Cơ Sở Lý Thuyết Các Quá Trình Xử Lý Nước Thải

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<ul><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>1-1 </p><p>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 &amp; Eddy, 1991) </p><p>Cong trnh Ap dung Li chan rac Tach cac chat ran tho va co the lang </p><p>Nghien rac Nghien cac chat ran tho en kch thc nho hn ong nhat </p><p>Be ieu hoa ieu hoa lu lng va tai trong BOD va SS </p><p>Khuay tron Khuay tron hoa chat va chat kh vi nc thai, va gi can trang thai l lng </p><p>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 </p><p>Lang Tach cac can lang va nen bun </p><p>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 </p><p>Loc Tach cac hat can l lng con lai sau x ly sinh hoc hoac hoa hoc </p><p>Mang loc Tng t nh qua trnh loc. Tach tao t nc thai sau ho on nh </p><p>Van chuyen kh Bo sung va tach kh </p><p>Bay hi va bay kh Bay hi cac hp chat hu c bay hi t nc thai </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>1-2 </p><p> 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 &amp; Eddy, 1991) </p><p>Qua trnh Ap dung Ket tua Tach phospho va nang cao hieu qua cua viec tach can l lng </p><p>be lang bac 1 </p><p>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 </p><p>Kh trung Pha huy chon loc cac vi sinh vat gay benh </p><p>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 </p><p>Kh chlorine Tach lng clo d con lai sau qua trnh clo hoa </p><p>Kh trung bang ClO2 Pha huy chon loc cac vi sinh vat gay benh </p><p>Kh trung bang BrCl2 Pha huy chon loc cac vi sinh vat gay benh </p><p>Kh trung bang Ozone Pha huy chon loc cac vi sinh vat gay benh </p><p>Kh trung bang tia UV Pha huy chon loc cac vi sinh vat gay benh </p><p> 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 </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>(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: </p><p>1-3 </p><p>CAC LOAI SONG CHAN RAC</p><p>Song Chan Rac Tho Song Chan Rac Mn Li Chan Rac </p><p>- Loai co nh - Loai co nh- Loai di ong - Nhom song chan rac - Dang a - Dang trong </p><p>- Nhom song chan rac </p><p> 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 </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>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. </p><p>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%. </p><p>1-4 </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>1-5 </p><p>Hnh 1.2 Cau tao be lang ng. </p><p> 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: </p><p>Mng thu San cong tac Bo truyen ong Mang rang ca </p><p>Vanh chan bot noi Canh gat bot </p><p>Ong thu nc sau lang </p><p>Ong trung tam phan phoi nc </p><p>Ngan thu bot noi Ong thu bun </p><p>Canh gat bun </p><p>Ong dan nc vao </p><p>ay va tng be beton </p><p>Kg/ngay khong kh cung cap</p><p>Kg/ngay lng chat ran trong nc thai</p><p>A </p><p>S = </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>Ty le nay thay oi tuy theo loai chat l lng co trong nc thai va thng c xac nh bang thc nghiem. </p><p> 1,3 sa(fP 1)</p><p>Sa</p><p>A </p><p>S = </p><p> Trong o </p><p>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) </p><p> Trong trng hp co tuan hoan dong bao hoa kh: </p><p>1,3 sa(fP 1)R</p><p>SaQ </p><p>A </p><p>S = </p><p> Trong o </p><p>R Lu lng dong tuan hoan (m3/ngay) Q Lu lng nc thai (m3/ngay) </p><p> 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 </p><p>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. </p><p> - Tuyen noi chan khong (Vacuum Flotation). Trong trng hp nay, bao hoa khong kh ap </p><p>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. </p><p> - Tuyen noi bang kh hoa tan (Dissolved Air Flotation). Suc khong kh vao nc ap suat cao </p><p>(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). </p><p>1-6 </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>1-7 </p><p>Bon khuech tan </p><p>Bm tuan hoan </p><p>Van ieu ap Mang thu can Thiet b gat can </p><p>Thiet b vt bot Motor truyen ong Mang thu bot noi </p><p>Hnh 1.3 S o he thong tuyen noi dang ADF. </p><p>Nc sau x ly</p><p> Kh </p><p> nen </p><p>Nc thai </p><p> 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. </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p> 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. </p><p>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; </p><p>- Bo sung cac tac nhan hoa hoc; </p><p>- Loc nc acid qua vat lieu co tac dung trung hoa; </p><p>- Hap thu kh acid bang nc kiem hoac hap thu ammoniac bang nc acid. </p><p>1-8 </p></li><li><p> GREEN EYE ENVIRONMENT </p><p>CONG TY MOI TRNG TAM NHN XANH GREE</p><p>Tel: (08)5150181 Fax: (08)8114594 www.gree-vn.com</p><p>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. </p><p>1-9 </p><p>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 cho...</p></li></ul>