Study On Batch Process With Two-Phase Anaerobic Digestion For Urban Organic Waste

The decomposable organic wastes, included in town waste, are naturally decomposed in the environment. It leads to lots of organic pollutants, which pose a direct hazard to the environment of the town. At the same time, organic wastes have some characters, such as low heating value, putrescibility and rich content of organic mass etc. Due to the characters, anaerobic fermentation treatment of organic wastes is considered as a practical and feasible developing direction. In the paper two-phase anaerobic digestion process was employed to treat the town organic waste. This paper mainly researched several aspects as follows:①We respectively researched the influences of several ways on hydrolysis and dissolution of acidogenic phase, such as anaerobic spaying/anaerobic immersion, anaerobic immersion/aerobic alternation, anaerobic immersion/anoxic alternation and anaerobic immersion with UASB effluent of the methanogenic phase. At the same time, we also researched the dissolution rules of organic wastes added excrement of pigs. The experiments showed that anaerobic immersion with UASB effluent was optimal for the promotion of organic components dissolution effect. The suitable period for dissolution was 7 days, while the concentration of dissolved COD was on the order of 25140～6790mg/l. The dissolution rules of organic wastes added excrement of pigs accorded with the dissolution rules of organic wastes. Simply, during the last phase of dissolution, the concentration of dissolved COD was smaller along with the proportional rising of excrement of pigs.②By means of experiments, we researched the startup of UASB reactor. The experiments showed that digestion sludge, through single-phase anaerobic reactor domestication, was inoculated and cultivated step by step. During 60-day time, the startup of the methanogenic phase UASB reactor was realized. The volume load increased to 9.4±0.2kgCOD/m3.d and the removal rate of COD was above 80%. At the same time, granular sludge blanket was formed. During the startup process, the pH value of UASB reactor effluent was kept between 7.50 and 8.35; while the alkalinity of effluent was kept between 1457 and 3580mg/l. The results indicated that the treatment system had a strong buffering capacity to acid and alkali. The concentrations of VFA and NH4+-N were 249.6～2813.2 mg/l and 94.8～301.9mg/l, respectively, which would not influence the normal operation of the system.