Biotreatment of ammonia from air by an immobilized Arthrobacter oxydans CH8 biofilter

A heterotrophic Arthrobacter oxydans CH8 that was capable of removing NH₃ from NH₃ containing gas was isolated from livestock farming wastewater. The A. oxydans CH8 was immobilized with calcium alginate packed into filter column. Metered NH₃-containing gas was partially humidified and passed through the glass column. Extensive tests including the removal characteristics, the removal efficiencies, and the metabolic products of NH₃ by A. oxydans CH8 were conducted. Additionally, the operation criteria for the biofilter was also established. NH₃ removal capacities were elevated by the immobilized-cell (biological conversion) method and the BDST (bed depth service time) method (physical adsorption), respectively. The optimum temperature for removing NH₃ was 30 °C, while the nitrification ability remained 80% at 40 °C. The high efficiency (>97%) in the removal of NH₃ was attained at 36 L/h with pH control and was not decreased because of high NH₃ inlet concentration. In addition, the high maximum removal rate (1.22 g of N/day·(kg of bead)) enhanced the use of the biofilter in industrial-scale NH₃(g) pollution control. The ability to remove NH₃ at high inlet concentration and temperature suggested that the immobilized A. oxydans CH8 biofilter has potential in processing NH₃ gas.