Study on a fixed zeolite bioreactor for anaerobic digestion of ammonium-rich swine wastes

► A fixed zeolite bioreactor was constructed. ► The ammonium was adsorbed via the fixed zeolite. ► Many microorganisms fixed on the surface zeolite. ► The bioreactor reduced the inhibition of high ammonium concentration. ► Start-up time decreased and methane production increased. In this study, a fixed zeolite bioreactor was developed for the anaerobic digestion of ammonium-rich swine wastes (NH4+-N=3770mg/l). To investigate the performance of the reactor, a sunken zeolite bioreactor and a bioreactor without zeolite were used as controls. The new bioreactor exhibited good performance, with startup time on the 14th day and methane production of 178.5ml/g-VS during all 32days of the experiment at 35°C. This bioreactor significantly shortened startup time, enhanced methane gas yield more than twofold and made COD removal more efficient than under the other models. Furthermore, it reduced the inhibition of high ammonium concentration during the anaerobic digestion of ammonium-rich swine wastes via effective ammonium removal and the immobilisation of microorganisms. Because of its simple structure and good performance, the fixed zeolite bioreactor can be recommended for future use.