Answer: Option A. -> True
:
A
Cooking oiland fats get hardened and therefore can blockpipes. In open drains,the fats clog the soil pores which reducesits effectiveness in filtering water.

Answer: Option D. -> It is used to disinfect water and absorb ultraviolet rays
:
D
Ozone is used to disinfect water and it also absorbs ultraviolet rays. Other uses of ozone are as follows:
1. Kills bacteriaeffectively.
2. Oxidises substancessuch as iron and sulphur so that they can be filtered out of thesolution.
3. There are no nastyodours or residues produced from the treatment.
4. Ozone converts backinto oxygen quickly and leaves no trace once it has been used.

Answer: Option B. -> False
:
B
Sewage is a complex mixture which contains various organic and inorganic impurities. They need to be removed before they are discharged into water bodies. If they are directly discharged into the water bodies it will harm the aquatic life as well as the human population.

Answer: Option B. -> Sewerage
:
B
Sewerage is a network of big and small pipes called sewers that transport sewage from the point of being produced, such as, households, industries to the point of point of disposal i.,e., the treatment plants.
Sewage contains suspended solids, organic and inorganic impurities. Sluge is a by-product produced in wastewater treatment.

Answer: Option C. -> tea leaves can harden and block the pipes.
:
C
The used tea leaves or solid food remains should not be thrown down into the drain as they can harden and block the pipes of the drain. Thus, the wastes choke the drains and do not allow free flow of oxygen. This in turn hampers the degradation process.
Therefore, used tea leaves should always be thrown in the dustbin.

Answer: Option B. -> Septic tanks
:
B
Septic tanks are suitable for places, such as hospitals, isolated buildings or a cluster of 4-5 houses, where there is no sewerage system. A septic tank isa tank, that is typically underground, in which sewage is collected and allowed to decompose through bacterial activity before draining by means of a leaching field.

Answer: Option B. -> False
:
B
Water contains some microbes which degrade organic matter present in them and helps in purifying the wastewater. Chemicals like paints, insecticides kill the microbes present in water. Also, the toxic chemicals present in them cause water pollution. Hence, they should not be thrown down the drain.

Answer: Option A. -> nitrogen
:
A
Sewage contains harmful nutrients such as phosphorus and nitrogen.
Too much nitrogen and phosphorus in water causes algae to grow faster. Significant increase in algae will lead to decrease in oxygen which is required by other aquatic animals.
Hence, excess of nutrients in sewage is harmful.

:
Each arrangement: 0.5 Mark
Onsite human waste technology: 1.5 Marks
The various alternative arrangements for sewage disposal are:
i) Septic Tanks
ii) Chemical Tanks
iii) Composting Tanks
In case of on-site human waste technology, thetoilets do not require scavenging. Excreta from the toilet seats flow through covered drains into a biogas plant. The biogas produced is used as a source of energy.
So, on-site human waste technology has a two-fold advantage:
i) It disposes off the wastes.
ii) The biogas produced from these can be used as an alternative source of energy.

:
Each point: 1 Mark
i)Many cities have large and growing population resulting in greater demand for water resources. A large population means, not only more water is required for domestic use but also for higher foodgrain productivity.
ii) Today the multinational companies and other industrial units consume large quantities of hydroelectric power and for the processing of which they put greater pressure on the existing freshwater resources.
iii) Pollution of water bodies due to the discharge of industrial effluents, use of pesticides, insecticides, and fertilizers used in agriculture, make the river water hazardous for human consumption.
iv)Inefficient use of water for agriculture is another reason for scarcity of freshwater.Traditional techniques of irrigation cause maximum water loss due to evaporation, drainage, percolation, water conveyance, and excess use of groundwater.
v)Reduction in traditional water recharging areas. Rapid construction is ignoring traditional water bodies that have also acted as groundwater recharging mechanism.