Q1. What is sludge? Solution Solid faecal matter which is generated after the water treatment plant is known as sludge. Q2. Why it is that cooking oil and fats should not be thrown down the drain? Where should they be thrown? Solution Cooking oil and fats should not be thrown down the drain as it can harden and block the pipes. In an open drain, the fats clog the soil pores reducing its effectiveness in filtering water. We should throw cooking oil and fats in the dustbin. Q3. Which trees should we plant near sewage ponds? Why? Solution We should plant eucalyptus trees all along sewage ponds. These trees absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere. Q4. In waste water treatment plant, discuss the first step of treatment? Solution In the first step, wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed. Q5. During waste water treatment,(a) H...
Q1. Write three damages caused by heavy rains, if the trees are absent. Solution (i) If trees are not present, rain hits the ground directly and may flood the area around it. (ii) Heavy rain may also damages the soil. (iii) Roots of trees normally bind the soil together, but in their absence the soil is washed away or eroded. Q2. How do trees play an important role in regulating the climate? Solution Forests have a key role in regulating the climate, because trees by their photosynthesis absorb carbon dioxide from the atmosphere and store carbon as wood and organic matter in the soil. Q3. Write any three problems encountered if forests disappear. Solution (i) If forests disappear, the amount of carbon dioxide in air will increase, resulting in the increase of earth's average temperature. (ii) In the absence of trees and plants, the animals will not get food, protection and shelter. (iii) In the absence of trees, the soil will not hold water, which will cau...