PAC投加对絮体破碎后再絮凝特性和颗粒去除的影响

Effects of additional dosage of PAC on the re-growth of the broken flocs and removal of particles

为改善絮体破碎后的再絮凝能力,提高颗粒的去除效率,以西宁地区低温低浊水为研究对象,通过光学检测仪器及数学拟合方式,分析补投聚合氯化铝（PAC）对破碎后絮体粒径与分布、生长速率变化的影响,描述颗粒及浊度的去除效果.结果表明：随PAC补投量的升高,絮体粒径和生长速率均先增大后减小,各自达到峰值所需补投药量分别为4和6 mg/L;剩余浊度和颗粒数先降低后升高,最低时可分别降至0.79 NTU、90个·m L^-1.补投2 mg/L药剂后,280-630μm絮体颗粒体积分数由22.85%增大到46.36%,4-35μm絮体颗粒体积分数由1.21%减小至0.19%,再絮凝后絮体平均粒径为400μm,大于未破碎前的370μm,粒径增长率为8.11%,絮体生长速率为77.26μm/min.补投PAC可促进絮体破碎后的再絮凝,提高浊度及颗粒数的去除效果,可有效改善实际工程絮凝工艺效果.

To improve the re-growth ability of broken flocs and the removals of colloids and small particles,the raw water with character of low temperature and turbidity was investigated using optical detection instruments and mathematical method. The effects of additional dosage of PAC on the variations of the floc size,growth rate and floc size distribution were studied and the removals of turbidity and particles were also conducted. With the increase of PAC dosage,the floc size and growth rate showed an initial upward trend followed by a downward trend,and the optimum dosage for the floc size and growth rate was 4 mg / L and 6 mg / L,respectively. Moreover,the residual turbidity and particles were significantly decreased first,and then increased. The lowest values of residual turbidity and particles were 0. 79 NTU and 90 m L^-1. When the addition dosage was 2 mg / L,the volume percentage of the flocs in the range of 280-630 μm was evidently increased from 22. 85 % to 46. 36 %,while that of the flocs in the range of 4-35 μm was decreased from 1. 21% to 0. 19%. In addition,the floc size after re-growth was 400 μm,larger than that before breakage,with the growth rate of 77. 26 μm / min. Therefore,the additional dosage of PAC could obviously improve the re-growth ability of the broken flocs and the removals of turbidity and particles.Moreover,the experimental results could effectively improve the treatment efficiency and water quality.