Enzymatic Treatment of Alginate to Reduce UF/MF Membrane Fouling for Municipal Wastewater Reuse

摘要

Wastewater reuse has proven to be effective and successful to solve water shortage problems and to support the sustainable development of the economy. Nonpotable reuse is a widely accepted practice that will continue to grow in many parts of the world. In order to meet the safety and quality requirements for wastewater reuse, advanced treatment technologies like membrane filtration are necessary. However, polysaccharides, the polymeric carbohydrates secreted by microorganisms from the effluent of wastewater treatment plants may cause significant membrane fouling. Alginate is one the typical polysaccharides found in wastewater effluent. This study explored using the enzyme of alginate lyase to catalytically degrade alginate in order to decrease their affinity and fouling potential to γ-Al_2O_3 membranes of 0.2 and 0.02 urn pore size, respectively. Size exclusion chromatography indicates a significant decrease in molecular weight of alginate after enzymatic reactions for 2 hours. Enzymatically treated alginate caused less fouling on both membranes than original alginate at pH 6.7±0.3 and ionic strength of 0.075 M. Alginate lyase reduced the foulant resistance by 82% and 85% for 0.2 and 0.02 urn membranes, respectively. Compare to 0.2 μm membrane, enzyme had more significant enhancement of backwashing of 0.02 urn membrane with a 100% recovery rate obtained. The foulant structure composed of treated alginate was more readily removed by backwashing, suggesting reversible fouling. The advantages of using enzymatic technique to control membrane fouling include high efficiency and no damage to the membrane materials.