PURPOSE: To shorten the treating time in the method for removing nitrogen and phosphorus from waste water in batches by detecting the end nitration point in the nitration stage and the end denitrification point in the denitrification stage by the change of an oxdidation-reduction potential and successively changing the succeeding stages.
CONSTITUTION: In the activated-sludge treatment, methanol is added in the initial anaerobic stage (2) when the org. matter is deficient in the waste water discharged from a biological reaction tank 1 in the denitrification stage, and activated sludge is charged as a second stage. An aerobic stage (1), anaerobic stage (2), aerobic (2), settling, discharge and standby stages are successively conducted. The ammoniacal nitrogen is nitrated in the aerobic stage (1), and the nitrate nitrogen is removed in the anaerobic stage (2). In this case, the time when an increment of the oxidation-reduction potential amounts to <0.5mV /min in the nitration stage is considered to be the nitration end point, and the time when a decrement of the potential becomes >1.2 times the preceding decrement in the denitrification stage is considered to be the denitrification end point.
MIKI OSAMU
ITO AKIRA
