What is a potential effect of unregulated industrial waste discharged into a municipal wastewater treatment plant?

The correct choice is associated with the potential for an anaerobic digester upset. When unregulated industrial waste is discharged into a municipal wastewater treatment plant, it can introduce toxic substances, high concentrations of organic materials, or other pollutants that the treatment plant is not designed to handle. This can disrupt the microbial populations that are essential for the anaerobic digestion process, leading to an upset in the digester.

An upset in an anaerobic digester may result in decreased biogas production, increased levels of volatile fatty acids, and an overall reduction in the efficiency of the treatment process. This disruption can compromise the treatment facility's ability to effectively process wastewater, potentially leading to environmental issues and violations of discharge permits.

On the other hand, increased oxygen levels, enhanced sludge quality, and improved nutrient removal are generally not outcomes associated with the presence of unregulated industrial waste. These outcomes typically indicate effective treatment processes and healthy plant operations, which would be adversely affected by uncontrolled industrial discharges.