2009 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).
A lab-scale system is being developed & validated to investigate the soil leaching characteristics of emerging contaminants and pathogens found in treated waste water. The system uses a flow through column to determine the ability for soils to decrease the movement of contaminants found in waste water. The system has been used to show that the kinetics of sorption to the soil is a function of flow rate and application frequency. Operational parameters have also been determined to allow for the investigation of pathogen transport through soil. Re-growth of pathogens outside of the soil column will invalidate results of column experiments so a temperature control system has been devised and tested that limits growth while preventing death of the pathogens when they are not in contact with the soil.
Indicator bacteria found exclusively in feces have been used to monitor water samples for fecal contamination for decades. However, many bacterial methods used for fecal monitoring have been developed for use in relatively clean (drinking or surface water) samples and their utility for use in reclaimed water is largely unknown. The effectiveness of Salmonella and E. coli as indicators in soil and reclaimed water was investigated. Salmonella was found to be extremely rare in reclaimed water samples; future monitoring for this pathogen will be performed only on un-treated wastewater samples. The bacterial group Enterococcus was also evaluated and added as an indicator in all reclaimed water quality studies.
Continual exposure of pathogens to antibiotics can lead to the development of antibiotic resistance. A study was begun to assess antibiotic distribution and the development of antibiotic resistance in enterococci isolated from soils undergoing recharge with reclaimed wastewater. Soil cores were collected and more than 200 isolates have been collected for resistance analysis. Additionally, cores are being prepared for extraction and analysis of antibiotics that will be correlated to the development of antibiotic resistance.
A collaborative study with University of Arizona focused on transport and survival of E. coli in recharge basin soils. Modeling of data revealed that recharge water movement through urban stream beds decreased levels of organic pollutants but increased fecal indicator bacteria, information critical to sustained urban water resource management.
A physical scale model of a water distribution and irrigation system has been designed and the parts are being purchased. The system has been designed to use similar materials and recreate areas of turbulence similar to in-place systems that will allow for investigation of pathogen re-growth, degradation of emerging contaminants and possible treatment methods.
Stakeholders identified algal production in wastewater holding ponds as a serious concern; algae can clog irrigation systems and also have the ability to produce compounds that are highly toxic to humans and animals. Cyanobacteria (blue-green algae) were added as an indicator for monitoring pond water quality, and molecular methods were validated for quantifying both general and toxin-producing cyanobacteria in soil and water.
Survival of E. coli in stormwater flows. The presence of pollutants in water resulting from monsoonal flows is of concern because these waters move from riverbeds to recharge basins, where they are used to replenish depleted groundwater supplies. A collaborative study between ARS scientists at Maricopa, AZ and University of Arizona researchers focused on transport of chemical contaminants and survival of E. coli in stormwater flows in Tucson, Arizona. Modeling of the data collected over two years revealed that stormwater movement through urban Tucson stream beds decreased levels of organic pollutants in the stormwater but increased E. coli levels. This water quality information will be critical to sustained urban water resource management in semiarid areas.
Mobility of carbamazepine, the human drug, in soil. Emerging contaminants such as drugs, hormones, personal care products and endocrine disrupting compounds are prevalent in treated municipal waste water. A lab-scale system has been developed and validated to investigate the soil leaching characteristics of emerging contaminants. Results show that there is a kinetic component to sorption of the human drug carbamazepine to soil that affects environmental fate. ARS scientists at Maricopa, AZ found that as the velocity of the water carrying the carbamazepine through the soil increases, the amount of carbamazepine sorbed to the soil decreases. In addition it has been shown that repeated application of carbamazepine results in increased mobility due to already ‘occupied’ sorption sites. These results provide guidelines such reducing water application rates and allowing sufficient time between applications to protect groundwater contamination.
Waste water recycling at a latex extraction facility. Wastewater from a processing plant that extracts latex from guayule is difficult to dispose of due to high pH (>12), odor and the presence of hydrophobic organics. These factors result in disposal difficulties. ARS scientists at Maricopa, AZ determined that up to 50% of the wastewater could be recycled within the processing plant and not affect latex recovery. Additionally, the resulting wastewater can be treated to remove the odor and hydrophobic organics as well as lower the pH. The proposed treatment is lowering pH with acid followed by sedimentation; the resulting water has a neutral pH with no odor or hydrophobic organics. The resulting water has the benefit of being a fertilizer containing both nitrogen and potassium. The results will be used to increase the economic viability of domestic latex and rubber production.
|Number of Other Technology Transfer||2|
Coffelt, T.A., Williams, C.F. 2009. Characterization and recycling of waste water from guayule latex extraction. Industrial Crops and Products (29), pp. 648-653.
Williams, C.F., Letey, J., Farmer, W.F. 2006. ESTIMATING THE POTENTIAL FOR FACILITATED TRANSPORT OF NAPROPAMIDE BY DISSOLVED ORGANIC MATTER. Soil Science Society of America Journal. doi:102136/sssaj2001.0063, pp. 24-30.