Super-lightweight, low-cost and wireless water quality monitor for remote chlorine rate management in water-circulating cooling facilities

There is a growing demand for the continuous monitoring of residual chlorine in water-circulating cooling facilities to remotely maintain concentrations within an appropriate range. This study aims to develop a lightweight, low-cost, and wireless water quality monitor. We further propose a highly simplified and miniaturized configuration based on a wet chemical analysis method, which combines a liquid delivery mechanism driven by water head pressure, rather than a high-precision pump, with a low-power latch valve. Furthermore, to prevent fluctuations in flow path resistance, we adopted a glass-made mixing and reaction flow path device fabricated using imprint processing, which offers excellent surface smoothness and high rigidity. The evaluation results demonstrated that this monitor's flow system achieves highly stable flow behaviour while reducing reagent consumption to less than 1/10 (a few μL per measurement). Under these stable flow conditions, we confirmed sufficient analytical performance for measuring the residual chlorine rate in cooling water. Furthermore, in a demonstration test using a small-scale circulating cooling unit, we confirmed that the signal response of the monitor was perfectly synchronized with changes in chlorine concentration following periodic additions at 60 min intervals. Consequently, a super-lightweight, extremely low-cost, and fully wireless water quality monitor is ready for use.