Nitric Oxide Removal Efficiency Research Articles

N2O production in the FeII(EDTA)-NO reduction process: the effects of carbon source and pH

Chemical absorption-biological reduction (BioDeNOx), which uses Fe(II)(EDTA) as a complexing agent for promoting the mass transfer efficiency of NO from gas to water, is a promising technology for removing nitric oxide (NO) from flue gases. The carbon source and pH are important parameters for Fe(II)(EDTA)-NO (the production of absorption) reduction and N2O emissions from BioDeNOx systems. Batch tests were performed to evaluate the effects of four different carbon sources (i.e., methanol, ethanol, sodium acetate, and glucose) on Fe(II)(EDTA)-NO reduction and N2O emissions at an initial pH of 7.2 ± 0.2. The removal efficiency of Fe(II)(EDTA)-NO was 93.9%, with a theoretical rate of 0.77 mmol L(-1) h(-1) after 24 h of operation. The highest N2O production was 0.025 mmol L(-1) after 3 h when glucose was used as the carbon source. The capacities of the carbon sources to enhance the activity of the Fe(II)(EDTA)-NO reductase enzyme decreased in the following order based on the C/N ratio: glucose > ethanol > sodium acetate > methanol. Over the investigated pH range of 5.5-8.5, the Fe(II)(EDTA)-NO removal efficiency was highest at a pH of 7.5, with a theoretical rate of 0.88 mmol L(-1) h(-1). However, the N2O production was lowest at a pH of 8.5. The primary effect of pH on denitrification resulted from the inhibition of nosZ in acidic conditions.

Photocatalytic oxidation of nitric oxide from simulated flue gas by wet scrubbing using ultraviolet/TiO2/H2O2 process

Nitric oxide (NO) from flue gas is hard to remove because of low solubility and reactivity. A new technology for photocatalytic oxidation of NO using ultraviolet (UV)/TiO2/H2O2 process is studied in an efficient laboratory-scale reactor. Effects of several key operational parameters on NO removal efficiency are studied, including TiO2 content, H2O2 initial concentration, UV lamp power, NO initial content, oxygen volume fraction and TiO2/H2O2 solution volume. The results illustrate that the NO removal efficiency increases with the increasing of H2O2 initial concentration or UV lamp power. Meanwhile, a lower NO initial content or a higher TiO2/H2O2 solution volume will result in higher NO removal efficiency. In addition, oxygen volume fraction has a little effect. The highest NO removal efficiency is achieved at the TiO2 content of 0.75 g/L, H2O2 initial concentration of 2.5 mol/L, UV lamp power of 36 W, NO initial content of 206×10−6 and TiO2/H2O2 solution volume of 600 mL. It is beneficial for the development and application of NO removal from coal-fired flue gas with UV/TiO2/H2O2 process.

Oxidative absorption of NO by sodium persulfate coupled with Fe2+, Fe3O4, and H2O2

The oxidative absorption of nitric oxide (NO) by sodium persulfate (Na2S2O8) coupled with Fe2+, Fe3O4, and H2O2 was investigated in a bubble column reactor. Moreover, the effect of temperature on NO removal has been studied. At high temperatures, Fe2+ and Fe3O4 could effectively activate persulfate to form sulfate radicals, leading to high removal efficiency of NO. About 62% and 86% of NO were removed at 75 and 90°C, respectively. Also, the optimum Fe2+ concentration for 0.2 mol L−1 persulfate was 1.0 mmol L−1 at 75°C, under which the removal efficiency of NO was observed to be 89%. However, beyond 1.0 mmol L−1 Fe2+, the increase in Fe2+concentration was unfavorable to NO removal due to the scavenging of radicals by the excess Fe2+. Additionally, the presence of 2.85 mmol L−1 Fe3O4 increased the NO removal efficiency by 11% compared to that obtained in the absence of Fe3O4. It was proposed that activation ability of Fe3O4 to persulfate was attributed to Fe2+ on the Fe3O4 surface. Moreover, the addition of H2O2 led to the increase of the NO removal for some time, but followed by a drop because of the depletion of H2O2. It was suggested that H2O2 served as an oxidant rather than an activator of persulfate. © 2014 American Institute of Chemical Engineers Environ Prog, 2014 © 2014 American Institute of Chemical Engineers Environ Prog, 34: 117–124, 2015

Removal of nitric oxide from simulated flue gas via denitrification in a hollow-fiber membrane bioreactor

A hollow-fiber membrane bioreactor (HMBR) was studied for its ability to treat nitric oxide (NO) from simulated flue gas. The HMBR was operated for 9 months and showed a maximum elimination capacity of 702 mg NO/(m2day) with a removal efficiency of 86% (gas residence time of 30 sec, inlet NO concentration of 2680 mg/m3, pH 8). Varying operation parameters were tested to determine the stability and response of the HMBR. Both the inlet NO concentration and gas residence time influenced the removal of NO in the HMBR. NO elimination capacity increased with an increase in inlet NO concentration or a shortening of gas residence time. Higher removal efficiency of NO was obtained at a longer gas residence time or a lower inlet NO concentration. Microbial communities of the HMBR were sensitive to the variation in pH value and alkalescence corresponding to an optimum pH value of 8. In addition, NO elimination capacity and removal efficiency were inversely proportional to the inlet oxygen concentration. Sulfur dioxide had no great influence on elimination capacity and removal efficiency of NO. Product analysis was performed to study N2O and N2 production and confirmed that the majority of the microorganisms were denitrifying bacteria in the HMBR. Compared to other bioreactors treating NO, this study showed that the denitrifying HMBR was a good option for the removal of NO.

Advanced Oxidative Removal of Nitric Oxide from Flue Gas by Homogeneous Photo‐Fenton in a Photochemical Reactor

AbstractIn this work, advanced oxidation removal of nitric oxide (NO) from flue gas by homogeneous Photo‐Fenton was investigated in a photochemical reactor and the effects of several influencing factors on NO removal were evaluated. The gas‐liquid reaction products were determined. The reaction pathways of NO removal are also preliminarily discussed. It was found that with the increase of Fe2+ concentration, NO removal efficiency first increased and then decreased. Increasing H2O2 concentration and UV radiation intensity greatly increased NO removal efficiency, but the growth rates gradually became smaller. NO removal efficiency greatly reduced with the increase of gas flow and NO concentration, and only slightly decreased with the increase of solution temperature, but significantly increased with the increase of initial solution pH value. The main anion product in the liquid phase was NO3–. With respect to removal of NO using homogeneous Photo‐Fenton, ·OH oxidation was the main reaction pathway, and H2O2 oxidation was the secondary reaction pathway.

Kinetic Analysis of Dielectric Layer Thickness on Nitric Oxide Removal by Dielectric Barrier Discharge

The kinetic analysis of dielectric layer thickness on nitric oxide (NO) removal in dielectric barrier discharge (DBD) reactor was investigated. The simulated results show that, with the decrease of dielectric layer thickness, the electric field increases, leading to an enlarging E/N. When E/N was 250 Td, the dissociation rate and electron mean energy reached 14.3 times and 1.5 times respectively compared to when E/N was 150 Td, and their excitation rates were magnified 176, 182, 226, and 171% separately, generating more N atoms and metastable states of N2 molecules. In NO/N2 system, the dissociation and excitation rate of N2 were related to the amount of NO removal. The experimental results show that, NO removal efficiency increased as energy density was increased and a decreasing dielectric layer thickness promoted NO removal, which coincides with simulated ones well, indicating the feasibility and the rationality of the dynamics analysis.

Water and temperature effects on photo-selective catalytic reduction of nitric oxide on Pd-loaded TiO2 photocatalyst

Photo-selective catalytic reduction (photo-SCR) of nitric oxide (NO) was studied in the presence of water. The incipient wetness impregnation was applied to prepare 1 wt% PdO/TiO2 photocatalyst. Steady-state photoreaction was carried out in a continuous-flow photoreactor with 0.55–1.6 v% water at 30–120°C under UV-light intensity of ∼ 200 mW/cm2. The C3H8/NO molar ratio in the feed ranged from 0.8–16.8 at a volume hourly space velocity (VHSV) from 330–1090 h−1. The result indicates that the increase of temperature has played an important role in inhibiting NO transformation to NO2 under the humid condition. Another important factor for maximizing denitrification (reduction of nitrogen oxides, DeNOx) efficiency was C3H8/NO ratio. An increase of temperature at a suitable C3H8/NO ratio can minimize NO2 formation, which can lead to high NO removal efficiency of more than 90% at a temperature of 70–100°C. In addition, the mechanism of palladium transformation during photoreaction is proposed, to explain the influence of Pd on the improvement of NO removal.

Evaluation of Nitric Oxide Removal from Simulated Flue Gas by Fe(II)EDTA/Fe(II)citrate Mixed Absorbents

Fe(II)EDTA is an effective absorbent for the integrated chemical absorption–biological reduction system in removing nitric oxide (NO) from flue gas. However, this absorbent is subject to some defects, such as oxidation by oxygen. In order to overcome this drawback, instead of using Fe(II)EDTA solely, a mixed absorbent containing both Fe(II)EDTA and Fe(II)Cit (Cit = citrate) is employed to absorb NO from simulated flue gas. The mixed absorbent not only shows a high NO absorption capacity similar to a Fe(II)EDTA absorbent, but also exhibits high NO absorption rate and good resistance to oxidation in simulated flue gas. This mixed absorbent can maintain 80% NO removal efficiency at 323 K for more than two hours at an inlet NO concentration of 670 mg·m–3, which is almost as effective as the Fe(II)EDTA absorbent at the same Fe(II) concentration. The oxidation rate constant of Fe(II) in the mixed absorbent is also slower than that in the Fe(II)EDTA absorbent. The optimal molar ratio of Fe(II)Cit to Fe(II)EDTA in the mixed absorbent was found to be 3:1. The effects of several key factors for NO removal, such as the inlet concentrations of NO (200–670 mg·m–3), O2 (1–6.5%), and SO32– (0–43 mg·L–1) and the pH of the mixed absorbent, have been studied. Interestingly, results seem to suggest that SO32– is beneficial for the removal of NO in the system. These findings provide fundamental data for the design of NO removal system for industrial applications with mixed Fe(II)EDTA/Fe(II)Cit absorbent.

Effect of Reactor Structure in DBD for Nonthermal Plasma Processing of NO in N2 at Ambient Temperature

In order to improve dielectric barrier discharge reactor structure, an experimental study was carried out into its effect on nitric oxide (NO) removal. Different structures were distinguished by electrode connection, diameter, material and shape of inner electrode, and dielectric material, respectively. The results show that breakdown voltage is lower when a high voltage is applied to the outer electrode in the coaxial reactor; NO removal efficiency decreases with a smaller inner electrode diameter and increases when tungsten is used as the inner electrode material rather than copper or stainless steel. When the inner electrode is screw shaped, it improves the discharge power and NO removal efficiency. A similar higher NO removal efficiency is found when corundum is used as the dielectric material instead of ceramic or quartz. Therefore, these findings should become the basis for modifications to the electrode structure in order to improve NO removal efficiency.

Nitric oxide enhanced reduction in a rotating drum biofilter coupled with absorption by FeII(EDTA)

AbstractBACKGROUND: The ongoing emission of nitric oxide (NO) is a serious persistent environmental problem, because it contributes to atmospheric ozone destruction and global warming. A novel and effective system was developed for the complete treatment of NO from flue gases. The system features NO absorption by FeII(EDTA) and biological denitrification in a rotating drum biofilter (RDB).RESULTS: After 100 mg L−1 FeII(EDTA) was added to the nutrient solution, the results show that the NO removal efficiency was improved from 70.56% to 80.15%, the optimal temperature improved from 32.5 °C to 40.5 °C, and the pH improved from 7.5 to 8.0–8.3. A maximum NO removal efficiency of 96.5% was achieved when 500 mg L−1 FeII(EDTA) was used in the nutrient solution.CONCLUSION: This experiment demonstrates that FeII(EDTA) could not only improve the mass transfer efficiency of NO from gas to liquid, but also serve as an electron donor for the biological reduction of NO to N2. The new integrated treatment system seemed to be a promising alternative for the complete treatment of NO from flue gases. © 2012 Society of Chemical Industry

Removal of nitric oxide in a biotrickling filter under thermophilic condition using Chelatococcus daeguensis

The development of a thermophilic biotrickling filter (BTF) system to inoculate a newly isolated strain of Chelatococcus daeguensis TAD1 for the effective treatment of nitric oxide (NO) is described. A bench-scale BTF was run under high concentrations of NO and 8% O2 in thermophilic aerobic environment. A novel aerobic denitrifier Chelatococcus daeguensis TAD1 was isolated from the biofilm of an on-site biotrickling filter and it showed a denitrifying capability of 96.1% nitrate removal rate in a 24 h period in aerobic environment at 50 °C, with no nitrite accumulation. The inlet NO concentration fluctuated between approximately 133.9 and 669.6 mg m-3 and kept on a steady NOx removal rate above 80% in an oxygen stream of 8%. The BTF system was able to consistently remove 80–93.7% NO when the inlet NO was 535.7 mg m-3 in an oxygen stream of 2–20%. The biological removal efficiency of NO at 50 °C is higher than that at 25 °C, suggesting that the aerobic denitrifier TAD1 display well denitrification performance under thermophilic condition. Starvation for 2, 4 and 8 days resulted in the re-acclimation times of Chelatococcus daeguensis TAD1 ranging between 4 and 16 hours. A longer recovery time than that for weekend shutdown will be required when a longer starvation occurs. The results presented here demonstrate the feasibility of biotrickling filter for the thermophilic removal of NOx from gas streams. Implications A novel denitrifier Chelatococcus daeguensis TAD1 was isolated from an on-site biotrickling filter in aerobic environment at 50 °C. To date, C. daeguensis has not been previously reported to be an aerobic denitrifier. In this study, a thermophilic biotrickling filter system inoculated with Chelatococcus daeguensis TAD1 for treatment of nitric oxide is developed. In coal-fired power plants, influent flue gas stream for nitrogen oxides (NOx) removal typically exhibit temperatures between 50 and 60 °C. Traditionally, cooling gases to below 40 °C prior to biological treatment is inevitable, which is costly. Therefore, the application of thermophilic microorganisms for the removal of nitric oxide (NO) at this temperature range would offer great savings and would greatly extend the applicability of biofilters and biotrickling filters. Until now there has not been any study published about thermophilic biological treatment of NO under aerobic condition.

Quantification of Reduction of Nitrogen Oxides by Nitrate Accumulation on Titanium Dioxide Photocatalytic Concrete Pavement

Field trials of photocatalytic pavements were recently initiated and are being considered by many states (e.g., Virginia, Texas, New York, and Missouri). Results from this study are from the country's first air-purifying asphalt and concrete photocatalytic pavements on December 20, 2010. The test area was a pavement site located on the Louisiana State University campus in Baton Rouge. The objective of this study was validation of photocatalytic degradation of nitrogen oxides (NOx) at the test site by measuring nitrate salts (NO3) deposited on the pavement surface. With quantification of the nitrate levels produced in the field attributable to photocatalytic activity, measurements were correlated to laboratory test results of NOx reduction efficiency. A field sampling procedure of NO3 deposited on the pavement surface is presented. On the basis of the results of the experimental program, the proposed method to quantify photocatalytic efficiency through nitrate measurements was successful. There was definite evidence that photocatalytic degradation of NOx was taking place in the treated section. In addition, the photocatalytic process was active during the first 4 days followed by a slight decrease in degradation of NOx. Full regeneration of photo catalytic activity took place through a self-cleaning process during a rain event. Six months of traffic and in-service operating conditions had negligible effects on the efficiency of the photocatalytic coating. In addition, there was good agreement between nitric oxide removal efficiency measured in the field after one day of nitrate accumulation and in the laboratory at the same relative humidity.

Removal of nitric oxide in rotating packed bed by ferrous chelate solution

As a major pollutant flue gas, nitric oxide (NO) emission has received great attention of the world. Various technologies have been developed to reduce NO emission. Among them, wet scrubbing approach seems to be promising concept. Ferrous chelate solution has been demonstrated as a suitable and efficient option in flue gas denitrification process due to its high reaction rate with NO and good regeneration ability. However, NO absorption rate is strongly affected by mass transfer limitation of NO and FeII(EDTA) solution in traditional reactors. In this study, RPB is firstly introduced as a gas–liquid reactor to enhance the NO removal efficiency by FeII(EDTA) solution. Preliminary experimental results are presented on the absorption of NO by investigating the effects of operating parameters on NO removal efficiency in RPB. The removal efficiency peaks when the pH value of the absorbent reaches 7. The optimum temperature for this gas–liquid absorption system is in the range of 293–303K. When the gravity level of the RPB is higher than 150g, the removal efficiency could reach 87%. In addition, the NO removal efficiency decreases with the increase of the gas–liquid ratio. The simultaneous increase of the gas and the liquid flow rates has no obvious effect on the removal efficiency. The obtained results imply a great potential of RPB in the removal of NO from flue gases.

Comparative study of NO removal in surface-plasma and volume-plasma reactors based on pulsed corona discharges

Nitric oxide (NO) conversion has been studied for two different types of atmospheric-pressure pulsed-corona discharges, one generates a surface-plasma and the other provides a volume-plasma. For both types of discharges the energy cost for NO removal increases with decreasing oxygen concentration and initial concentration of NO. However, the energy cost for volume plasmas for 50% NO removal, EC50, from air was found to be 120eV/molecule, whereas for the surface plasma, it was only 70eV/molecule. A smaller difference in energy cost, but a higher efficiency for removal of NO was obtained in a pure nitrogen atmosphere, where NO formation is restricted due to the lack of oxygen. For the volume plasma, EC50 in this case was measured at 50eV/molecule, and for the surface plasma it was 40eV/molecule. Besides the higher NO removal efficiency of surface plasmas compared to volume plasmas, the energy efficiency of surface-plasmas was found to be almost independent of the amount of electrical energy deposited in the discharge, whereas the efficiency for volume plasmas decreases considerably with increasing energy. This indicates the possibility of operating surface plasma discharges at high energy densities and in more compact reactors than conventional volume discharges.

Absorption of nitric oxide from simulated flue gas using different absorbents at room temperature and atmospheric pressure

Effective removal of nitrogen oxides (NOx) from flue gas allows more fossil fuels to be produced and utilized with less negative impact on the environment. It would be more cost-effective, however, if nitric oxide (NO) is oxidized to soluble nitrate and nitrite and then removed from the air by existing desulfurization wet scrubbers. This paper compares the effectiveness of three different oxidants for this purpose, namely, ethylenediaminetetraacetic acid; iron (2+) (Fe(II)–EDTA), hexamminecobalt(II) chloride ([Co(NH3)6]Cl2), and hydrogen peroxide (H2O2). Experimental results using column reactors showed that [Co(NH3)6]Cl2 was more effective over the same period of time. The best initial NO removal efficiency of about 96.45% was measured at the inlet flow rate of 500ml/min; the temperature of approximately 19°C; the pH value of around 10.5; and the concentrations of [Co(NH3)6]Cl2 , NO and O2 of 0.06mol/L, 500ppm and 5.0%, respectively.

Catalytic Reduction of Hexaminecobalt(III) by Pitch‐based Spherical Activated Carbon (PBSAC)

AbstractThe wet ammonia (NH3) desulfurization process can be retrofitted to remove nitric oxide (NO) and sulfur dioxide (SO2) simultaneously by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexaminecobalt(II), Co(NH3), so that NO removal efficiency can be maintained at a high level for a long time. In this study, the catalytic performance of pitch‐based spherical activated carbon (PBSAC) in the simultaneous removal of NO and SO2 with this wet ammonia scrubbing process has been studied systematically. Experiments have been performed in a batch stirred cell to test the catalytic characteristics of PBSAC in the catalytic reduction of hexaminecobalt(III), Co(NH3). The experimental results show that PBSAC is a much better catalyst in the catalytic reduction of Co(NH3) than palm shell activated carbon (PSAC). The Co(NH3) reduction reaction rate increases with PBSAC when the PBSAC dose is below 7.5 g/L. The Co(NH3) reduction rate increases with its initial concentration. Best Co(NH3) conversion is gained at a pH range of 2.0–6.0. A high temperature is favorable to such reaction. The intrinsic activation energy of 51.00 kJ/mol for the Co(NH3) reduction catalyzed by PBSAC has been obtained. The experiments manifest that the simultaneous elimination of NO and SO2 by the hexaminecobalt solution coupled with catalytic regeneration of hexaminecobalt(II) can maintain a NO removal efficiency of 90% for a long time.

피트(peat) 혼합담체를 이용한 저농도 질소산화물(NOx) 제거특성

In this study, removal characteristics of nitrogen oxides <TEX>$(NO_x)$</TEX> from road transport by using peat as the packing media for biodegradation have been investigated in the long term. Physicochemical and biological treatment of peatmixed media eliminates any requirement to use chemical substances and also facilitates the biodegradable actions of microorganism. Safe biodegradation of pollutants, no need to apply additional microbes owing to their active growth, and no generation of secondary pollutants were found in this experiment. It was concluded that average removal efficiencies of nitric oxide (NO) and nitrogen dioxide <TEX>$(NO_2)$</TEX> were 80% and 97% respectively with respect to the linear velocity 35~40 mm/s and 0.3 ppm ozone concentration in the long period operation. Inflow concentration of nitric oxide over 0.05 ppm was suitable when pretreated with ozone. Non-ozone stage was performed with linear velocity 20~100 mm/s and then the average removal efficiency of nitric oxide and nitrogen dioxide were 38% and 94% respectively. Other results showed that the apparent static pressure was raised with increases in applied water content and aerial velocity in mixed media during fan operation.

Simultaneous absorption of NO and SO 2 into Fe II–EDTA solution coupled with the Fe II–EDTA regeneration catalyzed by activated carbon

The simultaneous removal of NO and SO 2 from flue gases can be realized with Fe(II)–ethylenediamineteraacetate(EDTA) solution. Activated carbon is used to catalyze the reduction of Fe III–EDTA to Fe II–EDTA to maintain the capability of removing NO of the Fe–EDTA solution. The reductant is the sulfite/bisulfite ions produced by SO 2 dissolving into the aqueous solution. Experiments have been performed to determine the effects of activated carbon of coconut shell, Fe II–EDTA concentration, Fe/EDTA molar ratio, SO 2 partial pressure, NO partial pressure and SO 4 2− concentration on the combined elimination of NO and SO 2 with Fe II–EDTA solution coupled with the Fe II–EDTA regeneration catalyzed by activated carbon. According to the experimental results, activated carbon not only catalyzes the reduction of Fe III–EDTA by sulfite/bisulfite greatly but also avoids the release of N 2O. The NO removal efficiency increases with the initial Fe II–EDTA concentration and SO 2 partial pressure. The ratio of Fe/EDTA and the SO 4 2−concentration has little effect on the catalytic reduction of Fe III–EDTA. The optimal initial NO concentration range is from 600 ppm to 900 ppm. The experimental results manifest that the Fe II–EDTA solution coupled with catalytic regeneration of Fe II–EDTA can maintain high nitric oxide removal efficiency for a long period of time.

Modeling of a hollow fiber membrane biofilm reactor for nitric oxide removal: model development and experimental validation

AbstractBACKGROUND: A diffusion and reaction model was developed for a hollow fiber membrane biofilm reactor (MBfR) to control nitric oxide (NO) emissions. In the MBfR, waste gases containing biodegradable compounds pass through the lumen of microporous hydrophobic hollow fiber membranes. Soluble, biodegradable compounds diffuse through the membrane pores and partition into a biofilm attached to the membranes where they are biodegraded. The membranes serve as a support for the microbial population and provide a large surface area for mass transfer. A dynamic model was developed for the MBfR which assumed biodegradation via Monod kinetics and constant biofilm thickness and density. The model was validated using experimental data from a study of NO removal (100 ppm) from a combustion gas mixture in a bench‐scale MBfR with an acclimatized nitrifying population.RESULTS: NO gas was treated in a bench‐scale MBfR at varying liquid recirculation velocities of 0.8 to 2.0 cm s−1. The gas residence time (τ), calculated as the membrane lumen volume divided by the gas flow rate, was 1.9 s. NO removal efficiency for synthetic combustion gas ranged between 68% and 73% at room temperature (20 °C).CONCLUSION: The MBfR shows promise for treatment of waste gases from combustion processes. The model predicted an optimal liquid recirculation velocity of 1.5 cm s−1 for NO removal, which is in good agreement with experimental data. Sensitivity experiments with the numeric model indicated that removal was a strong function of the biofilm density and the Monod maximum specific growth rate (µmax). Copyright © 2010 Society of Chemical Industry

Assessment of the Bacterial Community for Denitrifying Removal of Nitric Oxide in a Rotating Drum Biofilter by Denaturing Gradient Gel Electrophoresis

The emission of nitric oxide (NO) to the atmosphere is a major environmental problem. To abate NO emission from the industrial flue gas, a rotating drum biofilter (RDB) was developed for the denitrifying removal of NO. After the start-up period, the RDB could effectively remove NO from the waste gas and the denitrifying removal efficiency could reach 85%. After the addition of CuII(EDTA) to the nutrients, the removal efficiency could increase to 99.1%. To improve the understanding of the relationship between the composition of bacterial population and the performance of the RDB, a denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified genes coding for 16S rRNA was used to analyze and determine the changes in bacterial communities in the RDB. Results showed that there was a slight change in microbial diversity after the addition of CuII(EDTA) to the nutrient solution, which led to an increase in NO removal efficiency. Eight major bands of 16S rRNA gene fragments obtained from the DGGE gels of biofilm samples were further purified, reamplified, cloned, and sequenced. Phylogenetic analysis identified sixteen types of micro-organisms in the RDB. Sequences of these fragments were compared with those listed in the database of the GeneBank (National Center for Biotechnology Information). Gene analysis of 16S rRNA showed that the major populations were Clostridium sp., β-proteobacterium, γ-proteobacterium, and Cytophaga-Flexibacteria-Bacteroides (CFB) groups. In addition, it was concluded that denitrification was caused by the organism with DNA represented by bands labelled G-5, G-6, and G-8. G-5 was related to a γ-proteobacterium, whereas those labeled G-6 and G-8 were related to a β-proteobacterium.