Clean Water and Sanitation (SDG 6), Climate Action (SDG 13)
Disinfection by-products in recycled wastewaters: What is in my water?
Susana Kimura Hara* University of Calgary, Canada
The sustainability of freshwater supplies is a growing concern that is being jeopardized by population growth, changing climate patterns, and increasing demands by economic activities. Our changing world is increasingly relying on alternative water sources (i.e., saline and wastewater effluents) that contain a broad range of contaminants including pathogens, ammonia, halide ions, pesticides, industrial solvents, pharmaceuticals, and consumer products. Regions that are experiencing severe water drought and scarcity are already developing and implementing technologies to augment their water resources from wastewater effluents. The reuse of wastewater effluents requires the practice of disinfection to prevent outbreaks of waterborne diseases. Chemical and ultraviolet light disinfection processes are used to effectively control microbial pathogens (and their high health risks). However, these treatment methods carry serious unintentional consequences: they react with natural and anthropogenic constituents to form disinfection by-products (DBPs) that pose a potential health problem caused by long-term exposure. Wastewater effluents are of special concern because they contain higher levels of organic nitrogen and ammonia that could lead to the formation of unregulated nitrogen-containing DBPs (i.e., haloacetamides, haloacetonitriles, halonitromethanes) that have been shown to be more toxic than currently regulated DBPs (haloacetic acids and trihalomethanes). Currently, there are no guidelines established for DBPs in wastewater-impacted waters. Nevertheless, alternative treatment technologies and schemes are being proposed with little knowledge of the safety of these waters. This is further complicated by the complexity of wastewater effluents, which may form a different suite of DBPs compared to pristine waters. The objective of this study is to determine what key aspects of the effluent organic matter (EfOM) contained in wastewater that are responsible for the formation of toxic DBPs across a wastewater reuse facility that treats secondary wastewater effluent with microfiltration, reverse osmosis, and ozone disinfection. To achieve this, three-dimensional excitation-emission matrices (EEMs) obtained with fluorescence spectroscopy is combined with Parallel Factor Analysis (PARAFAC) modeling to analyze wastewater samples. PARAFAC is used to characterize EfOM by statistically deconvolute complex EEMs into individual components. Treated wastewaters were evaluated for DBP formation potential by disinfecting samples with chlorine and chloramines and analzyed for 30 regulated and regulated DBPs. Results from a year-long study will be presented, which is the first of its kind.
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© The Author(s), 2023
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