Final Report: Reagentless Field-Usable Fixed-Site and Portable Analyzer for Trihalomethane (THM) Concentrations in Drinking WaterEPA Contract Number: EPD09028
Title: Reagentless Field-Usable Fixed-Site and Portable Analyzer for Trihalomethane (THM) Concentrations in Drinking Water
Investigators: Findlay, Mel
Small Business: KWJ Engineering, Inc.
EPA Contact: Richards, April
Project Period: February 1, 2009 through July 31, 2009
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2009) RFA Text | Recipients Lists
Research Category: SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
Description:U.S. Environmental Protection Agency (EPA) regulations require corrective action for drinking water distribution systems that exceed the maximum contaminant level (MCL) of 80 µg/L for total trihalomethanes (TTHMs). Real-time or even periodic monitoring of drinking water, however, currently is not economically feasible. Available methods use gas chromatography and are expensive and plagued with long delay times between sample collection and results. A sensor allowing rapid response, real-time measurement of TTHM concentrations in water systems would be ideal for identifying contaminant “hot spots” and allowing system operators to implement immediate mitigation.
The purpose of this research is to develop and demonstrate the feasibility of a sensitive, halogen-selective sensor and simple analytical method that can measure TTHM at concentrations below the EPA regulated level. The selectivity has been demonstrated in prior work. This research will focus on the sensor design and fabrication processes to improve accuracy, reduce power requirements, and reduce the cost of analysis.
In the 1990s, a team including the Principal Investigator for this project developed a sensor for screening groundwater contaminated by chlorinated solvents. A sensor was fabricated in a process very similar to the heated metal oxide sensor (HMOS). Unlike HMOS, this sensor was extremely selective to halogenated organic vapors while showing virtually no response to any other commonly encountered contaminant. While useful for field screening, the sensor did not have the accuracy or sensitivity needed to meet the drinking water requirements.During Phase I of this SBIR project, KWJ designed and fabricated a thick film sensor chip with the rare-earth coating on it, to compare to the original “bead-type” sensor fabricated previously. Sensitivity, repeatability, and selectivity were evaluated as functions of sensor geometry and ceramic coating composition. Next, several perm-selective sampler designs were built and tested, and sensitivity to each of the four THM compounds in water was demonstrated.
Summary/Accomplishments (Outputs/Outcomes):During Phase I, KWJ demonstrated extreme sensitivity and selectivity of the sensor. Testing showed a minimum detection limit of less than 10 ppbv for CHCl3, and less than 25 ppbv for bromoform, which is the least sensitive of the THM compounds. KWJ also demonstrated sensor response to each of the four THMs dissolved in water, with concentrations as low as 25 µg/L CHCl3 detected. Several options for rapid speciation were evaluated, with the target of <60 seconds analysis time.
1. KWJ's approach has shown the necessary sensitivity and response time for measuring low ppb levels of THM compounds rapidly.
2. Lifetime and calibration intervals for the sensor will be determined in Phase II, but have shown the potential to meet or exceed the application requirements.