3e maturation ponds
TRANSCRIPT
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Professor Mara
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zz
Why? Different ponds have different functions
,
but faecal bacterial removal is high
Theory indicates that a series of smallTheory indicates that a series of small
overall sizeoverall size
also observed in practice
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o, e er a w c s e er w c s e er
A F M MM
or (b):
M MMF
Size and number of maturation ponds depend.
theory indicates that, for max. performance,theory indicates that, for max. performance,
ma ura on pon s s ou e e same s ze.ma ura on pon s s ou e e same s ze.
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E. coliE. coli r m v l in W Pr m v l in W P
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kinetics in a completely
mixed reactor:== ++ee . co
value of kB is strongly temp. dependent:
== T20T20. .. .
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So, for a series of onds:So, for a series of onds:
A F M MN N
NNii
(1+ k(1+ kBBanan))(1+ k(1+ kBBfacfac))(1+ k(1+ kBBmatmat))nnee
maturation
,
or take as 5 107 per 100 ml
e nown requ re e uen qua y poss y
104 E. coli per 100 ml for irrigation)
an & fac known, butbut matmat and nand n both unknownboth unknown
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Ne = Ni / [(1+ kBan)(1+ kBfac)(1+ kBmat)n]
so: one equation, two unknowns:
,
2 ponds @ 7 days, or 3 ponds @ 5 days,
and see if Ne is < required effluent value
or (and this is better) calculate the value ofcalculate the value of
for n =f o r n = 11 then for n =then for n = 22 etc. untiletc. until
matmat
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: minimum value of: minimum value of , in ran e, in ran eminmin
3355 days.days.A min. value is assigned to
hydraulic shorthydraulic short--circuitingcircuiting. Maraisrecommends 33 daysdays in warm climates
~5 da s in tem erate climates
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: minimum value of: minimum value of , in ran e, in ran eminmin
335 days.5 days.A min. value is assigned to
hydraulic shorthydraulic short--circuitingcircuiting. Maraisrecommends 3 days3 days in warm climates
~5 da s in tem erate climates
Solution to equation might be, for examplefor example:
n = 1 mat
= 150
n = mat =
n = 3 mat = 4.2
n = 4 mat = 1.6 STOP!STOP!
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(a) Ignore values of(a) Ignore values ofmatmat >> facfac and
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Therefore:Therefore: 1.
min. mat mat
BUT ALSO:BUT ALSO: 33.. BOD loading constraint:BOD loading constraint:
s(Ms(M11))
.. s(fac)s(fac)
To calculate s(M1), first determine Le(fac)
= L from first-order e uation forunfiltered BOD removal with k1 = 0.1
1 1. .
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n ac s mp es o cons er cons ra nn ac s mp es o cons er cons ra nfirst:first:
MM11 == 1010LLiiD/D/00..7575s(fac)s(fac)
= = = s
and follow theand follow the 44--step procedure step procedure
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Maturation Pond DesignMaturation Pond Design
ourour--step proce urestep proce ure
==minmin
s acs ac
= Le fac
[unfiltered BOD]
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ep :ep :
maturation ponds:mm == {[N{[Nii//NNee(1+ k(1+ kBBaa))(1+ k(1+ kBBff))(1+ k(1+ kBBM1M1)])]
1/n1/n 1}/k1}/kBB
now the retention time in M2, M3 etc.now the retention time in M2, M3 etc.
Solve for n = 1, 2, 3 etc. andSTOPSTOP when m
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Step 3:Step 3:
Choose most appropriate combination* ofmin
mat , mat .
** ie,ie, the one for which their product is athe one for which their product is a
MINIMUM, as this givesMINIMUM, as this gives the least land areathe least land area
..
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Step 4:Step 4:
Determine mat. pond areas taking net
.
f= 2AfD/(2Qi 0.001eAf)
Rearrange this for mat. ponds:AAm = 2Q= 2Qimm/(2D + 0.001e/(2D + 0.001emm))
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es gn empera ures
Des. temp. = mean temp. of coldest month
or ma ura on pon s:or ma ura on pon s:
Des. tem . =Des. tem . = mean tem . of coolest monthmean tem . of coolest monthin the irrigation seasonin the irrigation season
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e i B an B fac B mat
But shouldBut should samesame value of kvalue of kBB
be used forbe used for
anaero c, acu a ve an ma ura on pon sanaero c, acu a ve an ma ura on pon s
Probably not, but not too much data available
inin facultative ondsfacultative onds kk seems to be a functionseems to be a functionof organic loading as well as of time andof organic loading as well as of time and
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Northeast Brazil, 25 oC
161)
12ta(d
8co
8
varae
4remo
0 200 400 6000FC
0 200 400 600BO D loading rate (kg/ha d)
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Northeast Brazil, 25 oC
xper men une ay
= 29.1 days= 29.1 daysRetention BOD SS FCFCtime (d) (mg/l) (mg/l) (/100ml)
Raw ww 240 305 4.6 107
A1 6.8 6363 56 2.9 106
F1 5.5 45 7474 3.2 105
M1 5.5 25 61 2.4 104
M2 5.5 19 43 450450
M3 5.8 17 45 30 Unfiltered
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Removal ofRemoval of excreted pathogensexcreted pathogens in deepin deep** ponds inponds in
- oo
*3.42.8 m = 21 days
wwRetention time 1 5 5 5 5
F. coliformsF. coliforms 2E7 4E6 8E5 2E5 3E4 7E37E3
F. enterococci 3E6 9E5 1E5 1E4 2E3 300
ampy o ac ersampy o ac ers .
SalmonellaeSalmonellae 20 8 0.1 0.02 0.01 00Enteroviruses** 1E4 6E3 1E3 400 50 9
Bacterial nos. per 100 ml ** Viral nos. perViral nos. per10 litres10 litres
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Mechanisms of Pathogen Removal in WSPMechanisms of Pathogen Removal in WSP
Viruses:Viruses:
Adsorption & sedimentation (probably)
::Several ossible res onsible factors e :
Time & TemperatureTime & Temperature UV radiation ga ox ns gg Low CO2 High pHHigh pH Predation by protozoa and micro-invertebrates
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DO pH Temp.********** NH3-N Total PTotal P Sol. P**********
Diurnal
********** BOD SS var a on
in fac. pond
SS********** e uen
quality Chl. a FC
nor eas
Brazil
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16
t(d)
8
12
aecoa
Northeast Brazil
~
4
Cremoara
0 200 400 600BOD load ing ra te (kg/ha d)
0FC
1200
1600
a()
800hoo
a
400Inp
ch
0 200 400 600BOD load ing ra te (kg/ha d)
0
So.So.
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161)
12sa(d
8aeco
moara
4
FCrem
0 500 1000 1500 2000In -pond ch lo rophy ll a concentra tion (g/l)
0F
In p on d ch lo ro ph yll a concentra tion (g/l)Thus the ond al ae are lar el res onsible
for FC (and other excreted bacterial) removal
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4. Laboratory work in UK and fieldwork in
High pH (>High pH (>99..44))
High light intensity with high DOHigh light intensity with high DO
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SunlightSunlight
Rapid
Increased pondHigh
H >9.4Photo-oxidation
FaecalFaecal
diedie--offoff
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SunlightSunlight
Rapid
Increased pondHigh
H >9.4Photo-oxidation
FaecalFaecalmaximizemaximize
diedie--offoff
FC spend inFC spend in
No equations, but:
of high pHof high pH
--
Encourage stratification in maturation pondsEncourage stratification in maturation ponds
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Different mechanism as V. cholerae is
resistant to hi h H a H of 9 is routinelused in clinical microbiology to isolate it)
V. cholerae killed by low concentrations of~ ,
essential
Field data from northeast Brazil:
Removal ofRemoval of Vibrio choleraeVibrio cholerae OO11 in WSPin WSP
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Removal ofRemoval ofVibrio choleraeVibrio choleraeOO11 in WSPin WSPNortheast Brazil April-July 1992 2527 oC
Series ofSeries of 1010 ponds (ponds (11--day anaerobic pond followed by nineday anaerobic pond followed by nine22--day pondsday ponds all too low for use in practice!) all too low for use in practice!)
.. .(per litre) 100 ml) (mg/l) (g/l)
--An. pond 2828 8E6 79 --
.
1st mat. pond 3 1E6 53 1132nd 8 5E5 43 703rd 3 2E5 36 115
4th
00 66EE44 31 11311 days
5 0 4E4 28 1146th 0 8E3 17 163
8th 0 2E3 11 267
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Brazil, India andBrazil, India and
% Rem = 100(1 0.14e0.38)
lower 95% confidence equation:**
100 [1100 [1 0.41exp( 0.49 0.41exp( 0.49 + 0.0085+ 0.008522))
** Use for designUse for design