Evaluation of Water Softening Adjustments for Reduced Chloride Discharge
Minnesota currently has 91 communities that have chloride in their wastewater discharge above the allowable limit in the NPDES permit and will need to take action to reduce chloride. Each wastewater treatment plant (WWTP) receives a unique chloride limit in their permit from the Minnesota Pollution Control Agency (MPCA). And all facilities have a variety of chloride sources, hardness levels of their drinking water sources, as well as their drinking water distribution systems. Many communities are upgrading their centralized water distribution system to reduce hardness at the drinking water treatment plant in order to meet their assigned chloride permit limit. However, several communities are not able to implement that option, so this project will help to inform those cities what options will provide a significant reduction in chloride coming from private water softening systems.
The students will work with the Minnesota Pollution Control Agency to select a community in Minnesota that has been identified to have elevated chloride in their wastewater discharge and evaluate the options and opportunities to optimize, adjust or upgrade home water softening systems to reduce chloride discharged to the WWTP. Then using the best available data and information, calculate the expected reductions for the various water softening adjustment scenarios and determine what options, if any, would reduce chloride enough to allow the WWTP to meet the chloride limit in their permit.