Effect of phosphorus load on nutrients removal and N2O emission during low-oxygen simultaneous nitrification and denitrification process

Abstract

Three laboratory scale anaerobic-aerobic (low-oxygen) SBRs (R1, R2 and R3) were conducted at different influent phosphorus concentration to evaluate the impacts of phosphorus load on nutrients removal and nitrous oxide (N₂O) emission during low-oxygen simultaneous nitrification and denitrification (SND) process. The results showed that TP and TN removals were enhanced simultaneously with the increase in phosphorus load. It was mainly caused by the enrichment of polyphosphate accumulating organisms (PAOs) under high phosphorus load and low COD/P ratio (<50), which could use nitrate/nitrite as electron acceptors to take up the phosphorus. N₂O emission was reduced with increasing phosphorus load. N₂O-N emission amount per cycle of R3 was 24.1% lower than that of R1. It was due to the decrease of N₂O yield by heterotrophic denitrification. When the phosphorus load increased from R1 to R3, heterotrophic denitrification (D) ranged from 42.6% to 36.6% of the N₂O yield.

Removal of nitrogen by heterotrophic nitrification–aerobic denitrification of a phosphate accumulating bacterium Pseudomonas stutzeri YG-24

“…Jia et al (2013) reported that in the alternating anaerobic and aerobic bioreactor, the presence of adjacent aerobic and anoxic microzones benefited simultaneous N and P removal due to the activities of denitrifying phosphorus accumulating organisms (DPAOs). However, the composition of the consortium was unclear, and the DPAOs were only enriched in the anoxic phage, its application in real practice was restricted.…”

Microbial community characteristics during simultaneous nitrification-denitrification process: effect of COD/TP ratio

“…Both TP and TN removal efficiencies were enhanced along with the decrease of COD/TP ratio, and R3 gained relatively high nitrogen and phosphorus removal efficiency under low COD/TP ratio. It was mainly achieved by some PAOs capable of denitrification, i.e., denitrifying PAOs (DPAOs), using PHA stored in the anaerobic stage as carbon source and nitrite/nitrate as electron acceptors (Jia et al 2013a).…”

“…The effect of COD/TP ratio on SND performance (i.e., nutrients removal efficiency) has been reported in our previous work (Jia et al 2013a). As a more fundamental follow-up work, the main effort herein was focused on the microbial community characteristics in order to better understand the underlying mechanisms regarding the impact of COD/TP ratio on SND performance.…”

“…Synthetic wastewater with same COD and ammonium but different TP concentrations were fed into three SBRs, corresponding to the average influent COD/TP ratios of 91.6, 40.8, and 27.6 for R1, R2, and R3, respectively, and theoretical COD/TN ratio of 10.0 for all three reactors. The schematic diagram of the SBR system and detailed composition of synthetic wastewater can be found in our previous work (Jia et al 2013a). …”

“…The operating parameters of SND processes, such as oxygen concentration (Hocaoglu et al 2011), temperature (Zhang et al 2009), and C/N ratio (Chiu et al 2007), were found to significantly affect microbial metabolisms, and consequently nutrient removal performance. C/P ratio is reported to significantly influence the nutrients removal and is an essential factor for the optimization of wastewater treatment process, such as anaerobic-anoxic/nitrification sequencing batch reactor (A 2 N-SBR) (Wang et al 2009), UniFed SBR process (Zhao et al 2008), and SND process (Ge et al 2010, Jia et al 2013a. However, to date, special attempts have not yet been devoted to investigating the impact of chemical oxygen demand (COD)/ total phosphorus (TP) ratio on the performance of SND processes in terms of microbial community characteristics.…”