Study On Shortcut Nitrification-denitrification In Synthetic Ammonia Wastewater

Heavy pollution of synthetic ammonia industry is one of the important reasons caus-ing water ammonia nitrogen exceeds bid badly. High ammonia concentration, low with CODCr and BOD5, and containing a certain amount of mineral oil, sulphur, cyanide is the main cause of the synthetic ammonia industry wastewater which is difficult to effectively handle. Presently, the main technologies have steam stripping, stripping method, ion ex-change, chemical precipitation, biological nitrogen removal technology and so on. Com-pared with other methods, however, the biological nitrogen removal technology has the advantages of lower energy consumption and avoiding secondary pollution. And the short-cut nitrification denitrification has the advantages of lower oxygen consumption, saving carbon sources dosing quantity, less sludge production, especially for dealing with the high concentration ammoniac wastewater and high N/C. At present, we have made certain achievements in this filed, but there is rare in the actual production or research on medium scale, most still remain in the experimental stage. In order to effectively prevent ammonia emissions of industrial wastewater ammonia nitrogen load, we need to develop efficient biological denitrification technology urgently based on the existing laboratory studies.This experiment studied at the condition which was ambient temperature, air control in 40 m3/h, dissolved oxygen concentration in the nitrification process of 0.28～ 1.06 mg/L, mixed liquor suspended solids concentration was about 4000 mg/L, settling velocity was 30%. And this led the competition between the two classes of nitrifying bacteria, generated dynamic choice, inhibited the proliferation of nitric acid bacteria, and also eliminated nitric acid bacteria from the system gradually by controlling the sludge age in 5-8 d, then made the nitrite bacteria dominant position. The shortcut nitrification denitrification process in synthetic ammonia wastewater would be realized. Based on the experiment, we had ob-served that changes single factor - aeration, influent pH, initial C/N (CODCr-and NH4+-N concentration ratio), it impacts on ammonia oxidation rate and nitrite accumula-tion rate. The experimental result suggested that the proper aeration, pH and initial C/N for shortcut nitrification in synthetic ammonia wastewater was about 40 m3/h, pH was about 8.5(maintain the original influent pH), initial C/N was about 4. Under controlled condition of each single factor, nitrite accumulation rate were 92.7%,92.7% and 93.9%respectively at the end of the aeration. We further explored correlations between the transformation of "three kinds of nitrogen" (NH4+-N,NO3--N,NO3--N) and the DO and pH changes, and their first-order derivative with time in the shortcut nitrification denitrification process. We found the DO and pH which could regard as control signals in shortcut nitrification denitri-fication process was feasible, then the real-time control strategy was established. Finally, we made a comprehensive experimental study about the single factor control conditions, and built the real-time control strategy according to the DO and pH. Selected the following more than two months of actual operation with controlling conditions close to 15 cycles run results, we found that CODCr removal rate was about 85%, effluent ammonia nitrogen tested for no basically, nitrite accumulation rate was approximately 95%, TN removal rate was close to 90%.