Several factors may significantly affect or aid, the hydraulic and biological behavior of wastewater stabilization ponds.
Some, not all, can be taken care of during designing a waste stabilization pond.
Natural factors 1) Temperature Temperature directly influences the physical, chemical and biological activities in a waste stabilization pond system.
Rate of photosynthesis and cellular metabolism are directly proportional to the pond temperature.
Ponds should be designed for most adverse temperature conditions.
At lower temperature, dissolved oxygen present has a tendency to remain in pond longer.
As the temperature rises, dissolved oxygen is likely to be liberated to atmosphere, especially under supersaturated conditions.
The oxygen production by Algae in wastewater through photosynthesis is also temperature dependent.
All ponds perform well on a sunny, cloudless day at an air temperature above 20 degree C and mild wind conditions.
At a temperature above 35 degree C, the rate of photosynthesis declines rapidly and at temperatures above 45 degree C, it altogether stops.
High temperatures stimulate growth of blue green algae at the expense of more efficient green algae.
At the same time, aerobic bacteria in wastewater consume oxygen at higher rate creating conditions to form anaerobic patches in the waste stabilization pond.
Sudden reduction in temperature slows down algae activity and oxygen production.
Algae will move to lower layers, the green color will reduce and pond performance will drop.
2) Rainfall Rainfall influences pond performance.
Detention time reduces when it rains.
Besides, heavy shower dilutes the contents of shallow ponds reducing the food available to biomass.
Rainfall adds oxygen to a pond system by increasing turbulence.