Distribution and degradation of Bisphenol A (BPA) substitutes BPAF and BPS compared to BPA in aerobic soil and anaerobic

Recently, worries regarding BPA’s known endocrine disrupting potential encouraged the development of alternative chemicals such as bisphenol AF (BPAF) and bisphenol S (BPS). As their names suggest, BPS and BPAF have similar structures to Bisphenol A, which has been used for a variety of purposes. However, BPS and BPAF also have the potential to be endocrine disrupting chemicals (EDCs). Unlike BPA, little is known about their persistence of the alternatives once they enter the environment or in the wastewater treatment process. The present research pursued evaluating the partitioning behavior of BPA, BPS and BPAF and their degradation in aerated soil and anaerobic sludge from a wastewater treatment system. BPA and the alternative BPA analogues have two ionizable acid groups (pKa value range ∼ 7.4 to 10.4), thus exist as an anion or a neutral molecule in the environment depending on pH. Measured octanol-water distribution coefficients of the neutral forms followed: BPAF > BPA > BPS. For adsorption isotherms on four different soils with varying soil properties, organic matter (OM) was the primary factor controlling sorption with sorption increased in the soil pH range investigated (4.3-8.6) with increasing OM. Soil pH had only a secondary role since the neutral species dominated at range of most soil pH. Unlike the trends with, BPS had a higher sorption affinity than BPA. In anaerobic sludge, no degradation of any of the three bisphenols was observed during the 4-week incubation study under methanogenic conditions. Loss of bisphenols from the solution phase was due to sorption to the sludge solids with the following affinity: BPAF > BPA > BPS. This means that the substitutes will persist during treatment and as their uses increase, their concentrations will increase in solid residuals. In aerobic degradation studies conducted in the two slightly acidic soils containing different % organic matter, half-lives for both BPA and BPS were less than one day whereas BPAF persisted much longer with half-lives of 22-36 days. Although BPA degrades quickly under aerobic conditions, the impact of BPA has been a concern due to its high loading to the environment from massive production and potential harmful effects. Replacement of BPA by its alternatives may lead to similar concerns and impact especially for the more persistent BPAF. This study reduced the data gaps that existed by quantifying the behavior of BPS and BPAF in soils as well as estimating the fundamental properties necessary to predict the environmental fate and transport of these alternatives.