Study On Denitrification Mechanism And Key Technologies Of Wastewater Treatment With MBBR

In recent years, the excess emissions of nutrients such as nitrogen and phosphorus cause eutrophication phenomenon growning, brought harm to the ecological environment and human health. Controlling and reducing emissions of nitrogen and phosphorus has become one of the countermeasures to combat eutrophication. The excess emissions of nitrogen and phosphorus in the wastewater treatment plant are the main reason for the eutrophication. Therefore, our country increases some binding targets in the overall planning of social and economic development during the period of the "Twelfth Five Year". In this situation, many sewage treatment plants in our country are facing an urgent requirement of upgrading and reconstruction.MBBR (Moving Bed Biofilm Reactor) is the preferred technology for upgrading and reconstruction of sewage treatment plants. This paper used a composite technology of MBBR and A/O to treat domestic wastewater in a productive experiment research. The test results showed that:when the temperature is at25±1℃and HRT is7h, this technology has a higher removal rate of COD and ammonia nitrogen, the average removal rate was89.7%and96.5%respectively, the effluent COD and ammonia nitrogen maintain stable under50.0mg/L and5.00mg/L, all reach the grade A standard of GB18918-2002, its ability to resist impact load is enhanced significantly relative to conventional treatment system. Temperature is more obvious impact on the system, as the temperature falls, the removal of ammonia nitrogen decreased, this showed that denitrifying bacteria is more sensitive to temperature. Through a study on the filler’s contribution to the denitrification effect, the results showed that the biofilm of packing plays a major role in the removal of ammonia nitrogen.At low temperature (8℃-13℃), investigated the removal performance of the pollutants in domestic wastewater at different hydraulic retention time (8.4h,16.8h and12.1h) by adopting a two-stage MBBR process. Integrated its removal efficiency and economic factors, determined a more appropriate HRT is12h of the system. Under this condition, the two-stage MBBR process has a higher removal rate of COD and ammonia nitrogen,87.9%and98.1%, respectively, the effluent COD is lower than50mg/L, with an average of about35.1mg/L, and the effluent ammonia nitrogen is lower than5mg/L, with an average of about2.00mg/L, all are better than the grade A standard of GB18918-2002. The results also show that, with the shortening of HRT, the two-stage MBBR process on volumetric COD removal load increases gradually, and on volumetric ammonia nitrogen removal load increases gradually with reducing of HRT in a certain load, but when the HRT reduced to a certain range, the system on volumetric ammonia nitrogen removal load will be reduced along with the shortening of HRT. Through a batch test on the characteristics of contaminant removal by MBBR paragraphs filler, the results showed that two-stage MBBR process on degradation of COD ocuurs mianly in aerobic I segment, and heterotrophic bacteria is the dominant flora; degradaton of ammonia nitrogen ocuurs mianly in aerobic II segment, and the dominant flora is nitrifying bacteria. And aerobic Ⅱ segment segment filler exhibit stronger activity than aerobic I segment.On MBBR integrated device running, we found problems of grille blockage and sludge floating in sedimentation tank, this paper analyzes the problems and put forward some solving measures. And according to the coagulation test for sludge floating problem, the PAC dosing can be an effective solution to sludge floating, at the same times, it also remove phosphorus in depth, and make the effluent of TP content is better than the grade A standard of GB18918-2002.