Long-term operation of biofilters for biological removal of ammonia

Biological removal of ammonia was investigated using two types of packing materials, compost and sludge in laboratory-scale biofilters (81 reactor volume). The aim of this study is to investigate the potential of unit systems packed with these supports in terms of ammonia emissions treatment. Experimental tests and measurements included analysis of removal efficiency, metabolic products, and results of long-term operation. The inlet concentration of ammonia applied was 20-200 mg m(-3). The ammonia loading rates of 24.9-566 g NH3 m(-3) d(-1) to compost biofilter (BF3) and 24.9-472 g NH3 m(-3) d(-1) to sludge biofilter (BF4) were applied for 210 days, respectively. Removal efficiencies of the compost and sludge biofilters were in the range of 97-99% and 95-99%, respectively when the inlet concentration of ammonia was below 110 mg m(-3), and the maximum elimination capacities were 288 and 243 g NH3 m(-3) d(-1), respectively. However, removal efficiency and elimination capacity of both biofilters significantly decreased as the inlet concentration increased to above 110 mg m(-3). By using kinetic analysis, the maximum removal rate of ammonia, V-m, and the saturation constant, K-s, were determined for both packing materials and the value of V-m for compost was found to be larger. Periodic analysis of the biofilter packing materials showed the accumulation of the nitrification product NO3- in the operation. During the experiment, the pressure drops measured were very low. The use of both packing materials requires neither nutritive aqueous solution nor buffer solution. (C) 2004 Elsevier Ltd. All rights reserved.