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Novel process of biochemical ammonia removal from air streams using a zeolite (clinoptilolite) filter system

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Abstract

Ammonia (NH3) in air is of major health and environmental concern, i.e. contribution to the greenhouse effect when NH3 is converted to nitrous oxide (N2O) in the atmosphere. Another important concern for ammonia in the atmosphere, is the possible conversion to secondary fine particulate matter in the presence of SOx or NOx. The main sources of NH3 in air are waste and food processing industries as well as animal livestock production. The increase in environmental litigation, coupled with rising environmental awareness and a focus on quality of life, has resulted in an increase in the investigation and implementation of new technologies for the treatment of ammonia. In addition, existing methods are cost intensive, unreliable or complex and difficult to control. In this research, a novel biochemical ammonia removing process has been developed and operated for 300 days. This process involves a sequence of biological, physical and chemical processes initiated by the dissolution of the introduced ammonia into the water of the filter system to make the ammonium available for biological degradation (nitrification). A spontaneous reaction of the intermediate nitrification product, nitrite, and ammonium to nitrogen takes place as soon as both compounds are present. This reaction is known to be catalysed by zeolite (clinoptilolite). Water from the discharged moisture of the filter system was condensed on top of the reactor by employing a novel moisture control mechanism. The clean condensate percolated by gravity through the reactor bed and forced the accumulated compounds to the bottom of the reactor. This led to a gradient distribution of compounds across the reactor depth with the highest concentrations at the bottom (140 mM ammonium, 1 M nitrite and 350 mM nitrate), favouring the chemical reaction of NH4+ + NO2-

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