Partial least square modeling of hydrolysis: analyzing the impacts of pH and acetate

摘要

pH and volatile fatty acids both might affect the further hydrolysis o f particulate solid waste, which is the limiting-step of anaerobic digestion. To clarify the individual effects of pH and volatile fatty acids, batch experiment s were conducted at fixed pH value (pH 5—9) with or without acetate (20 g/L). T he hydrolysis efficiencies of carbohydrate and protein were evaluated by carbon and nitrogen content of solids, amylase activity and proteinase activity. The tr end of carbohydrate hydrolysis with pH was not affected by the addition of aceta te, following the sequence of pH 7>pH 8>pH 9>pH 6>pH 5; but the inhibition of ac etate (20 g/L) was obvious by 10%—60 %. The evolution of residual nitrogen show ed that the effect of pH on protein hydrolysis was minor, while the acetate was seriously inhibitory especially at alkali condition by 45%—100 %. The relations hip between the factors (pH and acetate) and the response variables was evaluate d 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 mor e important factor. Therefore, the inhibition by acetate on carbohydrate hydroly sis was mainly due to the corresponding decline of pH, but the presence of aceta te species, while the acetate species was the absolutely important factor for th e hydrolysis of protein.