Study On The Start-up And Process Control Of Short-cut Nitrification-denitrification In Normal Temperature

As the nitrogen pollution in waters becoming increasingly serious, and the nitrogen index becoming increasingly strict, short-cut biological nitrogen removal is regarded for its advantages, such as saving energy and carbon resource, shortening hydraulic residence time, reducing the amount of sludge-discharging, and etc. Now there are a lot of studies on the start-up of short-cut nitrification reactor in a high temperature, and a few studies in a normal temperature especially in the low temperature of winter. But to a large number of urban sewages, which belong to the normal temperature and low ammonia sewage, it costs too much power to make them warming and maintain the temperature. So there is important practical significance to study on the short-cut nitrification-denitrification biological nitrogen removal under normal temperature conditions to reduce power consumption in the actual projects.First a study on the autotrophic partially nitrification in the low temperature conditions in the SBR was carried out. And the research finds were as follows: in the low temperature conditions, there also were turning points in the pH, DO curves at the end of nitrification process, which could be used to direct nitrification; and at 10 ~ 15℃in the SBR, through real time control and improving the influent pH and ammonia concentration, the autotrophic partially nitrification was implemented, and the accu- mulation rate of the nitrite passed 50% but not over 70% and unstable.In order to increase stability, the study secondly was started on the basis of mature full nitrification-denitrification sludge. By raising the temperature and reducing dissolved oxygen, first the short-cut nitrification-denitrification was achieved at a high temperature, after the accumulation rate of the nitrite achieved 85%, gradually cooling down to normal temperature, then the nitrate accumulation rate declined slightly but still more than 70%, and the short-cut nitrification-denitrification in the normal temperature was started. Then gradually increasing aeration rate, it was found that the short-cut nitrification was not damaged by a higher dissolved oxygen concentration, but the nitrate accumulation rate declined slightly. This illuminated that the system had not completely eliminated out of nitrate bacteria, but nitrite bacteria still held advantages, so the optimization of the bacteria is the key to achieve stable short-cut nitrification. It was also found that over aeration could change short-cut nitrification to full nitrification. On the sixth day after over aeration, the accumulation rate of nitrite nitrogen fell to 45% from 70%, the style of nitrification became full nitri- fication.In the end, this thesis discussed the kinetic of short-cut nitrification, got the kinetic model in the phase of short-cut nitrification.