Removal of high concentration of NH 3 and coexistent H 2S by biological activated carbon (BAC) biotrickling filter

Abstract

High efficiency of NH 3 and H 2S removal from waste gases was achieved by the biotrickling filter. Granular activated carbon (GAC), inoculated with Arthrobacter oxydans CH8 for NH 3 removal and Pseudomonas putida CH11 for H 2S removal, was used as packing material. Under conditions in which 100% H 2S was removed, extensive tests to eliminate high concentrations of NH 3 emission—including removal characteristics, removal efficiency, and removal capacity of the system—were performed. The results of the Bed Depth Service Time (BDST) experiment suggested that physical adsorption of NH 3 gas by GAC was responsible for the first 10 days, after which NH 3 gas was biodegraded by inoculated microorganisms. The dynamic steady state between physical adsorption and biodegradation was about two weeks. After the system achieved equilibrium, the BAC biotrickling filter exhibited high adaptation to shock loading, elevated temperature, and flow rate. Greater than 96% removal efficiency for NH 3 was achieved during the 140-day operating period when inlet H 2S loading was maintained at 6.25 g-S/m 3/h. During the operating period, the pH varied between 6.5 and 8.0 after the physical adsorption stage, and no acidification or alkalinity was observed. The results also demonstrated that NH 3 removal was not affected by the coexistence of H 2S while gas retention time was the key factor in system performance. The retention time of at least 65 s is required to obtain a greater than 95% NH 3 removal efficiency. The critical loading of NH 3 for the system was 4.2 g-N/m 3/h, and the maximal loading was 16.2 g-N/m 3/h. The results of this study could be used as a guide for further design and operation of industrial-scale systems.