Howard Weinberg
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UNC Chapel Hill
last updated 01/14/2008
Active Research
Characterization of the Chemical Constituents of Mixed Oxidant Disinfection
Occurrence of Selected Pharmaceutically-Active Compounds and Personal Care Products in Treated Wastewater and Drinking Water
The objectives of this study are to determine: the occurrence levels of selected pharmaceutically-active compounds (PhACs) and personal care products (PCPs) in the wastewater of a major southeastern utility in the US; the extent of PhAC and PCP removal by the various wastewater treatment processes employed at the utilitys wastewater reclamation plants; the occurrence levels of selected PhACs and PCPs in the utilitys raw and finished drinking water.
Twenty-four hour composite samples will be collected monthly for 12 months at a number of locations across the wastewater reclamation plants: The plants employ, in addition to conventional biological treatment, coagulation and granular media filtration, GAC, ozonation, and membrane filtration.
Analytical techniques will include gas chromatography/ mass spectrometry (GC-MS) and high performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) Target PhACs include diclofenac, gemfibrozil, metopropolol, propranonol, naproxen, primidone, trimethoprim, ciprofloxacin, ofloxacin, sulfamethoxazole, carbamezapine, dilantin, erythromycin, and meprobramate. PCPs of interest include DEET, triclosan, and caffeine.
Concurrent with the PhAC and PCP measurements, complementary data will be obtained from treatment plant staff detailing process operations for the day during which the composite samples were collected, such as BOD, COD, TOC, TKN, ammonia-N, nitrate-N, TSS, mean cell residence time, pH, temperature, applied ozone doses, granular media filter loading rate, membrane flux and pressure, GAC empty bed contact time, etc., for the wastewater reclamation plants, and chemical doses, pH, temperature, etc. for the water treatment plants. This latter information will be used to interpret variations in PPCP occurrence and removal patterns from month to month.
Impact of Residual Pharmaceutical Agents and their Metabolites in Wastewater Effluents on Downstream Drinking Water Treatment Facilities
a. Objectives: This research will assess the presence and subsequent impact of major use pharmaceutically active compound (PhAC) residues and their metabolites in the environment on drinking water quality and serve to determine whether this environmental issue warrants further investigation in the US In particular, the project will evaluate the occurrence, fate, and transport of these chemicals from wastewater treatment plant discharges upstream of drinking water treatment plants. The raw water feed to the potentially susceptible drinking water-treatment facilities will then be monitored through the various treatment steps of the plant including the sediments and finished water. The hypotheses that are to be tested are that; (i) residual PhACs in municipal wastewater treatment plant discharges persist in the receiving streams and can be transported to downstream water treatment plant intakes, (ii) conventional drinking water treatment processes do not effectively remove all of these residues, (iii) PhAC residues may be present in the particulate phase removed during the drinking water treatment process and in finished drinking water, (iv) the widespread use of antibiotics has led to the production of antibiotic resistant bacteria capable of penetrating treatment processes and persisting in and even multiplying in treated drinking water.
b. Approach: Using a combination of LC/MS and immunoassay techniques we will monitor sub nano-molar levels of major use antibiotics, blood lipid regulators, anti-inflammatories, b-blockers, hormone therapy drugs, and diagnostic chemicals in a variety of matrices: wastewater streams, raw water feeds to drinking water plants, and treated water from each of several treatment processes used during water treatment. We will also isolate selected types of bacteria from these waters, specifically E. coli, enterococci and Pseudomonas aeruginosa, and determine the prevalence and levels of resistance to a range of antibiotics. A bench-scale study using elevated levels of selected PhACs in a local vulnerable surface water will evaluate the potential for removal or conversion of these compounds by a variety of physical and chemical treatments under controlled conditions. Furthermore, we will use broadly targeted LC-MS techniques to learn the fate of the source PhACs if they are chemically converted during treatment. In particular, we will monitor their fate in chemical residuals (such as coagulant sludge) and attempt a mass balance to ensure a complete tracking of their fate and transport in the treatment process.
c. Expected Results: In addition to providing occurrence data on a wide range of major-use PhACs and their metabolites in basins and drinking water, the project will demonstrate whether the presence of antibiotics in waste streams and drinking water feeds is contributing to the increased prevalence of antibiotic resistant bacteria in the environment. These results will provide EPA with the basis to determine whether higher priority investigation of this subject is warranted in the US in order to assure the future health of the nation's drinking water supply.
Use of Indicators to Distinguish Between Point and Non-Point Sources of Chemical Contamination in North Carolina Streams
(Funded by the U.S. Geological Survey and Water Resources Research Institute of North Carolina)
Effluent discharged into receiving streams from wastewater treatment plants has to meet National Pollutant Discharge Elimination System permit levels on a variety of parameters that are designed to protect the stream's ecology and aquatic life from deleterious effects and to ensure that the natural flora and fauna can remediate the residual chemicals and micro-organisms prior to subsequent usage. As new chemicals are constantly being introduced into the domestic and industrial market, it is inevitable that they will be found in the raw waters entering these treatment plants. When their presence in receiving streams is undesirable, research studies are implemented to evaluate alternate approaches to control their levels in plant effluents. No equivalent gesture is guaranteed for the same fate of these chemicals originating from nonpoint sources. Consequently, downstream reservoirs and lakes are likely to be sinks for many of these compounds from a variety of unregulated sources. The management of nonpoint source contamination wasn't designed to account for the presence of chemicals with far different properties to those mimicking natural compounds and the presence of pharmaceutically and endocrine active chemicals with biological functions in environmental waters is testament to the ineffectiveness of current contaminant control. Drugs used for human and animal therapy and endocrine-disrupting compounds are introduced into agricultural systems via land application of recycled wastewater and accumulated biosolids as well as through direct usage of pesticides. The widespread domestic use of many of these compounds also ensures that they will be present in septic systems and in landfills. Leakage and runoff from any of these systems will contribute significant loading into receiving waters and contribute to impairment. It is unknown what percentage of accumulations of these compounds derive from point and non-point sources but from extrapolation of what is known about nonpoint pollution from regulated compounds, the contribution from the nonpoint sources is likely to be very significant.
Until now, it has been a major challenge to provide an effective strategy that would permit identification of non-point sources of chemical pollution as distinct from point sources. This proposal will investigate the use of chemical profiling that distinguishes between point and non-point sources of pollution and develop an approach for characterizing the contributions of surrogate measures of chemical contamination in the form of antibiotics and endocrine disrupting hormones and pesticides from land application runoff and on-site wastewater treatment seepage. The results of this study will provide an indication of the relative contributions to overall pollution from chemicals originating in both point and non-point sources and a strategy that can be applied to survey impaired streams for these chemicals.
Iodinated Acids and Iodide in Drinking Water Supplies: Method Development for ng/L Levels of Detection Relevant for Application in Occurrence Surveys
(funded by the American Water Works Association Research Foundation)
Iodoacetic acid is the most cytotoxic and genotoxic disinfection by-product (DBP) in mammalian cell assays reported in the literature, but methods for quantitative analysis in drinking water do not currently exist. Without them, no meaningful studies related to formation, control, and occurrence in drinking water can be undertaken. Iodoorganic compounds, such as iodomethanes and iodoacids, can be formed as DBPs during oxidation of iodine-containing drinking water such as could occur during disinfection. Some of these products have a very low taste-and-odor threshold (e.g., <1 µg/L for iodoform), while others are highly cytotoxic (e.g., iodoacetic acid is more than 250 times more cytotoxic than chloroacetic acid, which is one of the regulated haloacetic acids [HAAs]). Iodoacids have, thus far, only been identified in one chloraminated water that was high in bromide, but even this finding has raised the concern that concentrations in the ng/L range may be akin to the public health risks associated with mutagenic halogenated furanones (e.g., MX) at these levels. The Stage 2 regulation of HAAs and trihalomethanes has been predicted to drive many surface-water systems to chloramines. Thus, there is a concern over a risk/risk tradeoff (known chlorination DBPs for emerging chloramine DBPs such as iodinated acids). Therefore, it is essential to have in place a rugged, reliable, and easy to use analytical method that can obtain occurrence and control information in drinking waters across the nation. Similarly, there is no database on iodide levels in source waters, so it is difficult to accurately predict which sources will be most likely to generate these DBPs. This study will first develop a sensitive analytical method for iodoacids and then apply it, together with a modified version of a current method for the analysis of iodide and iodate (inorganic oxidation product of iodide), to perform a survey of occurrence levels across the U.S. and to be able to determine the fate of iodide during treatment. The analytical method will be developed from an exploration of different preconcentration techniques, such as solid phase resin and micromembrane extraction, with the objective of achieving reproducible and precise quantitation at the ng/L level. Ultimately, it will be important to know the levels at which these iodoacids occur in order to assess the potential for adverse environmental and human health risks. In addition, simulated batch reactions will compare the effect of free and combined chlorine on an iodide-spiked filtered plant water to evaluate whether iodoacids are indeed a by-product predominantly of chloramines.
The principal objective of this proposed research is to develop robust analytical methods for iodide at sub µ/L levels and iodinated acids at ng/L levels that can be used to determine occurrence levels in the nation's drinking water supplies. By applying these methods to batch reactor studies and occurrence surveys at plants using different treatment processes and source waters, the analysis of the fate of the source iodide will better help the drinking water industry understand how to minimize formation of the iodoacids by knowing under what conditions they form. Together, with the toxicological data on the acids, the drinking water industry will be in a better position to consider whether the occurrence levels are of concern and, if so, how best to protect consumers from exposure.
Characterization of the Chemical Constituents of Mixed Oxidant Disinfection
(funded by the Department of Homeland Security Advanced Research Projects Agency SBIR Program through the MIOX Corporation)
On-site generation technology utilizes common salt (sodium chloride) which is made in to a dilute brine solution that is converted in an electrolytic cell to a chlorine-based liquid disinfectant. The chlorine component is important since the US EPA requires a chlorine disinfection residual value in drinking water in the United States. There are no hazardous materials used, consumed or produced in the process. The product produced is not hazardous since the concentration of the oxidant is less than 1%. Operating costs are very low compared to chlorine gas or commercial sodium hypochlorite (bleach) since consumables are commonly available salt and electrical power. The commercial applications of this technology are significant world-wide and include potable water, wastewater, cooling towers, swimming pools, and other applications requiring a chlorine-based disinfectant. System sizes range from large municipal water applications to individual use devices for both the commercial and military sectors. Mixed-oxidant variants of the disinfectant have been demonstrated to reduce disinfection by-products (trihalomethanes and haloacetic acids) and provide other significant chemistry benefits for potable water, cooling towers, swimming pools, and other applications. However, the precise chemical composition of the mixed oxidant solution remains unknown knowledge that would help expand the technology as well as facilitate a clearer understanding of the superior disinfection of the chemistry involved in the process. This study will use a combination of electrochemical and spectroscopic techniques to understand the process of mixed oxidant chemistry more substantially.