Foudmental Research Of Applying On Purification Of SO₂ Waste-gas In Low Concentration By Using Biological Trickling Filter

The problem about air pollution caused by sulfur dioxide from coal brining is one of the focus issues concerned by all over the world. SO₂ not only brings serious air pollution but also causes acid rain for its water-solubility. At present, the mostly physical or chemical methods with high removal rate treating SO₂ have a few disadvantages of high cost and second pollution, but Biological method has many advantages of low cost, few energy sources needed and little second pollution.An approach to purify SO₂ waste gas in low concentration using biological trickling filter is studied in this paper. The microorganism was cultivated by the research team early. The main conclusions from the experiment are the following.(1) It is feasible to purify SO₂ using biological trickling filter with the microorganism cultivated by the research team. And the SO₂ purifying efficiency can reach percent 90.(2) During the growth of the microbial population, the SO₂ removal efficiency gradually increased to about 85% after 40 days, and the pH of the effluent decreased to 2.0 when the microorganism growth was finished.(3) The optimum operating conditions are the following: the concentration of SO₂ in influent gas is 500¹000mg/m³, the gas flow rate is 0.1m²/h, liquid recycle rate is 15L/h and pH is 1.0;the biodegradability increased with the increasing gas flow rate, inlet SO₂ concentration or temperature. However SO₂ removal efficiency decreased from 86.4% to 73.2% when the gas flow rate was changed from 100L/h to 300L/h. both the biodegradability and removal efficiency increased with the increasing of temperature during 15 25 ℃ .While the concentration of SO₂ in flow gas is about 2500mg/m3, the SO₂ removal efficiency could reach 90%. Overall experimental data from the study indicate that the microorganism is suitable for purifying SO₂.(4) According to the kinetic calculation models, the SO₂ biological elimination, the SO₂ outlet concentration and SO₂ removal efficiency were calculated to the change of inlet concentration. The calculated data show that neither of the two models is suitable to explain the removal process.(5) Iron(III) can oxidate SO2 into sulfur(IV) at the acid aqueous solution, which offers the evidence for SO2 removal with the bioreactor in aqueous solution.The microorganism cultivated by the research team is effective on the removal of waste gas such as H2S> CS2N SO2. Since there have few studies on the removing SO2 with biological trickling filter in China, and only several reports can be found in the world, This experiment results not only show a new way for biological low concentration flue gas desulfurization but also provide a potential application and study in waste gas treatment by biological technology.