A novel AAO-SBSPR process based on phosphorus mass balance for nutrient removal and phosphorus recovery from municipal wastewater

Abstract

A novel AAO-SBSPR (Anaerobic-Anoxic-Oxic/Sequencing Batch Sidestream Phosphorus Recovery) process was developed for phosphorus (P) recovery and nutrient removal from municipal wastewater. Meanwhile, an operational strategy based on the P mass balance for the process was proposed, where P recovery rate was coupled with sludge retention time (SRT) so as to reduce the impact of P recovery on P content in activated sludge and maintain a stable operation of the process. The results show that the proposed operational strategy is helpful for the stable operation of the AAO-SBSPR process and up to 65% of the influent P was recovered with the phosphate removal efficiency of 99.1%. Both P recovery and extended SRT had limited influence on the P release and uptake rates of polyphosphate accumulating organisms (PAOs). The results of high-throughput sequencing analysis indicated that the relative abundance of Accumulibacter increased while SRT was extended under high P recovery rate. Moreover, significant promotion of simultaneous nitrogen removal and P uptake was observed, where the ratio of anoxic P uptake to the total P uptake of the whole process increased from 41.7% in the AAO process to 77.5% in the AAO-SBSPR process, combined with the increase of total nitrogen (TN) removal efficiency from 71.9% to 80.4%. The P recovery process is also beneficial for the reduction of sludge production and nitrification process as SRT was extended for high P recovery rate. Overall, the AAO-SBSPR process together with the operational strategy proposed in this study provides a promising and practical alternative for P recovery from municipal wastewater.

Keywords: AAO-SBSPR process; Nutrient removal; Operational strategy; P mass balance; Phosphorus recovery; Sludge retention time.