Study On Treatment Of Thiobacillus Denitrificans In Flue Gas And Waste Water Denitrification And Desulfurization Processes

Nitrogen compounds and sulfur compounds in flue gas and waste water are harmful to environment and human health. The traditional technologies for removing these pollutants have some shortcomings such as high cost or produced secondary pollutant.Thus, biological purification technology become more concerned in recent years because of its easily design, low cost, no repeated pollution.The biological characteristics and suitable growth conditions of Thiobacillus denitrificans were demonstrated. Thiobacillus denitrificans has such advantage as desulfurization and denitrification under anaerobic conditions. Therefore it can be used to remove hydrogen sulfide and nitric oxide from flue gas and sulfide and nitrate from waste water. The experiment was carried out in Biotrickling filter filled with packing on which Thiobacillus denitrificans grown. The factors influencing the H2S and NOx removal efficiency such as gas flow, concentration of inlet gas, spray volume of circulation liquid, etc, were observed. The factors influencing the nitrate and sulfide removal efficiency such as the ratio of sulfide to nitrate and the sulfide concentration, etc, were investigated too.The results of the experiment were summarized as follows:Thiobacillus denitrificans could effectively remove H2S, NOx, nitrate and sulfide under anaerobic condition.The removal efficiency of H2S increased from 75% to 91% when the spray volume of circulation liquid was 150L/h, gas flow was 1m3/h, the inlet concentration of H2S increased from 0 to 30ppm. The removal efficiency of H2S decreased from 91.4% to 73.3% when the spray volume of circulation liquid was 150L/h, gas flow was 1m3/h, the inlet concentration of H2S increased from 30 to 160ppm. The removal efficiency of NO2 was about 95% when the spray volume of circulation liquid was 200L/h, gas flow was 0.1m3/h, the inlet concentration of NO2 increased from 100 to 450ppm. The removal efficiency of NO keeped between 70.9%—73.2% when the spray volume of circulation liquid was 150L/h, gas flow was 0.1m3/h, the inlet concentration of NO increased from 200 to 450ppm. The removal efficiency of NO decreased from 69.4% to 59.9% when the spray volume of circulation liquid was 150L/h, gas flow was 0.1m3/h, the inlet concentration of NO increased from 750 to 1600ppm. In addition, through the analysis on mass transfer of H2S and NOx in bio-reactor, it was indicated that"Adsorption-Biofilm Theory"was suited for removal of H2S and NO, and"Absorption-Biofilm Theory"was suited for removal of NO2.When the ratio of sulfide to nitrate was 5:3, and the sulfide concentration was controlled at 400mg/L in the waste water, the nitrate removal efficiency reached over 65% and the sulfur concentration was 207.3mg/L after 3 days. While the sulfide concentration reached over 400mg/L, the efficiency of nitrate removal reduced quickly.