Madison Water Utility – PFAS Removal Bench-Scale Testing and Feasibility Study

Project Challenges
Madison Water Utility (MWU) is a public water system in Madison, Wisconsin serving more than 250,000 people with a system of 23 deep bedrock wells, 895 miles of water main, and more than 64,000 service connections.

Well 15 was taken out of service due to community concerns about detected per- and polyfluoroalkyl substances (PFAS) from a nearby airport. Prior to shutdown, an air stripping system was used to remove the chlorinated volaile organic compounds (CVOCs) tetrachloroethylene (PCE) and trichloroethylene (TCE).

MWU requested assistance in evaluating treatment technologies, estimating capital and long-term operating costs, and preliminary design information to return Well
15 to a production rate of 1,000 gallons per minute.

TRC Solutions
MWU needed a team with expertise in the treatment of PFAS in water, engineering design and cost estimating, public sector collaboration, and state/local PFAS trends and practices. Therefore, TRC teamed with Evoqua Water Technologies to provide the following services:

Bench-Scale Testing

• A treatability study work plan was developed, and rapid small-scale column tests were completed with two granular activated carbon (GAC) options to evaluate PFAS and CVOC reduction.
• Analytical modeling was conducted to assess ion exchange resin performance (PFAS reduction only).
• Absent a state or federal drinking water standard for PFAS, four different removal goals were evaluated for PFAS. The minimum removal goal for PCE and TCE was >90%.

Treatment Design Recommendations

• A lead-lag GAC vessel system was determined to be a cost-effective way to remove PFAS, PCE, and TCE to target levels and decommission the existing air stripper (saving >$80,000 annually in operation and maintenance).
• An initial cost of $825,000 was estimated for the major treatment system components, which included bag filters to remove suspended solids, carbon vessels and GAC, a backwash tank, and steel piping with a life expectancy of approximately 30 years.
• The estimated annual operating costs of $48,000 to $301,000 would depend on influent concentrations, selected treatment objectives, and the frequency of carbon regeneration and bag filter replacement.

Client Benefits
The feasibility study provides MWU with the information needed to evaluate whether installing a treatment system is the most cost-effective way to meet overall needs and capacity concerns for this area of Madison.