Bi tiu lun: CH S CHT LNG NC WQI V NG DNGMC LC CHNG I: NH NGHA CH S CHT LNG NC WQI .............................5 1.1. NH NGHA .....................................................................................................5 1.2. PHN TCH MT S DNG WQI ...................................................................5 1.3. LA CHN CC CH TIU CHT LNG TNH TON WQI............. 6 1.4. TNH TON CH S WQI .................................................................................6 CHNG 2. TNH HNH NGHIN CU V NG DNG WQI..............................8 2.1. TNH HNH NGHIN CU V P DNG WQI TRN TH GII................8 2.1.1. Ch s cht lng nc ca M......................................................................8 Bng 2.1. Cc thng s c xem xt, thit lp ch s cht lng nc ca NSF. .10 Hnh 2.1: th chuyn i gi tr o ca thng s la chn (xi) thnh ch s ph (qi) trong m hnh NSF - WQI.............................................................................................12 Bng 2.2. Trng s ng gp ca cc thng s theo NSF WQI.................................132.1.2. Ch s cht lng ca Canada......................................................................13 Bng 2.3. Gi tr ch s s dng trong phng php BC..............................................142.1.3. Ch s cht lng nc ca Malaysia ...........................................................16 2.1.4. Ch s cht lng nc p dng ti mt s quc gia Chu u (Universal Water Quality Index)..............................................................................................17 Bng 2.4. Cc thng s la chn v cng thc tnh ch s ph.....................................172.1.5. Ch s cht lng nc ca Bhargava (n )............................................19 Bng 2.5: Cc thng s cht lng nc la chn cho cc mc ch ring..................20 2.2. TNH HNH NGHIN CU V P DNG WQI VIT NAM ...................21 2.2.1. S dng ch s cht lng nc phn loi v phn vng CLN sng Hng....................................................................................................................21 Bng 2.6. Cc thng s cht lng nc la chn cc mc ch s dng ring...........21 Hnh 2.2: Hm nhy ca cc thng s la chn i vi cc mc ch s dng ring22 Bng 2.7. Thng s v trng s tng ng...................................................................232.2.2. Xy dng ch s cht lng nh gi v qun l cht lng nc h thng sng ng Nai .......................................................................................................23 Bng 2.8. Cc thng s cht lng nc v trng s ...................................................23 Bng 2.9. Phn loi cht lng ngun nc mt..........................................................242.2.3. Phn vng cht lng nc theo mc nhim p dng h thng WQI ph hp vi TP H Ch Minh 2007 2008............................................................25 Hinh 2.3: Cac thi ham nhay (Fi) i vi cac thng s CLN khi tinh WQIB ...........28 Bng 2.10. Phn loi cht lng nc theo WQI ........................................................28 CHNG 3. NG DNG NGHIN CU CH S CHT LNG NC NH GI V PHN VNG CHT LNG NC SNG HU........................29 3.1. TNH CP THIT CA TI .....................................................................29 GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNG 3.2 NI DUNG V PHNG PHP NGHIN CU ...........................................29 3.2.2. Phng php nghin cu..............................................................................29 Hnh 3.1. Cc giai on xy dng ch s cht lng nc...........................................30 Bng 3.1. Cc cng thc tp hp tnh WQI [2, 3, 5, 7, 9].............................................303.2.3. Phng php nh gi cht lng nc theo WQI .......................................31 3.3. KT QU -THO LUN .................................................................................31 3.3.1 Kt qu xy dng ch s cht lng nc .....................................................31 Hnh 3.2. th v hm s tng quan gia nng BOD v ch s ph...................31 Hnh 3.3. th v hm s tng quan gia nng DO v ch s ph......................32 Hnh 3.4. th v hm s tng quan gia nng SS v ch s ph.......................32 Hnh 3.5. th v hm s tng quan gia thng s pH v ch s ph......................32 Hnh 3.6. th v hm s tng quan gia nng COD v ch s ph...................33 Hnh 3.7. th v hm s tng quan gia nng Tng Coliform v ch s ph....33 Bng 3.2. Trng s ca cc thng s cht lng nc.................................................343.3.2 nh gi cht lng nc h thng sng Hu bng WQI Phn vng cht lng nc .............................................................................................................34 Bng 3.3. Phn loi nhim ngun nc mt..............................................................343.3.3. Din bin cht lng h thng sng Hu......................................................34 Hnh 3.8. Bn phn vng cht lng nc sng Hu nm 2007..............................36 3.4. KT LUN KIN NGH ...............................................................................37 GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNGDANH MC CC BNGBng 2.1. Cc thng s c xem xt, thit lp ch s cht lng nc ca NSF. . .10Bng 2.2. Trng s ng gp ca cc thng s theo NSF WQI..................................13Bng 2.3. Gi tr ch s s dng trong phng php BC...............................................14Bng 2.4. Cc thng s la chn v cng thc tnh ch s ph......................................17Bng 2.5: Cc thng s cht lng nc la chn cho cc mc ch ring...................20Bng 2.6. Cc thng s cht lng nc la chn cc mc ch s dng ring............21Bng 2.7. Thng s v trng s tng ng....................................................................23Bng 2.8. Cc thng s cht lng nc v trng s ....................................................23Bng 2.9. Phn loi cht lng ngun nc mt...........................................................24Bng 2.10. Phn loi cht lng nc theo WQI .........................................................28Bng 3.1. Cc cng thc tp hp tnh WQI [2, 3, 5, 7, 9].............................................30Bng 3.2. Trng s ca cc thng s cht lng nc..................................................34Bng 3.3. Phn loi nhim ngun nc mt...............................................................34GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNGDANH MC CC HNHHnh 2.1: th chuyn i gi tr o ca thng s la chn (xi) thnh ch s ph (qi) trong m hnh NSF - WQI.............................................................................................12Hnh 2.2: Hm nhy ca cc thng s la chn i vi cc mc ch s dng ring.22Hinh 2.3: Ca c thiham nhay (Fi) i vi ca c thng s CLN khi tinh WQIB ............28Hnh 3.1. Cc giai on xy dng ch s cht lng nc............................................30Hnh 3.2. th v hm s tng quan gia nng BOD v ch s ph....................31Hnh 3.3. th v hm s tng quan gia nng DO v ch s ph.......................32Hnh 3.4. th v hm s tng quan gia nng SS v ch s ph........................32Hnh 3.5. th v hm s tng quan gia thng s pH v ch s ph.......................32Hnh 3.6. th v hm s tng quan gia nng COD v ch s ph....................33Hnh 3.7. th v hm s tng quan gia nng Tng Coliform v ch s ph.....33Hnh 3.8. Bn phn vng cht lng nc sng Hu nm 2007...............................36GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNGCHNG I: NH NGHA CH S CHT LNG NC WQI1.1. NH NGHAWQI l l mt phng tin c kh nng tp hp mt lng ln cc s liu, thng tin v cht lng nc, n gin ha cc s liu cht lng nc, cung cp thng tin di dng d hiu, d s dng cho cc c quan qun l ti nguyn nc, mi trng v cng chng.Ch s cht lng nc thng thng l mt con s nm trong khong t 1 100, nu con s ln hn chng t cht lng nc tt hn mong i.i vi cc ch tiu nh nhit , pH, Coliform phn v oxy ha tan ch s biu th mc yu cu i vi nhu cu s dng. i vi cc cht dinh dng hay bn l cc ch s m thng khng c trong tiu chun th ch s cht lng biu th iu kin mi trng ti khu vc. Ch s tng hp tnh ton trn c s nhiu ch tiu cho ta mt nh gi tng quan. Thng thng ch s trn 80 chng t mi trng nc t cht lng; ch s nm trong khong 40 80 l mc gii hn v nu nh hn 40 l mc ng lo ngi. ng dng ln nht ca ch s cht lng l dng cho cc mc tiu so snh (ni no c cht lng nc xu, ng lo ngi hn so vi cc mc ch s dng) v tr li cu hi ca cng chng mt cch chung chung (cht lng ngun nc ni ti ra sao?). Cc ch s c t tc dng i vi cc mc tiu c th! Vic nh gi cht lng nc cho cc mc tiu c th phi da vo bng phn tch cht lng vi y cc ch tiu cn thit.Ch s cht lng nc WQI khng ch dng xp hng ngun nc m gip cho chng ta thy ni no c vn ng lo ngi v cht lng ngun nc1.2. PHN TCH MT S DNG WQITrn th gii hin nay c nhiu dng WQI ang c s dng, trong ng ch l WQI ca Canada (The Canadian Council of Ministers of the Environment- CCME, 2001). WQI-CCME c xy dng da trn rt nhiu s liu khc nhau s dng mt quy trnh thng k vi ti thiu 4 thng s v 3 h s chnh (F1-phm vi, F2-tn sut vaF3-bin ca cc kt qu khng p ng c cc mc tiu CLN- gii hn chun). WQI-CCME l mt cng thc rt nh lng v vic s dng ht sc thun tin vi cc thng s cng cc gi tr chun (mc tiu CLN) ca chng c th d dng a vo WQI-CCME tnh tan t ng. Tuy nhin, trong WQI-CCME, vai tr ca cc thng s CLN trong WQI c coi nh nhau, mc d trong thc t cc thnh phn CLN c vai tr khc nhau i vi ngun nc v d nh thnh phn cht rn l lng khng c ngha quan trng i vi CLN ngun nc nh thnh phn oxy ha tan. WQI ca Qu V sinh Quc gia M (National Sanitation Foundation-NSF) l mt trong cc b ch s cht lng nc c dng ph bin. WQI-NSF c xy dng bng cch s dng k thut Delphi ca tp on Rand, thu nhn v tng hp kin ca mt s ng cc chuyn gia khp nc M la chn cc thng s CLN quyt nh sau xc lp phn trng lng ng gp ca tng thng s (vai tr quan trng ca thng s - wi) v tin hnh xy dng cc th chuyn i t cc gi tr o c ca thng s sang ch s ph (qi). WQI-NSF c xy dng rt khoa hc da trn kin s GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNGng cc nh khoa hc v cht lng nc, c tnh n vai tr (trng s) ca cc thng s tham gia trong WQI v so snh cc kt qu vi gi tr chun (mc tiu CLN) qua gin tnh ch s ph (qi). Tuy nhin cc gi tr trng s (wi) hoc gin tnh ch s ph (qi) trong WQI-NSF ch thch hp vi iu kin cht lng nc ca M.Do vy, cn c cc WQI ph hp vi iu kin ca Vit Nam, v d vng ng bng sng Cu Long, nn nhit thng thay i rt t hoc c th ni khng c thay i nn yu t nhit ngun nc c th b qua trong WQI, s dng trong thc t. 1.3. LA CHN CC CH TIU CHT LNG TNH TON WQITy theo mc ch s dng c th la chn cc ch tiu gim st cht lng tnh ton ch s WQI, thng thng ngi ta la chn cc ch tiu sau: nhit (T), oxy ha tan (DO), pH, Coliform phn (FC), tng ni t (TN), tng phospho (TP), tng cht rn l lng (SS), BOD, v c.Cng c th dng t s TN:TP thay cho tng ch tiu ring r. Ch tiu TN s dng khi t s TN:TP nh hn 10 v s dng TP khi t s ni trn ln hn 20. Do bn lng lin quan n hai ch tiu l SS v c, do vy kt hp chng li thnh mt s x = 2/[1/SS + 1/ c] s dng cho tnh ton ch s WQI chung.1.4. TNH TON CH S WQI tnh ton v nh gi ch s WQI cn tin hnh 3 bca. Bc 1: Chuyn cc s liu ch tiu cht lng thnh ch s c gi tr t 1 100: mi ch tiu c quy i thnh ch s theo hm s bc 2 vi cc hng s c cho trong bng. Cc hng s ny thay i ty thuc vo loi ngun/v tr o. i vi cc ch tiu nhit , DO, pH, FC, BOD cng thc tnh cho gi tr 80 khi cc ch tiu o t cht lng theo tiuchun. V tr althngquytnhtiuchunchoch tiuColiform, vd ngun loi A nhit thp hn 18 oC cho ch s khong 80.Cng thc tnh WQI cho tng ch tiuWQI = a + b1(ch tiu) + b2(ch tiu)2 b. Bc 2: Kt hp cc ch s: Cc ch s WQI ca nhiu t o trong nm c th kt hp thnh mt ch s cht lng. Ch s WQI cho cc ch tiu khc nhau c kt hp bng cch tnh trung bnh v tr i h s bt li ca cc thng c ch s nh hn 80. H s ny tnh bng cng thcH s bt li = (85 WQI)/2V d ch s WQI trung bnh thng 1 l 89 v ch tiu pH c ch s l 75. Khi h s bt li ca pH = (85 75)/2 = 5 v ch s WQI s l 89 5 = 84.c. Bc 3. p dng cc nguyn tc nh gi S dng cc gi tr trung bnh kt hp cc ch tiu, v d SS v c. Bng cch gim c s ln nh gi;GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNG S dng gii hn cht dinh dng (t l TN:TP, hoc TN hay TP) thay cho vic phi tnh ton ch s cht lng cho c hai ch tiu; H s bt li ln nht (20) s dng cho cht dinh dng v bn lng khi ch s WQI tnh ton cho cc ch tiu ny di 80.Chng ta c th s dng mt s th sau tnh ton WQI, tt nhin l cc ng cong ny ch c tnh minh ha v n s bin i ty thuc vo iu kin c thSau khi tnh ton xong cc ch s i vi tng ch tiu cht lng, chng ta tnh ch s cht lng WQI chung bng cch nhn cc ch s ca tng ch tiu ring l vi h s tng ng ca chngCh tiu H s (fi)DO 0.17FC 0.16pH 0.11BOD 0.11T0.10TP 0.10TN (N-NO3-) 0.10 c 0.08TS 0 .07WQI = WQIi fiTrong : WQIi ch s cht lng tnh cho tng ch tiu ring r.GVHD: TS. MAI TUN ANHBi tiu lun: CH S CHT LNG NC WQI V NG DNGCHNG 2. TNH HNH NGHIN CU V NG DNG WQI2.1. TNH HNH NGHIN CU V P DNG WQI TRN TH GIITrn th gii hin nay ty thuc vo v tr a l, iu kin t nhin, hin trng cht lng nc ca mi vng, mi quc gia m c nhiu cch tip cn v xy dng m hnh ch s cht lng nc khc nhau, trong mt s m hnh ch s cht lng nc (WQI) c p dng ph bin trn th gii c tm tt nh sau.2.1.1. Ch s cht lng nc ca Ma) Ch s cht lng nc bang Oregon (OWQI - Oregon Water Quality Index)Ch s cht lng nc ca bang Oregon c thit lp ban u vo thp k 70. y l phng php n gin v ngn gn nhm din t thng tin v cht lng nc sng, h. La chn cc thng s Cc thng s s dng: nhit , DO, BOD, pH, tng cht rn (TS), tng N, tng P v Fecal Coliform (FC). Cng thc tnh WQI = ni iSIn121=2 2 2 2 2 2 2 21 1 1 1 1 1 1 18FC P N TS pH BOD DO TSI SI SI SI SI SI SI SI+ + + + + + +Trong : + n: s lng cc thng s tnh ton (8 thng s)+ SIi2: l ch s ph ca cc thng s tnh ton+ Cc ch s ph ny c xc nh theo cc cng thc cho tng thng s sau:Nhit + T 110 C: SIT = 100+ 110C < T 290C: SIT = 76,54 + 4,172. T 0,1623.T2 2,0557.10-3T3+ 290C < T : SIT = 10DO+ DO bo ha (DOs ) 100%+ Nng DO (DOc) 3,3 mg/l : SIDO = 10+ 3,3 mg/l 20Ch s ph ca N-NH3: (x: nng , mg/l)+ SIAN = 100,5 105x khi x 0,3+ SIAN = 94 e-0,0573x 5*2 x khi 0,3 < x < 4+ SIAN = 0 khi x 4 Kt qu phn loiMc nhim ngun nc s c kt lun da vo kt qu ch s tnh theo cng thc hoc ch s ph ca cc thng s BOD, N NH3, SS. Kt qu tnh ton v phn loi cht lng nc theo WQI ca Malaysia nh sau:Ch sMc nhim nhim nng nhim va Khng nhimWQI 0 - 59 60 - 80 81 - 100BOD 0 - 79 80 - 90 91 - 100GVHD: TS. MAI TUN ANH 16Bi tiu lun: CH S CHT LNG NC WQI V NG DNGN NH30 - 70 71 - 91 92 - 100SS 0 - 69 70 - 75 76 - 1002.1.4. Ch s cht lng nc p dng ti mt s quc gia Chu u (Universal Water Quality Index) Cng thc chungUWQI = iniiI w1Trong :+ wi l trng s ca thng s i+ Ii l ch s ph ca thng s i+n: s thng s Thng s la chn v ch s ph Cc thng s la chn tnh ton ch s v cng thc tnh ch s ph Ii c nu trong Bng 2.4 Bng 2.4. Cc thng s la chn v cng thc tnh ch s phThng s Phn loi Ch s phBODX