Treatment of acidic gangue leaching wastewater by electrocoagulation combined with SRB

Coal gangue, a solid waste from coal mining, contains sulfide minerals that oxidize with oxygen and water to produce sulfuric acid, leading to acidic leachate. This leachate, rich in acidic substances and heavy metals, contaminates water sources through runoff or precipitation. To address this, a treatment system combining electrocoagulation and sulfate-reducing bacteria (SRB) was developed. Pine needles, used as a slow-release carbon source, replaced traditional carbon sources for microbial growth and metabolism. The system's key parameters included an electrode spacing of 6.5 mm, a current density of 25.0 mA/cm2, a reaction time of 29.5 min, 500 g of pine needles, 260 mL of SRB inoculum, and a daily water intake of 1,300 mL. Over 60 days, water samples were analyzed every 2 days for efficiency and microbial structure. Pine needles effectively released carbon, sustaining microbial activity. Removal rates for total iron (TFe), Mn2+, Zn2+, and SO42− were 99.5, 95.22, 99.60, and 79.59%, respectively, with effluent pH stabilized between 7.0 and 8.0. Key microbial taxa, including Clostridium, Lutispora, and Citrobacter, decomposed organic matter and reduced sulfate, enhancing treatment efficiency. This integrated system efficiently treated acidic coal gangue leachate, meeting discharge standards. It mitigates environmental impacts and provides significant environmental and economic benefits.