2002 Progress Report: Impact of Residual Pharmaceutical Agents and their Metabolites in Wastewater Effluents on Downstream Drinking Water Treatment FacilitiesEPA Grant Number: R829014
Title: Impact of Residual Pharmaceutical Agents and their Metabolites in Wastewater Effluents on Downstream Drinking Water Treatment Facilities
Investigators: Weinberg, Howard S.
Current Investigators: Weinberg, Howard S. , Singer, Philip C. , Sobsey, Mark D. , Meyer, M. T.
Institution: University of North Carolina at Chapel Hill
Current Institution: University of North Carolina at Chapel Hill , United States Geological Survey
EPA Project Officer: Page, Angela
Project Period: August 27, 2001 through August 26, 2004 (Extended to August 26, 2006)
Project Period Covered by this Report: August 27, 2001 through August 26, 2002
Project Amount: $524,992
RFA: Drinking Water (2000) RFA Text | Recipients Lists
Research Category: Drinking Water , Water Quality , Water
The results of the U.S. Geological Survey's reconnaissance studies of pharmaceutical agents in the aquatic environment are being used to focus a study on the occurrence, fate, and transport of these chemicals from the point of discharge from wastewater treatment plants to the finished product in drinking water treatment. The objectives of this research project are to determine answers to the following questions:
(1) Can models, such as Estimation Program Interface (EPI) suite, efficiently predict the environmental fate and toxic effects of pharmaceutical compounds? We will investigate various model predictions after evaluation against the known effects of other environmental triggers (such as pesticides) with the objective of prioritizing compounds by their health endpoints, and then determine which of these can be expected to persist and be present in the different matrix environments.
(2) Where the models predict significant partitioning out of the aqueous phase, can approaches be developed to obtain a mass balance on target compounds as they transport through watersheds?
(3) What is the fate of these agents during chemical treatment of wastewater (such as chlorination), and if these "byproducts" are not significantly changed in structure, do they possess the same potential environmental impacts as their parent compound?
(4) Can antibiotics or their environmental degradates contribute to the evolution of antimicrobially resistant bacteria, as a major-use group of pharmaceutical products?
During Year 1 of the project, we have been careful to evaluate the results of ongoing studies elsewhere to identify the major gaps in knowledge, and the best approaches to generate a more complete understanding of the fate of major-use pharmaceutical compounds in the aquatic environment. After a thorough review of the literature, we have decided to focus on a few select groups of compounds that either have not been previously studied, or for which insufficient or incomplete fate data are available. In the first phase of this research project, we will be studying four groups of antibiotics (tetracyclines, sulfonamides, fluoroquinolones, and macrolides), x-ray contrast media, antiepileptics, antidepressants, and hormone therapy drugs. Model predictions indicate that these chemicals would most likely resist removal during conventional wastewater treatment, and that there would be significant partitioning into soil and sediments by the target compounds once they are discharged into receiving streams. Significant method development has occurred, which accounts for the presence of natural organic matter in the background of extracts of aqueous samples, and uses significant concentration factors with solid-phase extraction to achieve detection limits below 10 ng/L. Analysis of these compounds uses gas chromatography with ion trap mass spectrometric detection of derivatized acidic and neural compounds, or liquid chromatography with triple quad mass spectrometry for the analysis of antibiotics and identification of degradates. We currently are achieving 50-80 percent recovery of the target compounds from various aquatic matrices. It appears that many of the antibiotics are chemically altered during wastewater disinfection, which accounts for a low number of detections in surface waters to date. We are identifying the structure of these byproducts, and hope to begin tracking their fate during discharge and subsequent transport into watersheds. Application of these methods to an initial survey of other target compounds that we have selected for study has revealed their presence in some local surface waters.
In anticipation of finding many of these compounds in the source water of drinking water treatment plants, we have begun to investigate their fate during treatment. We initially are studying transformation products during oxidation (ozone) and chlorination, as well as the effects of advanced oxidation using a combination of ozone, peroxide, and ultraviolet photolysis experiments under laboratory-controlled conditions. Initial results indicate that such treatment changes the concentrations of the parent compounds, but that in most cases, byproducts of yet unknown identities are formed.
Another focus of this research project is to study appropriate strategies for determining the evolution of antimicrobially resistant bacteria from contact with antibiotics. For this part of the research project, we are evaluating two different monitoring approaches; membrane filtration and the Colilert/Enterolert method. Both methods have significant advantages and disadvantages, making the choice not straightforward. With membrane filtration, it is possible to obtain absolute bacterial counts, assay large volumes of samples, and detect Escherichia coli, Enterococci, and Pseudomonas. False positives are obtained; however, as a result of fluorescence of colonies other than the target microbes. False negatives are obtained as a result of clogging of the filter, in which case it is difficult to recover damaged bacteria, and a large amount of preparative work is needed. With the Colilert/Enterolert method, much less workup is involved, a much lower probability of false positives exists, and equally reliable if not more reliable results are obtained than by membrane filtration. The major disadvantages of this method are its inability to detect Pseudomonas, and the fact that it is limited to the analysis of a 100-mL sample, which can be restrictive when searching for low levels of resistant bacteria. We will determine whether the method of choice can detect resistant bacteria in sample waters, and possibly correlate their presence to those of antibiotic residues. We then will track the fate and incidence of resistant bacteria through water basins, and will determine the concentration of antibiotics at which microbes can acquire resistance as well as the time it takes to acquire such resistance. Once acquired, we will determine whether the resistance remains in the absence of the selective pressure of the antibiotic, and whether the resistance is transferable. This will be achieved by monitoring the acquisition of resistance genes in a controlled environment before attempting to detect and isolate resistant bacteria in environmental samples.
During Year 2 of the project, we will attempt to: (1) identify the degradates of the target compounds that result from disinfection in wastewater; (2) assess the effects of oxidation and advanced oxidation on these and the parent compounds; and (3) perform experiments to determine resistance acquisition in bacteria by exposure to antibiotics in aquatic environments. Method development will focus on approaches for effectively isolating the target compounds and their byproducts from soils and sediments, as well as the consideration of expansion of the target groups.