Oxidation ponds can successfully treat either raw or settled sewage. The latter is more often applied. The loading in terms of 5-day BOD may vary from 55 kg per day per hectare for tropical regions like our country. The pond area required per 1,000 persons may vary roughly from 0.2 to 0.4 hectares. It is claimed that the BOD removal is as much as 90 per cent and coliform removal is even higher, 99 per cent, which speaks of the great efficiency of these ponds for the process of sewage oxidation.

Oxidation ponds which are rectangular shaped (l / b = (3/2)) having side slopes (1:1.5) are constructed by building embankments of earth. Usually more than one in number, these are operated in parallel or series for the sewage oxidation process. Operating ponds in series generally causes increased reduction of BOD by preventing short-circuiting and increase oxygen in sewage.

On the other hand, parallel operation may be desirable to distribute the raw BOD load and avoid potential odor problems. They are of shallow depth usually 0.9 to 1.5 m and as such effective in permitting penetration of sunlight to all parts of the sewage, encouraging algae growth. Influent is applied in the middle of the wastewater oxidation pond and allowed to be spread by the action of wind currents, which prevents any odor nuisance due to concentration.

Oxidation ponds are suitable in case of small cities for sewage oxidation, where relatively large land areas are easily and cheaply available, and in tropical countries having dry climate and warm temperatures. They possess such advantages as low cost, quickness of construction, easy maintenance and high efficiency of BOD removal. Disadvantages are nuisance due to mosquito breeding and odors.