Thanks Ali Ling for highlighting this excellent The New York Times article by Hiroko Tabuchi on PFAS in wastewater Biosolids and providing expert insight and commentary for context.
The links with PFAS, Biosolids and land application, is interesting and nuanced. It is indeed a fertiliser, and adds much needed humic content to mineralised soil. It’s highest value is its low entropy, structured organic matter.
The issue with contamination of milk via Biosolids to land in Maine was the subject of the documentary: “Sludge: A PFAS Uprising”. Terrible title, but good documentary.
On a Mass balance basis, at a rate of production of 7 million dry tonnes/yr in the US and at average rates of agronomic loading and land application, it would be applied to 1-2% of agricultural land annually. It’s just not moving the needle. Land application of animal slurries eclipses it, by over an order of magnitude.
It’s not a bad idea in principle. But it’s really low cost disposal. That’s what really drives it. The farmers can carry on without it, the water utilities would experience the disruption. In Europe, prior to a legislative ban on deep sea disposal, ships were filled, headed a mile offshore and emptied the hold. The Germans, who had very little access to this disposal option, lobbied hard for the ban.
It’s a good way to deal with 45% of Biosolids in the US, but isn’t really that significant in meeting nutrient requirements for ag.
Lobbying, supported by groups like Synagro led to adoption of the term “Biosolids” and definition of Class A and Class B. It’s good marketing: ‘Biosolids’ is a lot more palatable than the term ‘sewage sludge’. The water reuse community could learn a thing or two from this communications strategy.
Based on a risk-benefit analysis, it’s increasingly hard to support the case for continued land application as long as we have such a heterogeneous chemical cocktail going to our treatment plants.
Much of this partitions naturally, and via the treatment process, into wastewater Biosolids, including microplastics, antibiotic resistant bacteria, pharmaceuticals, endocrine disrupting compounds and yes, when it is present, also PFAS. If it was just human waste, it’s a very sustainable circular concept. It’s what happens in nature, but this is death by a thousand unknown unknowns.
The alternatives to land application and land fill will not be just incineration, it will be a crisis-driven market opportunity that will lead to the creation of unicorn water technology market opportunities for solutions with radical functionality. The probability just continues to increase, steadily, incrementally, year by year. Reminiscent of the millionaire in the Hemingway novel The Sun Also Rises, who was asked, “How did you go bankrupt?” to which he replied wryly, “Gradually, then suddenly“.
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