Study On The Effect Of Intermediate In Dry Anaerobic Digestion

Dry anaerobic digestion has great commercial prospects, which has much more advantages than wet anaerobic digestion. However, there are still many problems to be solved:such as mass transfer problem, startup time, stable gas, etc. It’s worth to note that the stability of the system depends on the activity of bacteria participating in the digestive process. In this work, the specific microorganisms in anaerobic digestion in different conditions were detectde using fluorescence in situ hybridization (FISH). The effect of intermediate to produce methane in dry anaerobic digestion process was explored. Meanwhile, the relationship of VFAs and the corresponding microorganisms was analyzed. In addition, the influence of VFAs, which include acetic acid, propionic acid and butyric acid, to the sulfate reducing bacteria in anaerobic digestion was also investigated. The main results of this study were as follows:(1) The optimal amount of acetic acid added was10.5g every other day for eight times till to the stability stage. This could avoid inhibiting the active of microbial community, produce more biogas, and short the startup time of anaerobic digestion. The average population of the H2-utilizing methanogen was more than the acetate-utilizing methanogen. At the start-up of the experiment the population of H2-utilizing methanogen increased to the maximum and decreased sharply. At stable stage the level of H2-utilizing methanogens was very low, in contrast, the population of acetate-utilizing methanogen increased. The relationship of the content of acetic acid with the population of H2-utilizing methanogen and acetate-utilizing methanogen were all negative linear with the coefficient of0.8658and0.8074, respectively, when the content of acetic acid was0-25g·L-1.(2) The optimal amount of propionic acid added was10.5g every other day for six times. Under such condition, biogas production quantity was larger than other reactors, which could promote the growth of methanogens. The relationship of the content of propionic acid and the population of Syntrophic propionate-oxidizing bacteria were negative linear with the coefficient of0.8352, when the content of propionic acid was0-100g·L-1. Meanwhile, concentration of propionic acid in0to30g·L-1was accompanied by the higher level of Syntrophic propionate-oxidizing bacteria.(3) The optimal amount of butyric acid added was4.8g every other day for six times. This could increase the activity of methane bacteria. The relationship of butyric acid and Syntrophic butyrate-oxidizing bacteria were positive linear with the coefficient of0.7229, when the content of butyric acid was0-2.4g·L-1. The relationship of the content of acetic acid and the population of Syntrophic butyrate-oxidizing bacteria were positive linear with the coefficient of0.8100, when the content of acetic acid was0-30g·L-1. It indicated that the correlation between concentration of acetic acid and the microbial involved in the response was better.(4) Added the optimal amount of acetic acid, propionic acid, butyric acid, the contribution of VFAs to reduction rate of SRB was investigated, results showed: acrylic acid> butyric acid> acetic acid. The evolution of populations of SRB and MB was monitored by using FISH technology in the reactor by adding different VFAs, studies showed that the activity of MB and SRB in the reactors was additional butyric acid> additional acetic acid> additional propionic acid> controls. Adding a certain amount of propionic acid was more advantageous to activate the activity of SRB, promote the transformation of propionic acid, enhance synergy of SRB and MB, improve the ability of against the rancidity.