Abstract
In order to improve nitrogen removal efficiency, an anaerobic filter-aerobic biological filtration process was modified by filling. with nitrifying bacteria immobilized carrier made of polyethylene-alcohol (immobilized pellets) as a media for biological filtration tank. The effect of water temperature on T-N removal efficiency was investigated.
When aeration was performed so that the immobilized pellets were fluidized above the ceramic carrier filled in the biological filtration tank, T-N was successfully removed. T-N removal efficiency was increased by increasing the filled ratio of immobilized pellets by replacing a portion of the ceramic carrier at the water temperature of 10°C. Conversely, the removal efficiency was lower when the filled ratio of immobilized pellets was 60%, due to the increase of suspended solids in the effluent. Therefore, a proper filled ratio of immobilized pellets was thought to be about 50%.
The nitrification rate at the water temperature of 5°C was 17 mg·l-1·h-1 for the immobilized pellets and 3.9 mg·l-1·h-1 for the ceramic carrier, thus the nitrification rate of the former was 4.4 times that of the latter. Removal rates of the inflow carbon and nitrogen were 72% as carbon dioxide and 65% as nitrogen gas, respectively.
