Optimization Of Operating Conditions For Anaerobic Digestion Of Kitchen Waste

Kitchen waste is a kind of organic matters, which contains lots of nutrients such as glucose, protein, fat, etc. Due to its high moisture content, it cannot be burned directly. Sanitary landfill pretreatment skill will lead to incomplete degradation of organic matter, so it will cause pollution to the environment, even worse, it can also affect the underground water quality. The most unbearable problem is that the unpleasant smell it produces will affect the residents' living environment seriously, lower the living environment quality. The anaerobic fermentation technology, not only can solve the problem of the environmental pollution, but also can reduce the cost of enterprise operation. This paper was devoted to optimize the operating conditions for anaerobic digestion of kitchen waste. Firstly, the research was fouced on the optimization of the initial pH and hydraulic retention time (HRT) of two phase anaerobic digestion, by adjusting the initial pH value of the acid phase and detecting the TVFA/ethanol content, glucose and protein content of the effluent, the best initial pH of the acid phase was obtained, a batch experiment was used to test the methane production of the effluent of the acid phase, the same conclusion was got with the acid production experiment. What's more, the influence of the HRTs on the two-phase experiment was also investigated, and contrasted with the single-phase anaerobic digestion. Finally, the CSTR was used to investigate the digestion of the kitchen waste in a one-stage fermentation process, the inoculation sludge and temperature influence on the single-phase anaerobic digestion were studied, the best operation condition of the inoculation sludge and temperature was got. Main conclusions are as follows:(1) By the study of the initial pH influence on the two-phase anaerobic digestion of the kitchen waste, we concluded that the optimal initial pH of the acid phase is 8, the TVFA/ethanol production of the acid phase is 12.4 g/L, methane production rate of the methane phase is 421 mL/gTS, which was 18% higher than the methane yield at the experimental group at initial pH 4.(2) The batch-sequence experiment of the kitchen waste was investigated for the methane production, HRT was evaluated for efficient methane production, we concluded that the best combination was HRT of 5d for acidification phase and HRT of 15d for methane production phase, the methane production rate of this combination is 329.5 mL/gTS, followed by acidification phase (HRT of 3d) and methane production phase (HRT of 17d). The methane production rate of the anaerobic digestion in single-phase is lower than the above two kinds of combinations of HRT, but 17.8% superior to the combination of acidification phase (HRT of 2d) and methaneproduction phase (HRT of 18d).(3) In the research of the effects of the temperature and inoculation of mud on the single-phase anaerobic digestion, when the inoculum was obtained from the mesophlic condition, the increase of temperature did not affect the anaerobic digestion of methane production rate significantly. When the anaerobic digestion operated at high temperature, methane production rate with the thermophilic incoloume was obviously higher than that with the mesophilic incolume. The highest methane yield (641 mL/gTS) was obtained at thermophilic anaerobic digestion with the thermophilic incoloume, and it was 30% higher than the methane yield at the mesophlic anaerobic digestion with the mesophilic incolume.