Question

What would happen if a large volume of untreated sewage is discharged into a river?

Answer 1

Human health and the environment are suffering mainly from the direct disposal of commercial and human waste in natural resources without being treated. Sewage treatment is important to cut down the toxicity of sewage. BOD is an accurate measurement of the amount of oxygen that is needed to remove the waste organic matter.

Complete Answer:
Sewage contains a huge amount of organic matter that is highly toxic.
Microorganisms are usually used for removing toxic organic matter. If the untreated sewage is disposed-off directly into the water bodies, it will lead to major pollution of water. The pollutants are mainly organic matter and microorganisms that can cause diseases. If this water is used for human consumption, it can lead to water borne diseases. The pollutants will also change the pH level of the water causing harm to aquatic life (both plants and animals). It also has a potential to contaminate groundwater.
BOD stands for biological oxygen demand. Untreated sewage being released into rivers results in increased biological oxygen demand. BOD is an indication of the amount of organic pollution that is present in an aquatic ecosystem. BOD can also be used to measure the chemical oxidation (COD) of inorganic matter. It is also used in sewage treatment to completely destroy and decay organic wastes with the help of aerobic organisms.

Notes:
Biological oxygen demand has other significant applications outside of determining the polluting potential of water. It can be used to determine the rate of respiration in living beings. BOD is also used in the medical and pharmaceutical industries to determine the oxygen consumption of cell cultures.