进料频率对餐厨垃圾与剩余污泥中温共发酵系统稳定性的影响

考察系统负荷(以COD计)为11.36 g·(L·d)-1时,6种不同进料频率下,餐厨垃圾和剩余污泥中温厌氧共发酵过程中产气量、气体组分、SCOD、pH和挥发性脂肪酸(VFAs)的变化,旨在明确进料频率对系统稳定性的影响,同时结合单一VFA的产甲烷动力学特性,探明系统不稳定的原因。结果表明,进料频率较高时,进料周期内系统的气体组分、SCOD和pH无明显变化,产气量呈线性增长,且基本无VFA积累。随着进料频率降低,进料初期过快的水解酸化导致SCOD和VFAs浓度呈现明显的先升高后逐渐降低的趋势,从而导致pH和甲烷含量波动明显。当进料频率为1 次·d-1时,系统中pH降至7.5,甲烷含量降至45.4%,丙酸占总有机酸的比例最高可达87.9%。相比乙酸而言,丙酸在甲烷化过程中存在的延滞期(1.21 h)及较低的甲烷化速率(5.01 mL·h-1)可能是导致存在丙酸积累的低频进料系统中稳定性较差的原因之一。

Effect of feeding frequency on stability of mesophilic co-digestion of food waste and waste activated sludge

In order to know the effects of feeding frequency on stability of co-digestion of food waste and waste activated sludge, the variation of biogas production, biogas composition, SCOD, pH and VFAs were investigated at 6 different feeding frequency under OLR(calculated by COD) of 11.36 g·(L·d)-1. Meanwhile, the kinetic characteristics of methanogensis of individual VFA were also analyzed to know the reason for instable performance. Results showed that in a feeding period, the variation of gas composition, SCOD and pH were not significant, biogas production increased almost linearly without VFA accumulation at the high feeding frequency. With the decrease of feeding frequency, the fast hydrolysis and acidogenesis led to the increase of SCOD and VFAs concentration at the beginning of the feeding period, then gradually decreased, and resulted in the significant fluctuation of pH and methane percentage in biogas. At the feeding frequency of 1 d, pH declined to 7.5, the content of methane dropped to 45.4%. The concentration of propionic accounted for 87.9% of TVFA. Compared with acetate, the lag time (1.21 h) and lower rate (5.01 mL·h-1) of methanogenesis of propionate should be one reason for instable performance of low feeding frequency system.