Enzymatic Control of Alginate Fouling of Ceramic Micro- and Ultra-Filtration Membranes: Effect of Solution Chemistry

Alginate is a typical polysaccharide and membrane foulant in the secondary effluent of treated wastewater. This study investigated using the enzyme of alginate lyase to catalytically depolymerize alginate in order to decrease its affinity and fouling potential to gamma-Al₂O₃ ceramic membranes of 0.2 and 0.02 µm pore size, respectively. Enzymatically treated alginate caused less fouling on both membranes at pH 6.7 and 9.0 with ionic strength from 0.006 to 0.075 M. Without the presence of calcium, alginate lyase reduced the foulant resistance by more than 82% for both membranes. In the presence of 1 mM calcium cation, alginate lyase reduced the foulant resistance by more than 55%. In addition, the foulant structure composed of treated alginate was more readily removed by backwashing, suggesting reversible fouling. Alginate lyase provided an enhancement of backwashing of the 0.02 µm membrane with a greater than 92% recovery rate in the absence of calcium. However, a less significant improvement of the permeate recovery rate was observed with enzymatically treated alginate in the presence of 1 mM Ca²⁺. Overall, enzymatic technique provides a viable solution to membrane fouling. The advantages of the technique include high efficiency and no damage to the membrane materials.