7/29/2019 3b Anaerobic Ponds

1/21

ANAEROBICANAEROBICPONDSPONDS

ro essor ara

7/29/2019 3b Anaerobic Ponds

2/21

dissolved oxygen

depth range 15 m; depends on ground

con ons usua y m

importantimportant

7/29/2019 3b Anaerobic Ponds

3/21

ALGAE:ALGAE:

occasional surfaceoccasional surfacefilm of sulphidefilm of sulphide--

toleranttolerant

ChlamydomonasChlamydomonas

7/29/2019 3b Anaerobic Ponds

4/21

ALGAE:ALGAE:

occasional surfaceoccasional surfacefilm of sulphidefilm of sulphide--

toleranttolerant

ChlamydomonasChlamydomonas

OPERATION OF ANAEROBIC PONDSOPERATION OF ANAEROBIC PONDS

sedimentation of settleable solids and

intense anaerobic digestion (>15oC) and

copious biogas (CH & CO ) production

high BOD & SS removalhigh BOD & SS removal

functions much like an open septic tank

7/29/2019 3b Anaerobic Ponds

5/21

sludge layer

About 30% of influent BOD leaves as biogas

same groups of anaerobic bacteria

digesters require same environmentalrequire same environmental

con ons eg, p > .con ons eg, p > .

7/29/2019 3b Anaerobic Ponds

6/21

based on volumetric BODbased on volumetric BOD loadinloadin

VV = L= Lii Q/V g/mQ/V g/m33dd

= L= L // =

mg/l (= g/m3)

VQ

Q = flow, m3/d

= vo ume, m

1 ddV/Q =V/Q =

(retention time, days)

aa

1 d1 d

7/29/2019 3b Anaerobic Ponds

7/21

Design range for normal domesticDesign range for normal domestic

was ewa er:was ewa er:

100100 400 400

if 400, then risk ofodourodourrelease

7/29/2019 3b Anaerobic Ponds

8/21

caused mainly by hydrogen sulphide gashydrogen sulphide gas(H2S)

4 ponds by obligately anaerobic sulphate-

reducing bacteria (eg, Desulfovibrio spp) 2 , ,

depends on pH:depends on pH:

7/29/2019 3b Anaerobic Ponds

9/21

S=HS-

2

Effect of H on h dro en sul hide

bisulphidesulphide equilibrium

7/29/2019 3b Anaerobic Ponds

10/21

Odour, continued

odour not usually a problem if sulphateodour not usually a problem if sulphate

concentration

7/29/2019 3b Anaerobic Ponds

11/21

Anaerobic PondsAnaerobic Ponds

temperature, but insufficient reliable field

a a ava a e o eve op goo es gnequation

Design temperatureDesign temperature: mean air temp. inmean air temp. in

pond temp. some 2pond temp. some 233ooC warmer)C warmer)

Minimum retention time of 1 dayMinimum retention time of 1 day

7/29/2019 3b Anaerobic Ponds

12/21

BOD5 Percentage

Temp (oC) loading BOD

g m ay remova

10 100 40

1020 20T 100* 2T + 20*

2025 10T + 100* 2T + 20*

>>

* = o,

7/29/2019 3b Anaerobic Ponds

13/21

Raw wastewater 306 g/m306 g/m33dd

A2 A3A2

A4

129 g/m3d

Northeast Brazil, ~25Northeast Brazil, ~25 CC

7/29/2019 3b Anaerobic Ponds

14/21

Retention BOD SS FC

time (mg/l) (mg/l) (per

Raw ww 245245 310 4.7 107

** **** 6.. .

A3 0.4 45 64 5.0 106

A4 1.9 49 57 4.7 106

** ****

Not worth having (at least for domestic ww)

7/29/2019 3b Anaerobic Ponds

15/21

Northeast Brazil 25Northeast Brazil 25ooCC

Pond Retention Volumetric Percentage

Code time BOD load BOD(days) (g/m3 day) removal

.

A6 1.01.0 215 7676

A4/1 1.9 129 80

A1/3 2.0 116 75A1/2 4.0 72 68

.

7/29/2019 3b Anaerobic Ponds

16/21

very good removal of BOD & SSvery good removal of BOD & SS this has effect ofreducing land areareducing land area

requ remen or overa pon sys emrequ remen or overa pon sys em, soanaerobic onds should alwa salwa s be used

(except at small works serving only a few

thousand people)

7/29/2019 3b Anaerobic Ponds

17/21

Operation and maintenanceOperation and maintenance1. fl breedin in scum la er ma be a

problem: use a suitable larvicide

.

occurs every n years:

(Pond volume, m(Pond volume, m33))n =n =

Sludge accumulationSludge accumulation33 (Population)(Population),,

~ 3

~0.08 m3/cap.yr in Europe

7/29/2019 3b Anaerobic Ponds

18/21

en ra

CYPRUS

7/29/2019 3b Anaerobic Ponds

19/21

7/29/2019 3b Anaerobic Ponds

20/21

7/29/2019 3b Anaerobic Ponds

21/21

Anaerobic pond, Cyprus