| Fossil fuels such as petroleum and charcoal contain sulfur and nitrogen which can convert into SO2 and NOx let off after burning. SO2 and NOx can bring sour rain on the earth and detroy the health of mankind. NO is the main exist material of NOx, so the removal of SO2 and NO from industry waste gases are investigated in this paper.The pollution of SO2 and NOx catch the worldwide attention, and many countries are taking some effective measures to control the pollution. Now, the regulation of controlling NOx is established while the pollution of SO2 is being controlled. And the treatment of the pollution of SO2 and NOx is a hot research in the world, all kinds of techniques are developed to solve the problem of the pollution of SO2 and NOx.Traditional disposal techniques of SO2 and NOx mainly adopt physical and chemical methods. The common ones are wet flue gas desulfurization and NH3 election catalyse reduction combined technique, active char adsorption and plasma method and so on. These techniques have taken the important roles in the process of controlling the pollution of SO2 and NOx, but they have some problems such as high cost, complex technics, secondary pollution and the reborn problem of sorbents and catalyzers. Biological one is a new technique and applied wildly by virtue of its simple apparatus, convenient maintenance, low energy consumption, less secondary contamination and high removal efficiency.In this paper bio-trickling towers were established to purify SO2 and NO gases. The whole paper included four parts as follows:(1) Heterotrophic denitrificans were adopted to purify NO simultation waste gases, and the optimal operation conditions were investigated.Biological trickling tower with biofilm carrier was used to investigate the process of purifying the simulating nitric-oxide-containing waste gas by denitrifiers. The experiment demonstrated that rod bacillus denitrifyers can be gotten by dynamic cultured and tamed for carrying on the packing materials. Nitric oxide removal efficiency is up to 98.4%, with empty-bed residence time(EBRT)80 s, inlet nitric oxide concentration 30～500 mg/m3 and circulating liquid flux 90-100L/h. In addition, only little NO3- could be detected in the liquid. The way of purification of nitric-oxide-containing waste gas by denitrifying is feasible.(2) SRB + TD two bio-trickling towers in series were developed to purify SO2 and NO simulation waste gases respectively, and the optimal operation conditions were investigated.Biological trickling technique is usually carried out to purify those biodegradable waste gases. In this experiment, Sulfate-Reducing Bacteria(SRB) and Thiobacillus denitrificans(TD) were cultured for carrying on the packing materials in the two bio-trickling towers respectively to treat the waste gases of sulfur dioxide and nitric oxide under the anaerobic conditions. The experiment demonstrated that sulfur dioxide removal efficiency can reach over 99%, with empty-bed residence time(EBRT)30s, inlet concentration 500?1500mg/m3 and circulating liquid spraying density 26m3/(m2·h), and the average removal efficiency of hydrogen sulfide produced by SRB is 90.5%; Nitric oxide removal efficiency can reach 98%at its maximum and average removal efficiency was 73.3% , with empty-bed residence time(EBRT)20s, inlet nitric oxide concentration 500?2000mg/m3 and circulating liquid spraying density 26m3/(m2·h). So, conclusion can be drawn that the way of purification of sulfur dioxide and nitric oxide waste gases by microorganism is worth investigating.(3) SRB + TD + heterotrophic denitrificans cultured in one bio-trickling tower was developed to purify SO2 and NO simulation waste gases, and the optimal operation conditions were investigated.SRB + TD + heterotrophic denitrificans were cultured in one bio-trickling tower to simlutaneous remove SO2 and NO simulation waste gases. The experiment demonstrated that sulfur dioxide average removal efficiency can reach 97.6% and nitric oxide average removal efficiency can reach 51.4%, with pH 7?8,the concentration of S2O32? 3g/L, empty-bed residence time(EBRT)135s, circulating liquid spraying density 18m3/(m2·h), sulfur dioxide inlet concentration 200?5000mg/m3 and nitric oxide inlet concentration 20?500mg/m3. To elevate gases removal efficiency, the further study on simultaneous biological removal of SO2 and NO gases need to solve some problems such as the competition between SRB and TD on S2O32?.(4) The study on biological mechanism of removal of SO2 and NO gasesIn the four part of this paper, the mechanism of biofilm forming and the structure of microorganism in the biofilm was discussed. On the basis of tradition biofilm theory and experiment, a transformed biofilm theory was brought forward which divides biofilm in the bio-trickling tower into three kinds: liquid biofilm, solid biofilm and active biofilm according to different containing water quantity. And the suitable biofilm to biological removal of SO2 and NO were analyzed. In addition, biological removal mechanism were discussed in this part. Some disadvantages of biological removal of SO2 and NO wrer found and next research goals were brought forward and some practical problems which will be confronted in the process of indutrial application of this subject were also discussed in this part.
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