Lü Fan, He Pin-jing, Shao Li-ming
State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai, China.
J Environ Sci (China). 2006;18(4):805-9.
pH and volatile fatty acids both might affect the further hydrolysis of particulate solid waste, which is the limiting-step of anaerobic digestion. To clarify the individual effects of pH and volatile fatty acids, batch experiments were conducted at fixed pH value (pH 5-9) with or without acetate (20 g/L). The hydrolysis efficiencies of carbohydrate and protein were evaluated by carbon and nitrogen content of solids, amylase activity and proteinase activity. The trend of carbohydrate hydrolysis with pH was not affected by the addition of acetate, following the sequence of pH 7>pH 8>pH 9>pH 6>pH 5; but the inhibition of acetate (20 g/L) was obvious by 10%-60 %. The evolution of residual nitrogen showed that the effect of pH on protein hydrolysis was minor, while the acetate was seriously inhibitory especially at alkali condition by 45%-100 %. The relationship between the factors (pH and acetate) and the response variables was evaluated by partial least square modeling (PLS). The PLS analysis demonstrated that the hydrolysis of carbohydrate was both affected by pH and acetate, with pH the more important factor. Therefore, the inhibition by acetate on carbohydrate hydrolysis was mainly due to the corresponding decline of pH, but the presence of acetate species, while the acetate species was the absolutely important factor for the hydrolysis of protein.
pH值和挥发性脂肪酸都可能影响颗粒固体废物的进一步水解，而颗粒固体废物的水解是厌氧消化的限速步骤。为了阐明pH值和挥发性脂肪酸各自的影响，在固定pH值（pH 5 - 9）下进行了有无乙酸盐（20 g/L）的批次实验。通过固体的碳和氮含量、淀粉酶活性和蛋白酶活性评估碳水化合物和蛋白质的水解效率。碳水化合物水解随pH值的变化趋势不受乙酸盐添加的影响，顺序为pH 7>pH 8>pH 9>pH 6>pH 5；但乙酸盐（20 g/L）的抑制作用明显，抑制率为10% - 60%。残余氮的变化表明，pH值对蛋白质水解的影响较小，而乙酸盐具有严重的抑制作用，尤其是在碱性条件下，抑制率为45% - 100%。通过偏最小二乘建模（PLS）评估了这些因素（pH值和乙酸盐）与响应变量之间的关系。PLS分析表明，碳水化合物的水解既受pH值影响，也受乙酸盐影响，其中pH值是更重要的因素。因此，乙酸盐对碳水化合物水解的抑制主要是由于相应的pH值下降，但乙酸盐种类的存在也是原因之一，而乙酸盐种类是蛋白质水解的绝对重要因素。
