1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
This is a new project that started in January 2017 and continues research from 2020-13000-003-00D, “Reuse of Treated Municipal Waste Water for Irrigation as a Means to Increase Alternative Water Supplies”. Please see the report for the previous project for additional information. Under Objective 1, quarterly sampling of the Neely wastewater treatment plant in Arizona was begun. High intensity sampling over a week was conducted in the spring and summer, two additional sampling events in the fall and winter will be carried out. Samples are being analyzed for pharmaceuticals and potential endocrine disruptors. Under Objective 2, biochar has been produced using guayule and cotton gin waste at different temperatures. Biochars are being evaluated as sorbents to remove pharmaceuticals at sub part per million levels from water. Removal rates are being measured using traditional batch sorption techniques. Promising biochar’s will be further evaluated as filter media for irrigation systems delivering reclaimed wastewater.
Yang, Y., Toor, G., Wilson, P., Williams, C.F. 2017. Do septic systems contribute micropollutants and their transformation products to shallow groundwater? Environmental Science and Technology. 123:258-267.