Start-up of Anaerobic Ammonium Oxidation Reaction in UASB Bioreactor

The start-up of anaerobic ammonium oxidation(ANAMMOX) process and operational characteristics in a 3.2 L Upflow Anaerobic Sludge Blanket(UASB) reactor seeding with activated sludge from a municipal sewage treatment plant was investigated.The UASB bioreactor was feed with artificial wastewater composed of ammonium and nitrite at proper NH_4~+-N/NO_2~——N ratio and the influent dissolved oxygen concentration of 2.7～3.2 mg/L.The results demonstrated that ANAMMOX process was achieved successfully with high removal efficiencies of NH_4~+-N and NO_2~——N upto 99.6% and 75.4% after 119 day's of operation and acclimation.The removal efficiencies of NH_4~+-N,NO_2~——N and TN could reach as high as 99.9%,99.9%,and 91.2% after the concentration of NH_4~+-N increased form 50 mg/L to 70 mg/L and the ratio of NH_4~+-N to NO_2~——N was equal to 1∶1.32.Furthermore,the average ratio of removed ammonia,removed nitrite and produced nitrate was 1∶1.54∶0.30 at the stable stage of the process.The effluent pH kept around 8.4 and the alkalinity varied a little.The biomass obtained with high ANAMMOX activity was brown.The grain-sludge of brown was found at the bottom of the bioreactor.The operation showed that the volume load and the temperature of reaction part could influence the running of the bioreactor.