Anaerobic Treatment Of Sulfate Laden Wastewater With Simultaneous Removal Of Hydrogen Sulfide Using Biochar

Abstract

This study examined the use of biochar to alleviate sulfide toxicity during anaerobic treatment of high strength sulfate-rich wastewater with concomitant recovery of sulfur. At the highest sulfate concentration tested (6,000 mg SO42-/L), the unionized dissolved sulfide (DS) of 131 mg S/L resulted in built-up of total volatile fatty acids concentration up to 3,500 mg/L as acetic acid (HAc), and the reactors were on the verge of failure. Upon integrating biochar columns with anaerobic reactors, sulfide was rapidly removed with removal efficiencies >98% of gaseous H2S, 94% of DS and 89% of free sulfide, thereby alleviating sulfide toxicity to methanogens (MPA) and sulfate reducing bacteria (SRB) and promoting the stability of the anaerobic process. 16S rRNA gene sequencing analyses revealed that after the removal of H2S by biochar, the RA of MPA (Methanobacterium and Methanosaeta) increased from 0.7% to 3.7% in R1, 0.7% to 2.2% in R2 and 0.4% to 2.2% in R3, while the relative abundance of SRB (Desulfovibrio decreased from 9.3% to 6.3% in R1, 9.1% to 1.7% in R2 and 4% to 0.5% in R3 indicating the anaerobic treatment was quickly recovered to stable state.