Effect of agitation on the performance of an anaerobic sequencing batch biofilm reactor in the treatment of dairy effluents

摘要

Agitation rate is an important parameter in the operation of Anaerobic Sequencing Biofilm BatchnReactors (ASBBRs), and a proper agitation rate guarantees good mixing, improves mass transfer,nand enhances the solubility of the particulate organic matter. Dairy effluents have a high amountnof particulate organic matter, and their anaerobic digestion presents inhibitory intermediatesn(e.g., long-chain fatty acids). The importance of studying agitation in such batch systems is clear.nThe present study aimed to evaluate how agitation frequency influences the anaerobic treatmentnof dairy effluents. The ASBBR was fed with wastewater from milk pasteurisation process andncheese manufacture with no whey segregation. The organic matter concentration, measured asnchemical oxygen demand (COD), was maintained at approximately 8,000 mg/L. The reactor wasnoperated with four agitation frequencies: 500 rpm, 350 rpm, 200 rpm, and no agitation. In termsnof COD removal efficiency, similar results were observed for 500 rpm and 350 rpm (around 90%)nand for 200 rpm and no agitation (around 80%). Increasing the system’s agitation thus not onlynimproved the global efficiency of organic matter removal but also influenced volatile acidnproduction and consumption and clearly modified this balance in each experimental condition.