Effect of shocked nitrobenzene concentrations on the operational performance of anaerobic sequential batch reactor

Two lab-scale anaerobic sequence batch reactors (ASBRs), respectively fed with 5 mg L-1 (R1) and 200 mg L-1 (R2) of sulfate were set up in this study. A mixture of the volatile fatty acids (VFAs) containing acetate and propionate was provided as electron donors. The effects of the influent nitrobenzene (NB) concentrations and the external electron acceptor of sulfate on the operational performance of ASBRs were investigated. The results indicated that NB reduction, sulfate reduction and propionate degradation were inhibited or further terminated in response to a shocked influent NB concentration of 50 mg L-1, i.e., 32 g m(-3) day(-1). However, these biological activities in ASBRs could be reversibly resumed so long as the influent NB regained below 30 mg L-1. The insufficient propionate was the main electron donor for the simultaneous reductions of NB and sulfate. Sulfate can energetically compete with NB for propionate as a co-substrate, resulting in the better performance of reactor R1 than that of R2. In engineering applications, the influent loading rates of pollutants should be safely declined below toxic thresholds to avoid the failure of system operation. (c) 2017 American Institute of Chemical Engineers Environ Prog, 37: 712-718, 2018