Sewage treatment is the process of removing contaminants from wastewater and household sewage, both run off (effluents), domestic, commercial and institutional.

It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants.

Its objective is to produce an environmentally safe fluid waste stream (or treated effluent) and a solid waste (or treated sludge) suitable for disposal or reuse (usually as farm fertilizer). Using advanced technology it is now possible to re-use sewage effluent for drinking water.

Waste treatment processes include energy-intensive operations such as aeration and pumping. As a result, waste water treatment plants (WWTPs) require significant energy consumption.

As electrical prices increase, plant operators are facing higher energy costs in order to meet discharge permit requirements.

The second leading expense to WWTP owners is the cost of energy, behind only personnel.

For plants, who employ anaerobic digestion for biosolids treatment, the process of combusting digester gas to produce electricity and heat through cogeneration/CHP may provide a solution to rising operational costs.

A large proportion of the world’s sewage systems do not recover value from the sewage in the form of electricity and heat. The renewable energy fuel source derived from sewage gas can be converted using reciprocating gas engines, to electricity and heat.The sewage gas electricity and heat can eliminating the need to purchase fossil fuels for plant heating processes.