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INTENSIFICATION OF AMMONIA REMOVAL FROM WASTE WATER IN BIOLOGICALLY ACTIVE ZEOLITIC ION EXCHANGE COLUMNS


  The use of nitrification filters for the removal of ammonium ion from waste-water is an established technology deployed extensively in municipal water treatment and in industrial water treatment. The process involves the development of immobilized bacterial films on solid packing support, which is designed to provide a suitable host for the film, and allow supply of oxygen to promote aerobic action. Ion-exchange techniques are also very effective for removal of ammonia (as the ammonium ion) from waste water and have the advantage of very fast start-up times compared to biological filtration which in some cases may take several weeks to be fully operational. The capital and operating costs of ion exchange can be significant particularly for large volume applications such as for water treatment. Here we explore the performance of ion exchange columns in which nitrifying bacteria are cultivated, with the goal of a “combined" process involving simultaneous ion-exchange and nitrification. A combined process offers the potential of significant reduction in the use of regenerant chemicals thus lowering costs and reducing environmental impact. Earlier studies show that limitation of oxygen supply can be an impediment to operation of fixed bed nitrifying filters in flooded mode. Here, the integration of a membrane module for in-situ introduction of air into biologically active ion exchange columns is described. The performance of fixed beds of clinoptilolite in the presence of nitrifying bacteria was compared to that in columns in which only ion exchange is occurring. The influence of in-situ aeration using a membrane-module is described. Porous membrane materials were compared including polyethersulfone, polypropylene, nylon, and PTFE. The ammonia removal in the presence of nitrifiers is significantly intensified. Column operation with membrane aeration showed further enhancement of ammonia removal. The greatest enhancement was observed in t[...]

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