Here's How One Community Made Quick Work of PFAS

A New York town removes PFAS from its drinking water supply in four months using a granular activated carbon treatment system.

Here's How One Community Made Quick Work of PFAS

Granular activated carbon adsorber pipes are connected to a valve manifold that directs the water to and from the granular activated carbon vessels.

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PFAS, used in nonstick and waterproof coatings, personal products and fire suppression foams, have become a significant concern for drinking water utilities.

These long-molecular-chain fluoride and carbon chemicals are resilient and are suspected of being linked to many health risks. Federal oversight with clearly defined safe and unsafe thresholds has been absent, leading many states to set their own standards.

For local government decision-makers, media coverage of the issue has created a need for some knowledge of high school chemistry: parts per trillion, compounds, molecular chains, adsorption and absorption are commonly used terms.

Unfortunately PFAS, known as “forever chemicals,” are still considered emerging contaminants, and so regulatory consensus remains elusive. While many treatment methods are being discussed, it is hard to know what is proven to work.

Therefore, recent experience of the Town of New Windsor, New York, is of interest. Aztech Environmental Technologies, a LaBella Company, designed, procured and installed a PFAS treatment system for the town in only four months.

NO PFAS — AT FIRST

Historically, the town purchased water from the City of New York (Catskill Aqueduct) at significant expense. Town officials worked for more than 12 years to develop an independent water source, ultimately drilling and constructing three wells, which are the largest-yielding municipal wells in the state.

Knowing about issues at the nearby Washington Lake site, in 2016 the town sampled the new wells for PFAS and found them nondetect, based on detection limits in the range of 10 parts per trillion.

After development of the wells, the Butterhill Water Treatment Plant was constructed with a design capacity of 6.4 mgd. It was designed to treat elevated levels of iron and manganese, which were identified in the well water. The plant went online in August 2018.

TROUBLE DETECTED

Later, on two occasions, the state Department of Health tested water from the Butterhill plant; the samples tested positive for PFAS (notably PFOA and PFOS). However, town officials and representatives were not told of the results until February 2019, and only verbal confirmation of a positive result was provided.

The written report town officials received was the first indication of the specific levels of PFOA and PFOS in the water that sourced the wells. The levels were below the U.S. EPA public health advisory and even the proposed maximum contaminant limit.

Still, out of an abundance of caution for its residents, the town shut down the wellfield and returned to the Catskill Aqueduct for its source of supply. Officials quickly realized they were on the clock for solutions for the Butterhill plant: A planned maintenance closure of the Catskill Aqueduct was scheduled for November 2019.

REVIEWING OPTIONS

The New York State Department of Environmental Conservation retained Aztech to develop a solution. Given the short timeline, the company turned to carbon: readily available, easy to procure and one of the most reliable treatment technologies.

Granular activated carbon has long been used in water treatment for its ability to adsorb most chemical compounds while allowing clean water to pass through. Another treatment considered was ion-exchange resin, which offers some advantages and trade-offs.

Whereas carbon adsorbs most organics, ion exchange can be tailored to adsorb only certain compounds. This tailoring of treatment can extend bed life and reduce media changeouts. Resin vessels can also have a smaller footprint due to the lower residence time than carbon. However, resin costs more than carbon, and some resins cannot be regenerated, requiring thermal destruction. Aztech recommended the GAC treatment, and the DEC agreed to proceed.

DEPLOYING THE SOLUTION

The New Windsor system consisted of six 10-foot-diameter, 20,000-pound carbon units, able to produce 1,500 gpm (2.16 mgd). The balance of the supply was provided by neighboring municipal systems and a smaller supply well, owned by the town.

After the carbon vessels were delivered and installed, disinfection and testing were performed on the vessels and related plumbing. Backwashable GAC vessels were installed and also tested.

Backwashing of carbon vessels is occasionally required to reduce water flow channelization and to remove any materials that may have been deposited on the top of the carbon bed. However, it presents some issues. Breakthrough of PFAS constituents can occur due to the redistribution of the bed, moving more contaminated carbon particles from the upper bed to the lower bed. With that in mind, the backwash procedure and schedule has to be well planned.

The Butterhill plant water was deemed compliant after testing for bacteria, microbes and turbidity according to state Department of Health regulations. The GAC treatment system was brought online, and the Butterhill treatment plant was once again fully operational, producing water with undetectable PFAS contamination.

LESSONS LEARNED

Since commissioning, some site water drainage modifications have been made. In addition, a tensioned fabric building was constructed and propane tanks and heaters were added to keep the system operational through the winter.

The New Windsor story illustrates that it is possible to treat a PFAS-contaminated water supply in a relatively short time. Aztech designed, built and tested that system using in-house services, but in other instances, the company has collaborated with customers’ consultants and engineers.

Available funding may depend on the source of contamination; in New Windsor, questions remain about culpability for the contamination; for the time being, the state of New York is funding the project. Cost recovery will begin after the responsible party is determined.

Plants located near potential PFAS sources should test for contamination regularly and proactively. Depending on the plant and contamination levels, some cities and towns may choose to seek uncontaminated water sources elsewhere. However, cost-effective treatment is possible and will likely become more refined with each community that tackles the challenge.

ABOUT THE AUTHOR

Fil L. Fina III, P.E., (ffina3@aztechenv.com) is environmental remediation program manager at Aztech Environmental Technologies, a LaBella Company and a full-service environmental, geology/hydrogeology and remediation consulting and contracting firm.   



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