A model for predicting THM presence in networks of water supply systems

The European normative, implemented in the Spanish national legislation in 2003, reduced the acceptable maximum concentration of THMs in drinking water, from 150 to 100 μ/L. This implies that many existent facilities could not achieve this requirement. Generally speaking, the problems related to THMs in the area studied occur in certain periods during the year, mainly in summer. The present concentration of trihalomethanes (THM) in networks samples of water supply systems was predicted based on a set of easy parameters measured continuously at the site, which evidently did not include THM concentration. Consequently, when these values started being high, it was possible to take necessary measures (e.g. to modify the water source, reduce chlorination, etc.) to prevent higher values which are not permitted by law. The analysis of disinfection by-products is expensive and to develop a simple tool that will allow measuring the concentrations of trihalomethanes, particularly in small, poorly resourced water supplies is therefore a worthy intention. Other studied aspects have been the season of sampling or the sampling point. Data of drinking water supply systems coming from four regions in Spain have been used. In total 893 complete analyses have been managed. For obtaining the model, a statistical analysis of multiple regression and diverse Anova tests have been carried out.