pH值对餐厨垃圾厌氧发酵产挥发性脂肪酸的影响

通过间歇实验研究了中温条件下pH值对餐厨垃圾厌氧发酵产挥发性脂肪酸(VFA)的影响.考察了pH值为5.0、6.0、7.0及不控制pH值下的有机酸浓度及组成情况.结果表明,当控制反应器中pH值为6.0时,餐厨垃圾水解酸化效果最好,比其他pH值条件下产生更多的有机酸.pH值为6.0时,VFA浓度与单位VS产酸量在第68h达到最大值,分别为40.89g/L和0.328gVFA/gVS,是不控制pH值时的8倍.pH值对发酵产物组成影响显著.不控制pH值时,反应器内的pH值在24h内由6.6迅速下降到3.8,乙醇为主要的发酵产物,占59.8%,表现为典型的乙醇型发酵.当控制pH值为5.0、6.0、7.0时,均为丁酸型发酵.但pH值为5.0时,乙酸为主要产物;pH值为6.0时,丁酸为主要产物;pH值为7.0时,乙酸与丁酸比例相当.试验表明,餐厨垃圾厌氧发酵产酸的最佳pH值为6.0.

Effect of pH value on VFA concentration and composition during anaerobic fermentation of kitchen waste

Under mesophilic conditions(35℃), batch experiments were carried out to determine the effect of pH value on volatile fatty acid(VFA) concentration and composition during anaerobic acidogenesis of kitchen wastes. The pH value was uncontrolled in one reactor and controlled at 5.0, 6.0, 7.0 in other reactors. The results showed that the greatest degree of hydrolysis and acidogenesis was obtained and more organic acid was produced when the pH value was controlled at 6.0. When the pH value was controlled at 6.0, the maximum VFA concentration and yields of 40.89g/L and 0.328gVFA/gVS was obtained in the 68th hour, and was 8 times of that when the pH value was not controlled. The product composition in the acid reactor strongly depended on the pH value. The pH value of the uncontrolled reactor dropped from 6.6 to 3.8 quickly within 24 hours. Ethanol was the main product, accounted for 59.8% of total end products. So the typical ethanol-type fermentation occurred when the pH value was not controlled. It was butyric acid-type fermentation when the pH value was controlled at 5.0, 6.0 and 7.0. Acetic acid was main product at pH 5.0, butyric acid was dominant at pH 6.0, proportion of acetic acid and butyric acid was similar to each other at pH 7.0. The optimum pH value of hydrolysis and acidogenesis of kitchen wastes was 6.0.