Oxidation pond is a cheap method for sewage treatment. It is also called sewage lagoon, redox pond and water stabilisation pond. It consists of a shallow (1-1.5m deep) body of water. It also has an inflow and outflow. It is used for treatment of both industrial waste and sewage.
Three components are essential for the functioning of the oxidation pond. They are:
The bacteria in the pond oxidise the various organic material producing carbondioxide, ammonia and water. The algae grow by utilising the inorganic material and carbon dioxide in the presence of sunlight. The oxygen requirement for oxidation of the organic matter by bacteria is satisfied mainly by oxygen released by the algae. Also some oxygen is provided by the contact with the atmosphere. Sunlight is an important factor in the functioning of the oxidation pond as the algae relase oxygen only in the presence of sunlight. Hence in cloudy days and at night, the efficiency of the system is decreased.
Oxidation ponds are mainly aerobic with a small anaerobic component operating at night and in the deeper parts. Both aerobic and anaerobic bacteria are present. The effluent of the oxidation ponds are used for irrigation or is released into rivers after proper treatment. Properly maintained oxidation ponds do not cause much problems of bad odour.