Biological Nitrogen Removal from Nitrogen-Rich Wastewaters by Partial Nitrification and Anaerobic Ammonium Oxidation

摘要

PURPOSE: A system for advanced biological wastewater treatment by partial nitrification (NH4-NNO2-N) and anaerobic ammonium oxidation is provided to effectively treat nitrogen-rich wastewater with no supply of external carbon source. CONSTITUTION: Wastewater is first introduced into a precipitation tank(1) before it is treated in an intermittent aeration SBR(2), because organics and phosphorus of raw wastewater inhibit anaerobic ammonia oxidation in the intermittent aeration SBR. In the precipitation tank phosphorus up to 90 % and organics up to 75 % are removed by chemical precipitation. The intermittent aeration SBR process consists of partial nitrification, denitrification and reaeration. The partial nitrification lasts until SCOD/NO2-N become 2, and represented as follows,(2NH4¬+)+(3O2)(2NO2¬-)+(4H¬+)+(H2O)(partial nitrification/aerobic). After partial nitrification the intermittent aeration SBR is alternated to anoxic condition for denitrification, by which organics are consumed. This reaction is represented as shown below,(2NO2¬-)+(CH3)OH+(CO2) (N2)+(2HCO¬-)3+(H2)(denitrification/anoxic). These alternative reactions are repeated until the ratio of NH4-N/NO2-N become 1:1.3. For the optimal operation, the temperature of wastewater is maintained with the range of 30 to 35 deg.C and sludge retention time (SRT) is controlled to be 1.0 to 3.0 days. After wastewater is treated in the intermittent aeration SBR process, it enters into a deaeration tank(3) where oxygen an inhibition factor of anaerobic ammonia oxidation is removed and settled sludge is withdrawn. Effluent from the deaeration tank is introduced into a continuous media reactor (SMR,4) for allowing wastewater to come into contact with fixed media when directed downward and fluidizing media when directed upward. The anaerobic ammonia oxidation process is represented as shown below, (NH4¬+)+(1.3NO2¬-)+(0.0425CO)2(1.045N)2+(0.22NO3¬-)3+1.87(H2O)+(0.09OH¬-)+(0.0425CH)2. For the optimal operation, the temperature of wastewater in the continuous media reactor is maintained with the range of 30 to 35 deg.C, hydraulic retention time (HRT) is controlled to be 1.5 to 2.0 days and pH 7 to 8.