Xu Ly Nuoc Mat Lam Nuoc Cap Sinh Hoat

7/30/2019 Xu Ly Nuoc Mat Lam Nuoc Cap Sinh Hoat

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i hc quc gia H Ni Trng i hc khoa hc t nhin

Khoa Mi trng

Tiu lun X l nc mt lm nc cp sinh hot

Gio vin hng dn : PGS.TS TRNH TH THANH

Sinh vin thc hin : Nhm 3Nguyn Th L Nguyn Quang

Nam inh Th Nga Phan Th Qunh Nga Nguyn Th Hng

Nhung Phm Th Nhung L Th Phng

Lp\ K49 Cng ngh Mi trng

H Ni -2007


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Tng quan

I. Nhu cu S dng nc Vit Nam

Nc l nhu cu thit yu cho mi sinh vt, ng vai tr c bit trong vic

iu ho kh hu v cho s sng trn tri t. Hng ngy c th con ngi cn 3 - 101 nuc

cho cc hot ng sng, lung nc ny i vo c th qua con ng thc n, nc ung

thc hin cc qu trnh trao i cht v trao i nng lng, sau thi ra ngoi theo con

ng bi tit. Ngoi ra con ngi cn s dng nuc cho cc hot ng khc nh tm,

ra,...

Nc ta hin nay nhu cu s dng nc ngy cng tng do s pht trin dn s v

mc sng ngy cng tng. Tu thuc vo mc sng ca ngi dn v tu tng vng m nhu

cu s dng nc l khc nhau, nh mc cp nc cho dn th l 150 L/ngi.ngy, cho

khu vc nng thn l 40 - 70 L/ngi.ngy.

Ngun nc cung cp cho nc sinh hot nc ta ch yu l ngun nc mt, c

ly t cc sng h, sau khi qua x l s dn n cc h dn. Hin nay, hn 60 % tng cng

sut cc trm cp nc ti cc th v khu cng nghip trn c nc dng ngun nc

mt vi tng lng nc khong 3 triu m3/ ngy.m, con s ny cn tng ln nhiu trong

nhng nm ti nhm cung cp cho cc th v khu cng nghip ngy cng m rng v

pht trin.

D kin 50 nm na nuc ta s ri vo tnh trng thiu nc trm trng. S bin i

ca kh hu ton cu s dn n s suy gim ca ngun nuc. Cc kt qu nghin cu gn

y vit Nam cho thy tng lng nuc mt ca nuc ta vao nm 2025 ch bng khng 96

%, n nm 2070 xung cn khong 90 % v nm 2100 con khong 86 % so vi hin nay.

Vi tc pht trin dn s nh hin nay th dn 2025 lng nc mt tnh bnh qun u

ngui nc ta ch t khong 2.830 m3/ngi.nm. Tnh c lung nuc t bn ngoi chy

vo th bnh qun t 7.60 m3 ngi.nm.

Ti nguyn nc ti Vit Nam phn b khng u gia cc vng. Trn 60% ngun

nc tp trng ng bng sng Hng (lu vc sng M Kng) trong khi

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ton phn lnh th cn li ch c gn 40% lng nuc nhng li chim 80% dn s c nc

v trn 90% khi lng hot ng sn xut kinh doanh, dch v. c bit cc a phngvng min ng Nam B v l vc ng Nai - Si Gn, lng nc bnh qun u ngi

ch t khong 2.900 m3/ngi.nm, bng 28% so vi mc trung bnh ca c nc.

Bn cnh , ti nguyn nc ca Vit Nam cng phn b khng u theo thi gian

trong nm v gia cc nm. Lng nc trung bnh trong 4 n 5 thng ma ma chim

khong 75 - 85% trong khi nhng thng ma kh (ko di n 7 - 8 thng) li ch c khong

15 - 25% lng nuc ca c nm.

Theo nh gi ca cc nh nghin cu, tc tng trng kinh t cao khng i ivi vic lm tt cng tc bo v mi trng gy ra nhng nh hng tiu cc ti ti

nguyn nc nc ta. Tnh trng nhim ngun nc mt ngy cng tng v mc v

quy m, mt s khu vc ng bng c biu hin nhim do cc cht hu c kh phn

hu v hm lng vi khun cao. Cc biu hin suy thoi, cn kit ngun nc ang tr ln

r rt v ph bin nuc ta.

Vi nhng c im v tnh khng bn vng ca ti nguyn nc ca nuc ta, cng

tc qun l nh nc vi ti nguyn qu bu ny cn phi c tng cng tt c cc cpngay t by gi trc khi qu mun.

II. nh gi ngun nc mt ca Vit Nam

Nc ta c mng li sng ngi kh dy c, trong phi k ti cc sng

ln, trong c h thng sng M Kng, tip theo l h thng sng Hng, ng Nai, sng

M, sng C, sng Hng, sng Thi Bnh, sng Thu Bn, . ., vi din tch lun vc mi sng

trn 10.00 km2, lu lng cc sng chnh vo khong 880 Km3/nm.

Lng ma trung bnh hng nm 1960 mm, to ra nc ti to c khong 324Km3/nm.

Mt sng phn b khng u, ph thuc vo iu kin a hnh, kh hu ca tng

a phng.

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Nhn chung, cc sng nc ta c tr lng ln c kh nng cung cp cho cc i

tng dng nc trc mt v cho tng lai. Tuy nhin m bo s dng ngun ncmt c lu di cn phi c chin lc s dng hp l v bo v ngun nc mt do cc

tc ng ca con ngi gy ra.

Ngoi ngun nc mt l cc sng, h th min ni ngun nc sui cng ong vai

tr quan trng trong vic cung cp cho ngi dan vng cao.Ngun noc sui o tr lng

nc v cht lung nc thay i theo ma. Ma ma nc c c ln, hm lung cnco

v cng cha nhiu cht hu c. Tuy vy nhng tnh cht ca cn khc nc sng. Cn

y l cn th, d lng ng, thi gian lng nhanh hn nuc sng.c im ca cc ngun nc mt nc ta c th tm tt nh sau:

a. Nc sng:

Cht lng nc sng Vi Nam thay i theo ma v theo vng a l. Do dng

chy bo mn b mt khu vc to ln cc cht tri theo dng chy gm ct, bn, ph sa,...

Nc sng c hm lung cn cao vo ma ma. Tng lng cn do cc sng ra

bin trung bnh hng nm khong 200 - 250 triu tn, trong 90% c to ra vo ma l.

Vo ma l, c cao, hm lng cn ln v thay i theo tng thi k. c cao nhtxut hin trong tt c cc thng ca ma l Cc thng ma cn, khi cc sng c vn tc

dng chy nh nht th nc c c nh nht, i khi c gn t tiu chun nc

sinh hot v n ung theo tiu chun cp nc cho cc th.

Thnh phn chnh ca nc sng:

- Khong cht: Hm lng khong cht ca c sng Vi Nam cn thp ( 200 -

500 mg/L

- pH: Nc cc sng chnh c kim trung tnh (7 - 8)- cng: Nc thuc nc mm

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- Hm lng cc ion chnh: Ch yu l cc ion Ca2+, Mg2+, K+, S42', CL', HC03',...

b. Nc h:Nc ta c nhiu h t nhin nh h Ba Be, h Ni Cc, v mt s h nhn to

phc v vic ti tiu cho nng nghip. c bit mt s h c dung tich tr nc ln ca cc

cng trnh thu in Thc B, Ho Bnh, ...

Nhn chung cc h t nhin c tr lng nh, ch mt vi h ln c kh nng cung

cp nc cho cc i tng va v nh. Cc h thu in c kha nng cung cp cho cc i

tng ln.

Nc h c hm lng cn nh hn nc sng v oc lng t nhin v kh ninh. Tuy nhin hm lng cn cng dao ng theo ma, ma ma c hm lng cn ln,

ma kh hm lng cn nh, c h trong gn m bo tiu chun trong ca nc sinh

hot v n ung. S dao ng v cht lng nc thng xy ra cc vng ven b v ph

thuc vo a hnh ca vng ven b. Vng xa b v gia h c cht lng nc n nh hn.

Nc h c mu cao do rong, ru, to. Hm lng cht hu c trong h thng

cao do xc ng thc vt quanh h gy nn.

Nhn chung cht lng nc h tt, dy chuyn cng ngh x l nc c th n ginhn cng ngh x l nc sng, lng ho cht dng keo t t, do vy gi thnh x l

nuc h thng r hn nc sng.

S cng ngh x l nc b mt

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Nc th (sngh...)

H/C keo t,chnh pH

Hp cht st

trng Cl2, O3,CIO2...

MC CH

- Tch cc mnh vn vt th, vtni- Dit khun gy bnh- Hn ch mi v

Ph v th n nhh keoTo bng nh

- Kt dnh cc bng cnnh thnh bng cn ln

- Lng tch bngcn

- Lc cc bng cncn li

- Tiu dit loi b visinh vt

Tin x l

X l s b nc b mt rt quan trng. Trc khi dn nc vo dy chuyn x l,

ngi ta lu nc mt thi gian di vi mc ch:

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- To qa trnh lng t do ca cc ht bi v cc kim loi nng c nng cao trong

nc th khng tch c bng qu trnh keo t nh cban, niken, xyanua (CN),ch,caimi v cc kim loi c hi khc cng lng xung y.

- Xc tin lm sch t nhin tch c phn ln cc cht hu c nh v cc tp

cht v c.

- Cps th dng cc bin php trao i kh nhn to tng hm lng oxy ha tan

trong nc.

-X l s b vi dch vi duy tr cng ca nc t8.5-9.0 D.

Tm li, nh cc qu trnh ha, l, sinh hc t nhin xy ra trong h nn cht lngnc trong h tt hn ngun nc a vo h. Nh b sung qu trnh nhn to nn nng

to thp, cng v nng kim loi c hi gim i, kt qu l gim i rt nhiu chi

ph cho giai on tip theo.

I. KhVkhun vrut nh cc qu trnh t nhin trong h cha nc

Cc qu trnh t nhin xy ra trong h cha nc c th gim ng k lng vi sinh

vt gy bnh c mt trong nc , bi v:

- Nng cht dinh dng cn thit cho vi khun trong nc rt thp.- Nhit ca nc nh hn 37c nn tc sinh snar ca vi khun vi rt rt

chm.

- Cc ng vt nguyn sinh, nm trong nc thng l k th ca vi khun vi

- Cc ng vt nguyn sinh, nm trong nc thng l k th ca vi khun,

vi rt.

- Tia cc tm ca nh sng mt tri tiu dit vi khun lp b mt.

- Vi khun, vi rut thng b lng cng vi cc ht cntong nc

- C cht v c, cc cht c trong nc c th hy hoi vi khun, pH khng

thch hp cho vi khun.

1.2 Ngn nga s pht trin ca to

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ngn nga s pht trin ca to trong c ngun nc c th s dng cc phng

php sau y:a. S dng ha cht dit to

Ngi ta dng cc ha cht nh C11SO4 nng t 0.1-10mg/l, nhng hp cht

ca clo nng t 0.3 n 1.0 mg/1, natri sunfat, cht dit c 2.4 D. .Tuy nhin, a ha

cht c bit l cc ha cht bo v thc vt vo cc h cha khng phi l bin php ti

u.

b. Gim cht dinh dng cho to trong nc

Cc cht dinh dng nh nit, photphat trong nc c th c gim bt bng cchngn nga vic thi nc thi sinh hot, cht thi ca con ngi v ng vt cng nh cc

cht thi c cha N4+, NO3", PO43' vo ngun nc...Hoc c th p dng cc phng

php tch cht dinh dng ra ngun thi nh sau:

-X l sinh ha kt hp vi khNO3 trong iu kin ym kh.

Clo ha nng pH hoc l lm thong kh

- Tch photphat ra khi nc bng cch kt ta vi Fe3+, Al3+ hocCa(OH)2.

c. Gim cng nh sng ti h chacng nh sng xuyn qua nc theo phng trnh

I = I.E'l

Trong :

Io-cng nh sng b mt nc;

I- cng nh sng d sau d, z- h

s hp ph nh sng ca nc.

Nh vy, mun gim c lng nh sng hp ph vo nc cn tng sau hocgim h s hp ph ca nc bng cch gim c ca nc.

II. Keo tU- tUo bngDung dch keo l h bn (kh lng) nh cu trc c bit ca cc ht keo.

Trong nhm ny phi k n virus, cc cht c phn t lng ln c ngun gc t

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nhin nh axit humic. Ht keo c kch thc nh (< 0,5 |j,m) nn bng mt v hin vi thng

thng khng th nhn thy.Ht keo k nc c bn nh lp in kp tch in cng du. Ht keo a nc c

bn nh tng tc ht-nc thng qua cc chm chc a nc trn cc phn t ht keo,

II. 1. cuu TUO HUT KEO vu TNH BUN CUA HU KEO Theo Atkins hkeo l tn gi c in ca cc h phn tn d thca cc ht

c kch thc nh hn 500 nm trong mi trng khc v cht so vi cht ht ( y

ta ch cp n mi trng lng).

Tuy nhin kch thc khng phi l yu t quyt nh m cu to ht keo

mi l yu t quyt nh n tnh bn ca cc h keo.

Tu vo cu to ht v nguyn nhn gy ra bn ta c hai loi ht keo: loi

a dung mi c th l a nc (hydrophilic) v loi k dung mi hay &znc

(hydrophobic).

Loi a nc l cc dung dch cao phn t vi cc phn t cht hu c ho tan c

kch thc ln v cha nhiu nhm chc phn cc, c i lc cao vi cc phn t nc.

Loi k nc l cc loi keo c gc xit hoc hyroxit kim loi. Do kch thc ht rt

nh h keo c b mt cc ln, v vy v mt nhit ng chng khng bn v c xu th co

cm gim nng lng b mt. Mt khc do ht keo c cu to c bit ca lp in kp

to nn lc y tnh in ht-ht nn chng kh tip cn gn nhau, ht nhau v co cm

thnh ht ln hn nng c th lng c nn h ny c tnh bn.

Cu to c bit ca ht keo c th c lm r trn c s v d keo Fe(III): Khi ho

tan FeCl3 trong nc s xy ra phn ng thy phn:

FeCl3 + 3H20 -> Fe(OH)3 + 3HC1 (1)

Kt ta Fe(OH)3 co cm di dng tp hp ht [mFe(OH)3] rt nh, c gi l ht nhn, n

c kh nng hp ph nhng ion ging cc thnh phn to ra n, v


10/51

d hp ph cc ion Fe3+, to thnh lp ion Fe3+ trn b mt ht c gi l p hp

ph hay l p ion quyt nh du:

Nh vy, ta c mt ht mi mang in tch 3n+, n c xu th ht 3n cc ion tri du

(CF) trong dung dch trung ho in tch 3n+. Trong thc t khng phi tt c 3n ht cr

bm cht vo nhn m ch c 3(n-x) ht crbm vo, lp ion crbm vo ny c gi l

lp in tch tri du. Cng vi lp n ion Fe3+ hp ph c nh ta c 3(n-x) ion crbm

theo ht [mFe(OH)3] to thnh lp in kp gm 3n in tch dng v 3(n-x) in tch m,

kt qu l ht keo (phn gia du {}) mang in tch 3x+:

[m Fe(OH)3]nFe3n+ + 3(n-x) cr-> {[mFe(OH)3]nFe3"+3(n-x)Cr}3x+

Phn cn li 3x ht crtri ni trong dung dch khong khng gian gn ht, to

nn p khuyt tn. Nh vy, nu vit di dng cng thc ho hc ht keo c cu to tng

th nh sau:

Trong khng gian, ht keo c dng nh mt qu cu tch in (hnh 2.1).

Theo hnh 2 1 ht nhn l qu cu gm tp hp cc phn t Fe(OH) 3(r) nm tm.

Cc ion quyt nh du gn cht vo qu cu Cc in tch tri du lp gn nht to

thnh lp ion nghch v mt bin A-A, cc in tch tri du - phn

(2)

(3)

{[mFe(OH)3]nFe3n+3(n-x)Cr}3x+3xCr

lp hp ph (1 p ion quyt nh du)

lp in tch tri du

V lp khuch tn

Ht keo

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cn li nm lp khuch tn kh linh ng, vy quanh ht keo tch in nh m my

quanh tri t.

Lp ion tri du

Lp ion quyt nhdu hay lp hp ph

Hnh 2.1- Cu to ht keo v s thay i th theo khong cch t b mt ht keo

Tm li, ht keo trung ho v in ht keo phi c hai lp in tch tri du c

cng lng in tch: lp hp ph (v d, nFe 3+) nm trn b mt ht nhn tch in dng

hoc m (trong trng hp nFe3+

l dng), in th tng ng ca n l th nhit nghayl th Nemst, (po\ tip theo l lp ion tri du tch in ngc li (m hoc dng). Hai lp

in tch ny to nn mt cu trc tng t nh hai bn cc song song ca mt t in,

trong mt bn cc tch in dng (hoc m) gn cht vi ht nhn l lp ion quyt nh

du, cn bn cc kia tch

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in tri du v to nn lp in kp. y l cu to thng thng ca t in phng.

K thut x l nc cp t nc t nhin, v k c mt s cng on trong dychuyn x l nc thi thng thng l k thut lng - lc. e hnh dung tc lng ca

nhng ht khng tch in di tc dng ca trng trng v nh gi kh nng s dng b

lng x l lm trong nc xembng 2.1.

Ta thy cc k thut lng - lc thng thng trong ngnh nc ch c hiu qu nht

nh i vi ht c kch thc c am, trong trng hp lc tt nht l ln hn 0,1 Lim. i

vi nhng ht c 0,1 im tr xung rt kh lng v khng th lc c bng lc ct thng

thng. e c th lc chng bng lc ct thng thng phi bin chng thnh nhng ht

ln hn. Phng php ph bin thc hin vic ny l phng php keo t ngha l x l

nc bng nhng cht keo t trc khi lng - lc.

Bng 2.1 - Kch thc ht v thi gian lng do trng lc

Loi ht ng knh, Din tch b mty Thi gian

mm 2 3

m /mlng 1 m nc

Si m 10 6.102 1 s

Ct lc 1 6 103 10 s

Ct en 0,1 6.10" 120 s

Bn 0,01 6.5 2 h

Vi khun 0,001 6.1(1" 8 ngy

Ht keo 0,0001 6.10' 2 nm

Ht keo 0,00001 6J8 20 nm

Ht keo 0,000001


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10-e 10-6 10-4 10-2 10o

Nng keo t - to bng (mol/L)

Hnh2- Cc ng keo t i vi bn loi cht keo t

Li ko ht keo bng bng cn

- 'r

(a)

&

yV + 0 +yN+ +

G8-HO'.%;+;+ *

-l

(b)

(c)

Hnh 2.3- M hnh qu trnh keo t - to bng

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(a) S y gia cc ht keo cng du; (b) Hin tng co lp in kp v s ht nhan

gia cc ht keo b trung ho v in; (c) Hin tng to bng nh PAA.

cc ht keo m &/

phn t PAAkhu li thnh bng ln. ii.3 Cht keo t v cc yu t nh hng U. Phn

nhm Al2(S04)3.nH20 (n = 14+ 18)

y l cht keo t ph bin nht, c bit l Vit Nam. Khi dng phn nhm lm

cht keo t s xy ra phn ng thu phn:A12(S04)3 + 6H2O -> 2AI(OH)3 + 6H+ + 3S042 (5)

Hnh 2 4- nh hng ca pH v liu lng n kh nng gy keo t ca phn nhm

Neu trong nc thiu kim (K), pH s gim; nu K s c phn ng:


15/51

A12(S04)3 + 3Ca(HC03)2 -> 2Al(OH)3 + 3CaS04 + 6CO2 (6)

Theo phng trnh (6) c 342 mg A12(S04)3 khan, hm lng 100% cn 6 mdl K(HCO3-). Neu K trong nc khng th cn b sung vi hoc sa b, nu khng pH

s h. Lng kim cn (K) tnh theo cng thc:

K = F K + 1 = 0,0175F - K + 1 (7)

324 Trong

:

K = lng kim cn thm, ml/L ;

F = lng phn, mg/L;K = kim ca nc, ml/L.

e chuyn i ra n v g/L, i vi vi K sau khi tnh theo pt. (7) cn nhn vi 37;

i vi sa nhn vi 58.

Khi s dng phn nhm hay bt k cht keo t no khc cn lu nng v vng

pH ti u (hnh 4), pH hiu qu tt nht vi mui nhm l khong 5,5 -T- 7,0.

C th dng phn kp KA1(S04)2.12H20 thay phn nhm, mi quy lut tng t

phn nhm song gi t hn nhiu. Khng dng NH4A1(S4)2 trong x l nc cp v gy

nhim amni.

cc nc cng nghip ngi ta c i hi rt cao v trong ca nc lc. Neu o

bng c k th c nc lc phi nh hn hoc bng 0,1 n 3 NTU (AWWA Task

Group 225 M).

Thm ch khi nc c c rt thp 0,1 NT vn c rt nhiu cn khng th thy

bng mt thng. N c th l nhng ht cn rt tinh cha b tc ng ca cht keo t hoc

bn thn nhng mnh v nh ca cc bng kt ta cht keo t khng th lng - lc c.

Ngi ta xc nh c ng vi ss = 0,1 mg/L c th c ti 200 triu ht c 0,1 Lim l cc

mnh ca bng cn Al(OH)3 c p = 1,01. Tuy nhin y l i lng khng nguy him v ch

ng vi hm lng Al3+ bng

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Vit Nam phn nhm c sn xut cc nh my ho cht Vit Tr, Tn Bnh ...

v c hm lng nhm quy v AI2O3 l khong 14% (i vi ho cht tinh khit l 15,1%).Do ngm nc rt thay i nn cn nh lng hm lng nhm khi s dng.

II.3.2 Mui st Fe2(S04)s.H20 hoc FeCl3.nH20 (n = 1 +6)

Mui st cha ph bin Vit Nam nhng rt ph bin cc nc cng nghip. Ho

hc ca mui st tng t nh mui nhm ngha l khi thu phn s to axit, v vy cn

kim gi pH khng i.

Fe2(S04)3 + 3Ca(HC03)2 -> 2Fe(OH)3 + 3CaS04 + 6CO2 (8)

So vi phn nhm mui st c u th l vng pH ti u rng hn, t 5 n 9, bngcn bn hn v nng hn nn lng tt hn, lng st d thp hn.

II. 3.3 Cc polime nhm, st

S hnh thnh cc ht polyme nhm trong dung dch c lm r t nhng nm

1980. y l c s khoa hc sn xut PAC cng nh ng dng PAC.

Ho hc ca qu trnh keo t:

Thng thng khi keo t chng ta hay dng mui clorua hoc sulpht ca Al(III)

hoc Fe(III). Khi , do phn li v thu phn ta c cc ht trong nc: Al3+

, Al(OH)2+

,Al(OH)2+, Al(OH) phn t v Al(OH)4', ba ht polime: Al2(OH)24+, Al3(OH)45+ v

A11304(0H)247+ v Al(OH)3 rn. Trong A11304(0H)247+ gi tt l Ali3 l tc nhn gy keo t

chnh v tt nht.

Vi Fe(III) ta c cc ht: Fe3+, Fe(OH)2+, Fe(OH)2+, Fe(OH) phn t v Fe(OH)4',

polime: Fe2(OH)24+, Fe3(OH)45+ v Fe(OH)3 rn. Cc dng polime Fex(OH)y(3x-y)+ hoc

FexOy(OH)x+r(2x_2y'r)+

Trong cng ngh x l nc thng thng, nht l nc t nhin vi pH xung quanh7 qu trnh thu phn nh nu xy ra rt nhanh, tnh bng micro giy, khi ht Al 3+

nhanh chng chuyn thnh cc ht polime ri hyroxit nhm trong thi gian nh hn giy

m khng kp thc hin chc nng ca cht keo t l trung ho in tch tri du ca cc

ht cn l lng cn x l lm chng keo t.

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Khi s dng PAC qu trnh ho tan s to cc ht polime AI 13, vi in tch vt

tri (7+), cc ht polime ny trung ho in tch ht keo v gy keo t rt mnh, ngoi ra tc thu phn ca chng cng chm hn Al3+ rt nhiu, iu ny tng thi gian tn ti ca

chng trong nc ngha l tng kh nng tc dng ca chng ln cc ht keo cn x l, gim

thiu chi ph ho cht. Ngoi ra, vng pH hot ng ca PAC cng ln gp hn 2 ln so vi

phn, iu ny lm cho vic keo t bng PAC d p dng hn. Hn na, do kch thc ht

polime ln hn nhiu so vi Al 3+ (c 2 nm so vi nh hn 0,1 nm) nn bng cn hnh thnh

cng to v chc hn, thun li cho qu trnh lng tip theo.

II.3.4 Cht tr keo t - to bngC bn nhm cht tr keo t: cc cht hiu chnh pH, dung dch axit silixic hot tnh,

bt t st v polime.

1. Cc cht hiu chnh pH

Nh nu qu trnh keo t thng km theo s tiu th K, nu kim ca nc

ngun thp gy gim pH. Cht hiu chnh pH thng l vi. Vi sng l CaO, khi dng phi

ti ngha l ho vo nc to Ca(OH) 2. Do tan ca vi thp (trong khong 2CM-30

c, tan ca Ca(OH)2 bng 1,65-5-1,53 g/L) vi thng c s dng di dng huynph Ca(OH)2.

S dng vi ngoi kh nng n nh pH tng hiu qu keo t bng phn cn tng

cng x l cc axit humic, cng.

2. Axit silixic hot tnh (AS)

AS thng c iu ch ti ch bng cch trung ho thu tinh lng Na2Si3 bng

axit nhng iu kin c th. Axit silixic to thnh thc cht l polime v c, mang in

tch m. Khi vo nc cc phn t AS m in nhanh chng ht cc ht bng cn nh mang

in dng ca kt ta hyroxit nhm hoc st to bng ln.

3. Bt t st

Bt st tc dng tng t AS do chng mang in tch m, hn na chng cn c kh

nng, tuy yu, hp ph mt phn cc cht hu c gy mu, bng cn to

17


18/51

thnh cng nng hn. Cng nh AS, bt st liu lng thch hp dng tt khi phi hp vi

phn nhm v mui st.4. Cc cht to bng hu CO - cao phn t

y l nhm cht c tc dng to bng tt nht. Cc polyme dng lm cht to bng

cho qu trnh x l nc phi p ng cc yu cu sau:

- Tan tt trong nc;

- Khng c;

- C kh nng to bng tt nh i lc cao i vi ht keo v bng cn nh trong

nc x l.Ty vo bn cht nhm chc m ngi ta phn ra lm 3 loi:- Loi khng phn ly (nhm chc amid -CONH2).

- Loi to anion (nhm chc axit -COCT)

- Loi to cation (nhm chc amin bc cao =N1 cr)

To bng hu c bao gm cc hp cht t nhin v cc hp cht tng hp.

Cc hp cht t nhin ch yu c cu trc ung, bao gm:

- gm thc vt

- pectin

- xantan (sn phm ln men ym kh ng ma) ...

Cc hp cht tng hp:

Thng chng l cc hp cht cao phn t, c phn t khi mc 104-105. Chng c

th c s dng ring, nhng thng phi hp vi cht keo t v c. Khi s dng chng

liu lng mui v c gim mnh, bn sinh ra s t hn nhiu so vi s dng keo t v c.

Thng gp bn nhm hp cht:

- Sn phm trng ngng melaminphoocmaldehit:

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19/51

CH2NH N NHCH2

NV" N

NH2n

- sn phm trng ngng ca epiclohyrin v dimetylamin:

- poly(dialyl-dimetyl amni clorua):

CH2CH2

N Cl0

/ \TCH3CH3

- Nhm ph bin nht hin nay l cc polyacrylamit (PAA) tan trong nc, hin

nhp ngoi. Liu dng trong x l nc cp ca chng l 5-S-15 phn triu. Tt nht l dng

PAA kt hp vi phn. Khi dng PAA, dung dch PAA thng c a vo sau khi khuy

trn phn khong 1+2 pht. im khc c bn ca qu trnh to bng l tc to bng ln

(trong vng 2 pht so vi phn cn 20 pht) v kch thc bng cn cng nh bn bng

cn hn hn bng cn phn.

PAA cn c s dng ph bin trong x l nc thi, x l bn v nhiu ngnh cng

nghip vi liu dng ln ti 5-50 g/m3.

Nhc im chnh ca PAA l sn phm nhp, t v phi la chn chng loi PAA

v liu lng cho ph hp vi tng loi nc bng thc nghim.

n

n

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Cng thc cu to ca cc loi PAA ph bin cho hnh 7.

Loi khng phn li (non-ionic):

CH-

c=o

Loi anion (anionic):

-ICH2CH-

c=

CH2CH

c=00

m

Loi caton (cationic): R

~CJ2 CH

C=0nh2

:H2c

c=0 cf_(ch2VVCT3

' '^ch3

m

Hnh 2.5- Cng thc cu to ca cc loi PAA x l nc

II.4 ccYUU TU UNH HUUNG DDA^ QU TRNH KEO r Ngoi yu tbn cht ca cht keo t (nht l gi tr v du in tch) v tp

cht c trong nc cc yu t sau l quan trng nht.

11.4.1 YutpH

Mi cht keo t, d l mui nhm hay st, u c khong pH ti u cho s hnh

thnh kt ta hyroxit tng ng. Thp hn gi tr ny cc bng Me(OH )3 to thnh s b

ho tan bi axit. Cao hn gi tr ny s to thnh cc mui baz kh kt

i vi cc cht in li polime pH s nh hng n kh nng phn li ca cc nhm

chc, gy tng hoc gim mt cc nhm chc hot ng lm thay i kh nng tng tc

phn t polime - ht keo.

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11.4.2 YOu t hu cKhi x l nc bng cht keo t cn lu hin tng lm bn keo bi cc

cht b hp ph hu c. Cc cht hu c t nhin (v d, axit humic - AH) ph bin trong

nc c tnh lm bn keo r rt nh kh nng to phc vi Fe 2/3+, ngoi ra lp mng cht

hp ph hu c vy quanh ht keo ngn cn tng tc gia cc ht keo vi cc tc nhn keo

t ta ch ng a vo, gim r rt tc dng lm trong nc ca cht keo t. v phnmnh, lng HA trong keo t c th nh gi qua pH,bng 2.2 cho ta thy t l HA thng

gp trong keo t ph thuc vo pH nh th no.

y chnh l trng hp ta gp khi nc c mu (do cht hu c tan trong nc).

Cch x l thng l nng pH bng vi gim t l HA/t hoc tin x l bng cc cht

xy ho nh clo, zn ph hy mt phn cht hu c trc khi keo

Bng 2.2 -S ph thuc t l HA/t (phn HA/100 phn t) vo pH mi trung nc

Ph HA/t pH HA/t

3,85 9,60 6,95 6,28

5,0 8,18 7,25 5,37

5,1 7,26 8,50 2,05

II.5 UNG DUNG

Qu trnh keo t - to bng thng p dng trc lng hoc lc :

- Lm trong nc, x l mt phn mu trc khi lc (x l nc cp): cc cht keo

t trong x l nc cp thng l phn nhm, gn y xut hin Poly- Aluminium-Chloride

(PAC) l mui nhm dng polime, cc cht tr keo t PAA. Mui nhm thng s dng

mc trn 10 mg/L, PAC s dng mc bng 1/2--1/4 mui nhm, PAA s dng mc 0,2-

-0,5 ppm.

- Gim hm lng ss trc khi vo x l sinh hc (x l nc thi)

- Tng cng kh nng lng ca b lng cp 2 trong x l nc thi

- Lc trc tip nu ss khng qu caoTrong mt s trng hp cc cht keo t liu cao c th p dng x l mu

trong nc thi cng nghip, v d nc thi dt nhm, nc thi giy.

Qu trnh keo t c thc hin bng cch trn nc vi cht keo t trong cc thit

b khuy trn nhanh, sau nc c a vo b to bng vi s khuy trn nh nhng

nhm tng cng tip xc ht - ht lm cho bng pht trin kch thc, trnh v bng. Tip

theo nc vo b lng thc hin qu trnh tch rn/lng.

S keo t - to bng c coi l hiu qu nu bng cn to ra d dng nhn thybng mt thng (kch thc gn 1 mm tr ln), khi nc s lng trong nhanh trong ng

quan st trong vng 10-15 pht yn.

Ngoi nhng ng dng trong x l nc cht keo t to bng cn p dng nhiu

trong vic x l bn nhm tng kh nng tch nc khi bn, p dng trong cng nghip

giy nhm iu chnh c trng lu bin ca hn hp bt...

15.7.1 Khuy trn

Khuy trn l qu trnh m hu ht cc h phn ng u cn thc hin. Mc chchnh ca n l to tip xc ti a gia cc phn t, ion, cc thnh phn phn ng, gim

thiu cn tr gy ra do khuch tn chm.

i vi h lng hoc rn(t)/lng(nhiu) ta dng thut ng khuy (hoc c khuy

trn), i vi h rn/rn hoc rn(nhiu)/lng(t) ta thng dng thut ngtrn.

Ngoi vic to iu kin cho phn ng xy ra nhanh hn, gim thiu tc ng ca

yu t khuch tn, khuy trn cn c cc tc dng quan trng khc nh:

- Lm u hn hp (trong cng ngh vt liu bt)- Lm v cc ht, git ln (trong cng ngh ho hc).

- Tng cng tc truyn nhit, gim nh hin tng tng gim nhit cc b.

Trong qu trnh keo t - to bng khuy trn nhm:

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- Phn b nhanh, u cht keo t, to bng trong ton th tch nc cn x

- Tng hiu qu x l, suy ra gim chi ph trong qu trnh keo t.

- Tng tip xc ht - ht nh, thc y to bng.

- Lm l lng cc ht rn trong lng (trong h x l vi sinh) hoc kh

Khi cn phn bit: i vi qu trnh phn ng, cn phn b u ho cht nhanh

ti a nn ta s dng qu trnh khuy nhanh; i vi qu trnh to bng hyroxit kim loi

khuy nhanh s lm v bng cn, khi ta cn khuy nh nhng. Hiu qu qu trnh khuy

ph thuc vo cng sut khuy.

Tnh cng sut khuy

nh lng qu trnh khuy ta dng i lng graen vn tc G. Trong gii hn

nht nh, i lng G cng ln s khuy cng tin ti l tng. G chnh l hm ca cng

sut khuy p cho mt n v th tch cn khuy:

p = Cng sut tuyn vo cht lng, w

V = Th tch cn khuy, m3

|LI = nht ng hc cht lng, Pa.s

Q = lu lng, m3/s

V = th tch cn khuy, m3to = thi

gian lu nc, s

Tu mi nhim v c th ta chn gi tr G thch hp. Hiu qu khuy (tng s va

chm ht - ht) o bng Gto, trong to l thi gian lu nc trong vng khuy.

l.

(9)

hoc h qu:

Trong : G = graien vn tc, s"1

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Bng 2.3, 2.4 cho ta cc d liu kinh nghim tnh cc i lng G, Gt 0ng vi mi

qu trnh.Bng 2.3 - Cc gi tr G tnh khuy nhanh

Cc gi tr thi gian lu to

(s)

Gi tr G la chn (s )

0,5 (trn trong ng) 3500

10+20 1000

20-30 900

30-40 800

Lu hn na 700

Bng 2. 4- Cc gi tr Gto tnh b to bng

Loi bn G(s~1) Gio

Nc c ss thp, keo t x l c mu 20+70 60000-200000

Nc c ss cao, keo t x l ss 50+150 90000+180000

Lm mm, 10% ss 130-200 200000-250000Lm mm, 39% ss 150+300 390000-400000

------------?------------------Khuy nhanh

y l qu trnh nh hng mnh n hiu qu s dng cht keo t. Nh nu,

qu trnh thu phn xy ra trong micro giy (ti liu ni l 0,ls), nh vy khuy cng nhanh

cng tt v kha cnh p ng yu cu phn ng. Ngc li nu ion Al 3+ hnh thnh cha kp

tip xc ht keo thc hin chc nng trung ho in tch, gy keo t, n thu phn to

Al(OH)3, khi n ch c th tc ng nh mt cht to bng.

Phn loi cc phng php khuy nhanh:

- Khuy c kh bng my khuy (tt nht)

- Khuy bng kh nn.

24

- Khuy bng cch bm cht lng tun hon

- Khuy tnh: tn dng cc c cu dng chy, v d: khuy trong ng trn; khuy

kiu rnh thu - dn (rnh Parshall); thc nc; vch c l, vch o chiu

Bn khuy trn c hc

Nc vo____

ng c

Nc ra

D- -Q

o- -

D- -0

Hnh 2.6 - Bn khuy nhanh c kh

Bn khuy nhanh thng c thi gian lu thu lc c 10 -- 30 s, G mc 600 -s-

1000 s"1, th tch gii hn 8 m3. Bn khuy thng c hnh tr, tng hiu qu khuy

thng b tr thm 2 V 4 vch chn nh dc thnh b tng hiu qu khuy, i khi c

vch ngang chng to xoy.

My khuy gm: ng c in, hp s gim tc, trc khuy, cnh khuy.

Cnh khuy thng dng loi turbin hoc mi cho (xem h. 9). Ho cht phi cho

vo vng ngay di cnh khuy, ni c khuy mnh nht.

Mi cho nghing chn vt tuc bin

Hnh 2. 7- Mt s dng cnh khuy

Mt s quy tc kinh nghim:

- su mc nc: 0,5 + 1,1 ln ng knh bn.- ng knh cnh khuy: 0,3 -- 0,5 ln ng knh bn, thng < lm.

- Tm chn dc rng ~ 0,1 ln ng knh bn.

- Neu mc nc = 1,1 1,6 ln ng knh bn cn lp 2 tng cnh khuy, khi

khong cch gia hai cnh khuy (theo trc khuy) gp hai ln ng knh cnh khuy.

- Hai b cnh khuy ng trc gy ra cng sut khuy 1,9 ln so vi mt b nu

dng mt mt

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24/51

9 r

Bng2. 5- Cc gi KT chn cnh khuy

Loi cnh khuy KT

Chn vt mt tng, 3 cnh khuy 0,32

Chn vt hai, 3 cnh khuy 1,00

Tuc bin, 6 cnh phng, c chn 6,30

Tuc bin, 6 cnh cong 4,80

Tuc bin qut, 6 cnh nghing 45 1,65

Tuc bin vng, 6 cnh cong 1,08

Tuc bin vng, vi stator, khng vch chn 1,12

7.2 H to bng

H to bng nh hng n kch thc bng hnh thnh, do nh hng n kh

nng tch R/L trong h tip theo.

Mc ch qu trnh to bng l khuy va to iu kin tip xc tt nht gia

cc ht cn nh vi nhau, to iu kin cho chng ht nhau, to bng ln hn ti mc ckh nng lng d dng, nhng mt khc khng c khuy qu mnh lm v bng cn

mi hnh thnh, nh vy i lng G phi nh v hp (bng 4).

Do cht lng nc vo thay i nn cn thit k sao cho c th thay i G c 2 --

3 ln m khng qu thay i kt cu b to bng. Bng cng ln, mt bng cng cao ta

cng cn G ln (9). i vi cn ca qu trnh lm mm bng vi

- sa, t khi nng hn cn keo t nn G cao nht. Khi mt ss tng, gi tr G cng

tng tng ng.Cnh khuy thng dng l loi cnh hng tm do cnh khuy loi ny to G c

gi tr u nht trong ton th tch.

C th khuy to bng bng cc cnh khuy dng tm phng, h bn nhiu vch

ngn o chiu.

27

Cnh khu

Hnh 2.8-B to bng vi cnh khuy dng tm phng

cht Vch c nhKhuy nhanh/' H|Png dng

Bn/b to bng tt nht l hnh ch nht, chia 3 vng. i lng G phn chia sao

cho gim dn t u vo ti u ra (h 2.10). G ly theobng 2.5.

Mt s quy tc kinh nghim:- Cnh khuy mi cho c ng knh=0,2 -- 0,5 b rng b, ti a= 3m.

- Tnh cng sut khuy dng biu thc Rushton:

(")3(P,)V (!())

3

p = Cng sut, w

KT = Hng s cnh khuy

n = Tc quay ca cnh khuy, v/s

Di = ng knh cnh khuy, m

p = T khi nc, kg/m3

g = Gia tc trng trng, 9,8 m/s2

Trong cc b khng c vch ngn p thc t ch c th bng 1/6 p tnh theo pt.

(10) . Cc gi tr KT chn theobng 5.

Mt kiu b to bng khc, kh n gin v hiu qu l b to bng kiu Aabama

(hnh 9). y thc cht l mt thit b phn ng khuy trn bng thu lc, dng nc c

o chiu nhiu ln nh h thng ng hng dng. H thng ng o chiu dng nc c

th c thay bng h vch ngn vi cng chc nng, khi ta gi l thit b phn ng vi

vch ngn o chiu.

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thit b phn ng vi vch ngn o chiu.

Hnh 2 9-B to bng kiu Alabama

III .LUngIII.1. KHI NIUM LUNG vu BU LUNG Lng l qu trnh tch

cn l lng khi nc nh tc ng ca trng lc, n

cn c gi lsa lng.

Cc cht l lng y c th l ss t nhin, cc bng cn sau keo t - tobng, k c bng vi khun sau x l sinh hc.

Cng c thc hin qu trnh lng l b lng. Be lng c th c ch to

di dng thit b bng thp, compozit hoc xy dng bng beton, gch. Cc hnh

dng ph bin nht l hnh tr vung hoc trn, hnh hp ch nht.

Mt b lng cn c bn vng (hnh 3.1) [1]:

1. Vng nhn v phn phi nc. y l u vo b

2. Vng lng

3. Vng cha bn lng

4. Vng thu nc lng

Vng nhn - phn phi nc vo

Nc th I

Vng thu nc lngMng thu nc

29 1 Nc lng -

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Hnh 3.1- M hnh b lng v bn vng c bn

Vng nhn nc c chc nng phn phi nc u sao cho tn dng c ti a

khng gian vng lng, ngoi ra phi gim vn tc nc vo vng lng ti vn tc thit k

gii hn cho vng lng Vo c gi l tc gii hn hay ti b mt (n v: m3/m2.ngy).

Nh vy cu to ca vng nhn nc phi m bo c cc yu cu k trn. Trong thc t

thit k vng nhn nc khng c coi trng nn hiu qu b lng km hn so vi khi

tch b ti 25%

e thc hin iu ny vng thu nc thng c vch hng dng (c th kim phn

phi (hnh 3.1) Nc cng c th c phn phi v gim tc tt thng qua h ng nhiu

u ra.

Vng thu nc lngc chc nng thu nc lng bt cn, chuyn ti i sang cng

on tip theo. thc hin iu ny cn b tr cc mng thu. vn tc nc vo mng

khng qu cao, iu dn ti to cc dng chy mnh gn mng thu cun theo cn ang lng

ngi ta a ra thng s ti mng thu (n v: m 3/m.ngy). R rng l cn cng nng cng

kh b cun tri nn chiu di mng thu cng ngn. Bng 3.1 cho ta s ph thuc tiu chun

thit k i vi mng thu cho cc loi bng cn khc nhau.

r

Bng 3.1- Cc thng s ti mng thu thng gp [1]

Loi bng cn Ti mng thu, m37m. ngy

Bng nh phn vi nc t c 143-179

Bng nh phn vi nc c 179-268

Bng cn x l cng 268-322

30

Vng cha bn phi thun li cho vic thu gom, x bn v v sinh b thng k.

Thng phi c h gom bn b tr gn ca nhn nc. Neu b gom bn th cng th y b

phi c dc nht nh v pha h gom. dc t hai bn v tm b t nht phi l 10%,

t u thu nc lng n u nhn nc vo t nht l 5%. Neu gom bn bng cn gt bn

c kh th dc t l 1%.

su h gom bn t nht l 0,3 mt. Vi b lng thit k vn hnh tt, vi nc keo

t - to bng tt th c ti 75% bn lng c lng trong khong 1/5 u tin ca ng i

ca nc, v vy vng lng bn tnh t khong 2 mt cch vng nhn nc vo.

III.2 L THUYUT TNH TUCDLUNG HUT - PHUUNG TRNH STOKEBn cht caqu trnh lng c th xem xt trn c s hin lng lng ca ht

cn c kch thc d, t khi pp trong mi trng cht lng, v d nc, c nht

ng lc hc \x.

e xy dng m hnh tnh tc lng ht ta chp nhn mt s iu kin sau: l Cc

ht cn c hnh dng v kch thc khng i, khng tng tc, khng co cm vi nhau,

ngha l mi ht c th coi l ht c lp vi nhau, s sa lng ca ht ny khng nh hng

n ht kia.2. Bn c kch thc rt ln so vi ht, ngha l b qua yu t tng tc thnh bnh.

3 Cht lng c nht nht nh.

4. Cht lng khng chuyn ng

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FD FbFn = FD+Fb

Tng hp lc

Fg

Hnh 3.2- Lc tc ng ln ht khi sa lng trong mi trng lngKhi ht ri trong

nc (hoc bt k cht lng no khc) n chu ba lc tc ng (hnh 3.2) [1].

-Lc trng trngFg c phng ko ht xung y bnh,

- Lc cn ca cht lng gy ra do lc ni ArchimetFb,

-Lc ma stvi cht lng FD lm chm chuyn ng ca ht.Tng hp cc lc cn ta c (h. 3.2) FH=Fb + FD .

Khi Fg > Fn ta s c ht chuyn ng nhanh dn vi gia tc a xc nh theo nh lut

Niutn (F = ma).

Phng trnh cn bng lc:m = Fg+Fb+FD

trong :

m = khi lng ht, a =

gia tc sa lng, mi tn l

k hiu vector.

B qua du vector, lu hng tc ng ca cc lc, vit phng trnh Niutn cho

ht kho st ta c: ma = Fg-Fb-FD

hay: ma = (Fg - Fb) - FD (3.1)

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Tng (Fg - Fb) c ngha nhc trng trng hiu dng Fgko ht xung. Trong

trng hp lc trng trng hiu dng ln hn lc ma st Fd ht s ri vi gia tc a nh

pt. (3.1).

Nh vy vn tc ri ca ht s tng theo thi gian chuyn ng ht, iu ny dn ti

FD tng, ti thi im khi (Fg - Fb) = FD th gia tc = 0, khi ht chuyn ng vi vn tc

khng i.

(Fg - Fb) = Fg l lc trng trng hiu dng ko ht xung xc nh bng:

Fg- = (Pp - P)gVp (3.2)

trong :

Fg = lc trng trng hiu dng gy ra s sa lng ca ht,

Pp = t khi ca ht, p = t khi ca nc, g = gia tc trng trng,

= 9,8 m/s2Vp = th tch ht.

Lc ma st c xu th km s sa lng bng:

FD=pCDAPv2 (3.3)

trong :CD = h s ma st gia ht ang ri vi mi trng lng,

V = tc ri ca ht,

Ap = thit din ht vung gc vi hng ri ca ht.

H s ma st CD l mt hm phc tp, v d, i vi ht ri trong dng chy tng,

Stoke a ra cng thc lc ma st, phn trong ngoc l h s ma st CD:Fd = (37|^d)v

(3.3a)

Trong d l ng knh ht; . l nht ng lc hc ca cht lng.

Ket hp cc pt. (3l) n (3.3) ta c:

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Ppvpa = PpVp = (Pp - P)gvp - i pCoApv2 (3.4)dt2

Khi ht sa lng trong mi trng nc di tc dng ca tng lc nu ht chuyn

ng nhanh dn, ng thi cc lc cn tng theo V 2 n khi lc sa lng (lc trng lc hiu

dng) cn bng lc cn (lc ma st) ta c a = 0 hay vn tc bng hng s, nh vy:

(pP-p)gVp=ipCDApV2 (3.5)

T y ta tnh c V, tc lng ca ht:

V=\MPJE (3.6)V CDp p

Trng hp n gin nht, nu ht l hnh cu ng knh d, thay cc gi tr Vp,

Ad bng cc biu thc cha d (Vp = (l/6)7id3; Ap = (1/4) n2); ta c:

(5E3 (3.7)V CD p

Trong thc t i lng Cd - h s ma st khng phi hng s, n tng khi tc

chuyn ng ca cht lng gn ht tng v ph thuc ch so Reynod, Re, ch s khng th

nguyn ni ln ch chy ca cht lng. i vi ht hnh cu ta c:

Re = ^ (3.8)M

Gi tr ca Re ph thuc vo ng vi cc ch chy [1]:

Re < 1: chy tng

Re > 1000: chy ri

1 < R < 1000: vng trung gian

Vi cc ht hnh cu ta c th s dng cc gi tr thc nghim:

Nu Re < 1 ta c CD = 24/Re (3.9)Nu 1 < R < 1000 ta c CD = 24/Re + 3/Re05 + 0,34 (3.10) Nu R>

1000 ta c CD = 0,34 n 0,4 (3ll)

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Ngoi ra CD ph thuc hnh dng ht, yu t quyt nh Ap th hin qua s ph

thuc vo yu t (Ap/Vp): ht cng khc hnh cu (Ap/Vpcng ln) th CD cng ln.

Khi , kt hp pt. (3.7(3.9) ta c phng trnh Stoke cho php tnh tc lng V

ca ht:

EMBED Equation.3

(3.12)

Nh vy ht lng nhanh chnh lch (pp - p) l rt quan trng, iu ny c

ngha l cht ht cng nng ht lng cng nhanh.

Trong thc t cc ht khng hnh cu l tng nh m t, hnh dng ca chng rt

khc hnh cu, kch thc a dng, ta gi l h a phn tn. Chng khng nhng c th

tng tc vi nhau to bng ln (hin tng keo t-to bng, hin tng to bng ca vi

khun trong b lng cp 2) m chng cn tng tc vi chnh mi trng nc, khi

khng th p dng pt. (3.12) V vy, thun li cho vic phn tch qu trnh lng ngi ta

phn ra bn kiu lng tu mc tng tc ht-

III .3 PHN LOM cc KI U LOU LUNG

III.3.1 Lng loi 1

y l trng hp cc ht lng khng c tng tc ht-ht. y l cc trng hp

lng cn t nhin th, cn nng thp, khng c tng tc ht-ht v tng tc ht-nc

c th b qua.

Kiu lng ny hay gp cc h tin x l lng ct, v cc ht th.

III.3.2 Lng loi 2

y l kiu lng ca cc ht c kh nng bm kt vo nhau to bng ln, khi ht

tng dn v kch thc, khi lng dn n tc lng tng. Hin tng lng loi hai hay

gp khi s dng cht keo t - to bng.

III.3.3 Lng loi 3

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Cn gi l lng z?/cn hay lng vng. Khi nng cn tng i cao, khi tng

tc ht-ht lm chm qu trnh lng, c khi ht dng nh cng lng, khi ta s thy r

bin phn cch nc/bn. Hay gp trong cc b lng cp hai ca h x l sinh hc.

.3.4 Lng loi 4

y l trng hp tng tc ht-ht mnh n mc c th hnh thnh cu trc khng

gian ca bm, n xut hin khi nng bn cn cao, s lng xy ra ng ngha vi s nn

bn lm thot nc trong cu trc bn. ng lc ca qu trnh l s tng khi lng lin

tc ca bn nh s b xung bn mi lin tc t lp nc pha trn do sa lng cc kiu 1, 2,

3. Hay gp lp di ca lp bn trong b lng cp 2 (h x l sinh hc), b nn bn///.5cc DUNG BU LUNG cu BUN

Hin nay c rt nhiu dng b lng v vy chng ti ch trnh by cc dng

b lng c bn nht, ph bin nht trong x l nc cp: Be lng ng, b lng ngang v b

lng li tm.

III.5.1. Be lng ng

- Hnh dng, cu to: Hnh tr vung hoc trn. y chp to gc t nht 50 so vi

mt bng. Thng i km vi khoang phn ng i chiu dng nc.- Nguyn tc hot ng: Nc chy theo phng thng ng t di ln trn cn

cc ht cn ri ngc chiu vi chiu chuyn ng ca dng nc t trn xung. Khi x l

nc khng dng cht keo t, cc ht cn c tc ri ln hn tc dng ca dong nc

s lng xung c, cc ht cn c tc ri nh hn hoc bng tc dng ca dng nc

s ch l lng hoc b cun theo dng nc ln pha trn b. Khi s dng nc c dng cht

keo t, trong nc c cha cc ht cn kt dnh. Do ngoi ht cn c tc ri ban u

ln hn tc dng ca dng nc lng xung c v cc ht cn khc cng lng c.Nguyn nhn l do trong qu trnh cc ht cn c tc ri nh hn tc dng ca dng

nc b

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y ln trn, chng kt dnh vi nhau v tng dn kch thc do tc ri ln hn tc

chuyn ng ca dng nc lm cho n lng xung c.

u tin nc chy vo ng trung tm gia b ri i xung di qua b phn hm

lm trit tiu chuyn ng xoy ri vo b lng. Trong b lng ng, nc chuyn ng t

trn xung, cn t trn xung y b. Nc lng c thu vo mng b tr xung quanh

thnh b v c a sang b lc.

- Thng s thit k:

e xy dng cc tiu chun thit k b lng ng (h. 3.3), khi ta c hai khi nim:

tc lng cn Vpv tc dng nc v0.

Nh vy, iu kin lng s l:

Nu chiu cao ct nc l H, vy thi gian nc dng t y ti mng thu t tnh

theo phng trnh:

V th tch vng lng V = HA, trong A l thit din y, phi hp vi pt.

C s tnh b lng ng l phng trnh Stoke (pt. 3.12) ngha l tc dng

nc dng phi nh hn tc lng bn. S b lng ng cho hnh 3.3.

Vp> Vo (3.13)

(3.14)

Mt khc t chnh l thi gian lu nc tnh bng:

(3.15)

Trong : V = th tch nc trong vng lng Q = lu

lng

(3.14) v (315) ta c:

H _ HAv0~ Q

T y rt ra biu thc xc nh v0:

Vo = (pt Hazen)A

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Hnh 3.3 - S b lng ng

Ngi ta thng thit k b lng ng vi din tch mt nc khng qu 100 m 2, c

t l gia ng knh v chiu cao t hn hoc bng 1,5. Trn hnh 3.3 l s b lng ng

y chp ca n c dc t nht l 50 nu ngi ta x l nc bng cht keo t, v 60

trong trng hp x l cng.

tm b lng ng l ng hnh tr ng vai tr bung phn ng. Nc theo ng dn

vo bung phn ng (nu cho ho cht keo t) v theo ng tr i xung, to u ra 4 pha

ri i ln.

Vic thu nc c thc hin nh h mng thu b tr xung quanh gn mp trn b.

Nu din tch mt nc ca b ln hn 12 m 2 th nn b tr thm cc mng thu theo ng

hng tm, nu n ln hn 30 m2 th cn 6^-8 mng thu. Mng thu nc nn c mt trn

hnh rng ca hoc c l 20 -- 30 mm nc qua. Din tch mng thu tnh sao cho tc

nc chy trong mng bng 0,6 -- 0,7 m/s. Cn y b c x nh k nh p sut

thy tnh bng cch m van x y hoc dng bm ht bn.

Tc dng nc trong b lng ng phi nh hn tc lng cn (xc nh bng

thc nghim) v khng ln hn 0,6 mm/s (bng 3.2).

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Bng 3.2 - S ph thuc tc dng nc V (mm/s) trong lng ng vo cht lng nc

th khi x l phn

Loi nc V(mm/s)

Nc mu, CLL < 50 mg/1 0,35 ( 0,45

Nc c, CLL = = 50 (250 0,45 ( 0,50

>250 0,50 ( 0,60

Nc c khng nh phn 0,12(0,15

------------------------------------------7----------------------------- 7------------------------------------------------------------------------------------------------------------------------------

Ghi ch: nu c cht to bng, V tng thm 15 ( 20%

- ng dng: Trm c cng sut khng qu 3000 m3/ngay, khi x l bng cht keo

t. Lng ng hay dng trong cng ngh x l nc cp quy m nh.

3.5.2. B lng ngang

- Hnh dng, cu to: Hnh hp ch nht lm bng gch hoc btng ct thp. T l:

L:H >= 10 dc t nht 0.02 theo chiu dc v 0.05 theo chiu ngang

- Nguyn l hot ng: Nc chuyn ng theo chiu ngang t u b n cui b.

Vi tc nc V u khp mi im trong vng lng v gi s cc ht u cng mt v tr

xut pht (im vo b), khi da vo kch thc ca tng ht m ht c th lng c

hay khng. Xt mt ht c qu o ri (c dng ng thng- xt trng hp l tng) ng

bng chiu di ca y b v c cao bng chiu cao b tng ng vi tc lng ca ht

l Vp khi ht lng c. Nh vy nu cc ht cn c tc lng nh hn Vp s khng

lng c.

- Thng s thit k:

7 r

Hnh 3.4-M hnh b lng ngang

39

1-nc th vo, 2- mng thu nc, 3 - x cn bn

- Cc thng s thit k c bn ca b lng ngang

- Thi gian lu khng t hn 4 gi

- Tc nc c keo t V = 3 -- 13 mm/s. Neu khng s dng cht keo t phi gim

V cn 2 -- 3 mm/s.

- T l L : B > 10

- Chiu cao H = 3,0 -- 5,0 m

- dc theo chiu nc chy ti thiu 0,02; theo phng ngang ti thiu 0,05.

- ng dng: p dng cho trm x l c cng sut 3000m3/ngy.m (nu dng phn),

v cng sut bt k cho trm x l khng dng phn.

III. 5.3 Be lng li tm

- Hnh dng, cu to: Hnh tr trn, y cn, c cn gt thu bn

- Nguyn l hot ng:

Hnh 3.5- B lng ly tm

- Nc vo thung c a theo ng trung tm, t khoang trung tm nc theo cc

tia bn knh chy vo cc mng thu b tr quanh b hnh trn. Be lng ly tm thng c

p dng cho cc ngun nc c hm lng ss cao, nht l trong x l nc thi. thu gombn b c trang b cn gt bn c gii gt st y

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c dn bn v h thu tm b. T y bn c x bng p sut thy tnh hoc bng bm

ht bn (hnh 3.5).

ng knh b lng ly tm thng gp t 5 -- 60 m, su 3 -- 5 m tm v1.5 --3m thnh b. Tc quay ca cn gt bn l 3 -- 3,5 v/h vi ng c y c

1.5 + 2,0 kW

- Thng s thit k: Da trn c s thc nghim

- ng dng: p dng khi lng cn ln IV. Lc

IV.1 KHI NIUM Lc l qu trnh lm sch ncthng qua cc vt liu lc nhm tch cc ht

cn l lng, cc th keo t v c vi sinh vt trong nc, kt qu l sau qu trnh lc

cht lng nc tt hn c v mt l hc, ho hc, sinh hc.

Trong cc h x l nc cp lc l qu trnh quan trng bc nht v n trc

tip quyt nh cht lng nc sn phm, trong x l nc thi lc ch p dng

trong nhng trng hp nht nh. Qu trnh lc c thc hin hai cng on

trong dy chuyn x l: mt l lc th ngay im bt u thu nc, khi qu

trnh lc mang tnh phng nga: chn rc, lc cn th, ru to ... bo v h thng

x l sau v hai cng on p trt, trc kh trng: lc m bo trong

- yu t hng u ca cht lng nc.IV.2 LTHUYUTLUC i vi cc k thut lc nc

thng thng (khng ke lc mng NF v RO)

lc l qu trnh tch cht rn (cn, cn l lng) ra khi nc khi cho nc i qua

mi trng vt liu lc c th gi c cn nhng cho nc i qua. Ket qu l thu

c nc trong, khng cha (hoc cha rt t) cn l lng.

Lc thng thng khng x l c cc tp cht tan nh cc cht hu c gy

mu, mi (tr khi lc bng than hot tnh), cc khong cht ho tan. Tuy nhin nu

tin x l thch hp vn c th x l c mt phn cht hu c tan (v d x l

mt phn cht mu bng phn) hoc ton b tp cht (v d: Fe dng st (II) ho

tan sau lm thong, xy ho tt tr thnh kt ta st (III) lc c).41


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Vi s xut hin ca k thut lc mng NF v RO, ngy nay k thut lc cho php

tch c cc cht ho tan quy m phn t, ion.

Trong dy chuyn x l nc cp thng thng, cng on lc ng vai tr quyt

nh n cht lng sn phm v thng ng p trt trc cng on clo ho st trng-

bo qun trc khi nc vo b cha bm vo mng.

i vi cc k thut lc nc thng thng (khng k lc mng NF v RO) lc l qu

trnh tch cht rn (cn, cn l lng) ra khi nc khi cho nc i qua mi trng vt liu

lc c th gi c cn nhng cho nc i qua. Ket qu l thu c nc trong, khng cha

(hoc cha rt t) cn l lng.

Lc thng thng khng x l c cc tp cht tan nh cc cht hu c gy mu,

mi (tr khi lc bng than hot tnh), cc khong cht ho tan. Tuy nhin nu tin x l

thch hp vn c th x l c mt phn cht hu c tan (v d x l mt phn cht mu

bng phn) hoc ton b tp cht (v d: Fe dng st

(II) ho tan sau lm thong, xy ha tt tr thnh kt ta st (III) lc c).

Vi s xut hin ca k thut lc mng NF v RO, ngy nay k thut lc cho php

tch c cc cht ho tan quy m phn t, ion.

Trong dy chuyn x l nc cp thng thng, cng on lc ng vai tr quyt

nh n cht lng sn phm v thng ng trc cng on clo ha st trng-bo

qun trc khi nc vo b cha bm vo mng.IV.3 cc CU CHULUC vu cc HUN TUUNG LN QUAN

Ty bn cht ca cn cn lc, tu k thut v vt liu lc p dng c th gp

cc c ch lc v hin tng sau: lu gi, bm dnh v hin tng nh thng...

Cc c ch lu gi

C ch lu gi c th hiu l c ch lc thun tu vt l c ghi nhn trong

trng hp lc qua li lc, mng lc c kch thc l nh. Trong trng hp ny lp

lc hot ng theo nguyn l ci ry bt: ht cn nh i qua, ht ln b lu gi li. Trong

thc t, ht nh hn ng knh l trng cng c th b lu gi

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li nu ng thi nhiu ht nh cng qua mt l trng, hoc ht cn lc b tng kch thc

do nhiu nguyn nhn khc nhau.

Trong trng hp ny, cc c ch sau c th ln lt hoc ng thi xut

hin: Nhiu ht nh chen nhau cng qua khe trng nn b kt li

Ht nh trong khi theo dng chy qua l trng b c xt vo lp vt liu lc

rn v b gi li do lc b mt (hp ph)

Do gi tc trng trng, ht cn lng trn b mt vt liu lc khu vc khng

c l trng...

Nhng c ch ny xut hin trong c k thut lc mng v k thut lc bng lp vt

liu lc dng ht.

C ch bm dnh

Khi tc dng chy khng ln, cc lc b mt c th gy ra s bm dnh cc ht

cn trn b mt vt liu lc. Bn cht cc lc b mt kh phc tp, ph bin l lc ht tnh

in v lc Van dec Val (Van der Waals).

Hin tng nh thngTrong qu trnh lc qua lp vt liu lc ht, do cc c ch nu trn nn khe trng

gia cc ht vt liu lc b lp y dn bi cc ht cn b lu gi hoc bm dnh. Nh vy

thit din chy thc t b thu hp dn, tc dng chy qua khe s tng v ko theo cc ht

cn nh vo su trong lp vt liu lc ht, thm ch ht cn b ko theo nc lc. Trng

hp ny nc lc gim cht lng, ta ni lp lc b nh thng.

Hin tng tc v s phc hi lp vt liu lc

Hin tng tc thit b lc do cn bt dn cc khe, l trng m nc c th chyqua theo cc c ch nu. Trong trng hp ny vn c th tip tc lc bng cch tng p

sut. V d: nu lc trng lc nh i vi b ct ta c th mc nc trn lp vt liu lc

dng ti mc vi mt. i vi cc thit b lc p lc vi lp vt liu lc l ct ngi ta c

th nng p lc ti vi ba atm.

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Thng thng, khi thit k thit b lc ngi ta chp nhn mt mc tc nht

nh. vt qua hin tng ny ngi ta tng mc nc hoc mc p p vo lp vt liu

lc gi tc lc khng i.

Khi tn tht p vt qu mc nh (do s tch lu lp bn cn) cn phc hi

li lp vt liu lc v trng thi ban u bng cch ra sch lp vt liu lc khi bn cn, ta

gi l ra lc. Cch ra ph thuc vo loi vt liu v k thut lc p dng.

Ra lc: Bng k thut Ra ngc l ph bin nht v l k thut duy nht i vi

cc thit b lc dng lp vt liu dng ht. Mi trng ra thng l nc sch v cc

trm ln l hn hp kh - nc. i vi cc loi mng lc nh mng lc micro, nano ... sau

ra ngc thng phi x l ho cht b xung.

Ra ngc c thc hin theo chiu ngc li nh sau: ng van thu nc sch,

bm nc sch hoc hn hp kh - nc vi cng rt cao vo y b qua h phn phi

u, nc ra cng cao s lm nng cc ht vt liu lc ln, lp ht si ln , c vo

nhau ra sch bn bm trn b mt, nc bn ra c thu gom qua cc mng phn

phi vo ti cha bn, qua van x ra ngoi. Qu trnh kt thc khi nc ra tr nn trong,

khng cha bn.

kim sot hot ng ca mt h lc ta cn theo di mt trong hai thng s hoc c

hai, l tn tht p c khi lc v c ca nc sn phm.IV.4 PHN LOUI

K thut lc ct thng c phn loi theo tc lc, theo ng lc ca qu trnh

lc, theo chiu ca dng chy, theo s loi vt liu lc.

v mi trng vt liu lc c hai nhm chnh:

Nhm vt liu lc dng ht, mi trng lc l lp vt liu lc dyNhm vt liu dng mng, mi trng lc c dy khng ng k.

Theo tc lc ta c:

Lc nhanh: khi tc lc khong ln hn 5 m/h

Lc chm: khi tc lc bng 0,1 4- 0,3 m/h

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Theo ng lc ca qu trnh lc

nc qua c lp ct dy n cn c th nng nht nh, th nng ny c th do

bn thn trng lng ct nc hoc do bm nn, nh vy ta c:

Lc t chy hay c trng lc: nc chy nh trng lcLc p lc: nuc chy nh

bm nc to p Theo loi vt liu lc:

Lc mt lp: ch dng mt loi vt liu lc

Lc a lp: dng hai loi vt liu lc khc nhau ve cht tr ln

Phn loi theo chiu dng chy ta c:

Lc xui', nc chy t trn xung, thu nc lc y

Lc ngc: nc chy t di ln, thu nc lc trn ming b

Theo c th ca k thut lc v cch hnh thnh mng lc th cp:

Lc tip xc;

Lc ni;

Lc diatomit.

IV.5. CC KU THUUTLUC PHU BIUN TRONG xu L NUUC CUP IV. 5.1

Lc nhanhIV.5.1.1 Gii thiu chung

Trong qu trnh lc nhanh, nc cn x l i qua lp ht c kch thc trung bnh-

ln,vn tc cao. Ngi ta chia b dy lp vt liu lc thnh nhiu lp mng vi kch thc

khc nhau, ban u a s cn bn trong nc tip xc vi b mt trn cng ca lp vt liu,

theo thi gian b dy ca lp mng cn tng dn, b lin kt ca lp mng v vt liu lc

yu i n lc lc ny b ph v th mt phn cn bn b cun su hn xung cc lp ht lc

bn di v lu dn th cn phi thay lp vt liu khc.Vn tc lc nhanh thng thng l 1,5.10 '3 m/s. Nc a qua lp vt liu lc t trn

xung hoc t di ln, s dng dng chy t trn xung c u im l to c ng lc

cho qu trnh nh chnh lch p sut trc v sau khi qua lp vt

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liu lc nh p lc trng trng. Nhc im ca phng php ny l cn p lc mnh ca

dng nc t di ln khi ra lc, cc ht nh b y ln trn, cc ht to gi li pha di,

khi nc cn lc tip xc vi ht b trc th d b tc mao qun lc.

IV.5.1.2 Cu to b lc

Gm cc thnh phn: ng thu nc bn, ngn trung gian, mng trn, vt liu lc,

ngn thu nc sch, ng thu nc sch.

- Vt liu lc: thng dng l ct t nhin, ct thch anh nghin, hoa

nghin..Tiu chun la chn vt liu lc:

+/ bo m thnh phn ht theo yu cu phn loi +/ bo m ng u v kch

thc ht +/ bn c hc cao +/ bn ho hc m bo

IV.5.1.3 Nguyn l hot ng

S nguyn l b lc trng lc vi lp vt liu lc dng ht

1- van chnh lu lng nc vo ; 2- van x nc bn ra lc; 3- van chn khi x ra

hoc thu nc v m khi x lc u v x kit; 4- van m khi thu nc sch; 5- van ni nc

ra lc hoc ng do tn tht p AP (nu c), hoc chng e kh.

Nc th (t ngun hoc t b lng loi bt ss, theo TCN 33-85, ss khi vo blc nhanh phi khng ln hn 10 mg/L) theo ng dn vo b qua ngn

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trung gian (i khi gi l ti). Trn ng i c van (1) kim sot lu lng nc vo.

Ngn trung gian c chc nng nhn v phn phi nc vo u khp b mt b lc thng

qua cc mng trn (khng v trn h. 9.3). Nc lc i t trn xung, qua lp vt liu lc dy

khong mt mt, cn bn c gi li ph trn v trong lp ct, nc trong i vo h thu

gom, theo ng dn qua van (4) vo b cha nc sch. Lc mi lc nc ra hi c s c

x b (gi lx lc u) qua ng van (3). Khi b tc hoc b nh thngphi ra lc.

IV. 5.2 Lc chm

IV.5.2.1 Gii thiu

Lc chm p dng nhiu cho x l nc ung v nc cp, vn tc chy rt thp:

0.03.10"3-0,15.10"3 m/s do mi chu k lc chm thng ko di n vi thng hoc lu

hn, lc chm.v vy bn cnh kh nng tch cn l lng nh nguyn l lc nhanh m khng

cn ho cht keo t, lc chm c kh nng lm trong nc tt hn nhiu nh qu trnh lc

sinh hc. Lc chm rt thch hp khu vc nng thn vi iu kin vn hnh, bo dng

ng phng php. Neu p dng quy m ln cng s cho kt qu rt tt v v mt cht

lng nc.

Qu trnh lc bt u t lp nc trn lp vt liu lc n su vo trong lp vt liu

lc, quan trng nht l cc qu trnh sinh hcbt u t lp mng lc th cp c hnh

thnh t cn v vi sinh vt tch lu trong hai-ba tun u tin trn mt ct. y l im khc

bit c bn gia lc chm v lc nhanh. Nh lp mng lc ny v cc qu trnh vi sinh m t

sau y nc lc chm c cht lng cao khng nhng v trong (do lc tt cn l lng)

nh lp ct mn m cn sch mt phn cht hu c v c th loi ti 95-99% v tng vi

khun v 20-40% v xy ho

/F5.2.2 Cu to b lc chm

H thng lc chm gm 3 khi chnh (nh hnh v)

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1 H cp nc th;

2. B lc gm hai b phn:

Lp vt liu lc v lp m;

H thu nc;

3. Be cha nc sch

Do tc lc chm, trong h khng nht thit phi quan tm qu mc n h phn

phi nc vo. Ngoi ra cn c h thng van iu chnh lu lng, x kit .

im khc c bn ca h lc chm so vi lc nhanh l lp ct lc. Ct lc chm nh

hn nhiu so vi ct lc nhanh, kch thc ct lc ch xung quanh 0,3 mm. Cu to lp ct

lc v vt liu m gn ging b lc nhanh.

Do tc lc chm, trong b lc ng thi xy ra cc qu trnh lm sch nc sau

y:

Qu trnh sa lng

Qu trnh hp ph

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Qu trnh lc

Qu trnh x l sinh hc.

y b vi chc nng thu gom nc lc c xy dng bng cch xp cc tm beton

hoc gch so le to cc khe h cho nc chy nh hn. Khe h phi nh khng lt

vt liu m.

IV.5.2.3 Nguyn l hot ng:

Vn hnh:

Be lc thng cao khong 3 m vi lp ct lc dy 1,0 -- 1,2 mt. Ct lc l ct mn,

c kch thc hiu qu 0,15 -- 0,35 mm, nh hn nhiu so vi ct lc nhanh.

Qu trnh lc m t nh sau

Nc th c bm Pi y qua van Vi vo ti phn phi T, t y nc vo b,

c lc qua lp ct mn vi tc rt chm: 0,1 -- 0,3 m/h.

Khi mi khi ng, tc lc ch c hiu chnh mc 1/2 vn tc thit k v tng

dn trong 12 gi u tin ti vn tc thit k, lng nc u ny phi x b Sau 12 n 36

gi (nu dng ct mi cng phi ko di giai on ny vi sinh pht trin cng lu cng

tt, c th ti 2 --3 tun) bt u thu nc lc.

Trong qu trnh lc, lp vt liu lc b tc dn, tr lc tng dn. gi tc lc n

nh cn nng dn mc nc d trong b lc.

V. st trngv.lUUNHNGHUA:

- Kh trng l qu trnh tiu dit cc tc nhn gy bnh trong nc.

i vi cc cht st trng nc cp c 2 chc nng: tiu dit cc mm gy bnh v

bo v h thng d tr v phn phi ncV. 2 cc Tc NHN ST TRNG: ho cht: clo, cc hp cht

cha clo hot ng, ozon, axit v baz,...

cc tc nhn vt l : nhit, bc x uv, lc v lngbc x : in t

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Trong 2 tc nhn ph bin nht l clo (v cc hp cht clo hot ng) v ozon.

Axit v kim i khi cng p dng v pH >11 hoc pH


45/51

V. 4MUT SU Tc NHNKHU TRNG THUUNG GUP

V. 4. Clo

Cc cht ho hc c s dng nhiu nht kh trng clo l: kh clo, cc

hypoclorit natri NaOCl, cc hipoclorit canxi Ca(OCl)2, cc monocloramin NH4CI v ioxit

clo C102. Trong s cc sn phm ny, chnh clo dng kh l cht m ngi ta dng nhiu

nht kh trng nc sch. Trong cc trm x l nc nh ngi ta hay dng hypoclorit

v cc cht ny d s dng m t gy nguy hi cho ngi s dng. Cloramin tc dng chm

trong nc, od ngi ta s dng chng nhng ni c th m bo thi gian tip xc

tng i lu. T nm 1974, ngi ta s dng ch yu dioxit clo do kh nng kh trng,

oxy ho cc cht hu c v kh c mt phn ln cc mi, v m khng sinh ra cc cht

gy ung th. Tuy nhin dioxit clo l mt kh khng n nh nn phi sn xut ngay ti ni

s dng.

- Thit k h clo ho:

- thit k cn chn trc dng clo s dng, phng php nh lng, sau tnh

kch thc b phn ng, chn h kim sot v cc thit b ph tr

- Trn th trng, clo c mt s dng sau: clo lng nn trong cc bnh (bom) thp.

Khi s dng clo loi ny phi c h thit b x clo nhit phng, khi clo s chuyn v

dng kh, ho tan clo trong nc sch c dung dch clo gc ri nh lng dung dch clo

vo nc cn x l. y l dng clo r nht nhng kh dng nht (cn thit b pha v nh

lng chuyn dng, kh t).

- Dng clo ph bin th 2 l dng bt, v d canxi hypoclor, trc khi s dng s

pha thnh cc dung dch trong cc bn plastic

- Dng th 3 hay gp l natri hypoclor. y l cht ty trng cng nghip, thng

dng lng v dung dch ch cha ti a 15% Clo hot ng, Vit Nam nng clo hot

ng mc 80g/l

- u im ca vic s dng clo:

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- Kh trng nc c thc hin bng kh clo c nn vo trong nhng bnh thp

chu p lc cao v c a vo nc nh h thng van iu chnh lng kh clo thot ra.

Cch ny c u im tit kim c din tch s dng, thun tin trong vic vn hnh

- Clo c rt nhiu u im p ng c tiu chun la chn cht kh trng nn

hin nay phng php kh trng bng clo c dng nhiu nht (80%) cc phng php

kh trng trn th gii). Tc dng kh trng ca cc hp cht c clo hot tnh chnh l

ch sau khi ho tan vo nc chng to thnh axit hypochlorous (HOC1) v cc ion

hypochlorite (OC) l nhng cht khi tip xc vi mng t bo ca vi sinh s lm cn tr qu

trnh trao i cht dn n chng b cht.

- Nhc im:

- Khi cho clo vo nc c th ko theo mt s hiu ng ph nh clo tc dng vi cc

cht hu c ca nc i khi c th to ra cc cht gy ung th (trihalometan) hoc gy

mi kh chu (clorofenolat)

- clo khng mnh loi b hon ton mt s vsv nh virut v ng vt nbo.

- Clo l cht c mnh do vy cn c cc bin php m bo an ton nghim

ngt

v.4.2 Ozon

Ozon c cng thc ho hc l O3, l mt kh khng n nh v kh nng oxi ho cao.

O3 c s dng lm cht kh trng t u nhng nm 1970.

+ Cc tnh cht ca 03:

- Kh nng oxy ho: kh nng oxy ho l c tnh rt tt lm cho n tr thnh mt

cht hay c s dng trong cng ngh x l nc. Tht vy, ozon lm gim mu, mi v v.

N cn ph hu cc cht c ngun gc phenol, oxy ho cc ion st v mangan ho tan bin

chng thnh cc ion khng tan. Hn na kh nng oxy ha cao cn ph v cc hp cht hu

c ca st v mangan m cc phng

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php kh st v mangan thng thng khng lm c. Mt khc, tri ngc vi clo, ozon

khng c tc dng vi nit amoniac. Tuy nhin, mt s nghin cu mi y tit l s

ozon ho mt s cht hu c v mt s thuc tr su c th to thnh cc cht gy ung th.

- Kh nng kh trng: kh nng kh trng ca O3 cao hn clo t 10-100 ln v

tiu dit tt c cc loi vsv. N dit c hiu qu i vi cc bo t v cc nang l cc vsvbn vng nht.

Lng O3 cho vo nc kh trng ph thuc vo cc loai nc, nhu cu oxy ho

cc cht hu c v v c. Cng nh i vi clo, cn duy tr mt nng ozon d no sau

thi gian tip xc xc nh.

+ Ccphng php sn xut O3

Hai phng php sn xut ozon chnh da trn tc dng quang ho hc ca cc tia

cc tm (phng php to ozon trong kh quyn) hoc tc dng ca s phng in di p

sut cao trong khng kh kh (phng php s dng trong cng nghip). Ngi ta cng c

th sn xut ozon t khng kh hoc oxy nguyn cht, v khi lng, hiu sut ca mypht ozon gn gp i khi l oxy nguyn cht.

+U im ca vic st trng bng O3: hot tnh cao, x l c rt tt c ng vt

nguyn sinh, t gy mi kh chu, khng to ph phm l cc hp cht c clo c hi.

+ Nhc im:

- Nhc im ln nht: 3l cht phn hu nhanh to thnh 02 nn thi gian tn ti

trong nc ngn (20-3 Op) =>phi sn xut ngay ti ch dng ngay v khng c tc dng

bo v h phn phi.

- Trong vic sn xut 3,gi thnh nng lng in s dng v bo dng l rt ln.

Bng: so snh kh nng kh trng ca mt s cht kh trng thng gp da vo

h so dit vi sinh:

53


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Cht kh trng Vi khun Virut Bo t

Ozon (03) 500 5 2

HOC1 20 1,0 0,05

ocr 0,2


49/51

3m

Cn

B lng trong'. Th tch b = 200m3; chiu cao b: 6m; tc dng = 0,9 -

1,2 mm/s; c 6 ng dn nc ra t ng trung tm. Loi b ny tn t din tch nht, kh

nng to cn trit nn nc ra tng i trong nhng kh vn hnh, i hi ngi vn

hnh phi c trnh , phi u t nhiu hn.

Giai oan 3: Nc trong sau khi lng cn c a vo b lc. Nc c lc bng

ct Silic (95%), ct sc cnh, c ng knh 0,8 - 1,2 mm. dy lp ct l 1,2 m. Ct s

dng 1 ngy, ra 1 ln. Hiu qu lc l lOmg cn/1 nc.

Giai oan 4: Kh trng. Nc sau khi lc c kh trng bng Clo ha lng ri a

vo cc b cha.

Giai oan 5: Qua h thng trm bm cp 2, nc sch c a i phn phi v cung

cp cho ngi s dng.

VII. KDt lun

- Nc sau x l cn m bo an ton cho ngi s dng. Cc tiu chun phi m

bo an ton cho sc khe, mi v, thm m, v ph hp cng nhiu cng tt cc tiu chun

quc t. Nc cp sinh hot phi m bo khng c vi sinh vt gy bnh, nng cc cht

c, cc cht gy bnh mn tnh. trong, mn, mi v v tnh n nh phi cao.

- i vi nh my nc cm Thng l mt trong nhng nh my tt nht ca Vit

Nam, vi cng ngh hin i, u t ln. Nh my p ng c nhu cu s dng nc sch

ca dn c thnh ph Hi Dng.

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MC LC

| Nhu cu s dng nc Vit Nam..........................................................................................................1

II. nh gi ngun nc mt ca Vit Nam.............................................................................................2

Tin x l ......................................... ......................................... ......................................... ............................. 5

II.Keo t- to bng...........................................................................................................................................7

II. 1. Cu to ht keo v tnh bn ca h keo..................................................................................................8

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II. 2. C ch keo t - to bng......................................................................................................................11

II. 4 Cc yu t nh hng n qu trnh keo t............................................................................................20

II4.1 YutpH......................................................................................................................................20

II.4.2 Yu t hu c..........................................................................................................................21

II. 5 ngdng...............................................................................................................................................21

///.Lng..............................................................................................................................................29

III. 1. Khi nim ng v b ng..................................................................................................................29

III. 2 L thuyt tnh tc lng ht - Phng trnh Stoke........................................................................31

III.3 Phn loi cc kiu loi lang...............................................................................................................35

III. 5. Cc dng b lng c bn....................................................................................................................36

V. Lc....................................................................................................................................................41

IV. 1 Khi nim...........................................................................................................................................41

IV.............................................................................................................................................................2

L thuyt lc...............................................................................................................................................41

IV. 3 Cc c ch lc v cc hin tng lin quan..........................................................................................42

IV. 4 Phn loi............................................................................................................................................44

IV. 5. Cc k thut lc ph bin trong x l nc cp....................................................................................45

V. St trng.................................................................................................................................................................49

nh ngha:..........................................................................................................................................49

F2 Cc tc nhn st trng:.........................................................................................................................49

V. 3........................................ ......................................... .................. Cc tiu chun la chn cht kh trng

50

V.................................... ......................................... .................... ...... 4 Mt s tc nhn kh trng thng gp

51

V. Nh my nc Cam Thng ................................................................................................................54

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