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 ofmachine whichhelps in separatingliquids(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 A. -> Poor sanitation and contaminated drinking water is the cause for a large number of diseases.
:
A
There is a direct relationship between sanitation and diseases. Poor sanitation and contaminated drinking water are the cause of a large number of diseases. Under poor sanitation, people may resort to defecating in the open, near fields or directly in the water. Itcauses water and soil pollution. The surface and groundwater, both get polluted and becomes the most common carriers of water-borne diseases.

:
Each point: 1 Mark
All of us can contribute in maintaining sanitation at public places.
(i) We should notlitter anywhere.If there is no dustbin in sight, we should carry the litter home and throw it in the dustbin.
(ii) We should avoid throwing wastes in nearby water bodies, which can contaminate them.
(iii) We should not defecate in the open. It is possible to have safe disposal of excreta by low cost methods.

:
Each step:1 Mark
1) We should notscatter litter anywhere.
2) Prevent clogging of drains by not releasing solid wastes in them.
3)If there is no dustbin in sight, we should carry the litter home and throw it in the dustbin.
4)We should help municipal corporations to cover all the open drains and remove disease-causing substances thrown in open.
5) We should make sure that the sewerage system in our house is properly managed.

:
Machine usage: 1 Mark
Impact: 2 Marks
A bar screen machine in a wastewater treatment plant is an essential equipment as it helps to remove large objects floating in the water like rags, sticks, cans, bottles, plastic packets and even sanitary napkins. This machine plays an important role in separating suspended aggregates from wastewater before commencing the treatment of water.
The people of Itarsi will be impacted by all these floating debris in their water feed if they are not separated right at the outset. Further, bottles, rags, sanitary napkins become the breeding zone of many undesirable bacteria and pathogens.

:
Steps: 0.5 Mark each
Steps involved in getting clarified water from wastewater are:
1. Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed.
2. Water then goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.
3. The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water.
4. Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water. Chemicals like chlorine is added to disinfect the clarified water, before releasing it into distribution systems.

Answer: Option C. -> pollutants
:
C
Sewage is a complex mixture containing suspended solids, organic and inorganic impurities.
These pollutants are removed using physical, chemical, biological processes in a wastewater treatment plant before they are released into a water body.

Answer: Option A. -> Sewerage
:
A
Sewerage is like a transportation system that carries sewage from the point of production i.e. households, industries, hospitals, to the point of disposal i.e. wastewater treatment plant.
These systems have manholes located at fixed frequency. It is necessary to have a sewerage system without which we may be exposed to various air-borne diseases.

Answer: Option D. -> Hampers health as the water is impure
:
D
Our day to day actions that need serious contemplationis often ignored. Be it dumping the waste and construction debris on road or pushing the road sweeping into the nearby drain, every incoherent action leads to worsening of the state of the drainage system. If the drain slabs are not repaired on time, leaving convenient openings for pushing garbage and trash matter inside the drain. The open drains are treated as garbage store, which when are completely filled up, fail to carry any storm flow and contribute to water-logging and flooding. To aggravate the situation these flooded or waterlogged areas serve as the abode for vectors that spread diseases like malaria, filarial or dengue.

Answer: Option C. -> Wastewater from homes is fit for consumption.
:
C
The wastewater includeshuman waste, food scraps and chemicals. Sewageis a type of wastewater that comprises of domestic wastewater. It can contain food waste, waste from toilets, etc. and hence, is unfit for consumption. Wastewater from industries can contain chemicals and toxic wastes.