Answers to some important questions of class 7 from Water and Wastewater Management

Answers to some important questions of class 7 from Water and Wastewater Management

Chapter: Water

Q 1: Why is groundwater generally pure?

A 1: Groundwater is water found in the spaces between soil particles and cracks in underground rocks.

As groundwater passes through different layers of the soil – humus, top soil and rocks, it gets filtered and thus can be treated as pure or free from general impurities.

Q 2: Heavy rain is good for recharging groundwater. Comment.

A 2: Groundwater recharge is a process where water moves downward from surface water to groundwater. Rains are the natural method to recharge groundwater.

If heavy rain happens only once then it will not recharge groundwater much as water goes through soil slowly (percolation). But, lot of heavy rains over a period of few days can definitely help in passing of water from upper layers to lower portions or rocky layer, a slow process, to store rain water and thus recharge groundwater.

Chapter: Wastewater Management

Q 1: Open drainage system of sewage disposal is health hazard. Explain. Support your answers with suitable examples.

A 1: Open drainage system of sewage disposal is open or uncovered and does not have sanitation which can cause diseases. The less the sanitation, the more the diseases.

Open drainage system of sewage disposal is a health hazard due to following reasons:

- Foul smell causes respiratory diseases and makes it difficult for people to breathe.

-  Refuse and faecal matter in drains quickly becomes bad in smell as it decomposes. It is a suitable medium for flies and mosquitoes for egg-laying and a site for many pathogenic bacteria and viruses to multiply.

Q 2: What is the function of anaerobic and aerobic bacteria in the process of waste water treatment? Explain giving suitable examples.

A 2: In waste water treatment, sludge in the digester tank is allowed to decompose with the help of anaerobic bacteria (bacteria which can survive in the absence of oxygen) to produce biogas, that can be used for the generation of electricity.

Air is pumped into the clarified water or water without solid impurities to help aerobic bacteria to grow. Aerobic bacteria consume human waste, soaps and other unwanted matter still remaining in clarified water.