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Each point: 1 Mark.
The better housekeeping practices are as follows:-
1. Cooking oils and fats should not be thrown down the drain. They can harden and block the pipes.
2. Chemicals like paints, solvents, insecticides, motor oil and medicines may kill microbes that help purify water. So, efforts should be made to ensure that they are not disposed into the drain.
3. Used tea leaves, solid food remains, soft toys, cotton, sanitary towels etc should only be thrown into the dustbin.These solid food wastes chokethe drain and do not allow the free flow of oxygen, thus hampering the degradation process.

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Each point: 0.5 Mark
The various contaminants present in wastewater are:
i) Organic impurities: Human faeces, oils, animal wastes.
ii) Inorganic: Nitrates, phosphates, metals.
iii) Heavy metals: Mercury, lead.
iv) Microorganisms: Bacteria, viruses.

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Explanation: 2 Marks
Example: 1 Mark
Untreated human excreta is a health hazard. It may cause water pollution and soil pollution. Both the surface and groundwater get polluted.
Groundwater is a source of water for wells, tube wells, springs, and many rivers. Thus it becomes the most common route for waterborne diseases.
Poor sanitation and contaminated drinking water is the cause of a large number of diseases.
They include cholera, typhoid, polio, meningitis, hepatitis, and dysentery.

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Naming: 1 Mark each
Organic impurities in sewage include:
1) Human faeces
2) Herbicides
3) Fruitand vegetable wastes

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Sewage: 1 Mark
Contaminants: 1 Mark
Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients and other disease-causing bacteria and microbes.
The impurities present in sewage are called contaminants.

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Definition: 1 Mark
Each Disinfectant: 0.5 Marks
When wastewater is allowed to settle in a large tank, solids like faecessettle at the bottom of the tank. The solid waste at the bottom of the tank is known as sludge.
Two chemicals that are used to disinfect water are:

• Ozone


• Chlorine

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Wastewater is anywaterthat has been adversely affected in quality byexternalinfluence. Wastewater can originate from a combination of domestic, industrial, commercial oragriculturalactivities, surface runoff and fromsewerinflow or infiltration.

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Chlorination: 1 Mark
Sources: 2 Marks
Chlorine is used in wastewater treatment to disinfect the water.
The various sources from which wastewater is produced are:

• Homes: Water used in washing, cleaning, bathing, cooking etc.


• Industries: Water used in washing raw materials, cleaning machines, coolants.


• Agricultural fields:Water used for irrigation washes off chemical fertilizers, insecticides, etc.


• Other human activities: Water used for water sports, festivals etc.

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Correct matching: 0.5 marks each
$\begin{array}{cc}a)Cleaningofwaterisaprocessof& ii)removingpollutants\\ b)Wastewaterreleasedbyhousesiscalled& v)sewage\\ c)Driedsludgeisusedas& iv)manure\\ d)Drainsgetblockedby& vi)cookingoilsandfats\\ e)Wastewateristreatedin& i)sewagetreatmentplant\\ f)Septictanks,chemicaltoilets,compostingpitsareexamplesof& iii)lowcostdisposalsystems\end{array}$

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Vermi-processing toilet: 4 Marks
Reason: 1 Mark
Vermirefers to small worms such as earthworms. Vermi-processing toilets are those toilets in which humans excreta is treated by earthworms. It has been found to be a novel, low water-use toilet for safe processing of humanexcreta without odour and fly problem.The operation of the toilet is very simple and hygienic. The human excreta is completely converted to vermi cakes -a resource much needed for enhancing the fertility of the soil.
We should not throw chemicals like paints, solvents, insecticides, motor oil, medicines down thedrain as they may kill microbes that help purify water. It also leads to pollution of groundwater and may adversely affect the health of organisms.