Anaerobic Ponds -Treatment Process The rate of anaerobic processes depends highly
on temperature, in particular the methanogenic bacteria accelerate their metabolic activity with temperature. At higher temperatures BOD is therefore more
effectively removed, especially the BOD-dissolved. In cold climates anaerobic ponds mainly act as
settling ponds In case the influent contains sulphate or nitrate,
also sulphate reduction and denitrification is occurring.
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Anaerobic Pond –Pollutant removal BOD removed by sedimentation and anaerobic
decomposition Ammonia nitrogen removal by volatilization, algal
uptake Nitrite reach infleunt may get denitrified Phosphorus removal is minimal Removal of bacterial pathogens in anaerobic
ponds is poor (1 log unit faecal coliform reduction)
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Anaerobic Ponds - Odor Odour formation from anaerobic ponds is
frequently reported. One of the main odorous compounds is H2S, the
product of sulphate reduction.
In a well designed and operated anaerobic pond
the pH is kept in a range around 7.5. In this range most of the sulphide is present as the bisulphide ion, which has no odour.
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Anaerobic Ponds -Odor Odor Reduced By – Raising the pH to around 8 by lime addition to prevent the formation of odorous H2S. – Recirculation of final maturation pond effluent to the anaerobic pond. This measure will result in an aerobic top layer, in which sulphide is oxidised to sulphate. – Reducing the applied organic loading rate by providing extra anaerobic ponds in parallel or by increasing the depth – Stimulating the establishment of a scum layer on top of the anaerobic pond, for instance by spreading a thin layer of straw on the surface.
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Anaerobic ponds- Design Anaerobic ponds are designed on the basis of
volumetric organic loading (kgCOD/m3/day).
– Van = Pond volume (m3) – A = Surface are (m2) – D = Average pond depth (m) – BODin = Influent concentration (kgBOD/m3) – Q = Flow rate (m3/day) –
= volumetric organic loading rate (kgBOD/m3/day)
It is quite common to use pond systems in series of two or three
based on minimum month-averaged air temperature (0C) Temp < 10
0.10
(40 % removal)
Temp 10-20
0.02 * Temperature – 0.10 (then % remvola is -2* Temperature +20 )
Temp >20
0.30 (60 % removal)
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Operation and maintenance Regular desludging – The performance of anaerobic ponds may deteriorate when ponds are getting full with sludge. – The accumulated sludge causes the HRT to decrease and this may prevent complete settling and digestion of particulate matter
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Facultative Pond Aerobic layer
Anaerobic Layer
Facultative ponds are the second treatment step
in a pond system. Depth of pond -1.5 – 2.5 m deep earthen basin
with an embankment slope of 1:3. Detention time 5 – 10 days.
.
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Facultative Pond-Treatment mechanism
sedimentation and anaerobic digestion. Sludge BOD removed -while desludging and
anaerobically transformed into methan gas
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Facultative Pond-Treatment mechanism The oxygen produced by algal photosynthesis in
the top layer is used for the decomposition of organic matter in deeper layers by heterotrophs. Symbiotic interrelationship referred to as ‘Algae-
Bacteria Symbiosis’ .
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Facultative Pond –Pollutant removal BOD removed by sedimentation and aerobic and
anaerobic decomposition Ammonia nitrogen removal by volatilization
(during day time when pH is increase due to production of CO2), algal uptake , ammonification Nitrate -denitrified Phosphorus removal is minimal Removal of bacterial pathogens in anaerobic
ponds is poor (1-2 log unit faecal coliform reduction)
NORWEGIAN UNIVERSITY OF LIFE SCIENCES
Facultative Ponds- Design Design based on organic surface loading rate load
