Which factors are assessed by POTWs for surcharges on industrial discharges?

The assessment of surcharges on industrial discharges by Publicly Owned Treatment Works (POTWs) primarily focuses on parameters that indicate the strength and characteristics of wastewater. The correct answer, which includes Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Flow, and Suspended Solids (SS), is critical because each of these factors provides insights into the potential impact on the treatment process and the receiving environment.

BOD measures the amount of oxygen that microorganisms will consume while decomposing organic matter in the water. COD assesses the total quantity of oxygen required to chemically oxidize both biodegradable and non-biodegradable substances. The flow rate indicates the volume of wastewater entering the treatment facility, which can heavily influence treatment efficiency and operation. Suspended solids represent particulate matter that can clog treatment processes and affect the clarity of the effluent. By monitoring these parameters, POTWs can determine the level of treatment required and the associated costs, leading to appropriate surcharges for industrial users whose discharges exceed established thresholds.

In contrast, the other options focus on factors that, while relevant to water quality, do not directly correlate to surcharge calculations in the same fundamental way. Heavy metals and factors like microbial content and biological activity may certainly be monitored for compliance and environmental