BIOLOGICAL NITRIFYING AND DENITRIFYING METHOD FOR NIGHT SOIL TYPE SEWAGE

摘要

PURPOSE:To subject sewage to efficient nitrification and denitrification treatment by setting the water temperatures in nitrification process and denitrification process and the activated sludge concn. of the nitrification process at specific ranges and circulating the specific amount of NOX in the nitrification process to the denitrification process. CONSTITUTION:In biologically treating night soil type sewage by providing a denitrification process 4 to the prestage of a nitrificatin process 6 and circulating the nitrified liquid to the denitrification process, the water temperatures of the process 6 and the process 4 are kept at 25-42 deg.C, and the activated sludge concn. of the process 6 is maintained at 10-40g/l. Thence, 70-95% of the NOX formed in the process 6 is circulated to the process 4, and the treatment is performed while the number of days of the night soil type sewage stagnating in the process 6 and the process 4 are being kept at 0.5-5.0 days respectively. Thereby, the nitrifying and denitrifying device is efficiently reduced in size and both the installation area and construction cost thereof are considerably reduced.