Our sewage often becomes fertilizer. Problem is, it’s tainted with PFAS

Read the full article by Barbara Moran (WBUR)

“The Deer Island Wastewater Treatment Plant is a pollution success story. Over the last several decades, it transformed Boston Harbor from a nationally embarrassing cesspool into a swimmable bay.

The treatment plant takes everything the people of Greater Boston send down their sinks, toilets, showers and washing machines — plus industrial waste — and treats it. The treated water is clean enough to let out into the ocean. The remaining sludge gets recycled into fertilizer that’s used in nearly 20 states.

But now that fertilizer is raising fresh concerns. That’s because wastewater treatment plants like Deer Island were not built to handle the toxic ‘forever chemicals’ known as PFAS.

The treatment process concentrates PFAS chemicals in the sludge, and therefore in the fertilizer, leading environmentalists and public health advocates to call for an immediate end to its use. Others are not sure that a full ban on sludge-based fertilizer, or ‘biosolids,’ is the answer. But there is widespread agreement that we have only begun to grasp the extent of the problem.

‘I think we’re only starting to discover how important biosolids are as a source of PFAS contamination,’ said Heidi Pickard, a Harvard doctoral student who is analyzing soil and corn from farms contaminated by sludge-based fertilizer.

‘Most states have not even begun to test to see if biosolids that have been applied to land are contaminated, that soil is contaminated,’ Pickard said. ‘I think if they go and look, they’re going to discover that this is a huge contamination issue everywhere.’

The ‘pollution sink’

Forty-three communities — about a third of the people in Massachusetts — send their wastewater to Deer Island. Industrial and household waste, stormwater, the liquid that leaks from landfills and the slop pumped out of septic tanks — it’s all tunneled to the plant with its iconic egg-shaped tanks. On average, the plant receives and treats more than 330 million gallons of wastewater each day, making it the second-largest treatment plant in the country, by volume.

Because thousands of consumer and industrial products — from waterproof cosmetics to toilet paper to firefighting foam — contain PFAS, the wastewater coming into Deer Island, like wastewater everywhere, is contaminated with the chemicals.

‘What gets into wastewater is just about everything that we use in our society, because it’s the pollution sink for what’s out there. Which is a big deal when we’re talking about PFAS,’ said Laura Orlando, a civil engineer and senior science advisor for Just Zero, a nonprofit focused on waste.

Treatment plants don’t remove PFAS from wastewater or sludge, and there’s no easy or cost-effective way to do it, Orlando said. It’s also not their job.

Wastewater treatment plants are designed to remove excess nutrients like nitrogen and phosphorus, kill pathogens and filter out items like gravel and sneakers that find their way into the waste stream. ‘It’s not about, ‘take out this chemical, take out that chemical, reduce your PFAS,’’ Orlando said.

At Deer Island, part of the treatment process happens inside the giant eggs, which are filled with bacteria happily eating sewage. Each egg can hold 3 million gallons of sludge, storing the warm slurry for weeks at a time.

Inside, microbes drastically reduce the volume of sludge, which is useful because the plant then has less to manage. The microbes also give off methane the plant captures and converts into power.

But there’s something else that happens in the eggs: the heat and microbes can transform PFAS chemicals from one form to another. More specifically, certain PFAS molecules known as ‘precursors’ can chemically change into known PFAS toxins. These toxic PFAS then stick around in their final form. These changes can also happen in other places with microbial activity, like soil.

This chemistry is important. Harvard chemist Elsie Sunderland, who studies PFAS precursors, said that their chemical formulas are often closely held trade secrets, making them difficult to track and measure. Sunderland said the only way to get a real handle on how much PFAS is in sludge, or anything, is to stop counting individual types of PFAS, and instead measure the total mass of molecules with PFAS’s telltale carbon-fluoride bond. But there are only a few commercial labs that can do this. Most tests trace only a handful of PFAS chemicals, rather than the thousands that exist.

Deer Island has tested its biosolids for 16 PFAS compounds since 2019, and has just begun tracking 40 types. For two of the most concerning molecules, PFOS and PFOA, its monitors find an average of 15 parts per billion combined.

But it’s hard to know what to make of these numbers, and not only because of the measurement problem: right now there’s no state or federal rules that say how much PFAS in biosolids is too much.

A few states have guidelines, but they vary widely. For instance, fertilizer made from Deer Island sludge would be allowed under Michigan’s specs but not Connecticut’s. Maine banned the use of sludge-based fertilizers altogether in 2022, the first and only state to do so. Massachusetts has no guidelines, but regulators are ‘exploring options.’

Right now, the fertilizer pellets or ‘biosolids’ from Deer Island are used in almost 20 states, including Massachusetts, New York and Pennsylvania. Biosolid-based fertilizers are also sold for home use, according to an analysis by the Sierra Club.

Industry advocates say that turning sludge into fertilizer is a far better option than burning it or throwing it into a landfill.

‘We’re putting carbon back into the soil. There’s a lot of nutrients in there and micronutrients,’ said Janine Burke-Wells, executive director of the North East Biosolids and Residuals Association. ‘And when you see what the material does for the soil, it is pretty amazing.’

Many environmental advocates have long been critical of sludge-based fertilizers because they can contain contaminants like heavy metals. Clint Richmond, toxics policy lead for the Massachusetts chapter of the Sierra Club, points out that there are other ’emerging contaminants of concern’ in sludge, like microplastics and pharmaceuticals, that are largely unregulated.

‘Even if biosolids were PFAS-free, I wouldn’t put it on my garden, let’s put it that way,’ Richmond said.”…