các phương pháp xử lý nước

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các phương pháp xử lý nước

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Mc lcA.TNG QUAN21.Tng quan v nc22.Phn loi nc23.Cc thng s, ch tiu nh gi cht lng nc sch.33.1Ch tiu l hc33.2Ch tiu ha hc43.3Ch tiu vi sinh7B.CC PHNG PHP X L NC81.PHNG PHP X L L HC (C HC)81.1Phng php lng81.2Phng php lc101.3Phng php phn ring bng mng (membrane)121.4Phng php nhit151.5Phng php x l bng UV152.PHNG PHP HO HC V HA L172.1Phng php x l ho cht gim cng ca nc172.2Phng php trung ha182.3Phng php oxy ha v kh182.4Tch st bng phng php ho hc192.5Phng php kt lng202.6Phng php hp ph212.7Phng php trao i ion222.8c ch vi sinh vt bng ho cht243.PHNG PHP SINH HC25C.TI LIU THAM KHO28

A. TNG QUAN1. Tng quan v ncNc l mt nhu cu khng th thiu c trong cuc sng hng ngy cng nh trong qu trnh sn xut cng nghip. Trong sinh hot, nc dng cho nhu cu n ung, v sinh, cc hot ng gii tr, phun nc ti cy,Trong hot ng sn xut cng nghip, nc cp cho qu trnh lm lnh, sn xut cc loi thc phm hp, nc gii kht, ru, bia,..Tuy nhin, t s gia tng dn s qu mc, bin i kh hu, lm nhanh chng cn kit ngun ti nguyn nc ngt trn hnh tinh. Nc bt u b nhim, nhim phn, nhim nhiu kim loi nh: Fe, Ca, Mg,.gy nh hng xu n sc kho cng nh cc ngnh cng nghip lin quan n nc.Nc trong t nhin th by gi t nhiu cng b nhim bn, khng tp cht ny th cng l tp cht kia. Bt ngun t nguyn nhn trn, c nhiu bin php thc hin x l nc cung cp nc sch phc v cho n ung, sinh hot con ngi cng nh cc ngnh cng nghip ch bin khc c bit l ngnh cng nghip sn xut nc gii kht.Ni n cng nghip sn xut nc gii kht, th nc l mt thnh phn v cng quan trng v nc l nguyn liu chim t l cao nht (>80%). V vy, nc cn phi x l tht sch trc khi em sn xut thnh nc gii kht, nu khng s gy nh hng rt ln n cht lng, cm quan ca sn phm cng nh n sc kho ngi tiu dng.Nc dng trong cng nghip sn xut nc gii kht ch yu l ngun nc mt v ngun nc ngm.Thnh phn ha hc ca nc mt ph thuc vo tnh cht t ai ni m dng nc chy qua n cc thy vc, cht lng nc mt cn chu nh hng bi cc qu trnh t nhin( ma l, hot ng sng v cht i ca h sinh vt nc,) cng nh hot ng ca con ngi. Trn cng mt con sng, cht lng nc thng xuyn thay i ng k theo thi gian v khng gian.2. Phn loi nc+ Nc mtTrong nc thng xuyn c cc cht kh ha tan, ch yu l xy. xy ha tan trong nc c ngha quan trng i vi i sng ca cc thy sinh vt.Nc mt thng c hm lng cht rn l lng ng k vi cc kch thc khc nhau, mt s trong chng c kh nng lng t nhin, cht l lng c kch thc ht keo thng gy ra c ca nc sng, h. C nhiu cht hu c do sinh vt b phn hy C nhiu rong to, thc vt ni, ng vt ni Cht lng nc thay i theo ma B nh hng mnh m bi hot ng hai bn b ca con ngi( cng nghip, nng nghip)+ Nc ngmNgun nc ngm th thm qu nhiu lp ct, ,..nn cc vi sinh vt d dng li trong nc, nn hm lng khong trong nc rt cao t nc c cng cao.nh hng ca cc cht trong nc i vi cht lng v sc kho con ngi.3.Cc thng s, ch tiu nh gi cht lng nc sch.3.1 Ch tiu l hc Nhit Nhit nc l i lng ph thuc vo iu kin mi trng v kh hu.Nhit c nh hng khng nh n cc qu trnh x l nc. Nc mt c nhit thay i theo nhit mi trng. mu mu thng do cc cht bn trong nc to nn: hp cht st, mangan khng ha tan lm nc c mu ; cc cht mn humic gy ra mu vng; nc b nhim bn bi nc sinh hot hay cng nghip thng c mu xanh hoc en.Mu vng ca hp cht st v mangan.Mu xanh ca to, hp cht hu c.Nc c mu cao thng gy kh chu v mt cm quan. Vi cc quy trnh x l nh sc kh Ozone, clo ha s b, keo t, lng lc c th lm gim mu ca nc. Cn lu khi ngun nc c mu do hp cht hu c, vic s dng clo c th to ra cht mi l Trihalomethane c kh nng gy ung th. Tiu chun nc sinh hot quy nh mu ca nc.n v o mu thng dng l theo mu Platin - Coban.Nc thin nhin c mu thp hn 200 . mu biu kin trong nc thng do cc cht l lng trong nc to ra v d dng loi b bng phng php lc. loi b mu thc ca nc (do cc cht ha tan to nn) phi dng cc bin php ha l kt hp. c c l i lng o hm lng cht l lng trong nc, thng do s hin din ca cht keo, st, to v vi sinh vt.Nc c gy kh chu v mt cm quan, ngoi ra cn c kh nng nhim vi sinh.. Cc quy trnh x l nh keo t, lng, lc gp phn lm gim c ca nc.Nc c c ln chng t nc c nhiu cn bn. n v o c thng l mgSiO2/l, NTU, FTU.Nc c thng c c 20-100 NTU. Nc dng n ung thng c c khng vt qu 5 NTU. Hm lng cht rn l lng cng l mt i lng tng quan n c ca nc. Mi vMi trong nc thng do cc hp cht ha hc ch yu l cc hp cht hu c hay sn phm t qu trnh phn hy vt cht gy nn. Nc thin nhin thng c mi t, mi tanh, mi thi. Nc sau khi kh trng thng nhim mi clo hay clophenol. Ty theo thnh phn v hm lng cc mui khong ha tan nc c th c cc v mn, ngt, cht ,ng. nht nht l i lng biu th s ma st ni, sinh ra trong qu trnh dch chuyn gia cc lp cht lng vi nhau. y l yu t chnh gy nn tn tht p lc v do vy n ng vai tr quan trng trong qu trnh x l nc. nht tng khi hm lng cc mui ho tan trong nc tng v gim khi nhit tng. dn inNc c dn in km. Nc tinh khit 200C c dn in l 4,2 S/m (tng ng in tr 23,8M/cm). dn in ca nc tng theo hm lng cc cht khong ho tan trong nc v dao ng theo nhit . Thng s ny thng c dng nh gi tng hm lng cht khong ho tan trong nc. Tnh phng xTnh phng x ca nc l do s phn hu cc cht phng x trong nc to nn. Nc ngm thng nhim cc cht phng x t nhin, cc cht ny c thi gian bn phn hu rt ngn nn nc thng v hi. Tuy nhin khi b nhim bn phng x t nc v khng kh th tnh phng x ca nc c th vt qu gii hn cho php.Hai thng s tng hot phng x v thng c dng xc nh tnh phng x ca nc. Cc ht bao gm 2 proton v 2 ntron c nng lng xuyn thu nh, nhng c th xuyn vo c th sng qua ng h hp hoc tiu ho, gy tc hi cho c th do tnh ion ho mnh. Cc ht c kh nng xuyn thu mnh hn, nhng d b ngn li bi cc lp nc v cng gy tc hi cho c th.3.2 Ch tiu ha hc pH pH l ch s c trng cho nng ion H+ c trong dung dch thng c dng biu th tnh axit v tnh kim ca nc. pH = 7 nc c tnh trung tnh. pH < 7 nc c tnh axit. pH > 7 nc c tnh kim. pH ca nc c lin quan n s hin din ca mt s kim loi v kh ho tan trong nc. pH < 5, tu thuc vo iu kin a cht, trong mt s ngun nc c th cha st, mangan, nhm dng ho tan v mt s loi kh nh CO2, H2S tn ti dng t do trong nc. pH c ng dng kh cc hp cht sunfua v cacbonat c trong nc bng bin php lm thong. Ngoi ra khi tng pH v c thm tc nhn oxy ho, cc kim loi ho tan trong nc chuyn thnh dng kt ta v d dng tch ra khi nc bng bin php lng lc.Ngun nc c pH > 7 thng cha nhiu Ion nhm carbonate v bicarbonate (do chy qua nhiu tng t ). Ngun nc c pH thpc th gy h men rng.Hin nay, cha c bng chng c th no lin quan gia PH v sc khe ca ngi s dng. Theo tiu chun, pH ca nc s dng cho sinh hot l 6.0 - 8.5 v nc ung pH 6.5 - 8.5. Tuy nhin cc loi nc ngt c gas c pH t 2.0 - 4.0. Cc loi thc phm thng c pH 2.9 - 3.3.Gi tr pH ca nc c lin quan n tnh n mn thit b, ng ng dn nc v dng c cha nc. c bit trong mi trng pH thp, kh nng kh trng ca clo s mnh hn. Tuy nhin khi pH > 8.5, nu trong nc c hp cht hu c th vic kh trng bng Clo d to thnh hp cht Trihalomethane gy ung th. kim kim ton phn l tng hm lng ca cc ion hydrocacbonat (HCO3- ), hyroxyl (OH -) v ion mui ca cc axit yu khc. nhit nht nh, kim ph thuc vo pH v hm lng kh CO2 t do c trong nc kim l mt ch tiu quan trng trong cng ngh x l nc. xc nh kim thng dng phng php chun mu nc th bng axit clohydric ( HCl ) hay axit sunfuric (H2SO4) v theo di theo cht ch th mu, u tin l phenolphatalein sau d l metylloran. cng cng ca nc l i lng biu th hm lng cc ion canxi v magi c trong nc. Trong k thut x l nc s dng ba loi khi nim cng: cng ca nc l i lng biu th hm lng cc ion canxi v magi c trong nc. cng ton phn biu th tng hm lng cc ion canxi v magi c trong nc. cng tm thi biu th tng hm lng cc ion Ca2+, Mg2+ trong cc mui cacbonat v hydrocacbonat canxi, hydrocacbonat magi c trong nc. cng vnh cu biu th tng hm lng cc ion Ca2+, Mg2+ trong cc mui axit mnh ca canxi v magie.C nhiu n v o cng khc nhau: c (o dH): 1 o dH = 10 mg CaO/l nc Php (o dH ): 1 o dH = 10 mg CaCO3/0,7 l nc Anh (oe ): 1 oe = 10 mg CaCO3/0,7 l nc ng u ( mgl/ l): 1 mgl/l = 2,8 o dH.Tu theo gi tr cng, nc c phn loi thnh: cng < 50 mg CaCO3/l : nc mm. cng 50 150 mg CaCO3/l : nc trung bnh. cng 150 300 mg CaCO3/l : nc cng. cng > 300 mg CaCO3/l : nc rt cng.Vit Nam dng dn v o d cng l mili dng lng trong 1 lit (mlg/l) khi o cng < 0.001 mlg/l dng micro dng lng gam trong lit mlg/l. i 1 mglg/l =1.8 o dH. oxy ho c bng permanganat oxy ho l mt i lng nh gi s b mc nhim bn ca ngun nc. l lng oxy cn c oxy ho ht cc hp cht hu c trong nc.Cht oxy ha thng dng xc nh ch tiu ny l pecmanganat kali (KMnO4).Trong thc t, ngun nc c oxy ho ln hn 10 mgO2/l c th b nhim bn. Nu trong qu trnh x l c dng clo dng clo t do hay hp cht hypoclorit s to thnh cc hp cht clo hu c [trihalomentan(THM)] c kh nng gy ung th. T chc Y t th gii quy nh mc ti a ca THM trong nc ung l 0,1mg/l. Ngoi ra, nh gi kh nng nhim ngun nc, cn cn nhc thm cc yu t sau y oxy ho trong nc mt, c bit nc c mu c th cao hn nc ngm. Khi ngun nc c hin tng nhum mu do rong to pht trin, hm lng oxy ho tan trong nc s cao nn oxy ho c th thp hn thc t S thay i oxy ho theo dng chy: Nu thay i chm, lng cht hu c c trong ngun nc ch yu l cc axit humic. Nu oxy ho gim nhanh, chng t ngun nhim l do cc dng nc t bn ngoi vo ngun nc. Cn kt hp vi cc ch tiu khc nh hm lng ion clorua, sunfat, photphat, oxy ho tan, cc hp cht nit, hm lng vi sinh vt gy bnh c th nh gi tng qut v mc nhim bn ca ngun nc. Cc hp cht nitQu trnh phn hu cc cht hu c to ra amoniac (NH4+), nitrit (NO2-) v nitrat (NO3-).Do cc hp cht ny thng c xem l nhng cht ch th dng nhn bit mc nhim bn ca ngun nc. Khi mi b nhim bn, ngoi cc ch tiu c gi tr cao nh oxy ho, amoniac, trong nc cn c mt t nitrit v nitrat. Sau mt thi gian NH4+, NO2- b oxy ho thnh NO3- . Phn tch s tng quan gi tr cc i lng ny c th d on mc nhim ngun nc. Vic s dng rng ri cc loi phn bn cng lm cho hm lng nitrat trong nc t nhin tng cao. Ngoi ra do cu trc a tng tng mt s m ly, nc thng nhim nitrat. Nng NO3- cao l mi trng dinh dng tt cho to, rong pht trin, gy nh hng n cht lng nc dng trong sinh hot. Cc hp cht SilicTrong nc thin nhin thng c cc hp cht silic. pH < 8, silic tn ti dng H2SiO3. Khi pH = 8-11, silic chuyn sang HSiO3-. pH > 11, silic tn ti dng HSiO3 v SiO32- .Do vy trong nc ngm, hm lng silic thng khng vt qu 60mg/l, ch c nhng ngun nc c pH > 9,0 hm lng silic i khi cao n 300mg/l. Trong nc cp cho cc ni hi p lc cao, s tn ti ca cc hp cht silic rt nguy him do cn silic ng li trn thnh ni, thnh ng lm gim kh nng truyn nhit

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