| With the rapid development of economy, the continual increasing of the total wastewater by discharged and the wide use of synthetic wash, chemical fertilizer and pesticide recently, the problem of eutrophication caused by nutrition such as nitrogen and phosphorus is more serious, which not only lead the water environment to all kinds of serious harm, but also cause great economic lose. The target of nitrogen and phosphorus of effluence from the second stage city wastewater is restricted severely by Comprehensive Wastewater Discharge Standards of our country (GB8978-1996) for the purpose of preventing and managing the problem of more and more serious pollution of nitrogen and phosphorus and water eutrophication. The basic principle of wastewater biological nitrogen removal is that in the conventional second stage biological treatment, on the base of transforming organic-nitrogen to ammonia-nitrogen, ammonia-nitrogen is transformed to nitrite-nitrogen and nitrate-nitrogen through the function of nitrate bacteria, then nitrate-nitrogen is transformed to nitrogen through the function of denitrifying bacteria, thus the purpose of nitrogen removal is attained. The basic principle of wastewater biological phosphorus removal is that accumulating phosphorus bacteria can release phosphorus on the anaerobic condition and absorb phosphorus surplus from outer environment on the aerobic condition and store phosphorus in the bacteria in the form of aggregation which forms the high phosphorus sludge that is discharged from the system, thus the purpose of phosphorus removal from wastewater is attained. According to the idea of the conventional removal, ammoniation-nitrification-denitrification that during the conventional nitrogen process, these two course of nitrification and denitrification are apart on the space or on the time. Typical process of the former is A/O, A2/O , and the typical process of the later is SBR and its changeful way process. In those process, it is inevitable that the sludge age among nitrifying bacteria , denitrifying bacteria and accumulating phosphorus bacteria are not harmony because the microorganism with different function grow in one system , especially the long generation time nitrifying bacteria and other bacteria mixed growing. As the chief body of nitrification course, denitrifying bacteria is usually belonged to aotutroph and special aerobic bacteria, of which the outstanding characteristic is that the speed of multiply is very slow and the generation time is usually long. It can attain 30 days in winter, and the nitrification is very weak even in summer that the sludge age of activated sludge technology is lower than 5 days. Accumulating phosphorus bacteria is microorganism with short generation time. It is pointed in Rensink's study that efficiency of phosphorus removal is increased through reducing sludge age. In the meantime, nitrification needs condition of long sludge age and aerobic condition, otherwise, denitrification needs condition of short sludge age and anaerobic condition, releasing phosphorus needs contidion of short sludge age and anaerobic condition, absorbing phosphorus need aerobic condition. Considering the situation of the wastewater treatment in our country, one wastewater treatment process with fitting to situation in our country, high treatment function, low investment, low expending on operate and high nitrogen and phosphorus removal rate is researched and exploded urgently. On the base of learning sufficiently from the existing nitrogen and phosphorus removal at home and abroad, the cycle activated sludge and biofilm is combination organic, the study problem of removing nitrogen and phosphorus with Cycle Activated Sludge-Biofilm Technology reactor is established. CAS-BT reactor concludes biological selector and compound biological react area, of which the filling is processed by ourself and select many hole crust of polypropylene, and spume plastic is filled in it. The annular aerated conduit and discharge sludge conduit are set on the bottom of...
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