PFAS inhibited sulfamethoxazole removal by regulating biofilm metabolisms on biological activated carbon

Activated carbon (AC) filtration is an effective technique to remove emerging contaminants in drinking water treatment plants. Adsorption onto AC and biodegradation by biofilm are two main mechanisms for the removal of emerging contaminants such as antibiotics. However, the effects of highly bioaccumulative and toxic poly- and perfluoroalkyl substances (PFAS) on antibiotic removal by AC filtration have not been well-understood. In this work, two AC columns were built and operated for 434 days to study the effects of ng-level PFAS on the removal of sulfamethoxazole (SMX). The results showed that 100 ng/L PFAS significantly decreased the removal rate of 1 μg/L SMX from 78.8 % to 71.7 %. Trace PFAS decreased the abundances of ammonia monooxygenase and nitrite-oxidizing bacteria, thus repressing nitrification co-metabolism process. Meanwhile, trace PFAS inhibited tricarboxylic acid (TCA) cycle by preventing pyruvate from generating acetyl-CoA, reducing energy supply for co-metabolism process. On the other hand, inhibiting TCA cycle led to a redirection of carbon from growth into polysaccharide intercellular adhesin biosynthesis. Trace PFAS also increased glutamate synthase and glutamine synthetase abundances, which promoted biofilm formation and then hindered SMX adsorption by AC. This study provides new insights into the adverse role of PFAS in antibiotic removal by AC filtration.