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United States Department of Agriculture

Agricultural Research Service

Research Project: Reuse of Treated Municipal Waste Water for Irrigation as a Means to Increase Alternative Water Supplies

Location: Water Management and Conservation Research

2013 Annual Report

1a. Objectives (from AD-416):
Objective 1: Develop new and novel water quality indicators (biological and chemical) for assessment of reclaimed water quality. Objective 2: Determine the processes that govern the fate and transport of emerging contaminants, pathogens, and nutrients found in treated wastewater used for irrigation to provide a research basis for potential regulation of these constituents. Objective 3: Develop and optimize small on-site treatment systems to reduce emerging contaminants and pathogens found in domestic waste water used for irrigation.

1b. Approach (from AD-416):
Field data from sites where treated effluent has been used will be gathered and used to determine the presence and suitability of selected emerging contaminants and pathogens found in treated municipal wastewater as indicators. Qualitative and quantitative enzyme-linked immunosorbent assays (ELISA) will be developed for the identified wastewater indicators. Environmental samples will be taken and analyzed for nutrients, pathogens, and emerging contaminants. Distribution of nutrients, pathogens, and emerging contaminants will be used to determine which constituents may be accumulating in the environment for further investigations. Using a combination of lab studies fate and transport parameters will be determined for the identified constituents. Concurrently, a series of laboratory and field experiments will be conducted to determine the development of antibiotic resistance in native soil microbial populations. Finally, a small scale, low input treatment systems will be developed and validated to provide improvement in water quality and increased water supply by treating household wastewater.

3. Progress Report:
Significant progress has been achieved in all three objectives related to emerging contaminants. However, work related to pathogens and indicator organisms has not progressed due to a scientist vacancy and subsequent abolishment due to reductions in appropriations. Currently, there is no microbiological expertise devoted to the project. Commercially available antibodies for several emerging contaminants have been identified and are being evaluated for Enzyme-Linked Immunosorbert Assay (ELISA) development. Initially, non-specific interactions between primary and secondary antibodies were observed. A series of cross reactivity experiments were conducted to isolate and eliminate these cross reactions. Currently a system of two primary antibodies and one secondary antibody have been determined for three compounds (carbamazepine, ciprofloxacin and caffeine) for development of a 'sandwich' ELISA. Annual loading rates of emerging contaminants at a ground water recharge facility were determined. Deep percolation (> 1m) of these compounds were also quantified by collecting solution samples from the soil profile. The concentration of emerging contaminant found in solution samples were related to the mass sorbed to soil. The reduction of redox sensitive emerging contaminants was also measured at depths <1 meter below the surface of the recharge basin. Sorption of the antibiotic lincomycin was found to be effected by pH and the non-equilibrium sorption of the drug carbamazepine was quantified. Additionally, soil profile analyses of nutrients to 1 m have been completed. Nutrient analysis shows that extractable nitrate and boron are at very low levels throughout the profile. Phosphorus concentrations, on the other hand are high, especially in the surface layers. A Material Transfer Research Agreement (58-5347-3017) has been entered into with Forret Plasma Labs to investigate the use of a plasma arc system for treatment of household wastewater and the potential for removal of emerging contaminants from municipal wastewater. The plasma arc system has been setup at the Arid Land Agricultural Research Center and initial testing is ongoing.

4. Accomplishments
1. Sorption of the antibiotic lincomycin to arid regions soils and the influence of pH. The reuse of sewage effluent for irrigation is an effective way to increase water supplies in the desert southwest. Contaminants such as antibiotics, found in treated effluent, have been identified as a potential problem for use of this water for irrigation. Scientists at the US Arid-Land Agricultural Research Center, Maricopa, Arizona, determined environmental fate parameters for lincomycin using three arid region soils. It was found that lincomycin sorption is related to soil pH. When soil pH is below 7.6, lincomycin exhibits little sorption to soil, however, when soil pH is above 7.6 sorption of lincomycin is increased 10 fold. These results can be used to determine site-specific guidelines for disposal and use of reclaimed water.

2. Increased environmental mobility of the human drug carbamazepine due to non-equilibrium sorption. The reuse of sewage effluent for irrigation is an effective way to increase water supplies in the desert southwest; however, contaminants such as human drugs, found in treated effluent, have been identified as a potential problem for use of this water for irrigation. Batch equilibrium soil sorption (KD), defined as the mass of compound sorbed to soil at a specific solution phase concentration, is commonly used to determine the mobility of organic compounds in soil. Scientists at the Arid-Land Agricultural Research Center in Maricopa, Arizona, conducted a comparison between KD from a flow through system and a batch equilibrium system. The KD from the flowing system was found to be greater than from batch adsorption. The flowing system also indicated that increasing water flow rate and repeated solute pulses resulted in progressively lower KD's. This indicates that the risk of carbamazepine leaching to groundwater increases with increased water velocity and multiple applications. These results can be used to alter irrigation and groundwater recharge practices with treated effluent to protect groundwater.

3. The uptake of 20 human drugs in irrigation water by nasturtiums. The use of reclaimed municipal sewage for irrigation can be seen as a potential new source of water in arid and semi-arid regions of the world. One potential obstacle to reusing reclaimed water for irrigation of food crops is the uptake of emerging contaminants and the introduction of these compounds into the human food chain. Scientists at the Arid-Land Agricultural Research Center in Maricopa, Arizona, irrigated nasturtiums with solutions containing 20 different drugs for 90 days and harvested to determine the mass of drug accumulated. In general, it was found that the highest drug concentrations were found in the leaves and roots. High concentrations of drugs in the roots is attributed to being in contact with the soil and high concentration in the leaves is attributed to the drugs being left behind after evaporation. The accumulation of emerging contaminants in leaves has implications for irrigating leafy vegetables, like lettuce, for human consumption and could lead to crop specific irrigation recomendations.

Last Modified: 05/27/2017
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