Survey of 218 organic contaminants in groundwater derived from the world's largest untreated wastewater irrigation system: Mezquital Valley, Mexico

Abstract

The Mezquital Valley system is the world's oldest and largest example with regard to use of untreated wastewater for agricultural irrigation. Because of the artificial high recharge associated with the Mezquital Valley aquifers, groundwater is extracted for human consumption, and there are plans to use this groundwater as a water resource for Mexico City. Thus, this study analyzed 218 organic micro-contaminants in wastewater, springs, and groundwater from Mezquital Valley. Five volatile organic compounds (VOCs) and nine semi-volatile organic compounds (SVOCs) were detected in the wastewater used for irrigation. Only two SVOCs [bis-2-(ethylhexyl) phthalate and dibutyl phthalate] were detected in all the wastewater canals and groundwater sources, whereas no VOCs were detected in groundwater and springs. Of the 118 pharmaceutically active compounds (PhACs) and 7 reproductive hormones measured, 65 PhACs and 3 hormones were detected in the wastewater. Of these, metformin, caffeine, and acetaminophen account for almost sixty percent of the total PhACs in wastewater. Nevertheless, 23 PhACs were detected in groundwater sources, where the majority of these compounds have low detection frequencies. The PhACs sulfamethoxazole, N,N-diethyl-meta-toluamide, carbamazepine, and benzoylecgonine (primary cocaine metabolite) were frequently detected in groundwater, suggesting that although the soils act as a filter adsorbing and degrading the majority of the organic pollutant content in wastewater, these PhACs still reach the aquifer. Therefore, the presence of these PhACs, together with the high levels of the endocrine disruptor bis-2-(ethylhexyl) phthalate, indicate that water sources derived from the recharge of the studied aquifers may pose a risk to consumer health.

Identification of Aquifer Recharge Sources as the Origin of Emerging Contaminants in Intensive Agricultural Areas. La Plana de Castellón, Spain

“…These characteristics surely allowed the compound to be detected in the GW samples. On the other hand, although acetaminophen was detected in this case, [80] showed that acetaminophen was degraded and not detected in GW, but they did not specify the soil types. In 2002, [81] pointed out that both primidone and carbamazepine were particularly useful for GW studies because both were detected.…”

Identification of the Hydrogeochemical Processes and Assessment of Groundwater Quality, Using Multivariate Statistical Approaches and Water Quality Index in a Wastewater Irrigated Region

“…The wastewater recharge rate in the study area is approximately 25 m 3 /s, and corresponds to 13.3 times the natural recharge rate in the Mezquital Valley [12]. The accelerated recharge rate facilitates the transport of persistent pollutants to the unconfined aquifer, and results in a deleterious impact on groundwater quality [13]. Previous studies have reported the pollution of groundwater related to high levels of NO 3…”

Presence and Natural Treatment of Organic Micropollutants and their Risks after 100 Years of Incidental Water Reuse in Agricultural Irrigation

“…The raw wastewater that is sent from Mexico City (through the "Emisor Central") is used for agricultural irrigation in Tula Valley, and presents traces (ng/L) of at least 18 OMPs. Overall, in spite of the occurrence of some hard to degrade compounds in the groundwater of the Mezquital Valley aquifers, soil layers with a high content of organic matter and clays seem to act as filter and buffer systems for almost all of these compounds, which prevent contamination of the aquifer [18,28,43]. In addition, carbamazepine was regularly recorded, which suggests the possible presence of other polar and persistent organic micro-pollutants.…”

“…Conversely, few works have evaluated the content of these organic contaminants in wastewater and groundwater in the same area. Those that did measured very few compounds [18]. They tended only to assess the occurrence and fate of semi-volatile organic compounds, pharmaceutically active compounds, and other emerging contaminants in the Tula Valley and focused on their accumulation and dissipation, or their sorption/desorption from soils [18].…”