Effect of pH on Cell Yield of Anaerobic Granular Sludge

The methane production rates and methane conversion ratios at six different alkalinity levels were obtained with anaerobic sequencing batch reactor (ASBR), glucose was fed as carbon source, and NaHCO₃ was added into the influent in order to make sure that the ratios of COD / Alk was between 1.0:1 and 4.8:1. The results indicated that the methane production rate and methane conversion ratio, at pH lower than 6.5, decreased by 8% ~ 10% compared to neutral pH, and the values of cell yields (Y) increased from 0.13 to 0.18 synchronously, the Y value and alkalinity dose were fitted to an empirical correlation; granular sludge mainly containing Methanosarcina may need less alkalinity supplement in carbohydrate wastewater treatment; observed yield was less than value of Y, mainly due to more energy was consumed in the process of microorganism metabolism when the value of pH was lower than 6.5.