In the purification of portable water, the coagulant used is?

Explanation

Alum, or aluminum sulfate, is commonly used as a coagulant in the purification of portable water. When added to water, alum forms a gelatinous precipitate called floc, which traps impurities such as suspended particles, dirt, and microorganisms. These impurities settle to the bottom of the water, allowing for easier removal during the filtration process. Therefore, option (a) is correct. Now we'll look at why other options are incorrect.(b) BOD (Biochemical Oxygen Demand): BOD is not a coagulant used in the purification of portable water. Instead, BOD is a measure of the amount of dissolved oxygen consumed by microorganisms during the decomposition of organic matter in water. It is used as an indicator of water quality and pollution levels but is not directly involved in the purification process. Therefore, option (b) is incorrect.(c) COD (Chemical Oxygen Demand): Similar to BOD, COD is not a coagulant used in the purification of portable water. COD is a measure of the amount of oxygen required to oxidize organic and inorganic compounds in water. It is also used as an indicator of water quality and pollution levels but does not play a role in water purification. Therefore, option (c) is incorrect.(d) All of the above: This option is incorrect because only option (a) (alum) is the correct coagulant used in the purification of portable water. Options (b) and (c) (BOD and COD) are not coagulants and are not directly involved in the purification process.(Environmental chemistry,Solid Waste Management and Water Treatment)