Integration Of A / O Biofilm Reactor Denitrification Characteristics

Traditional biological nitrogen removal processes either need several separated tanks with different DO concentrations, or need sequential aerobic and anoxic environment in turn in a single reactor. Thus these processes have many shortcomings, such as high cost of facility construction, large consumption of energy, low nitrogen removal efficiency and high cost of operation. As to these shortcomings, an integrative biofilm reactor is designed, which can realize carbon and nitrogen removal simultaneously in a single tank and can also realize circulation necessary for nitrogen removal only by aeration.First, flow field in the integrative reactor are tested with PIV and then the reactor is modified according to the testing results. Second, research is carried out on carbon and nitrogen removal in domestic wastewater with the modified reactor. Finally, mechanism of the reactor and also effects of operating conditions, such as influent COD/TN and aeration rate on the reactor's removal efficiencies are investigated with synthetic wastewater. The following conclusions can be obtained.(1) Oxic and anoxic environment can be created simultaneously in the integrative reactor, and nitrifying liquid can be circulated without pump in the reactor, thus the electric consumption and the cost of facility construction could be reduced.(2) The research results of domestic wastewater show that when HRT is 24h and temperature is between 20 to 24 degrees centigrade, the COD removal efficiency is about 90%, nitrification rate and TN removal efficiency reach 85% and 70%. The effluent concentration of NOa-N and NO2-N are about 15mg/L and Img/L respectively. When it comes to synthetic wastewater, the reactor has better removal efficiencies.(3) Carbon is benefit for denitrification, but is disadvantageous to nitrification. The experiment results indicate that when the ratio of influent COD/TN is 5, the reactor's nitrification ability and denitrification ability could match each other best.(4) The integrative reactor's nitrogen removal process is based on the following two aspects. One is that nitrification is mainly displayed in the oxic section and denitrification is dominantly carried out in the anoxic section and they harmonize with each other by circulation. And the other is that nitrification and dinitrification could be displayed simultaneously in each seation.