PURIFICATION OF FILTHY WATER WITH ACTIVATED SLUDGE

摘要

PURPOSE:To efficiently remove, BOD, ammoniac nitric acid, etc. from filthy water, by introducing conc. sludge from a precipitating pool into an aerating cell to hold the concentration of suspended matter in activated sludge inside the cell at a specified range, and controlling the volume index of sludge in the cell below a specified value. CONSTITUTION:After being primarily purified to remove blocks, sand, etc., filthy water is introduced into an aerating cell, and an amount of oxygen required for removing BOD in the presence of activated sludge but insufficient to perform complete aerobic reaction is blown into the filthy water to decompose organic substance in it. A sludge-thickening means is independently provided to introduce a part of a mixed liquid fed out of the aerating cell or a part of returned sludge into the thickening means. A part of the obtained conc. sludge is introduced into the aerating cell to hold the concentration of suspended matter in active sludge inside the cell at 7,000-15,000mg/l and to control the volume index of sludge below 120. As a result, nitrification and denitrification can be performed in addition to the decomposition of organic substance in the filthy water inside the aerating cell.