HIGH-DEGREE TREATMENT OF BIOLOGICAL TREATING WATER

摘要

PURPOSE:To treat the biological treating water with a high degree without increasing the output of sludge by adding slaked lime to the biological treating water to insolubilize phosphoric acid ions in the water, then adding an inorganic flocculant, and separating the formed flocs from liquid. CONSTITUTION:Slaked lime is added to the biological treating water to insolubilize phosphoric acid ions. Since most of the phosphor compds. are converted into orthophosphoric acid by biological treatment, the addition of slaked lime to the original water after biological treatment is highly effective to insolubilization. At that time, the decrease in pH due to nitration can be prevented by adding the slaked lime into an aeration tank. Then an inorganic flocculant such as aluminum sulfate is added, and the formed flocks are separated from liquid by precipitation floating, centrifugation, etc. On that occasion, the separation effect can be improved by adding a flocculant such as polyacrylamide or its partially hydrolyzed substance, and polyacrylic acid sodium to make the flocs coarser.