tCvn T i u c h u n V i t N a m

TCVN 6001 : 1995 ( ISO 5815-1989 )

Cht lng nc. Xc nh nhu cu oxi sinh ho sau 5 ngy (Bod5). phng php

cy v pha long Water quality - Determination of biochemical oxigen demand

after 5 days (BOD5) - Dilution and seeding method

H Ni - 1995

TCVN 6001 : 1995

2

Li ni u

TCVN 6001 - 1995 hon ton tng ng vi ISO 5815 -

1989.

TCVN 6001 - 1995 do Ban K thut Cht lng nc

TCVN/TC 147 bin son, Tng cc Tiu chun - o lng

- Cht lng trnh duyt, B Khoa hc - Cng ngh v

Mi trng ban hnh.

TCVN 6001 : 1995

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T I u c h u n v I t n a m tcvn 6001 : 1995

Cht lng nc. Xc nh nhu cu oxi sinh ho sau 5

ngy (Bod5). phng php cy v pha long Water quality - Determination of biochemical oxigen demand after 5 days (BOD5) - Dilution

and seeding method

1 Mc ch

Tiu chun nu mt phng php kinh nghim v thng dng xc nh nhu cu oxi sinh ha ca

nc bng nui cy v pha long.

Phng php p dng cho cc loi nc c nhu cu oxi sinh ha ln hn hoc bng 3mg oxi/lt v

khng vt qu 6000 mg oxi/lt. Phng php cng c th p dng cho nhu cu oxi sinh ha ln hn

6000 mg oxi/lt nhng sai s do phi pha long i hi phi thn trng khi x l kt qu.

Kt qu thu c l sn phm kt hp ca cc qu trnh ha hc v sinh ha. Chng khng c c

tnh r rng ca qu trnh ha hc n thun. Tuy nhin, chng cho mt ch th v cht lng nc.

Php th c th b nh hng bi nhiu cht c i vi sinh vt nh cc cht dit khun, cc kim

loi c, clo t do chng c ch s oxi ha sinh ha. S c mt ca to hoc vi sinh vt nitrat ha c

th lm cao kt qu. Ph lc A cung cp thng tin v thi gian v nhit khc nhau.

2 Tiu chun trch dn

Nhng tiu chun sau y c p dng cng vi tiu chun ny. Tt c mi tiu chun u lun

c sot xt li, nhng khuyn khch p dng nhng bn mi nht.

TCVN 6001 : 1995

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TCVN 5499-1995 (ISO 5813:1983), Cht lng nc - Phng php Winkler xc nh oxi ha tan.

ISO 5814:1984, Cht lng nc - Xc nh oxi ha tan - Phng php in ha.

ISO 6107-2: 1981, Cht lng nc - T vng - Phn 1.

ISO 7393-1: 1985, Cht lng nc - Xc nh clo t do v clo tng s - Phn 1: Phng php

chun dng N, N-dietyl-1, 4 phenylendiamin.

ISO. 7393-2: 1985, Cht lng nc - Xc nh clo t do v clo tng s - Phn 2: Phng php o

mu dng N, N - dietyl-1,4 - phenylendiamin cho cng vic kim tra thng ngy.

3 nh ngha

Tiu chun ny dng nh ngha sau:

Nhu cu oxi sinh ha (BOD): nng khi lng ca oxi ha tan b tiu th bi s oxi ha sinh hc

cc cht hu c v / hoc v c trong nc trong nhng iu kin xc nh. (nh ngha ly t ISO

6107-2).

Trong tiu chun ny, "s oxi ha sinh hc" mang ngha "s oxi ha sinh ha".

4 Nguyn tc

Trung ha mu nc cn phn tch v pha long bng nhng lng khc nhau ca mt loi nc

pha long giu oxi ha tan v cha cc vi sinh vt hiu kh, c hoc khng cha cht c ch s nitrat

ha.

nhit xc nh trong mt thi gian xc nh, 5 ngy, ch ti, trong bnh hon ton y v nt

kn. Xc nh nng oxi ha tan trc v sau khi . Tnh khi lng oxi tiu tn trong 1 lt nc.

Tin hnh ng thi th nghim kim tra vi dung dch chun ca gluc v axit glutamic.

5 Thuc th

Trong phn tch ch dng cc thuc th tinh khit phn tch v nc ct hoc nc c tinh khit

tng ng (nc ct t my hon ton bng thy tinh hoc nc qua trao i ion).

Nc khng c cha nhiu hn 0,01mg ng trong 1 lt, khng cha clo t do, cc cloramin, kim,

axit v cc cht hu c.

5.1 Nc cy

TCVN 6001 : 1995

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Nu bn thn mu nc khng cc vi sinh vt cn thit, phi dng nc cy to c bng mt

trong cc cch sau:

a) Nc thi sinh hot, ly t cng chnh hoc t cng ca mt vng dn c khng b nhim cng

nghip. Nc ny c lng trc khi dng.

b) Thm 100g t vn vo 1 lt nc. Lc u v yn 10 pht. Ly 10ml nc trong trn v pha

long thnh 1 lt bng nc ct.

c) Nc sng, h c cha nc thi sinh hot.

d) Dng nc sau khi lng ca cc trm x l nc thi.

e) Nc ly t h lu ca dng thi ca nc cn phn tch hoc nc cha vi sinh vt thch hp cho

nc cn phn tch v c nui cy trong phng th nghim (trng hp nc thi cng nghip

cha cc cht kh b phn hy).

5.2 Cc dung dch mui

Cc dung dch sau y bn t nht trong mt thng v cn bo qun trong cc bnh thy tinh mu

sm. Chng cn c loi b ngay khi c du hiu kt ta hoc sinh vt pht trin.

5.2.1 Dung dch m photphat

Ha tan 8,5g kali dihidrophotphat (KH2PO4), 21,75g kali hidrophotphat (K2HPO4), 33,4g natri

hidrophotphat heptahidrat (Na2HPO4.7H2O) v 1,7g amoni clorua (NH4Cl) trong khong 500ml nc.

Pha long n 1000ml v lc u.

Ch thch: pH ca dung dch m ny phi l 7,2, khng cn iu chnh g thm.

5.2.2 Magie sunfat heptahidrat, 22,5g/l

Ha tan 22,5g magie sunfat heptahidrat (MgSO4.7H2O) trong nc. Pha thnh 1000ml v lc u.

5.2.3 Canxi clorua, 27,5g/l

Ha tan 27.5g canxi clorua khan (CaCl2) (hoc mt lng tng ng mui canxi clorua ngm

nc) trong nc. Pha long thnh 1000ml v lc u.

5.2.4 St (III) clorua hexahidrat, 0,25g/l

Ha tan 0,25g st (III) clorua hexahidrat (FeCl3.6H2O) trong nc. Pha thnh 1000ml v lc u.

5.3 Nc pha long

TCVN 6001 : 1995

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Thm 1ml mi dung dch mui (5.2.1, 5.2.2, 5.2.3 v 5.2.4) vo khong 500ml nc. Pha long

thnh 1000ml v lc u. To nhit 200C cho dung dch va iu ch c, ri sc khng kh

trong 1 gi, ch khng lm nhim bn dung dch, c bit l bi cc cht hu c, cht oxi ha,

cht kh hoc kim loi 1 ), sao cho nng oxi ha tan t nht phi t 8mg/l.

Dung dch chun b nh trn ch c dng trong vng 24 gi, phn d sau 24 gi phi b.

5.4 Nc pha long cy vi sinh vt

Thm t 5ml n 20ml nc cy (5.1) (ty theo ngun gc) vo 1 lt nc pha long (5.3) . Gi nc

va iu ch 200C. Chun b nc ny ngay trc khi dng , b phn d vo cui ngy lm

vic.

Lng oxi b tiu th sau 5 ngy 200C ca nc pha long cy vi sinh vt (5.4) chnh l gi tr trng

(8.3) v khng c vt qu 0,5 mg/l.

5.5 Dung dch axit clohidric (HCl), khong 0,5 mol/l.

5.6 Dung dch natri hidroxit (NaOH), khong 20g/l.

5.7 Dung dch natri sunfit (Na2SO3), khong 0,5 mol/l.

5.8 Dung dch chun gluc/axit glutamic.

Sy mt t gluco khan (C6H12O6) v mt t axit glutamic (HOOC-CH2-CH2-CHNH2-COOH ) 103oC

trong 1 gi. Cn mi th 150 1mg, ha tan trong nc v pha thnh 1000 ml, lc u.

Chun b dung dch ny ngay trc khi dng v b lng d vo cui ngy lm vic .

5.9 Dung dch alylthioure (ATU) (C4H8N2S)

Ho tan 1,00g alylthioure trong nc, pha long thnh 1000ml v lc u. Dung dch bn t nht 2

tun l.

____________________________

1) Nn dng bnh khng kh nn hoc bm nn khng kh , trong khng kh khng c tip xc vi cht

bi trn (bm nn dng mng). Lc v ra khng kh trc khi dng.

TCVN 6001 : 1995

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Bng 1 - pha long khuyn ngh xc nh BOD5

BOD5 d on mg/l H s pha long Kt qu c lm trn

n

p dng cho

3 - 6 gia 1 v 2 0,5 R

4 - 12 2 0,5 R, E

10 - 30 5 0,5 R, E

20 - 60 10 1 E

40 -120 20 2 S

100 - 300 50 5 S, C

200 - 600 100 10 S, C

400 - 1200 200 20 I, C

1000 - 3000 500 50 I

2000 - 6000 1000 100 I

R: nc sng;

E: nc thi c lm sch sinh hc;

S: nc thi c lm trong hoc nc thi cng nghip b nhim nh;

C: nc thi cha x l;

I: nc thi cng nghip b nhim nng.

6 Thit b, dng c

Mi dng c thy tinh cn phi sch, khng cha cc cht c hoc cht phn hy sinh hc, lun

c bo v khi b bn.

Cc thit b thng thng trong phng th nghim v cc thit b dng c sau:

TCVN 6001 : 1995

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6.1 Bnh , ming hp, dung tch t 130ml n 350ml, c nt mi thy tinh, v nu c th nn dng

loi vai vung. Loi 250ml thng c a dng.

6.2 Bung , c kh nng duy tr c nhit 200C 10C.

6.3 Thit b xc nh nng oxi ha tan 2 ).

6.4 Phng tin lm lnh (00 C n 40C) dng vn chuyn v gi mu.

6.5 Bnh pha long, nt thy tinh, vch chia n ml, dung tch ph thuc vo mu pha long yu cu.

7 Gi mu

Mu c gi nhit gia 00C v 40C trong bnh np y tht kn cho n khi em phn tch.

Tin hnh phn tch mu cng sm cng tt v khng gi mu qu 24 gi k t khi ly.

8 Cch tin hnh

8.1 X l s b

8.1.1 Trung ha mu

Nu pH ca mu khng nm trong khong 6 v 8, cn dng dung dch axit clohidric (5.5) hoc natri

hidroxit (5.6) trung ho mu sau khi xc nh th tch bng php th ring. Khi trung ho khng

cn quan tm n kt ta nu c to thnh.

8.1.2 Clo t do v/ hoc clo lin kt

Trung ho clo t do v clo lin kt c trong mu bng dung dch natri sunfit (5.7). Ch khng dng

d.

Cc tiu chun v clo t do v clo lin kt theo ISO 7393-1 v ISO 7393-2.

8.2 Chun b dung dch th

8.2.1 Xc nh BOD khng c ch s nitrat ha

a nhit mu n khong 200C, np khong na bnh v lc trnh qu bo ha oxi.

_____________________________ 2) C th xc nh oxy ho tan bng phng php it theo TCVN 5499-1995 (ISO 5813) hoc phng php in ho (xem ISO 5814)

TCVN 6001 : 1995

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Ly mt th tch xc nh cho vo bnh pha long (6.5) v thm nc pha long cy vi sinh vt

(5.4) n vch. Lc nh trnh to bt kh.

Nu dng h s pha long ln hn 100, cn thc hin vic pha long thnh hai hoc nhiu bc.

8.2.2 Xc nh BOD c c ch s nitrat ha

a nhit mu n khong 200C, np khong na bnh v lc trnh qu bo ha oxi.

Ly mt th tch xc nh cho vo bnh pha long (6.5), thm 2ml dung dch alylthioure (5.9) cho 1 lt

mu pha long ri thm nc pha long cy vi sinh vt (5.4) n vch mc. Lc nh trnh to

bt kh.

Ch thch:

1) C th dng cht c ch 2 - clo - 6 - triclometylpyridin (TCMP) (Cl - C5H3N - CCl3) gn trn natri

clorua. Thm sao cho nng TCMP trong mu pha long t 0,5mg/l.

2) pha long cn ly sao cho sau khi nng oxi ha tan d nm trong khong 1/3 v 2/3

nng ban u.

chn c pha long thch hp cn th nhiu ln theo m hnh ton hc v s dng pha long

tng ng vi BOD5 tham kho (xem bng 1).

Xc nh nhu cu oxi tng s (TOC) v nhu cu oxi ha hc (COD) bng phng php cromat c th

cung cp thng tin tt trong vn ny.

3) Ch ly mu i din.

4) Cch c ch s nitrat ha nh mc 8.2.2 khng phi l c hiu qu trong mi trng hp.

Thm nhiu ATU hn nh ch mc 8.2.2 c th nh hng n chun Winkler.

8.3 Th trng

Tin hnh th trng ng thi vi vic xc nh, dng nc pha long cy vi sinh vt (5.4).

8.4 Tin hnh xc nh

Dng xi-phng np cc mu pha long (xem 8.2) vo cc bnh (6.1), cho trn nh.

cc bt kh bm trn thnh bnh thot ra ht. y bnh, ch trnh gi li bt kh.

TCVN 6001 : 1995

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Chia cc bnh np thnh hai dy, mi dy gm cc mu ca mi mt pha long v mt mu

trng (xem 8.3).

t mt dy cc bnh vo bung (6.2) v trong ti 5 ngy.

o nng oxi ha tan thi im khng trong mi bnh, k c mu trng, ca dy cn li theo

TCVN 5499-1995 (ISO 5813 hoc ISO 5814).

Sau khi , xc nh nng oxi ha tan trong mi bnh, v trong mu trng ca dy t trong

bung , theo TCVN 5499-1995 (ISO 5813 hoc ISO 5814).

8.5 Php th kim tra

kim tra nc pha long cy vi sinh vt, nc cy v k thut ca ngi phn tch, tin hnh

php th kim tra bng cch pha long 20ml dung dch chun gluc - axit glutamic (5.8) vi nc

pha long cy vi sinh vt (5.4) thnh 1000ml v tin hnh nh mc 8.4.

Kt qu BOD5 s nm trong khong 180mg/l v 230 mg/l.

Nu khng, cn kim tra li nc cy v nu cn c k thut ca ngi phn tch.

Tin hnh kim tra ng thi vi mu phn tch.

9 Th hin kt qu

9.1 Xc nh xem mu no trong s cc mu th t iu kin:

32)(

31

211 CCCC

trong :

-C1 l nng oxi ha tan, ca mt trong cc mu th thi im khng, mg/l;

-C2 l nng oxi ha tan, cng ca mu sau 5 ngy, mg/l.

9.2 Nhu cu oxi ha sau 5 ngy (BOD5), tnh bng miligam oxi trong mt lt, c tnh theo phng

trnh:

( ) ( )e

e

VVCC

VVVCCBOD 1431

1215

=

TCVN 6001 : 1995

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trong :

-C1 v C2 ging nh 9.1;

-C3 l nng oxi ha tan, ca mu trng thi im khng mg/l;

-C4 l nng oxi ha tan, ca mu trng sau 5 ngy mg/l;

-Ve l th tch, ca mu dng d chun b dung dch th tng ng, ml;

-V1 l tng s th tch, ca dung dch th , ml.

Nu nhiu mu t kt qu nm trong khong yu cu, tnh gi tr trung bnh ca cc kt qu thu

c ca cc mu .

10 Bo co kt qu

Bo co kt qu gm cc thng tin sau:

a) trch dn tiu chun ny;

b) ngy, gi ly mu;

c) phng php gi mu;

d) ngy, gi bt u phn tch;

e) loi nc cy dng;

f) v c ch s nitrat ha nu dng;

g) s ngy (5);

h) kt qu v phng php trnh by kt qu dng;

j) nhng im c bit ghi nhn c trong qu trnh th;

k) chi tit v nhng cng on khng c trong tiu chun ny, hoc xem nh ty chn.

TCVN 6001 : 1995

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Ph lc A

(thng tin)

Nhng nhit v thi gian khc

Tc oxi ha cc hp cht hu c trong giai on u th BOD c th biu din bng nh lut

Phelp:

ktxL

LLog =10 trong :

-L l gi tr BOD, thi gian bng v cng, mg/l;

-x l BOD, thi im t, tnh bng ngy, mg/l;

-t l thi gian, tnh bng ngy;

-k l hng s tc , biu din bng nghch o ca ngy.

i vi mt loi hp cht hu c v mm vi sinh cho trc, hiu ng ca nhit ln hng s tc

k v gi tr L c th d on c mc gn ng bc nht. iu rt c ch khi xem xt php

th BOD nhng vng kh hu m hoc khi nghin cu nhng con sng di chy qua nhiu vng

kh hu. Tuy nhin, khi dng mi quan h ny phi rt thn trng.

Gi tr BOD tiu chun l sau 5 ngy 200C. Qua nhiu nm vi nhiu s liu, chng t l cc

cch th nhanh hn dng o nhim hu c u c lin quan vi BOD 5 ngy. Mt trong nhng

bt tin ca phng php ny l phi i 5 ngy mi c kt qu. Nhiu c gng thc hin t

cng kt qu nh BOD 5 ngy trong mt thi gian ngn hn (3 hoc 2,5 ngy) bng cch dng nhit

cao hn (270C hoc 350C tng ng). Mt s nc kh hu rt nng, th BOD 3 ngy c th l

thc t hn. y khng phi l vn tit kim thi gian m do cc vi sinh vt phn hy v oxi ho

cc cht hu c quen sng nhit 250C v 300C. Tuy nhin, hu ht cc nc kh hu nng

vn dng phng php th BOD c in 5 ngy vi cch lm lnh mu th.

Mt s ngi dng cch th 3 ngy, em so snh kt qu v tm cc mi lin quan vi th 5 ngy.

Mt nghin cu so snh cho thy rng hai cch th t khi khc nhau qu 5%.

TCVN 6001 : 1995

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Mt cch khc l th BOD 7 ngy 200C. D nhin khng cn c s khc bit v cch lm v mu

so vi tiu chun 5 ngy, v tng quan gia hai phng php cng d dng nhn thy. Th 7 ngy

c dng Thy in t lu. Th 7 ngy 180C cng c nghin cu.

Mt im quan trng trong mi ci bin ny l phn ng gp ca vi sinh vt nitrat ha. Mi so snh

v quan h u quy v kt qu BOD tng s khng dng ATU, v do khng thy c mc ng

gp do nitrat ha vo BOD o c khi dng nhit v thi gian khc nhau. C tng nhit v

tng thi gian u lm tng mnh kh nng xy ra s nitrat ha. iu dn n nhu cu tng

ATU ln nng cao hn nhiu so vi 2,0mg/l nh trnh by trong tiu chun ny.

Dng nh khng th thit lp c mt h s chuyn BOD khng tiu chun (nhit v thi gian

) v BOD tiu chun, nht l khi phn tch mt dy cc dng mu khc nhau.

cng l tnh trng chung vi hu ht cc cch th kinh nghim, bao gm c cc cch th nhu cu

oxi chung khc nh gi tr COD v pemanganat. C th l thit lp h s chuyn ch cho mt chng

loi mu hn ch no . Th d gi tr BOD 7 ngy, dng ATU, mu nc sa lng ln u v ln

cui, cao hn BOD tiu chun tng ng l 1,09 v 1,29.

Ngoi tr trng hp tht r rng, nhng kt qu BOD khng tiu chun cn thng bo km theo

y iu kin m khng nn c gng chuyn thnh BOD tiu chun.

____________________