Research Of Vfas Production Of Cassava Dregs By Countercurrent Anaerobic Fermentation

Cassava dregs is a kind of organic solid waste which is produced from industrial production and processing. Cassava waste contains large numbers of organic matter, a large numbers of carbohydrates can make the resource reuse. In this paper, research of producing acetic acid from cassava waste by countercurrent anaerobic fermentation, at the same time, to improve substrate decomposition and Reduce emissions。By changing the condition parameters of countercurrent anaerobic fermentation on the experiments, it can improve production and conversion of VFAs during countercurrent fermentation, and the degradation effect of cassava dregs, it also can ease inhibition of free acid to acid-forming bacteria. The result of study can provide a basic for realizing continuously, stably and high yield acetic acid.1. Comparing with the effects of VFAs production between countercurrent fermentation and conventional fermentation. After the process of countercurrent fermentation operating stably, the concentration of acetic acid and VFAs achieve2.11g/L and3.45g/L, respectively. Comparing with conventional fermentation process, the concentration of acetic acid and VFAs increased by56.2%and41.3%,respectively, the ratio of acetic increase by9.79%, the production of VFAs and acetic acid are increased by42.6%and41.6%, the conversion of VFAs and acetic acid are increased by40.8%and30.3%, the substrate decomposition on countercurrent fermentation is higher than conventional fermentation22.6%.2. Because of the different Stacking time and disposing method, the component of stale and fresh cassava dregs is different. Starch and carbohydrates of stale cassava dregs is higher than fresh cassava dregs. Two kinds of waste are disposed by countercurrent anaerobic fermentation, after the countercurrent is stable, the concentration of VFA and acetic acids of fresh cassava waste is3.45g/L and2.11g/L, but that of stale cassava dregs are1.75g/L and0.9g/L. the Substrate degradation rate, production of VFA, production of acetic acids of fresh cassava dregs are30.1%,0.08gVFA/gVSfed,0.51gAC/gVSfed. the Substrate degradation rate, production of VFA, production of acetic acids of fresh cassava dregs are13.2%,0.04gVFA/gVSfed,0.23gAC/gVSfed. The production of VFA and Substrate degradation rate of fresh cassava waste is higher than stale cassava dregs.3. The effects of VFAs production from cassava dregs during countercurrent fermentation under high concentration of substrate is better than low concentration of substrate. But when the concentration of substrate is higher than80g/L, the concentration of VFAs and acetic acid have ai little change. When under a low concentration, microorganism can make full use of cassava dregs. The ratio of acetic acid reach69.2%when the concentration of substrate is80g/L, after it increased to100g/L the VFAs production and conversion, the decomposition of cassava dregs, the ratio of acetic acid will deduce. Countercurrent fermentation is good for accumulation of VFAs. The inhibition of free acid to microorganism will be stronger and stronger with the increased of substrate concentration during countercurrent fermentation.4. SRT is a important factor on countercurrent fermentation. When SRT is12d, the countercurrent fermentation process is better for producing VFAs. The concentration of VFAs and acetic acid are6.8g/L and4.8g/L, respectively, when the SRT is grater or less than12d, the concentration of VFAs and acetic acid will reduce. The decomposition of cassava waste will be better and better with the growth of the SRT, and some material which is hand to degradation may be used after a long time contracted with microorganism. When the SRT is longer than a certain time, the concentration of VFAs and acetic acid will reduce, the production and conversion of VFAs and acetic acid will also reduce.