The Coagulation Enhanced Effect of Polydiallydimethylammonium Chloride to Polyaluminum Chloride in the Treatment of Tiny Polluted Autumn Yangtze River Raw Water

摘要

The enhanced coagulation processes to autumn Yangtze River raw water using steady composite coagulants prepared by polyaluminum chloride (PAC) and Polydiallyldimethylammonium chloride (PDM) with different intrinsic viscosity were reported. Jar tests were used to study the influences of the composite mass ratios of PAC to PDM and the intrinsic viscosity of PDM on the turbidity removal and settlement performance. The results showed that for the Yangtze river raw water with temperature of 16 ～18 °C and turbidity of 70 NTU, the turbidity removal efficiency of the composite coagulants was remarkable. When 6NTU turbidity of supernatant from settlement tank was required according to the current process of potable water plant in Nanjing, the dosage of 1.66mg/L PAC was necessary, the PAC/PDM composite coagulants with the mass ratios of 20:1,10:1,5:1 only needed dosage ranges of 1.38 ～1.26mg/L, 1.19 ～1.14mg/L, 1.16 ～ 1.13mg/L with the increasing of PDM intrinsic viscosity from 0.524dL/g to 2.47dL/g. And compared with PAC used only, composite coagulants could decrease the PAC dose by 16.87%～24.10%, 28.31%～31.32%, 30.12%～31.93%. When 2NTU turbidity of supernatant from settlement tank was required according to the process for preparing higher quality of potable water, the dosage of 3.35mg/L PAC was necessary. And compared with PAC used only, composite coagulants could decrease the PAC dose by 19.10%～30.45%. In generally, PDM could increase the floc density, improve the turbidity removal effect and settlement performance. The lower the mass ratios of PAC to PDM or the higher the intrinsic viscosity of PDM, the more efficient of the composite coagulants was.