Contamination of groundwater by pathogenic bacteria, protozoa, and viruses of fecal origin has been associated with waterborne disease outbreaks across various hydrogeological environments worldwide. Significantly, the extent of such microbiological contamination and transport of waterborne pathogens in aquifers is still not well understood (Bradford & Harvey, 2017;Cronin & Pedley, 2002). Generally, groundwater is considered to be less vulnerable than surface water to microbial pathogenic contamination from fecal matter, however, polluted groundwater is still responsible for a disproportionate fraction of reported waterborne disease outbreaks, particularly in developing countries and rural regions (Bradford & Harvey, 2017;Buckerfield et al., 2019;Jin & Flury, 2002; WHO & UNICEF, 2014). Furthermore, this problem is shared in developed countries such as the United States where between 750,000 and 6 million illnesses per year have been attributed to contaminated groundwater (Macler & Merkle, 2000;Reynolds et al., 2008). Serious cases of pathogenic bacterial contamination of aquifers have been reported following episodic heavy rain events, a notable example occurring at Walkerton (Ontario, Canada) in May 2000, where the rapid transport of pathogenic contaminants through a highly fractured carbonate aquifer system to water supply wells resulted in 2,300 illnesses and 7 deaths (O' Connor, 2002;Worthington & Smart, 2017). Many incidences of waterborne diseases can be associated with contamination of surface water and groundwater due to failing on-site domestic wastewater treatment systems (DWTSs), spreading of agricultural fecal matter (i.e., manure) and other farming activities in rural and less urbanized areas (Fetter, 2001;WHO, 2003). Despite a decrease in recent decades in waterborne disease outbreak risks related to municipal water supply sources, no corresponding decrease in disease outbreak risks for untreated or inadequately treated groundwater has been observed on the basis of outbreak reports (Craun, 2012). Hence, microbial pathogenic contamination of aquifers remains an ongoing, globally important, water quality problem (Ashbolt, 2004;Nguyen et al., 2016). Moreover, as a result of increasing numbers of point and nonpoint sources of fecal pollution in catchments (Barrett et al., 1999;Cronin & Pedley, 2002;Misstear et al., 1996), population growth, extreme weather events associated with climate change, and rapid land-use alterations, it should be expected that such water quality problems will be exacerbated in the
<p>Karst aquifers are exceptionally vulnerable to pollution and may be impacted by multiple contamination sources. In rural and suburban areas, human wastewater effluent from on-site domestic wastewater treatment systems (DWTSs) and agricultural sources are the most significant threats to groundwater quality. It has been estimated that around 2.8 billion people worldwide rely on DWTSs for treating domestic wastewater. As karst groundwater is a major source of drinking water for at least one-quarter of the world&#8217;s population it makes protection and management of karst aquifers extremely important. These aquifer systems are highly complex and challenging to understand, especially with regards to the fate and transport of contaminants through such systems. Thus, significant knowledge gaps exist with respect to linking contaminants with the origins of pollution and quantifying different pollution impacts on groundwater quality in karst environments.</p> <p>In this paper, a novel approach for investigation of the impact of contaminants from DWTS effluent on rural karstified aquifers using a range of source-specific tracers is proposed, as it is extremely difficult to distinguish between agricultural and DWTS effluent pollution using only traditional water quality parameters or any single environmental marker. Domestic wastewater is primarily discharged from toilets, washing machines, showers and dishwashers, but even after on-site wastewater treatment processes a large number of different contaminants, including source-specific ones, can still reach the groundwater and wider environment. One example are microplastic particles which are found with other solid materials in the wastewater effluent principally due to household washing and cleaning processes. Investigations of microplastic occurrences in groundwater systems are very rare but several karst springs in the west of Ireland have been sampled during this study for quantification and identification of microplastic particles using Fourier-transform infrared spectroscopy (FTIR). Many of these particles were successfully linked to human wastewater on the basis of their physical and chemical properties and/or adsorbed/absorbed pollutants. The overall numbers of microplastics and numbers of household-derived microplastic particles were linked to other well-known indicators of human contamination such as fluorescent whitening compounds (FWCs) and specific anion ratio signatures (Cl:Br). Our results show a significant correlation between microplastics and detected FWC signals at different karst springs over time, which suggests the majority of found microplastic particles to be from DWTS effluent. Notably, certain limitations were found and furthermore understood in terms of the capability of Cl:Br ratio method in determining human wastewater impacts on karst groundwater. Additionally, we have found that faecal sterol and stanol concentrations, as source-specific faecal markers, and their ratios can very successfully differentiate and quantify DWTS effluent pollution and agricultural faecal contamination at karst springs due to rapid and extensive transport of these contaminants particularly through the karst conduit networks.&#160;</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.