Wastewater treatment plants often don't effectively remove harmful mutagens from industrial wastewater. While physico-chemical parameters like BOD and COD are commonly used to monitor treatment efficiency, biological parameters are not. A study found that a sewage treatment plant successfully treated wastewater based on physico-chemical measures, but failed to remove genotoxicants. This means that the treated wastewater may still contain harmful compounds that can harm aquatic life in natural water bodies.