Towards Identifying Disinfectants and Quantifying Disinfectant Levels in Water

Abstract

Disinfectants are added to the water distribution system and swimming pools to control the growth of pathogenic microorganisms in water. High disinfectant levels are health hazards since they produce disinfectant by-products which are carcinogens. Thus, monitoring the amount ofresidual disinfectants present and maintaining an optimal amount of residual disinfectants throughout the distribution network is very crucial for safe water distribution. Colorimetric measurements are the current standard for measuring disinfectant levels in water. However, it is very difficult to integrate colorimetric measurements into automated monitoring devices. Redox active molecules like the phenyl-capped aniline tetramer (PCAT) can be incorporated as a dopant into a single wall carbon nanotube sensor for detecting oxidant in drinking water. The sensor works on the principle of oxidizing adsorbed redox molecules on carbon nanotubes by oxidant present in drinking water thus changing the resistivity of the carbon nanotube film. Most commonly used disinfectants are HOCl, Cl2, ClO2, Chloramine, KMnO4, HOBr, H2O2, O3, Br2, I2, etc. They all are oxidizing agents and can be distinguished from one another as they have different oxidation potentials. For water treatment purposes, it is not enough to know the disinfectant level, but it is also very important to identify which disinfectant is present. Currently, there is no standard method for distinguishing different disinfectants presents in water. The development of sensor arrays based on redox active molecules having different redox potentials is a potential pathway towards differentiating between different disinfectants in water. Different aniline oligomers were synthesized to create a library of redox active molecules. Redox properties of these molecules have been determined, and expected results were compared with the sensor performance. In the future, these sensors can be incorporated into a reliable, resettable and reagent free sensor array for monitoring and distinguishing different disinfectants in water. Being able to constantly monitor the disinfectant level and identifying the disinfectant present in water will enable us to design an improved and sustainable disinfecting system.