The Ground Water Ammonium Sorption onto Activated Clinoptilolite Column

The use of nitrification filters for the removal of ammonium ion from waste-water is an established technology deployed extensively in polluted ground water. The process involves the development of immobilized bacterial films on a solid packing support, which is designed to provide a suitable host for the film, and allow supply of oxygen to promote aerobic action.  Removal of ammonia and nitrite is increasingly necessary to meet drinking water and discharge standards being applied in the US, Europe and other places. Ion-exchange techniques are also effective for removal of ammonia (as the ammonium ion) from polluted water. The capital and operating costs of ion exchange can be significant, particularly for large volume applications. 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 reduction in the use of regenerant chemicals thus reducing costs and lowering environmental impact. Earlier studies show that limitation of oxygen supply can be an impediment to operation of fixed bed nitrifying filters in flooded mode. In this poster, 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 is compared to that in columns in which only ion exchange is occurring. Further comparison with columns equipped with in-situ aeration using the membrane-module is described. A number of different membrane materials were compared including polyethersulfone (PE), polypropylene (PP), nylon, and polytetra-fluoroethylene (PTFE). The results demonstrate the potential of combined nitrification and ion-exchange, and the effectiveness of in-situ aeration using a novel membrane module.