Electroanalytical and spectroscopic approaches combined with photo(electro)catalytic treatment for real-time decision-making on rural groundwater quality

Abstract

This study presents two rapid, portable methods for monitoring drinking and groundwater quality. The first uses Square Wave Voltammetry (SWV) to semi-quantitatively assess oxidisable organic matter (SWV-index). This method, tested on commercial drinking water and on rural groundwater samples, exhibited a fair relation with total organic carbon (TOC) (in an on-off detection scheme, the Threshold Limit of Detection (LODT) for TOC was determined to be 29.02 ppm for 90 % confidence interval). Electrochemical studies of Escherichia coli and Pseudomonas syringae suspensions provided insights into the oxidation of biological matter. The second method, based on fluorescence excitation-emission spectroscopy, detected two fluorescent compound types linked to biological and organic matter, with the fluorescence factor index (FF-index) correlated with TOC (LODT = 49.29 ppm). Water quality was further monitored during laboratory photocatalytic tests and portable photoelectrochemical treatments using Bi2WO6 and WO3 under visible light irradiation. Interestingly, although both semiconductors show similar photocatalytic efficiencies, photoelectrocatalysis (PEC) is slightly enhanced for Bi2WO6 due to the greater extent of HO• formation during its electrochemically assisted photoactivation. The decrease in the SWV-index during water treatment offers a simple, fast, portable, and effective electroanalytical methodology to evaluate the viability of using PEC method in the remediation of the waters under study, thus providing a tool to accelerate decision making regarding the treatment possibilities.