Enteromorpha prolifera polysaccharide based coagulant aid for humic acids removal and ultrafiltration membrane fouling control.

Polyacrylamide (PAM) has been used as a coagulant aid in water treatment process for past decades, but it has caused great damages to human nervous system. Developing new coagulant aid with high biological safety is urgently demanded. This study provides a natural biomacromolecule coagulant aid with good biosecurity-Enteromorpha prolifera polysaccharide (Ep). Its coagulant aid efficiency and mechanism were investigated in terms of organics removal, floc properties and membrane fouling degree. In addition, contrast experiments were conducted with PAM to evaluate its potential of industrial applications. Results showed that organics removal could be increased by 23% when 0.3 mg/L Ep was used, which exhibited comparable aid effects to PAM. Due to the bridging-sweep aid role of Ep, flocs sizes, growth rate and recovery factor reached 470 μm, 62.6 μm/min and 0.492, respectively, while only 170 μm, 14.0 μm/min and 0.326 were obtained by PAM. Additionally, flocs exhibited more porous and multi-branched structures when Ep was applied, which caused less ultrafiltration membrane fouling (eventual J/J value = 0.52). As a result, Ep could be considered as a potential substitute of PAM, since better biosecurity, higher organics removal and lower membrane fouling could be obtained simultaneously by Ep addition.