Development of a bio-zeolite fixed-bed bioreactor for mitigating ammonia inhibition of anaerobic digestion with extremely high ammonium concentration livestock waste

A novel bio-zeolite fixed-bed bioreactor combining with physicochemical and biological methods for mitigating ammonia inhibition was developed to improve the anaerobic digestion of ammonium-rich livestock wastes. The fixed-bed bioreactor was constructed by zeolite that was fixed using three different kinds of polymer materials including chlorinated polyethylene (CPE), polymer foaming sponge (PFS) and porous nylon (PN). Using ammonium-rich swine wastes (NH4+-N: 7511 mg/l) as substrate, a series of batch anaerobic fermentation experiments were carried out under 35 °C. The bioreactor suspending with CPE fixed zeolite showed the shortest start-up period (2 days) and the highest methane production (about 96 times higher than that of the Control) after 30-days anaerobic digestion. Furthermore, the higher and stable methane concentration and yield during 100-day of semi-continuous anaerobic digestion clearly indicated the long-term practical effectiveness of CPE-fixed zeolite bioreactor. Synergy of ammonia adsorption and microorganism immobilization by CPE fixed zeolite contributed to the enhanced anaerobic digestion efficiency. The developed novel CPE fixed zeolite bioreactor was suggested to be a favorable system for improve the anaerobic digestion of ammonium-rich agricultural wastes.