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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Water Management and Conservation Research » Research » Research Project #441621

Research Project: Increased Water Security through Safe Reuse of Reclaimed Water

Location: Water Management and Conservation Research

2022 Annual Report

The long-term objective of this project is to provide science-based data to ensure that treated municipal wastewater used for irrigation poses minimal threat to people and the environment. Specifically, during the next five years the project will focus on the following objectives. Objective 1: Determine the processes that govern the environmental fate and transport of emerging contaminants and other constituents found in treated wastewater used for irrigation to provide a research basis for potential regulation of these constituents. Sub-objective 1.A: Determine the effect of temperature on the sorption, fate, and transport of pharmaceuticals in soil. Sub-objective 1.B: Determine the effects of long-term wastewater irrigation on soil contaminant concentration and the soil microbiome. Sub-objective 1.C: Optimize removal of pharmaceuticals from water. Objective 2: Develop and optimize low input treatment systems to reduce emerging contaminants and nutrients found in degraded waters to increase water resources used for food production.

Objective 1 will seek to Increase water supplies available for irrigation and managed aquifer recharge through safely reusing treated wastewater. The effect of temperature and season on the environmental fate and transport of contaminants of emerging concern (CEC) found in reclaimed wastewater will be characterized and quantified. Ten different pharmaceuticals that have a range of pKa’s from (4.0 – 16.0) will be evaluated in the lab by batch sorption and column flow through experiments using soils from the Southwest US. Experiments will be conducted at 10° C, 25° C, and 40° C. Pharmaceutical mobility will be evaluated and compared to seasonal soil temperatures to determine seasonal variability in soil transport. A set of paired stormwater recharge basins, one that receives wastewater inputs and one that does not, will be sampled for pharmaceutical analysis. Results from lab experiments and the paired basins will be used to model the potential for stormwater retention basins to contaminate groundwater with pharmaceuticals found in the wastewater used for irrigation. These results will be used to provide management guidance for stormwater retention basins. Finally, biochar pyrolyzed from walnut shells and cotton gin waste will be evaluated as a treatment method for removing pharmaceuticals from wastewater. Biochar pretreatments will include untreated, acid treated, and base treated prior to pyrolysis. Lab scale columns will be constructed and water containing pharmaceuticals will be passed through biochar filter columns. Removal efficiency and capacity will be calculated, and sorption mechanisms elucidated. Objective 2 Will be a modeling exercise to determine the potential for using reclaimed wastewater as a supplemental irrigation source in rainfed agricultural systems. The volume of produced wastewater in regions of the Midwest will be spatially matched to potential crop needs. Crop irrigation needs will be modeled using historical weather data and then spatially matched to wastewater availability. Results will be used to determine potential yield loss related to reduced rainfall due to short term spatial and temporal drought. Yield recovery will be related to available water and distance water needs to be transported.

Progress Report
This report documents progress for project 2020-13000-005-000D, Increased Water Security through Safe Reuse of Reclaimed Water, which started in January 2022 and continues research from project 2020-13000-004-000D, The Use of Treated Municipal Waste Water as a Source of New Water for Irrigation. In support of Sub-objective 1A, a series of pharmaceutical sorption experiments were conducted at various temperatures. It was found that increasing temperature resulted in decreased pharmaceutical sorption. The decrease in sorption indicates that pharmaceutical mobility through soil will increase with increasing temperature. In support of Sub-objective 1C, biochars produced from cotton gyn waste and walnut shells have been evaluated and for removal of pharmaceuticals from water. A series of experiments were conducted to determine the effect of treatment prior to pyrolysis and after pyrolysis on sorption potential. It was found the pretreatment of pyrolysis feedstock with acid and base prior to pyrolysis resulted in a five times increase of surface area. In addition, it was found that a 24-hour water rinse of biochar’s after pyrolysis resulted in increased surface area of more than ten times. Results are being used to optimize removal of pharmaceuticals from water in low input flow through systems. In support of Objective 2, contact has been made with researchers at Arizona State University to gain access to a database compiled for the American Water Works Association that collected flow data and water quality data for all permitted wastewater treatment facilities in the United States. Water data will be used as input for a modeling exercise to determine the potential to supplement ET needs during spatial and temporal events that cause water stress in crops.

1. Simultaneous extraction of four antibiotic compounds from soil and water matrices. Antibiotic resistance is a growing health concern. Analyzing the presence of antibiotic compounds in the environment is critical for determining the drivers for development of antibiotic resistance. Methods were developed by ARS researchers in Maricopa, Arizona, to simultaneously analyze four antibiotics important in human medicine (sulfamethoxazole, trimethoprim, lincomycin, and ofloxacin) in environmental matrices. Based on this research, matrix characteristics, especially pH, as well as the pKa’s and functional groups of the antibiotics results in the need to select the appropriate extraction methods when attempting to extract antibiotic compounds from a water or soil matrix. These newly developed methods will be useful for researchers and regulators to quantify antibiotics from environmental samples.