Biotreatment of hydrogen sulfide- and ammonia-containing waste gases by fluidized bed bioreactor

Gas mixtures of H2S and NH3 are the focus of this study of research concern ing gases generated from animal husbandry and treatments of anaerobic waste water lagoons. A heterotrophic microflora (a mixture of Pseudomonas putida for H2S and Arthrobacter oxydans for NH3) was immobilized with Ca-alginate and packed into a fluidized bed reactor to simultaneously decompose H2S and NH3. This bioreactor was continuously supplied with H2S and NH3 separately or together at various ratios. The removal efficiency, removal rate, and m etabolic product of the bioreactor were studied. The results showed that the efficiency remained above 95% when the inlet H2 S concentration was below 30 ppm at 36 L/hr. Furthermore, the apparent maxi mum removal and the apparent half-saturation constant were 7.0 x 10(-8) gS/ cell/day and 76.2 ppm, respectively, in this study. The element sulfur as a main product prevented acidification of the biofilter, which maintained th e stability of the operation. As for NH3, the greater than 90% removal rate was achieved as long as the inlet concentration was controlled below 100 p pm at a flow rate of 27 L/hr. In the NH3 inlet, the apparent maximum remova l and the apparent half-saturation constant were 1.88 x 10(-6) g-N/cell/day and 30.5 ppm, respectively. Kinetic analysis showed that 60 ppm of NH3 sig nificantly suppressed the H2S removal by Pseudomonas putida, but H2S in the range of 5-60 ppm did not affect NH3 removal by Arthrobacter oxydans. Resu lts from bioaerosol analysis in the bioreactor suggest that the co-immobili zed cell technique applied for gas removal creates less environmental impac t.