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

Environmental Protection Agency rules stipulate that corrective action be taken for drinking water distribution systems that exceed the maximum contaminant level (MCL) for total Trihalomethanes (TTHMs) 80μg/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 time delays between sample collection and results.  Laboratory 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 PIs developed such a sensor in the 1990s.  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 (HMOS).  Unlike HMOS sensors, this sensor was extremely sensitive to chlorinated organic vapors while showing no response to any other commonly encountered contaminant.  High power consumption and the short lifetime of the sensor made it impractical except for use in 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 detectmultiple 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 the 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 80μg/L in water.  KWJ will design, fabricate, and package a U-MENS sensor chip with the rare earth functionalization on it and demonstrate that it is responsive to THM. Phase I proposal goals: The overall 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 80μg/L in water. The experimental goal is to design, fabricate, and package a U-MEMS sensor chip with the rare-earth functionalization on it, demonstrate that it is responsive to THM by putting it into a membrane sampled flow path, and record the signal for RHM vs. standard solutions of THM in water. A further goal is to develop a practical design for a prototype instrument that integrates the U-­MENS sensor with the passive water samples.