Sewage discharge is the primary cause of water pollution in urban areas, as it contains high levels of organic matter, nutrients, and pathogens.

Biochemical oxygen demand (BOD) is commonly used to assess the level of organic pollution in water, as it measures the amount of oxygen required by microorganisms to decompose organic matter.

The primary purpose of an environmental impact assessment is to identify and assess the potential environmental impacts of a proposed project, including impacts on water quality.

Nitrate is commonly used to assess the level of nutrient pollution in water, as it is a major form of nitrogen that can contribute to eutrophication.

Agricultural runoff is the primary source of nutrient pollution in agricultural areas, as it contains high levels of fertilizers and manure.

Total suspended solids (TSS) is commonly used to assess the level of sediment pollution in water, as it measures the amount of suspended particles in the water.

Stormwater runoff is the primary source of sediment pollution in urban areas, as it carries sediment from impervious surfaces such as roads and rooftops.

E. coli is commonly used to assess the level of microbial pollution in water, as it is a specific indicator of fecal contamination.

Sewage discharge is the primary source of microbial pollution in water, as it contains high levels of pathogens such as bacteria and viruses.

The primary purpose of water quality monitoring is to assess the current state of water quality, including the levels of various water quality parameters.

All of the above water quality parameters are commonly used to assess the level of heavy metal pollution in water, as they are known to be toxic to aquatic life and human health.

Industrial wastewater is the primary source of heavy metal pollution in water, as it often contains high levels of heavy metals from industrial processes.

Total organic carbon (TOC) is commonly used to assess the level of organic chemical pollution in water, as it measures the total amount of organic carbon present in the water.

Industrial wastewater is the primary source of organic chemical pollution in water, as it often contains high levels of organic chemicals from industrial processes.

Trihalomethanes (THMs) are commonly used to assess the level of disinfection byproducts in water, as they are formed when chlorine reacts with organic matter in the water.