Question 1

Fill in the blanks:

(a) Cleaning of water is a process of removing .
(b) Wastewater released by houses is called .
(c) Dried is used as manure.
(d) Drains get blocked by and .

Answer

(a) Contaminants
Cleaning of water is a process of eliminating pollutants before it enters a water or aquatic body or is reused. This wastewater treatment process is commonly known as sewage treatment. It takes place in various stages.

(b) Sewage
Sewage is a waste. Most of the dirty water having dissolved and suspended impurities or contaminants in it. The impurities present in sewage are known as contaminants or pollutants.

(c) Dung
Cow dung, which is dark brown in colour is mainly used as manure. If the dung is not recycled into the soil by species like earthworms and dung beetles, cow dung can dry out remain on the pasture, creating an area of grazing land which is unpalatable to animals.

(d) Plastic and sludge
The waste water is passed into a sedimentation tank and allowed to stand there for a while. Most of the solid organic matter settles down on the bottom of the slope of sedimentation tank in the form of a sludge; the solid part of sewage is called sludge.