The Town of Burlington, Massachusetts’ water sources consist of an in-town surface water supply, seven groundwater wells, and surface water purchased through an interconnection to the Massachusetts Water Resources Authority (MWRA) water distribution system. The in-town supplies are treated at two separate water treatment plants before being introduced into the distribution system.
In April of 2021, Burlington sampled its Mill Pond source water for PFAS. The results revealed elevated levels of PFAS6 compounds above the 20 ng/L limit. In June 2021, the MassDEP issued the town a Notice of Non-Compliance requiring that Burlington treat the source to reduce concentrations of PFAS6 or shut down the supply altogether. Continued sampling indicated that PFAS6 concentrations in the Mill Pond source water ranged from 44–55 ng/L with an average of 45 ng/L, more than two times the allowable limit.
In late 2021, Wright-Pierce proceeded with the permitting, design, and construction oversight of adding a PFAS removal process to the Mill Pond water treatment plant. The Town required that the new PFAS treatment be designed, constructed, and online within 18 months.
Subcontracts were immediately established for two-season pilot testing of multiple granular activated carbon (GAC) media and ion-exchange (IX) resins, rapid small-scale column testing of GAC, wetlands delineation, and geotechnical services. The final plan for design, procurement, and bidding included the following:
- Design and pre-purchase of the PFAS pressure vessel system
- Design and pre-purchase of transfer pumps and variable frequency drives
- Design and bidding of a small contract to prepare the site for the prime contractor
- Design and bidding of the general contract for the construction of the PFAS system
Normally design and permitting for a project of this type could take up to two years for two-season piloting, design, permitting, regulatory approval, as well as State Revolving Fund approvals. Because of the need to accelerate the schedule, the design for Burlington was compressed into a space of just under four months.
Within the first six weeks of design, bids were received for equipment pre-purchase, and two-season piloting and rapid small-scale column testing (RSSCT) for both GAC and IX resins began. The design of the PFAS pressure vessel system included provisions for both the use of GAC and/or IX media. First-season RSSCT results showed that IX media performed far better than GAC because the filtered total organic carbon (TOC) concentrations were high enough to compete with PFAS for the absorptive sites on GAC media.
The ion-exchange resin PFAS system is complete and removing PFAS compounds to non-detect levels. In addition, the process resulted in the unintended benefit of significantly improving overall water quality – operators report that water quality has never been better in over 20 years of operation.
Do you have questions regarding PFAS and its treatment? Please contact us today to learn more.