Unveiling the role of rubber seals in the generation of decentralized disinfection by-products in chlorinated water distribution systems

Abstract

The degradation of rubber seal (RS), particularly ethylene-propylene-diene (EPDM), in the drinking water networks has been confirmed, yet the role of RS as a disinfection by-product (DBP) precursor remains unknown. This study provides explicit proof of the formation of halogenated disinfection by-products (X-DBPs) from RS in chlorinated drinking water within water supply systems. Over time, exposure to chlorinated water ages RS, releasing high levels of organic compounds, which act as DBP precursors. Trihalomethanes (THMs) and haloacetic acids (HAAs) emanating from RS recorded 12.1 μg L⁻¹ and 2.3 μg L⁻¹, respectively, after contact with chlorinated water. RS additionally revealed modest amounts (∼1.5 and 0.25–0.3 μg L⁻¹) of haloacetaldehydes (HALs) and haloacetonitriles (HANs), respectively, posing potential cytotoxic risks. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR) analyses showed remarkable morphological alterations in RS due to exposure to chlorinated water, whether in ultrapure water or real water. Moreover, the correlation analysis of 2D–COS–FT-IR exhibited the hydroxyl group (O–H) as the most sensitive functional group among other groups toward chlorine. The biofilm in the plastic pipes exposed a negligible role in the formation of X-DBPs, emphasizing the main contributions of RS and the water matrix to the formation of X-DBPs in drinking water. Our results highlight the need to consider them alongside other DBP precursors to safeguard water quality and to explore safer alternatives for sealing water pipes within the distribution system.