Real-time in situ auto-correction of K interference for continuous and long-term NH monitoring in wastewater using solid-state ion selective membrane (S-ISM) sensor assembly.

Potassium ions (K) present in wastewater has caused severe interference for NH monitoring, over-estimation of NH concentration and ultimately leads to extra energy consumption. Past effort for enhancing the selectivity of NH over K were oftentimes complex, costly, or compromised the selectivity and accuracy of the NH ion selective membrane (ISM) sensors. This study targeted this imminent challenge by developing an integrated NH/K auto-correction solid-state ISM (S-ISM) sensor assembly combined with a data-driven model to monitor [NH] under different [NH] and [K] concentrations. The results showed that the interference of K was substantially alleviated for NH measurement. The accuracy was enhanced by over 70% when examined using real wastewater and energy consumption was expected to reduce by 26% for a wastewater treatment plant, especially for wastewater with high [K]. Furthermore, the uniquely structured S-ISMs were made by embedding the ionophores in a robust polyvinyl chloride (PVC) matrix containing plasticizers and a layer of carbon nanotubes (CNT) as ion-to-electron transducer, which maintained the selectivity and accuracy of the S-ISM sensor for 4 weeks in wastewater. NH/K sensor assembly integrated with data-driven correction models poses great potential in high-efficiency and energy-saving wastewater treatment and water reuse processes.