Reagentless Field-Usable Fixed-Site and Portable Analyzer for Trihalomethane (THM) Concentrations in Drinking Water

Environmental Protection Agency rules stipulating corrective action for drinking water distribution systems that exceed the maximum contaminant level (MCL) for total Trihalomethanes (TTHMs), 80mg/L. Real-time, or even periodic, monitoring of drinking water is not economically feasible. Current methods use gas chromatography, and are expensive and plagued with long delay time between sample collection and results. Lab analysis requires sample collection, packaging and shipping, tracking and recordkeeping, and disposal of samples. A sensor allowing rapid response, real time measurement of TTHM concentration in water systems would be ideal for identifying contaminant ¿hotspots¿ and allowing system operators to implement immediate mitigation. A team including the PI¿s developed such a sensor in the 1990¿s. This sensor was fabricated from a mixture of lanthanum oxide and lanthanum fluoride sintered in a silica matrix, a procedure very similar to that used for the heated metal oxide sensor (HMOS0. Unlike HMOS sensors, this sensor was extremely sensitive to chlorinated organic vapors while showing no response to any other commonly encountered contaminant. Power consumption and short lifetime of sensor made it impractical except of screening applications. Current work by the KWJ staff has resulted in an extremely low power, MEMS (microeletrome systems) based sensor platform. Up to four classes of chemical sensors can co-exist on the single first generation U-MEMs platform. The sensor platform can be configured to look at a specific chemical (or class of chemicals) or detection of multiple analytes via a sensor array and pattern recognition. Furthermore, the extremely small size of the MEMS structure enable operation at very low power, even for those devices such as the R-Cl sensor, which require an internal heater for operation. In R&D prototypes, we have operated the U-MEMS structure at less than 1.7mW continuous power for thermal detection of VOCs, thus allowing extended operation under battery power for a heterogeneous sensor array. The goal of this project is to develop and demonstrate feasibility of a MEMS sensor-based prototype hardware and a simple analytical method that can measure TTHM at concentrations below the EPA regulated level of 80mg/L in water. KWJ will design, fabricate, and package a U-MENS sensor chip with the rare earth functionalization on it, demonstrate that it is responsive to THM.