Which of the following is/are products of wastewater treatment? (a) Biogas (b) Sludge (c) Both biogas and sludge (d) Aerator

Soln:

The answer is (c) Both biogas and sludge

Explanation:

During wastewater, treatment water is allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.