膜蒸馏处理滤池反冲洗废水的效能研究

Performance of Membrane Distillation for Treating Filter Backwash Wastewater

采用膜蒸馏(MD)工艺,考察了聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)和聚丙烯(PP)3种材质的疏水膜对滤池反冲洗废水的处理效果。结果表明,PTFE膜的性能最佳,在60℃下能保持(15.2±0.8)L/(m^(2)·h)的渗透通量,并可稳定截留99%的无机离子和80%以上的有机污染物。另外,从工艺优化角度考察了不同预处理方式和进水模式对MD工艺运行的影响,结果表明,混凝沉淀预处理方式能够有效减缓膜结垢,在168 h的运行周期下PTFE膜通量仅下降了35%;与持续浓缩的进水模式相比,间歇进水初期的膜通量下降幅度更大,但每24 h稀释进料后都出现膜通量突增使整体产水量高于连续进水模式总量的5%左右。采用SEM和FTIR分析得出,PTFE膜污染成因是无机盐结晶和腐殖酸类有机污染。

This paper investigated the performance of membrane distillation(MD)process with hydrophobic membranes made of polyvinylidene fluoride(PVDF),polytetrafluoroethylene(PTFE)and polypropylene(PP)for treating filter backwash wastewater.The PTFE membrane showed the best performance,maintained a permeable flux of(15.2±0.8)L/(m^(2)·h)at temperature of 60℃,and stably rejected 99%of inorganic ions and more than 80%of organic pollutants.In addition,the effects of different pretreatment methods and feeding modes on MD process operation were investigated from the perspective of process optimization.Coagulation and precipitation pretreatment effectively slowed down membrane fouling,and the flux of PTFE membrane only decreased by 35%during 168 h operating cycle.Compared with the continuous concentration feeding mode,the membrane flux at the initial stage of intermittent feeding mode decreased more sharply,but the flux suddenly increased every 24 h after diluting the influent,making the overall water yield 5%higher than that of continuous feeding mode.The SEM and FTIR analysis showed that the PTFE membrane fouling was attributed to inorganic salt crystallization and humic acid organic pollution.