Conventional pollutants fall into five categories; the presence of these pollutants is commonly determined by measuring biochemical oxygen demand, total suspended solids, pH levels, the amount of fecal coliform, and the quantity of oil and grease.

Biochemical oxygen demand (BOD) is the quantity of oxygen required by microorganisms to stabilize five-day incubated oxidizable organic matter at 68°F (20°C). Hence, BOD is a measure of the biodegradable organic carbon and at times, the oxidizable nitrogen. BOD is the sum of the oxygen used in organic matter synthesis and in the endogenous respiration of microbial cells. Some industrial wastes are difficult to oxidize, and bacterial seed is necessary. In certain cases, an increase in BOD is observed with an increase in dilution. It is hence necessary to determine the detection limits for BOD.

Suspended solids interfere with the transmission of light. Their presence also affects recreational use and...