Research On Efficient Technology Of Biogas Production By Organic Solid Wastes In Rural Area

With the vigorous development of the planting and breeding in recent years, the rural living conditions was improved significantly. However, people only pay attention to the economic development, ignoring the environment problem in the process, The relations between economy and environment can not coordinate to balance, causing serious pollution in the countryside. The pollution is mainly derived from the rural organic solid wastes (such as straw, livestock and poultry manure and eat hutch garbage), which are not disposed properly.According to current situation of the rural, this article take the straw as the main raw material, research methanogenesis process conditions and process parameters by two-phase anaerobic digestion technology, which studied the hydrolysis acidification process, methanogenesis process, and two-phase anaerobic process, respectively. The main research contents and conclusions are as follows:Hydrolysis acidification process:Having investigated the optimal fermentation conditions in the hydrolytic acidification phase, this part mainly studied fermentation temperature, fermentation patterns (the wet, half dry type, dry type fermentation), and the change of organic acids and soluble COD in the hydrolysis acidification process. The experimental results show that:For wet fermentation, within the scope of the fermentation temperature 20℃ to 40℃, with the increase of fermentation temperature, the VFA concentration also gradually rise, It is butyric acid type fermentation; For half dry fermentation, fermentation temperature in 20℃-35℃ range, produce acid phase VFA concentration as the temperature rises, but the acid production of 40℃ can not increase again, make produce acid concentration is lower than 35℃, so the biggest produce acid fermentation temperature is 35℃ for half dry, the fermentation type of butyric acid type fermentation; For dry fermentation, the fermentation temperature 20℃-30℃ range, produce acid phase with VFA concentration fermentation temperature rises, but fermentation temperature 30℃,35℃ and 40℃, VFA concentration did not increase with the increase of temperature, temperature 30℃ as the best produce acid, and fermentation types is propionic acid.Exploring the cycle time of three fermentation type in the acidogenic phase, the cycle time of three fermentation type is 5 days, in the 5 days three type fermentation produce VFA concentration was highest, they are 1623.09mg/L,4284.05mg/L,4986.94mg/L. In the circulation process of three fermentation type experiments, from the change about the concentration of COD, VFA, which is produced by unit VS, we can concluded that:half-dry fermentation can produce the higest concentration of COD and VFA on unit VS, the Acid production rate is also the fastest speed, they are 195.11mg/gVS and 71.40mg/gVS.Methane-producing phase:Research in study the effect of small amplitude temperature changes on biogas production between the temperature range (30℃ to 37℃), it results show that:from each nissan volume、cumulative gas、cumulative gas production rate and methane content etc point of views to analysis the two phase anaerobic fermentation performance, it is concluded the 35℃ is superior to the 33 and 30 ℃, the accumulative total volume of 35℃ compared to 33℃ and 30℃ increased by 31.07% and 169.88% respectively. This shows that methanogens is more sensitive to temperature, reduce 2℃ or 5℃ will have inhibitory effect on it.Small amplitude temperature change is studied on the influence of the gas phase microorganisms, it is conclueded that 35℃ group not only advantage bacteria number, but microbial diversity and evenness were greater than the other two groups from the DGGE electrophoresis、similarity clustering analysis、 and microbial diversity from three aspects, clarifying the small temperature lowering the mechanism of reducing methane production,two-phase anaerobic fermentation:hydraulic retention time on the influence of acid and methane-producing phase, it is concluded that:comparing the hydraulic retention time 3 and 4.5 days of the experimental group, the hydraulic retention time 3 days while the removal rate of VFA, methane content is lower than the hydraulic retention time of 4.5 days of the experimental group, but they only have small difference, More importantly, hydraulic retention time of 3 days of the experimental group accelerated the dissolution rate of VFA acidification phase and the gas production is the largest, and reached 4.9L, it was higher than the other two experimental groups 6.24% and 58.57%, respectively, it is also can draw when the hydraulic retention time of 1.5 days fermentation system is not stable, gas methane-producing phase can’t be stable.