Sewage treatment: chemical and biological process

Sewage treatment is the process of removing contaminants from wastewater and household sewage, both runoff (effluents), domestic, commercial and institutional
The objective of sewage treatment is to produce a disposable effluent without causing harm to the surrounding environment and prevent pollution

Origins of sewage

Sewage is generated by residential, institutional, commercial and industrial establishments
It includes household waste liquid from toilets, baths, showers, kitchens, sinks and so forth that is disposed of via sewers
In many areas, sewage also includes liquid waste from industry and commerce
The separation and draining of household waste into grey water and black water is becoming more common in the developed world, with grey water being permitted to be used for watering plants or recycled for flushing toilets

Sewage may include storm water runoff

Grey water & Black water

Grey water is wastewater generate from domestic activities such as laundry, dishwashing, and bathing, which can be recycled on-site for uses such as landscape irrigation and constructed wetlands whereas
Black water is wastewater containing fecal matter and urine