Air Pollution Test - 1

Potable water implies water that is safe to drink or to use for food preparation.

A contaminant is any physical, chemical, biological, or radiological substance or matter in water that makes it impure.
Some drinking water contaminants may be harmful if consumed at certain levels in drinking water, while others may be harmless.
The presence of contaminants does not necessarily indicate that the water poses a health risk.

Urban and suburban areas are non-point sources of pollution because much of the land surface in these areas is covered by buildings, pavement and compacted landscapes. These surfaces do not allow rain and snowmelt to soak into the ground which greatly increases the volume and velocity of stormwater runoff.

Pollutants from urban runoff include: Sediment; Oil, grease and toxic chemicals from motor vehicles; pesticides and nutrients from lawns and gardens; viruses, bacteria and nutrients from pet waste and failing septic systems; and road salts.

Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen required by the aerobic bacteria to break down organic matter present in a given water sample. Higher value is indicative of water pollution.

A water supply with a BOD level of 3-5 ppm is considered moderately clean.

In water with a BOD level of 6-9 ppm, the water is considered somewhat polluted because there is usually organic matter present and bacteria are decomposing this waste.

Ground water contamination may occur due to natural as well as man-made causes.
All of the above mentioned causes are responsible for ground water pollution.

Addition of organic waste to water bodies reduces the amount of oxygen in the water.

This is because the aerobic bacteria utilise the oxygen to decompose the organic matter, thereby creating a shortage because of which the fish and other aquatic animals die of suffocation.

Industrial wastewater is referred to as industrial effluent, which usually contains toxic substances.
Hence, it should be treated before it is released into the water bodies.

Although exposure to agricultural chemicals can occasionally result in direct fish mortality, most fish kills in recreational and farm ponds are the result of oxygen depletion, which may occur due to addition of organic waste to the water.