Class 7 - Biology - Wastewater Story
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 ____________.
(a) Cleaning of water is a process of removing pollutant.
(b) Wastewater released by houses is called sewage.
(c) Dried sludge is used as manure.
(d) Drains get blocked by oils and fats.
What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
Sewage is a liquid waste which has water as its largest component along with various types of impurities like waste water from houses, offices, factories, hospitals etc., is called sewage.
It has a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes.
Discharging untreated sewage into rivers or seas will pollute the water resources.
Contaminated water is dangerous for aquatic plants and animals. It also spread many diseases like cholera, typhoid, polio, meningitis, malaria, dengue etc.
Why should oils and fats be not released in the drain? Explain.
Oil and fats can clog the drains reducing its effectiveness in filtering water. In open drains, they block the pores in the soil and thus hamper the filtration by soil.
Hence, oil and fats should not be released into the drain.
Describe the steps involved in getting clarified water from wastewater.
Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical and biological matter that contaminates the wastewater.
Following steps are involved:
What is sludge? Explain how it is treated.
Sludge is human waste (like faeces) in waste water left during sewage treatment. Since it is organic waste, it is used to produce bio gas and manure.
Sludge is collected by a scrapper. It is transferred to a separate tank where it is decomposed by the anaerobic bacteria.
The biogas produced in the process can be used as fuel. After the aerator tank, microbes and human waste settle down and form activated sludge.
The activated sludge is about 97% water. The water is removed by sand drying beds or machines. Dried sludge is used as manure, returning organic matter and nutrients to the soil.
Untreated human excreta are a health hazard. Explain.
Untreated human excreta contain many pathogens and disease causing microbe like cholera, diarrhea, typhoid, polio, meningitis, hepatitis etc.
The germs of these diseases can easily reach human population through air, water or insects and through contaminated food and water. Thus, untreated human excreta are a health hazard.
Name two chemicals used to disinfect water.
Chemicals like chlorine (Chlorine dioxide) and ozone (in the pharmaceutical industry) are commonly used to disinfect water.
Explain the function of bar screens in a wastewater treatment plant.
Bar screens are used to remove large objects like rags, sticks, cans, plastic packets napkins, etc. in wastewater treatment plant.
Explain the relationship between sanitation and disease.
A large number of diseases is caused due to poor sanitation and contaminated drinking water.
Poor sanitation leads to growth of harmful microbes, flies and mosquitoes which are the source of spreading many diseases like cholera, typhoid, polio, meningitis, hepatitis and dysentery.
So, its better to have a good sanitation and proper hygiene.
Outline your role as an active citizen in relation to sanitation.
Wastewater treatment plant requires costly infrastructure to build and to be maintained. So, we should be an active citizen and limit the type of waste. Try to follow the following:
Study the following statements about ozone:
(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%.
Which of these statements are correct? (i) (a), (b) and (c) (ii) (b) and (c) (iii) (a) and (d) (iv) All four.
(ii) (b) and (c).
Ozone is used to disinfect water and absorbs ultraviolet rays.