Three Stages to Remove Contaminants from The Sewage

Sewage is the liquid waste produced by humans which typically contains washing water, faeces, urine, and other liquid or semi-liquid wastes from household and industry. It is one type of waste water.
In order to discharge the sewage to the environment, there is need to be a sewage treatment. Sewage treatment is the process of removing the contaminants from the waste water. It's objective is to produce a waste stream and a solid waste or sludge, which are suitable for discharge and reuse back into environment.
Sewage treatment involves three stages, called primary, secondary, tertiary treatment. First, in the primary stage, sewage from the main sewer is flowed to the settling tank. In the settling tank, polluted water is separated from it's contaminants. These contaminants will be dissolved and become a sediment on the bottom of the settling tank. This sediment is an undecayed solids, so it must be removed and burned.
After that, in the secondary stage, the polluted water is distributed to the pump house. In the pump house, polluted water is pump to reach the sprinkler beds, which is located higher than the sprinkler beds.
In the tertiary treatment stage, polluted water are filtered in the sprinkler beds. Polluted water, which has reached rotating arms beneath the sprinkler beds, will be sprayed to the sprinkler beds. The sprinkler beds is designed with layer, so the polluted water can be filtered. This filtering process will remove stones and micro-organisms from the polluted water. Water, which is came out from the sprinkler beds, is not polluted and hazardous anymore. Therefore, it can be discharged to the environment.