Which of the following is/are products of wastewater treatment?

1. Biogas
2. Sludge
3. Both biogas and sludge
4. Aerator

Correct Answer: (c) Both biogas and sludge

Explanation: The sewage is treated to destroy the germs and reduce the contaminants. In wastewater treatment, wastewater is passed through a sedimentation tank, in which organic materials settle down and are removed with scraper. This is called sludge.

In separate tank, sludge is acted upon by anaerobic bacteria which produces methane, carbon dioxide, and biogas by process known as digestion. Therefore, both sludge and biogas are products of wastewater treatment.