This Small Business Innovation Research (SBIR) Phase I project seeks to demonstrate the feasibility of a system that allows for rapid detection and measurement of the concentration of metal ions in water with a view towards application of this system to monitoring water being released into environmental waters by industrial companies. Companies discharging water into the environment maintain wastewater treatment facilities, which frequently use chemicals to remove pollutants from wastewater. Controlling the efficiency of the treatment process requires real-time monitoring of the treated water. The proposed system will be capable of providing this capability, which will allow for optimum use of treatment chemicals ? currently treatment chemicals are used in excess to account for potentially large concentration changes of the target pollutant to be removed. Thus, a real-time sensor system reduces both environmental impact and cost of treatment. The technology employs optical fibers, which are chemically modified with sensor molecules whose luminescence properties change in the presence of the target pollutant. The broader/commercial impacts of this research are that this technology for real-time monitoring is not only capable of meeting a critical need for real-time wastewater-treatment process control, but can potentially address a range of monitoring tasks requiring a robust, portable, and field-deployable measurement system while offering significant cost advantages compared to existing laboratory-based systems. Thus, the impact of this project is beyond the initially targeted application to environmental monitoring in general, exploiting the capability of the technology to accommodate sensors for a variety of pollutants.
The primary goal of this project is to develop and commercialize a fiber optic-based sensor instrument for measuring heavy metal contaminants in water. The system uses one or more fluorescent sensor dyes that exhibit an optical response upon exposure to the target contaminant(s). The sensor dye molecules are incorporated into a replacement coating placed on the fiber core so that optical coupling occurs between the sensor molecules and the optical fibers. Sensor arrays can be created to measure a single contaminant over a specified area or to measure multiple contaminants simultaneously, like mercury, cadmium, lead, and nickel, with the appropriate sensor dyes. Similarly, sensor arrays can also be configured with different sensor dyes to measure nonmetallic chemical species, like dissolved oxygen and pH. Commercial applications of this fiber sensor technology include compliance monitoring, process control, and reducing operating costs and supplies in industrial settings. Currently, industrial treatment systems use intermittent and lengthy lab analysis to quantify metallic species present in wastewater. This technology has the advantage of providing comparable measurements in real time. For example, the sensor array platform can be used to monitor industrial wastewater discharged into municipal sewers or surface waters to ensure regulatory compliance, avoid costly fines, and prevent environmental contamination. Furthermore, this technology can be used to monitor wastewater prior to treatment in order to optimize the treatment process and chemical dosing. Consequently, the sensor array platform can improve efficiency, reduce treatment costs, and benefit the environment. In this work, the feasibility of the fiber sensor technology was demonstrated with a zinc sensor immobilized in a polymer. This polymer material is made porous to aid transport of the target contaminant to the sensor molecules. The fiber sensor exhibited a reversible and rapid, one-minute response upon exposure to a solution containing dissolved zinc; the nonporous sensor displayed a 3 hour response time. Also, the sensor was able to accurately measure zinc concentrations over a range of 0.04 to 1.25 ppm. These results were verified by a conventional laboratory instrument and by an independent, outside laboratory. In addition, the immobilized zinc sensor provided a stable response for ninety days. Finally, the response of zinc fiber sensor depended on both temperature and pH, which will require compensation for field measurements.
