抄録
Bacterial population dynamics and nitrification characteristic of immobilized activated sludge have been investigated during acclimation procedure to inorganic synthetic wastewater (NH4-N 20mg·l-1). A 1.5 liter reactor was operated at 20 °C with a hydraulic retention time of 3 hours for the start-up and 1 to 3 hours after 2 years. Number of nitrifying bacteria in pellet entrapping activated sludge increased around 103 times in the first 10 days and reached to a higher level of 108 to 109 cells·ml-1-pellet. The higher level was still maintained after 2 years. At the same time heterotrophic bacteria existed 108 to 109 cells·ml-1-pellet throughout the operation. Electron micrographs of cross sections of pellet, both in the start-up period and after 2 years, suggested the coexistence of nitrifiers and heterotrophes both of which formed respective colonies. It was confirmed that the nitrification activity increased 3 times when the number of nitrifying bacteria increased 10 times.
