Thin film based disc microelectrode arrays in water toxicity control

Resumen

The importance of good drinking water quality has generated great demand for cheap, simple and fast methods to control water toxicity, In order for a water to be suitable for human consumption, it must fulfil certain criteria such as the absence of: (i) microorganisms, (ii) substances that can alter its organoleptic properties and (iii) toxic substances such as heavy metals and certain ions. This thesis is about measuring some of these parameters using electrochemical techniques and microfabricated transducers. One of the simplest ways to ensure the absence of microorganisms in water is to keep a controlled residual level of disinfectant. This is in most of the cases hypochlorous acid / hypochlorite, which causes microbial death. However, the use of strong oxidising agents as disinfectants does not suffice to mitigate or remove the effect of other toxic compounds, like mercury or bromate, which persist in the medium. Occasionally, the carcinogenic character of certain compounds, demands for highly sensitive methods of detection. The first chapters of this thesis show the viability of using micro-electrodes to monitor free chlorine in tap water within safety levels. Then, improvements on current electrochemical methods used for mercury and bromate are presented which aim at lowering detection limits and simplifying methodology using microelectrode arrays. Finally, a novel method to determine acute toxicity in water supply lines using a biofilm based micro-respirometer array is discussed. The work is completed with a comprehensive review on the use of microelectrode arrays in electroanalysis and a description of the 2-D simulation method used to characterize and model the behaviour of microfabricated microelectrode arrays.