Location: Water Management and Conservation Research
2020 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
In support of Objective 1, researchers at Maricopa, Arizona, completed sampling for pharmaceuticals at a wastewater treatment plant in Pennsylvania. A total of 110 composite samples were collected over 4 weeks (1 each in winter, spring, summer, and fall) and have been analyzed for 120 pharmaceuticals, endocrine disrupting compounds and personal care products. In addition to outlet sampling in Pennsylvania a tracer experiment was conducted along with sampling the inlet stream. This data will be used to provide a retention time model for the treatment plant based on inlet flow rate. This model will be used to provide critical treatment efficiency data that can be used to refine treatment process to maximize removal of trace organic contaminants.
In support of Objective 2 a series of experiments were completed to evaluate the potential for biochar to remove pharmaceuticals at low concentration from water. Using batch sorption and flow through experiments three pharmaceuticals with different chemical properties were evaluated based on the ability for different biochars to remove them from water. Results indicate that the removal efficiency is dependent on the type of biochar, the pH of the system and the pKa of the pharmaceutical. Overall, the best removal occurred with cotton gin waste biochar produced at 700 C for compounds that were not charged at the pH of the system.
Accomplishments
1. Modeling carbamazepine transport in wastewater-irrigated soil under different land uses. The reuse of sewage effluent for irrigation is an effective way to dispose of treated wastewater while protecting surface waters from contamination. Carbamazepine is a persistent anti-epileptic drug found in wastewater effluent. ARS researchers in Maricopa, Arizona, in collaboration with scientists from the University of Zagreb and Penn State University found that movement of carbamazepine in surface soils is related to organic carbon content, that models overestimated the observed mobility and that augmenting soil organic matter content could be used to limit carbamazepine mobility. Results will be used to better predict carbamazepine mobility and protect the environment where treated wastewater is used for irrigation.
2. Approaches for identifying stakeholder groups in natural resource management. Stakeholder analysis, including social network analysis, has long been recognized as an essential part of natural resource management and research. Both qualitative and quantitative methods have been used to determine social networks. ARS researchers in Maricopa, Arizona, in collaboration with Penn State University, University of Nebraska, and Arizona State University assessed the efficiency of quantitative and qualitative social network approaches. Results showed that in cost-constrained projects where a choice must be made between qualitative and quantitative approaches to social network-based stakeholder analysis, the qualitative approach is the more cost-efficient route for identifying stakeholder groups. Results are being used by cooperative extension to improve production and delivery of research results to stakeholders in the United States.
3. Adsorption of pharmaceuticals from aqueous solutions using biochar derived from cotton gin waste and guayule bagasse. Current treatment processes in wastewater treatment plants are not designed to remove pharmaceuticals that are present, leading to concern when using treated wastewater for irrigation. Biochar produced from organic waste material can be a cost effective sorbant to remove pharmaceuticals from water. ARS researchers in Maricopa, Arizona, in cooperation with scientists at Penn State University, evaluated biochar produced from cotton gin waste and guayule bagasse for efficacy at removing pharmaceuticals. It was found that cotton gin biochar was more effective than biochar produced from guayule bagasse at removing sulfapyridine, docusate, and erythromycin and that removal was also greater for biochars produced at higher temperatures. In addition, removal increased as pH increased from 7 to 10. Results will be used to provide low cost treatment for removal of pharmaceuticals from wastewater used for irrigation at the point of use.
Review Publications
Bronson, K.F., Hunsaker, D.J., Meisinger, J.J., Rockholt, S.M., Thorp, K.R., Conley, M.M., Williams, C.F., Norton, E.R., Barnes, E.M. 2019. Improving nitrogen fertilizer use efficiency in subsurface drip-irrigated cotton in the desert southwest. Soil Science Society of America Journal. 83(6):1712-1721. https://doi.org/10.2136/sssaj2019.07.0210.
Filipovic, L., Filipovic, V., Walker, C.W., Williams, C.F., Gall, H., Watson, J.E. 2020. Modeling carbamazepine transport in wastewater-irrigated soil under different land uses. Journal of Environmental Quality. 49(4):1011-1019. https://doi.org/10.1002/jeq2.20074.
Wutich, A., Beresford, M., Bausch, J., Eaton, W., Brasier, K., Williams, C.F., Porter, S. 2020. Identifying stakeholder groups in natural resource management: Comparing quantitative and qualitative social network approaches. Society and Natural Resources. 33(7):941-948. https://doi.org/10.1080/08941920.2019.1707922.
D'Alessio, M., Durso, L.M., Williams, C.F., Olson, C.A., Ray, C., Paparozzi, E.T. 2020. Applied injected air into subsurface drip irrigation: plant uptake of pharmaceuticals and soil microbial communities. Journal of Environmental Engineering. 146(2). https://doi.org/10.1061/(ASCE)EE.1943-7870.0001655.
