Implementación de un modelo predictivo para la formación de trihalometanos en sistemas de abastecimiento. Propuesta de soluciones tecnológicas y herramientas de ayuda para la gestión del riesgo sanitario

Resum

Trihalomethanes are disinfection byproducts (DBPs) formed by the reaction of chlorine derivatives in drinking water with their precursors which may be organic matter or bromide. Prolonged exposure over time to high concentrations of THMs poses a risk to human health due to its carcinogenic and mutagenic potential. For this reason, the regulation of THMs in drinking water supply systems is essential. In Spain the concentration of trihalomethanes (THMs) in drinking water is regulated since 2003 by Royal Decree 902/2018, of 20 July, amending Royal Decree 140/2003, of 7 February on health criteria for drinking water, through this legislation establishes the maximum level of THMs in water supply networks at 100 μg/l. This has led to research looking for technologically and economically viable alternatives to reduce the concentration of THMs in drinking water supply networks. In this research, a compendium of available technologies is made, and 3 of them are specifically analyzed, based on experimental data collected by companies of the water sector and its associated companies: • TRS System (Trihalomethanes Removal System) • Electroadsorption of bromides • Direct desorption with air The prediction model ESTRIHALO, developed by the companies of the water sector (Agbar) and the University of Granada, was also analyzed in detail as a preventive mechanism. This model seeks to become a tool to alert about possible increases in the concentration of THMs that reach the consumers and to allow drinking water managers to take action in advance, adjusting operating parameters in an economically viable way. This model is especially useful for smaller facilities, where the costs associated with monitoring THMs are high. The statistical analyses of the predictive models reflect percentages of reliability (R2) of up to 70% in the theory, given by the statistical program. Whereas, by including the algorithms of the models in the computer systems of the supply systems, has achieved a success rate of up to 89% when validating the real values of the concentration of THMs with those predicted by the models. The TRS System (Trihalomethanes Removal System) bases its operation on the volatility of trihalomethanes. The purpose of this technology is the direct elimination of THMs already formed by spraying water into microdroplets, favoring their diffusion into the air. With the data obtained in the pilot test and during its operation in the Castelldefels warehouse (Barcelona), the TRS system has proven to be a viable alternative to eliminate about 50% of the THM concentration. The THMs direct desorption system has been developed in the Region of Murcia to reduce the concentration of THMs by direct desorption by air. Like the TRS system, it bases its operation on the volatility of THMs already formed in the water. In this case, air is injected from the base of the tank to generate microbubbles capable of favoring the diffusion of THMs towards the surface of the tank. This technology was developed in response to the increase in the concentration of THMs in drinking water in Murcia, which have been observed in recent years. Seeks to maintain low levels of THMs throughout the supply network through the installation of automated desorption equipment in intermediate tanks. Regarding the treatment of THMs formation precursors, it has been demonstrated in laboratory experiments that electroadsorption of bromide can achieve THM elimination values of between 43% and 53%. This method is based on the enhancement of the adsorbent capacity of activated carbon filters by applying an electric field. However, it requires further research to determine whether these yields can be achieved on an industrial scale.