Proof-of-concept for chemiresistive water quality sensors: free chlorine in drinking water; ammonia in wastewater

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Water is essential to our life. We take water from the environment, consume it for various purposes, and discharge it back into the environment. Maintaining water quality at all times is very important. Our drinking water, for example, needs to be kept free from pathogens throughout the distribution system by maintaining residual disinfectant levels. Free chlorine is a common disinfectant used for that purpose because it is effective at killing pathogens, even though it is not very stable and can easily deplete during drinking water distribution. This is why continuous online monitoring is desirable at multiple points along the distribution system. Monitoring of wastewater during its discharge into the environment is similarly important. While it is not destined for immediate human consumption, it can severely impact the ecosystem at the discharge site, or downstream of it. In most cases, wastewater will eventually pass by the intake sites of other drinking water systems. The nitrogen content of wastewater, in especially in the form of aqueous ammonia, is of particular concern. Thus, ammonium sensors are commonly deployed at wastewater plants. Both free chlorine and ammonia sensors are being manufactured and distributed by our industrial partner ABB as part of the Aztec and Navigator series of continuous water analyzers. These devices mainly rely on colorimetric and electrochemical sensors. While ABB has succeeded in reducing the reagent consumption of their colorimetric sensors, they nevertheless require periodic maintenance for refills. Electrochemical sensors are typically reagentless, but nevertheless limited by the durability of their reference electrodes. This proposal aims to develop McMaster's chemiresistive technology for use in ABB's online analyzers.