). Trong gii hn sinh hc v ng lchc sinh vt kh nitrat d dng rt ging vi sinh vt d dng hiu kh s dng oxi haBOD. Tuy nhin c mt s khc nhauln l qu trnh kh nitrat khng i hi ngun cungcp oxi. S khc nhau lm gim nhng nguyn tc kht khe trong qu trnh hiu kh

Hu ht cc hp cht hu c u c th c s dng nh nhng cht cho in t ngoi sinh.Trc y methanol c chn v n c li v kinh t ch khng phi n tt hn nhng cht


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cho in t c chn khc. Khi c s tp trung sn nhng cht hu c trong nc thi thchng c s dng nh mt cht cho in t r tin. dng nc thi t qu trnh ch bin thc

phm v sn xut ung th thng c s dng nht bi v chng cha nng BOD cao(hn 10000mgBODl/L) v t l C/N cao. Vi t l C/N cao ,thc tnh ca ngun carbohydratl cung cp mt lng ln in t, nhng li gii phng ra 1 t N dng kh. Trong khi mc

ch ca qu trnh kh nitrate l loi b ht N trong nc, v th vic thm vo N dng kh s isai mc ch.Cc hp cht v c cng c s dng nh mt cht cho in t v ngy cng ph bin. Kh H2l cht cho in t rt tt cho qu trnh kh nitrat t dng. Chng c nhng u im nh: snxut sinh khi thp hn so vi d dng v hon ton khng thm vo N dng kh. Nhc imchnh ca kh H2l thiu an ton cho h thng chuyn ha Hydro. Trong nhng nm gn yvic pht trin ra thit b mng phn hy th khc phc c mi nguy him thng gptrong chuyn ha kh v lm cho H2tr thnh s la chn hng u.Sulfua dng kh cng iu khin qu trnh kh nitrat t dng. thng thng nht th ngun Sdng kh l S v chng b oxi ha n SO42-. Thng thng th S c gn vo cht nn rn

chng bao gm cht rn di y nh CaCO3, bi v oxi ha S xy ra trong acidmnhS(s)+6/5NO3-+2/5H20SO4

2-+3/5N2+4/5H+

Ha hc lng php ca phn ng kh nitratPhi hp 3 qu trnh Nitrate ha khc nhau c kim tra: d dng s dng methanol nh chtcho in t , d dng vi cht cho in t l acetat v t dng vi H2 nh cht cho in t.T bng 10.1 chng ta s dng gi tr fos ln lt l 0.36;0.52 v 0.21. Mi phn ng th chot ng vi mt SRT ca 15d. Chng ta c th tnh ton cho tt c nhng phng trnh hahc lng php cho mi h thng di nhng iu kin khc nhau

- Th nht mi h thng c gi tr fs v fering nhn c t cng thc :

khi b=0.05/d v fd=0.8 cho tt c cc h thng, th ta tnh cPhn ng fs feD dng vi methanol 0.267 0.733D dng vi acetate 0.342 0.658T dng vi H2 0.137 0.862

- Th hai cc bn phn ng c lin quan th:T bo s dng NO3- nh ngun N

1/28NO3- +5/28CO2+29/28H+ =1/28C5H7O2N +11/28H2O+ cht nhn in t

1/5NO3- +6/5H+ +e- =1/10N2 +3/5H2O+ cht cho e:

Methanol1/6CO2 +H+ +e- =1/6CH3OH +1/6H2O

Acetat1/8COO2 +1/8HCO3- + H+ +e- = 1/8CH3COO- +3/8H2O

Kh H2H+ +e- =1/2H2

- Th ba:cc bn phn ng c kt hp theo:R= -R(cht cho) +feR(cht nhn) + fsR(t bo)

D dng vi methanol


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0.1667CH3OH + 0.1561NO3- +0.1561H+ =0.00954C5H7O2N + 0.0733N2 +0.3781H2O + 0.119CO2

D dng vi acetat0.125CH3COO- + 0.1448NO3- + 0.1438H+ = 0.0122C5H7O2N + 0.658N2 +0.125HCO3- + 0.0639CO2 + 0.1542H2O

D dng vi kh H20.5H2 + 0.1773NO3- + 0.0246CO2 + 0.1773H+ = 0.00493C5H7O2N + 0.0862N2 +0.5714H2O

Bng tm tt 10.2 th a ra nhng ha hc lng php c bit ca phn ng, qua bng thta cng bit c khi lng sinh khi sinh ra ca qu trnh kh nitrat c biu din qua gi trfs, t l gia VSS(sinh ra)/NO3-(tiu th), hoc t l gia khi lng VSS(sinh ra)/OD(tiu th)v n suy gim ng k t acetat n methanol n kh H2. Mt xu hng khc l t 4.3 n13% in t ca NO3-_N tiu th c s dng nh ngun N cho qu trnh tng hp, t l lnnht c lin quan n gi tr fs ln nht.Bng 10.2 th cng ch ra 28.6% DO ca sinh khic u t vo vic kh ngun N 3 trng thi oxi ha

Nhng s liu trong bng 10.2 cng hng dn vic thit k h thng x l ph hp. V dqu trnh kh nitrat d dng vi acetat i hi phi cung cp khong 4g BOD cho mi gamNO3

--N . Ti thi gian th n sn xut ra khong 0.69g VSS ca sinh khi v 3.6g CaCO3catnh kim. Trc kia n c s dng xc nh t l bn thi ra, trong khi gn y n c sdng gii quyt nc c cha m thch hp.

2.2.1 Qu trnh kh Nitrate bc 3 vi bn hot tnh Qu trnh kh nitrat bc 3 vi bn hot tnh thng thng c s dng x l cho

nhng nc thi c cha nitrat. Cc m hnh x l c bn ging nh qu trnh x l hiu kh sdng bn hot tnh: b khuy trn, b lng bt hot, bn tun hon v bn thi kim sot thigian lu bn. Nhn chung SRT l khong 5 ngy tnh t thi im thm cht hu c cho in t.

Thi gian ny th lu hn so vi qu trnh kh nitrat t dng.(Bng 10.2)Bng 10.2Reaction Heterotrophic Heterotrophic AutotrophicType with Methanol with Acetate with H2

fs 0.267 0.342 0.138Electron equivalents in donor 1 1 1Electron equivalents in biomassTotal (=fs) 0.267 0.342 0.138

In C (=s) 0.191 0.244 0.099

In N (= s) 0.076 0.098 0.039NO3

-consumedMol 0.1561 0.1438 0.1773

e- eq as acceptor (=fs) 0.733 0.658 0.862e-eq as N source 0.076 0.098 0.039e- eq total 0.809 0.756 0.901Net H+ consumed

H+ equivalent 0.1561 0.1438 0.1773Key rations

g OD/g NO3N 3.66 3.97 3.22

g alk as CaCO3/g NO3N 3.57 3.57 3.57g VSS/g NO3

N 0.490 0.685 0.224


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g VSS/g OD (=Yn) 0.135 0.172 0.0696

Mc d qu trnh kh nitrat bng bn hot tnh ging vi qu trnh x l hiu kh nhiuim, nhng m hnh h thng c nhiu im khc nhau:

- Th nhtl b x l c thit k gim n mc ti thiu s thng kh. Mc d chtlng cha trong b rt cn s khuy trn nhng cn hn ch n mc ti thiu s tip xc vikhng kh. gii quyt vn ny th ngi ta thng khuy trn c cht bng tuabin chm.Trong 1 s trng hp th b phn ng c che kn, mc d cch ny khng c thng dng.

- Th haii hi s b xung cc cht cho in t. Mc d lng chnh xc cht cho int c th c tnh chnh xc bi ha hc lng php, nhng mt quy tc nht nh l4gBODL/g NO3- -N trong sut qu trnh kh. Cht cho in t cn phi c thm vo nu O2i vo h thng . Cht cho in t hu c c th c tng cng cung cp cho dng nc thi.H2 c thm vo tt nht cng vi mng bt ha tan. Cht S kh thm vo trong h thng llng,bi v n c cung cp di dng cht rn ha tan, ni chung sulfide (HS -), sulfite (SO3-), hoc thiosulfate (S2O32-) c th c thm vo di dng cht lng, nhng vic ny c kh

nng s lm tng nhanh vi khun dng si v lng ln bn.Thit k b lng th da vo nguyn tc nh trong qu trnh x l hiu kh. N c th xem stng bn l mt vn , tuy nhin s thnh cng ca qu trnh kh l lm gim nng caNO3- trong b phn ng Thit k c bn qu trnh kh Nitrate bc 3 s dng bn hot tnh

Mt dng nc thi 1000 m3/d cha 50mg/L NO3- -N, 2 mg/L O2, khng c lp cho in t.

Chng ta hon thnh 1 thit k s b m phn b sung acid acetic v 1 SRT 5d. Hn hpdung dch d bay hi v cht rn l lng c nng 2500 mg/L. Mc d s thng kh l nhnht, O2 c thm vo c nng 6 mg O2/L trong dng chy. (ch rng nu c s thngkh y , s thm hng trm mg/L O2vo dng nc.)

+ Th nht, chng ta phi tnh t l acid acetic, ci c thm vo kh nitrate v O2. Khifso

= 0.52 cho qu trnh kh nito vi acid acetic, x = 5d, b = 0.05/d, fd= 0.8, fs = 0.4368, lm nnphng trnh ca phn ng kh nito:0.125 CH3COOH + 0.1282 NO3

- + 0.1282 H+ =0.05632 N2 + 0.0156 C5H7O2N + 0.1720 H2CO3 + 0.0875 H2O

T phng trnh ny, ta thy t l acid acetic v NO3-cn cho phn ng:

= Bin i thnh n v khi lng:

.

.

=

V vy, ly i 50mg/L NO3-

-N cn 4.46 x 50 = 223 mg BODL/L acid acetic.O2cng b kh. Phng trnh cho phn ng hiu kh bao gmfso = 0.6,b = 0.1/d,fd = 0.8, vx

= 5d.0.125 CH3COOH + 0.14 O2 + 0.0157 NO3

- + 0.0157 H+ =0.0157 C5H7O2N + 0.1714H2CO3 + 0.0315H2O

Tphng trnh ny cho thy:

. =

Tphng trnh ny c ngha l acid acetic thm vo tiu th ht O2 l:

. (2 + 6 mg O2 / L) = 14 mg BODL/ LTm li, acid acetic phi c thm vo sinh ra 223 + 14 = 237 mgBODL/L trong dng chy.


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+ Thhai, t l bn sinh ra vn cn tphng trnh trn v gi s 100% acid acetic phn nghon ton, sn lng quan st c:

.

=

cho s kh nito v

. = 0.22 g VSS/ g BODLcho s oxi ha hiu kh. Tng sn phm VSS l:

. 1,000 m3/d . = 52 kg VSS/d

+ Thba, th tch ca h thng phi c tnh tx , t l sn phm VSS, v MLVSS cn:

V =

=

= 104 m3

Ti trng th tch (QSo /V) l 2,3 kg BODL/ 1,000 m3d, 1 gi trcao hn bnh thng c

dng trong bn hot tnh hiu kh. Mt ti trng thtch cao hn c thc hin, bi v hn choxy vn chuyn khng phi l vn . Tuy nhin, thit k b lng vn phi c xem xt v c

ththc y th tch ca h thng tng ln, ci cn cho MLVSS thp hn

x.Ch cui cng, acid acetic thm vo ca h thng. Tuy nhin, s kh nito tiu th t l H+ gnnh cn bng vi acid acetic. Do , s thm vo ca acid acetic s lm gim pH trong l phnng. Snh hng ca pH c thc tnh ton dng nguyn tc acid/base v xem nh linquan n h thng aacid/base yu.

2.2.2 Qu trnh mng sinh hcQu trnh kh nito l 1 trong nhng ng dng d dng nht trong phm vi rng ca x l mngsinh hc.

Mc d nitrate l cht nhim chnh, in t cho lun 1 t l gii hn. Do , thit kca h thng sinh hc cho s kh nito nn ph thuc vo dng ca lp cho. Bng 10.1 ch rarngJRca lp cho in t gn nh 1 kg OD/1,000 m

2-d. Tt nhin gi tr chnh xc ph thucvo lp cho dng v iu kin ca phn ng, nh t l tch ra v nhit . S hot ng khcca h thng sinh hc l gi trJca lp cho hu c t 15 n 22 kg BODL/1,000 m

2-d thngdng l vic cn thit loi b nit v nng BOD c th chp nhn c trong nc thi.Dng H2nh 1 in t t dng tch NO3

-cho dng chy l 25 kg OD/1,000 m2-d, tngng 3.1 kg H2/ 1,000 m2-d. Bng t l ny, dng NO3

-(kg N/1,000m2-d) bng 1/3 n gi trca dng cho.

Hu nh cc h thng sinh hc hot ng tt cho s kh nito, min l oxy vn chuync gi mc ti thiu v s bt kn khng xy ra. H thng thnh cng bao gm:

Hn ch thng kh trong RBCs Lp chm c nh ca , ct, vi hay cht do. Lp ha lng ca ct, cacbon hoat ha, ht nha trao i ion Lp lng ca nhng ht nh Mng ngn ca l phn ng sinh hc, loi mng cung cp H2 v l mng bm dnh

sinh hc.

Thi gian gi nc thp khi b mt vn chuyn thng thong. V d, x l cht lng cthi gian gi nc t hn 10 pht( Jeris, Beer, and Mueller, 1974). Ti trng th tch trongtrng hp ny c th vt qu 20,000 kg BODL/1,000m

3-d.2.3Qu trnh kh Nitrate bn bc 1

Qu trnh kh nitrate bn bc 1 c gi l bn n hay qu trnh kh N kt hp, lin quan nch s BOD trong nc thi thc hin qu trnh kh Nitrate. V vy bn kh nitrate bc 1


28/36

khng th hot ng nh mt qu trnh b sung sau qu trnh x l th cp, bi v x l th cp(x l bc 2) loi b nhng cht hu c ng vai tr l cht cho in t. Hn na s khnitrate din ra phi c s tch hp y cc qu trnh hiu kh, oxi ha BOD v nitrat ha. Qutrnh tch hp phi d tr cht cho in t hu c cho qua trnh phn nitrat thiu kh, trong khiti cng mt thi gian, nu cung cpiu kin hiu kh th cho php din ra qu trnh nitrate

ha, to nitrat cho qu trnh phn Nitrat. 2 qu trnh ny hu nh tri ngc nhau. Trong thc t,chng c th c iu ha.t c 2 mc ch ca qu trnh kh nitrate bn bc 1 cung cp nhiu li ch cho x l ncthi:

- V khng phi thm tc nhn cho in t t bn ngoi vo h thng nn gim c chiph hn so vi qu trnh kh nitrate bc 3

- V mt s loi nc thi c BOD b oxi ha vi nitrate nh cht nhn in t, khng phiO2, nn chi ph sc kh gim so vi h thng khc nitrate ha N dng kh trong ncthi.

- Thnh cng loi b hon ton hoc hu nh hon ton N, do cc ngun nc cbo v khi nguy c ph dng ha.Nhng nm gn y, khoc hc k thut pht trin tip cn mt cch r rang nhng i lp

ca qu trnh bn kh Nitrat bc 1. Mt lot cu hnh k thut, nhng tt c qu trnh bnbc 1 da trn 3 tin trnh c bn, c m t trong phn tip theo. Bng cch no c thkt hp cc tin trnh ny li vi nhau to ra hiu qu cho qu trnh x l s c nutrong phn sau.

2.3.1Cc tin trnh c bn bn bc 1 Nc thi thng thng cha BOD hu c v N dng kh c gi la tng Nit Kjeldahl(TKN). TKN s c oxi ha thnh NO3

-_N m khng oxi ha ht tt c BOD trc qu trnhphn Nitrat. 3 tin trnh c bn d tr cht hu c cho in t trong khi qu trnh nitrate ha

din ra:+ D tr v phn hy sinh khi+ Tin kh Nitrat c in+ Nitrat ha ng thi vi kh Nitrat

2.3.1.1 D trv tng hp sinh khiHnh a:

Qu trnh d tr v phn hy sinh khilu gi cc electron t cht cho in t ban utrong sinh khi. Tng hp sinh khi d tr ng lng electron c ngun gc ban u t BOD

v c gii phng thng qua h hp ni sinh thc hin qu trnh kh Nitrat. Vic tip cn

Sludge recycle

Low BODLow High

BOD0

TNK0

aeration

Sludgewaste

AerobicBODOxidationNitrificationBiomasssysthesis

AnoxicDenitrificationwith biomassas donor


29/36

sinh khi ny gn lin vi cc k s Thy s ni ting (Wuhrmanm, 1964) v c gi l qutrnh phn hy sinh khi Wuhrmanm.Hnh a) cho thy, d tr v phn hy sinh khi, bao gm b hiu kh bn hot tnh, trong TKN b Nitrat ha chuyn v dng NO3

-_N; trong khi BOD b oxi ha 1 phn v mt phnc lu tr qua qu trnh tng hp sinh khi. Hn hp bn-nc thi sau chy vo b thiu

kh, ni m NO3-_N c chuyn thnh N2t do qua qu trnh h hp ni sinh. B x l, bntun hon v bn thi c s dng cho ln lt cc chc nng: ng thnh dng rn,cht rn ti ch v kim sot SRT.Mc d qu trnh lu gi v phn hy sinh khi n gin v hiu qu cho vic gi electron choqu trnh kh Nitrat, khng thng s dng n nh 1 qu trnh ring l. 2 thiu st gii thch tisao vic ng dng qu trnh lu gi v phn hy sinh khi b hn ch :

- Qu trnh h hp ni sinh c ng hc chm. ng hc chm ca h hp ni sinh cngha l nng cao cht rn l lng hn dch v thi gian lu nc di trong b thiukh l cn thit. C 2 dn n chi ph u t cao, trong khi trc y c th to nn vn vn hnh vi b x l v vic tun hon.

- Th 2, phn hy sinh khi lun to ra NH4+_N. V vy b thiu kh tun hon N v mBOD vo nc, mc d nng thp hn ban u.2.3.1.2 Tin kh Nitrate c in

Hnh b:

Tin kh Nitrat c inHnh b, trc tip s dng BOD trong dng nc thi cho qu trnh kh nitrat. lm c iuny, b cha u tin l b thiu kh. BOD trong nc thi l cht cho in t cho qu trnh kh

Nitrat xy ra b cha th nht. b 2, hiu kh hon ton, ni m TKN trong nc thi bnitrat ha thnh NO3

- _N v lng BOD khng c dng trong b thiu kh s c tiu thtrong qu trnh hiu kh. Nitrat c hnh thnh trong b hiu kh c cung cp cho b thiukh bi lng ln dng chy tun hon . H thng ny c gi l tin kh Nitrat, bi v qutrnh kh Nitrat c din ra b u tin, v theo sau l nhng phn ng hiu kh. Trc khixy ra qu trnh kh Nitrat, lm sao lng electron cha trong lng BOD c duy tr choqu trnh ny. Cha kha cho vic s dng BOD trong nc thi l dng tun hon nitrate t bhiu kh. NO3

-khng tun hon trong nc thi v loi b phn on N bi qu trnh kh Nitrat

tng ng vi

vi Q l lu lng dng chy vo b v l lu lng dng tunhon ( mi quan h ny c lm r phn cui ca phn Bn kh Nitrat bc 1). V vy, h s

ti ch (100% .

) ca 400% tr ln c s dng mang lng NO3

- tr li b thiu kh,

v vy tng N c loi b l rt ln.

Sludge recycle

Some BOD

AnoxicBODOxidation bynitraterespiration

AerobicBODOxidationandnitrification

BOD0TNK0

Low BODsome low

High and mixedliquor recycle aeration

Sludgewaste


30/36

Phng php tin kh Nitrat c in i vo s dng rng ri trn ton th gii. li th ca nbao gm vic s dng trc tip lng BOD trong nc thi cho qu trnh kh Nitrat, iu nylm gim chi ph sc kh so vi hiu kh nghim ngt loi b BOD hon ton; Cc qu trnhng hc cng din ra nhanh hn so vi phng php lu gi v phn hy sinh khi. Khuyt im chnh ca phng php ny l tiu tn nhiu kinh ph cho h thng ng dn v

bm.

2.3.1.3 Kt hp 2 qu trnh Nitrate ha v phn Nitrate haHnh c:

Cch tip cn th 3 ca phng php Bn kh Nitrat bc 1 l Nitrat ha ng thi vi khNitrat. c minh ha hnh cKhi nng DO xung thp hn 1 mg/l (ppm) th qu trnh phn Nitrat thiu kh s din rasong song vi cc phn ng hiu kh ca qu trnh Nitrat ha v qu trnh oxi ha BOD.3 yu t cho php tt c cc phn ng din ra ng thi:

1.

Cc loi enzyme nitrogen reductase c ngn chn ch khi DO > 1 mg/l.2. Qu trnh c ch enzyme nitrogen reductase l khng ng k khi DO < 1 mg/l.3. DO trong h thng xung thp hn bnh thng, v vy qu trnh kh Nitrat c th din

ra thm ch cn mnh m hn khi bn trong mng sinh hc, ngay khi cc cht cho int lt (thm nhp) vo bn trong t bo.

C bn 100% qu trnh loi b N bng s kt hp qu trnh Nitrat ha vi kh Nitrat cghi nhn, v mt phn qu trnh kh Nitrat c th din ra trong hu ht cc h thng bn hottnh nitrate ha v c nng DO di mc bo ha. Khi bn hot tnh c khai thc trit ,s kt hp qu trnh Nitrat ha vi kh Nitrat pht huy tt c nhng u im ca qu trnh tinkh Nitra , ng thi loi b c nhng im bt li chnh, hiu qu tun hon tng ln. Vmt nh hng, duy tr mt nng DO thp trong sut qu trnh x l to ra 1 t l tun honv cng cao v cho php loi b 100% N.

Ngy nay, hn ch chnh ca vic lp t h thng kt hp Nitrat ha vi kh Nitrat l chng tacha bit c s lin quan ca SRT (thi gian lu bn), thi gian lu nc v DO c thc sm bo.c im chung ca tt c cc qu trnh kh nitrate bn bc 1 l mt cng ng vi sinh vt thchin tt c cc phn ng. Cng ng ny chnh l Bn bc 1. Vi khun Nitrat oxi ha ammoni

bt c khi no c s hin din cu DO, sinh vt d dng c s chuyn i qua li gia h hpthiu kh vhiu kh hoc chng thc hin ng thi 2 phng thc h hp ny. V nhng sinhvt Nitrat ha l c th t dng, t l tng trng ca chng s kim sot SRT mc cn thit,nhng tt c cc chng vi sinh vt c cng SRT. Nhng SRT ln hn 15 d (days) c s dng

trong hu ht cc h thng v i khi cn di hn na. SRT cn cung cp nhng nhn t an ton

BOD0

TNK0

Low BOD, and

Sludgewaste

Sludge recycle

Controlled Low D.OSimultaneousnitrification,denitrification, andaerobic BOD oxidationx> 15 days


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cho cc vi khun nitrat ha khi nng DO xung thp hoc =0. SRT di c ngha l s tch tca MSLL l ng k.Mt kt qu thc t cho SRT di lthi gian lu nc () cn phi tng ln gi cho hmlng MSLL trong gii hn hp l, iu ny c quyt nh bng hiu sut ca b cha.

Nhng thng s ca b cha cho qu trnh kh nitrate bn bc 1 c dng tng t nh nhng

b hiu kh m rng cho bn hot tnh. Thi gian lu nc trong cc phn ng cho qu trnhtin kh Nitrat v kt hp Nitrat ha vi kh Nitrat thng thng mt t nht 10 gi i vi chtthi in hnh v ln hn 24 gi cho mt s trng hp. Thm ch yu cu thi gian lu nccn di hn khi nc thi b nhim nng.

2.3.2Qu trnh bin i c bn bn bc 1Nhng bt li ca cc tin trnh c bn cho qu trnh kh nitrate bn bc 1thc y pht trin k

hoch kt hp cc tin trnh c bn khc phc cc hn ch. Ba bin th l qu trnh Barnard ,

b phn ng hng lot v h thng mng sinh hc.

2.3.2.1 Qu trnh Barnardinfluent

Hnh 10.2

Qu trnh kt hp ni ting nht mang tn ngi pht minh ra n, Dr. J. Barnard Nam

Phi(Barnard,1975). Qu trnh Barnard, th hin di dng s nh hnh 10.2, bt u vi tin

phn nitrate trong khung 1 v 2. Thi gian lu thy lc in hnh, da trn dng chy lu lng

Q, khong 14h cho giai on tin phn nitrat vi phm vi t 7 n 24h. Vi mt t l tun hon

cho QR2 ca 400%, kh

1.Anoxicpredenitrification

= 3hbased

2. aerobicnitrification 11h

4. aerobicnitrification 1h 3. anoxicdenitrificatio

n

settler

Mixed li uor

Sludge recycle

effluentt

Sludge wasting


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ong chng 80% ca u vo TKN b phn nitrat thnh N2, trong khi khong 20% ri

khi b 2 thnh NO3--N. Nu u vo TKN l 50mg/l, NO3

--N khan ri khi b 2 vo khong

10mg/l.

Nc thi t b 2 chy vo b 3, ni m h hp ni sinh kh nhin liu 10mg/l NO3_

-Nthnh kh N2. Thi gian in hnh lu gi thy lc l 3h. Phn hy t bo gii phng NH4+-N

vo nc vi t l khong 0.3mg NH4+-N/mg NO3

_-N. V vy, dng vo t s phn hy sinh

khi( b 3) bao gm khong 3mg NH4+-N/l.

B 4 quynh khong 1h qut gi vo oxi ha NH4+-N thnh NO3

_-N. V th, u ra

t qu trnh Barnard bao gm NO3_-N vo khong 6% u vo TKN. B lng hot ng nhng

chc nng thng thng ca n v c thit k vi tiu chun kh m rng.

Qu trnh Barnardph bin rng ri trn th gii, s dng qu trnh kh nitrate bn bcmt loi b thnh cng 90% N. Tr ngi ca n l nhiu b, tng ng thi gian lu thy

lc di, v dng tun hon ng k gia b 2 v 1.

2.3.2.2 B Hiu kh gin on (SBR)

Hnh 10.3

Fill React 1 React 2 React 3 SettleAnoxic Aerobic Anoxic Aerobic


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3h 3h 2h 0.33h 0.67hMix Aerated Mixed Aerated Quiescent

B phn ng hng lot (SBR) l phng php thay th t c mc ch ging nh

tin kh nitrate v qu trnh Barnard. Hnh 10.3 m t mt chu trnh 9h in hnh loi b c90% N, nh qu trnh Barnard. Trong sut giai on thiu oxy, BOD nc thi b nitrate ha

vi NO3- mang theo bn lng t chu trnh trc. Giai on hiu kh u tin, oxy ha TKN

thnh NO3-, trong khi BOD d c tn dng cho hiu kh. Giai on b thiu kh phn nitrat

ch yu qua h hp ni sinh. Giai on b hiu kh th hai( b3) bin i NH4+-N, gii phng

trong b thiu kh, thnh NO3_ u ra(sau lng) v mang theo cho b thiu kh ca chu trnh

tip theo. SBR nm bc gn nh cng chc nng trong thi gian 5 giai on ca qu trnh

Barnard trong khng gian. S khc bit ng k duy nht l SBR ch s dng NO 3- mang theot b lng v chuyn n tin phn nitrat, trong khi qu trnh Barnard ch yu s dng hn hp

cht lng tun hon t giai on hiu kh u tin.

Mc d chu trnh SBR thng thng ko di 8 n 12h, SRT v thi gian lu thy lc

ging qu trnh Barnard. SRT l 15h hoc nhiu hn trong khi thi gian lu thy lc l 8 n

24h. Hot ng SBR c th c rt ngn ch cn tin phn nitrat. V th, b thiu kh, mt

b hiu kh, v giai on lng c gi li.

2.3.2.3 H thng mng sinh hc


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Hnh 10.4

ng thi qu trnh nitrat v kh nitrat c th hon thnh vi qu trnh mng sinh hc,

ging nh s pht trin huyn ph. Dn n s kt hp t nhin ca mng sinh hc , oxy ha

BOD hiu kh, nitrat ha v kh nitrat c th tin hnh song song vi cc lp khc nhau ca

mng sinh hc. V th, ng thi qu trnh nitrat ha v kh nitrat bng mng sinh hc c th

thc hin trong mt b vi nhiu cch tng t nh cch xut hin bn hot tnh. Nng DO,

t l tch ri cc mng sinh hc v ti b mt ca BOD l thng s thit k quan trng. Nghin

cu v pht trin trong tng lai l cn thit xac1 nh phm vi ng tin cy cho cc tham s

thit k.

Tin kh nitrate mng sinh hc c th thc hin c. Hnh 10.4 m t b mng sinh hc

thiu kh trc mt b mng sinh hc hiu kh, v dng thi hiu kh c tun hon cung

cp NO3_ cho b mng sinh hc k kh. Tin kh nitrate mng sinh hc, hai cng ng vi khunkhc bit pht trin. V th n khng phi l bn bc mt, mc d n t c tt c mc ch

ca qu tnh bn bc mt.Bi v sinh khi khng di chuyn vi nc, h thng mng sinh hc

th hin hnh 10.4 khng khai thc sinh lu gi v phn hy sinh khi. Nu s kh nitrat l

cn thit , qu trnh bc ba nn a vo trong hnh 10.4. Ln lt, giai on th ba c th c

hot ng lu gi v phn hy sinh khi nu n hot ng trong trnh t vi giai on 2. Nn

tng sinh khi v d tr OD trong sut giai on hiu kh, trong khi n hot ng kh nitrat ni

sinh khi k kh.Mi b mng sinh hc c th thit k nguyn l s dng qu trnh b mng sinh hc. B

hiu kh l mt v d m trong qu trnh nitrat ha v oxy ha BOD hiu kh phi cng tn

ti. B thiu kh thng thng c BOD d ng k, trong khi nng NO3_N c th rt nh. V

th, t l gii hn c cht c th c NO3-, ch khng phi BOD. Nghin cu chuyn su l cn

thit trc khi chng ta bit Tm quan trng ca gii hn NO3- trong b sinh hc thiu kh.

QU TRNH ANAMMOX

Anoxic biofilmreactordenitrification

Aerobicbiofilm reactorNitrificationand aerobicBOD

influent effluent

High effluent recycle to turn


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Gn y, mt vi khun l trong nhm sinh vt bm y c pht hin vi kh nng oxy hak kh NH4

+-N thnh N2(Strous, Kuenen, v Jetten, 1999; Strous et al.,1999). Chng ny cgi l vi khun ANAMMOX, vit tt ca Anaerobic AMMonium Oxidation.Vi khun ANAMMOX dng ammonium nh cht cho in t v nitrate nh cht nhn in t.Phng trnh nng lng nh sau:NH4

+ + NO2- = N2 + 2 H2O

Cc t bo t dng, cacbon v c c chuyn thnh cacbon cu to t bo thng qua qutrnh oxy ha nitrite thnh nitrate. Nitrite cng c xem nh ngun cung cp nito:5 CO2 + 14 NO2

- + 3 H2O + H+ = C5H7O2N + 13 NO3

-Sn phm sinh ra v tc tng trng c trng ca qu trnh ANAMMOX l khng cao, chkhong 0,14g VSSa/gNH4

+-N v tng ng 0,065/d (Strous, Heifnen, Kuenen, Jetten, 1998).iu ny cho chng ta h s cn bng l:

NH4+ + 1,26 NO2- + 0,085 CO2 + 0,02 H+ = N2 + 0,01 C5H7O2N + 0,24 NO3+ + 1,95 H2OS pht hin ra ANAMMOX l mt pht hin mang tnh t ph trong k thut sinh hc mitrng. Tuy nhin, s quan trng ca ANAMMOX trong k thut sinh hc mi trng vn chac bit n. iu kin tch ly ti u ca qu trnh gm thi gian lu c bit (SRT rt di),hot ng bn vng, s c mt ca nitrite, thiu oxy, thiu ngun cp c th l nguynnhn ca s gim nitrite thng qua phn nitrate.

III. Kt LunTrong cc phng php x l nit, th x l nit bng phng php sinh hc cho hiu sut kh

nit cao t 70-95% lng nit trong nc thi. Qu trnh x l n nh, ng tin cy. Cc cngtrnh s dng cng d vn hnh v qun l, din tch t yu cu nh, chi ph u t hp l


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Bn cnh qu trnh kh nit bng phng php thng thng l nitrat ha v phn nitrat th qu

trnh Anammox (Anaerobic Ammonia Oxidation) cho hiu sut x l cao hn vi nhiu u

im ni tri nht l gim c lng bn x l v lng oxi cung cp cho qu trnh x l.

Vi nhng tc hi do nit trong nc thi em n cho sc khe con ngi v cho mi trng,

vic tm ra cc bin php x l cho hiu qu cao, t tn km ng thi m bo s pht trin bn

vng, dng chnh nhng yu t sinh thi trong t nhin x l l v cng cn thit. Chng tacn nghin cu pht trin v hon thin hn na cc qu trnh x l ny, m bo s n inh

ca mi trng sng.

Nhom 1,5-Xu Ly Sinh Hoc Cac Hop Chat Chua N

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