Phosphorus recovery from municipal wastewater with improvement of denitrifying phosphorus uptake based on a novel AAO-SBSPR process

Abstract

Both synthetic and real municipal wastewaters were used to verify the applicability of a novel AAO-SBSPR (Anaerobic-Anoxic-Oxic/Sequencing Batch Sidestream Phosphorus Recovery) process developed for the phosphorus (P) recovery and nutrients removal. P recovery strategy based on P mass balance of the process was employed where sludge retention time (SRT) of the systems was extended. Meanwhile, the anoxic/aerobic volume ratio was increased to enhance the activity of denitrifying P uptake. The results show that up to 59.8% and 75.2% of P from real and synthetic wastewaters were continuously recovered at the SRT of 35 d, respectively. The lower P recovery efficiency of the system fed with real wastewater was due to its lower influent P load and P content in activated sludge after P recovery was decreased from 0.059 mgP/mgVSS to 0.033 mgP/mgVSS. The analysis of the kinetic and stoichiometric parameters suggested that activities of the polyphosphate accumulating organisms (PAOs) in P recovery systems were retained under high P recovery efficiency, and more glycogen was degraded to provide energy for acetate uptake. This resulted in the highest average TP removal efficiency of 94.0% for the AAO-SBSPR process fed with real wastewater. Moreover, the enhancement of denitrifying P uptake activity was observed in P recovery systems. It was further improved by increasing the volume of the anoxic tank, which resulted in better TN removal performance. Meanwhile, the diversity of the microbial community was increased as the system was changed from the AAO process to the AAO-SBSPR process, and the relative abundances of the key functional bacteria such as nitrifiers, denitrifiers, PAOs and DPAOs were increased which strengthened the N-related metabolic pathways of the system remarkably.