Ca(OH)_2絮凝沉淀-臭氧氧化垃圾渗滤液生化出水提高反渗透性能

Improvement of reverse osmosis performance of biologically treated leachate from municipal solid waste incineration plant by Ca(OH)_2 flocculation,precipitation and ozonation

为了提高生化出水的反渗透性能,本文提出采用Ca(OH)_2絮凝沉淀预处理生化出水,再经O_3氧化后,用于反渗透膜的深度处理工艺.研究表明,Ca(OH)_2絮凝沉淀可以有效地去除垃圾渗滤液生化出水中的大分子有机物及Ca^(2+)、Mg^(2+)离子.当废水絮凝沉淀出水的电导率最低时,废水中的Ca^(2+)和Mg^(2+)离子浓度降到最低,同时也去除了较大比例的COD.对电导率最低条件下的Ca(OH)_2絮凝沉淀出水再经O_3处理后,废水中的Ca^(2+)和Mg^(2+)离子浓度和COD进一步降低,其反渗透膜通量比MBR出水的通量增高25%—35%,膜污染明显减轻,可延长膜清洗周期.臭氧氧化Ca(OH)_2絮凝沉淀出水涉及到臭氧分子直接氧化和氢氧根催化臭氧氧化两种机理,但前者起主导作用.臭氧氧化处理进一步降低了废水中的COD和Ca^(2+)、Mg^(2+)离子浓度,是提高反渗透膜通量的主要原因.

The leachate produced in an incineration plant for municipal solid waste（ MSW） is a very complex and highly polluted wastewater. The wastewater can not be discharged after conventional biological treatment. To improve the reverse osmosis performance of the biologically treated leachate,a combined process was proposed in which the biologically treated leachate was treated by Ca（OH）_2flocculation and precipitation,then oxidized by ozone with the OH-ions present in the Ca（OH）_2flocculated leachate, and finally the ozonated leachate was treated by RO membrane. The experimental results indicated that flocculation coagulation of Ca（OH）_2effectively removed a large fraction of organic pollutants such as humic acids and reduced Ca^（2＋）and Mg^（2＋）concentration in the biologically treated leachate were conductivity of the flocculated leachate is lowest. The COD and Ca^（2＋）and Mg^（2＋）concentration in the flocculated leachate were further reduced after the ozonationprocess. The RO membrane flux of the ozonated leachate was raised by 25%—35% compared to that of the biologically treated leachate,and RO membrane fouling was obviously reduced. Molecular ozone oxidation and catalytic ozonation mechanisms coexisted in the ozonation process of Ca（OH）_2flocculated wastewater,but the former played a more important role. Further reduction of COD,Ca^（2＋）and Mg^（2＋） concentration by the ozonation process is the major cause for the improvement of reverse osmosis performance of the wastewater.