NCERT Class 7 Science Chapter 18: Wastewater Story YouTube Lecture Handouts
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NCERT Class 7 Science Chapter 18: Wastewater Story (NSO/NSTSE)
Brain Teasers
- What are organic and inorganic impurities?
- Differentiate Sewer and Sewerage.
Sources of Wastewater
Cleaning Wastewater
- DonΥt waste water
- Remove pollutants
- 1 billion people donΥt have safe drinking water
- 22 March β World Water Day
- 2005 - 2015 β Water for Life
- Sewage Treatment
Sewage
Waste water from homes, industries, hospitals and offices
Dissolved and Suspended Impurities
Sewer β Network of pipes (from production to disposal) ; Manholes located 50 to 60 m
Organic impurities β Human faeces, animal waste, oil, urea (urine) , pesticides, herbicides, fruit and vegetable waste, etc.
Inorganic impurities β Nitrates, Phosphates, metals.
Nutrients β Phosphorus and Nitrogen.
Bacteria β Such as vibriocholera which causes cholera and salmonella paratyphi which causes typhoid.
Other microbes β Such as protozoans which cause dysentery.
Treatment of Water
- Before treatment
- After aeration
- Chlorination
- Sedimentation
Waste Water Treatment Plant
Bar Screens for large plastics and cans:-
Grit and Sand Removal β reduce speed
- Solid feces settle on bottom and is removed by scraper β sludge
- Skimmer removes floatable impurities
- Clear water is clarified water β biogas
- Aerator - Air is pumped for aerobic growth; Bacteria consume waste
- Activated Sludge β microbe settle on bottom and is 97% water
- Dried sludge is used as manure, returning organic matter & nutrients to the soil.
Cover Open Drains
Plant Eucalyptus to absorb surplus waste water & release pure water
Cholera, Typhoid, Polio
Meningitis, Hepatitis and Dysentery
Cooking oil harden and block pipes
Chemicals like paints, solvents, insecticides, motor oil, medicines may kill microbes that help purify water. So do not throw them down the drain
Solid waste choke drains
Swachh Bharat Abhiyan
Vermi-processing toilet: A design of a toilet in which humans excreta is treated by earthworms has been tested in India. It has been found to be a novel, low water-use toilet for safe
processing of human waste
Alternate Arrangements
To improve sanitation, low cost onsite sewage disposal systems are being encouraged. Examples are septic tanks, chemical toilets, composting pits.
Septic tanks are suitable for places where there is no sewerage system, for hospitals, isolated buildings or a cluster of 4 to 5 houses
By-products of wastewater treatment are sludge and biogas.
Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.
We should not defecate in the open
β Mayank