Application of Enteromorpha as a new kind of coagulant aid in municipal sludge treatment

Abstract

The large-scale blooms of Enteromorpha disrupts normal ecosystem functioning and brought serious environmental problems in past years. This study focused on the recycling of it with the aim of “treating waste by waste.” In this paper, Enteromorpha polysaccharide (Ep) was applied as a new coagulant aid in sludge treatment process. Initially, orthogonal test was conducted and then the effect of Ep on coagulation behavior was studied and coagulation performance was evaluated in terms of solid content, turbidity, filtrate rate, capillary suction time, and resistance to filtration. Zeta potential and scanning electron microscopic (SEM) were also measured to investigate coagulation mechanism. In addition, cost analysis of sludge treatment was also discussed in this paper. Results of orthogonal test showed that coagulation efficiency was significantly affected by hydraulic conditions. Sludge treatment efficiency could be apparently improved by Ep addition and the optimum polyacrylamide (PAM) and Ep dosages were 15 and 3 mg/L, respectively. When Ep was used in combination with PAM, the average particle size of sludge was increased, and the treated sludge possessed better dehydration ability. In addition, results of cost analysis showed that Ep addition could reduce the cost of sludge treatment by reducing PAM dosage.