Acidogenic Fermentation Of Municipal Sludge In Combination With Food Waste For The Production Of Organic Acids

Municipal sludge and food waste are both solid waste of high value. Sludge co-digestion with food waste can increase the concentration of the volatile fatty acids (VFA) the target production, improve the rate of degradation of the substrate concentration and conversion rate of VFA, promote acid production industrialized feasibility . Results were shown as follow:1) The effect of C/N on bio-production of organic acids by anaerobic co-digestion of food waste and sewage sludge. The sludge and food waste fermented in accordance with TS ratio of 75%: 25%, 50%: 50% and 25%: 75%,as the C/N in 6:1 to 34:1 among five different ratio. The results showed that the addition of food waste at a proper rate can improve the substrate degradation and the bio-production of VFA. When the food versus sludge is 1:3, the volatile solid degradation rate increased by 23.5% and the VFA yield increased by 18.8% compared to the sludge fermentation. Meanwhile, the shift of C/N can also influence the distribution of the VFA. A low C/N is inclined to acetate accumulation, but a higher C/N cause the butyrate accumulation. When the pH of fermentation changed, the neutral and slight acid condition will lead to a better VFA bio-production. These results provide useful clues for the industrial application.2) The effect of VS concentration and a two-stage fermentation on acid production process. Different organic load were studied when the food versus sludge is 1:3 ,to produce more acetic acid in the process. That high concentrations of feed can effectively improve the VFA concentration and acetic acid ratio. High substrate degradation and acid production rate were achieved at the conversion rate of VS = 80 g ? L-1. Two-stage fermentation proved that acid production process should be controlled in a short fermentation period (6-8 days).3) The sludge and food waste were mixed and fermented by biogas production inhibition means. The sludge and food waste were mixed and fermented, and the impact on the composition and concentration of VFA, the substrate degradation and methane gas production potential by three gas production inhibition means were studied. The results indicate that the fermentation gas production can be effectively inhibited by the BES, chloroform, pH = 10.These three conditions can also enhance the products acid conversion rate, and pose a certain impact on the composition of acid production .