This is the correct option. Nitrogen is a waste from nutrients.

The statement. micro-organisms decompose the inorganic matter present in the sewage, is  false. Micro-organisms decompose the organic matter present in the sewage.

This is the correct option, as excessive rainfall is not a reason responsible for the scarcity of fresh water. Rather, excessive rainfall is good as it increases the supply of fresh water.

This is the correct option. Malaria is not a water related disease. It is caused due to a bite by an infected mosquito.

This is the correct option. March 22 is celebrated as World Water Day.

Treatment of liquid with chlorine to kill disease causing organisms, is not a step involved in the primary treatment stage of sewage. The liquid is treated with chlorine at the last stage, which is called tertiary treatment.

This is the correct option, as phosphates are an inorganic waste. Inorganic wastes are chemical substances of mineral origin.

This is the correct option, as this is not an organic waste. It is an inorganic waste.

This is the correct option, as medical waste from hospitals in the form of syringes, bottles, cotton swabs etc is not the component of the sewage.

During the third stage of treatment of sewage, disinfection of water is done by using calcium, is a false statement. Thus, it is a correct option. During the third stage of treatment of sewage, disinfection of water is done by using ozone or chlorine.

This is the correct option. Waste Water Treatment Plant is the full form of WWTP.

This is the correct option. Eucalyptus trees should be planted along sewage ponds as they absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere.

This is the correct option, as discharging sewage directly into rivers will increase water pollution.

This is the correct option. A septic tank is an underground  place, in which sewage is collected and allowed to decompose through bacterial activity before draining by means of a soakaway. A sedimentation tank is a place into which sewage is passed to allow suspended solid matter to separate out. An aeration tank is a place where a liquid is held to increase the amount of air in it.

This is the correct option. Contaminants are the dissolved and suspended impurities in sewage. Sludge is the solid matter that settles at the bottom in the sedimentation tank. Biogas is the gaseous fuel produced by the fermentation of organic matter.