Phosphorus Removal from Aerobic Granular Sludge: Proliferation of Polyphosphate-Accumulating Organisms (PAOs) under Different Feeding Strategies

Abstract

Aerobic granular sludge (AGS) is known for high phosphorus removal from wastewaters, and phosphorus can be recovered from high phosphorus-containing waste sludge granules. This study aimed at determining the feeding strategy that provides the best performance in terms of the proliferation of polyphosphate-accumulating organisms (PAOs) and phosphorus removal. Using three AGS bioreactors, this study compared phosphorus removal and the proliferation dynamics of PAOs under three different feeding strategies: anaerobic slow feeding (R1), pulse feeding + anaerobic mixing (R2), and pulse feeding (R3). Results indicate that R1 and R2 achieved significantly higher phosphorus removal (97.6 ± 3% for R1 and 98.3 ± 1% for R2) than R3 (55 ± 11%). The anaerobic slow feeding procedure (R1) achieved the highest specific phosphorus release rate (SPRR) and specific phosphorus uptake rate (SPUR) as compared to the other two feeding conditions. 16S ribosomal ribonucleic acid (rRNA) gene sequencing assay of the microbial community for the three feeding strategies indicated that although the feeding strategy impacted reactor performance, it did not significantly alter the microbial community. The bacteria community composition maintained a similar degree of diversity. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the dominant bacterial phyla in the system. Dominant PAOs were from the class Betaproteobacteria and the genera Paracoccus and Thauera. Glycogen-accumulating organisms were significantly inhibited while other less-known bacteria such as Wandonia and Hyphomonas were observed in all three reactors.

Feasibility Study of Applying Anaerobic Step-Feeding Mode for the Treatment of High-Strength Wastewater in Granular Sequencing Batch Reactors (GSBRs)

“…R1 and R2 had similar mean organic removal efficiencies during this stage (60 days) of 94.55± 1.4%, and 92.6 ± 2.3%, respectively. These results are consistent with previous studies of AGS systems that investigated the effect of feeding strategy on the removal efficiencies of organic substrate [15,16].…”

“…Low phosphorus removal was previously reported in GSBRs systems [30]. Comparable results were found by Iorhemen, O.T et al (2022) [16], where three GSBRs were operated for 84 days to treat an influent with COD:TN:TP ratio of 100:5:1. The results show that the phosphorus removal efficiency was about 55 ± 11% for the GSBRs that used pulse feeding without anaerobic mixing.…”

“…The effect of different feeding strategies on the proliferation dynamics of polyphosphateaccumulating organism (PAOs) and phosphorus removal has also been investigated [16]. Herein, three feeding strategies (e.g., anaerobic slow feeding, pulse feeding followed by anaerobic mixing, and pulse feeding) were applied through GSBRs.…”

“…However, phosphorus removal performance has been significantly influenced. Reactors that have anaerobic slow feeding and pulse feeding followed by anaerobic mixing demonstrated high phosphorus recovery from wasted sludge; therefore, active PAOs can be accumulated, and GAOs can be significantly inhibited within the bioreactor leading to high specific phosphorus uptake and specific phosphorus release rates [16].…”