微涡旋絮凝逆流气浮纳滤集成工艺去除水中腐殖酸的研究——以聚合氯化铝(PACl)为絮凝剂

Removing humic acid in water by the integrated process of micro-eddy flocculation(MEF)-counter current dissolved air flotation (CCDAF)—nanofiltration (NF), PACl as flocculant

研究了微涡旋絮凝逆流气浮纳滤集成工艺去除水中腐殖酸的工艺特征和效果.试验结果表明,微涡旋絮凝逆流气浮工艺去除水中腐殖酸时,在最佳投药点(PACl),出水水质符合纳滤系统预处理单元的要求,而且该工艺需要PACl絮凝剂的量较低.该预处理系统与纳滤系统组合的集成工艺可以使水中的腐殖酸浓度大大降低,且含TQ5636FC型纳滤膜的流程1比含MN1812A型纳滤膜的流程2效果好.前者出水的TOC值可达0.28～0.45mg·L-1,CODMn值为0.47～0.8mg·L-1,UV254nm值为0～0.0033,且有95%以上的脱盐率;后者出水的TOC值为0.52～1.25mg·L-1,CODMn值为0.66～1.0mg·L-1,UV254nm值为0.008～0.012,脱盐率很低.另外,尽管保安过滤器活性炭预处理有利于纳滤膜出水水质的提高,但活性炭柱与纳滤膜能去除的有机物种类有些重合,活性炭柱的存在也降低了纳滤膜对有机物的去除率.水中颗粒物的粒度分布表明,原水、絮凝后和气浮出水中颗粒物粒度分布的中位直径(d50)分别为5～6μm、10～14μm和8～13μm.经过保安过滤器或保安过滤器活性炭柱,水样中的颗粒物的d50为0到几个μm.经过纳滤膜后出水无颗粒物.

The integrated process of micro-eddy flocculation（ MEF）-counter current dissolved air flotation（ CCDAF）-nanofiltration（NF） was used to remove humic acid in water, and its characteristics and effects were studied. The results showed that water quality of MEF-DAF process could match the requirement of pre-unit for membrane system at optimum dosage of PACl flocculant. The dosage is less than that in flocculation-sediments process. The MEF-CCDAF-NF integrated process could remove most of humic in water, and the flowage one with TQ56-36FC NF unit had better performance than the flowage two with M-N1812A one. It could be demonstrated by the better quality of effluent water after flowage one ： 0.28-0.45 mg·L^-1 of TOC, 0.47-0.8mg·L^-1 of CODMn, 0-0. 0033 of UV254nm, and only 5% residual TDS than that after flowage two： 0.52-1.25mg·L^-1 of TOC, 0.66-1.0mg·L^-1 of CODMn 0.008-0.012 of UV254nm, and high TDS content. Moreover, the NF perraeat quality could be improved when activated carbon （AC） unit following MF, but some kinds of organics in water could be catch by both AC and NF units, leading to decreasing the stepwise removal rate for organics in water by NF unit. The d50 of particle size distribution （PSD） in raw water, flocculated one and floated one are 5-6μm, 10-14μm, and 8-13μm, respectively. Sometimes particles in water with several microns of d50, could still be found afar MF or MF-AC units, and no particles exist in NF permeat.