壳聚糖促进气浮工艺处理低温低浊淮河原水

为考察壳聚糖对常规混凝-气浮工艺除污效能的影响, 对壳聚糖分别用作助凝剂与微气泡表面改性剂时, 低温低浊淮河原水的气浮处理效果进行研究.利用超滤膜及树脂吸附技术对水中的NOM进行分离, 并分析各NOM组分的THMFP和HAAFP及其去除情况.结果表明:壳聚糖作为助凝剂时, 气浮对NOM的去除表现出明显的选择性, 更偏向于高分子质量疏水性NOM的去除.在溶气系统循环水中投加壳聚糖, 可以对微气泡进行表面改性.循环水pH由7.0降低为5.5(小于壳聚糖pKa), 促进了壳聚糖改性气浮对小分子亲水性NOM的去除, 且浮后水Zeta电位未见明显升高, 壳聚糖分子紧密的黏附在微气泡表面.此外, THMFP与HAAFP的去除率也得到提升.壳聚糖微气泡改性技术为强化气浮去除NOM提供了新选择.
The aim of this work is to investigate the effect of chitosan on improving the performance of the conventional coagulation-dissolved air flotation (DAF) process during the treatment of low temperature and low turbidity of Huaihe River water. Comparative tests using chitosan as coagulant aid or bubble surface modifier were conducted. NOM in samples was fractionated based on hydrophobicity and molecular weight. The trihalomethane and haloacetic acid formation potentials in each fraction and their removal efficiency were also evaluated. The results showed that when chitosan was used as a coagulant aid, DAF exhibited obvious selectivity in the removal of NOM fractions. The hydrophobic organic matters with high molecular weight were removed preferentially. A novel, functionalized bubble surface can be obtained in DAF by dosing chitosan in recycle water. Decreasing the pH of the recycle water from 7.0 to 5.5 (less than the pKa of chitosan) improved the removal of hydrophilic NOM fractions with low molecular weight by chitosan-modified bubbles. Most chitosan molecules were adhered onto the bubble surfaces and there was no obvious increase in the zeta potentials of the floated water. In addition, the enhanced reduction of trihalomethane and haloacetic acid precursors were also observed. Bubble surface modification provides an alternative approach for DAF to promote the removal of NOM from surface water.