Question

Describe about the fundamentals of facultative ponds

Answer 1

• Facultative pond :- functions aerobically at the surface while anaerobic conditions prevail at the bottom.They are often about 1 to 2 m in depth. The aerobic layer acts as a good check against odour evolution from the pond
• Mechanism :-

1. The functioning of a facultative stabilization pond and symbiotic relationship in the pond are shown below. ( at the last)
2. Sewage organics are stabilized by both aerobic and anaerobic reactions. In the top aerobic layer, where oxygen is supplied through algal photosynthesis, the non-settleable and dissolved organic matter is oxidized to CO2 and water.
3. In addition, some of the end products of partial anaerobic decomposition such as volatile acids and alcohols, which may permeate to upper layers are also oxidized periodically. The settled sludge mass originating from raw waste and microbial synthesis in the aerobic layer and dissolved and suspended organics in the lower layers undergo stabilization through conversion to methane which escapes the pond in form of bubbles.

• Factors affecting pond reaction :-

1. wastewater characteristics and fluctuations.
2. environmental factors (solar radiation, light, temperature)
3. algal growth patterns and their diurnal and seasonal variation)
4. bacterial growth patterns and decay rates.
5. solids settlement, gasification, upward diffusion, sludge accumulation.

• Design parameters :-

1. The optimum range of depth for facultative ponds is 1.0 - 1.5 m.
2. volume is around 10,000 Cubic meter.
3. Retention time - 5 to 30 days .
4. Normal BOD loading 40- 160gm /cubicmetre /day
5. Service should be every 10 years.
   
   
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