2010 Annual Report
1a.Objectives (from AD-416)
(1) Provide baseline data to evaluate the long-term effects of irrigation with treated wastewater; (2) Understand proceses that govern the fate and transport of emerging contaminants, pathogens and nutrients found in treated wastewater used for irrigation; Investigate the use of Ozone as a treatment for emerging contaminants in irrigation systems and (3) Develop guidelines for the safe reuse of treated wastewater for irrigation.
1b.Approach (from AD-416)
Sites will be determined where wastewater application has occurred. Soil 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 soils for further investigations. Using a combination of lab, column and lysimeter 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 persistence of pathogens and emerging contaminants in delivery systems. Removal and transformations of nutrients and emerging contaminants as well as pathogen regrowth will be measured throughout the systems. Results and data will be used to identify problems inherent in wastewater irrigation. Constituents that pose a potential environmental risk will be identified and the fate and transport parameters developed will be used to formulate potential management options that could reduce potential environmental degradation. Formerly 5347-13320-001-00D (12/06). FY09 Program Increase of $40,438.
A lab-scale treatment system has been developed and validated to investigate the ability to provide on-site treatment for pathogens and emerging contaminants. The treatment system utilizes commercially available disinfection systems and has the potential to provide treatment with a capital investment of less than $4,000. Various treatment options are being investigated. They include chlorination, ozone, and UV treatment. Operational parameters such as flow rates and concentration of disinfecting compounds have been determined. Initial results indicate that both pathogens and emerging contaminants can be oxidized by the treatment system. This would indicate that on-site treatment of waste water for irrigation is possible and not cost prohibitive.
Sampling has continued at a ground water recharge facility for the distribution of emerging contaminants and the development of antibiotic resistance within the soil microbial community. A second year of soil cores were collected. Soil cores from the first year were extracted and analyzed for emerging contaminants and the second year cores are currently undergoing extraction for analysis. The cores from the first year of sampling were analyzed for the development of antimicrobial resistance. High level resistance to 16 antibiotics was measured. A number of soils were found to contain microbes with significant resistance. First year cores have also been analyzed for the pharmaceutically active compounds carbamazepine, lincomycin, ibuprofen, and caffeine. The distribution of the pharmaceutically active compounds can be related to soil chemical and physical properties.
The reuse of sewage effluent for irrigation is an effective way to increase water supplies in the desert southwest. Contaminants such as human drugs, found in treated effluent, have been identified as a potential problem for use of this water for irrigation. ARS Scientists in Maricopa, AZ, found that the mobility of carbamazepine increased with increasing pore-water velocity and that repeated applications of carbamazepine also increased potential mobility. This would indicate that the use of reclaimed waste water for long-term irrigation has the potential to lead to movement of carbamazepine to ground water. However, the potential for carbamazepine degradation within the soil environment has not been investigated and the sorption of carbamazepine determined in this study would allow ample time for biodegradation.
Healthy Research Bacteria. It has been proposed that the input of resistant bacteria into the environment through wastewater treatment is a key source of antibiotic resistance that has extensive implications to public health. More than two million Americans are infected each year with resistant pathogens and 14,000 die as a result. Studies conducted by ARS scientists in Maricopa, AZ, (200 isolates collected from 50 soil cores) show similar antibiotic resistance levels in soils isolated from wastewater recharge basins and from irrigation pond sediments, and that multidrug resistance is higher in bacteria isolated from sediments with no exposure to reclaimed water. This information on the development and transport of antibiotic resistance will be crucial to public health professionals working to halt the spread of resistance in clinically-important bacterial strains.
Williams, C.F., Coffelt, T.A., Watson, J.E. 2009. Increased soil sorption of pendimethalin due to deposition of guayule-derived detritus. Soil Science Society of America Journal. 73(6):1952-1957.