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.
