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Description: 1 Mark
Reason for making: 2 Marks
A manhole is a covered vertical hole in the ground, pavement or road above the underground sewer pipeline.
These are made so that if there is any leakage or blockage in the underground sewer pipeline, the sanitary worker can go down or up to these sewer pipelines for cleaning or any repair.

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a) 2 Marks
b) 3 Marks
a) It has been suggested that we should plant eucalyptus trees all along sewage ponds because these trees absorb wastewater rapidly and release pure water vapour into the atmosphere.
b)Septic tanks are suitable for places such as hospitals, isolated buildings, and clusters of houses where there is no sewage. Local governments or private corporations usually provide septic tanks in areas that have no direct connection to main sewage pipes. The septic tank system consists of a small sewage treatment system.
Aeroplanes and trains usually have chemical toilets. A chemical toilet uses chemicals to disinfect human waste and remove its bad odour. That is why trains and aeroplanes do not have elaborate plumbs and sewage.

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Sewerage: 1 Mark
Inorganic impurities: 0.5 Mark each
Sewerage is like a transport system(consisting of pipes) that carries the sewage from the point of being produced to the point ofdisposal, i.e. wastewater treatment plant.
Various kinds of inorganic impurities present in wastewater are:
i) Nitrates
ii) Phosphates
iii) Metals
iv) Sulphates

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A setup that treats or purifies wastewater is waste-water treatment plant.Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical and biological matter that contaminates water.

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Each point: 1 Mark
The wastewater generation can be minimized by the following ways:
1: Waste water accumulated in the kitchen can be used to water plants around the area.
2: Chemicals like paints, solvents, insecticides, motor oil, and medicines may kill microbes that help to purify water. So, do not throw them down the drain. They might also block the drain pipes
3: Used tea-leaves, solid food remains, soft toys, cotton, sanitary towels, etc, should also be thrown in the dustbin. These wastes choke the drain and they do not allow free flow of oxygen.This hampers the degradation process.

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Classification: 1 Mark each
(i) Sullage Water: This is referred to the waste water that comes from kitchen sinks.
(ii) Foul waste: This refers to the waste water that is released from lavatories and toilets of both domestic and commercial establishments.
(iii) Trade waste: It is theliquidwastegenerated oncommercial premises and discharged to our sewerage system.

Answer: Option A. -> True
:
A
Untreated human excreta is a health hazard because this results in poor sanitation. A very large fraction of people defecate in the open, on railway tracks or directly into water. It causes water and soil pollution. This can lead to a lot of water borne diseases such as typhoid and cholera.

Answer: Option B. -> It helps in removing suspended solids.
:
B

Sewage has different kinds of impurities such as suspended solids, oil, organic and inorganic impurities. 
A skimmer is a type of machine which helps in separating liquids(oil) or suspended particles from another liquid. It is usually used to separate oil and suspended solids from water in a wastewater treatment plant.

Answer: Option B. -> Cholera
:
B

Water-borne diseases are any illness caused by drinking contaminated water. Cholera and typhoid are water borne diseases.
Cholera is an infectious and fatal bacterial disease of the small intestine. It is generally acquired from infected water supplies and causes severe vomiting and diarrhea.
Smallpox, chicken pox, fever are not water borne diseases.

Answer: Option B. -> Eucalyptus tree
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B

Eucalyptus trees are suggested to be grown near sewage ponds as eucalyptus trees absorb all surplus waste water rapidly and release pure water vapour into the atmosphere.