A Performance Study Of Simultaneous Microbial Removal Of SO₂ And NO In A Biotrickling Filter Under Anaerobic Condition

The process research on experiment and simulation of simultaneous bioremoval of SO₂ and NO under anerobic condition was performed to investigate the long-term removal performance, process parameters and influence factors. The main content is as follows:The enrichment of sulfate reducing bacteria and anaerobic denitrifying bacteria were successfully obtained from the landfill leachate using the highly selective coculturing-technique in a biotrickling filter. The composition of coculture medium was controlled to make the end-product H2S of sulfate reducing bacteria serve as the main electron donor for denitrifying bacteria and so the mutualistic symbiosis relationship was established between the two bacteria. It was shown that when both SO₂ and NO feed concentration were kept constant at 2g/m³ with an empty bed residence time of 76s, the SO₂ removal efficiency was always above 95%. However, NO removal efficiency showed an obvious periodicity of 5-6 days within the 60 days after the attachment phase and the NO removal efficiency was fluctuated with a range of 10% to 92%. The steady state of NO removal efficiency was achieved after 130 days and the NO removal efficiency was fluctuated around 92%.The sulfate reducing bacteria filter, anaerobic denitrifying bacteria filter and the coculture filter used for removing SO₂, NO and NO/SO₂ respectively were performed in parallel. Compared with the anaerobic denitrifying bacteria filter, the coculture filter showed a faster start-up, a higher resistance to shock NO-loadings and a better tolerance of starvation. Compared with the sulfate reducing bacteria filter, the coculture filter had a higher SO₂ removal efficiency with the same empty bed residence time, the same SO₂ feeding concentration or the same oxidation reduction potential.In order to improve the NO-removal performance, some special surfactants were added to the coculture to investigate their effects on NO-removal efficiency. It was indicated that the surfactants consisting of mercapto, thiol, thiophenol, secondary amine, ester and alcohol could effectively increase the NO removal efficiency, among which the 3% （volume ratio） of DMSS-LAO-30 coculture system showed a best NO-removal performance.Based on the experiments, the dynamics model for microbial flue gas desulfurization was obtained using the Deep Biofilm theory and Monod kinetic equation and the effects of empty bed residence time, SO₂ feed concentration, specific surface area of packings, incremental gas feeding and steady gas feeding on the SO₂ removal efficiency were also investigated. Furthermore, based on a simplified 2species-3substrate model with the gas-liquid-biomembrane transfer theory, the population dynamics model for simultaneous removal of NO and SO₂ in a laboratory-scale biotrickling-filter was described. The simulation results were in good agreement with the experimental values of biofilm thickness, population densities of biofilm, total biomass dry weight and partial pressures of NO and SO₂ in the outlet gas and the model has been proven to be accurate and credible with the long-term verification experiments.