Final Report: Optical Sensor for Monitoring of Groundwater Trichloroethylene Levels

EPA Contract Number: EPD11066
Title: Optical Sensor for Monitoring of Groundwater Trichloroethylene Levels
Investigators: Beshay, Manal H.
Small Business: Intelligent Optical Systems Inc.
EPA Contact: Manager, SBIR Program
Phase: II
Project Period: May 1, 2011 through April 30, 2013
Project Amount: $224,996
RFA: Small Business Innovation Research (SBIR) - Phase II (2011) Recipients Lists
Research Category: SBIR - Waste , Small Business Innovation Research (SBIR)

Description:

Advanced sensing technologies are needed to more efficiently address the requirements for the long- and short-term monitoring of groundwater, specifically for chlorinated hydrocarbons such as trichloroethylene (also known as trichlorethene, and abbreviated as TCE).
 
To date, high-sensitivity TCE detection levels could only be achieved through water sampling followed by laboratory analysis with state-of-the-art instrumentation (e.g., gas chromatography-mass spectrometry [GC-MS] and x-ray fluorescence [XRF]). Laboratory-quality analysis in the field has required mobile GC-MS units on a trailer or in the back of a vehicle, so that obtaining reliable measurements in multiple locations has not been cost-efficient. Portable GC and XRF units are available for field use at relatively high unit cost, and trained personnel are still required. Test kits also can be used in the field, but they have limited sensitivity and require multiple-step preparation, calibration, and readings, which makes their use in multiple locations slow. Also, these current monitoring technologies are expensive. Small, rugged, reasonably priced sensors that meet the required pollutant detection levels are needed; moreover, the sensor also should be handheld and meet specific end-user needs for shorter analysis times, good reproducibility, and ease-of-use.
 
Intelligent Optical Systems (IOS) has developed an optical sensor to monitor groundwater TCE levels based on the optical detection of the reaction byproducts formed by the catalyzed degradation of chlorinated hydrocarbon species in water samples. IOS has developed that concept into a test platform consisting of a premeasured reactive catalyst packaged in the water sampling port. When the groundwater is sampled, the chlorinated hydrocarbons in the sample interact with the catalyst and produce degradation byproducts, which are then detected by optical measurements with chromogenic indicators.
 
The required target sensitivity is 10 ppb or lower; IOS achieved sensitivity levels of 1 ppm, suggesting that this technology is suitable as a monitoring tool for hot-spot contaminated sites.
 
The optical sensing platform developed by IOS has several advantages for field monitoring, particularly in "hot spots" where contamination is known to exist, and levels need to be monitored frequently with a flux of samples. The premeasured catalyst is packaged directly in the sampling port, eliminating the need for additional measurement steps. The byproduct chromogenic indicator is predried on the microwell readout platform for high-throughput testing of multiple samples. The microwell reader is available in handheld prototypes such as ESE-Qaigen devices. The test platform also can be used in a network for large area monitoring, with wireless communication sending data collected from tested field sites to a mapping network.
 
Market data indicate a wide need for a portable detector of chlorinated hydrocarbons in water samples, indicating that the IOS sensing platform will be competitive in the field of chlorinated hydrocarbon detection. According to a 2003 source, prices for current portable units such as portable GC-MS range from $17,000 to $50,000.* A 2011 source puts a portable unit of this type in the $10,000 to $14,000 range, inclusive of all setup equipment for field testing. In 2010, a potential market size for analytical instrumentation for low-end, on-site water testing was estimated to be ~$150M in the United States, and the world market was estimated to be $350M. IOS will continue its marketing efforts for this technology by demonstrating the technology IOS has developed to interested partners such as Hach, and at technical exhibitions such as SBIR national conferences.

Summary/Accomplishments (Outputs/Outcomes):

IOS has developed a field-deployable chlorinated hydrocarbon sensor platform, identifying a mechanism for the catalytic reduction of chlorinated hydrocarbons in aqueous solutions at room temperature, making use of zero valent iron nanoparticles (ZVINPs). These nanoparticles have the ultimate reactivity to chlorinated hydrocarbon reduction and have shown that measurement of this reaction's byproducts by colorimetric/fluorometric means is a valid approach to reliable chlorinated hydrocarbon sensing.
 
The reaction parameters, including reaction time, catalyst ratio, indicator levels, and reaction temperature, were optimized. Although most catalytic reactions require elevated temperatures, the reaction conditions were optimized without heating, under ambient conditions, making them suitable for field use. The premeasured catalyst is packaged directly in the sampling port, eliminating the need for additional measurement steps. The byproduct chromogenic indicator is predried on the microwell readout platform, enabling the device to perform high-throughput testing of multiple samples. The microwell reader is available in handheld prototypes such as ESE-Qaigen devices. Laboratory testing resulted in detection of TCE at 1 ppm, which meets the required sensitivity for hot-spot contamination site monitoring.

Conclusions:

Simple, reliable and cost-effective field testing of chlorinated hydrocarbons in groundwater is feasible with the sensing platform developed by IOS. The platform consists of premeasured aliquots of a catalytic reagent packaged directly in the sampling port. Upon sampling, the reagent reacts with the chlorinated hydrocarbons present in the groundwater sample to produce degradation byproducts, which are then detected by optical measurements with chromogenic indicators immobilized on a microwell readout platform. The microwell reader is available in handheld prototypes such as ESE-Qaigen devices.

References:

* "GC to Go," American Chemical Society, pubs.acs.org/subscribe/archive/tcaw/12/i03/pdf/303harris.pdf, 2003 (accessed July 6, 2011).
 

Supplemental Keywords:

field analyzer, chlorinated hydrocarbon, water monitoring, waste water, optical detection


SBIR Phase I:

Distributed Optical Fiber Sensor for Long-term Monitoring of Groundwater Trichloroethylene Levels