On-linemonitoring of a BNR process using in situ ammonium and nitrate probes and biomass nitrification-denitrification rates in an intermittently aerated and pulse fed bioreactor

摘要

BACKGROUND: The need to monitor and optimize biological nitrogen removal (BNR) processes has led to the use of on-line instrumentation. In situ located sensors can monitor in a real-time mode the dynamics of microbial processes, providing the opportunity to understand and optimize process performance. RESULTS: A nitrification-denitrification process wasmonitored on-line for the first time in an intermittently aerated and pulse fed activated sludge system using in situ located sensors for ammonia and nitrate. Pulse feeding created a reduced C/N ratio gradient across the anoxic phase, resulting in complete denitrification within a period of 20 min. Two denitrification rates were determined, corresponding to nitrate reduction during utilization of the readily biodegradable (0.110-0.246 g g-1 d-1) and the slowly (particulate) biodegradable (0.032-0.041 g g-1 d-1) COD, respectively. Despite the fact that the initial C/N ratio at both Food/Microorganism ratio (F/M) 0.20 and 0.28 was decreased from 4.8 to 1.8 at the end of the anoxic phase, the C/N ratio decrease was twice as fast at the higher F/M ratio. CONCLUSION: Pulse-feeding resulted in higher C/N ratios at the beginning of the anoxic phase, creating a reduced C/N ratio gradient during the denitrification period. Organic load was mostly consumed during the anoxic phase, resulting in high nitrification efficiency, low oxygen requirement and saving energy.