Influence of synthetic and natural polymers on the anaerobic granulation process

The influence of synthetic Percol 763 and natural chitosan polymers on the granulation rate of suspended anaerobic sludge was studied in laboratory-scale upflow anaerobic sludge bed (UASB)-like reactors. The results showed that supplementation of the reactors with polymers, either natural or synthetic, enhanced the granulation in comparison to control reactors (without the addition of polymers). A greater granulation was, however, obtained with chitosan compared to that with Percol 763. Chitosan yielded a granulation rate as high as 56 m/d compared to 35 m/d Percol 763. The superior granulation performance of chitosan was probably related to its polysaccharidic structure, hence acting similarly to the extracellular polymeric substances (EPS) in aggregating anaerobic sludge. The granules specific activities were enhanced in the reactors supplemented with both polymers compared to those in control reactors. Overall, the results showed that polymers play a more critical role than microbial trophic groups in enhancing anaerobic granulation in UASB-like reactors.