| An oxidation pond (also called waste stabilization | | | | for mutual growth and development. Besides these, |
| pond) is an artificial pond in which sewage can be | | | | other microorganisms in wastewater stabilization |
| retained for a sufficient time to satisfy the | | | | ponds like protozoa, rotifers etc., also live in these |
| biochemical oxygen demand (BOD), and thereby | | | | waters and feed on algae and bacteria. |
| make the sewage non-putrescible. The purifying | | | | Because of the shallow depth, generally less than 2 |
| action in an oxidation pond can be explained because | | | | m, the oxidation ponds act as facultative ponds in |
| of a unique relationship between bacteria and algae in | | | | which both aerobic as well anaerobic biochemical |
| shallow ponds. The bacteria metabolize organic | | | | reactions take place. As the raw sewage without |
| matter releasing nutrients like nitrogen, phosphorous | | | | primary treatment enters the waste stabilization |
| and carbon dioxide. | | | | pond, the organic solids settle to the bottom and |
| Algae use these compounds along with energy from | | | | decompose anaerobically forming a sludge zone at |
| sunlight for synthesis of food releasing oxygen in | | | | the bottom and producing intermediate products. The |
| wastewater. Bacteria take up oxygen released by | | | | latter are acted upon by facultative and aerobic |
| algae, thus closing the cycle. This type of relationship | | | | bacteria, and in the process converted into stabilized |
| between bacteria and algae is called symbiosis. This is | | | | nutrient form. Oxygen is added to the wastewater in |
| common among organisms living in small ponds and | | | | the pond by wind action at the surface and from |
| streams, where two or more species live together | | | | daylight metabolism of algae. |