21

Li cm n

i

Mc lc.........ii

Danh sch hnh nh v bng biu....................iii

Danh mc ch vit tt...iv

Dn li nhn xt ca ngi hng dn...vDn li nhn xt ca ngi phn bin....vi

M U ....CHNG I: IU KIN A L T NHIN CA SNG ON QUA A BN TNH SN LA..................................12

1.1. KHI QUT V TNH SN LA...........................................13

1.1.1. V tr a l.....................................................................14

1.1.2. iu kin t nhin...........................15

1.1.3. Ti nguyn..........................................................16

1.2.GII THIU V SNG ...........................................17

CHNG II : TNG QUAN V CHT LNG NC, CC PHNG PHP NH GI CHT LNG NC..2

2.1. CHT LNG NC, CC PHNG PHP NH GI CHT LNG NC.3

2.1.1. Cht lng nc..4

2.1.2. Cc phng php nh gi cht lng nc..5

2.2. TNG QUAN V CHT LNG NC.......6

2.2.1. Gii thiu chung v ch s cht lng nc ..72.2.2. Phng php chung xy dng mt m hnh WQI..82.2.3. u v hn ch ca WQI.92.2.4. Cc m hnh ch s WQI ang c p dng trn th gii...102.2.5. Ch s cht lng nc Vit Nam.11CHNG III: NH GI V PHN VNG CHT LNG NC SNG ON CHY QUAN A BN TNH SN LA...............

3.1. NH GI CHT LNG NC ..................

3.2. PHN VNG CHT LNG NC...............CHNG IV: KT LUN V KIN NGH...

TI LIU THAM KHO.

PH LC.

Ph Lc A:

Ph lc B: ...

M U

1. Tnh cp thit ca tiSng c vai tr quan trng khng ch cung cp mt ngun nc ln cho sinh hot, cng nghip m cn c thy in cho c nc ni chung v Sn La ni ring. V vy, vic nh gi v phn vng cht lng nc trn sng bo v ngun nc ang c nguy c b nhim l ht sc quan trng. Chnh v nhng iu m ti Nghin cu ch s cht lng nc nh gi v phn vng cht lng nc sng trn a bn tnh Sn La l mt s cn thit.2. Mc tiu v phm vi nghin cu2.1. Mc tiu nghin cu

nh gi c tnh hnh cht lng nc sng chy qua a bn tnh Sn La thng qua ch s cht lng nc.Phn vng c cht lng nc sng chy qua a bn tnh Sn La thng qua ch s cht lng nc.2.2. Phm vi nghin cu:

Phm vi nghin cu bao gm ton b Sng on chy qua a bn tnh Sn La.

3. Phng php nghin cu.Phng php thu thp, thng k, x l s liu: Tin hnh thu thp, x l s liu v cht lng nc trn sng on chy qua a bn tnh Sn La.Phng php tng hp, phn tch ti liu: Thu thp h thng ha, x l phn tch nh gi tt c cc ti liu sn c.

CHNG I: IU KIN A L T NHIN CA SNG ON QUA A BN TNH SN LA.

1.1. KHI QUT V TNH SN LA.

Din tch14.055km2

Dn s (2009)1.080.641 ngi

Mt (2009)77 ngi/km2

n v hnh chnhSn La gm c 1 thnh ph: Sn La.

10 huyn: Bc Yn, Mai Sn, Mc Chu, Mng La, Ph Yn, Qunh Nhai, Sng M, Sp Cp, Thun Chu, Yn Chu.

Dn tcVit, Thi, Hmng, Mng, Dao

M in thoi22

M bu chnh27

Bng s xe26

ISO 3166-2VN-05

1.1.1 V tr a lSn La l tnh nm pha ty bc ca T quc, c ta a l t 20031 n 22002 v Bc v t 103011 n 105002 kinh ng. Sn La tip gip vi 6 tnh. Pha bc gip Yn Bi v Lai Chu, pha ng gip Ha Bnh v Ph Th, pha nam gip tnh Thanh Ha v nc Cng Ha Dn Ch nhn dn Lo, pha ty gip huyn in Bin.

1.1.2. iu kin t nhin.

1.1.2.1. a hnh

a hnh Sn La mang tnh cht i ni thp, cao trung bnh khong 600 - 700m. Cc h thng ni ln trong tnh u chy theo hng ty bc - ng nam v cng vi Hong Lin Sn pha bc kp ly mt di cao nguyn vi gia. Chng chia lnh th Sn La thnh hai khu vc sng ln l lu vc sng v lu vc sng M.1.1.2.2. Kh hu.Kh hu Sn La mang tnh cht nhit i r rt, nhit trung bnh nm khong 21C, lng ma trung bnh nm t 1200-1600mm.

Kh hu chia lm hai ma r rt: ma ng lnh, kh, ko di t thng 10 n thng 3 nm sau, m khng kh thp (75-76%); ma h nng m, ko di t thng 4 n thng 9, ma nhiu lng ma chim ti 90% lng ma ca c nm.

1.1.2.3. Thy vn

Sn La c h thng sng sui dy vi 35 con sui ln; 2 sng ln l sng di 280 km vi 32 ph lu v sng M di 90 km vi 17 ph lu; 7.900 ha mt nc h Ho Bnh v 1.400 ha mt nc ao h. Mt sng sui 1,8 Km/km2 nhng phn b khng u, sng sui c dc ln, nhiu thc ghnh do a hnh ni cao, chia ct su.

Cc sng chnh u chy theo hng ty bc - ng nam. i b phn sng sui chy trn cc sn dc, thung lng hp nn lm thc ghnh v thy ch kh tht thng.

1.1.3. Ti nguyn.1.1.3.1. t ai

Din tch t nhin ton tnh l 1.412.500 ha, trong t ang c s dng l 753.520 ha (chim 53,3% t t nhin), so vi c nc t l ny l 97%. Vo nm 2012 khi thy in Sn La vo hon ng th ton tnh s c 3 huyn b ngp vi tng din tch vo khong 13.730 ha.

1.1.3.2. Sinh vt

Rng: H thc vt Sn La c 161 h, 645 chi v khong 1.187 loi, bao gm c thc vt ht kn v ht trn, thc vt nhit i, nhit i v n i. Tiu biu c cc h nh lan, d, tch, sa mu, t vi, du... Cc h c nhiu loi nh cc, ci, u, ba mnh v, long no, hoa mi, ry, ng gia b, du, c ph, lan, cam, na, bng, vang, d....

ng vt rng: thng k c thnh phn cc loi ng vt rng lu vc sng , sng M, ch yu trong cc rng c dng nh Xun Nha, Sp Cp, T Xa, Mng Thi, Nm Gin nh sau: Th c 101 loi, trong 25 h, thuc 8 b; Chim c 347 loi, trong 47 h, thuc 17 b; B st c 64 loi, trong 15 h thuc 2 b; Lng th c 28 loi, trong 5 h, thuc 1 b. Cc loi pht trin nhanh nh di, nhm, don, chim, rn.

1.1.3.4. Khong sn

Sn La c nhiu loi khong sn khc nhau vi gn 150 im, song ch yu l m nh, phn b ri rc trn khp a bn tnh, tr lng khng ln v iu kin khai thc khng thun li.

- Than: C cc loi than m, than gy, than bn, than nu. Tng s trn 10 m v im than nhin liu vi tr lng, tim nng c tnh trn 40 triu tn.

- Ngun vi v st: Vi tr lng kh ln, phn b tng i rng, ang c khai thc, cho php pht trin mnh sn xut xi mng, gch ngi phc v nhu cu trong tnh v xy dng cng trnh thu in Sn La. - Vng: C 4 m sa khong v 3 im vng gc tt c u thuc loi m nh, c trin vng l m vng sa khong Pi Toong huyn Mng La, Mu Lu huyn Mai Sn. - Bt tan: C nhiu im m, ng k l m tan T Ph huyn Mc Chu c tr lng 2,3 vn tn, c gi tr xut khu v tiu dng trong nc.

1.1.3.5. Giao thng

ng b: c tnh c 2.401km, trong c 410km ri nha, 629km ng ri hoc cp phi. Tuyn ng quan trng nht l QL 6 chy qua 5 huyn, th ca tnh l Mc Chu, Yn Chu, Mai Sn, Sn La v Thun Chu.

ng thy: tnh c 210km

ng hng khng: sn bay N Sn mi c nng ln cp 3 vi hai chuyn bay/tun ni lin Sn La vi H Ni.

1.1.3.6. Dn tc

Sn La l a bn c tr ca 12 dn tc : ng nht dn tc Thi: 55,2%, dn tc Kinh 18%, dn tc Hmng 12%, dn tc Mng 8,2%, dn tc Dao 2,76%, dn tc Xinh Mun 1,45%, dn tc Kh m 1,34%, dn tc Lo 0,34%, dn tc La Ha 0,2%, dn tc Khng 0,18%. Mi dn tc u c nhng nt ring trong i sng vn ho truyn thng.

1.2. GII THIU V SNG

Sng , cn gi l sng B hay Giang l ph lu ln nht ca sng Hng. Sng bt ngun t tnh Vn Nam, Trung Quc chy theo hng ty bc - ng nam ri nhp vi sng Hng Ph Th.

Sng c tim nng ln v thu in, chim 25,3% tng tim nng thu in ca ton quc, hin nay c thu in Ho Bnh (Nlm=1.920MW) v ang xy dng thu in Sn La (Nlm=2.400MW). Do s c nhiu bin i tch cc v gim l lt cho h du, ci thin mc nc h lu trong ma cn. Vic xy dng cc p ln gy tc ng mi trng sinh thi, di dn lng h v n nh cuc sng cho nhn dn vng ti nh c lng h Sn La c nghin cu v thc hin mt cch thn trng.CHNG II : TNG QUAN V CHT LNG NC, CC PHNG PHP NH GI CHT LNG NC.

2.1. CHT LNG NC, CC PHNG PHP NH GI CHT LNG NC.2.1.1 Cht lng nc.

Hin nay, c nhiu khi nim lin quan n cht lng nc nh: Cht lng nc l mt ch tiu quan trng lin quan ti cc kha cnh ca h sinh thi v i sng con ngi nh: sc khe cng ng, sn xut lng thc, a dng sinh hc,...Hay cht lng nc l do nhiu yu t cu thnh, bao gm cc thng s vt l, ha hc v sinh hc. Tm quan trng ca mi thng s i vi cht lng nc thay i ty vo mc ch s dng.

Ngy nay, chnh do nhng hot ng cu con ngi l nguyn nhn ch yu lm suy gim cht lng ngun nc. Song song vi s pht trin kinh t, vn ha, dn s ngy cng gia tng th nhu cu s dng nc cng ngy cng tng c v khi lng ln cht lng. Cng vi l nhng nguy c gy ra do s thiu hiu bit ca con ngi v nhng tc ng tim n ca t nhin hay nhng cht c hi do con ngi thi vo mi trng trong tnh trng h thng c s d liu v mng li quan trc cht lng nc cn rt thiu thn. Vic khai thc qu mc cc ngun nc phc v cho nhu cu hng ngy ca con ngi m khng c k hoch bo v s dn n nguy c cn kit v nhim ngun ti nguyn nc ang t ra nhng thch thc to ln cho ton cu v mi quc gia trn th gii. T y, i hi phi c nhng chnh sch mang tm chin lc qun l cht lng nc, bo v ngun nc v kim sot s nhim ngun nc. qun l cht lng nc hiu qu th vic cn thit hin nay l phi nh gi c cht lng nc.Ty theo tng loi nc s dng vi mc ch khc nhau, s c mt s tiu chun tng ng vi mc ch s dng. nh gi cht lng nc cn phi phn tch cc thng s cht lng nc. Ngi ta chia thng s cht lng nc thnh cc nhm: vt l, ha hc v vi sinh.

Cc thng s vt l bao gm: c ( TUR ), nhit (C), mu sc, mi v, tng hm lng cc cht rn ( TS ), Tng hm lng cc cht ha tan (DS),- Nhit nh hng n pH, n cc qu trnh ha hc v sinh ha xy ra trong nc. Nhit ph thuc rt nhiu vo mi trng xung quanh, vo thi gian trong ngy, vo ma trong nmNhit cn c xc nh ti ch (ti ni ly mu).

- Mu sc: Nc nguyn cht khng c mu. Mu sc gy nn bi cc tp cht trong nc (thng l do cht hu c, mt s ion v c (st)), mt s loi thy sinh vtMu sc mang tnh cht cm quan v gy nn n tng tm l cho ngi s dng.- c: gy nn bi cc ht rn l lng trong nc. Cc cht l lng trong nc c th c ngun gc v c, hu c hoc cc vi sinh vt, thy sinh vt c kch thc thng thng t 0,1 10 m. c lm gim kh nng truyn sng ca nc, nh hng ti qu trnh quang hp.1 n v c l s cn quang gy ra bi 1 mg SiO2 ha trong 1 lt nc ct. c c o bng my o c (c k turbidimeter).- Tng hm lng cc cht rn (TS): Cc cht rn trong nc c th l nhng cht tan hoc khng tan. Cc cht ny bao gm c nhng cht v c ln cc cht hu c. Tng hm lng cc cht rn l lng kh tnh bng mg ca phn cn li sau khi lm bay hi 1 lt mu nc trn ni cch thy ri sy kh 105C cho ti khi khi lng khng i (n v tnh bng mg/L).

- Tng hm lng cc cht ha tan (DS): Cc cht rn ha tan l nhng cht tan c trong nc, bao gm c cht v c ln cht hu c. Hm lng cc cht ha tan ( DS) l lng kh ca phn dung dch qua lc khi lc 1 lt nc mu qua phu lc c giy lc si thy tinh ri sy kh 105oC cho ti khi khi lng khng i. n v tnh l mg/L. DS = TS SS.Cc thng s ha hc c th chia thnh cc cht hu c v v c.

- Tng cc cht hu c c c trng bi thng s nhu cu oxy ha (BOD) hoc tng cacbon hu c (TOC). Trong nhiu trng hp ngi ta cn phn tch ring tng cht hoc tng nhm cht hu c c mt trong nc nh: cc ha cht bo v thc vt, phenol,- Cc cht v c c c trng bi cc thng s: mui (Sal), cng, pH, nitrat (NO3 ), nitrit ( NO2 ), amoni (NH3/NH4+), photphat (PO3 ), sunfat ( SO4 2 ).

Cc thng s vi sinh: tng Coliform, Ecoli, Coliform phn,... c coi l nhng thng s ch th cho s nhim cc vi khun c ngun gc phn. l nhm vi khun gy cc loi bnh ng rut, t thng hn, - Coliform phn: Nhm vi sinh vt Coliform c dng rng ri lm ch th ca vic nhim phn, c trng bi kh nng ln men lactose trong mi trng cy 35 - 37C vi s to thnh axit aldehyd v kh trong vng 48h.

- Ecoli: L Esherichia Coli hay trc khun i trng, thng sng trong rut ngi v mt s ng vt, Ecoli c hiu cho ngun gc phn, lun hin din trong phn ca ngi v ng vt, chim vi s lng ln. S c mt ca Ecoli vt qu gii hn cho php chng t s nhim ch tiu ny.Ty thuc vo ngun nc v mc ch s dng nc , ngi ta thng quy nh cc thng s khc nhau, chng hn nh: theo QCVN 08: 2008/BTNMT, s thng s CLN ca ngun nc mt dng cp cho sinh hot gm 32 thng s, nhng thng s ca ngun nc mt cp cho nui tm s ( theo tiu chun ca B Thy sn quy nh nm 2001: 28 TCVN 171: 2001) ch gm c 6 thng s.2.1.2 Cc phng php nh gi cht lng nc.2.1.2.1 nh gi da vo phng php m hnh ha.M hnh ha cht lng nc, ni cch khc l s dng cc m hnh ton hc m phng cht lng nc. y l phng php cn i hi nhiu thng s u vo bao gm cc thng s thy vn, ha l,.. nn kh phc tp. y l mt phng php hiu qu nhng cn s hiu chnh, hiu bit v thy ng lc hc v chi ph cho vic xy dng m hnh cng rt cao.2.1.2.2 Phng php s dng ch s

Ch s l mt tp hp cc tham s hay ch th c tch hp hoc nhn vi trng s. Khi xy dng phng php ch s ny u da trn nhng nguyn tc kh n gin, c th thay i theo iu kin.2.1.2.3 Phng php da vo tng thng s ring l.

Phng php ny l mt phng php truyn thng, vic nh gi cht lng nc thng da vo kt qu phn tch cc thng s ring bit ri so snh chng vi cc gi tr tng ng ng c quy nh trong tiu chun lin quan.Phng php ny thng gy kh khn cho cng tc gim st v qun l cht lng nc, cht lng nc c th t tiu chun da vo mt s thng s nhng cng c mt vi thng s khc khng p ng c. ng thi phng php ny cng khng nh gi c cht lng nc mt cch tng qut, khng phn loi c cht lng nc nn kh s snh c cht lng nc tng vng ca mt con sng, hay cht lng nc sng ny vi sng khc

2.1.2.4 Phng php p dng ch s sinh hc.

Phng php quan trc mi trng nc bng cc thng s ha l ch c th phn nh tnh trng thy vc ti thi im ly mu, m nh hng ca cht lng nc thng b tc ng bi cc ngun trong mt thi gian nht nh v cha cc qu trnh tch ly sinh hc trong c th sinh vt. Cho nn cc thng s ha l kh c th nh gi c y v cht lng nc nh hng n h sinh thi.Trong khi , vic quan trc din bin cht lng nc bng phng php ch s sinh hc c nhiu u im hn phng php ha hc v nhiu mt nh: tn t thi gian hn, chi ph thp hn v kt qu nh gi cng nhanh hn, tng th hn v mt din bin cht lng nc theo thi gian. Kt qu quan trc sinh hc cho php nh gi kh khch quan v tc ng cht lng mi trng nc n h thy sinh lu vc. Tuy nhin th phng php ny gp kh nhiu kh khn trong vic ly cc mu sinh hc nn cng rt t c p dng.2.2 TNG QUAN V CHT LNG NC.

2.2.1 Gii thiu chung v ch s cht lng nc .

Ch s cht lng nc (Water Quality Index - WQI) l mt ch s t hp c tnh ton t cc thng s cht lng nc xc nh thng qua mt cng thc ton hc. WQI dng m t nh lng v cht lng nc v c biu din qua mt thang im.Vic s dng sinh vt trong nc lm ch th cho mc sch c t nmNm 1850 c coi l nghin cu u tin v WQI.

Ch s Horton (1965) l ch s WQI u tin c xy dng trn thang s.

Hin nay c rt nhiu quc gia/a phng xy dng v p dng ch s WQI. Thng qua mt m hnh tnh ton, t cc thng s khc nhau ta thu c mt ch s duy nht. Sau cht lng nc c th c so snh vi nhau thng qua ch s . y l phng php n gin so vi vic phn tch mt lot cc thng s.2.2.2 Phng php chung xy dng mt m hnh WQI.Vic xy dng mt m hnh WQI chia lm 4 bc c bn:

Bc 1: La chn thng s:

C rt nhiu thng s c th th hin cht lng nc, s la chn cc thng s khc nhau tnh ton WQI ph thuc vo mc ch s dng ngun nc v mc tiu ca WQI. Da vo mc ch s dng WQI c th c phn loi nh sau: Ch s cht lng nc thng thng, ch s cht lng nc cho mc ch s dng c bit.Vic la chn thng s c th dng phng php delphi hoc phn tch nhn t quan trng. Cc thng s khng nn qu nhiu v nu cc thng s qu nhiu th s thay i ca mt thng s s c tc ng rt nh n ch s WQI cui cng. Cc thng s nn c la chn theo 5 ch th sau:

Hm lng Oxy: DO

Ph dng: N-NH4, N-NO3, Tng N, P-PO4, Tng P, BOD5, COD, TOC

Cc kha cnh sc khe: Tng Coliform, Fecal Coliform, D lng thuc bo v thc vt, cc kim loi nng.c tnh vt l: Nhit , pH, Mu sc

Cht rn l lng: c, TSS.Bc 2: Chuyn i cc thng s v cng mt thang o (tnh ton ch s). Cc thng s thng c n v khc nhau v c cc khong gi tr khc nhau, v vy tp hp c cc thng s vo ch s WQI ta phi chuyn cc thng s v cng mt thang o. Bc ny s to ra mt ch s ph cho mi thng s. Ch s ph c th c to ra bng t s gia gi tr thng s v gi tr trong quy chun. Bc 3 : Trng s.Trng s c a ra khi ta cho rng cc thng s c tm quan trng khc nhau i vi cht lng nc. Trng s c th xc nh bng phng php delphi, phng php nh gi tm quan trng da vo mc ch s dng, tm quan trng ca cc thng s i vi i sng thy sinh, tnh ton trng s da trn cc tiu chun hin hnh, da trn c im ca ngun thi vo lu vc, bng cc phng php thng k.Mt s nghin cu cho rng trng s l khng cn thit. Mi lu vc khc nhau c cc c im khc nhau v c cc trng s khc nhau, v vy WQI ca cc lu vc khc nhau khng th so snh vi nhau.Bc 4 : Tnh ton ch s WQI cui cng.

Cc cng thc tnh ton WQI c nhiu dng khc nhau, c th tnh v khng tnh n phn trng lng ng gp (wi), c th l dng tng hoc dng tch hay dng Solway Bng 1 cp mt s phng php thng c p dng.Bng 1-1 Cc cng thc tnh WQI tng qutDng tngDng tchDng Solway

Khng tnh phn trng lng ng gp

C tnh phn trng lng ng gp

2.2. 3 u v hn ch ca WQI.T nhng ti liu tham kho v phng php nghin cu cht lng nc bng ch s WQI, t a ra nh gi v cc u im ca WQI trong nh gi cht lng nc:

- Cho php gim 1 lng ln s liu t mt lot cc thng s vt l, ho hc, vi sinh xung cn 1 con s n gin theo 1 phng thc n gin v c tnh lp li.

- L kt qu ca vic tnh ton ton hc nn cho php nh gi, phn loi khch quan CLN v cho php so snh CLN theo khng gian, thi gian.- Thch hp vi vic tin hc ho nn thun li cho qun l v cung cp thng tin cho cng ng.

- Cho php lng ha cht lng nc theo mt thang im lin tc v n th hin tng ha nh hng ca cc thang s cht lng nc.

- To iu kin thun li cho bn ha cht lng nc thng qua vic mu ha cc thang im WQI.

- Khng nhng ng vai tr l ch th ca s thay i cht lng nc m cn ch th cho nhng thay i v tim nng s dng nc.Tuy nhin, cng c nhng mt hn ch nh sau:

- Thiu s nht tr v cch tip cn chung thit k ch s WQI - WQI khng bao hm thng tin v hiu qu kinh t c c t s ci thin CLN.2.2.4 Cc m hnh ch s WQI ang c p dng trn th gii.Trn th gii c nhiu quc gia p dng WQI vo trong thc tin, cng nh c nhiu nh khoa hc nghin cu v cc m hnh WQI. Nhng c 3 m hnh ni ting nht:2.2.4.1 Ch s cht lng nc tng qut ca NSF ( NSF- WQI)Ch s CLN ca Qu v sinh Quc gia M NSF (National Sanitation Foundation Water Quality Index) l mt trong nhng ch s CLN ni ting v c s dng ph bin nht, c xy dng nm 1970 nh l mt cng c truyn thng thng tin v cht lng nc n cng ng v cc nh ban hnh lut. NSF WQI l kiu ch s CLN tng qut, chung cho cc mc ch s dng.

NSF WQI c xy dng bng cch s dng k thut Delphi ca tp on Rand. Mc ch ca phng php ny l thu nhn v tng hp kin ca mt s ng cc chuyn gia khp nc M (142 ngi) v kha cnh qun l cht lng nc nhm trnh nhng vn do quan im ch quan v s khc nhau gia cc a phng.

T kt qu cc phiu cu hi iu tra nhm chuyn gia 9 thng s quan trng nht c xc nh t 35 thng s a ra l DO, Coliorm phn, pH, BOD5 , NO3-, PO43- , nhit , c v tng cht rn ( TS) vi cc trng s tng ng. Cc trng s t tiu im l sc khe cng ng da trn mc ch s dng nc ca con ngi. Tm li, cc cng vic phi lm trong tnh ton NSF_WQI bao gm:

La chn ra cc thng s CLN quyt nh (Xi).

Xc lp phn trng lng ng gp ca tng thng s (wi)

Tin hnh xy dng cc th chuyn i t cc gi tr xi (gi tr o c ca thng s Xi) sang ch s ph (Ii).

Tnh ton WQI bng cc cng thc tp hpCc cng thc tnh WQI c nhiu dng khc nhau, c th tnh v khng tnh n phn trng lng ng gp, c th l dng tng hoc dng tch hoc dng Solway

NSF xy dng hai cng thc WQI dng tng v dng tch l hai cng thc c s dng rng ri M cng nh nhiu quc gia trn th gii.

Dng tng v c tnh n phn trng lng ng gp:

WA WQI = 9i=1 wiqi (0.1) Dng tch v c tnh n trng lng ng gp:

WM - WQI = (0.2)Phn trng lng ng gp (wi) ca 9 thng s la chn nh sau: DO: 0,17; Coliform phn: 0,15; PH: 0,12; BOD5: 0,10; PO43- : 0,10; nhit : 0,10; c: 0,08; TS: 0,08; NO3- : 0,10.Bng 1-2: Phn loi cht lng nc theo NSF WQI

LoiNSF - WQIGii thch

I91 100Ecellent( Cht lng tuyt ho)

II71 90Good ( Tt)

III51 70Medium( Trung bnh)

IV26 50Bad ( Khng tt)

V0 - 25Very Bad ( Rt t )

2.2.4.2 Ch s cht lng nc ca BhargavaCh s cht lng nc ny do Bhargava xy dng vo nm 1983, c p dng u tin phn vng v phn loi cht lng nc sng Ganna, n . Di y l cc bc xy dng ch s cht lng nc ca Bhargava:

- Xc nh cc mc ch s dng nc: C 5 mc ch s dng chnh, l: Tip xc trc tip (tm, bi li)

Cp nc sinh hot (im thu nc th cho cc nh my n c

Nng nghip (hay nc thy li)

Cng nghip (nc cp cho cc ngnh cng nghi p ni chung: lm mt, v sinh cng nghip.

Thy sn (nui tm, c...).

- Xc nh cc thng s cht lng nc cho mi mc ch s dng nc: Cc mc ch s dng nc khc nhau nn yu cu cc thng s cht lng nc cng khc nhau v tm quan trng ca mi thng s cng khc nhau.

Cc tiu ch xc nh cc thng s CLN la chn cho mi mc ch s dng nc bao gm:

+ Thng s phi c tm quan trng ln,

+ Thng s c th xc nh nhanh v chnh xc,

+ S thng s cng t cng tt, nhng phi m t c im v CLN ca sng, knh rch c kho st.

- Xy dng hm nhy cho cc thng s la chn (Fi): Hm nhy m t cht lng cc thng s CLN la chn, l i lng trung tm ca m hnh Bhargava WQI. y l hm tuyn tnh, biu din mi quan h gia Fi vi gi tr xi c dng chuyn cc gi tr o (xi) v cng thang im chung trong khong 0,01 1, vic xy dng da trn cc gi tr gii hn quy nh i vi cc thng s CLN la chn trong cc tiu chun tng ng vi cc mc ch s dng khc nhau.- Tnh ton ch s CLN: WQI cho mi mc ch s dng nc c tnh theo cng thc sau:

WQi = Trong

- Fi: l gi tr hm nhy ca thng s th i

- n: s thng s la chn.

Da theo thang im Bhargava WQI, CLN c phn thnh 5 loi hay

( 5 mc) nh sau:

Bng 1-3: Phn loi cht lng nc theo Bhargava WQILoiBhargava-WQI Gii thch

I90 100Rt tt (khng nhim - nhim rt nh)

II65 89Tt ( nhim nh)

III35 64Trung bnh ( nhim trung bnh)

IV11 34Xu ( nhim nng)

V0 10Rt xu ( nhim rt nng)

2.2.4.3 Ch s cht lng nc ca Canada ( CCME WQI)Ch s cht lng nc Canada CCME WQI c xy dng da trn c s k tha v pht trin m hnh WQI ca bang British Columbia v nm 2001 c Hi ng B trng Mi trng Canada chp nhn a vo s dng. CCME WQI l loi m hnh WQI cho mc ch ring hoc mc ch tng qut v c th p dng cho c ngun nc ngt, nc l v nc mn. Song ch p dng c khi c t nht 4 thng s CLN v 4 t o hay quan trc v nhng tiu chun cht lng nc cho cc mc ch s dng khc nhau ph thuc vo cc tiu chun v quy nh ca quc gi hoc quc t.

CCME WQI c tnh ton t cc h s i din cho 3 yu t: phm vi (F1), tn sut (F2), ln (F3). Trong F1, F2 c xc nh trc tip cn F3 c xc nh gin tip.

- Tnh ton gi tr phm vi F1: F1 t s cc thng s khng p ng c so vi mc hng dn trong khong thi gian tnh ch s.

F1 = ( s thng s vt qu tiu chun/ tng s thng s)*100

- Tnh ton gi tr tn sut F2: F2 l phn trm s mu khng p ng c mc hng dn.

F2 = (S mu khng p ng tiu chun/ Tng s mu)*100

- Tnh ton gi tr bin F3: Gi tr F3 c tnh ton qua 4 bc sau:

Bc 1: Vi cc gi tr khng p ng c tiu chun (cao hn gii hn trn hoc thp hn gii hn di) ta tnh gi tr sau:

+ Khi gi tr ca thng s cao hn tiu chun:

Exi = (Gi tr thng s/Mc hng dn) 1.

+ Khi gi tr ca thng s nh hn tiu chun:

Exi = (Mc hng dn/gi tr thng s) 1Bc 2: Tnh ton gi tr nse:Bc 3: F3 c tnh ton bng phng php tim cn v c gi tr t 0 n 100Bc 4: Tnh ton gi tr WQI

WQI = 100 Bng 1-4: Phn loi cht lng nc theo CCME WQILoiCCME- WQI Gii thch

I95 100Rt tt (khng nhim - nhim rt nh)

II80 94Tt ( nhim nh)

III65 79Trung bnh ( nhi m

trung bnh)

IV45 64Xu ( nhim nng)

V0 44Rt xu ( nhim rt

nng)

2.2.5 Ch s cht lng nc Vit Nam.

Ti Vit Nam trong thi gian qua, Tng cc Mi Trng ban hnh quyt nh s 879/QD- TCMT v vic ban hnh s tay hng dn tnh ton ch s cht lng nc. WQI c cc nh khoa hc nghin cu v p dng cho mt s lu vc sng, mt s nghin cu in hnh nh:- Nghin cu ca TS Tn Tht Lng (2006): Xy dng ch s CLN p dng cho sng ng Nai.Trong nghin cu ny , tc gi s dng phng php Delphi v phn tch tng quan a ra ch s WQI. Bng 1-4: Cc thng s c la chn theo phng php Delphi- Tn Tht Lng

Thng sTrng s tm thiTrng s cui cng

BOD51.000.23

DO0.760.18

SS0.700.16

pH0.660.15

Tng N0.630.15

Tng coliform0.560.13

T im s trung bnh do cc chuyn gia cho ng vi tng khong nng thc t, i vi mi thng s cht lng nc tc gi xy d ng mt th v hm s tng quan gi a nng v ch s ph. Da vo phng php th vi s tr gip ca phn mm x l bng tnh Excel, cc hm ch t lng nc c biu th bng cc phng tr nh sau:- Hm cht lng nc vi thng s BOD5: y =-0,0006x2- 0,1491x + 9,8255

- Hm cht lng nc vi thng s DO: y = 0,0047x2 + 1,20276x -0,0058

- Hm cht lng nc vi thng s SS: y = 0,0003x2 - 0,1304x + 11,459

- Hm cht lng nc vi thng s pH: y = 0,0862x4 - 2,4623x3 + 24,756x2 102,23x + 150,23- Hm cht lng nc vi thng s tng N: y = - 0,04x2 0,1752x + 9,0244

- Hm cht lng nc vi thng s coliform: y = 179.39x -0,4067Ch s WQI cui cng c tnh theo cng th c trung bnh cng c trng s: Trong :

I: Ch s cui cng

qi: Ch s ph cho cc thng s

wi: Trng s nh gi cht lng nc h thng sng ng Nai, da vo mt s kt qu nghin cu ca nhiu tc gi v kinh nghim thc t xut phn loi ngun nc mt theo ch s WQI nh sau:1-5: Phn loi cht lng ngun nc mt Tn Tht Lng

Loi ngunncK hiu muCh s WQInh gi cht lng

1Xanh dng9