A. Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers
B. 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river
C. Solubility of oxygen in sewage is 95% of that of distilled water
D. All the above
Correct Answer: All the above ✔
Last Updated: August 25, 2020