Howard Weinberg
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last updated 01/14/2008
Recently Completed Research
(Click on the 'Results' link of any subject to see the published work.)
Evaluation of Bromate Uptake in Foods during Cooking
Drinking Water Disinfection Byproducts And Miscarriage
Occurrence of Drinking Water Disinfection Byproducts
Formation and Stability of Ozonation Byproducts in Drinking Water
Objectives
This project was designed to determine the levels of bromate that are taken up by food which is prepared in drinking waters containing this disinfection byproduct. The study was designed to evaluate whether cooked food provides an additional pathway for human exposure to bromate derived from drinking water and formed part of a collaborative partnership with Research Triangle Institute (RTI) based in the Research Triangle Park.
Specifically, we:
1. first developed a procedure for extracting, isolating, and quantifying bromate in a variety of food materials that were cooked in a variety of drinking waters prior to consumption.
2. utilized the analytical method developed in our laboratories at UNC for the sub mg/L levels of bromate in drinking waters. This methodology was applied to extracts obtained in objective 1.
3. evaluated a mass balance between bromate levels in the water used for cooking and the levels which were taken up in the cooked food to determine if this pathway of exposure is an additional risk factor that needs to be accounted for when evaluating MCLG levels of bromate in drinking water.
Approach
A variety of wet and dry foods were evaluated. Using the methods and expertise of the research group at RTI, we performed precise spiking of food materials, cooked the materials under controlled conditions in water, and then homogenized the cooked foods prior to extraction. We first evaluated a series of aqueous extraction and concentration procedures to recover spiked levels of bromate in wet foods following homogenization. The procedures focused on maximizing recovery (partitioning into the extracting medium) and stabilizing the extract prior to analysis.
It was anticipated that the extraction procedure that would be developed would be non-selective towards anions. As such, the extract would most likely contain low levels of bromate relative to other anion species and initial ion chromatographic analysis of serial dilutions of such extracts was performed to determine the ionic strength of the extract. By matching this value to the capacity of the ion chromatographic column, it was possible to determine appropriate sample handling to ensure that the column capacity was not exceeded. Routinely-practiced IC methodologies for bromate in water using conductivity detection is limited in sensitivity due to coelution of chloride with bromate. It was our intention to apply the methodology developed in our laboratories to alleviate this outcome. This method employed a post-column reaction with UV detection that is invisible to the majority of anionic species that elute from the chromatographic column.
Although the major source of bromate in drinking waters is associated with the ozonation of bromide-containing source waters, recent evaluations by our research group have determined that hypochlorite-treated waters are an additional source. This is of particular concern due to the large number of treatment plants utilizing hypochlorite in their finished water. Due to the manufacturing constraints of the hypochlorite raw material, average levels of bromate associated with chlorination exceed 1mg/L. We evaluated the impact of foods cooked in waters from hypochlorite-treated waters as well as those with preliminary ozonation. We assisted in the identification of treatment plants with a range of treatment processes and finished water quality so that this project could demonstrate application across the spectrum of drinking waters available in the United States. We determined the levels of bromate in the waters used for cooking both prior to and after cooking, and in the food that was cooked. We investigated the cooking parameters to evaluate the partition coefficient of bromate from the food materials into the water. With these sets of results, we evaluated a mass balance between the initial levels of bromate in the water and the final levels of bromate in the food.
b. Approach: An ion chromatographic system resolved the oxyhalides which combined with a post-column reagent generating the tribromide ion which was detected in a UV detector. The operating parameters of each segment of this process were optimized for maximum sensitivity towards all known oxyhalides in synthetic solutions containing a controlled ionic strength and organic carbon background. Following evaluation of appropriate quenching procedures, the method was applied to a wide variety of drinking waters derived from different treatment processes. In addition to waters from treatment plants, bottled waters, filtered waters, and boiled waters were assessed.
c. Results
d. Estimated Improvement in Risk Assessment/Management: If the 10-5 excess cancer risk for bromate in drinking water is indeed 0.5mg/L, this project will provide a sensitive and direct analytical method for the measurement of bromate at this level, and will allow for bromate levels in finished drinking water to be assessed at concentrations where they are presumed to adversely impact public health. If such levels can be measured, then alternative disinfection methods can be evaluated, and the conditions under which disinfectants are applied can be altered to lower bromate formation and thereby reduce the risk of exposure to harmful levels of bromate. This cannot be accomplished very easily with the current methods available for bromate analysis.
Assessment of Trace Element Concentrations in Municipal Wastewater Treatment Plant Discharges in North Carolina
Summary: A number of municipal wastewater treatment plants in North Carolina appear to periodically violate their NPDES discharge requirements with respect to trace contaminants. The most frequently-cited violations have been for mercury, cadmium, and cyanide but it appeared likely that these "apparent" violations stemmed from the fact that the permitted discharge levels for these contaminants tended to be close to their practical limits of quantitation using conventional procedures for analysis of these trace elements. Accordingly, the objectives of the proposed research project were to develop a workable protocol for analysis of these trace contaminants and to ascertain, using this protocol, whether or not the levels of trace contaminants in the effluents from a select group of wastewater treatment facilities in North Carolina were truly in excess of their permitted levels. Sources of error associated with existing methods of analysis were identified. If the concentrations did indeed exceed permitted levels, attempts were made to identify the cause(s). The focus of the study was on mercury, cadmium, and cyanide because these are the trace contaminants that appeared to violate permitted levels most often.
Approach:
After meeting with the USEPA's Environmental Monitoring and Support Laboratory (EMSL) in Cincinnati to determine the most appropriate sample handling and analytical techniques for measurement of these trace contaminants the research team met with scientists and regulatory personnel of the North Carolina Division of Environmental Management (DEM), particularly with their laboratory personnel, to determine acceptable sampling and analytical procedures and expectations for analysis of the subject trace contaminants. Analytical protocols were developed by the project team to identify the key issues and the possible sources of error associated with the measurement of the there species in wastewaters and an approach proposed to resolve these issues. A collaboration with OI Analytical permitted application of a newly developed analytical method using flow injection alongside the established acid distillation approach for cyanide analysis. Sampling trips to participating utilities collected grab and composite samples from different points in the treatment process (i.e. influent, primary effluent, secondary effluent, final effluent prior to disinfection, digester supernatant) and analyses split between the utility, contract, State, and UNC laboratories. Sampling protocols were developed in consort with representatives of the facilities being sampled and were strictly followed by all participants. Since the flow injection procedure permitted multiple sample analysis at a few minutes per sample compared to two hours per sample using the traditional distillation technique, it was possible to carry out very strict quality control that identified major problems with the complex pre-treatment strategies that account for interferences but are often not followed. One outcome from this study was the direction given to utilities in the need to scrutinize more carfeully the data and detail provided by contdact laboratories, not to take short-cuts on complex methods, and to consider replacing laborious time-consuming methods with those using new technology that eliminate large systematic errors. On a scientific level it became apparent that in some waters, cyanide was being formed during the procedures used to stabilize the samples prior to analysis.
The results of this study are presented in three publications:
(i) Report from the Water Resources Research Institute of North Carolina who funded the project
(ii) Segmented Flow Injection, UV Digestion, and Amperometric Detection for the Determination of Total Cyanide in Wastewater Treatment Plant Effluents by H.S. Weinberg & S.J. Cook. Anal. Chem., (2002) 4(23), 6055-6063.
(iii) Insights into False Positive Total Cyanide Measurements in Wastewater Plant Effluents by H. Weinberg, S. Cook, and P.C. Singer. 2005. Water Environment Research, 77(5).
Formation, Occurrence, Stability, and Dominance of Haloacetic Acids and Trihalomethanes in Treated Drinking Water
Research Objectives: The objective of this project was to investigate the relative occurrence of haloacetic acids (HAAs) and trihalomethanes (THMs) in treated drinking waters, and to determine water quality, treatment, and distribution system conditions which influence their relative concentrations. THM formation has been well-studied, and THMs tend to be stable in water distribution systems. HAAs are less well-studied, and their kinetics of formation and stability need to be characterized. In order to understand the underlying causes of the relative differences in THM and HAA formation in different waters, a controlled study needs to be conducted in which the various contributory factors are investigated.
Technical Approach: All four Br- and Cl-containing THMs and all nine Br- and CL-containing Haas were measured as part of this investigation. Studies were conducted both on a bench-scale and in the field, at actual full-scale treatment plants and their respective distribution systems. The study had four components: (1) a laboratory phase of controlled investigations to assess the stability of the different HAA species under a variety of solution conditions; (2) a bench-scale, controlled, laboratory chlorination study in which six waters with differing NOM characteristics from different regions of the US were spiked with different amounts of bromide and chlorinated under a variety of solution conditions. The bench-scale studies also included chlorination before and after optimal coagulation of the waters, and hydrophobic/hydrophilic fractionation of the NOM and chlorination of these fractions; (3) a controlled biostability study in which annular reactors and biologically active filters were used to evaluate the biodegradability of different HAA species under different conditions; and (4) a full-scale plant study to assess the distribution and speciation of THMs and Haas in a variety of different waters from geographically diverse regions, with differing water quality, treatment, and distribution system characteristics. For the full-scale plant studies, sampling at each utility was conducted at the same time as the utilities were conducting their ICR sampling so that the findings would complement each other. This also provided a quality assurance check, allowed for a comparison between HAA5, HAA6, and HAA9, and assured that the appropriate water quality and treatment data that were needed for interpretation of the findings were available.
This study was a 5 year collaborative research project between the Departments of Environmental Sciences and Engineering and Epidemiology in the School of Public Health and the Ob/Gyn Department of the Medical School. The project, which began in January 2000, addressed the potential for exposure to elevated levels of drinking water disinfection byproducts to increase the risk of spontaneous abortion in women. By selecting populations served by distinctly different drinking water qualities and ensuring similar exposure throughout the target population, it was further intended to demonstrate whether the correlation is specific to a particular component of the water which may only be present in certain parts of the country.
This study addressed the following research questions:
1. Is living in an area served by water with elevated levels of DBPs associated with increased risk of spontaneous abortion?
2. Is living in an area served by water with elevated levels of chlorinated DBPs, brominated DBPs, or individual DBP species associated with increased risk of spontaneous abortion?
3. Are women who receive water with elevated levels of DBPs and ingest greater amounts of that water at increased risk of spontaneous abortion relative to those women who drink lesser amounts of water from the same source?
4. Do the patterns of association between DBPs and spontaneous abortion differ for losses that occur less than 12 weeks after the LMP verse later than 12 weeks after the LMP, with different stages of development prior to loss as assessed by ultrasound?
5. Is there an association between exposure to DBPs and reduced fetal growth, as measured by small-for-gestational-age births or preterm birth?
6. What is the contribution of tap water THMs to blood THM levels?
The project involved some intense monitoring of water quality in targeted regions of the country both from the distribution systems and consumers' taps. Strategies were developed to ensure accurate collection and analysis of these samples and to provide an accurate reflection of subjects' exposure to disinfection byproducts. This latter goal was aided by the analysis of DBPs in subjects' blood.
a. Objectives: A project was proposed to study a wide-range of newly identified byproducts resulting from the use of various disinfectants in drinking water treatment. This study first refined and adapted existing methods and investigated new methodologies for targeting a list of 49 of these compounds and then applied these methods to study the impact of water quality parameters on the formation and stability of these compounds in treated and distributed drinking waters. The objectives beyond the development of appropriate quality assured analytical methods were, therefore, to investigate the relative occurrence of these byproducts in treated drinking waters, and to determine water quality, treatment, and distribution system conditions which influence their relative concentrations, persistence and stability.
b. Approach: The pool of targeted byproducts listed in the RFA result from studies using chlorine, chloramines, ozone, and chlorine dioxide in drinking water treatment. Many of these studies were performed on synthetic solutions of natural organic matter under controlled laboratory conditions and there is little, if any, occurrence data of these compounds in full-scale treated water. In many cases, only tentative identification of these byproducts has been cited in the literature due to the absence of confirmatory standards. Furthermore, there was little attempt to quality assure the data generated or determine the sample handling conditions to ensure analyte stability. This research first obtained or synthesized pure standards of the targeted compounds to enable determination of the optimal sample handling and preservation conditions and utilized a combination of extraction and derivatization techniques to minimize artifactual formation and maximize recovery from the aquatic matrix. Positive identification was achieved by a combination of complimentary spectroscopic tools, some of which were designed to target a broader range of byproducts beyond those listed. Once methods for the target byproducts were established, studies of their formation and stability were conducted at full-scale treatment plants and their respective distribution systems. These plants were selected to assess the distribution and speciation of byproducts in a variety of different waters from geographically diverse regions, with differing water quality, treatment, and distribution system characteristics. In particular, each of the plants demonstrated competence with the treatment technologies they employ and are committed to providing accurate operational information and complimentary water quality analyses.
c. Results
Formation and Stability of Ozonation Byproducts in Drinking Water
a. Objectives: A project was proposed to study a wide-range of byproducts (BPs) resulting from the combined use of ozone (as a pre-oxidation treatment) with terminal disinfectants chlorine and chloramine. This study first investigated new methodologies for targeting as yet unidentified byproducts and then applied these as well as refined existing techniques for studying the impact of water quality parameters on the formation and stability of these compounds in distributed drinking waters. The objectives were, therefore, to investigate the relative occurrence of these byproducts in treated drinking waters, and to determine water quality, treatment, and distribution system conditions which influence their relative concentrations. Their kinetics of formation and stability needed to be characterized and in order to understand the underlying causes of the relative differences in byproduct formation in different waters, a controlled study needed to be conducted in which the various contributory factors are investigated.
b. Approach: The pool of identifiable byproducts resulting from the combined use of ozone and post-disinfectant was expanded by targeting compounds observed in the literature from laboratory studies on synthetic solutions containing natural organic matter (NOM) in a variety of treatment scenarios. Since many of the literature citations illustrate only tentative identification of byproducts, this research utilized a combination of in-situ derivatization techniques in combination with solid phase extraction (particularly micro-extraction) to target a broad range of polar byproducts produced by ozonation that might be subsequently chlorinated by post-disinfectant. Positive identification was achieved by a combination of complimentary spectroscopic tools. Once the target byproducts were established, studies of their formation and stability were conducted both on a bench-scale and in the field, at actual full-scale treatment plants and their respective distribution systems. The study had three components: (1) a laboratory phase of controlled investigations to assess the stability of the different byproduct species under a variety of solution conditions; (2) bench-scale, controlled, laboratory ozone/chlorination and ozone/ chloramination study in which six waters with differing NOM characteristics from different regions of the US were spiked with different amounts of bromide and ozonated/disinfected under a variety of solution conditions. The bench-scale studies also included disinfection before and after optimal coagulation of the waters, and hydrophobic/hydrophilic fractionation of the NOM and chlorination of these fractions; and (3) a full-scale plant study to assess the distribution and speciation of byproducts in a variety of different waters from geographically diverse regions, with differing water quality, treatment, and distribution system characteristics.
c. Results
d. Improvement in Risk Assessment: If the known byproducts of ozonation and post-disinfection have either known toxicological risks or at least suspected health implications to consumers exposed to them, it is likely that the unidentified byproducts add even more to this uncertainty. It is, therefore, essential to learn of the fate of these byproducts in drinking water distribution systems and determine their impact on the quality of water supplied to consumers. This project provided the tools to determine if current ozone-disinfectant practices offer a significant health risk to consumers or if they are achieving their goal of risk reduction from disinfection BPS.