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Electrochemical Detection of Polyphosphate Accumulation by Phosphate Accumulating Organisms for Wastewater Treatment

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July 2024

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2026-07-01

Authors

Cobb, Davis D

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East Carolina University

Abstract

Inorganic phosphates are a very common additive to fertilizers used in industrial agriculture. While these additions result in larger healthier crop yields the runoff from these macronutrients ends up within local water ecosystems. The discharge of phosphate to water systems can lead to eutrophication and long-term damage to the local environment. To treat phosphate, local wastewater treatment systems (WWTP) often use bacteria to remove phosphate from the water. These phosphate treatment organisms are termed phosphate accumulating organisms (PAO) and sequester phosphate by converting it into long chains of polyphosphate. The efficiency of this process can vary due to myriad factors; therefore, the ability to monitor if the biological processes are occurring normally is a significant WWTP need. To this end, an electrochemical biosensor was developed using Layer-by-Layer (LbL) methodology to immobilize films containing Pseudomonas putida, a model PAO, to detect polyphosphate uptake following soluble phosphate exposure. The bacterial films were exposed to electroactive methylene blue and phosphate with electrochemical monitoring using square wave voltammetry to determine methylene blue reduction currents. Currents at several potentials (vs. SCE) increase as a function of phosphate exposure, which were significantly elevated in the presence of P. putida vs. E. coli films. ICP-MS was used to show that P. putida sequesters phosphorus in significantly higher amounts than E. coli, which shows that the electrochemical output is due to poly-P accumulation on the electrode surface. The sensor was challenged with interfering ion solutions and at varying temperatures to model conditions that might be encountered at the WWTP. Overall, this study lays the groundwork for the eventual biosensor use to measure PAO health and function at WWTP.

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