Quinone-mediated Sb removal from sulfate-rich wastewater by anaerobic granular sludge: Performance and mechanisms

Antimony (Sb) is a typical pollutant in sulfate-rich industrial wastewater. This study investigated the Sb removal efficiency in sulfate-rich water by anaerobic granular sludge (AnGS) and the stimulation of amended anthraquinone-2-sulfonate (AQS). Results showed that 89.0% of 5 mg/L Sb(V) was reduced by AnGS within 24 h, along with the observed first accumulation (up to 552.2 mu g/L) and then precipitation of Sb(III); coexistence of 2 g/L sulfate inhibited the removal of Sb(V) by 71.4% within 24 h, along with gradual accumulation of Sb(III) by 3257.4 mu g/L, indicating the potential competition of adsorption sites and electron donors between Sb(V) and sulfate. Amendment of 31 mg/L AQS successfully removed the inhibition from sulfate, contributing to 99.5% Sb(V) removal and minimum Sb (III) accumulation in Sb(V) + sulfate + AQS group. Further test results suggested that Sb(V) removal by AnGS was mainly through dissimilatory reduction instead of bio-sorption, while Sb(III) removal mainly relied on instant bio-sorption by AnGS followed by precipitation in the form of Sb2O3 and Sb2S3. Extracellular Polymeric Substances (EPS) characterization showed that AQS promoted the accumulation of Sb(V) and Sb(III) in EPS. High-throughput sequencing analysis showed the enrichment of sulfate-reducing bacteria (SRB) in Sb(V) + sulfate group and suppressed SRB growth in Sb(V) + sulfate + AQS group.

Automated summary

This study investigated the efficiency of antimony (Sb) removal in sulfate-rich water using anaerobic granular sludge (AnGS) and the impact of amended anthraquinone-2-sulfonate (AQS). The results showed that the coexistence of sulfate inhibited the removal of Sb(V) but AQS successfully removed this inhibition. Further tests indicated that AnGS removed Sb(V) through dissimilatory reduction and Sb(III) through bio-sorption and precipitation.