nghien cuu xu ly nuoc thai sinh hoat bang bai loc ngam trong cay dong chay ngang 1495

7/26/2019 Nghien Cuu Xu Ly Nuoc Thai Sinh Hoat Bang Bai Loc Ngam Trong Cay Dong Chay Ngang 1495

1/20

B GIO DC V O TO HI PHNG

TRNG I HC DN LP HI PHNG

-----------O0O-----------

ISO 9001:2008

TI NGHIN CU KHOA HC

Ch nhim ti :ThS. Hong Th ThuB mn Mi Trng - i hc Dn Lp Hi Phng

Hi Phng 2010


2/20

DANH MC CC CH VIT TT

STT K hiu ngha

1 BOD Nhu cu oxy sinh ho

2 B&V Vi khun v virt

3 CHC Cht hu c

4 COD Nhu cu oxy ho hc

5 CS Cc cht keo

6 DEWATS Xl nc thi phn tn

7 DO Hm lng oxy ha tan

8 FWS Cc hthng chy trn bmt

9 HM Kim loi nng

10 HSF Cc hthng vi dng chy ngang di mt t

11 KHCN Khoa hc cng ngh

12 KHKT Khoa hc k thut

13 NXB Nh xut bn

14 GSTSKH Gio s Tin s khoa hc

15 RO Cc cht hu c khphn hu

16 SS Cht rn l lng

17 TCVN Tiu chun Vit Nam

18 T-N Tng hm lng nit

19 T-P Tng hm lng photpho

20 TSS Tng hm lng cc cht rn l lng

21 VSF Cc hthng dng chy ng

22 VSV Vi sinh vt


3/20

DANH MC BNG

STT Tn bng Trang1 Bng 1.1. c tnh ca nc thi sinh hot thng thng 3

2 Bng 2.1. Kt qu cc thng s nhim c x l trong h

thng vi Q = 700 (l/ng)26


thng vi Q = 1 (m3/ng)28


thng vi Q = 1,5 (m3/ng)30


thng vi Q = 2 (m3/ng)31






thng vi Q = 3 (m3/ng) (ln th1)36


thng vi Q = 3(m3/ng) (ln th2)38


4/20

DANH MC HNH V

STT Tn hnh Trang

1 Hnh 1.1. S nguyn tc hot ng ca bi lc ngp nc

trn bmt14

2 Hnh 1.2. S nguyn tc hot ng ca bi lc ngm dng

chy ngang15

3 Hnh 1.3. S nguyn tc hot ng ca bi lc ngm dng

chy ng17

4 Hnh 1.4. Cy sy 18

5 Hnh 2.1. M hnh th nghim 23

6 Hnh 2.2. Biu thhin hiu sut xl ca hthng vi

Q = 700 (l/ng)27


Q = 1 (m3/ng)

28


Q = 1,5 (m3/ng)

30


Q = 2 (m3/ng)

32


Q =2,5 (m3/ng)34


Q = 2,8 (m3/ng)

35

12 Hnh 2.8. Biu thhin hiu sut xl ca hthng viQ = 3(m3/ng) (ln th1)

37


Q = 3(m3/ng) (ln th2)

39


5/20

Bo co nghin cu khoa hc Bmn Mi trng -HDLHP

Ch nhim ti - ThS. Hong Th Thu 0

MC LC

M U ......................................................................................................................... 1

CHNG I: TNG QUAN........................................................................................... 2

1.1. Mt s khi nim .................................................................................................... 2

1.2. Tnh hnh nhim ca nc thi sinh hot ......................................................... 2

1.3. Mt s ch tiu nh gi cht lng nc ............................................................ 3

1.3.1. pH ...............................................................................................................................3

1.3.2. c ........................................................................................................................3

1.3.3. Mi .............................................................................................................................4

1.3.4. Hm lng cht rn ..................................................................................................4

1.3.5. Hm lng oxy ha tan (DO) ...................................................................................4

1.3.6. Nhu cu oxy sinh ha (BOD) ...................................................................................51.3.7. Nhu cu oxy ha hc (COD) ....................................................................................5

1.3.8. Tng hm lng Nit (T-N)......................................................................................5

1.3.9. Tng hm lng photpho (T- P) ..............................................................................6

1.3.10. Tiu chun vi sinh .................................................................................................6

1.4. Nguyn l cng ngh x l nc thi ................................................................ 6

1.4.1. Kho st v nh gi mc nhim ..................................................................6

1.4.2. Mt s phng php x l nc thi ....................................................................7

1.4.2.1. X l nc thi bng phng php c hc........................................................ 7

1.4.2.2. X l nc thi bng phng php ha hc v ha l..................................... 8

1.4.2.3. X l nc thi bng cc phng php sinh hc ........................................... 10

1.5. Gii thiu v cy sy ......................................................................................... 17

1.6. Vai tr ca cy sy trong h thng t ngp nc...........................................181.7.Mt s nghin cu trn th gii v ti Vit Nam ............................................ 18

CHNG II: PHNG PHP, I TNG, NI DUNG NGHIN CU........ 21

2.1. Phng php nghin cu..................................................................................... 212.1.1. Phng php phn loi, h thng ho l thuyt...................................................21

2.1.2. Phng php phn tch tng hp ti liu .............................................................21

2.1.3. Phng php Pilot ..................................................................................................21

2.1.4. Phng php phn tch ..........................................................................................21

2.2. i tng nghin cu...........................................................................................22

2.3. Ni dung nghin cu............................................................................................. 22

2.3.1. Qun l nc thi phn tn ....................................................................................22

2.3.2. M hnh th nghim .................................................................................................22

2.3.3. Thitk th nghim ..................................................................................................25


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2.4. Kt qu................................................................................................................ 26

2.4.1. Kt qu phn tch cc thng s nhim c x l trong h thng th

nghim vi Q = 700 (l/ng) ............................................................................................26

2.4.2. Kt quphn tch cc thng s nhim c x l trong h thng th

nghim vi Q = 1( m

3

/ng) .............................................................................................282.4.3. Kt qu phn tch cc thng s nhim c x l trong h thng th

nghim vi Q = 1,5 ( m3/ng) ........................................................................................29


nghim vi Q = 2 ( m3/ng) ...........................................................................................31


nghim vi Q = 2,5 ( m3/ng)) .......................................................................................33


nghim vi Q = 2,8 (m3/ng) .........................................................................................352.4.7. Kt qu phn tch cc thng s nhim c x l trong h thng th

nghim vi Q = 3 (m3/ng) (ln th 1) .........................................................................36


nghim vi Q = 3 ( m3/ng) (ln th 2) ........................................................................38

CHNG III: KT LUN V KIN NGH .............................................................41

3.1. Kt lun ..................................................................................................................41

3.2. Kin ngh ................................................................................................................42

TI LIU THAM KHO............................................................................................. 44


7/20




8/20



M U

nhim mi trng nc l mt vn ln m Vit Nam ang phi i

mt. Hu ht nc thi sinh hot cng nh nc thi cng nghip khng c

x l m c thi trc tip vo mi trng, gy nhim nghim trng ngun

nc mt, nc ngm, tc ng xu n iu kin v sinh v nh hng trc

tip n sc khe cngng.

X l nc thi bng bi lcngm v ang c p dng ti nhiu ni

trn th gii vi u in l r tin, d vn hnh ng thi mc x l nhim

cao. y l cng ngh x l nc thi trong iu kin t nhin, thn thin vi

mi trng, cho php t hiu sut cao, chi ph thp v n nh, ng thi lm

tng gi tr a dng sinh hc, ci to cnh quan mi trng, h sinh thi ca aphng. Mt khc, Vit Nam l nc nhit i, kh hu nng m, rt thch hp

cho s pht trin ca cc loi thc vt thy sinh. Do vy, ti la chn ti

nghin cux l nc thi sinh hotbngbi lc ngm trng cy dng chy

ngang.


9/20



CHNG I: TNGQUAN

1.1. Mt s khinim[16]

- nhim mi trng l s bin i cc thnh phn mi trng khng ph hp

vi tiu chun mi trng, gy nh hng xu n con ngi v sinh vt.

- Nc thi l nc qua s dng vo cc mc ch nh sinh hot, dch v,

ti tiu thy li, ch bin cng nghip, chn nui ... Thng thng nc thi

c phn loi theo ngun gc pht sinh ra chng.

-Nc thi sinh hot hay l nc thi t cc khu dn c bao gm nc sau khi

s dng t cc h gia nh, bnh vin, c quan, khch sn, trng hc, khu vc

thng mi v cc khu vui chi gii tr.

1.2.Tnh hnh nhim ca nc thi sinh hot[5]

Phn ln nc thi sinh hot cc khu dn c th, ven v nng thn

Vit Nam u cha c x l ng cch. Nc thi t cc khu v sinh mi

ch x l s b, cha t yu cu x ra mi trng ha cng dng nc thi

sinh hot t nh bp, tm, git ... l nguyn nhn gy nhim, lan trn dch

bnh. V vy trong iu kin hin nay, khi m cc d n thot nc v x l

nc cha c a n mi ni, nu c th cng ch dng li tnh trng thotnc ma v khc phc tnh trng ngp, ng, v cn rt nhiu chi ph vn

hnh, bo dng cc h thng , th vic nghin cu lm sch nc thi cho

cc h gia nh, hay cc cm dn c, bng cc cng ngh ph hp, n gin, c

chi ph xy dng v vn hnh thp, va m bo v sinh mi trng l mt

hng gii quyt hp l, kh thi.

Nc thi sinh hot thng thng thng c nhng c tnh sau:


10/20



Bng 1.1. Cc c tnh ca nc thi sinh hot thng thng[1]

Ch tiuNng

Cao Tr ung bnh Thp

BOD5 400 220 110

COD 1000 500 250

m hu c 35 15 8

m amn 50 25 12

TN 85 40 20

TP 15 8 4

TSS 1200 720 350

SS 350 220 100

1.3.Mt s ch tiu nh gi cht lng nc[3][2][6]

1.3.1.pH

pH ca nc c c trng bng nng ion H+trong nc. Gi tr pH trong

nc thi c ngha quan trng trong qu trnh x l, tnh cht ca nc c

xc nh theo cc gi tr khc nhau ca pH.

pH = 7: Nc trung tnh.

pH > 7: Nc mang tnh kim.

pH < 7: Nc mang tnh acid.

Gi tr ca pH cho php ta quyt nh x l nc thitheo phng php thch

hp, hoc iu chnh lng ha cht cn thit trong qu trnh x l nc. Cc

cng trnh x l nc thi p dng cc qu trnh sinh hc hot ng pH nm

trong gii hn t 6,5 9,0. Mi trng thun li nht vi khun pht trin

thng c pH t 7 8. Cc vi khun khc nhau th c gii hn pH khc nhau. Vd vi khun Nitrit pht trin thun li nht vi pH t 4,8 8,8; vi khun Nitrat

pht trin thun li nht pH t 6,5 9,3; vi khun lu hunh pht trin ti mi

trng c pH t 1 4.

Ngoi ra, pH cn nh hng n qu trnh to bng cn ca cc b lng nhto

bng cn bng phn nhm, phn st, PAC...

1.3.2. c

Nc t nhin sch thng khng cha cht rn l lng nn trong sut v

khng c mu. c do cc cht rn l lng gy ra. Nhng ht vt cht gy


11/20



c thng hp ph kim loi cng cc vi sinh vt gy bnh. Nc c cn ngn

cn qu trnh chiu sng ca mt tri xung y thy vc lm gim qu trnh

quang hp v dntigimnng oxy ha tan trong nc.

1.3.3. Mi

Mi hi thi kh ngi ca nc thi do cc cht hu c ca nc thi b

phn hy, mi ca ha cht, du m trong nc. Cc cht c mi nh NH3, CH4,

H2S, cc amin, cc hp cht hu c cha lu hunh.

C th xc nh mi ca nc theo phng php n gin sau: Mu nc c

trong bnh y np kn, lc khong 10 20 giy sau m np, ngi mi ri

nh gi khng mi, mi nh, trung bnh, nng v mi rt nng.

1.3.4. Hm lng cht rnTng cht rn (TS) l thng s quan trng c trng nht ca nc thi. N

bao gm cc cht rn ni l lng v keo tan. Cc cht rn l lng c th dn n

lm tng kh nng lng bn v iu kin k kh khi thi nc vo mi trng

m khng qua x l.

TS c xc nh bng trng lng th phn cn li khi cho bay hi 1lt nc

trn bp cch thy ri sy kh 103oC cho n khi trng lng khng i. n

v tnh bng mg/l (hoc g/l).

1.3.5. Hm lng oxy ha tan (DO)

Hm lng oxy ha tan l mt trong nhng ch tiu quan trng nht v oxy

khng th thiu c vi cc sinh vt. Oxy trong nccbsung tkhng

kh v thcvtthusinh trong ncquang hp, bnh thngoxi ho tan trong

nckhong8 10 mg/l. N duy tr qu trnh trao i cht sinh ra nng lng

cho s sinh trng, sinh sn v ti sn xut. Khi thi cc cht thi vo ngun

nc, qu trnh oxy ha chng s lm gim nng oxy ha tan trong cc

ngun nc ny, thm ch c th e da s sng ca cc loi c cng nh cc

sinh vt trong nc.

Vic xc nh thng s oxy ha tan c ngha quan trng trong vic duy tr iu

kin hiu kh trong qu trnh x l nc thi. Mt khc, lng oxy ha tan cn

l c s ca php phn tch xc nh nhu cu oxy sinh ha.


12/20



1.3.6. Nhu cu oxy sinh ha (BOD)[2]

BOD l lng oxy cn thit m vi sinh vt s dng trong qu trnh oxy h a

cc cht hu c d phn hy c trong nc.

Phng trnh tng qut biu din nh sau :

Cht hu c + O2 vtVi sinh CO2+ H2O + Sinh khi

Ch s BOD l thng s quan trng nh gi mc nhim ca nc, BOD

cng cao chng t lng chthu c c kh nng phn hy sinh hc trong nc

nhim cng ln.

Trong thc t, kh xc nh c ton b lng oxy cn thit cc vi sinh vt

phn hy cc cht hu c c trong nc m ch xc nh c lng oxy cn

thit trong 5 ngy nhit 20

o

C trong bng ti. Mc oxy ha cc cht huc khng u theo thi gian. Thi gian u, qu trnh oxy ha xy ra vi cng

mnh hn v sau gim dn.

1.3.7. Nhu cu oxy ha hc (COD)[2]

COD l lng oxy cn thit cho ton b qu trnh oxy ha cc cht hu c

trong mu nc thnh CO2v H2O bng tc nhn oxy ha mnh.

Trong thc t, COD c dng rng ri nh gi mc nhim cc cht

hu c c trong nc. Do vic xc nh ch s ny nhanh hn bng cch dngmt cht oxy ha mnh trong mi trng acid oxy ha cht hu c.

V d dng cht xy ha mnh nh K2Cr2O7th phng trnh phn ng nh sau:

Cht hu c + Cr2O7-2

+ H+

42SOAg

CO2+H2O + Cr3+

Sau em o mt quang ca dung dch phn ng trn, da vo ng

chun xc nh gi tr COD. V ch s COD biu th c lng cht hu c

khng b oxy ha bi vi sinh vt nn gi tr COD bao gi cng cao hn gi trBOD.

1.3.8. Tng hm lng Nit (TN)

Tng Nit l tng cc hm lng nit hu c, amoniac, nitrit, nitrat,chng

c vai tr quan trng trong h sinh thi nc. V vy trong x l nc thi cng

vi cc ch s trn ngi ta cn phi xc nh ch s tng Nit.

Hm lng nit hu c c xc nh bng phng php Kendal.Tng nit

Kendal l tng nit hu c v nit amoniac. Ch tiu amoniac thng c xc


13/20



nh bng phng php so mu hoc chun cn nitrit v nitrat c xc nh

bng phng php so mu.

xc nh c tng nit theo phng php Kendal ngi ta ph mu bng

H2SO4c nng, khi cc dng nit hu c chuyn v dng ion NH4+chuyn

thnh NH3sau tch NH3c ct tch ra v xc nh bng chun .

1.3.9. Tng hm lng photpho (TP)

Hp cht ca Phospho tn ti trong nc vi cc dng H2PO4-, HPO4

2-,

PO43- cc polyphosphate nh Na3(PO3)6v phosphor hu c.y l mt trong

nhng ngun dinh dng cho thc vt di nc,gy nhim v gp phn thc

y hin tng ph dng cc thy vc.

Hm lng phospho tha trong nc thi lm cho cc loi to,cc loi thcvt ln pht trin mnh lm gy tc cc thy vc. Hin tng to sinh trng

mnh (hin tng ph dng) do nc tha dinh dng,thc cht l hm lng

phospho trong nc cao.Sau to v vi sinh vt b t phn,thi ra lm cho

nc b nhim th cp,thiu xi ha tan v lm cho tm c bcht.

Trong nc thi ngi ta xc nh hm lng TP xc nh t s

BOD5:N:P phc v cho vic la chn phng php x l nc thi. Ngoi ra cng c

th xc lp t s gia P v N nh gi mc dinh dng c trong nc.

1.3.10. Tiu chun vi sinh[6]

Trong nc thi thng c rt nhiu loi vi khun c hi c bit l nc

thi bnh vin.Trong vi khun E.Coli l loi vi khun c trng cho s nhim

trng nc.Ch s E.Coli chnh l s lng vi khun ny c trong 100ml nc.

c tnh mi ngymingi bi tit 2.1011E.Coli.

Theo tiu chun WHO ngun nc cp cho sinh hot c ch s E.Coli 10

E.Coli/100ml nc, Vit Nam ch s ny l 20E.Coli/100ml nc.

1.4. Nguyn l cng ngh x l nc thi

1.4.1. Kho st v nh gi mc nhim[8][12]

tin hnh x l mt ngun nc thi trc ht cn phi bit thnh phn

cc cht nhim v ngun pht sinh chng.Phi phn tch chnh xc ch tiu

khng th ch tin hnh phn tch mt mu,m phi phn tch nhiu mu vi

mc ch l tm s bin i gia cc ch tiu trong mi trng.Hin nay cnhiu c s x l nc thi,nhng khng t trong s khng p ng c


14/20



yu cu x l. p ng c yu cu v mc ch s dng,trong cng ngh

x l nc thi phi sdng nhiu qu trnh khc nhau, c thphn thnh cc

cng on x l:

- X l cp I (x l s b): Gm cc qu trnh x l s b v lng loi cc

cht rn ln nh rc,ct x v bn cn, kh trng dit vi khun gy bnhdch,

kh cc cht c hi v m bo iu kin bnh thng ca cc cng trnh x l

sinh hc.

- X l cp II (x l th cp): Gm cc qu trnh sinh hc (i khi c c ha

hc).Nhim v chnh ca qu trnh ny l tch cc tp cht hu c ha tan c

th phn hy bng con ng sinh hc (ngha l lm gim ch s BOD) khi

x ra ngun nc thi khng gy thiu ht xy v mi hi thi cho ni tipnhn. Cc cng on ny bao gm cc qu trnh: hot ha bn, lc sinh hc hay cc

h sinh hc .........

- X l cp III (x l tng cng): Thng thng cc cng on ny ch cn kh

khun m bo nc trc khi vo cc thy vc khng cn vi sinh vt gy

bnh,kh mu,mi v m bo oxi cho ngun tip nhn. Cc phng php kh

khun thng dng l: Clo ha ngun nc,zn ha hoc chiu tia cc tm.

Vit Nam hin nay phng php kh khun bng clo dng kh, dng lng,cchipoclorit l hay c dng hn c.

Nhn chung, tt c cc phng php v cc qu trnh x l nc thi u da

trn c s cc qu trnh vt l,ha hc v sinh hc. Cc h thng x l nc

thi thng bao gm hng lot cc qu trnh trn,c kt hp to ra mt

dy chuyn cng ngh thch hp, ty thuc vo c tnh ca nc thi, tiu

chun dng ra v mc cn thit lm sch nc thi,lu lng nc thi cn

x l,tnh hnh a cht v thy vn,iu kin in,nc,kinh ph .

1.4.2. Mts phng php x l nc thi.

1.4.2.1. X l nc thi bng phng php c hc[15]

Thc cht phng php x l c hc l loi cc tp cht khng ha tan ra

khi nc thi bng cch gn,lc v lng.

Trong phng php ny thng ng dng cc cng trnh sau y :


15/20



- Song v li chn rc: loi b cc loi rc v cc tp cht c kch thc ln

hn 5 mm thng dng song chn rc,cn cc tp cht nh hn 5mm thng

dng li chnrc.

- B lng ct c ng dng loi cc tp cht v c v ch yu l ct trong nc thi.

- B vt m, du: Cc loi cng trnh ny thng c ng dng khi x l nc thi

cng nghip, nhm loi b cc tpcht nh hn nc: m, du m.v tt c cc

dng cht ni khc. i vi nc thi sinh hot, khi hm lng m khng cao thng

vic vt m thc hin ngay b lng nh cc thanh gt b tr trong b lng.

- B lng c ng dng loi cc cht l lng c t trng ln hn hoc nh

hn t trng ca nc.Cc cht l lng c t trng ln hn t trng ca nc s

lng xung di b,cn cc cht c t trng nh hn ca nc s ni ln trnmt nc.

- B lc c ng dng loi cc tp cht l lng kch thc nh b bng cch

lc chng qua li lc c bit hoc qua lp vt liu lc.

Trng hp khi mc lm sch khng cao lm v cc iu kin v sinh cho

php th phng php x l c hc gi vai tr chnh trong trm x l.Trong cc

trng hp khc,phngphp x l c hc ch l giai on lm sch s b

trc khi x l sinh ha.1.4.2.2. X l nc thi bng phng php ha hc v ha l[15]

+ Phng php ha hc: Thc cht ca phng php ha hc l a vo nc

thi cht phn ng no .Cht ny tc dng vi cc tp cht bn trong nc

thi v c kh nng loi chng ra khi nc thi di dngbay hi, kt ta hay

ha tan khng c hihoc t c hi hn.

+ Phng php ha l: L phng php x l ch yu da trn cc qu trnh vt

l gm cc qu trnhc bn nh trung ha, tuyn ni,keo t,to bng, ly tm,

lc,chuyn kh,hp ph,trch ly, c bay hi Ty thuc vo tnh cht ca tp

cht v mc cn thit phi lm sch m ngi ta s dng mt hoc mt s

phng php k trn.

- Trung ha: Nc thi thng c nhng gi tr pH khc nhau,mun nc thi

c x l tt bng phng php sinh hc phi tin hnh trung ho v iu

chnh pH v vng 6,6 7,6. Trung ho bng cch dng cc dung dch acit hocmui acit, cc dung dch kim hoc oxit kim trung ho dch nc thi.


16/20



- Trao i ion: Thc cht ca phng php trao i ion l mt qu trnh trong

cc ion b mt ca cht rn trao i vi cc ion c cng in tch trong dung

dch khi tip xc vi nhau. Cc cht ny gi l cc cht trao i ion, c hng hon

ton khng tan vo nc. Cc cht trao i ion c th l cc cht v c hoc hu

c c ngun gc t nhin hay tng hp.

- Keo t: Trong qu trnh lng c hc ch tch c cc ht rn huyn ph nh

c kch thc 10-2mm, cn cc ht nh hn dng keo khng th lng c.

Ta c th tng kch thc cc ht nh tc dng tng h gia cc ht phn tn

lin kt vo thnh tp hp cc ht c th lng c. Mun vy trc ht cn

trung ho in tch ca chng, th n l lin kt chng li vi nhau. Qu trnh

to thnh cc bng ln t cc ht nh gi l qu trnh keo t.- Hp ph: Phng php hp ph c dng loi cc tp cht bn ho tan vo

nc m phng php x l sinh hc cng cc phng php khc khng loi b

c vi hm lng rt nh. Thng thng, y l cc hp cht ho tan c c

tnh cao hoc cht c mu, mi, v rt kh chu.

Cc cht hp ph thng dng l than hot tnh, t st hot tnh, silicagen, keo

nhm, mt s cht tng hp hoc cht thi trong qu trnh sn xut nh x tro,

mt st, trong than hottnh c dng nhiu nht.- Tuyn ni: Phng php tuyn ni da trn nguyn tc cc phn t trong nc

c kh nng t lng km, nhng li c kh nng kt dnh vo cc bt kh ni ln

trn b mt nc, sau ngi ta tch ccbt kh. Trong mt s trng hp,

qu trnh ny cng dng tch mt s cht ho tan nh cht hot ng b mt.

Qu trnh ny c thc hin nh thi khng kh thnh cc ht bt nh vo

trong nc thi. Cc bt kh dnh cc ht l lnglng km v ni ln trn b mt

nc. Khi ni ln cc bt kh hp thnh bng ht ln ri to thnh mt lp

bt cha nhiu ht cht bn.

- Kh khun: Dng cc ho cht c tnh c i vi vi sinh vt, to, ng vt

nguyn sinh, giun sn lm sch nc, m bo tiu chun v sinh

vo ngun nc hoc ti s dng. Kh khun hay st khun c th dng ho

cht hoc cc tc nhn nh ozon, tia t ngoi...... Ho cht kh khun phi m

bo c tnh c vi vi sinh vt trong thi gian nht nh, sau phi c phn


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hu hoc bay hi, khng cn d lng gy c cho ngi s dng hoc vo cc

mc ch khc.

Ph thuc vo iu kin a phng v mc cn thit x l m phng

php ho hc hay phng php ho l l giai on cui cng (nu mc x l

t yu cu, c th x nc ra ngun) hoc ch l giai on s b (th d kh

mt vi cc lin kt c hi nh hng n ch lm vic bnh thng ca cc

cng trnh x l).

1.4.2.3. X l nc thi bng cc phng php sinh hc

X l nc thi bngphng php sinh hc da trn hot ng sng ca

sinh vtnhvi khun d dng hoi sinh c trong nc thihay thcvtsng

trong ncthi. Thc cht ca phng php sinh hc l da vo hot ng sinhtn ca sinh vt phn hy cc cht hu chay hpthcc cht nhimc

trong nc thi. Chng s dng ngun cht hu c v cc cht khong lm

ngun dinh dng v to nng lng. Trong qu trnh dinh dng, chng nhn

c cc cht lm vt liu xy dng t bo, sinh trng v sinh sn nn sinh

khi c tng ln. i vi nc thi c tp cht v c th phng php ny

dng kh cc sunfit, mui amoni, nitrat (tc l cc cht cha b oxy ho hon

ton).[7][13]

Phng php sinh hc ngy cng c sdng rng riv phng php

ny c nhiu u im hn cc phng php khc[14]

- Phn hu cc cht trong nc thi nhanh, trit m khng gy nhim mi

trng.

- To ra c mt s sn phm c ch s dng trong cng nghip v sinh hot

(biogas, etanol ), trong nng nghip (phn bn).

- Thit b n gin, phng php d lm, chi ph tn km t hn cc phng php khc.

Nguyn tc c bn ca phng php sinh hcx l nc thi l dng h

sinh vt phn hu, hpth, hpphcc cht c trong nc thi to nn cc sn

phm khng gy hi cho mi trng. Cc sn phm ca qu trnh c th c s

dng trong nhiu lnh vc ca i sng sn xut nh to ra biogas, toprotein

trong sinh khi ca sinh vt lm thc n gia sc H vi sinh vt tham gia

trong x l nc thi c nhiu loi nh nm men, nm mc, x khun. Tu theo


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h vi sinh vt s dng m c phng php x l thch hp theo hng x l

ym kh, x l hiu kh hay x l ty tin.[6][10]

Phng php hiu kh

X l nc thi bng phng php hiu kh da trn nhu cu oxy cn cung cp

cho vi sinh vt hiu kh c trong nc thi hot ng v pht trin. Qu trnh ny

ca vi sinh vt gi chung l hot ng sng, gm hai qu trnh: dinh dng s

dng cc hp cht hu c, cc ngun nit v photpho cng nhng ion kim loi

khc nhau vi mc vi lng xy dng t bo mi, pht trin tng sinh

khi, phc v cho sinh sn, phn hu cc cht hu c cn li thnh CO2v H2O.

Qu trnh sau l qu trnh phn hu vi dng oxy ho cc hp cht hu c, ging

nh trong qu trnh h hp ng vt bc cao. C hai qu trnh dinh dng voxy ho ca vi sinh vt c trong nc thi u cn oxy. p ng c nhu

cu oxy ny ngi ta phi khuy o khi nc thi oxy trong khng kh

c khuych tn, ho tan vo trong nc. Song bin php ny cha th p

ng c y nhu cu v oxy. Do vy ngi ta s dng cc bin php hiu

kh tch cc nh thi kh, thi bng kh nn hoc qut gi, vi p lc cao kt hp

khuy o. Cc bin php ny thng c s dng trong cc cng trnh x l

nc thi bng bin php hiu kh nhn to nh: Cc b phn ng sinh hc hiukh, cc b lc sinh hc, cc loi a quay sinh hc

Phng php ym kh

Qu trnh phn hu cht hu c trong iu kin ym kh do mt qun th vi sinh

vt (ch yu l vi khun) hot ng khng cn s c mt ca oxy khng kh, sn

phm cui cng l mt hn hp kh c CH4, CO2, N2, H2S, NH3 trong c

ti 65% l kh CH4. V vy qu trnh ny cn gi l qu trnh ln men Metan v

qun th sinh vt c gi l vi sinh vt Metan.

Phng php ym kh ch yu dng cho loi nc thi c nhim cao.

Qu trnh lm sch nc thi tin hnh trong b kn m bo iu kin ym kh.

Cho nc thi vo b vi sinh vt ym kh s tin hnh phn hu cht h c

trong nc thi theo 2 giai on:

- Giai on ln men acit: Nhng hidratcacbon d b phn hu sinh ho thnh cc

acit bo vi khi lng phn t thp. Khi pH mi trng gim xung n 5hoc thp hn, c km theo mi hi.


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- Giai on Metan ho: giai on ny cc vi sinh vt k kh chuyn ho cc

sn phm ca pha acit thnh CH4v CO2. Cc phn ng ny chuyn pH ca mi

trng sang kim.

H vi sinh vt ln men ym kh thng c sn trong nc thi. Tuy nhin

tng tc phn gii, nng cao nng sut hot ng ca cc b Metan, c th

phn lp, nui cy cc vi sinh vt thch hp cung cp thm cho b. Cc nhm

vi sinh vt thng gp trong qu trnh ny l: Metanococcus, Metanobacterium,

Metanosarcina

X l nc bng thc vt thu sinh[4,11]

Thy sinh thc vt l nhng loi thc vt sinh trng trong mi trng

nc, thc t n c th gy nn mt s bt li cho con ngi do vic pht trinnhanh v phn b rng ca chng. Tuy nhin li dng chng x l nc thi,

lm phn compost, thc n cho gia sc khng nhng c th gim thiu nhng

bt li gy ra bi chng m cn thu thm c li nhun, c nhng loi thy

thc vt sau:

a) Thu thc vt sng chm:Loi thu thc vt ny c r v thn di mt

nc, loi c s dng nhiu l to, rong. Trong h thng ny cc loi rong to

c th xung di nc v s c mt ca chng lm gim CO2 do CO2 l

nguyn liu ca qu trnh quang hp, tng O2 ha tan trong nc. Kt qu l

tng pH, to iu kin ti u cho s bay hi ca NH4v lng ng ca pht pho.

DO cao cn lm tng tc khong ha cc hp cht hu c. Ngita thng

p dngxl ncthiph dng(chanhiucc hpchtcaphotpho v

nit) v nc thi x l khng c php c c cao v nh vy s ngn cn

nh sng chiu xung di nc, lm gim qu trnh quang hp. Sau rong

tocvtln khihthngxl, c thlm nguyn liucho biogas hoc

chbinthcn gia sc, lm phn bn.

b) Thu thc vt sngni trn mt nc: R ca thc vt ny khng bm vo

t m l lng trong nc, thn v l ca n pht trin trn mt nc. N tri

ni trn mt nc theo gi v dng chy, loi c s dng nhiu nht l bo

ty. Trong x l nc thi bo ty c nhng vai tr sau:

- L ca cy bo ty xy ra quang hp vo ban ngy nn chng cung cp mtlng ln O2cho vng r v vng b mt thc y qu trnh phn hy hiu kh


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cc hp cht hu c cng nh qu trnh nitrat ha cc hp cht nit, vic tng

DO trong nc cn thc y qu trnh lng ng photpho trong nc.

- Bo ty sinh sn rt nhanh trong mi trng nc thi, do vy sau mt thi

gian ngn chng s to thnh b mng c tc dng gim nh sng mt tri nn

lm gim s pht trin ca to, ng thi lm gim tc ng ca gi ln b mt

ao h n n gim sng v dng chy; chng cng c tc dng lm gim s

xo trn bi nhit gia cc tng nc. Chnh nhng iu lm tng kh nng

lng ng ca ca cc cht l lng c trong nc thi.

- Bo ty c c im l c b r rt pht trin gm rt nhiu r nh liti, chng

l gi th cho rt nhiu vi sinh vt trong nc thi bm dnh, to iu kin tt

nht cho s tip xc gia cht nhim v vi sinh vt trong nc thi, tc l thcy qu trnh x l nc thi nhanh hn.

- B r ca bo ty c din tch b mt rt ln, do vy n c kh nng ht rt

nhiu cc cht l lng, lm trong nc.

- Pha di ca ao h xy ra qu trnh phn hy k kh cc hp cht ca cacbon

v kh nitrat, trong s cc sn phm to ra l kh c v c mi kh chu,

nhng do pha trn ca ao h c bo nn cc kh ny b hp th do vy

nhng vng x l ng quy cch chng ta s khng pht hin c mi canhng kh ny.

- Trong qu trnh sng bo c nhu cu s dng cc dng cht cn thit nh

m, ln, cc cht vi lng nh kim loi nng.....Do vy chnh bo ty cng

tham gia trc tip vo vic x l cc cht nhim trong nc thi.

- Bo ci to cnh quan sinh thi ca khu vc, nn trang tr bo trn mt nc

to ra cc kiu dng p mt v c th kt hp vi mt s loi thc vt thy sinh

khc nh sen, sng....

- Bo ty cn gp phn vo lm tng a dng sinh hc cho vng thc hin chc

nng x l nc thi nh thu ht cc loi chim t ni khc n, tng cc loi b

st, lng th, cc loi thy sinh vt.......

- Khi thu hoch bo c th lm phn hu c, to kh biogas, lm thc n cho gia

sc gia cm, lm th cng m ngh.....

c) Thy thc vt c thn trn mt nc(r bm vo y, thn vn ln trn mtnc) nh lau, sy, pht lc........

nghien cuu xu ly nuoc thai sinh hoat bang bai loc ngam trong cay dong chay ngang 1495

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