SIMULATION OF THE OPERATING-CONDITIONS OF THE MUNICIPAL WASTE-WATER TREATMENT-PLANT AT LOW-TEMPERATURES USING A MODEL THAT INCLUDES THE IAWPRC ACTIVATED-SLUDGE MODEL

There are some advantages to using the sewage system to transport and melt snow in snowy regions. Since this would cause a drop in sewage temperature, adequate methods of operating treatment plants at low temperatures should be addressed. First, calibration of the IAWPRC activated sludge model was done using pilot plant data from a 10 degrees C experiment. Then, the temperature coefficients in the reaction rate equations were estimated using the data from operation at 5 degrees C. Comparison of the simulation results with data gathered under other temperature conditions showed that the IAWPRC activated sludge model could be applied to low temperature conditions. A newly developed model of the full-scale plant was able to simulate not only the biological reaction in the aeration basin but also the performance of primary and final clarifiers, and sludge thickening and dewatering processes. The sludge and cake production rates, MLSS, and nitrification performance calculated by this model coincided with plant operation results at 12 degrees C. Operation maps of the plant in Sapporo were drawn at presumed low temperatures, 4 and 8 degrees C. They showed that if nitrifying bacteria were kept in the plant an overload in the sludge treatment process would be unavoidable without augmenting the capacity of water or of the sludge-treatment system.