No silver bullet for wastewater treatment of PFAS

By Martye Griffin, Director of Ecosystem Services

Chemistry can be a wonderful thing. It can provide lifesaving medicines for conditions that were once untreatable. It allows our vehicles to be more efficient and less-polluting, and to kill germs and viruses on surfaces throughout our homes and businesses. We appreciate how a rain suit keeps us dry while watching our children play sports in the rain, but we lament investing in a home water filtration system to protect our families because unwanted chemicals that have leached into our drinking water.

While chemistry has its drawbacks, the reality is chemicals are a part of our lives, and PFAS is no exception. But unlike other chemicals, there are limited options available to remove the PFAS that comes to our regional wastewater treatment plant, passes through our treatment system, into the water recycled into Badfish Creek and beyond. Treatment technologies for PFAS are rapidly evolving, but technologies like thermal treatment or using other chemicals to destroy PFAS require extreme temperatures or high chemical doses to be even partially effective in destroying PFAS. So far, there is no feasible large-scale treatment that is absolutely 100% effective in destroying PFAS.

So far, there is no feasible large-scale treatment that is absolutely 100% effective in destroying PFAS.

There is a reason for these challenges around destroying PFAS, and it has to do with the wide-ranging chemical and physical characteristics of PFAS. Characteristics include the strength of the chemical bond between carbon and fluorine, the ionic state and which ionic group the PFAS compound belongs to, chain length, and total concentration. These characteristics of PFAS compounds make it virtually indestructible to common treatment technologies.

Options for wastewater treatment plants

If we can’t destroy the PFAS in the wastewater that comes to us, what treatment options do we have? So far, the most common technologies for PFAS treatment include separating PFAS from the water using granular activated carbon, ion exchange resin, or reverse osmosis. Since these technologies do not destroy PFAS, the resulting residue (spent activated carbon, resins and concentrate) must be managed through further treatment and/or disposal through stabilization or incineration.

These limited treatment options hold additional considerations for wastewater treatment providers like the District to meet our mission of protecting human health and the environment. With ion exchange and reverse osmosis, there are concentrated liquid waste streams that must be further treated prior to discharge to the environment. With granular activated carbon, the carbon regeneration process that is necessary to reuse the filtering material has the potential to release PFAS to the atmosphere. Additionally, incineration poses additional health and environmental risk through incomplete combustion and by-product generation.

The cost to ratepayers

Modifications to add additional treatment steps to a wastewater treatment plant of our size is always an expensive endeavor. And while there is no price on protecting human health and the environment, costs for treating PFAS and in turn, the increase in rates the public pays, must be considered. The level of expense of treating PFAS can vary based on many factors, including the type of PFAS compound; the daily flow of wastewater coming to the plant; used filter material disposal or regeneration; and treatment and disposal of reverse osmosis liquid concentrate.

Recent information has shown that cost to treat PFAS impacts ratepayers. In New Hampshire, a water and sewer district increased its rates 40%, in part due to PFAS concerns. The District’s own study to treat our wastewater for chloride using reverse osmosis technology (a technology that could also remove, but not destroy, PFAS in wastewater) would cost the District $500 million in capital costs. Customer communities, and eventually homeowners, renters, businesses and industry, would shoulder much of this cost if it had been an approach the District pursued.

A sustainable, holistic approach

There is no price on protecting human health and the environment, but we must consider if the money we do spend is being spent in the correct way to meet our mission and is equitable to our ratepayers. With PFAS, money is better spent on an upstream solution rather than an end-of-pipe solution. Spending money on pollution prevention, product substitution, etc., are much cheaper and is holistic solution that offers a long-term, sustainable approach to keeping our waters clean.

Within all these considerations, the District remains committed to addressing PFAS concerns and has effective tools to do so. As demonstrated by the success of long-standing mercury and chloride source control efforts, minimizing the amount of PFAS coming into the plant is the best way to reduce the amount of PFAS leaving the plant.