Veschetti, Cittadini, Maresca, Ottaviani
Sustainability & Regulation Approval # 2004 Milan
Water distribution systems may be subjected to microbial contamination when new pipes are laid or repair work is done. Severe pollution of drinking water is also possible in plumbing systems during normal operating conditions as a consequence of unfortunate circumstances. In both cases, after removing the possible cause of contamination, it is necessary to disinfect with high levels of biocides to prevent the risk of pathogen proliferations. Chlorine is the most commonly used oxidant, but more recently, for safety and environmental reasons, there has been a general tendency towards the use of hydrogen peroxide in tank treatment. The disinfection can affect the surface properties of materials and, in consequence, determine the potential migration of undesirable substances in drinking water. To avoid the occurrence of such effects and the risk of water quality alteration, it is essential to carry out a simulation of the disinfection practice before using new materials as construction products in contact with drinking waters. At the moment only few data are available from national and international literature on the behaviour of plastic materials after repeated exposure to high levels of biocides. In this work samples of two different organic materials (high density polyethylene PE80 and EPDM rubber) and of cementitious with organic additives (acrylic polymer) were tested according to draft methods, prEN or EN standards such as prEN12873/1, CEN/TC164/WG3/N452 and prEN1420/1. A range of chlorine and hydrogen peroxide concentrations (0, 10 and 50 mg/L free Cl2; 0 and 300 mg/L H2O2) and contact times (6 and 24 hours) were investigated. After the disinfection procedure each material was submitted to three successive migration periods of 72 hours in test water without disinfectant. Organoleptic assessment of migration waters was carried out on the basis of EN1622 and evaluated taking into account the results of chemical analyses (THM, AOX, TOC and GC-MS scan).