[Performance of a novel combined flocculant HECES].

Combined flocculants with higher environmental safety and lower ecological risk are urgently required in the process of water and wastewater treatment. HECES, a kind of flocculants with high effect and high ecological safety was synthesized by natural and biodegradable polysaccharide starch of corn and inorganic aluminium salt. Flocculent performance includes sediment character and turbidity removal rate. The jar test results showed that the flocculent performance of HECES with the dose of 3.0 mg.L-1 was prior to the combined adding 4.5 mg.L-1 PAC and 1.0 mg.L-1 PAM in treating kaolin suspensions. The optimal concentration of HECES was 8.0 mg.L-1 and 4.0 mg.L-1 in treating domestic wastewater and municipal effluent respectively, with the comparison to 50% an 40% of PAC, the removal rate of turbidity reached 95% and 99%, respectively. It was also identified that the optimal concentration required to effect flocculation depended on kaolin concentration, and on the character of the wastewater within the range examined. It could be more effective to treat wastewater with higher concentration of HECES. The flocculating performance would be better at pH 4.0-9.5. The superior ecological safety of HECES was due to its lower dosage and its lower concentration of residual activated aluminium.