Stormwater runoff contains a wide range of pollutants originating from urban runoff, such as nutrients, brake- and tire-wear particles, organic compounds, and heavy metals. Nowadays, with increasing population growth, climate change, and urbanization, it is inevitable for drinking water utilities to rely on impaired and alternative water sources to meet the growing water supply needs. In this sense, stormwater runoff can be considered as an alternative to traditional potable surface and groundwater supplies. However, when the stormwater is planned to be used as an alternative source for potable use, one of the main concerns is the formation of both regulated (trihalomethanes [THMs], haloaceticacids [HAAs]) and unregulated disinfection by-products (DBPs) (Nitrosodimethylamine [NDMA], haloacetonitriles [HANs], etc.) upon disinfection. Based on the chemicals and additives used during their manufacturing process, particles from the wear of brake pads may contribute to DBP precursors present in stormwater. In general, brake pads are composed of three main formulations (metallic, semi-metallic, organic) and six main components (fibers, fillers, metals, abrasives, binders, and metal sulfides). In addition, they have been reported to contain several organic compounds, including long-chain acids, alkyl and aromatic amines and amides, other carbonaceous and nitrogenous compounds, and phenols. Overall, these compounds can be released into the air and ground during the automobile braking action and introduced into stormwater runoff following rain events. To date, extensive research has been conducted on the toxicity and water quality impacts resulting from particles released from brake pads. However, their impacts on the formation of regulated and unregulated DBPs is lacking. Therefore, the main goal of this research was to evaluate the impact of particles from brake pads on surface runoff water quality, in regards to the formation of THMs, HAAs, nitrosamines, HANs, and total organic halides (TOX) under varying drinking water oxidation strategies. The results indicated that six brake pads (two of each semi-metallic, organic, and ceramic) evaluated can potentially leach precursors (formation potential [FP]) between 85-853 ug/L, 106-2653 ug/L, 50-1000 ng/L, 4-53 ug/L, and 1743-13701 ug/L of THMs, HAAs, NDMA, HANs, and TOX, respectively. The formation of these DBPs under uniform formation condition (UFC) will be also discussed during the meeting.

Automobile brake pads: A source of DBP precursors in stormwater runoff

ACS Fall 2021

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