Abstract
Anaerobic digestion is an important technology for production of renewable energy from municipal solid waste (MSW). An MSW anaerobic digester usually transforms 70% of charged MSW to biogas and generates 30% residue. Wastewater containing high concentrations of ammonia is also produced. The necessary treatment of those residual materials reduces the overall economic efficiency of anaerobic digesters. We established hyper-thermophilic (80°C) anaerobic digesting sludge that includes more than four hyper-thermophilic microbes from hot springs. Hydrolysis enzyme activity tests revealed that hyper-thermophilic sludge solubilized MSW four-times faster at 80°C than anaerobic digestion sludge at 55°C. The total effects of this sludge were tested using a semi-continuous feed bench-scale digester. Results show that the digestion rate improved 4.3% and ammonia concentration of wastewater was lowered to half by ammonia stripping. The temperature and pH of hyper-thermophilic hydrolysis were suitable for ammonia stripping. Microbial flora of this hyper-thermal digester were characterized using PCR-DGGE. Some species of thermophilic bacteria were found from hyper-thermal hydrolytic sludge at 80°C, which do not usually exist in anaerobic digesters at 37°C or 55°C.
