The Research Of Technology Of Biological Denitrification Over Invers Disproportionation

The technology of biological denitrification over inverse disproportionation is one of the new technologies of biological denitrification. It has the advantages of low processing cost, less sludge production, high removal rate of nitrogen which the traditional technology of biological denitrification does not have. But this new technology hasn’t been developed because of some bottleneck problem such as the multiplication cycle of inverse disproportionation bacteria was very long, the toxicity of substrate concentration and the rigorous reaction condition for inverse disproportionation bacteria. If these bottleneck problems been resolved, the technology of biological denitrification over inverse disproportionation will be a turning point in sewage denitrification industry. This topic has researched the start-up characteristics of the ASBR reactor of biological denitrification over inverse disproportionation, and some influence factors on the biological denitrification over inverse disproportionation. The experimental content and results were as follows:Firstly, we used the aerobic flocculent sludge and the anaerobic granular sludge as inoculation sludge, the homemade glass reactor simulating the ASBR reactor to study the start-up characteristics of the ASBR biological denitrification over inverse disproportionation. In experiment, controlling the reaction temperature at 35 ℃, the p H at 7.5~8.0, the hydraulic retention time was 3 days. The test results were:(1) By the bank test(under the condition of pure matrix), there wasn’t chemical reaction of NH4+-N and NO2--N in our experimental condition;(2) The reactor which using aerobic sludge as inoculums was at the period of sludge adaptation in 1~70 days, in this period, the removal of nitrogen was not stable, the main reaction was heterotrophic denitrification reaction. After the 70 days, the reaction of inverse disproportionation appeared, the ratio of the amount of nitrite nitrogen removed and the ammonia nitrogen removed was high than 1.32, in these time the system has both the heterotrophic denitrification reaction and the inverse disproportionation reaction. After the 87 day, the denitrification reaction stopped, the inverse disproportionation reaction has been the only main reaction in the system. To the 180 th day, the removal rate of ammonia nitrogen and nitrite nitrogen reached to 64.7% and 77.1% respectively, and the ratio of the amount of ammonia nitrogen removed, the nitrite nitrogen removed and the nitrate nitrogen produced was 1:1.42:0.23, close to the theoretical ratio of 1:1.32:0.26, the color of the sludge was brown which was yellow initially;(3) The reactor which using anaerobic granular sludge as inoculums was at the period of sludge adaptation in 1~40 days, after 40 days, it entered the period of activity promotion, the denitrification reaction stopped at the day of 80, and the inverse disproportionation reaction became the main reaction in system. With the passage of time, the removal rate of nitrogen was rising gradually, to 180 th day, the removal rate of ammonia nitrogen and nitrite nitrogen reached to 77% and 80.7% respectively, and the amount of ammonia nitrogen removal and nitrite nitrogen removal and nitrate nitrogen produced was 1:1.22:0.23, close to the theoretical value(1:1.32:0.26), the surface of the sludge was dark red.Secondly, the influence of some factors on the inverse disproportionation reaction was studied, such as the reaction temperature, p H, organic matter, the concentration of substrate and the dissolved oxygen, the source of inorganic carbon. The results as follows:(1) the best reaction temperature for the reactor which using aerobic sludge as inoculums was 35 ℃, and the reactor which using anaerobic granular sludge as inoculums was 38 ℃;(2) The best reaction p H value for the reactor which using aerobic sludge as inoculums was 7.5, and the reactor which using anaerobic granular sludge as inoculums was 8.3;(3) If the concentration of COD was in 0~50 mg/L, the removal of nitrogen was stable, but if the concentration of COD was high than 50 mg/L, then the removal rate of ammonia nitrogen decreased obviously, while the removal rate of nitrite nitrogen increased, the removal rate of total nitrogen was decreasing;(4) When controlling the concentration of ammonia nitrogen was at 100 mg/L, we found that when the concentration of nitrite nitrogen was at 130 mg/L, the removal rate of total nitrogen was highest, it closed to 70%. But when the concentration of nitrite nitrogen reached to 180 mg/L, it produced toxicity to the inverse disproportionation bacteria, the result were the same in both two reactors. When we controlled the concentration of nitrite nitrogen at 130 mg/L, we found that in the reactor of using aerobic sludge as inoculums, the removal of nitrogen wasn’t influenced as the concentration of ammonia nitrogen from 100 mg/L to 330 mg/L. But in the reactor of using anaerobic granular sludge as inoculums, the removal rate of nitrogen decreased when the concentration of ammonia nitrogen beyond 180 mg/L;(5) The experimental results of the influence of dissolved oxygen(DO) on the inverse disproportionation were the same of both two reactors, namely the removal was stable when the dissolved oxygen concentration in 0~0.4 mg/L, but when the dissolved oxygen concentration is higher than 0.4 mg/L, removal rate of total nitrogen began to fall;(6) When the concentration of inorganic carbon source is less than 40 mg/L, it can’t meet the needs of the inverse disproportionation reaction, denitrification effect is not stable. When the concentration of inorganic carbon source was more than 40 mg/L, the inverse disproportionation denitrification effect became stable, if continue to increase the concentration of inorganic carbon source, the inverse disproportionation denitrification efficiency wasn’t been influenced.