Download pdf - Cơ Sở Lý Thuyết Các Quá Trình Xử Lý Nước Thải

GREEN EYE ENVIRONMENT

CONG TY MOI TRNG TAM NHN XANH GREE

Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com

TS: Nguyen Trung Viet TS: Tran Th My Dieu Copyright 2006 gree-vn.com, All rights reserved. Xin ghi r ngun khi bn pht hnh li thng tin t trang ny.

1-1

CHNG I. C S LY THUYET CAC QUA TRNH X LY NC THAI 1.1 TONG QUAN VE CAC BIEN PHAP X LY NC THAI Nc thai noi chung co cha nhieu chat o nhiem khac nhau, oi hoi phai x ly bang nhng phng phap thch hp khac nhau. Mot cach tong quat, cac phng phap x ly nc thai c chia thanh cac loai sau: - Phng phap x ly ly hoc; - Phng phap x ly hoa hoc va hoa ly; - Phng phap x ly sinh hoc. PHNG PHAP X LY LY HOC Trong phng phap nay, cac lc vat ly, nh trong trng, ly tam, c ap dung e tach cac chat khong hoa tan ra khoi nc thai. Phng phap x ly ly hoc thng n gian, re tien co hieu qua x ly chat l lng cao. Cac cong trnh x ly c hoc c ap dung rong rai trong x ly nc thai la (1) song/li chan rac, (2) thiet b nghien rac, (3) be ieu hoa, (4) khuay tron, (5) lang, (6) lang cao toc, (7) tuyen noi, (8) loc, (9) hoa tan kh, (10) bay hi va tach kh. Viec ng dung cac cong trnh x ly ly hoc c tom tat trong Bang 3.1. Bang 1.1 Ap dung cac cong trnh c hoc trong x ly nc thai (Metcalf & Eddy, 1991)

Cong trnh Ap dung Li chan rac Tach cac chat ran tho va co the lang

Nghien rac Nghien cac chat ran tho en kch thc nho hn ong nhat

Be ieu hoa ieu hoa lu lng va tai trong BOD va SS

Khuay tron Khuay tron hoa chat va chat kh vi nc thai, va gi can trang thai l lng

Tao bong Giup cho viec tap hp cua cac hat can nho thanh cac hat can ln hn e co the tach ra bang lang trong lc

Lang Tach cac can lang va nen bun

Tuyen noi Tach cac hat can l lng nho va cac hat can co ty trong xap x ty trong cua nc, hoac s dung e nen bun sinh hoc

Loc Tach cac hat can l lng con lai sau x ly sinh hoc hoac hoa hoc

Mang loc Tng t nh qua trnh loc. Tach tao t nc thai sau ho on nh

Van chuyen kh Bo sung va tach kh

Bay hi va bay kh Bay hi cac hp chat hu c bay hi t nc thai





1-2

PHNG PHAP X LY HOA HOC Phng phap hoa hoc s dung cac phan ng hoa hoc e x ly nc thai. Cac cong trnh x ly hoa hoc thng ket hp vi cac cong trnh x ly ly hoc. Mac du co hieu qua cao, nhng phng phap x ly hoa hoc thng at tien va ac biet thng tao thanh cac san pham phu oc hai. Viec ng dung cac qua trnh x ly hoa hoc c tom tat trong Bang 3.2. Bang 3.2 Ap dung cac qua trnh hoa hoc trong x ly nc thai (Metcalf & Eddy, 1991)

Qua trnh Ap dung Ket tua Tach phospho va nang cao hieu qua cua viec tach can l lng

be lang bac 1

Hap phu Tach cac chat hu c khong c x ly bang phng phap hoa hoc thong thng hoac bang phng phap sinh hoc. No cung c s dung e tach kim loai nang, kh chlorine cua nc thai trc khi xa vao nguon

Kh trung Pha huy chon loc cac vi sinh vat gay benh

Kh trung bang chlorine Pha huy chon loc cac vi sinh vat gay benh. Chlorine la loai hoa chat c s dung rong rai nhat

Kh chlorine Tach lng clo d con lai sau qua trnh clo hoa

Kh trung bang ClO2 Pha huy chon loc cac vi sinh vat gay benh

Kh trung bang BrCl2 Pha huy chon loc cac vi sinh vat gay benh

Kh trung bang Ozone Pha huy chon loc cac vi sinh vat gay benh

Kh trung bang tia UV Pha huy chon loc cac vi sinh vat gay benh

PHNG PHAP SINH HOC Vi viec phan tch va kiem soat moi trng thch hp, hau het cac loai nc thai eu co the c x ly bang phng phap sinh hoc. Muc ch cua x ly nc thai bang phng phap sinh hoc la keo tu va tach cac loai keo khong lang va on nh (phan huy) cac chat hu c nh s hoat ong cua vi sinh vat hieu kh hoac k kh. San pham cuoi cung cua qua trnh phan huy sinh hoc thng la cac chat kh (CO2, N2, CH4, H2S), cac chat vo c (NH4+, PO43-) va te bao mi. Cac qua trnh sinh hoc chnh s dung trong x ly nc thai gom nam nhom chnh: qua trnh hieu kh, qua trnh thieu kh, qua trnh k kh, thieu kh va k kh ket hp, va qua trnh ho sinh vat. Moi qua trnh rieng biet con co the phan chia thanh chi tiet hn, phu thuoc vao viec x ly c thc hien trong he thong tang trng l lng (suspended-growth system), he thong tang trng dnh bam





(attached-growth system), hoac he thong ket hp. Phng phap sinh hoc co u iem la re tien va co kha nang tan dung cac san pham phu lam phan bon (bun hoat tnh) hoac tai sinh nang lng (kh methane). 1.2 PHNG PHAP X LY LY HOC Trong nc thai thng cha cac chat khong tan dang l lng. e tach cac chat nay ra khoi nc thai thng s dung cac phng phap c hoc nh loc qua song chan rac hoac li chan rac, lang di tac dung cua trong lc hoac lc ly tam, va loc. Tuy theo kch thc, tnh chat ly hoa, nong o chat l lng, lu lng nc thai va mc o can lam sach ma la chon cong nghe x ly thch hp. 1.2.1 SONG CHAN RAC Nc thai dan vao he thong x ly trc het phai qua song chan rac. Tai ay, cac thanh phan co kch thc ln (rac) nh gie, rac, vo o hop, la cay, bao nilon, c gi lai. Nh o tranh lam tac bm, ng ong hoac kenh dan. ay la bc quan trong nham am bao an toan va ieu kien lam viec thuan li cho ca he thong x ly nc thai. Tuy theo kch thc khe h, song chan rac c phan thanh loai tho, trung bnh va mn. Song chan rac tho co khoang cach gia cac thanh t 60 100 mm va song chan rac mn co khoang cach gia cac thanh t 10 en 25 mm. Theo hnh dang co the phan thanh song chan rac va li chan rac. Song chan rac cung co the at co nh hoac di ong. Cac loai song chan rac c trnh bay tom tat nh sau:

1-3

CAC LOAI SONG CHAN RAC

Song Chan Rac Tho Song Chan Rac Mn Li Chan Rac

- Loai co nh - Loai co nh- Loai di ong - Nhom song chan rac - Dang a - Dang trong

- Nhom song chan rac

Song chan rac c lam bang kim loai, at ca vao kenh dan, nghieng mot goc 45-600 neu lam sach thu cong hoac nghieng mot goc 75-850 neu lam sach bang may. Tiet dien cua song chan co the tron, vuong hoac hon hp. Song chan tiet dien tron co tr lc nho nhat nhng nhanh b tac bi cac vat gi lai. Do o thong dung hn ca la thanh co tiet dien hon hp, canh vuong goc pha sau





va canh tron pha trc hng oi dien vi dong chay. Van toc nc chay qua song chan gii han trong khoang t 0,6 1 m/s. Van toc cc ai dao ong trong khoang 0,75 m/s 1 m/s nham tranh ay rac qua khe cua song. Van toc cc tieu la 0,4 m/s nham tranh phan huy cac chat thai ran.

Hnh 1.1 Song chan rac lam sach thu cong. 1.2.2 LANG CAT Be lang cat c thiet ke e tach cac tap chat vo c khong tan co kch thc t 0,2 mm en 2 mm ra khoi nc thai nham bao am an toan cho bm khoi b cat, soi bao mon, tranh tac ng ong dan va tranh anh hng en cac cong trnh sinh hoc pha sau. Be lang cat co the c phan thanh 2 loai: (1) be lang ngang va (2) be lang ng. Ngoai ra, e tang hieu qua lang cat, be lang cat thoi kh cung c s dung rong rai. Van toc dong chay trong be lang ngang khong c vt qua 0,3 m/s. Van toc nay cho phep cac hat cat, hat soi va cac hat vo c khac lang xuong ay, con hau het cac hat hu c khac khong lang va c x ly nhng cong trnh tiep theo. 1.2.3 LANG Be lang co nhiem vu lang cac hat can l lng co san trong nc thai (be lang t 1) hoac can c tao ra t qua trnh keo tu tao bong hay qua trnh x ly sinh hoc (be lang t 2). Theo chieu dong chay, be lang c phan thanh: be lang ngang va be lang ng. Trong be lang ngang, dong nc thai chay theo phng ngang qua be vi van toc khong ln hn 0,01 m/s va thi gian lu nc t 1,5-2,5 gi. Cac be lang ngang thng c s dung khi lu lng nc thai ln hn 15000 m3/ngay. oi vi be lang ng, nc thai chuyen ong theo phng thang ng t di len en vach tran vi van toc 0,5-0,6 m/s va thi gian lu nc trong be dao ong trong khoang 45 phut 120 phut. Hieu suat lang cua be lang ng thng thap hn be lang ngang t 10 en 20%.

1-4





1-5

Hnh 1.2 Cau tao be lang ng.

1.2.4 TUYEN NOI Phng phap tuyen noi thng c s dung e tach cac tap chat ( dang hat ran hoac long) phan tan khong tan, t lang kem khoi pha long. Trong mot so trng hp, qua trnh nay con c dung e tach cac chat hoa tan nh cac chat hoat ong be mat. Trong x ly nc thai, qua trnh tuyen noi thng c s dung e kh cac chat l lng, lam ac bun sinh hoc. u iem c ban cua phng phap nay la co the kh hoan toan cac hat nho, nhe, lang cham trong thi gian ngan. Qua trnh tuyen noi c thc hien bang cach suc cac bot kh nho vao pha long. Cac bot kh nay se ket dnh vi cac hat can. Khi khoi lng rieng cua tap hp bot kh va can nho hn khoi lng rieng cua nc, can se theo bot kh noi len be mat. Hieu suat qua trnh tuyen noi phu thuoc vao so lng, kch thc bot kh, ham lng chat ran. Kch thc toi u cua bot kh nam trong khoang 15 en 30 m (bnh thng t 50-120 m). Khi ham lng hat ran cao, xac suat va cham va ket dnh gia cac hat se tang len, do o lng kh tieu ton se giam. Trong qua trnh tuyen noi, viec on nh kch thc bot kh co y ngha quan trong. e at muc ch nay oi khi ngi ta bo sung them vao nc cac chat tao bot co tac dung lam giam nang lng be mat phan pha nh cresol, natri alkylsilicat, phenol, ieu kien tot nhat e tach cac hat trong qua trnh tuyen noi la khi ty so gia lng phap khi va pha ran at 0,01 0,1. Ty so nay c xac nh nh sau:

Mng thu San cong tac Bo truyen ong Mang rang ca

Vanh chan bot noi Canh gat bot

Ong thu nc sau lang

Ong trung tam phan phoi nc

Ngan thu bot noi Ong thu bun

Canh gat bun

Ong dan nc vao

ay va tng be beton

Kg/ngay khong kh cung cap

Kg/ngay lng chat ran trong nc thai

A

S =





Ty le nay thay oi tuy theo loai chat l lng co trong nc thai va thng c xac nh bang thc nghiem.

1,3 sa(fP 1)

Sa

A

S =

Trong o

sa o hoa tan cua khong kh (mL/L) f Phan kh hoa tan ap suat P, thng f = 0,5 P Ap suat (atm) Sa Nong o chat ran (mg/L) 1,3 Khoi lng rieng cua khong kh (1,3 mg/mL)

Trong trng hp co tuan hoan dong bao hoa kh:

1,3 sa(fP 1)R

SaQ

A

S =

Trong o

R Lu lng dong tuan hoan (m3/ngay) Q Lu lng nc thai (m3/ngay)

Tuy theo phng thc cap khong kh vao nc, qua trnh tuyen noi c thc hien theo cac phng thc sau: - Tuyen noi bang kh phan tan (Dispersed Air Floation). Trong trng hp nay, thoi trc tiep

kh nen vao be tuyen noi e tao thanh bot kh co kch thc t 0,1 1 mm, gay xao tron hon hp kh nc cha can. Can tiep xuc vi bot kh, dnh ket va noi len be mat.

- Tuyen noi chan khong (Vacuum Flotation). Trong trng hp nay, bao hoa khong kh ap

suat kh quyen, sau o, thoat kh ra khoi nc ap suat chan khong. He thong nay thng t s dung trong thc te v kho van hanh va chi ph cao.

- Tuyen noi bang kh hoa tan (Dissolved Air Flotation). Suc khong kh vao nc ap suat cao

(2-4 atm), sau o giam ap giai phong kh. Khong kh thoat ra se tao thanh bot kh co kch thc 20-100 m (Hnh 3.4).

1-6





1-7

Bon khuech tan

Bm tuan hoan

Van ieu ap Mang thu can Thiet b gat can

Thiet b vt bot Motor truyen ong Mang thu bot noi

Hnh 1.3 S o he thong tuyen noi dang ADF.

Nc sau x ly

Kh

nen

Nc thai

1.2.5 LOC Loc c ng dung e tach cac tap chat co kch thc nho khi khong the loai c bang phng phap lang. Qua trnh loc t khi dung trong x ly nc thai, thng ch s dung trong trng hp nc sau khi x ly oi hoi co chat lng cao. e loc nc thai, ngi ta co the s dung nhieu loai be loc khac nhau. Thiet b loc co the c phan loai theo nhieu cach khac nhau: theo ac tnh nh loc gian oan va loc lien tuc; theo dang cua qua trnh nh lam ac va loc trong; theo ap suat trong qua trnh loc nh loc chan khong (ap suat 0,085 MPa), loc ap lc (t 0,3 en 1,5 MPa) hay loc di ap suat thuy tnh cua cot chat long; Trong cac he thong x ly nc thai cong suat ln khong can s dung cac thiet b loc ap suat cao ma dung cac be loc vi vat lieu loc dang hat. Vat lieu loc co the s dung la cat thach anh, than coc, hoac soi nghien, tham ch ca than nau hoac than go. Viec la chon vat lieu loc tuy thuoc vao loai nc thai va ieu kien a phng. Qua trnh loc xay ra theo nhng c che sau: - Sang loc e tach cac hat ran hoan toan bang nguyen ly c hoc; - Lang trong lc; - Gi hat ran theo quan tnh; - Hap phu hoa hoc; - Hap phu vat ly; - Qua trnh dnh bam; - Qua trnh lang tao bong.





Thiet b loc vi lp hat co the c phan loai thanh thiet b loc cham, thiet b loc nhanh, thiet b loc h va thiet b loc kn. Chieu cao lp vat lieu loc trong thiet b loc h dao ong trong khoang 1-2 m va trong thiet b loc kn t 0,5 1 m.

Hnh 1.4 Thiet b sieu loc s dung mang membrane 1.3 PHNG PHAP X LY HOA HOC VA HOA LY 1.3.1 TRUNG HOA Nc thai cha cac acid vo c hoac kiem can c trung hoa a pH ve khoang 6,5 en 8,5 trc khi thai vao nguon nhan hoac s dung cho cong nghe x ly tiep theo. Trung hoa nc thai co the thc hien bang nhieu cach nhau: - Tron lan nc thai acid vi nc thai kiem;

- Bo sung cac tac nhan hoa hoc;

- Loc nc acid qua vat lieu co tac dung trung hoa;

- Hap thu kh acid bang nc kiem hoac hap thu ammoniac bang nc acid.

1-8





1-9

e trung hoa nc thai cha acid co the s dung cac tac nhan hoa hoc nh NaOH, KOH, Na2CO3, nc ammoniac NH4OH, CaCO3, MgCO3, olomt (CaCO3.MgCO3) va xi mang. Song tac nhan re nhat la voi sa 5-10% Ca(OH)2, tiep o la soa va NaOH dang phe thai. Trong trng hp trung hoa nc thai acid bang cach loc qua vat lieu co tac dung trung hoa, vat lieu loc s dung co the la manhetit (MgCO3), olomt, a voi, a phan, a hoa va cac chat thai ran nh x va x tro. Khi loc nc thai cha HCl va HNO3 qua lp a voi, thng chon toc o loc t 0,5 1 m/h. Trong trng hp loc nc thai cha ti 0,5% H2SO4 qua lp olomt, toc o loc lay t 0,6-0,9 m/h. Khi nong o H2SO4 len en 2% th toc o loc lay bang 0,35 m/h.

e trung hoa nc thai kiem co the co the dung kh acid (cha CO2, SO2, NO2, N2O3,). Viec s dung kh acid khong nhng cho phep trung hoa nc thai ma ong thi tang hieu qua lam sach chnh kh thai khoi cac cau t oc hai.

Viec la chon phng phap trung hoa la tuy thuoc vao the tch va nong o cua nc thai, che o thai nc va chi ph hoa chat s dung. 1.3.2 OXY HOA KH e lam sach nc thai, co the s dung cac tac nhan oxy hoa nh clo dang kh va hoa long, dioxyt clo, clorat canxi, hypoclorit canxi va natri, permanganat kali, bicromat kali, peroxy hydro (H2O2), oxy cua khong kh, ozone, pyroluzit (MnO2). Qua trnh oxy hoa se chuyen cac chat oc hai trong nc thai thanh cac chat t oc hai hn va tach khoi nc. Qua trnh nay tieu ton nhieu hoa chat nen thng ch s dung khi khong the x ly bang nhng phng phap khac. 1.3.3 KEO TU - TAO BONG Trong nguon nc, mot phan cac hat thng ton tai dang cac hat keo mn phan tan, kch thc cua hat thng dao ong trong khoang 0,1 en 10 m. Cac hat nay khong noi cung khong lang, va do o tng oi kho tach loai. V kch thc hat nho, ty so dien tch be mat va the tch cua chung rat ln nen hien tng hoa hoc be mat tr nen rat quan trong. Theo nguyen tac, cac hat nho trong nc co khuynh hng keo tu do lc hut VanderWaals gia cac hat. Lc nay co the dan en s dnh ket gia cac hat ngay khi khoang cach gia chung u nho nh va cham. S va cham xay ra do chuyen ong Brown va do tac ong cua s xao tron. Tuy nhien, trong trng hp phan tan keo, cac hat duy tr trang thai phan tan nh lc ay tnh ien v be mat cac hat mang tch ien, co the la ien tch am hoac ien tch dng nh s hap thu co chon loc cac ion trong dung dch hoac s ion hoa cac nhom hoat hoa. Trang thai l lng cua cac hat keo c ben hoa nh lc ay tnh ien. Do o, e pha tnh ben cua hat keo can trung hoa ien tch be mat cua chung, qua trnh nay c goi la qua trnh keo tu. Cac hat keo a b trung hoa ien tch co the lien ket vi nhng hat keo khac tao thanh bong can co kch thc ln hn, nang hn va lang xuong, qua trnh nay c goi la qua trnh tao bong. Qua trnh thuy phan cac chat keo tu va tao thanh bong can xay ra theo cac giai oan sau:





Me3+ + HOH Me(OH)2+ + H+ Me(OH)2+ + HOH Me(OH)+ + H+ Me(OH)+ + HOH Me(OH)3 + H+-------------------------------------------------------- Me3+ + HOH Me(OH)3 + 3H+

Hnh 1.5 He thong keo tu tao bong ket hp vi be lang Lamella

Nhng chat keo tu thng dung nhat la cac muoi sat va muoi nhom nh:

Al2(SO4)3, Al2(SO4)3.18H2O, NaAlO2, Al2(OH)5Cl, Kal(SO4)2.12H2O, NH4Al(SO4)2.12H2O FeCl3, Fe2(SO4)3.2H2O, Fe2(SO4)3.3H2O, Fe2(SO4)3.7H2O

Muoi Nhom

Trong cac loai phen nhom, Al2(SO4)3 c dung rong rai nhat do co tnh hoa tan tot trong nc, chi phi thap va hoat ong co hieu qua trong khoang pH = 5,0 7,5. Qua trnh ien ly va thuy phan Al2(SO4)3 xay ra nh sau: Al3+ + H2O = AlOH2+ + H+

AlOH+ + H2O = Al(OH)2+ + H+

Al(OH)2+ + H2O = Al(OH)3(s) + H+

1-10





1-11

Al(OH)3 + H2O = Al(OH)4- + H+

Ngoai ra, Al2(SO4)3 co the tac dung vi Ca(HCO3)2 trong nc theo phng trnh phan ng sau: Al2(SO4)3 + 3Ca(HCO3)2 Al(OH)3 + 3CaSO4 + 6CO2 Trong phan ln cac trng hp, ngi ta s dung hon hp NaAlO2 va Al2(SO4)3 theo ty le (10:1) (20:1). Phan ng xay ra nh sau: 6NaAlO2 + Al2(SO4)3 + 12H2O 8Al(OH)3 + 2Na2SO4 Viec s dung hon hp muoi tren cho phep m rong khoang pH toi u cua moi trng cung nh tang hieu qua qua trnh keo tu tao bong. Muoi Sat Cac muoi sat c s dung lam chat keo tu co nhieu u iem hn so vi cac muoi nhom do: - Tac dung tot hn nhiet o thap; - Co khoang gia tr pH toi u cua moi trng rong hn; - o ben ln; - Co the kh mui H2S. Tuy nhien, cac muoi sat cung co nhc iem la tao thanh phc hoa tan co mau do phan ng cua ion sat vi cac hp chat hu c. Qua trnh keo tu s dung muoi sat xay ra do cac phan ng sau: FeCl3 + 3H2O Fe(OH)3 + HCl Fe2(SO4)3 + 6H2O Fe(OH)3 + 3H2SO4 Trong ieu kien kiem hoa: 2FeCl3 + 3Ca(OH)2 Fe(OH)3 + 3CaCl2FeSO4 + 3Ca(OH)2 2Fe(OH)3 + 3CaSO4 Chat Tr Keo Tu e tang hieu qua qua trnh keo tu tao bong, ngi ta thng s dung cac chat tr keo tu (flucculant). Viec s dung chat tr keo tu cho phep giam lieu lng chat keo tu, giam thi gian qua trnh keo tu va tang toc o lang cua cac bong keo. Cac chat tr keo tu nguon goc thien nhien thng dung la tinh bot, dextrin (C6H10O5)n, cac ete, cellulose, dioxit silic hoat tnh (xSiO2.yH2O).





Cac chat tr keo tu tong hp thng dung la polyacrylamit (CH2CHCONH2)n. Tuy thuoc vao cac nhom ion khi phan ly ma cac chat tr ong tu co ien tch am hoac dng nh polyacrylic acid (CH2CHCOO)n hoac polydiallyldimetyl-amon. Lieu lng chat keo tu toi u s dung trong thc te c xac nh bang th nghiem Jartest (Hnh 3.5).

Hnh 1.6 Mo hnh Jartest.

1.3.4 HAP PHU Phng phap hap phu c dung rong rai e lam sach triet e nc thai khoi cac chat hu c hoa tan khong x ly c bang cac phng phap khac. Tuy theo ban chat, qua trnh hap phu c phan loai thanh: hap phu ly hoc va hap phu hoa hoc. - Hap phu ly hoc la qua trnh hap phu xay ra nh cac lc lien ket vat ly gia chat b hap phu va

be mat chat hap phu nh lc lien ket VanderWaals. Cac hat b hap phu vat ly chuyen ong t do tren be mat chat hap phu va ay la qua trnh hap phu a lp (hnh thanh nhieu lp phan t tren be mat chat hap phu).

Hnh 1.7 Lc phan tan London (ong vai tro chnh trong qua trnh hap phu)

1-12





1-13

- Hap phu hoa hoc la qua trnh hap phu trong o co xay ra phan ng hoa hoc gia chat b hap phu va chat hap phu. Trong x ly nc thai, qua trnh hap phu thng la s ket hp cua ca hap phu vat ly va hap phu hoa hoc.

Kha nang hap phu cua chat hap phu phu thuoc vao: - Dien tch be mat chat hap phu (m2/g);

- Nong o cua chat b hap phu;

- Van toc tng oi gia hai pha;

- C che hnh thanh lien ket: hoa hoc hoac ly hoc. 1.3.5 TRAO OI ION Phng phap trao oi ion c dung e tach cac kim loai nh Zn, Cu, Cr, Ni, Pb, Hg, Cd, V, Mn, cung nh cac hp chat Arsen, Phospho, cyanua, chat phong xa, khoi nc va nc thai. Phng phap nay cho phep thu hoi nhng chat co gia tr va at mc o lam sach cao. ay con la phng phap c ng dung rong rai e tach muoi trong x ly nc va nc thai. Trao oi ion la mot qua trnh trong o cac ion tren be mat cua chat ran trao oi vi ion cung ien tch trong dung dch khi tiep xuc vi nhau. Trao oi ion la cung mot qua trnh hap thu, trong o, cac ion co trong dung dch thay the nhng ion cua chat trao oi khong hoa tan (con goi mang trao oi ion). Chat trao oi ion dung trong cong nghiep hau het la nhng polyme khong tan, c goi la nha trao oi ion. Mang polyme cha nhng nhom co kha nang ket hp vi cac ion dng (chat trao oi cation - cationit) hoac ket hp vi cac ion am (chat trao oi anion - anionit). Chat trao oi ion co kha nang trao oi vi ca cation va anion c goi la chat trao oi lng tnh. Cac chat trao oi ion co the la cac chat vo c hoac hu c, co nguon goc t nhien hay tong hp nhan tao. Thuoc nhom cac chat trao oi ion vo c t nhien gom cac zeolit, kim loai khoang chat, at set, fenspat, Cac chat co tnh chat trao oi cation la chat cha nhom silicat loai: Na2O.Al2O3.nSiO2.mH2O. Cac chat flour apatit [Ca5(PO4)3]F va hydroxyt apatit [Ca5(PO4)3]OH cung co tnh trao oi ion. Chat trao oi ion vo c tong hp gom silicagen, cac oxyt kho tan va hydroxyt cua mot so kim loai nh nhom, crom, Cac chat trao oi ion hu c co nguon goc t nhien gom acid humic cua at va than a, chung mang tnh acid yeu. e tang tnh acid va dung lng trao oi ngi ta nghien nho than va lu hoa ieu kien d oleum. Than sunfo la cac chat ien ly cao phan t, re va cha ca cac nhom acid manh va acid yeu. Cac chat trao oi ion nay co nhc iem la o ben hoa hoc va o ben c hoc thap, dung lng the tch khong ln, ac biet trong moi trng trung tnh. Cac chat trao oi ion hu c tong hp la cac nha co be mat rieng ln, la cac hp chat cao phan t. Cac goc hydrocarbon cua chung tao nen li khong gian vi cac nhom co chc nang trao oi co nh.





1-14

Kha nang trao oi ion cua cac chat trao oi ion c ac trng bi dung lng trao oi tnh bang so ng lng ion c trao oi tren mot n v khoi lng hay the tch chat trao oi ion. Hay noi cach khac, dung lng trao oi c xac nh tren c s so lng nhom hoat ong tren mot n v khoi lng chat trao oi. Dung lng trao oi phu thuoc vao ac tnh cua nhng nhom hoat ong. oi vi chat trao oi ion axt yeu va baz yeu, dung lng trao oi se phu thuoc nhieu vao s thay oi pH cua dung dch. Nh vay, ben canh dung lng trao oi tong cong, con phai tnh en dung lng trao oi hu ch, la mot phan dung lng trao oi tong cong c s dung di nhng ieu kien th nghiem hoac ap dung thc te. Dung lng trao oi tong cong co the c xac nh trong phong th nghiem bang phng phap chuan o vi axt (oi vi cot trao oi anion dang OH-) hoac vi baz (oi vi cot trao oi cation dang H+). Dung lng trao oi cung c xac nh bang cach ng cong ngng hap thu. 1.4 PHNG PHAP SINH HOC Phng phap sinh hoc c ng dung e x ly cac chat hu c hoa tan co trong nc thai cung nh mot so chat vo c nh H2S, sunfit, ammonia, nit, da tren c s hoat ong cua vi sinh vat e phan huy cac chat hu c gay o nhiem. Vi sinh vat s dung chat hu c va mot so khoang chat lam thc an e sinh trng va phat trien. Mot cach tong quat, phng phap x ly sinh hoc co the phan chia thanh 2 loai: - Phng phap k kh s dung nhom vi sinh vat k kh, hoat ong trong ieu kien khong co

oxy;

- Phng phap hieu kh s dung nhom vi sinh vat hieu kh, hoat ong trong ieu kien cung cap oxy lien tuc.

Qua trnh phan huy cac chat hu c nh vi sinh vat goi la qua trnh oxy hoa sinh hoa. e thc hien qua trnh nay, cac chat hu c hoa tan, ca chat keo va cac chat phan tan nho trong nc thai can di chuyen vao ben trong te bao vi sinh vat theo ba giai oan chnh nh sau: - Chuyen cac chat o nhiem t pha long ti be mat te bao vi sinh vat;

- Khuech tan t be mat te bao qua mang ban tham do s chenh lech nong o ben trong va ben ngoai te bao;

- Chuyen hoa cac chat trong te bao vi sinh vat, san sinh nang lng va tong hp te bao mi. Toc o qua trnh oy hoa sinh hoa phuc thuoc vao nong o chat hu c, ham lng cac tap chat va mc o on nh cua lu lng nc thai vao he thong x ly. moi ieu kien x ly nhat nh, cac yeu to chnh anh hng en toc o phan ng sinh hoa la che o thuy ong, ham lng oxy trong nc thai, nhiet o, pH, dinh dng va nguyen to vi lng.





1-15

1.4.1 PHNG PHAP K KH Qua trnh phan huy k kh cac chat hu c la qua trnh sinh hoa phc tap tao ra hang tram san pham trung gian va phan ng trung gian. Tuy nhien, phng trnh phan ng sinh hoa trong ieu kien k kh co the bieu dien n gian nh sau: Vi sinh vat

Chat hu c -------------------> CH4 + CO2 + H2 + NH3 +H2S + Te bao mi

Mot cach tong quat, qua trnh phan huy k kh xay ra theo 4 giai oan (Hnh 1.8): - Giai oan 1: Thuy phan, cat mach cac hp chat cao phan t; - Giai oan 2: Acid hoa; - Giai oan 3: Acetate hoa; - Giai oan 4: Methane hoa. Cac chat thai hu c cha cac nhieu chat hu c cao phan t nh proteins, chat beo, carbohydrates, celluloses, lignin, trong giai oan thuy phan, se c cat mach tao thanh nhng phan t n gian hn, de phan huy hn. Cac phan ng thuy phan se chuyen hoa protein thanh amino acids, carbohydrate thanh ng n, va chat beo thanh cac acid beo. Trong giai oan acid hoa, cac chat hu c n gian lai c tiep tuc chuyen hoa thanh acetic acid, H2 va CO2. Cac acid beo de bay hi chu yeu la acetic acid, propionic acid va lactic acid. Ben canh o, CO2 va H2, methanol, cac ru n gian khac cung c hnh thanh trong qua trnh cat mach carbohydrat. Vi sinh vat chuyen hoa methane ch co the phan huy mot so loai c chat nhat nh nh CO2 + H2, formate, acetate, methanol, methylamines va CO. Cac phng trnh phan ng xay ra nh sau: 4H2 + CO2 CH4 + 2H2O 4HCOOH CH4 + 3CO2 + 2H2O CH3COOH CH4 + CO2 4CH3OH 3CH4 + CO2 + 2H2O 4(CH3)3N + H2O 9CH4 + 3CO2 + 6H2O + 4NH3 Tuy theo trang thai cua bun, co the chia qua trnh x ly k kh thanh: - Qua trnh x ly k kh vi vi sinh vat sinh trng dang l lng nh qua trnh tiep xuc k kh

(Anaerobic Contact Process), qua trnh x ly bang lp bun k kh vi dong nc i t di len (Upflow Anaerobic Sludge Blanket - UASB);

- Qua trnh x ly k kh vi vi sinh vat sinh trng dang dnh bam nh qua trnh loc k kh

(Anaerobic Filter Process).





1-16

Hnh 1.8 Qua trnh phan huy k kh.

Qua Trnh Tiep Xuc K Kh (Anaerobic Contact Process) Mot so loai nc thai co ham lng chat hu c cao co the x ly rat hieu qua bang qua trnh tiep xuc k kh (Hnh 1.9). Qua trnh phan huy xay ra trong be kn vi bun tuan hoan. Hon hp bun va nc thai trong be c khuay tron hoan toan. Sau khi phan huy, hon hp c a sang be lang hoac be tuyen noi e tach rieng bun va nc. Bun c tuan hoan tr lai be k kh. Lng bun d thai bo thng rat t do toc o sinh trng cua vi sinh vat kha cham.

UASB (Upflow Anaerobic Sludge Blanket) ay la mot trong nhng qua trnh k kh c ng dung rong rai nhat tren the gii do hai ac iem chnh sau:

Phc chat hu c Acid hu c

H2 4%

Acetic acid

CH4 76%

24%

52%

28%

72% 20%

Qua trnh thuy phanQua trnh acetate hoa va kh hydro

Qua trnh methane hoa

Nc thai

Tuan hoan bun

Tuyen noi/Lang

Nc sau x ly

Hnh 1.9 S o thiet b x ly sinh hoc tiep xuc k kh.





1-17

Ca ba qua trnh, phan huy - lang bun - tach kh, c lap at trong cung mot cong trnh;

Tao thanh cac loai bun hat co mat o vi sinh vat rat cao va toc o lang vt xa so vi bun

en canh o, qua trnh x ly sinh hoc k kh s dung UASB con co nhng u iem so vi qua

t tieu ton nang lng van hanh;

bun;

en giam c chi ph bo sing dinh dng;

co the hoi phuc va hoat ong c sau mot

o be UASB c trnh bay trong Hnh 1.10. Nc thai c nap lieu t pha ay be, i qua

be UASB c duy tr trong khoang 0,6-0,9 m/h. pH thch hp cho

o tai Viet Nam cha co loai bun hat nen qua trnh van hanh c thc hien vi tai trong ban

- -

hoat tnh hieu kh dang l lng.

Btrnh bun hoat tnh hieu kh nh: -

t bun d, nen giam ch ph x ly -

Bun sinh ra de tach nc; -

Nhu cau dinh dng thap n-

Co kha nang thu hoi nang lng t kh methane; -

Co kha nang hoat ong theo mua v bun k kh -thi gian ngng khong nap lieu.

Slp bun hat, qua trnh x ly xay ra khi cac chat hu c trong nc thai tiep xuc vi bun hat. Kh sinh ra trong ieu kien k kh (chu yeu la methane va CO2) se tao nen dong tuan hoan cuc bo giup cho qua trnh hnh thanh va duy tr bun sinh hoc dang hat. Kh sinh ra t lp bun se dnh bam vao cac hat bun va cung vi kh t do noi len pha mat be. Tai ay, qua trnh tach pha kh-long-ran xay ra nh bo phan tach pha. Kh theo ong dan qua bon hap thu cha dung dch NaOH 5-10%. Bun sau khi tach khoi bot kh lai lang xuong. Nc thai theo mang tran rang ca dan en cong trnh x ly tiep theo. Van toc nc thai a vaoqua trnh phan huy k kh dao ong trong khoang 6,6-7,6. Do o can cung cap u o kiem (1000 5000 mg/L) e bao am pH cua nc thai luon luon > 6,2 v pH < 6,2, vi sinh vat chuyen hoa methane khong hoat ong c. Can lu y rang chu trnh sinh trng cua vi sinh vat acid hoa ngan hn rat nhieu so vi vi sinh vat acetate hoa (2-3 gi 350C so vi 2-3 ngay, ieu kien toi u). Do o, trong qua trnh van hanh ban au, tai trong chat hu c khong c qua cao v vi sinh vat acid hoa se tao ra acid beo de bay hi vi toc o nhanh hn rat nhieu lan so vi toc o chuyen hoa cac acid nay thanh acetate di tac dung cua vi sinh vat acetate hoa. Dau khoang 3 kg COD/m3.ng. Moi khi at en trang thai on nh, tai trong nay se c tang len gap oi cho en khi at tai trong 15 - 20 kg COD/m3.ng. Thi gian nay keo dai khoang 3 -4 thang. Sau o, be se hoat ong on nh va co kha nang chu qua tai, cung nh nong o chat thai kha cao. Kh metan thu c co the s dung cho viec un nau va cung cap nhiet. Lng bun sinh ra rat nho nen khong can thiet phai at van e x ly bun. Qua trnh x ly nay ch tieu ton mot lng nho nang lng dung e bm nc.





Lan can bao ve

On

1-18

Qua Trnh Loc K Kh (Anaerobic Filter Process) Be loc k kh la mot cot cha vat lieu tiep xuc e x ly chat hu c cha carbon trong nc thai. Nc thai c dan vao cot t di len, tiep xuc vi lp vat lieu tren o co vi sinh vat k kh sinh trng va phat trien. V vi sinh vat c gi tren be mat vat lieu tiep xuc va khong b ra troi theo nc sau x ly nen thi gian lu cua te bao vi sinh vat (thi gian lu bun) rat cao (khoang 100 ngay).

g thu nc sau x ly

San cong tac

Mang thu nc dang rang ca

Thiet b tach pha kh long - ran

Vach hng dong

Cau thang

Vo thiet b

Hon hp

Lp bun k kh

Ong bm nc vao thiet b UASB

Bo phan phan phoi eu lu lng nc thai

Ong th tBnh h th

Bot kh

Dung dch NaOH 5%

Ong dan kh

Hnh 1.10 Upflow Anaerobic Sludge Bed (UASB).





1.4.2 PHNG PHAP X LY SINH HOC HIEU KH Qua trnh x ly sinh hoc hieu kh nc thai gom ba giai oan sau: - Oxy hoa cac chat hu c:

CxHyOz + O2 CO2 + H2O + H Enzyme - Tong hp te bao mi:

CxHyOz + NH3 + O2 Te bao vi khuan + CO2 + H2O + C5H7NO2 - H Enzyme

- Phan huy noi bao:

C5H7NO2 + 5O2 5CO2 + 2H2O + NH3 H Enzyme Cac qua trnh x ly sinh hoc bang phng phap hieu kh co the xay ra ieu kien t nhien hoac nhan tao. Trong cac cong trnh x ly nhan tao, ngi ta tao ieu kien toi u cho qua trnh oxy hoa sinh hoa nen qua trnh x ly co toc o va hieu suat cao hn rat nhieu. Tuy theo trang thai ton tai cua vi sinh vat, qua trnh x ly sinh hoc hieu kh nhan tao co the chia thanh: - X ly sinh hoc hieu kh vi vi sinh vat sinh trng dang l lng chu yeu c s dung e kh

chat hu c cha carbon nh qua trnh bun hoat tnh, ho lam thoang, be phan ng hoat ong gian oan, qua trnh len men phan huy hieu kh. Trong so nhng qua trnh nay, qua trnh bun hoat tnh la qua trnh pho bien nhat.

- X ly sinh hoc hieu kh vi vi sinh vat sinh trng dang dnh bam nh qua trnh bun hoat tnh

dnh bam, be loc nho giot, be loc cao tai, a sinh hoc, be phan ng nitrate hoa vi mang co nh.

Be Bun Hoat Tnh Vi Vi Sinh Vat Sinh Trng L Lng Trong be bun hoat tnh hieu kh vi vi sinh vat sinh trng dang l lng, qua trnh phan huy xay ra khi nc thai tiep xuc vi bun trong ieu kien suc kh lien tuc. Viec suc kh nham am bao cac yeu cau cung cap u lng oxy mot cach lien tuc va duy tr bun hoat tnh trang thai l lng. Nong o oxy hoa tan trong nc ra khoi be lang t 2 khong c nho hn 2 mg/L. Toc o s dung oxy hoa tan trong be bun hoat tnh phu thuoc vao: - Ty so gia lng thc an (chat hu c co trong nc thai) va lng vi sinh vat: ty le F/M; - Nhiet o; - Toc o sinh trng va hoat o sinh ly cua vi sinh vat; - Nong o san pham oc tch tu trong qua trnh trao oi chat; - Lng cac chat cau tao te bao;

1-19





- Ham lng oxy hoa tan.

Hnh 1.11 Hnh minh hoa c che x ly cua ao suc kh e thiet ke va van hanh he thong bun hoat tnh hieu kh mot cach hieu qua can phai hieu ro vai tro quan trong cua quan the vi sinh vat. Cac vi sinh vat nay se phan huy cac chat hu c co trong nc thai va thu nang lng e chuyen hoa thanh te bao mi, ch mot phan chat hu c b oxy hoa hoan toan thanh CO2, H2O, NO3-, SO42-, Mot cach tong quat, vi sinh vat ton tai trong he thong bun hoat tnh bao gom Pseudomonas, Zoogloea, Achromobacter, Flacobacterium, Nocardia, Bdellovibrio, Mycobacterium, va hai loai vi khuan nitrate hoa Nitrosomonas va Nitrobacter. Them vao o, nhieu loai vi khuan dang si nh Sphaerotilus, Beggiatoa, Thiothrix, Lecicothrix, va Geotrichum cung ton tai.

Yeu cau chung khi van hanh he thong bun hoat tnh hieu kh la nc thai a vao he thong can co ham lng SS khong vt qua 150 mg/L, ham lng san pham dau mo khong qua 25 mg/L, pH = 6,5 8,5, nhiet o 60C < t0C < 370C. Mot so s o he thong bun hoat tnh sinh trng l lng c trnh bay trong hnh di ay.

Nc thai Be lang

Be thoi kh

Be lang Nc sau x ly

Bun thai

Tuan hoan bun Bun

a. Qua trnh bun hoat tnh hieu kh co ien vi dong chay nut. (Conventional plug-flow activated process)

1-20





1-21

b. Qua trnh bun hoat tnh hieu kh khuay tron hoan toan. (Complete-mix activated sludge process) Hnh 1.12 S o he thong bun hoat tnh hieu kh.

Be Hoat ong Gian oan (Sequencing Batch Reactor SBR) Be hoat ong gian oan la he thong x ly nc thai vi bun hoat tnh theo kieu lam ay va xa can. Qua trnh xay ra trong be SBR tng t nh trong be bun hoat tnh hoat ong lien tuc ch co ieu tat ca xay ra trong cung mot be va c thc hien lan lt theo cac bc: (1) -Lam ay; (2)-Phan ng; (3)-Lang; (4)-Xa can; (5)-Ngng. S o he thong SBR c trnh bay trong Hnh 1.13.

Hnh 1.13 S o hoat ong cua he thong SBR. Be Bun Hoat Tnh Vi Vi Sinh Vat Sinh Trng Dang Dnh Bam (Attached Growth Activated Sludge Reactor) Nguyen ly hoat ong cua be nay tng t nh trng hp vi sinh vat sinh trng dang l lng, ch khac la vi sinh vat phat trien dnh bam tren vat lieu tiep xuc at trong be. S o cau tao be bun hoat tnh vi vi sinh vat sinh trng dang dnh bam c trnh bay trong Hnh 1.14.

Be lang

Be lang

Tuan hoan Bun thai bo

Nc thai Nc sau x ly

May thoi kh

Lam ay Phan ng Lang NgngXa nc





1-22

Thiet b AASR

Nc thai

Vat lieu dnh bam Gia lp vat lieu dnh bam Ngan thu nc

May thoi kh dang turbine Ong thong kh

Nc sau x ly

Hnh 1.14 Be bun hoat tnh vi vi sinh vat sinh trng dang dnh bam.

(Attacted Growth Activated Sludge Reactor AASR).

Be Loc Sinh Hoc Nho Giot (Trickling Filter) Be loc sinh hoc la mot thiet b phan ng sinh hoc trong o cac vi sinh vat sinh trng co nh tren lp vat lieu loc. Be loc hien ai bao gom mot lp vat lieu de tham nc vi vi sinh vat dnh ket tren o. Nc thai i qua lp vat lieu nay se tham hoac nho giot tren o. Vat lieu loc thng la a dam hoac cac khoi vat lieu deo co hnh thu khac nhau. Neu vat lieu loc la a hoac soi th kch thc hat dao ong trong khoang 25-100 mm, chieu sau lp vat lieu dao ong trong khoang 0,9-2,5 m, trung bnh la 1,8 m. Be loc vi vat lieu la a dam thng co dang tron. Nc thai c phan phoi ten lp vat lieu loc nh bo phan phan phoi. Be loc vi vat lieu loc la chat deo co the co dang tron, vuong, hoac nhieu dang khac vi chieu cao bien oi t 4-12 m. Ba loai vat lieu bang chat deo thng dung la (1) vat lieu vi dong chay thang ng, (2) vat lieu vi dong chay ngang, (3) vat lieu a dang. Chat hu c se b phan huy bi quan the vi sinh vat dnh ket tren lp vat lieu loc. Cac chat hu c co trong nc thai se b hap phu vao mang vi sinh vat day 0,1 0,2 mm va b phan huy bi vi sinh vat hieu kh. Khi vi sinh vat sinh trng va phat trien, be day lp mang tang len, do o, oxy a b tieu thu trc khi khuech tan het chieu day lp mang sinh vat. Nh vay, moi trng k kh c hnh thanh ngay sat be mat vat lieu loc. Khi chieu day lp mang tang len, qua trnh ong hoa chat hu c xay ra trc khi chung tiep xuc vi vi vi sinh vat gan be mat vat lieu loc. Ket qua la vi sinh vat ay b phan huy noi bao, khong con kha nang nh bam len be mat vat lieu loc, va b ra troi.





VAT LIEU LOC

ONG DAN NC VAO 100

BE TONG COT THEP

ONG TAY VN LAN CAN

ONG THU NC RA 300

ONG NG 100

30 0

100

DAY CANG

TANG

Hnh 1.15 Cau tao be loc sinh hoc nho giot

a sinh hoc (Rotating Biological Contactor) a sinh hoc gom hang loat a tron, phang, bang polystyren hoac polyvinylclorua (PVC) lap tren mot truc. Cac a c at ngap trong nc mot phan va quay cham. Trong qua trnh van hanh, vi sinh vat sinh trng, phat trien tren be mat a hnh thanh mot lp mang mong bam tren be mat a. Khi a quay, lp mang sinh hoc se tiep xuc vi chat hu c trong nc thai va vi kh quyen e hap thu oxy. a quay se anh hng en s van chuyen oxy va am bao cho vi sinh vat ton tai trong ieu kien hieu kh.

Hnh 1.16 a sinh hoc (RBC).

1-23





1.4.3 HO SINH VAT

Tuy theo nong o oxy hoa tan co trong ho, he thong ho sinh vat c phan loai thanh: (1) ho hieu kh, (2) ho hieu kh tuy tien, va (3) ho k kh.

Ho hieu kh Ho sinh vat hieu kh n gian nhat la cac ho bang at dung e x ly nc thai bang cac qua trnh t nhien di tac dung cua ca vi sinh vat va tao. Ho hieu kh cha vi sinh vat va tao dang l lng, va ieu kien hieu kh chiem u the suot o sau ho. Co hai loai ho hieu kh c ban: (1) ho nuoi tao nham tao ieu kien e tao phat trien manh nhat, co o sau t 150 450 mm; (2) ho hieu kh nham at c lng oxy hoa tan trong ho ln nhat, co o sau 1,5 m. Trong be quang hp hieu kh, oxy c cung cap bang qua trnh khuech tan kh be mat t nhien va qua trnh quang hp cua tao. Ngoai tr tao, quan the vi sinh vat ton tai trong ho tng t quan the vi sinh vat trong he thong bun hoat tnh hieu kh. Vi sinh vat s dung oxy sinh ra t qua trnh quang hp cua tao e phan huy hieu kh cac chat hu c. Cac chat dinh dng va CO2 thai ra t qua trnh phan huy nay lai la nguon thc an cho tao. Moi quan he cong sinh gia tao va vi sinh vat trong ho hieu kh c trnh bay trong Hnh 1.17.

Tao

Vi sinh vat

O2 CO2, NH3PO43-, H2O

Tao mi

Chat hu c

Nang lng mat tri

Te bao mi

Tao

Hnh 1.17 Moi quan he cong sinh gia tao va vi sinh vat trong ho hieu kh.

Ho hieu kh tuy tien Ho on nh chat lng nc thai trong o ton tai ca ba loai vi sinh vat hieu kh, k kh va hieu kh tuy tien c goi la ho hieu kh tuy tien. Trong ho hieu kh tuy tien ton tai 3 vung: (1) vung be mat ni tao va vi sinh vat ton tai trong moi quan he cong sinh nh trnh bay tren; (2) vung ay k kh, o chat ran tch luy c phan huy

1-24





di tac dung cua vi sinh vat k kh; va (3) vung trung gian, mot phan hieu kh va mot phan k kh, o chat hu c c phan huy i tac dung cua vi sinh vat hieu kh tuy tien. S o ho hieu kh tuy tien c trnh bay trong Hnh 1.18.

1-25

Hnh 1.18 S o ho hieu kh tuy tien. o sau cua ho hieu kh tuy tien gii han trong khoang 1,2 2,4 m (4 - 8 ft) va thi gian lu nc co the keo dai trong khoang 5-30 ngay.

Tao

Vi sinh vat

O2 CO2,

Tao mi

NH3, PO43-

NH3 PO43-

Te bao mi

Tao

Anh sang mat tri

O2 O2 CO2 H2S

H2S + 2O2 --> H2SO4

Te bao chet

Khuech tan

Nc thai

Can lang

Chat hu c CO2 + NH3 + H2S + CH4 Acid hu c,

ru

Bun ay

Gio

Vun

g hi

eu k

h

Vun

g hi

eu k

h tu

y tie

n V

ung

k k

h





1-26

Ho k kh Ho k kh c s dung e x ly nc thai co nong o chat hu c va ham lng can cao. o sau ho k kh phai ln hn 2,4 m (8 ft) va co the at en 9,1 m vi thi gian lu nc dao ong trong khoang 20-50 ngay. Qua trnh on nh nc thai trong ho xay ra di tac dung ket hp cua qua trnh ket tua va qua trnh chuyen hoa chat hu c thanh CO2, CH4, cac kh khac, cac acid hu c va te bao mi. Hieu suat chuyen hoa BOD5 co the at en 70% - 85%.

CHNG I. C S LY THUYET CAC QUA TRNH X LY NC THAI Qua trnhAp dungMuoi Nhom Muoi Sat Chat Tr Keo Tu Qua Trnh Tiep Xuc K Kh (Anaerobic Contact Process) Qua Trnh Loc K Kh (Anaerobic Filter Process) Ho hieu kh

Hnh 1.17 Moi quan he cong sinh gia tao va vi sinh vat trong ho hieu kh. Ho hieu kh tuy tien

Hnh 1.18 S o ho hieu kh tuy tien. Ho k kh