According to the CWA, what is the maximum limit for total suspended solids in effluent after secondary treatment?

The maximum limit for total suspended solids (TSS) in effluent after secondary treatment, as specified by the Clean Water Act (CWA), is set at 30 mg/L. This value is established to ensure that treated wastewater is sufficiently processed before being discharged into the environment, thereby minimizing potential pollutants that could affect water quality and aquatic ecosystems.

Secondary treatment is designed to remove biodegradable organic matter and suspended solids, which play a critical role in protecting water bodies from deterioration due to pollution. The 30 mg/L limit reflects a balance between achieving effective treatment and allowing for reasonable operational feasibility in wastewater treatment facilities.

In contrast, the other values listed—20 mg/L, 50 mg/L, and 100 mg/L—are not compliant with the current regulations under the CWA regarding secondary treatment effluent standards. Values higher than 30 mg/L may indicate insufficient treatment which can pose risks to environmental health due to excess solids in the released wastewater. Similarly, a standard lower than 30 mg/L like 20 mg/L, while potentially beneficial, is not the established limit defined by the regulations.