Biogenic sulfur recovery from sulfate-laden antibiotic production wastewater using a single-chamber up-flow...

The high-concentration sulfate (SO₄^2-) in the antibiotic production wastewater hinders the anerobic methanogenic process and also proposes possible environmental risk. In this study, a novel single-chamber up-flow anaerobic bioelectrochemical reactor (UBER) was designed to realize simultaneous SO₄^2- removal and elemental sulfur (S⁰) recovery. With the carbon felt, the cathode was installed underneath and the anode above to meet the different biological niches for sulfate reducing bacteria (SRB) and sulfur oxidizing bacteria (SOB). The bio-anode UBER (B-UBER) demonstrated a much higher average SO₄^2- removal rate (SRR) of 113.2 ± 5.7 mg SO₄^2--S L^-1 d^-1 coupled with a S⁰ production rate (SPR) of 54.4 ± 5.8 mg S⁰-S L^-1 d^-1 at the optimal voltage of 0.8 V than that in the abio-anode UBER (control reactor) (SRR = 86.6 ± 13.4 mg SO₄^2--S L^-1 d^-1; SPR = 25.5 ± 9.7 mg S⁰-S L^-1 d^-1) under long-term operation. A large amount of biogenic S⁰ (about 72.2 mg g^-1 VSS) was recovered in the B-UBER. The bio-anode, dominated by Thiovirga (SOB genus) and Acinetobacter (electrochemically active bacteria genus), exhibited a higher current density, lower overpotential, and lower internal resistance. C-type cytochromes mainly served as the crucial electron transfer mediator for both direct and indirect electron transfer, so that significantly increasing electron transfer capacity and biogenic S⁰ recovery. The reaction pathways of the sulfur transformation in the B-UBER were hypothesized that SRB utilized acetate as the main electron donor for SO₄^2- reduction in the cathode zone and SOB transferred electrons to the anode or oxygen to produce biogenic S⁰ in the anode zone. This study proved a new pathway for biogenic S⁰ recovery and sulfate removal from sulfate-laden antibiotic production wastewater using a well-designed single-chamber bioelectrochemical reactor.