抄録
In order to increase the efficiency of biological treatment systems, such as purification tanks for domestic wastewater, a fluidized bed biofilm filtration process that uses open cylindrical carriers (filter media) has been studied. With this process, the authors have achieved increased efficiency in the removal of organic matter and enhanced solid-liquid separation performance.
For less than 20 mg·l-1 BOD and less than 10 mg·l-1 SS in the effluent, when the filling ratio for the fluidized bed part is at 45%, the BOD volumetric loading must be less than 1.4 kg BOD5·m-3·d-1 and the BOD surface loading must be less than 5.7 g BOD5·m-2·d-1. To estimate the average inflow pattern of domestic wastewater and with an operation where 3Q water volume is recirculated per day, the filter height must be more than 200 mm and the filtration rate must be less than 1.0 m·h-1.
Through retail investigation of various design conditions, a fluidized bed biofilm filtration part has been designed for 5 persons and compared with the current contact aeration process. The volume of the fluidized bed part (aerobic treatment part) ranges from 0.1 to 0.25 m3 depending on the filling ratio, or 10 to 25% of the 1.0 m3 of a contact aeration tank. The biofilm filtration part, which carries out solid-liquid separation, has a volume of 0.045 - 0.1 m3, or 17 - 33% of the 0.3 m3 of a sedimentation tank.
Thus, the volume necessary for the biological treatment part plus the solid-liquid separation part has been significantly reduced, with increased efficiency. Future use of this system is therefore quite feasible.
