Desarrollo de métodos de análisis y control de subproductos de desinfección en aguas de abastecimiento público

Abstract

Disinfection byproducts (DBPs) are toxic compounds formed during disinfection of drinking water by reaction of chlorine with precursor organic substances. Among the nearly 800 known DBPs, trihalomethanes (THMs) and haloacetic acids are the most studied for their toxic evidence, being regulated by international health regulations. The rest, cailed unregulated or emerging DBPs, are present in drinking water at very low concentrations but with marked toxicity. Considering the possible toxic effects of DBPs on the health of consumers, effective analytical methods with low detection limits are necessary to allow their identification in drinking water, as well as to deep insight into the knowledge of the training mechanisms and the study of the treatment processes for its control and minimization in the waters of consumption. The objectives of the thesis were: 1) The real-scale study of the factors involved in the formation of THMs in drinking water during the treatment processes and their evolution along the distribution systems, as well as the development of predictive models for their control and minimization. 2) The development of new analytical methods for the simultaneous determination of regulated and emerging disinfection by-products in drinking water. The real-scale study showed a marked seasonal and spatial variation of THM concentrations in the water of the distribution systems essayed, being clearly dependent on the treatment process applied. The advanced treatment process, with ozonation and filtration/adsorption with granular activated carbon, was the most effective and stable, obtaining the lowest values of THMs as well as the lower ranges of seasonal and spatial variation. It was verified that an efficient oxidation process in ETAP contributes to reduce the values of THMs, thus reducing the effect of the seasonal and spatial variation, obtaining a greater stability of the quality of the supply water. A predictive model of trihalomethanes formation was developed in two stages (ETAP and Distribution System), obtaining good predictive capacity and good adaptability to different treatment scenarios. The adaptability of the model developed to the contour conditions allows its use in the quality control of drinking water, and can be a useful tool for the control of the processes, allowing to proceed in advance avoiding incidences related to of THMs concentration peaks in waters supplies. Two methods were developed for the analysis of a total of 24 DBPs in potable water (20 emerging DBPs: 6 iodine trihalomethanes, 6 haloacetonitriles, 6 halonitromethanes and 2 haloketones). The new methods were based on hollow fiber liquid phase microextraction (HF LPME), detection and quantification of analytes by GC pECD and verification by GC MS. For the improvement of microextraction with hollow fiber, techniques were incorporated as the effervescence or the spiral fiber arrangement by means of support device specifically designed and constructed by 3D printing. The two methods obtained present good linearity, repeatability and recovery, achieving very low limits of detection, being applied in the analysis of drinking water of the supply systems from Huelva zone.