Location: Water Management and Conservation Research
2018 Annual Report
Objectives
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.
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.
Approach
Objective 1 is a combination of monitoring of treated wastewater effluent for emerging contaminants (ECs) and research to investigate the potential for organic sorbents to sequester emerging contaminants in the environment. The mass of pharmaceuticals taken up by crops irrigated with treated municipal wastewater depends on the concentration of the pharmaceutical at the soil-root interface and the volume of water needed to meet plant metabolic needs. The concentration of pharmaceuticals at the root is determined by initial concentration applied and soil processes that remove the pharmaceutical from the soil solution.
Evaluating Temporal Patterns of ECs: Pharmaceutical concentration in sewage effluent will be measured on three different time scales from five different regions of the country (arid, semi-arid, humid continental, humid sub-tropical, tropical) to characterize the concentration of ECs found in reclaimed water. One sewage treatment plant from each region will be chosen for sampling. Treatment plants of similar size with similar treatment trains will be selected and sampling will consist of four high intensity sample periods lasting one week each in winter, spring, summer, and fall. Samples will be time averaged composite samples with equal aliquots collected every 30 minutes.
Evaluating the potential for organic residues to remove carbamazepine from irrigation water: Previous research has shown that organic materials can act as sorbents to remove trace organics, however, most of this research is limited to pesticides and industrial pollutants. The sequestration of these compounds by organics has typically been measured on systems where the contaminant is present at part per million levels (ppm), while ECs are typically found at part per billion (ppb) levels or less in irrigation water. It is hypothesized that sub ppm levels of ECs found in irrigation water can be effectively and economically removed from the water through the use of sorbents derived from waste products. Raw waste products to be tested will include post-harvest plant residues, biochars derived from plant residues, and organic wastes. Effective removal will be governed by overall sorbate characteristics, which include sorption kinetics, total sorption potential, and effective sorbent life span.
Objective 2 is a laboratory scale design and engineering endeavor to develop viable treatment practices to remove EC’s from irrigation water prior to plant uptake. Candidate sorbents will be evaluated for EC removal efficacy from irrigation water. It is hypothesized that through proper placement and treatment of organic plant residues the soil solution concentration of ECs can be reduced. Candidate sorbents will be evaluated in both media filters and as soil amendments concentrated where water application occurs to evaluate EC removal potential. Evaluation of field treatment options will use three different removal options: 1) Use of organic amendments as filter media; 2) Use of organic amendments to increase overall soil sorptive capacity; and, 3) Selective placement of organic amendments to intercept irrigation water prior to soil application.
Progress Report
Progress was made on both objectives, all of which fall under National Program 211, Water Availability and Watershed Management.
Objective 1: Quarterly sampling of the Neely wastewater treatment plant in Gilbert, Arizona, was completed and quarterly sampling at the State College, Pennsylvania, wastewater treatment facility began. High intensity sampling in State College, Pennsylvania, was conducted over a one-week period in summer 2018. Three additional sampling events will be conducted in fall 2018 and in winter and spring of 2019. Samples are being analyzed for pharmaceuticals and potential endocrine disruptors. Results will be used to provide input data for human health risk assessment models.
Objective 2: Biochar was produced using guayule and cotton gin waste at different temperatures. The chemical and physical characteristics of biochar that can influence sorption have been determined. Biochar is currently being evaluated for its sorbent potential to remove pharmaceuticals at sub-part per million levels from water. Removal rates and total potential removal are being measured using traditional batch sorption techniques and will be modeled to provide a predictive tool for design of removal systems. Promising biochar will be evaluated further as filter media for irrigation systems delivering reclaimed wastewater.
Accomplishments
1. Removal potential of tylosin from water using diatomaceous earth (DE). Tylosin is a widely used antibiotic fed to animals during livestock production with most of the antibiotic passing through the animal unchanged and entering the environment where it might contribute to antimicrobial resistance. ARS researchers at Maricopa, Arizona, and Clay Center, Nebraska, found that a common clay mineral, diatomaceous earth (DE), could remove tylosin from wastewater. Removal of tylosin from the wastewater was measured and two different sorption models were evaluated under different environmental conditions (e.g. temperature, type of salinity, ionic strength). One of the models was better at describing the binding and predicted that the amount of tylosin that binds to DE was dependent on the types of salts added and the temperature of the water. From previously reported data on the concentration of tylosin in beef cattle storage ponds, removal of tylosin by sorption to DE would cost $0.25 per million gallons of storage pond water. DE provides a cost-effective way to remove tylosin from wastewater produced by beef cattle operations.
2. Land application of wastewater to remove antibiotics from treated municipal wastewater. Wastewater treatment plants are not designed to completely remove pharmaceuticals from sewage and continually release low levels into the environment. Land application of wastewater may provide tertiary treatment for removal of pharmaceuticals and protect water resources. An ARS researcher at Maricopa, Arizona, in collaboration with researchers from Pennsylvania State University, State College, Pennsylvania, found that sulfamethoxazole typically had the highest concentration in the effluent followed by ofloxacin and trimethoprim. Results from a site that had previously received wastewater application but had no wastewater for 10 weeks revealed that ofloxacin was at the highest soil concentration, however, following 10 weeks of irrigation, sulfamethoxazole had the highest concentration. In addition, concentrations in ground water were typically less than detection limits. Soil can provide additional treatment of pharmaceuticals found in municipal wastewater effluent and protect water resources from antibiotic contamination.
