PFAS Mitigation, Shrewsbury, MA

A PFAS Journey to Determine Effective Management and Treatment Options

Tata & Howard is working with the Town of Shrewsbury, MA to address perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the groundwater. The Town of Shrewsbury water system serves a population of approximately 38,300. The system consists of about 200 miles of main, nine active groundwater wells from three well sites, three pressure zones, six storage tanks, and one water treatment plant. The 7.0 million gallon per day (mgd) Home Farm Water Treatment Facility utilizes biological treatment for removal of manganese.

In 2020, Shrewsbury detected PFAS in the wells. Sampling has indicated that PFAS is present in most of the wells operated by the Town but under the maximum contaminant level (MCL) of 20 nanograms per liter (ng/L) for PFAS6 as regulated by the Massachusetts Department of Environmental Protection (MassDEP) which includes the sum of concentrations for PFOS, PFOA, PFHxS, PFNA, PFHpA, and PFDA. Raw water from one well site, the Sewell Well, has been consistently higher than 20 ng/L; but the finished water from all wells after treatment at the Home Farm Water Treatment Plant has been in compliance and consistently less than 16 ng/L. Most of the PFAS is in the form of PFOA and PFOS which are the two compounds for which the EPA has developed a proposed MCL. The PFOA indicated by the green bar in Table 1 is higher than the proposed Federal MCL of 4 ng/L.

Currently, the Town has been managing the sources to improve water quality and stay under the current MCL of 20 ng/L for PFAS6. A mass balance is utilized to estimate finished water PFAS concentrations based on updated sample results and changes in the operation of the sources. Tata & Howard created the base tool which can be used to see how changes to PFAS levels or flow rates can affect the finished water concentration.

Table 2 represents existing conditions. The numbers used for PFAS are the highest results from each individual well observed in a year of sampling data, showing the finished water level is about 16 ng/L.  As long as the PFAS concentrations in the wells remain consistent, the Town will remain in compliance. If sample results change and they see an increase in PFAS concentration at Sewell, the Town will make adjustments using the mass balance to manage the sources to remain in compliance.

 The Town cannot manage sources like this indefinitely. They decided to move forward with reviewing PFAS treatment options and pilot testing to determine the best course of action if/when treatment is required.

Tata & Howard and the Town considered three treatment options. The first option is anion exchange, which uses a resin with positively charged ions. These are typically single use resins and require one to three minutes of empty bed contact time. The next option is Granular Activate Carbon (GAC) which uses adsorption. This media can be made from different types of carbon sources that can be recycled through thermal reactivations and requires a ten minute empty bed contact time. There are limitations with GAC on some of the short chain PFAS. The third type is novel media, which includes other types of media that do not fall into the first two categories. The novel media piloted uses an adsorption process that is classified as a single use resin and has a two to three minute empty bed contact time.

Pilot System

Shrewsbury’s pilot testing utilized three anion exchange resins from two suppliers (one of which was regenerative), a coal-based GAC, and a novel media. The novel media selected works like GAC since it is not as sensitive to chlorine and chlorides, which can impact the effectiveness of anion exchange resins.

The GAC pilot test utilized two 6-inch columns in series rather than one very tall column to give more flexibility for installation and backwashing. A total of 10 gallons of media were installed with a loading rate of 7.5 gal/ft2 and an empty bed contact time of approximately ten minutes. The anion exchange and novel medias each utilized one 6-inch column with five gallons of media installed, a loading rate of 11.25 gal/ft2, and an empty bed contact time of approximately two minutes.

The water source was a tap on the effluent line from the existing filters using finished water that had been treated for manganese removal but not any of the chemical additions of KOH, phosphate, chlorine, and fluoride. There were control valves so the water only came through the unit when the treatment plant was online, which is typically more than 20 hours per day.

There was an initial baseline water quality sampling event at the start, at the end of week 20, and at the end of piloting. PFAS samples were taken day one, day seven, and then monthly for the duration of the pilot. Samples were taken from the 25% sample tap until breakthrough (50% of the raw water PFAS levels, so between 6 and 7 ppt), then at the 50% tap.

Table 3 shows the result from the different taps at the end of the pilot.  The anion exchange results are from the best performing anion exchange resin. GAC was first detected in week 8 with breakthrough in the 25% tap in week 16 and the 50% tap in week 44. There was a detected amount in the final sample tap in week 64, which was the final week of the testing.

Anion exchange had the longest time to first detect but the 25% breakthrough for all anion exchange and novel media were all within a sample event or so of each other and occurred between weeks 44 and 52. The novel media had breakthrough of the 50% tap at week 60 and was detected in the 100% tap at the final week while the anion exchange was ND in the 100% tap at the end of the pilot.

Table 4 is a summary as to what the permanent filter system may look like. The filters are similar in size but the number of recommended filters differs for each resin. The overall building footprint is similar as well. The anion exchange did perform slightly better than the novel media, however, the overall PFAS removal results over the duration of the pilot was similar. Because of this, construction costs, long term media replacement costs, and operational considerations were included as part of the media selection process.

The Town has not yet made a final decision on media type, but it appears that the novel media may be the best fit for the Town’s needs.  Specifically, the novel media allows for some backwashing and chlorination, reducing the potential of biofilm buildup and potential capacity loss due to increased headloss through the media. Additionally, the novel media has a smaller footprint in comparison to GAC.  The Town of Shrewsbury’s current PFAS levels do contain mostly PFOS and PFOA at concentrations higher than the proposed Federal regulations for those two compounds. Also, based on reviewing the data of the PFAS6 compounds, PFOA was the compound first detected for all media; also, the majority of the detected PFAS6 concentrations in the effluent throughout the pilot were PFOA.

One additional challenge moving forward is the design of the facility so the water goes through the manganese treatment first, the new PFAS treatment next, and finally utilizes the existing clearwell for chlorine contact, with finished water pumping into the system, all while keeping the existing treatment online during construction and start up.  Tata & Howard is currently completing a preliminary design to better estimate costs before completing the final design, permitting, and ultimately construction.

Water Treatment Plant, Amherst, MA

Tata & Howard contracted with the Town of Amherst for design, permitting, and bidding of the 1.5 million gallon per day (MGD) Centennial Water Treatment Plant, to treat surface water from the Pelham Reservoir System. The existing Centennial WTP, located in the Town of Pelham but supplying the Amherst Public Water System, has a history of issues with turbidity, color, and disinfection byproducts in the form of total trihalomethanes (TTHM) and haloacetic acids (HAA5) because of high levels of organics in the Pelham Reservoir System. Due to the age and condition of the existing WTP, the filters which were the primary treatment process at the existing WTP were no longer effective at removing organics, leading to a decrease in finished water quality and total WTP capacity.  The existing Centennial WTP has been offline since 2018 due to water quality, as well as infrastructure concerns related to a lightning strike which impacted pumping equipment and communications at the Centennial Water Treatment Plant’s raw water pump station.

Based on the results of the pilot study performed by the Town of Amherst, Tata & Howard completed design of the new Centennial Water Treatment Plant including dissolved air flotation (DAF) clarifiers and granular activated carbon (GAC) filtration for treatment of organics, color, turbidity, and low levels of iron and manganese. The DAF system includes polyaluminaum chloride for coagulation, two rapid mix chambers, and three package DAF units which each include two high rate flocculation chambers, two low-rate flocculation chambers, a saturation tank, effluent collection system, discharge weir, mechanical skimmers and beach, and associated appurtenances and controls. Three dual media filter chambers with a silica sand/course garnet base layer and GAC above are located downstream of the DAF units, prior to final chemical addition.

Additional chemical feed includes a gaseous chlorine system for 4-log inactivation of viruses, gaseous ammonia for chloramine formation, sodium fluoride for dental health, and sodium hydroxide for pH adjustment and corrosion control. The new facility also includes an advanced Supervisory Control and Data Acquisition (SCADA) system for automated control of the water treatment plant. Operators for the Town of Amherst will be able to remotely monitor and control operation of the Centennial WTP, through a recently extended town fiber optic cable network.

The design of the Centennial WTP included provisions to maintain the Amherst water distribution system, as even with the Centennial WTP offline, the clearwell of the existing facility also serves to maintain pressure in a small portion of the water distribution system between the Centennial WTP and a booster pump station. The Centennial WTP feeds the majority of the water system (excluding the portion between the WTP and the booster pump station) by gravity. Since the existing WTP including the clearwell will be demolished prior to construction of the new WTP, design and construction of the new WTP will include a temporary water storage tank to maintain pressure and keep all connections active in the high service area of the Amherst Public Water System.

Permitting for this project included a BRP WS 24 New Treatment Plant application with MassDEP, Site Plan Review with the Pelham Zoning Board of Appeals, and a Request for Determination of Applicability (RDA) with Pelham Conservation Commission.

The Centennial Water Treatment Plant was recently bid and awarded to R.H. White Construction Co. of Auburn, MA for a contract amount of $18,876,000.  This project received funding though the Drinking Water State Revolving Fund program, and construction is expected to be completed by the summer of 2025.

Godfrey Brook Water Treatment Plant

Today’s volume and demand for daily water use may have changed since the town incorporated in 1881, but one goal remains constant to this day: safe water.

Team T&H continues to deliver safe, potable water through engineering excellence of precision, collaboration, feedback, and commitment between all team members, water department operators, and project managers. The Godfrey Brook WTP project scope involves construction administration and resident project representative services. Process elements of the project include biological iron and manganese pressure filters, a packed tower aerator, and chemical addition for the purpose of pH adjustment, corrosion control, and disinfection.  The new WTP includes a clearwell to achieve 4-Log inactivation of viruses prior to the distribution system. The WTP also includes HVAC, plumbing, electrical, and advanced SCADA systems for monitoring and control of the new treatment plant and the wells. Site work includes new raw and finished water mains, stormwater controls in the form of a sub-grade stormwater infiltration system, and residuals storage tanks for solids handling after backwashing the biological filters, and electrical including a new electrical standby generator. The project also includes site upgrades to the wells and access road, including an RCP culvert replacement to improve drainage of Godfrey Brook (a tributary stream into the Charles River), submersible well pumps and motors for the seven wells, and a precast concrete raw water metering vault for flow control. Currently, the biological filters are in the acclimation phase, the final step prior to a performance test to confirm effectiveness of removing iron and manganese.


Located to the left of the Godfrey Brook WTP’s exterior stands a packed tower aerator (shown above). The tower aerator removes carbon dioxide to increase pH in a more cost effective manner than chemical addition, and adds dissolved oxygen before the biological manganese filters, which is critical to biological filtration.

Biological manganese filters (above) come after the packed tower aerator for efficient removal of manganese. Biological iron filter is upstream of the packed tower to optimize the performance of all downstream processes.

The project included a culvert reconstruction to replace a damaged pipe. Culverts are trench-like constructs designed to allow free-flowing water beneath a road or railway, whether stormwater or a stream. Pictured is the finished culvert over Godfrey Brook, a tributary to the Charles River. 

T&H team members Matt O’Dowd, Juliette Burcham, Mitch Garon, and Barry Pociask review the electrical connection for the disconnect of the submersible well pump for well 1A. The Godfrey Brook Wellfield features seven total gravel packed wells: five rehabilitated and two newly installed.

The newly installed chemical feed system includes skid-mounted chemical metering pumps used for potassium hydroxide; here, chemical addition occurs for pH adjustment, along with the addition of sodium hypochlorite for disinfection and zinc orthophosphate for corrosion control prior to entering the water distribution system. 

Maher Water Treatment Plant – Groundbreaking Ceremony

On Wednesday, August 7, 2019, the Hyannis Water System and officials from MassDEP held a ceremonial groundbreaking for construction of the new Maher Water Treatment Plant designed by Tata & Howard, Inc.

The $12 million water system upgrade, funded by the MassDEP SRF program, will enable the Town to meet new and stricter federal and state regulations for emerging contaminants. The new plant will treat elevated levels of Perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), 1,4-Dioxane, iron, and manganese in the three drinking water production wells at the existing facility.

The water filtration building at the Maher Water Treatment Plant has a design capacity of 1,500 gallons per minute. Using granular activated carbon filtration, the successful removal of PFOS/PFOA will be obtained. Advanced oxidation with peroxide and ultraviolent (UV) light will treat 1,4-Dioxane. Lastly, greensand pressure filtration will not only remove the iron and manganese, but also extend the useful life of the granular activated carbon.

Tata & Howard has been instrumental in the evolution of this project. In December of 2016, Tata & Howard provided a conceptual design report to Barnstable’s Department of Public Works. A pilot test report was submitted in early 2018 and design began shortly thereafter.

The Hyannis Water System currently consists of four water treatment facilities, four storage tanks, 12 well pumping stations, and a 107-mile distribution system. The water system provides drinking water services to approximately 18,000 residents through 7,249 metered service connections to residential and commercial properties.

Waterline Industries Corporation of Seabrook, NH constructed the filtration building, and Tata & Howard provided construction administration and resident observation. The facility was operational in October 2020.

Canaan, VT and Stewartstown, NH Energy Efficient Wastewater Treatment Plant Upgrades

The Towns of Canaan, Vermont and Stewartstown, New Hampshire operate a shared wastewater treatment facility, which required significant upgrades. The existing facilities were 40 years old and although a few upgrades were performed in the 90s, the facilities were not performing well, did not meet Life Safety codes, and required significant maintenance. The upgrade met all of the goals of the Client by providing for simple operation and maintenance requirements, meeting the Life Safety codes, eliminating confined spaces, lowering of electrical power costs, and meeting discharge parameters through production of high quality effluent. The solutions developed for the upgrade to this facility were also economical.

Control building insulated concrete forms

One of the primary elements of the design was the consideration of the economics of energy reduction. The design incorporated insulated concrete form construction for the building walls with R-49 insulation rating in the ceilings.  The design also included a wood pellet boiler with a pellet silo and hot water heating system, which allowed for reduction of explosion proof heaters in the headworks building. All of the windows were low-E and highly insulated, and an outer glassed-in entry way increased the solar gain retention of the building and reduced heat loss.  he process headworks and operations buildings were constructed as single story structures, increasing operator safety.

The lagoon aeration system is now a fine bubble, highly efficient process with additional mixing provided by solar powered mixers that help reduce aeration requirements, improve treatment, and allows for the addition of septage, all at no cost due to solar power. The pump station upgrades were designed to eliminate daily confined space entry by the operator by the conversion to submersible pumps. For sludge removal, a unique and simple “Sludge Sled” system was incorporated, which allows the operators to easily remove the sludge at their convenience. Sludge treatment is accomplished with a geo-bag system that allows the sludge to be freeze dried, reducing the volume by almost 50% with no energy consumption.

The influent pump station was designed with three pumps instead of the normal two-pump system in order to meet both present and future design flows, allow for lower horsepower pumps, improve flexibility, reduce replacement costs, and reduce energy costs. The other four deep dry pit pump stations were converted to wet wells and submersible pumps, eliminating confined spaces, and are equipped with emergency generators, eliminating the need for operator attention when power is lost.

Solar mixers for lagoons

The incorporation of highly energy efficient building components resulted in reducing annual operation and maintenance costs, which resulted in lower user rates and a more sustainable facility. All building components are virtually maintenance free.  All of the equipment and processes were selected to reduce both annual and future replacement costs.

The treatment system is a 3-cell aerated lagoon system, and the solar powered mixers were installed to enable reduction of the aeration needs and horsepower during the summer months when septage is added.  The aeration blowers, which are housed in insulated enclosures, reduce noise and were sized to allow for the addition of septage to the lagoons, which is not common in Vermont. The aeration blowers are controlled with Variable Frequency Drives (VFDs), which allow for greater operator control of aeration and provide energy cost savings. The operation is simple and safe for operators and others who need to maintain the facility and equipment. The design has provided flexibility to the operators and has resulted in an energy efficient, sustainable solution for this community.


 

 

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Ozone Water Treatment Plant in Franklin, MA

Tata & Howard provided design and construction services for a new water treatment facility that houses a 1.2 mgd ultrafiltration system and completed a pilot test that consisted of an evaluation of two separate ultrafiltration technologies. Franklin Wells No. 1 and 2, located off Hayward Street in Franklin, Massachusetts were installed in the 1940’s with a combined safe yield of 1.2 million gallons per day. Due to high concentrations of iron and manganese in the groundwater, the wells were only used to meet peak water demands during the summer months. The construction of the water treatment facility recaptures the yield from these two sources.

The water treatment facility consists of a main building which houses static mixers, ozone feed equipment, chemical feed equipment, prefilters, membrane filtration equipment, instrumentation and controls. Treatment consists of ozone oxidation followed by membrane ultrafiltration. The project was funded in part by the Massachusetts Water Pollution Abatement Trust through a low interest state revolving fund loan.

The overall treatment scheme is as follows: ozone injection, oxidation of iron and manganese in an ozone contact tank, prefiltration, treatment through two ultrafiltration membrane skids, chlorination prior to a clearwell, and fluoride addition prior to discharge into the distribution system. The plant is designed to recycle backwash water and membrane recirculation water to the head of the plant utilizing two decant tanks. Ozone is produced on site utilizing compressed air, while a LOX tank is available to allow for the production of additional ozone if required in the future.

 

Pilot Testing for Iron and Manganese Removal in Barnstable, MA

Due to elevated levels of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), 1,4 Dioxane, and iron and manganese in the three drinking water production wells at the Maher Water Treatment Facility, the Town of Barnstable is proceeding with design and construction of upgrades at the facility to treat for these constituents.

Pilot testing includes carbon, Greensand, and LayneOx filters

The Town of Barnstable is currently conducting pilot testing at the site to determine the required design parameters, treatment process effectiveness, and best technology to achieve the desired treated water.  Treatment processes associated with pilot testing include GreensandPlus and LayneOx for removal of iron and manganese, advanced oxidation (ultraviolet light with hydrogen peroxide) for removal of 1,4-dioxane, and granular activated carbon (GAC) for removal of PFOS and PFOA.  Treatment for 1,4 Dioxane is the primary goal of the pilot test in order to meet the requirements of the Massachusetts Department of Environmental Protection (MassDEP) New Technology Approval process.

The MassDEP has confirmed that pilot testing of GAC filtration at the Maher facility is not a statutory requirement due to the current use of this water treatment technology at the Town’s Mary Dunn Wells and the availability of current water quality data for treatment of PFOS/PFOA within the same water system.  However, the Town has decided to include GAC filtration with pilot testing of advanced oxidation and iron and manganese removal to evaluate the performance of all proposed treatment processes operating together.

UV reactor for pilot test

Pilot testing is being conducted by Blueleaf, Inc. as a sub-consultant to Tata & Howard, Inc.  Pilot testing was completed in 2017.

 

 

 

 

Funding Assistance for WWTF Upgrade in Lyndon, VT

Upgrade for a 750,000 gallon per day extended aeration wastewater treatment facility to an A/O biological facility. Assistance included acquiring State CWSRF planning grants and USDA Rural Development grant for extensive improvements including separation of combined sewer/stormwater collection systems (CSO), advanced Class A sludge treatment, and reconstruction of original 1970’s treatment facility to new Anoxic/Oxic Treatment System. Total grant funds were $7,275,000.

Water Treatment Plant in Concord, MA

This project included construction of a 1.5 mgd capacity water treatment facility to treat potable water pumped from the existing Deaconess Well. The water treatment facility consisted of six vertical LayneOx pressure filters. The work also included demolition of the existing well pumping station and construction of a well pump vault with vertical turbine pump over the existing well, and completion of a SCADA system design to monitor and control the water treatment facility and well station.

Background:

Faced with increasing iron and manganese concentrations at two of its existing wells, Concord Public Works (CPW) decided that treatment was required.  Several treatment options were evaluated, with the most cost effective option being pressure filtration.  Piloting pitted manganese greensand against LayneOx, a proprietary media marketed by Layne-Christensen Company utilized in other parts of the country, but not in New England. In addition to proving its effectiveness in iron and manganese removal, “new technology approval” was obtained for the media from MassDEP. Although piloting showed LayneOx to have an advantage over greensand during testing at the Deaconess well site, the Town’s Procurement Office was reluctant to allow CPW to solely specify a proprietary media. Differences in piping and chemical requirements for both filter processes precluded a design that could have served either treatment system. Hence, a pre-purchase equipment bid was developed specifying both systems.

An additional challenge to treating the water was designing the treatment facility itself, whose architecture had to “blend in” with the bucolic and well healed character of the surrounding neighborhood. The Town requested that we provide three options simulating different themes; a barn, railroad station and a Richardsonian Romanesque style structure similar to the Chestnut Hill pump station. Our Architect provided renderings of the three options along with estimated costs and lists of pros and cons. After several meetings and input from various interested parties the Town chose the barn theme.

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Water Treatment Plant in North Chelmsford, MA

Tata & Howard completed a test evaluation and design report for the Bomil Well site comparing ultrafiltration using ozone and chlorine dioxide as oxidants. The report also evaluated several coagulant aids to treat the organic color in the water. The design report became the basis for the 2.5 mgd water treatment facility designed by Tata & Howard. The facility uses membrane filtration with chlorine dioxide for treatment.  Construction administration was also provided by Tata & Howard.