Investigation of Key Parameters for Bioremediation of PFAS in Biosolids Using Acidimicroibum Sp. Strain A6

Abstract

Acidimicrobium sp. Strain A6 (A6) has been shown to defluorinate per- and polyfluoroalkyl substances (PFAS), coupled with the Feammox reaction under anaerobic conditions. The A6 has great potential for application in industry as a bioremediation method, but challenges in implementing A6 bioremediation in environmental settings include exposure to a wide range of temperatures, and also the necessity of a Fe(III) source. A 60-day fully-liquid incubation experiment was conducted to investigate the temperature dependence of the reaction, in addition to a 40-day biosolid-slurry incubation using three biosolids with varying iron content to investigate the bioavailability of pre-existing iron for A6. Previous work with A6 has always been conducted at room temperature, but this is not representative of environmental conditions. The results show that A6 bacteria is highly influenced by temperature, showing low activity at 10 and 15 \(^{o}\)C. Significant ammonium oxidation and A6 number growth were exhibited at 20 and 28 \(^{o}\)C. Previous experiments show that iron is typically the limiting reagent in the Feammox reaction and requires continuous reapplication during incubations. The biosolid-slurry incubations showed significant growth in A6 numbers in high-iron biosolids and no/little growth in low-iron biosolids, which is the first demonstration of A6 grown using pre-existing iron in media without an added Fe(III) source. This research sheds light on the different pathways in A6 for bioremediation. The temperature experiment reveals potential geographic or seasonal constraints of A6 due to low activity at lower temperatures. The iron experiment reveals biosolids from wastewater treatment plants that use iron in treatment processes could be a potential candidate for economical and efficient A6 bioremediation by stimulating A6 growth without requiring the addition of massive amounts of Fe(III).