What factor influences the increase in dilution of wastewater during rain events?

The increase in dilution of wastewater during rain events is primarily influenced by inflow and infiltration into the system. Rainfall can lead to excess water entering the wastewater collection systems through various means, such as leaks in sewer pipes, poorly sealed joints, or direct connections from stormwater systems. This additional water dilutes the concentration of contaminants in the wastewater because the overall volume of water increases while the amount of pollutants may not increase proportionally.

This phenomenon is significant in determining how wastewater treatment plants manage their operations during wet weather. Facilities may need to handle larger volumes of diluted wastewater, which can impact treatment processes and effectiveness.

Other factors mentioned, like enhanced treatment capacity, decrease in industrial activity, and improved chemical treatments, do not directly address the mechanism by which rain increases the volume and dilution of wastewater in the system. Enhanced treatment capacity might help in processing larger volumes, but it doesn't describe the cause of dilution. A decrease in industrial activity might reduce pollutant loads but does not relate to the direct impact of rainfall. Similarly, improved chemical treatments can enhance treatment effectiveness, but they are not a factor in the dilution caused by rain.