The removal of copper and zinc from swine wastewater by anaerobic biological-chemical process: Performance and mechanism

Copper and zinc are often used as feed additives and frequently detected in swine wastewater. Anaerobic granular sludge (AnGS) plays an important role in high-rate anaerobic methanation biotechnologies which are widely applied to treat swine wastewater. The removal of Cu2+ and Zn2+ by AnGS was investigated in the batch and continuous systems. The results of batch experiments showed the adsorption by AnGS could be a significant method for Cu2+ and Zn2+ removal with efficiencies of 99 % and 49 % respectively. The sulfide precipitation mediated by AnGS could be another significant pathway for Zn2+ removal with efficiency of 18-27 % in Protein/M2+ experiments and 16-46 % in SO42+/M2+ experiments (M2+ represents the total concentration of Cu2+ and Zn2+. The results of continuous experiment showed, with SO42+/M2+ larger than 1.5, the influent Cu2+ and Zn2+ could be effectively removed in an anaerobic methanation bioreactor and its effluent Cu2+ and Zn(2+)concentrations were below 1 mg/L and 2 mg/L separately. The main removal mechanism of Cu2+ and Zn2+ in the anaerobic methanation system was that the biological production of sulfide from sulfate was followed by chemical precipitation and reduction. It is helpful for the removal of Cu2+ and Zn2+ with organic pollutants simultaneously to eliminate environmental risk of swine wastewater.

Automated summary

Copper and zinc, common in swine wastewater, can be effectively removed by anaerobic granular sludge (AnGS) through adsorption and sulfide precipitation pathways. Batch and continuous experiments showed high removal efficiencies of 99% and 49% for Cu2+ and Zn2+ by AnGS, with the main mechanism being biological sulfide production followed by chemical precipitation and reduction.