Effect of hydraulic loading rate on acidogenesis in a membrane-coupled anaerobic VFAs fermenter

A membrane-coupled anaerobic VFAs fermenter (MCAVF) was operated with five different hydraulic loading rates (3, 2, 1, 0.5 and 0.25 day(-1)) to evalua te its influence on acid phase VFAs production from coagulated raw sludge. Results show that C-2 to C-s volatile fatty acids were formed as predominan t compounds. At constant solids retention time (SRT) of 10 days, VFAs produ ction ratio moderately increased over the range of hydraulic loading rate ( HLR) of 3 day(-1) to 2 day(-1), but significantly decreased at other HLR co nditions. First order hydrolysis rate constant decreased with a decrease in HLR. The relatively high degradation percentages of carbohydrate and prote in were observed, ranging from 25 to 47%, 27 to 47%, respectively. However, lipid and fiber component were degraded at much lower ratio than the previ ous other two organic materials. On the other hand, despite some variation in the minor acids in five HLR cases, VFAs speciation appeared to be indepe ndent of HLR. The results obtained emphasize that; at least in the range in vestigated, the optimal HLR for VFAs production and recovery from coagulate d raw sludge is in the range of 2 day(-1) and 1 day(-1).