Development of a Flow-Batch Analyzer for the On-Site Automated Determination of Residual Chlorine in Drinking Water

A novel automated analyzer for the determination of residual chlorine in water was developed and evaluated. The analyzer is based on the technique of flow-batch analysis and employs the DPD photometric method for measurement of free chlorine. To decrease complexity, a stirrer was not used for mixing, resorting instead to the turbulence of the fluids to attain a satisfactory mixing of the reactants. The prototype was built using peristaltic pumps, a reaction-detection cell, and an LED-photodiode detection system. The open-source Arduino microcontroller platform was used for data acquisition and control. The operational evaluation of the system included the study of the mixing process, the determination of the optimum concentration of DPD reagent and the calculation of analytical figures of merit: linear range, precision and accuracy of the results, as well as detection and quantification limits. The performance of the analyzer was deemed fit for the purpose of on-site analysis. This prototype is being taken as the basis for the design of an industrial-grade on-site on-line analyzer for the determination of residual chlorine in water treatment plants and drinking water distribution systems.