Organic Contaminants in Reuse Waters and Transport Following Land Application
Scientists Provide Information on the Fate and Transport of Contaminants in Reuse Waters
Potential reuse waters contained unique mixtures of organic contaminants with the greatest number detected in treated municipal wastewater treatment plant effluent, followed by urban stormwater, and agricultural runoff. This study provided information for decisions on reuse strategies to support freshwater supplies.
Water-management agencies worldwide are increasing water reuse to augment freshwater supplies for crop irrigation and to maintain instream flows. The primary types of waters reused to meet increasing water supply demands are treated municipal wastewater treatment plant effluent and urban stormwater runoff. Additionally, recycled agricultural runoff can be used in arid areas. While water reuse augments water quantity needs, there is a lack of information on the contaminants that occur in different types of reuse waters and their fate if applied to land surfaces for irrigation needs. Concerns for safe and sustainable water and food supplies necessitates a better understanding of contaminants in potential reuse waters.
The U.S. Geological Survey (USGS), U.S. Environmental Protection Agency (USEPA), Oklahoma State University, and the University of Colorado-Boulder collaborated on a study to address these knowledge gaps. Scientists carried out the study at the Oklahoma State University South Central Research Station in Chickasha, Oklahoma.
Contaminants Measured
Scientists measured contaminants in three potential reuse sources (treated municipal wastewater treatment plant (WWTP) effluent, urban stormwater, and agricultural runoff). They also sampled runoff from two corn fields with (9 acres) and without (12 acres) WWTP effluent applied through irrigation to determine if contaminants in wastewater effluent applied to crops were mobilized and transported from the field through runoff during precipitation events. Lastly, they determined if contaminants were taken into the aboveground portions of corn plants from the two fields. Water samples were analyzed for concentrations of 643 organic chemicals, 62 inorganic chemicals, and estrogenicity. Aboveground plant samples were analyzed for a subset of the target organics including pharmaceuticals and per- and polyfluoroalkyl substances (PFAS).
Contaminant Mixtures in Reuse Waters
The three reuse waters contained unique mixtures of organic chemicals including disinfection byproducts [DBP], prescription and nonprescription pharmaceuticals, industrial/household chemicals, PFAS, polycyclic aromatic hydrocarbons (PAH), and pesticides. For example, PFAS, prescription pharmaceuticals, and industrial/household use chemicals were detected more frequently in WWTP effluent than in urban stormwater or agricultural runoff. In contrast, PAHs were the most frequently detected in urban stormwater, and pesticides were the most frequently chemicals in agricultural runoff. The greatest number of organic chemicals were detected in WWTP effluent (140), followed by urban stormwater (121), and agricultural runoff (58) samples. However, for most constituents (except for DBPs), concentrations and loads of organic contaminants from urban stormwater were comparable to and often exceeded those from wastewater-effluent discharges. The results of this study were consistent with previous findings that potential reuse waters contain unique mixtures of organic chemicals that have been shown to persist in the environment.
Transport of Contaminants from Fields Irrigated with WWTP Effluent
Wastewater irrigation was not found to be a predominant source of the total contaminant load in runoff from irrigated agricultural plots. Rain induced runoff between the paired corn fields with and without WWTP effluent irrigation, documented minimal differences in dissolved contaminants (pesticides made up the greatest portion of the load from both fields). However, two chemicals (imidacloprid and estrone), were detected in the rain-induced runoff from the wastewater-irrigated corn field and were likely contributed by effluent irrigation. Future research could clarify if any contaminants in reuse waters are adsorbed to soils or the suspended-sediment portion of runoff (not included in this study) to better determine their fate following application to farmland. Two pharmaceuticals were detected in the aboveground portions of corn plants at harvest (norfloxacin and ciprofloxacin) in the fields with WWTP effluent irrigation indicating plant uptake and potential exposure for livestock that consume the plant material.
Understanding the types of chemicals present in reuse waters, potential for the transport of dissolved chemicals, and uptake into plants, provides information for resource managers as they make decisions related to reuse requirements to minimize transport to water supplies to safeguard the human and wildlife. This information is particularly important as demand for freshwater increases and the need to supplement freshwater supplies through water reuse.
This study was supported by the USGS Environmental Health Program on land applied reuse materials and was conducted in collaboration with the U.S. Environmental Protection Agency and Oklahoma State University.
Potential reuse waters contained unique mixtures of organic contaminants with the greatest number detected in treated municipal wastewater treatment plant effluent, followed by urban stormwater, and agricultural runoff. This study provided information for decisions on reuse strategies to support freshwater supplies.
Water-management agencies worldwide are increasing water reuse to augment freshwater supplies for crop irrigation and to maintain instream flows. The primary types of waters reused to meet increasing water supply demands are treated municipal wastewater treatment plant effluent and urban stormwater runoff. Additionally, recycled agricultural runoff can be used in arid areas. While water reuse augments water quantity needs, there is a lack of information on the contaminants that occur in different types of reuse waters and their fate if applied to land surfaces for irrigation needs. Concerns for safe and sustainable water and food supplies necessitates a better understanding of contaminants in potential reuse waters.
The U.S. Geological Survey (USGS), U.S. Environmental Protection Agency (USEPA), Oklahoma State University, and the University of Colorado-Boulder collaborated on a study to address these knowledge gaps. Scientists carried out the study at the Oklahoma State University South Central Research Station in Chickasha, Oklahoma.
Contaminants Measured
Scientists measured contaminants in three potential reuse sources (treated municipal wastewater treatment plant (WWTP) effluent, urban stormwater, and agricultural runoff). They also sampled runoff from two corn fields with (9 acres) and without (12 acres) WWTP effluent applied through irrigation to determine if contaminants in wastewater effluent applied to crops were mobilized and transported from the field through runoff during precipitation events. Lastly, they determined if contaminants were taken into the aboveground portions of corn plants from the two fields. Water samples were analyzed for concentrations of 643 organic chemicals, 62 inorganic chemicals, and estrogenicity. Aboveground plant samples were analyzed for a subset of the target organics including pharmaceuticals and per- and polyfluoroalkyl substances (PFAS).
Contaminant Mixtures in Reuse Waters
The three reuse waters contained unique mixtures of organic chemicals including disinfection byproducts [DBP], prescription and nonprescription pharmaceuticals, industrial/household chemicals, PFAS, polycyclic aromatic hydrocarbons (PAH), and pesticides. For example, PFAS, prescription pharmaceuticals, and industrial/household use chemicals were detected more frequently in WWTP effluent than in urban stormwater or agricultural runoff. In contrast, PAHs were the most frequently detected in urban stormwater, and pesticides were the most frequently chemicals in agricultural runoff. The greatest number of organic chemicals were detected in WWTP effluent (140), followed by urban stormwater (121), and agricultural runoff (58) samples. However, for most constituents (except for DBPs), concentrations and loads of organic contaminants from urban stormwater were comparable to and often exceeded those from wastewater-effluent discharges. The results of this study were consistent with previous findings that potential reuse waters contain unique mixtures of organic chemicals that have been shown to persist in the environment.
Transport of Contaminants from Fields Irrigated with WWTP Effluent
Wastewater irrigation was not found to be a predominant source of the total contaminant load in runoff from irrigated agricultural plots. Rain induced runoff between the paired corn fields with and without WWTP effluent irrigation, documented minimal differences in dissolved contaminants (pesticides made up the greatest portion of the load from both fields). However, two chemicals (imidacloprid and estrone), were detected in the rain-induced runoff from the wastewater-irrigated corn field and were likely contributed by effluent irrigation. Future research could clarify if any contaminants in reuse waters are adsorbed to soils or the suspended-sediment portion of runoff (not included in this study) to better determine their fate following application to farmland. Two pharmaceuticals were detected in the aboveground portions of corn plants at harvest (norfloxacin and ciprofloxacin) in the fields with WWTP effluent irrigation indicating plant uptake and potential exposure for livestock that consume the plant material.
Understanding the types of chemicals present in reuse waters, potential for the transport of dissolved chemicals, and uptake into plants, provides information for resource managers as they make decisions related to reuse requirements to minimize transport to water supplies to safeguard the human and wildlife. This information is particularly important as demand for freshwater increases and the need to supplement freshwater supplies through water reuse.
This study was supported by the USGS Environmental Health Program on land applied reuse materials and was conducted in collaboration with the U.S. Environmental Protection Agency and Oklahoma State University.