Effects of hydraulic retention time (HRT) on denitrification using waste activated sludge thermal hydrolysis liquid and acidogenic liquid as carbon sources

Waste activated sludge (WAS) internal carbon source can efficiently and economically enhance denitri-fication, and hydraulic retention time (HRT) is one of the most important operational parameters for den-itrification. The effects of HRT on denitrification were investigated with WAS thermal hydrolysis liquid and acidogenic liquid as carbon sources in this study. The optimal HRT was 12 h for thermal hydrolysis liquid and 8 h for acidogenic liquid, with NO3 -N removal efficiency of 91.0% and 97.6%, respectively. In order to investigate the utilization of sludge carbon source by denitrifier, the changes of SCOD (Soluble chemical oxygen demand), proteins, carbohydrates, and VFAs (Volatile fatty acids) during denitrification process were analyzed and three-dimensional fluorescence excitation-emission matrix (EEM) spec-troscopy with fluorescence regional integration (FRI) analysis was introduced. The kinetics parameters of denitrification rate (V-DN), denitrification potential (P-DN) and heterotroph anoxic yield (Y-H) were also investigated using sludge carbon source at different HRT.(C) 2016 Elsevier Ltd. All rights reserved.