The procedure for removing contaminants from the wastewater basically from the household sewage is called sewage treatment. It has to undergo the chemical, physical and biological procedure to remove these contaminants and give out an environmentally safe treated effluent. A semi-solid slurry called the sewage sludge is the by-product of the sewage treatment. This sludge is further processed before it is suitable for land application.
Sewage treatment is also called as wastewater treatment, i.e. it also includes treatment of wastewater from industries. In many cities, the sewer carries a proportion of industrial wastewater to the sewage water treatment plant which has already undergone a treatment in the factories for reducing the pollutant. If it is a combined sewer it will also carry storm water along with it.
