(a) Cleaning of water is a process of removing pollutants. (b) Wastewater released by houses is called sewage. (c) Dried sludge is used as manure. (d) Drains get blocked by garbage and chemicals.
Q2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
Ans:
Sewage is wastewater released by homes, industries, hospitals, offices & other users.
It includes rainwater run down the street during a storm or heavy rains.
It contains many dissolved & suspended impurities, chemicals, disease causing bacteria & other microbes which cause water & soil pollution.
Hence, if this untreated sweage is discharged into rivers or seas, it can contaminate the water and spread a lot of diseases or destroy ecosystems in rivers and seas.
Q3. Why should oils and fats not be released in the drain? Explain.
Ans:
Cooking oil & fats should not be thrown down the drain as they harden and block the pipes.
In an open drain the fats clog the soil pores which reduces the water filtering capacity of the soil.
Q4. Describe the steps involved in getting clarified water from wastewater.
Ans:
Large objects like rags, sticks, cans, plastic packets, napkins are removed by passing wastewater through bar screens.
Water then goes to a grit & sand removal tank to remove sand, grit and pebbles through sedimentation.
Solid impurities & feaces called sludge are collected from bottom of water. A skimmer removes the floatable solids like oil & grease.
An areator cleans this clarified water.
Sometimes water may be disinfected with chemicals like chlorine & ozone.
Q5. What is sludge? Explain how it is treated.
Ans:
Sludge is the solid waste & impurities collected from the wastewater during the treatment in a wastewater treatment plant.
Sludge is decomposed in a separate tank by the anaerobic bacteria.
Activated sludge has 97% water which is removed & dried sludge is used as manure.
Q6. Untreated human excreta is a health hazard. Explain.
Ans:
Untreated human excreta causes water & soil pollution.
The surface & ground water gets polluted.
This causes water borne diseases like cholera, typhoid, polio, meningitis, hepatitis & dysentery.
Q7. Name two chemicals used to disinfect water.
Ans:
Two chemicals used to disinfect water are chlorine & ozone.
Q8. Explain the function of bar screens in a wastewater treatment plant.
Ans:
Bar screens remove large objects like rags, sticks, cans, plastic packets, napkins from the wastewater.
Q9. Explain the relationship between sanitation and disease.
Ans:
Sanitation and disease are related to each other.
Due to poor sanitation, a large number of diseases are caused.
Q10. Outline your role as an active citizen in relation to sanitation.
Ans:
As active citizens we should keep our surroundings clean by disposing of waste properly & using dustbins.
Educate others & share knowledge about sanitation & hygiene.
Participate in community clean-ups by joining local efforts to clean public spaces.
We should help municipal corporations to cover all the open drains and remove disease causing substances thrown in open.
(a) It is essential for breathing of living organisms. (b) It is used to disinfect water. (c) It absorbs ultraviolet rays. (d) Its proportion in air is about 3%.
