Present standards allow stabilization ponds and trickling filters to have higher 30-day average concentrations (45 mg/L) and 7-day average concentrations (65 mg/L) of BOD/suspended solids performance levels as long as the water quality of the receiving water is not adversely affected. Exceptions are also permitted for combined sewers, certain industrial categories, and less concentrated wastewater from separate sewers.


The Minimum Standards represent the average levels. It is important to understand that these standards are applied to specific bodies of water and are established to meet the particular pollution loads. Rivers mediate more rapidly than standing bodies of water like ponds or lakes. The collective pollution load of all systems contributing to the effluence must be considered in establishing acceptable levels. In the United States, local authorities of the EPA and DER regulate and establish the actual specification for each system releasing effluence into a particular body of water.