Growing an Enhanced Culture of Polyphosphate-Accumulating Organisms to Optimize the Recovery of Phosphate from Wastewater

Abstract

Having certain bacteria called phosphorus-accumulating organisms (PAOs) is important for getting rid of phosphorus (P) in wastewater from homes. This happens in a process called enhanced biological phosphorus removal (EBPR), where PAOs are active in activated sludge. To design and make EBPR processes work better, we need to have an in-depth understanding of how PAOs work. The best way to learn about them is by studying them in a laboratory. This study undertook to culture these microorganisms in the laboratory. A University of Cape Town membrane bioreactor (UCTMBR) activated sludge (AS) system was used to grow the microorganisms and see how well it worked. This paper looked at what type of substrate PAOs like best, either acetate or propionate, and how providing them with more of their preferred substrate affects how they grow. During the process, it was observed that P was not released or taken up significantly when acetate was added to the influent. The levels were consistently low at around 5.74 ± 4.47 mgP/L infl (release) and 19.9 ± 7.17 mgP/L infl (uptake). The signs become much better when propionate was used instead of acetate. When the amount of propionate in the influent was increased from 50% to 76% (as a percentage of influent total chemical oxygen demand), the amount of P released went up to 155 ± 17.7 mgP/L infl, and the amount of P taken up went up to 213.7 ± 11.4 mgP/L infl. The proof given indicated that propionate is preferred by PAOs. This study found that when more propionate was added to the wastewater, the concentration of PAO biomass went up. This was shown by certain signs that PAOs display when they are present. Results presented in this journal article emanate from an MSc Thesis (Thela, 2022) published in open-source UCT.