Presentation on

Oxidation Ponds

Oxidation Ponds

What are Oxidation Ponds ?

Oxidation Ponds are large earthen basins in which waste water is treated by natural processes involving bacteria and in many instances algae.

These are shallow basins used to treat raw water

Rate of waste oxidation is slower in Oxidation Ponds

Types Of Oxidation ponds

Aerobic Ponds

Anaerobic Ponds

Facultative Ponds

Maturation or Tertiary Ponds

Aerobic Ponds The aerobic pond are large in dimension &

shallow pond that used for wastewater treatment by natural process involving both algae and bacteria.

New Algae

Algae

O2

Bacteria

CO2, NH3, PO4, H2O

New Bacteria

Organic Bacteria

Solar Energy

Design Considerations

Parameter Value

Depth in mts. 0.15 - 0.5

Retention time (day) 2-6

BODu loading (lb/acre-day)

100-200

BODu removal (%) 80-90

Algae concentration (mg/l)

100-200

Re-circulation ratio 0.2-2.0

Effluent suspended solids concentration (mg/l)

150-350

Anaerobic Ponds Anaerobic Ponds requires no Dissolved Oxygen

for microbial activity as the organisms use O2 from compounds such as NO3, SO4 as their hydrogen acceptors and give end product such as methane, carbon dioxide etc.

These ponds are basically Sedimentation ponds High waste water loading which depletes all O2 Solids settles in pond basin Anaerobic digestion of sludge occurs in pond

bottom

Large Organic Loading

O2 Req > O2 Supply

Enhanced H2S- Formation

Increase In Turbidity

Reduced Light Penetration

Reduced Photosynthesis

Reduced O2 Formation

Anaerobic Conditions

how anaerobi

c conditions occurs

in oxidation ponds?

Anaerobic digestion process

Hydrolysis - Complex organics (proteins and fats) broken down to simpler compounds by various bacteria

Acidogenesis (Fermentation) – Fatty acids and alcohols oxidized, amino acids and carbohydrates fermented , forms volatile fatty acids and hydrogen

Acteogenesis – conversion of complex fatty acids to acetic acid

Methnogenesis - conversion of acetic acid to methane and CO2 and CO2 ,H2S to methane

Process When temperature rises above 15o C digestion

generates enough biomass which causes pond surface to bubble – biogas (70% CH4 and 30% CO2)

Digested solids accumulate – cleanout in 1 to 3 years

Pond Characteristics

Hydraulic detention time is short – 1 day

Depth – 2 to 5 m (usually 3m)

Design is highly empirical – based on volumetric load (gm BOD/m3/day)

For e.g. 100 gm BOD/m3/day to 3 m deep pond=3000 kg/ha/day

Role of pH

Below pH 7.0 then H2S forms and causes odor

Below ph 6.2 then conditions became toxic

ADVANTAGES Gives energy whereas aerobic requires

energy. Very high concentration can be treated

efficiently whereas not possible in aerobic ponds.

LIMITATIONS Standard BOD cannot be maintained under

anaerobic process as suspended solid increased.

Organic matter convert to CO2, CH4 which is difficult to separate from bacteria.

Facultative Ponds These are neither fully aerobic nor fully

anaerobic. They are often about 1 to 2 m in depth and favor

algal growth along with the growth of aerobic, anaerobic and facultative microorganisms.

Such ponds are aerobic during day time. In the remaining hours the pond bottom may turn anaerobic.

Top Pond water is aerobic and supports very high density algal population

Bottom water is an anaerobic condition in which sludge is digested

Algae generate O2 by photosynthesis during the day ,which is useful for oxidation of waste by bacteria

Bacteria degrade waste, uses O2 and generates CO2, algae use CO2 and generate O2

Wind

CO2

An

aero

bic

Zon

eA

erob

ic

Zon

e

Fac

ulta

tive

Z

one

O2

algae

(CO2, NO2, PO4, SO4)

Aerobic Bacteria

Biomass

Biomass

Anaerobic Bacteria

Sludge Blanket

Organic acids & Compounds of C, N, P, S

Impermeable lining

Sunlight

Maturation / Tertiary Ponds

These are similar to aerobic ponds but are very lightly loaded with organic wastes.

Generally used for upgrading effluents from conventional secondary treatment processes.

The principal purpose is to achieve reduction in fecal colliform count and remove nitrogen and phosphorus.

Used to remove pathogenic bacteria and viruses (99.9997%) - e-Coli removal

Solar disinfection – using UV light 1 m deep Total detention time of the order of 10 days Disinfection may be used, if required

Thanks