Combining partial nitrification and post endogenous denitrification in an EBPR system for deep-level nutrient removal from low carbon/nitrogen (C/N) domestic wastewater

Abstract

In this study, partial nitrification and post endogenous denitrification (PED) were combined with enhancing bacterial phosphorus removal (EBPR) in an anaerobic/aerobic/anoxic operated sequencing batch reactor (SBR) for deep-level nutrient removal from low carbon/nitrogen (C/N, chemical oxygen demand (COD)/total nitrogen (TN)) domestic wastewater. At anaerobic stage, abundant organic matters (96.6% of COD consumption) in raw wastewater were stored as poly-hydroxyalkanoates (PHAs) by phosphorus and glycogen accumulating organisms with enhanced activities, which provided sufficient intracellular carbons for subsequent aerobic phosphorus uptake and anoxic PED. By controlling suitable aeration rate and duration, high nitrite accumulation rate (97.2%) was obtained at aerobic stage, which saved intracellular carbons consumption of PED. Moreover, the subsequent utilization of glycogen after PHAs via PED ensured the deep-level TN removal (94.9%) without external carbon addition. After 160-day operation, the average effluent PO₄^3--P and TN concentrations were 0.4 and 3.0 mg/L, respectively, at C/N of 3.1.

Keywords: Enhanced biological phosphorus removal (EBPR); Glycogen accumulating organisms (GAOs); Partial nitrification; Phosphorus accumulating organisms (PAOs); Post endogenous denitrification (PED).