CDM Smith and WEF breakdown PFAS in biosolids

I think it’s really important for the public to understand that PFAS is ubiquitous in the environment. You can find it in the dust in your household, it’s in the carpeting, it’s in the fabrics on your chairs and couches. It’s in waterproof jackets, in non-stick pans, in your dental floss, it’s in all the fast food packaging. You’re in contact with these compounds every day. Wastewater treatment plants, wastewater recovery facilities, we’re receivers of these compounds, we’re not generators.

Source control is certainly the first step. The treatment that we’ve seen today has primarily been on the drinking water side. We haven’t really seen treatment on the wastewater side yet, but it’s coming. We’ve seen states like Mass­a­chu­setts, Colorado, Michigan, California, starting to put PFAS monitoring require­ments for influent/effluent and biosolids in their permits. As utilities, we need to understand where the PFAS is coming from in your system and go out and perhaps test the industries that are in your industrial pretreat­ment program to see if they have or are contribut­ing PFAS to you. Some utilities are doing this to great success. We need to understand if it is in your plant, what do you do? You need to test your leachate, your septage, as well. We like to focus on separate, concentrate and destroy as our mantra for PFAS. So if you can find the source and separate and concentrate and destroy it there, it’s much more economical than waiting for it to come to your plant. If it is in your plant, we’ve done some interesting work with our WRF project 5031 that is looking at the occurrence of and fate and transport of PFAS through wastewater treatment plants. One of the things we’re looking at there is the mass balance of fluorine across the plant. One of our theories is that potentially this PFAS is concen­trat­ing in the scum at a wastewater treatment plant. Because of its hydrophobic/hydrophilic nature, it tends to be more of a surfactant. In your aeration basins you could actually be separating the PFAS into that scum layer. So, if you manage that scum layer a little differently and not put it in your biosolids for ultimate disposal, perhaps that’s where we can concentrate and destroy a smaller volume than managing it in your biosolids. 

The mantra was separate, concentrate, destroy.

What we’ve found in our testing to date through not only WRF 5031 work but also through work that CASA has done in California collecting samples. Again, PFAS is ubiquitous in biosolids. Anywhere we test for it, we typically find it.  But the issue is what happens to those compounds in the biosolids, especially if they’re land applied. In our WRF 5042 project, we looked into this with a bench scale study of seven biosolids that are land applied in mezzo columns that we built and let the natural rainfall permeate through these mezzo columns. We collected the leachate and tested that and what we did find was that PFAS was traveling through the columns and coming out in the leachate. The question is, at those low concen­tra­tions, is it harmful to the environment, can it be detected in the groundwater, can it be uptaken by the plants. We don’t know those answers yet. We did see there was some trans­for­ma­tion of precursors in the biosolids to PFAS so that was an interesting outcome of that study. 

The impact is huge. I’m based in Mass­a­chu­setts so these Maine regulations directly impact a lot of utilities in the New England area. I think what is important about this legislation is that you’re banning the use of biosolids that contain PFAS in land application, unless it can be shown that the biosolids are PFAS free.  My question is, what does PFAS-free really mean? First of all there is not a standard method yet approved for sampling for PFAS in biosolids. And second of all, are we talking zero parts per trillion? What’s the detection limit?  Our outlets for biosolids are really shrinking. The landfills are at capacity, the incin­er­a­tors are being shut down. If land application is also banned, I don’t know where our biosolids will go. 

The study of PFAS is an evolving science, we don’t even know how many compounds fall under the PFAS umbrella.  Right now, in terms of gaps, it’s the destruction tech­nolo­gies. We need to get these compounds out of the environment. The processes right now are very energy intensive. Finding a destruction technology that is not so energy intensive would be key. The second is the fate and transport of PFAS in the land application of biosolids. Looking at fields that have had land applied biosolids for a number of years and testing the groundwater, under­stand­ing the precursor trans­for­ma­tion, under­stand­ing the leach­a­bil­ity because it depends on the soil types, even. And also under­stand­ing the plant uptake, is it being taken up by the plants and then being consumed.