3e maturation ponds

7/27/2019 3e Maturation Ponds

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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

-

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

3e maturation ponds

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