For the last entry of Wright-Pierce’s 2025 Calendar Series (which highlights projects featured in our yearly calendar), we close out with the Mill Pond Water Treatment Plant.
Project Overview
The Town of Burlington, MA, Mill Pond Water Treatment Plant treats surface water using a conventional process consisting of chemical feed, rapid mixing, flocculation, sedimentation, and shallow bed sand filtration. The plant, which serves as the Town’s primary water supply, has a maximum treatment capacity of 3.0 millon gallons per day (mgd).
In 2021, per- and polyfluoroalkyl substances, more commonly known as PFAS, were identified in Mill Pond at levels exceeding 50 parts per trillion (ppt), well above regulatory thresholds for drinking water. This required immediate action, and Wright-Pierce was subsequently selected to provide design and construction engineering services for the removal of PFAS at the plant..
A Fast-Tracked Approach
The Town required the new PFAS treatment be designed, constructed, and online within 18 months. A standard timeline for the design and permitting of a PFAS project of this type could take up to two years for two-season pilot testing, design, permitting, regulatory approval, and state revolving fund approvals. Despite the tightened schedule, Wright-Pierce was able to assemble a team and put into place a fast-track plan such that the design for the treatment plant was completed in just under four months.
Within the first six weeks of design, Wright-Pierce conducted warm-weather pilot testing, which served as the basis for the initial design, and bidding for equipment pre-purchase. The PFAS pressure vessel system was designed to accommodate the use of both granular activated carbon (GAC) and ion exchange (IX) media. Rapid small-scale column testing (RSSCT) showed IX media outperforming GAC. Wright-Pierce and the Town chose an IX resin PFAS system for the plant. Cold-weather pilot testing occurred later in the project.
About the Photo
When asked about the drone shot of the plant taken by CAD/BIM Manager Chris Hinkley, Project Manager Rob Williamson said, “Rather than contend with adding a new process to the existing building, Wright-Pierce and the Town agreed to separate it from the existing facility. This allowed the entire new process to be constructed, tested, and commissioned without impacting the existing process. We also selected materials and equipment that were most readily available during the COVID pandemic to ensure the best chance of meeting the Town’s schedule needs.”
Project Impact
Since coming online, the IX resin PFAS system has been removing PFAS to non-detect levels. This project also had the additional benefit of improving the overall water quality from the plant. Operators reported water quality was better than anything that had been produced in the past. To learn more about this project, check out our initial article published in October 2023.
Thank you for taking this journey with us as we reviewed the impactful projects highlighted on our 2025 calendar. To learn more about how Wright-Pierce can assist with your environmental engineering needs, or to receive a copy of our 2026 calendar, contact us today.