Small-scale water treatment systems for PFAS removal in the United States: technologies, costs and environmental justice implications

In April 2024 the United States set its first enforceable limits for per- and polyfluoroalkyl substances (PFAS) in drinking water. Ninety-seven percent of the country’s 156,000 public water systems are small, serving fewer than 10,000 people. The water industry expects 90 percent of the treatment installations the rule requires to land on them. These are systems run by one or two operators, often part time, with no engineer on staff and no spare budget.

We pulled together ten years of research, federal monitoring data and industry cost studies to answer the question those operators are actually asking: which technology, at what cost, and what do I do with the waste. Granular activated carbon removes more than 95 percent of the long-chain PFAS but under 55 percent of the short-chain ones the rule also covers. Ion exchange lasts about ten times longer between media changes and holds up on short-chain compounds. Membranes remove more than 99 percent of everything but are unaffordable below about 3,300 people. For the smallest systems the bill comes to between $305 and $11,150 per household per year, against an affordability threshold of about $1,022. When a small system does comply, it produces concentrated PFAS waste with no federal disposal standard and, since 2024, potential Superfund liability.

The rule was written for the whole country. The bill lands on the smallest towns, which are disproportionately rural, tribal and low-income. And 43 million people on private wells are outside it altogether. The paper gives small-system designers a decision framework tied to system size, PFAS profile and budget. It also names the perverse incentive at the center of the policy: complying creates a hazardous waste stream that the law then holds you liable for. Five specific priorities are proposed ahead of the 2029 compliance deadline.