Study On Denitrification Removal Of Nitric Oxide In Rotating Drum Biofilter

Nitrogen oxides (NO_X) are major atmospheric pollutants. Traditionaltechnologies for NO_X removal have some drawbacks such as high costs,secondary pollution and difficulty in maintenance. Biofilter is a widelyadopted method for air pollution control due to its security and loweroperating costs. Rotating drum biofilter (RDB) has been highly concernedoverseas in VOC_S control, demonstrating good performance. Nevertheless,little was reported on nitric oxide (NO) removal with RDB.In this thesis, denitrificaion purification of waste gases containing NOwas preliminarily investigated in RDB. The transformation process of NOin RDB will be explained, and then, the N balance in RDB will bedescribed.The experimental results indicated that, under the conditions oftemperature of 25℃～30℃, pH at 6.5 to 7.5, rotating speed of 0.5 r/min,empty bed residence time (EBRT) of 86.4 s, nutrient solution amount of 5L and fresh nutrient solution of 0.2 L/d, it was taken about 30 days for thebiofilm becoming mature. In the five-months' steady operation, NOconcentration was 120～584 mg/m~3, removal efficiency (RE) andelimination capacity (EC) maintained 60%～85.2% and 5～18 g/m~3·h, andthe average were 68.7% and 11.6 g/m~3·h, respectively.Drum rotating speed decided surface renewal and liquid film thickness.NO RE reached the maximum when the rotating speed was 0.5 r/min. It is reasonable to control the nutrient solution amount of 5 L in the experiment,EBRT is a key factor influencing the denitrification process. Moreover, theRE increased as the NO_X oxidize degree increased, and it was restrainedwhen the salt quantity was more than 13600 mg/L, then different carbonsource was investigated, glucose demonstrated the best performance,solium acetate and methanol followed. Excessive carbon source could notimprove RE, but the expense would raise. Temperature did not obviouslyaffect to the RE, and the best result appeared in pH at 8. Denitrobacteriasincluding Paracoccus denitificans and HyPhomlcroblum were showedfrom the electron microphotograph and biotic community in RDB.Gas-liquid mass transfer was the main controlled process, many waysin order to optimize the NO removal was investigated in this research. Thetranform paths of NO_X in RDB included chemical oxidization andbiotransformation. Intermediate product of nitrous oxide was analysisedwith GC-MS. At the end, through the analysis of N balance, the enter andexit amount of N element in gas/liquid phases balanced basically, afterhypothesized the rate of conversion of nitrogen. The study indicated thatdenitrification removal of NO_X in RDB has prospect for future application.