Ammonium Recovery by Means of a Natural Zeolite in Fluidized Beds

Abstract

As nutrient recovery from source separated urine and agricultural effluents is gaining attention, efficient systems are under investigation. The ammonium ion is a nutrient that can be recovered from wastewaters.

This study focuses on the optimal use of fluidized beds for removing ammonium ion by ion exchange with a natural zeolite using an ammonium concentration similar to the one in domestic wastewater. The main objective of this study is to analyze the effects of major operating parameters such as flow rate and particle size on the ammonium removal performance. This performance is best expressed in terms of a breakthrough capacity/total column capacity. Capacities refer to be amount of the ammonium ion captured on the clinoptilolite until breakthrough occurs or until all clinoptilolite in the column is exhausted, respectively. The ratio of the breakthrough capacity to the total column capacity depends on the operating parameters in the ion exchange column, whereas the total column capacity is a property of the zeolite and its conditioning.

Even though the flow rates in the fluidized beds studied are very high and subsequently the contact times are very short, fluidized beds show similar performances to those attained in fixed beds. An optimal flow rate or linear flow velocity for fluidized beds is sought where the removal performance of the bed is maximized. It is worth noting that the relevant empty bed contact times in the fluidized beds studied in this work vary from about 33 seconds to 75 seconds.

Results indicate that the maximum ammonium removal expressed in terms of breakthrough capacity / total column capacity varied within the range of 0.40 to 0.70 under favorable conditions.  This result is comparable to a fixed bed performance. The study presented here suggests that the use of fluidized beds should be considered and further evaluated as an alternative to ammonium removal in fixed beds.