垃圾渗滤液生化出水絮凝-纳滤处理及过程机理

垃圾焚烧发电厂渗滤液是一种含高浓度腐殖酸类物质和高盐含量的复杂有机废水, 传统生化处理后仍难达标排放。本工作围绕垃圾渗滤液生化出水的特性, 开展了Ca(OH)₂絮凝、臭氧氧化预处理与NF处理相结合的处理工艺, 并对处理过程的机理进行了探讨。研究表明, 渗滤液生化出水经过Ca(OH)₂絮凝处理, 可以有效地去除其中的杂环类化合物。生化出水经8 g·L^-1的Ca(OH)₂絮凝处理后, 比MBR出水产水通量提高达8.2%。对Ca(OH)₂絮凝出水进行臭氧氧化处理, 虽然降低了它的COD, 但并未进一步提高其NF膜通量, 其主要原因可能是臭氧氧化生成的硅氧烷类物质造成了膜的污染;与RO处理垃圾渗滤液生化出水相比较, NF膜无法分离废水中的酮类、胺和酰胺类、杂环类化合物, 使得NF产水的COD处在100~160 mg·L^-1。NF平均膜通量的增大可导致产水COD略有上升;垃圾渗滤液生化出水及其预处理水在NF处理过程中, 都没有表现出严重的膜污染。

Flocculation-nanofiltration treatment of biologically treated leachate and process mechanism

The leachate from incineration plant treating municipal solid waste (MSW) is a kind of wastewater, whose composition is very complicated and highly polluted, and after conventional biological treatment they can still not be directly discharged. According to characteristics of the biologically treated leachate, a combined process was proposed in which the biologically treated leachate was flocculated firstly by Ca(OH)₂, and then the flocculated leachate was oxidized by ozone, and finally the ozonated leachate was filtered by NF membrane, and process mechanism was also explored. The experimental results indicated that Ca(OH)₂ flocculation can effectively remove a large fraction of organic pollutants like heterocyclic compounds and improve the NF membrane flux. The permeate flux of flocculated effluent at the dosage of 8 g·L^-1 Ca(OH)₂ is increased by 8.2% compared with that of MBR effluent. The COD concentration in the flocculated leachate can be further reduced by the ozonation process, but NF membrane flux has no improvement. The reason could be that the siloxane compounds generated by the ozonation process caused the fouling of NF membrane. Compared with RO treatment process, ketones, amines, amides and heterocyclic compounds present in the biologically treated leachate can pass through the NF membrane. As a result, the NF permeate COD was increased by 100 mg·L^-1 to 160 mg·L^-1.Besides, the increases of NF average flux could lead to a slight increase of permeate COD. Membrane fouling is not obvious after the NF treatment of the biologically treated leachate and its pretreated samples.