혐기-간헐포기 공정에서 Denitrifying PAOs의 거동 특성

Abstract

This study investigated the occurrence and the behavior of Denitrifying Phosphate Accumulating Organisms (DePAOs). These organisms are capable of phosphorus removal and denitrification simultaneously under anoxic conditions. The experiment was conducted in two parts: The phosphorus removal efficiency was evaluated in an anaerobic-intermittent aeration process which was designed to be an Enhanced Biological Phosphorus Removal(EBPR) process: Then, several batch tests were carried out in order to elucidate how the DePAOs responds in an anaerobic-intermittent aeration process under varying conditions. In the first part of the experiment, the results show that the overall phosphorus removal efficiency is as high as 93.3% in a continuous flow system and hence the anaerobic-intermittent aeration process is in fact an EBPR process. In the batch tests, the presence of DePAOs under different anoxic conditions was observed with a limited amount of substrate. Several batch tests were run under anoxic conditions. The test samples were spiked with different nitrate concentrations of 5, 10 and 20 ㎎NO₃^- -N/L respectively. The tests revealed that both phosphorus uptake rate and denitrification rate were proportional in the first 30 min and phosphate uptake rate was 17.78∼24.89 ㎎PO₄^(-3) -P/gVSS/d and denitrification rate was 37.33∼53.33 ㎎NO₃^- -N/gVSS/d. The rate of phosphate uptake under anoxic conditions is 15.8∼26.3% slower than under aerobic conditions. With the available organic substrate, phosphates are released in anoxic condition. Results of these experiments cleary indicate that DePAOs exist under anoxic conditions in the EBPR process and that the phosphorus release and uptake under anoxic conditions depends on the presence of available organic substrate and the concentration of nitrate.