Non Technical Summary
It is well known that elevated dissolved organic carbon (DOC) in surface water is a threat to water quality and DOC is the precursor for disinfection byproduct (DBP) formation in drinking water, which has been of environmental and public health concerns. In an effort to safeguard human health in rural community, developing cost-effective technology for controlling DBP formation is urgently needed, especially in small drinking water treatment systems. Fenton or Fenton-like advanced oxidation reactions have been previously used for the degradation of organic contaminants in wastewater treatment and Superfund site remediation. This proposed project is to develop Fenton or Fenton-like advanced oxidation process as an effective strategy to reduce DOC in source water and control carcinogenic DBP formation in drinking water. If successful, results generated from this research will substantially contribute to fundamental understandings of chemical mechanisms on DOC degradation and DBP formation during drinking water treatment and lead to a cost-effective and environmental-safe technology for DBP mitigation in drinking water treatment facilities in rural community. Results would also have greater economic impacts as it will help reduce medical claims by residents consuming drinking water with elevated DBPs and the costs of labor and equipment demand for chlorine handling in drinking water treatment processes.
Animal Health Component
Research Effort Categories
Goals / Objectives
Overall goal of this project is to develop cost-effective Fenton and Fenton-like advanced oxidation technology as a practical strategy to control carcinogenic DBPs formation in drinking water and safeguard human health in rural areas, with an integrated approach of laboratory studies and mathematical modeling. Specific objectives include: i) Identifying optimal conditions for the formation of hydroxyl radicals in Fenton process. This task is to systematically investigate the factors that affect the formation of hydroxyl radicals in Fenton process under the conditions relevant to drinking water treatment process. The key parameters that will be investigated include pH, alkalinity, the concentrations of ferrous iron, and the concentrations of DOC.ii) Investigating optimal conditions for the degradation of THM precursors by Fenton process. This task involves the selection of appropriate treatment conditions that are most effective in reducing THM precursors. DOC will be isolated into three to four groups by selective procedures. Each group of DOC will be evaluated in terms of THM formation potential before and after treatment.iii) Developing Fe-GAC catalysts with optimal surface characteristics for THM precursor destruction at circumneutral pH. This task focuses on the preparation and characterization of the Fe-GAC catalysts, including selections of GAC, optimization of iron content and distribution, crystal structure, and surface modification with selected Lewis acids.iv) Identifying major parameters affecting THM precursor destruction in Fenton-like process. This task is to a) probe ?OH generation mechanism through heterogeneous Fenton-like precoess; b) differentiate THM precursor removal pathways and quantify the rates of the corresponding pathways; c) quantify the effects of various parameters affecting the DBP precursor destruction.v) Developing proper strategies for Fe-GAC catalyst regeneration. This task focuses on developing chemical and biochemical approaches for the Fe-GAC catalyst recycling or regeneration.
This study aims to develop a Fenton procedure and heterogeneous catalyst (Fe-GAC) for Fenton-like reaction that could facilitate the destruction of THM precursors. Five tasks will be accomplished following the specified procedures to demonstrate that hydroxyl radical (?OH), generated from Fenton and Fenton-like reactions, could be used as a strong reactant for DOC mitigation and THM control.Tasks i) Identifying optimal conditions for the formation hydroxyl radicals and degradation THM precursors by Fenton process. This task is to systematically assess the factors that affect the formation of hydroxyl radicals in Fenton process under the conditions relevant to drinking water treatment process. Production of hydroxyl radicals will be quantified by the established procedures in literature (Setsukinai et al., 2003; Cohn et al., 2004, 2006; Zhang and Lemley, 2006).The task involves the selection of appropriate treatment conditions that are most effective in THM precursor destruction. The key parameters that will be quantified include pH (5-8), the concentrations of ferrous iron and H2O2 (5-100 mg/L), and the concentration of DOC (2-30 mg/L). Batch kinetic experiments will be carried out in 300-mL flask at ambient temperature in dark. The reaction kinetics will be formulated with appropriate mathematical model.In addition, DOC speciation will be carried out following standard procedures. Each group of DOC will be tested for THM formation potential before and after treatment. THMs will be analyzed by purge and trap gas chromatographic/mass spectrometric method (US EPA method 524.2) after the chlorination of the water sample. The chlorination of the water samples follows a modified Uniform Formation Conditions (UFC) procedure: a) transfer 5.00 mL of the buffered water sample and 35.0 mL buffered DI water (pH 8.0) to the 40 mL incubation vial; b) dose with combined hypochlorite (buffer solution at pH 8.0), cap the incubation vial and invert several times; c) incubate the water at 25ºC in dark for 24 hr. Varian Saturn GC/MS 2000 with a DB-5MS column (J& W Scientific column, I.D 0.25 mm and 60m in length) will be applied for the determination of THMs. The flow rate of the helium carrier gas is set to 1.0 mL/min at 35°C, with inject split ratio of 10 and injector temperature 125°C. Column oven initial temperature is set at 35°C, and then increase to 50°C at 10°C/min and then to 200 at 20°C/min.Task ii) Developing Fe-GAC catalysts with optimal surface characteristics for THM precursor destruction at circumneutral pH.In this task, we will specify the conditions for the preparation of high efficient heterogeneous Fenton catalyst. A variety of Fe-GAC catalysts will be prepared from different oxidative treatments. The preparation will begin by treating GAC sample with Fe(II) at increasing concentrations. Each system will then undergo oxidation under different conditions, yielding a series of iron-impregnated catalysts. The prepared Fe-GAC catalyst will be characterized in terms of Fe content and distribution on GAC, iron crystal structure, surface acidic/basic properties, and specific surface area.Specifically, 2.0 g GAC is added to 200 mL of 0.10 M FeSO4 solution in a 300-mL glass flask, followed by the addition of 10 mL of 1.0 M H2O2 at ambient temperature. The flask is placed on an orbit shaker (Lab-line Instruments Inc.) at 120 rpm to avoid the settlement of the GAC. The pH of the solution is controlled at < 3.5 to prevent Fe(OH)3 precipitation. After 6 hr, the GAC impregnated with Fe(III) is taken out of the flask and washed with Millipore water several times. The catalyst is then dried at 80 °C for 12 hr in oven and 300°C for 2 hr in furnace. The catalysts could be further modified by other Lewis acids such as aluminum chloride to promote iron redox oscillation. To measure the iron content on Fe-GAC, 0.100±0.002 g of Fe-GAC sample is mixed with 30.0 mL of 1:1 HCl, followed by shaking (120 rpm) at ambient temperature for 6 h and then heating in a water bath at 90 ºC for 60 min (Lu, 1995). The supernatant is collected by filtration and the total iron is analyzed by 1,10-phenanthroline spectrophotometric method (APHA, 1989). The crystal structure of iron on Fe-GAC is determined by X-ray diffraction (XRD) analysis. The analysis was conducted with the MiniFlex automated, microprocessor controlled X-ray powder diffractometer, with Cu Kα X-ray source and semiconductor detector, operated at 15 mA and 30 kV.Tasks iii) Identifying major parameters affecting THM precursor destruction in Fenton-like process and Developing proper strategies for Fe-GAC catalyst regeneration. The prepared heterogeneous Fenton catalysts will be assessed for their capability of promoting hydroxyl radical generation from H2O2 at circumneutral pH. The tests will be conducted in stirred batch reactors with water samples collected from Missouri River. Many communities along the Missouri River use the river water as their drinking water supplies. We will evaluate how the major water quality parameters and treatment process could affect THM formation, including water pH, hardness, DOC, dissolved iron in the source water, Fe(III) content on GAC, H2O2 concentration applied, and temperature.A typical kinetic run starts from adding 0.100 g of Fe-GAC to 300 mL glass flask, then transferring 200.0 mL water sample. The flask is covered with aluminum foil to avoid the interference from the room light. After adjusting pH to the desired values with HCl or NaOH, certain amount of H2O2 is spiked at zero time point to initiate the reaction, while Fe-GAC is kept off-bottom with a magnetic stirrer. At fixed time points, 2.0 mL aliquot is withdrawn and filtered through 0.45 mM syringe filter (Fisher Scientific). The fluorescence intensity of filtrate is collected afterwards. All fluorescence measurements will be performed on the Hitachi F-4500 Spectrograph (Hitachi Co.). Samples are held in a standard 1-cm quartz cuvette and the lamp voltage is kept constant at 700 V for all experiments. Fluorescence spectra are collected as EEMS by scanning emission spectra at a range of excitation wavelengths, in which emission spectra are gathered from 250 nm to 550 nm in 3 nm steps, whereas the excitation wavelengths are stepped in 2 nm from 200 nm to 400 nm. The fluorescence scans are performed at a constant room temperature of 23±2°C. The fluorescence intensity is normalized to the water Raman scatter at excitation 248-252 nm/emission 267-273 nm. Selected samples will also be tested for THM formation potentials following the same method as Task ii). In this task, we will evaluate strategies for the recycling and regeneration of used Fe-GAC catalysts and develop a bench-scale pilot treatment system. Eliminating the generation of iron (hydro)oxides sludge in the treatment process could dramatically lower the overall treatment cost, making the process more competitive.