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

EPA Contract Number: EPD10060
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
Phase: II
Project Period: May 1, 2010 through April 30, 2012
Project Amount: $224,713
RFA: Small Business Innovation Research (SBIR) - Phase II (2010) RFA Text |  Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Water and Wastewater

Description:

In this SBIR project, KWJ Engineering (KWJ) developed a MEMS planar sensor chip with the rare-earth sensory coating on it and demonstrated that it is responsive to THMs at low ppb levels. In Phase I, KWJ fabricated and tested a planar version of the sensor, demonstrating the ability to detect ppb-levels of the THMs. In Phase II, KWJ worked to optimize this sensor and develop an instrument/method for effective monitoring of TTHM in drinking water that could provide a new field capability for environmental monitoring, saving significant time and cost in implementing EPA drinking water standards. The Phase II research effort focused on putting the sensor on the MEMS platform, optimizing the method and sampler design, building a field prototype instrument, and validating a simple sensor-method with a target of <10ug/L for all THM species. The resulting analyzer was tested in the laboratory for analytical level monitoring of drinking water for TTHMs. This sensory approach would enable THM analysis virtually anywhere, anytime, on-the-spot, and at low cost. Additional applications were studied as potential commercial markets and included pool and spa monitoring, as well as industrial water and groundwater measurements and landfill analysis.

Summary/Accomplishments (Outputs/Outcomes):

KWJ fabricated and tested a planar version of the MEMS sensor, demonstrating the ability to detect <5ppbv CHCl3, and <15ppbv CHBr3 in gas phase. Using a commercially available cartridge of thin-wall silicone tubes, KWJ achieved detection limits of <10 and 20ug/L, respectively, in water and without pre-concentration with the MEMS and planar non-optimized sensor. This sensor, therefore, can meet the EPA requirement for sensitivity. Laboratory testing also demonstrated the ability to speciate the 4 THM compounds using a 4 sensor array using this sensing technology. The instrumentation developed demonstrated that field methods will be possible with the sensory approach to TTHM monitoring.
 
Although virtually all of the analytical milestones have been achieved, one unanticipated hurdle to successful completion of field demonstration was the instability of the coated MEMS sensor platform. Although KWJ's rare-earth halogenated hydrocarbon sensitive coatings were applied to both planar alumina and MEMS SiC substrates, successfully achieving ppb-level sensitivity, long-term stability was elusive. At elevated temperatures, many of the coatings cracked and de-laminated from the substrate, resulting in very short operating lifetimes. The level of research and process development to resolve this MEMS fabrication hurdle was outside the scope and budget of this project. A new MEMS substrate will be required to stabilize high temperature operations so that the low-cost MEMS sensor can enable the analytical measurement sought over time.

Conclusions:

All of the project objectives were met: the sensor was placed on a low-cost MEMS substrate, the instrumentation and method for ppb-level monitoring was demonstrated, the sampling interface was effective and laboratory comparisons to the existing methods were accomplished. The potential applications for this sensory approach to TTHM monitoring would be large in EPA and spin off applications. However, for commercial success, improved stability and lifetime for the MEMS sensor platform must be addressed. The simplicity of the resulting monitor (no carrier gas, no consumables or reagents) would allow operation by facility staff with little or no training in comparison to current requirements for operation of complex instrumentation such as gas chromatographs or GC/MS based methods. The portability and comparatively low cost of a MEMS sensor approach would enable higher quality and more frequent online monitoring for EPA drinking water and other applications in more locations and at more times with sample transfer issues.

While all of the analytical requirements for the technology have been demonstrated, commercial progress will require additional work not to improve the sensitivity but rather to improve the stability and lifetime of the MEMS sensor platform. KWJ has found several potential commercial partners and demonstration sites and currently is seeking funding to improve the MEMS platform.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this project

Supplemental Keywords:

water monitoring, halogenated hydrocarbon, THM, HAA, MEMS, electrochemical sensor


SBIR Phase I:

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