keo tu tao bong
TRANSCRIPT
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KEO T - TO BNG
Coagulation - Flocculation
Gii thiu chung loi b cht rn l lng (SS SuspendedSolid) trong nc/nc thi
Lng (Sedimentation)
S- khi lng ring ca ht (kg/m3)
L- khi lng ring ca cht lng (kg/m3)
d - kch thc ca ht (m)
- nht ng lc hc (kg/ms)
vg
dS S L= 18
2
( )
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S lin h gia kch thc ht v thi gian lng
20 nmHt keo10-5
2 nmHt keo10-4
8 ngyVi khun10-3
2 git st10-2
2 phtCt mn10-1
10 giyCt1
1giySi10
Thi gian lng( su 1m)
Loi htKch thc ht(mm)
Gii thiu chung (tt) Tuyn ni (Flotation)
Bt kh c thm vo
Cc cht rn l lng s bm vo b mtca bt kh v ni ln
Lc (Filtration)
Ch hiu qu khi kch thc ht > 1m
Phi gim hm lng SS trnh nghnct lc
Keo t to bng (Coagulation Flocculation)
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Keo t to bng
Mc ch: tch cc ht cn c kch thc0,001m < < 1m, kh tch loi c bngcc qu trnh l hc thng thng nh lng,lc, tuyn ni.
Ht keo: 2 dng chnh Keo k nc: t st, oxit kim loi,
Khng c i lc vi mt nc D keo t a s l nhng ht keo v c
Keo a nc: proteins, polymers,
Th hin i lc vi nc Hp th nc v lm chm qt keo t a s l nhng ht keo hu c
c tnh ca ht keo Kh nng lng rt chm (chuyn ng Brown
gy cn tr qt lng do trng lc)
L tc nhn gy nhim nc e.g tng c (turbidity)
c tnh b mt (in th ,) l yu t quantrng (surface properties)
C xu hng kt hp vi cc cht t mi trngxung quanh (t l din tch b mt:khi lng caohn)
C xu hng tng in tch
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Cu to ht keo
Lc tng tc gia cc ht
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H keo Khi cc ht keo tip xc vi nhau, chng to
thnh cc ht c kch thc ln hn, to bngv kt ta
Lc gia cc ht keo: lc ht v lc y tnhin hoc lc Van der Waals
ln: t l nghch vi khong cch gia ccht
Kh nng n nh ht keo l kt qu tng hp
Fh v F
in th zta < 0,03V Fh thng F. Khi 0th qu trnh keo t cng t hiu qu
S
n
nh h
keo v gi tr
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Nng lng tng tc ca h keo
Cch qt keo t to bng Qt nn lp in tch kp, gim th in ng
zta nh ion tri du
Qu trnh keo t do hp ph ion tri du trnb mt, trung ha in tch to ra im ngin = 0
C ch hp ph - to cu ni
Cc polymer c th ion ha, nh cu trcmch di chng to cu ni gia cc ht keoqua cc bc: Phn tn polymer
Vn chuyn polymern b mt ht
Hp ph polymer ln b mt ht
Lk gia cc ht hp ph polymer vi nhau hoc vi cc ht khc
Qt keo t hp ph cng lng trong qt lng
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Cch (tt)
Trung ha in tch S hp ph cc cht mang in tch tri du vi cc
ht keo
Gim th in th b mt v lm mt n nh h
keo
Hm lng cht keo t tng nng ht keo tng
Qu nhiu cht keo t ti n nh h keo
Qt keo t - hp ph cng lng trong qt lng
Phn nhmPhn st
pH Al(OH)3Fe(OH)3
Cch to cu ni Phn ng 1: phn t polymer kt dnh vi ht keo
(tch in tri du)
Phn ng 2: phn cn li ca polymer trn linkt vi nhng v tr hot tnh trn b mt cc htkeo khc
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Cch to cu ni (tt) Phn ng 3: hin tng ti bn ht keo
Phn ng 4: nu qu tha polymer
C
ch
to c
u n
i (tt)
Phn ng 5: nu khuy trn qu mnhhoc qu lu, lk gia ht keo v polymers b ph v
Phn ng 6: ti bn ht keo
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Cht keo t (Coagulant)
Thng s dng trong x l nc v nc
thi: Fe(III) v Al(III)
FeCl3
Alum
R, ph thuc ln vo pH
Ha hc ca cht keo t C Al3+ v Fe3+ u p/ mnh vi nc
cc hydroxide kt ta
Al3+ + 3H2O Al(OH)3 + 3H+
Fe3+ + 3H2O Fe(OH)3 + 3H+
pH cao:
Al(OH)3 + OH- Al(OH)4-
Fe(OH)3 + OH- Fe(OH)4-
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Cht keo t - Alum
To thnh t qung Bauxit ha tan trong
H2SO4
Dung dch to thnh c loi b tp cht,
trung ha, cho bay hi to thnh cc ming
Nhm Sulfate
C mu xm hoc trng vng (ty vo hm
lng tp cht)
Cng thc: Al2(SO4)3(H2O)n (n = 0,6,10,16,18
v 27)
Alum (tt)Alum ha tan v p/ vi kim trong nc
Al2(SO4)3(H2O)n + HCO3- Al(OH)3 + CO2
+ SO42- + H2O
Kt ta Al(OH)3 mu trng
CO2 to thnh dng bt kh trong nc v bm
trn thnh cc th nghim Jar Test
SO42- tn ti trong nc
1g Alum tiu th ht 0,5g kim
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Alum (tt)
pH < 4
pH = 4,5 5
AlOH2+, Al8(OH)204+
pH > 9,5: Al(OH)4-
pH = 5 9: nhiu dng ktta, ch yu Al(OH)3
Alum (tt)
Nu s keo t (bng Alum) trong vng ti n nh(restabilization):
Tng hm lng Alum s dng thot khi mino ngc in tch
Tng nng SO42-
Thm dd vi tng pH, chuyn sang pha bn phivng ti n nh
Thm cht to bng kt bng cc keo mang in
dng Thm cht keo t mang in m (bentonite, silica
hot tnh) gim in tch dng ca ht keo to bng
trng lng ht keo tng tng vn tc lng
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Hp cht Fe
3 dng mui st ch yu thng gp trongx l nc:
FeCl3.6H2O : Ferric chloride
Fe2(SO4)3(H2O)9 : Ferric sulfate
FeSO4(H2O)7 : Ferrous sulfate
Fe2+ thng kt ta di dng Fe(OH)2 vFeCO3
kim nc t nhin: ch yu HCO3-
thm vi voFe2+ + HCO3- + OH- FeCO3 + H2O
Hp ch
t Fe (III)
Fe2(SO4)3.nH2O OXH FeSO4 bng HNO3
n: 0, 3, 6, 7, 10 v 12
FeCl3.nH2O cho HCl p/ vi Fe, Fe2(CO3)2hoc Fe2O3.
n: 6 (ch yu); 2; 2,5 v 3,5
Cc dng khc Fe(OH)2+
Fe(OH)4-
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M hnh Jar Test
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Jar Test (tt)
Mc ch: xc nh hm lng cht keo t thch hp Tin trnh th nghim
Ly th tch mu xc nh
Thm vo cht keo t vi hm lng tng dn
Khuy trn nhanh trong (3 pht), sau khuychm trong (12 pht), lng
o c ca mu
nh gi hiu sut ca qu trnh keo t to bng
Vn tc lng c
Th tch phn cn lng
Jar Test (tt)Nu khng xy ra keo t, hoc bng cn to thnh
khng thch hp
S dng hm lng cht keo t ln hn
Kim tra kim ca nc thi u vo (thm Soda)
Nhit ca nc thp p/ keo t khng xy ra
Jar Test: nh gi hiu qu ca cc cht keo t khc
nhau
Kh nng x l mu, mi v sn phm phca qu trnh kh trng
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Jar Test
Mt s cht keo t v c
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ng hc qt keo t to bng
Qt keo t: l thuyt v s ph bn ht keo
Qt to bng: s tip xc gia cc ht keo bph bn, theo cc c ch sau
Tip xc do chuyn ng nhit
Chuyn ng Brown/s khuych tn, to thnh cc ht 1m
Perikinetic flocculation
Tip xc t s chuyn ng ca lu cht
Gy ra bi qt khuy trn lu cht
Orthokinetic flocculation
Tip xc do qu trnh lng ca cc ht
ng h
c qt keo t
to bng (tt)
Ht c kch thc nh: ch yu l perikinetic
flocculation
Nu =1m v G=10s-1 th Jok=Jpk
Cc ht c xu hng kt hp to thnh ht
c kch thc 1m bng chuyn ng Brown
(perikinetic flocculation) khuy trn duy
tr tip tc s keo t to bng (orthokineticflocculation)
c tng gi tr G ti u gim
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Perikinetic flocculation
Jpk - tc thay i nng cc ht keo theo thi gian doPerikinetic flocculation
N0 - nng cc ht l lng ti thi im t
- h s hiu qu ca s va chm (tip xc)
k - hng s Boltzman
T nhit tuyt i
- nht ca cht lng
Tc qu trnh Perikinetic flocculation khng ph thuckch thc ht
Jpk t l thun vi nng cc ht l lng
J dNdt
k T Npk = =0
02
43. . .
..( )
Orthokinetic flocculation
d - ng knh ca ht
G - gradient vn tc, ph thuc vo
Thnh phn ha hc ca nc
Bn cht v nng keo trong nc
J pk J d tok . 2
0
3
0 ).(3
...2N
dG
dt
dNJOK
==
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Gi tr G v t G v t ti u ph thuc vo
Thnh phn ha hc ca nc
Bn cht v nng ca bng cn
G ti u gim khi c tng
G qu cao cn b v
t qu cao cn b n mn
Qu trnh to bng:
Ban u, bng cn c to thnh vi gi tr Gcao
Khi bng cn ln dn, gim dn G trnh lmv bng cn
Gi tr G v t
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Cht to bng (Flocculant)
Nng cn thp:
Cn s dng cht keo t vi hm lng cao
Bng cn to thnh nh, d v v lng chm
Cht to bng
S dng tng c tnh ca bng cn (tnh bn,
kh nng lng,)
Silica hot tnh
Bentonite
Vi
polymers
Cht t
o bng vai tr
Thay i pH thay i in tch b mt htkeo
To kim thch hp cho qt keo t
Gim in tch b mt (bng cch hp phtrn b mt ht keo) thot khi vng tin nh ht keo
To cu ni gia cc ht keo to bngcn
Tng bn ca bng cn
Tng nng cc phn t trong dung dch
Tng trng lng ca bng cn
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Polymers
Polymer hu c
Khi lng phn t ln, mch di
Polymer t nhin: hiu qu thp
Polymer tng hp: hiu qu cao hn
Polymer tng hp
C th cha cc nhm mang in Thng s dng trong cc nh my x l nc,
nc thi
Thit b ca qu trnh keo t Trung ha, lm mt n nh cc ht keo
Cht phn ng c khuch tn vo dungdch cng nhanh cng tt
Th tch cht phn ng c thm vo rtnh so vi th tch dung dch cn x l
Thit b khuy trn phi m bo: Gy xo trn thch hp
Phn tn nhanh cc cht phn ng vo dung dch
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My trn tnh (Static Mixers)
My trn tnh (tt) Khng c cc phn linh ng d bo dng
v sa cha
Mng chn, li,c lp pha trong ngng to s xo trn cn thit khuch tncht keo t
Nhc im
Tn tht ct p ln
Khng ph hp khi lu lng dng chy gim
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My trn kh nn (Pneumatic Mixers) Kh nn c s dng nh 1 thit
b khuy trn, c a vo thngqua my khuch tn
Khi bt kh ni ln gy s xotrn
Mc xo trn c iu chnhbi loi my khuch tn v p sut
Nhc im
Cc bng cn c th bm vo bt kh gycn tr qu trnh lng ca bng cn
My trn chc (Mechanical Mixers)
S xo trn c to ra do ng c turbin/chn vt/micho,quay
Tiu hao nhiu nng lng chi ph vn hnh v bodng cao
Lin tc hoc gin on
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Quy trnh cng ngh x l nc thiKCN L Minh Xun
t
Screenings
p bn
To bng B keo t B chnhpH
Treated water
H thu
B iu ha
Song chn rc
B lng 1
B trung ha AerotankB lng 2
B kh trng
NaOHPACAnionic polymer
HCl
Cationicpolymer
Nc Javel
PAC
Anionic polymer
NaOH
HCl