Bio


Bill Mitch received a B.A. in Anthropology (Archaeology) from Harvard University in 1993. During his studies, he excavated at Mayan sites in Belize and surveyed sites dating from 2,000 B.C. in Louisiana. He switched fields by receiving a M.S. degree in Civil and Environmental Engineering at UC Berkeley. He worked for 3 years in environmental consulting, receiving his P.E. license in Civil Engineering in California. Returning to UC Berkeley in 2000, he received his PhD in Civil and Environmental Engineering in 2003. He moved to Yale as an assistant professor after graduation. His dissertation received the AEESP Outstanding Doctoral Dissertation Award in 2004. At Yale, he serves as the faculty advisor for the Yale Student Chapter of Engineers without Borders. In 2007, he won a NSF CAREER Award. He moved to Stanford University as an associate professor in 2013.

Employing a fundamental understanding of organic chemical reaction pathways, his research explores links between public health, engineering and sustainability. Topics of current interest include:

Public Health and Emerging Carcinogens: Recent changes to the disinfection processes fundamental to drinking and recreational water safety are creating a host of highly toxic byproducts linked to bladder cancer. We seek to understand how these compounds form so we can adjust the disinfection process to prevent their formation.

Global Warming and Oceanography: Oceanic dissolved organic matter is an important global carbon component, and has important impacts on the net flux of CO2 between the ocean and atmosphere. We seek to understand some of the important abiotic chemical reaction pathways responsible for carbon turnover.

Sustainability and Persistant Organic Pollutants (POPs): While PCBs have been banned in the US, we continue to produce a host of structurally similar chemicals. We seem to understand important chemical pathways responsible for POP destruction in the environment, so we can design less persistent and problematic chemicals in the future.

Engineering for Sustainable Wastewater Recycling: The shortage of clean water represents a critical challenge for the next century, and has necessitated the recycling of wastewater. We seek to understand ways of engineer this process in ways to minimize harmful byproduct formation.

Carbon Sequestration: We are evaluating the formation of nitrosamine and nitraminecarcinogens from amine-based carbon capture, as well as techniques to destroy any of these byproducts that form.

Academic Appointments


  • Professor, Civil and Environmental Engineering

Honors & Awards


  • Excellence in Review Award, Environmental Science and Technology (2013)
  • Elected Vice-Chair of the 4th Disinfection Byproducts Gordon Conference in 2015, Disinfection Byproducts Gordon Conference (2015)
  • Invited speaker for the 3rd Disinfection Byproducts Gordon Conference, Mt. Holyoke College, Disinfection Byproducts Gordon Conference (2012)
  • Environmental Science and Technology Editors Choice Award Best Paper 3rd runner up, Environmental Science and Technology (2010)
  • Top 10 most-accessed articles, 2nd Quarter, Environmental Science and Technology (2010)
  • Invited speaker, Environmental Sciences Water Gordon Conference (2010)
  • Member, US EPA Scientific Advisory Board Drinking Water Committee (2010)
  • Invited speaker, Disinfection Byproducts Gordon Conference, Mt. Holyoke College (2009)
  • CAREER Award, NSF (2007)
  • Advisor of recipient, ACS Environmental Chemistry Graduate Student Award (2007)
  • Invited speaker, Disinfection Byproducts Gordon Conference, Mt. Holyoke College (2006)
  • Certificate of Merit, 230th ACS National Meeting (2005)
  • Arthur Greer Memorial Prize for teaching and research excellence by a junior faculty member, Yale University (2005)
  • Outstanding Doctoral Dissertation Award, Association of Environmental Engineering and Science Professors and Parsons Engineering (2004)
  • Graduated Summa Cum Laude and elected into the Phi Beta Kappa Academic Honor Society, Harvard University (1993)

Professional Education


  • B.A., Harvard University (Summa Cum Laude), Anthropology (Archaeology) (1993)
  • M.S., University of California, Berkeley, Civil and Environmental Engineering (1996)
  • Ph.D., University of California, Berkeley, Civil and Environmental Engineering (2003)

2018-19 Courses


Stanford Advisees


All Publications


  • N-nitrosamine, halogenated disinfection byproduct, and byproduct precursor control in UV/free chlorine and UV/H2O2 treatment trains: A parallel comparison in a pilot plant Chuang, Y., Szczuka, A., Mitch, W. AMER CHEMICAL SOC. 2018
  • Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS Nelson, K. L., Boehm, A. B., Davies-Colley, R. J., Dodd, M. C., Kohn, T., Linden, K. G., Liu, Y., Maraccini, P. A., McNeill, K., Mitch, W. A., Nguyen, T. H., Parker, K. M., Rodriguez, R. A., Sassoubre, L. M., Silverman, A. I., Wigginton, K. R., Zepp, R. G. 2018; 20 (8): 1089–1122

    Abstract

    Health-relevant microorganisms present in natural surface waters and engineered treatment systems that are exposed to sunlight can be inactivated by a complex set of interacting mechanisms. The net impact of sunlight depends on the solar spectral irradiance, the susceptibility of the specific microorganism to each mechanism, and the water quality; inactivation rates can vary by orders of magnitude depending on the organism and environmental conditions. Natural organic matter (NOM) has a large influence, as it can attenuate radiation and thus decrease inactivation by endogenous mechanisms. Simultaneously NOM sensitizes the formation of reactive intermediates that can damage microorganisms via exogenous mechanisms. To accurately predict inactivation and design engineered systems that enhance solar inactivation, it is necessary to model these processes, although some details are not yet sufficiently well understood. In this critical review, we summarize the photo-physics, -chemistry, and -biology that underpin sunlight-mediated inactivation, as well as the targets of damage and cellular responses to sunlight exposure. Viruses that are not susceptible to exogenous inactivation are only inactivated if UVB wavelengths (280-320 nm) are present, such as in very clear, open waters or in containers that are transparent to UVB. Bacteria are susceptible to slightly longer wavelengths. Some viruses and bacteria (especially Gram-positive) are susceptible to exogenous inactivation, which can be initiated by visible as well as UV wavelengths. We review approaches to model sunlight-mediated inactivation and illustrate how the environmental conditions can dramatically shift the inactivation rate of organisms. The implications of this mechanistic understanding of solar inactivation are discussed for a range of applications, including recreational water quality, natural treatment systems, solar disinfection of drinking water (SODIS), and enhanced inactivation via the use of sensitizers and photocatalysts. Finally, priorities for future research are identified that will further our understanding of the key role that sunlight disinfection plays in natural systems and the potential to enhance this process in engineered systems.

    View details for DOI 10.1039/c8em00047f

    View details for Web of Science ID 000441765000001

    View details for PubMedID 30047962

  • Distributed Chlorine Injection To Minimize NDMA Formation during Chloramination of Wastewater ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS Furst, K. E., Pecson, B. M., Webber, B. D., Mitch, W. A. 2018; 5 (7): 462–66
  • Tradeoffs between pathogen inactivation and disinfection byproduct formation during sequential chlorine and chloramine disinfection for wastewater reuse. Water research Furst, K. E., Pecson, B. M., Webber, B. D., Mitch, W. A. 2018; 143: 579–88

    Abstract

    Treatment of fully nitrified municipal wastewater effluents with chlorine followed by chloramines (i.e., sequential chlorine disinfection) upstream of advanced treatment trains can contribute pathogen inactivation credits for potable reuse while leaving a chloramine residual to control biofouling on membrane units in the advanced treatment train. However, free chlorine exposures must be optimized to maximize pathogen inactivation while minimizing the formation of disinfection byproducts (DBPs) that are challenging to remove in the advanced treatment train. Using a pilot-scale disinfection contactor receiving fully-nitrified, tertiary municipal wastewater effluent, this study found that a 3 mg * min/L free chlorine CT (i.e., the product of the chlorine residual "C" and the contact time "T") followed by a 140 mg * min/L chloramine CT could reliably achieve 5-log inactivation of MS2 bacteriophage and reduce median total coliform concentrations below 2.2 MPN/100 mL. Free chlorine disinfection was equally effective when chlorine was dosed to exceed the breakpoint for 1 mg/L of ammonia as N. At this free chlorine exposure, regulated trihalomethane (THM) and haloacetic acid (HAA) formation remained below their Maximum Contaminant Levels (MCLs), but NDMA concentrations of 30 ng/L were above the 10 ng/L California Notification Level. Increasing the free chlorine exposure to 30 mg * min/L increased THM and HAA formation, with regulated THMs approaching or exceeding the MCL. Although this free chlorine exposure prevented NDMA formation during chloramination, the 10 ng/L background NDMA formation in the tertiary effluent remained. Increasing the free chlorine exposure also increased the formation of unregulated halogenated DBP classes that may be significant contributors to the DBP-associated toxicity of the disinfected wastewater. The results indicate that sequential chlorination can be used to optimize the benefits of free chlorine (virus and NDMA control) and chloramine disinfection (THM, HAA, and coliform control).

    View details for DOI 10.1016/j.watres.2018.05.050

    View details for PubMedID 30015098

  • Chlorotyrosines versus volatile byproducts from disinfection during washing of lettuce and spinach Mitch, W., Komaki, Y., Simpson, A. AMER CHEMICAL SOC. 2018
  • Halogen radicals promote the photodegradation of microcystins in estuarine systems Mitch, W., Parker, K., Ghadouani, A., Reichwaldt, E. AMER CHEMICAL SOC. 2018
  • When ROS are not ROS: The effect of salts on the degradation of protein Mitch, W., Komaki, Y., Choe, J. AMER CHEMICAL SOC. 2018
  • Drinking Water Disinfection Byproducts (DBPs) and Human Health Effects: Multidisciplinary Challenges and Opportunities ENVIRONMENTAL SCIENCE & TECHNOLOGY Li, X., Mitch, W. A. 2018; 52 (4): 1681–89

    Abstract

    While drinking water disinfection has effectively prevented waterborne diseases, an unintended consequence is the generation of disinfection byproducts (DBPs). Epidemiological studies have consistently observed an association between consumption of chlorinated drinking water with an increased risk of bladder cancer. Out of the >600 DBPs identified, regulations focus on a few classes, such as trihalomethanes (THMs), whose concentrations were hypothesized to correlate with the DBPs driving the toxicity of disinfected waters. However, the DBPs responsible for the bladder cancer association remain unclear. Utilities are switching away from a reliance on chlorination of pristine drinking water supplies to the application of new disinfectant combinations to waters impaired by wastewater effluents and algal blooms. In light of these changes in disinfection practice, this article discusses new approaches being taken by analytical chemists, engineers, toxicologists and epidemiologists to characterize the DBP classes driving disinfected water toxicity, and suggests that DBP exposure should be measured using other DBP classes in addition to THMs.

    View details for DOI 10.1021/acs.est.7b05440

    View details for Web of Science ID 000426143300001

    View details for PubMedID 29283253

  • Capture and Reductive Transformation of Halogenated Pesticides by an Activated Carbon-Based Electrolysis System for Treatment of Runoff ENVIRONMENTAL SCIENCE & TECHNOLOGY Li, Y., Mitch, W. A. 2018; 52 (3): 1435–43

    Abstract

    This study evaluates an electrochemical system to treat the halogenated pesticides, fipronil, permethrin, and bifenthrin, in urban runoff. Compared to the poor sorption capacity of metal-based electrodes, granular activated carbon (GAC)-based electrodes could sorb halogenated pesticides, permitting electrochemical degradation to occur over longer timescales than reactor hydraulic residence times. In a dual-cell configuration, a cathode constructed of loose GAC containing sorbed pesticides was separated from the anode by an ion-exchange membrane to prevent chloride transport and oxidation to chlorine at the anode. When -1 V was applied to the cathode, fipronil concentrations declined by 92% over 15 h, releasing molar equivalents of chloride (2) and fluoride (6), suggesting complete dehalogenation of fipronil. An electrode constructed of crushed GAC particles attached to a carbon cloth current distributor achieved >90% degradation of fipronil, permethrin, and bifenthrin within 2 h under the same conditions. To evaluate a simpler single-cell configuration suitable for scale-up, two of the carbon cloth-based electrodes were placed in parallel without an ion-exchange membrane. For -1 V applied to the cathode, fipronil degradation was >95% over 2 h, and energy consumption declined with closer electrode spacing. However, chloride oxidation at the anode produced chlorine, and the anode degraded. Application of an alternating potential (-1 to +1 V at 0.0125 Hz) to the parallel-plate electrodes achieved >90% degradation of fipronil, bifenthrin, and permethrin over 4 h, releasing chloride at 50-70% of that expected for complete dechlorination. No loss of performance or formation of chlorine or halogenated byproducts was observed over 5 cycles of treating fipronil-spiked surface water.

    View details for DOI 10.1021/acs.est.7b05259

    View details for Web of Science ID 000424851700057

    View details for PubMedID 29281267

  • Comparing the UV/Monochloramine and UV/Free Chlorine Advanced Oxidation Processes (AOPs) to the UV/Hydrogen Peroxide AOP Under Scenarios Relevant to Potable Reuse ENVIRONMENTAL SCIENCE & TECHNOLOGY Chuang, Y., Chen, S., Chinn, C. J., Mitch, W. A. 2017; 51 (23): 13859–68
  • New Takes on Emerging Contaminants: Preface JOURNAL OF ENVIRONMENTAL SCIENCES Mitch, W. A. 2017; 62: 1–2

    View details for DOI 10.1016/j.jes.2017.12.005

    View details for Web of Science ID 000418892300001

    View details for PubMedID 29289280

  • Nitrosamines and Nitramines in Amine-Based Carbon Dioxide Capture Systems: Fundamentals, Engineering Implications, and Knowledge Gaps ENVIRONMENTAL SCIENCE & TECHNOLOGY Yu, K., Mitch, W. A., Dai, N. 2017; 51 (20): 11522–36

    Abstract

    Amine-based absorption is the primary contender for postcombustion CO2 capture from fossil fuel-fired power plants. However, significant concerns have arisen regarding the formation and emission of toxic nitrosamine and nitramine byproducts from amine-based systems. This paper reviews the current knowledge regarding these byproducts in CO2 capture systems. In the absorber, flue gas NOx drives nitrosamine and nitramine formation after its dissolution into the amine solvent. The reaction mechanisms are reviewed based on CO2 capture literature as well as biological and atmospheric chemistry studies. In the desorber, nitrosamines are formed under high temperatures by amines reacting with nitrite (a hydrolysis product of NOx), but they can also thermally decompose following pseudo-first order kinetics. The effects of amine structure, primarily amine order, on nitrosamine formation and the corresponding mechanisms are discussed. Washwater units, although intended to control emissions from the absorber, can contribute to additional nitrosamine formation when accumulated amines react with residual NOx. Nitramines are much less studied than nitrosamines in CO2 capture systems. Mitigation strategies based on the reaction mechanisms in each unit of the CO2 capture systems are reviewed. Lastly, we highlight research needs in clarifying reaction mechanisms, developing analytical methods for both liquid and gas phases, and integrating different units to quantitatively predict the accumulation and emission of nitrosamines and nitramines.

    View details for DOI 10.1021/acs.est.7b02597

    View details for Web of Science ID 000413391800007

    View details for PubMedID 28946738

  • Regulated and unregulated halogenated disinfection byproduct formation from chlorination of saline groundwater WATER RESEARCH Szczuka, A., Parker, K. M., Harvey, C., Hayes, E., Vengosh, A., Mitch, W. A. 2017; 122: 633–44

    Abstract

    Coastal utilities exploiting mildly saline groundwater (<150 mg/L chloride) may be challenged by disinfection byproduct (DBP) formation, a concern likely to increase with sea-level rise. Groundwater from North Carolina coastal aquifers is characterized by large variations in concentrations of halides (bromide up to 10,600 μg/L) and dissolved organic carbon (up to 5.7 mg-C/L). Formation of 33 regulated and unregulated halogenated DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles, haloacetamides, and haloacetaldehydes, was measured after simulated chlorination of 24 coastal North Carolina groundwater samples under typical chlorination conditions. Results of chlorination simulation show that THM levels exceeded the Primary Maximum Contaminant Levels in half of the chlorinated samples. Addition of halides to a low salinity groundwater (110 mg/L chloride) indicated that elevated bromide triggered DBP formation, but chloride was not a critical factor for their formation. DBP speciation, but not overall molar formation, was strongly correlated with bromide variations in the groundwater. THMs and HAAs dominated the measured halogenated DBPs on a mass concentration basis. When measured concentrations were weighted by metrics of toxic potency, haloacetonitriles, and to a lesser degree, haloacetaldehydes and HAAs, were the predominant contributors to calculated DBP-associated toxicity. For some samples exhibiting elevated ammonia concentrations, the addition of chlorine to form chloramines in situ significantly reduced halogenated DBP concentrations and calculated toxicity. HAAs dominated the calculated toxicity of chloraminated waters. Reverse osmosis treatment of saline groundwater (chloride >250 mg/L) can reduce DBP formation by removing halides and organic precursors. However, we show that in a case where reverse osmosis permeate is blended with a separate raw groundwater, the residual bromide level in the permeate could still exceed that in the raw groundwater, and thereby induce DBP formation in the blend. DBP-associated calculated toxicity increased for certain blends in this system due to the DBPs resulting from the combination of the elevated bromide concentration in the permeate and the organic precursors from the raw coastal groundwater.

    View details for DOI 10.1016/j.watres.2017.06.028

    View details for Web of Science ID 000407404300062

    View details for PubMedID 28646800

  • Reverse Osmosis Shifts Chloramine Speciation Causing Re-Formation of NDMA during Potable Reuse of Wastewater ENVIRONMENTAL SCIENCE & TECHNOLOGY McCurry, D. L., Ishida, K. P., Oelker, G. L., Mitch, W. A. 2017; 51 (15): 8589–96

    Abstract

    UV-based advanced oxidation processes (AOPs) effectively degrade N-nitrosodimethylamine (NDMA) passing through reverse osmosis (RO) units within advanced treatment trains for the potable reuse of municipal wastewater. However, certain utilities have observed the re-formation of NDMA after the AOP from reactions between residual chloramines and NDMA precursors in the AOP product water. Using kinetic modeling and bench-scale RO experiments, we demonstrate that the low pH in the RO permeate (∼5.5) coupled with the effective rejection of NH4+ promotes conversion of the residual monochloramine (NH2Cl) in the permeate to dichloramine (NHCl2) via the reaction: 2 NH2Cl + H+ ↔ NHCl2 + NH4+. Dichloramine is the chloramine species known to react with NDMA precursors to form NDMA. After UV/AOP, utilities generally use lime or other techniques to increase the pH of the finished water to prevent distribution system corrosion. Modeling indicated that, while the increase in pH halts dichloramine formation, it converts amine-based NDMA precursors to their more reactive, neutral forms. With modeling, and experiments at both bench-scale and field-scale, we demonstrate that reducing the time interval between RO treatment and final pH adjustment can significantly reduce NDMA re-formation by minimizing the amount of dichloramine formed prior to reaching the final target pH.

    View details for DOI 10.1021/acs.est.7b01641

    View details for Web of Science ID 000406982600042

    View details for PubMedID 28671841

  • Effect of Ozonation and Biological Activated Carbon Treatment of Wastewater Effluents on Formation of N-nitrosamines and Halogenated Disinfection Byproducts. Environmental science & technology Chuang, Y., Mitch, W. A. 2017; 51 (4): 2329-2338

    Abstract

    Ozonation followed by biological activated carbon (O3/BAC) is being considered as a key component of reverse osmosis-free advanced treatment trains for potable wastewater reuse. Using a laboratory-scale O3/BAC system treating two nitrified wastewater effluents, this study characterized the effect of different ozone dosages (0-1.0 mg O3/mg dissolved organic carbon) and BAC empty bed contact times (EBCT; 15-60 min) on the formation after chlorination or chloramination of 35 regulated and unregulated halogenated disinfection byproducts (DBPs), 8 N-nitrosamines, and bromate. DBP concentrations were remarkably similar between the two wastewaters across O3/BAC conditions. Ozonation increased bromate, TCNM, and N-nitrosodimethylamine, but ozonation was less significant for other DBPs. DBP formation generally decreased significantly with BAC treatment at 15 min EBCT, but little further reduction was observed at higher EBCT where low dissolved oxygen concentrations may have limited biological activity. The O3/BAC-treated wastewaters met regulatory levels for trihalomethanes (THMs), haloacetic acids (HAAs), and bromate, although N-nitrosodimethylamine exceeded the California Notification Level in one case. Regulated THMs and HAAs dominated by mass. When DBP concentrations were weighted by measures of their toxic potencies, unregulated haloacetonitriles, haloacetaldehydes, and haloacetamides dominated. Assuming toxicity is additive, the calculated DBP-associated toxicity of the O3/BAC-treated chloraminated effluents were comparable or slightly higher than those calculated in a recent evaluation of Full Advanced Treatment trains incorporating reverse osmosis.

    View details for DOI 10.1021/acs.est.6b04693

    View details for PubMedID 28092936

  • Relative Importance of Different Water Categories as Sources of N-Nitrosamine Precursors ENVIRONMENTAL SCIENCE & TECHNOLOGY Zeng, T., Glover, C. M., Marti, E. J., Woods-Chabane, G. C., Karanfil, T., Mitch, W. A., Dickenson, E. R. 2016; 50 (24): 13239-13248

    Abstract

    A comparison of loadings of N-nitrosamines and their precursors from different source water categories is needed to design effective source water blending strategies. Previous research using Formation Potential (FP) chloramination protocols (high dose and prolonged contact times) raised concerns about precursor loadings from various source water categories, but differences in the protocols employed rendered comparisons difficult. In this study, we applied Uniform Formation Condition (UFC) chloramination and ozonation protocols mimicking typical disinfection practice to compare loadings of ambient specific and total N-nitrosamines as well as chloramine-reactive and ozone-reactive precursors in 47 samples, including 6 pristine headwaters, 16 eutrophic waters, 4 agricultural runoff samples, 9 stormwater runoff samples, and 12 municipal wastewater effluents. N-Nitrosodimethylamine (NDMA) formation from UFC and FP chloramination protocols did not correlate, with NDMA FP often being significant in samples where no NDMA formed under UFC conditions. N-Nitrosamines and their precursors were negligible in pristine headwaters. Conventional, and to a lesser degree, nutrient removal wastewater effluents were the dominant source of NDMA and its chloramine- and ozone-reactive precursors. While wastewater effluents were dominant sources of TONO and their precursors, algal blooms, and to a lesser degree agricultural or stormwater runoff, could be important where they affect a major fraction of the water supply.

    View details for DOI 10.1021/acs.est.6b04650

    View details for Web of Science ID 000390620900009

    View details for PubMedID 27993049

  • Development of an Activated Carbon-Based Electrode for the Capture and Rapid Electrolytic Reductive Debromination of Methyl Bromide from Postharvest Fumigations. Environmental science & technology Li, Y., Liu, C., Cui, Y., Walse, S. S., Olver, R., Zilberman, D., Mitch, W. A. 2016; 50 (20): 11200-11208

    Abstract

    Due to concerns surrounding its ozone depletion potential, there is a need for technologies to capture and destroy methyl bromide (CH3Br) emissions from postharvest fumigations applied to control agricultural pests. Previously, we described a system in which CH3Br fumes vented from fumigation chambers could be captured by granular activated carbon (GAC). The GAC was converted to a cathode by submergence in a high ionic strength solution and connection to the electrical grid, resulting in reductive debromination of the sorbed CH3Br. The GAC bed was drained and dried for reuse to capture and destroy CH3Br fumes from the next fumigation. However, the loose GAC particles and slow kinetics of this primitive electrode necessitated improvements. Here, we report the development of a cathode containing a thin layer of small GAC particles coating carbon cloth as a current distributor. Combining the high sorption potential of GAC for CH3Br with the conductivity of the carbon cloth current distributor, the cathode significantly lowered the total cell resistance and achieved 96% reductive debromination of CH3Br sorbed at 30% by weight to the GAC within 15 h at -1 V applied potential vs standard hydrogen electrode, a time scale and efficiency suitable for postharvest fumigations. The cathode exhibited stable performance over 50 CH3Br capture and destruction cycles. Initial cost estimates indicate that this technique could treat CH3Br fumes at ∼$5/kg, roughly one-third of the cost of current alternatives.

    View details for PubMedID 27611209

  • Development of Predictive Models for the Degradation of Halogenated Disinfection Byproducts during the UV/H2O2 Advanced Oxidation Process ENVIRONMENTAL SCIENCE & TECHNOLOGY Chuang, Y., Parker, K. M., Mitch, W. A. 2016; 50 (20): 11209-11217
  • N-Nitrosamines and halogenated disinfection byproducts in U.S. Full Advanced Treatment trains for potable reuse. Water research Zeng, T., Plewa, M. J., Mitch, W. A. 2016; 101: 176-186

    Abstract

    Water utilities are increasingly considering indirect and direct potable reuse of municipal wastewater effluents. Disinfection byproducts (DBPs), particularly N-nitrosamines, are key contaminants of potential health concern for potable reuse. This study quantified the concentrations of N-nitrosamines and a suite of regulated and unregulated halogenated DBPs across five U.S. potable reuse Full Advanced Treatment trains incorporating microfiltration, reverse osmosis, and UV-based advanced oxidation. Low μg/L concentrations of trihalomethanes, haloacetic acids, dichloroacetonitrile, and dichloroacetamide were detected in the secondary or tertiary wastewater effluents serving as influents to potable reuse treatment trains, while the concentrations of N-nitrosamines were more variable (e.g., <2-320 ng/L for N-nitrosodimethylamine). Ozonation promoted the formation of N-nitrosamines, haloacetaldehydes, and haloacetamides, but biological activated carbon effectively reduced concentrations of these DBPs. Application of chloramines upstream of microfiltration for biofouling control increased DBP concentrations to their highest levels observed along the treatment trains. Reverse osmosis rejected DBPs to varying degrees, ranging from low for some (e.g., N-nitrosamines, trihalomethanes, and haloacetonitriles) to high for other DBPs. UV-based advanced oxidation eliminated N-nitrosamines, but only partially removed halogenated DBPs. Chloramination of the treatment train product waters under simulated distribution system conditions formed additional DBPs, with concentrations often equaling or exceeding those in the treatment train influents. Overall, the concentration profiles of DBPs were fairly consistent within individual treatment trains for sampling campaigns separated by months and across different treatment trains for the same sampling time window. Weighting DBP concentrations by their toxic potencies highlighted the potential significance of haloacetonitriles, which were not effectively removed by reverse osmosis and advanced oxidation, to the DBP-associated toxicity in potable reuse waters.

    View details for DOI 10.1016/j.watres.2016.03.062

    View details for PubMedID 27262122

  • Halogen Radicals Promote the Photodegradation of Microcystins in Estuarine Systems. Environmental science & technology Parker, K. M., Reichwaldt, E. S., Ghadouani, A., Mitch, W. A. 2016; 50 (16): 8505-8513

    Abstract

    The transport of microcystin, a hepatotoxin produced by cyanobacteria (e.g., Microcystis aeruginosa), to estuaries can adversely affect estuarine and coastal ecosystems. We evaluated whether halogen radicals (i.e., reactive halogen species (RHS)) could significantly contribute to microcystin photodegradation during transport within estuaries. Experiments in synthetic and natural water samples demonstrated that the presence of seawater halides increased quantum yields for microcystin indirect photodegradation by factors of 3-6. Additional experiments indicated that photoproduced RHS were responsible for this effect. Despite the fact that dissolved organic matter (DOM) concentrations decreased in more saline waters, the calculated photochemical half-life of microcystin decreased 6-fold with increasing salinity along a freshwater-estuarine transect due to the halide-associated increase in quantum yield. Modeling of microcystin photodegradation along this transect indicated that the time scale for RHS-mediated microcystin photodegradation is comparable to the time scale of transport. Microcystin concentrations decline by ∼98% along the transect when considering photodegradation by RHS, but only by ∼54% if this pathway were ignored. These results suggest the importance of considering RHS-mediated photodegradation in future models of microcystin fate in freshwater-estuarine systems.

    View details for DOI 10.1021/acs.est.6b01801

    View details for PubMedID 27447196

  • Environmental and personal determinants of the uptake of disinfection by-products during swimming ENVIRONMENTAL RESEARCH Font-Ribera, L., Kogevinas, M., Schmalz, C., Zwiener, C., Marco, E., Grimalt, J. O., Liu, J., Zhang, X., Mitch, W., Critelli, R., Naccarati, A., Heederik, D., Spithoven, J., Arjona, L., de Bont, J., Gracia-Lavedan, E., Villanueva, C. M. 2016; 149: 206-215

    Abstract

    Trihalomethanes (THMs) in exhaled breath and trichloroacetic acid (TCAA) in urine are internal dose biomarkers of exposure to disinfection by-products (DBPs) in swimming pools.We assessed how these biomarkers reflect the levels of a battery of DBPs in pool water and trichloramine in air, and evaluated personal determinants.A total of 116 adults swam during 40min in a chlorinated indoor pool. We measured chloroform, bromodichloromethane, dibromochloromethane and bromoform in exhaled breath and TCAA in urine before and after swimming, trichloramine in air and several DBPs in water. Personal determinants included sex, age, body mass index (BMI), distance swum, energy expenditure, heart rate and 12 polymorphisms in GSTT1, GSTZ1 and CYP2E1 genes.Median level of exhaled total THMs and creatinine adjusted urine TCAA increased from 0.5 to 14.4µg/m(3) and from 2.5 to 5.8µmol/mol after swimming, respectively. The increase in exhaled brominated THMs was correlated with brominated THMs, haloacetic acids, haloacetonitriles, haloketones, chloramines, total organic carbon and total organic halogen in water and trichloramine in air. Such correlations were not detected for exhaled chloroform, total THMs or urine TCAA. Exhaled THM increased more in men, urine TCAA increased more in women, and both were affected by exercise intensity. Genetic variants were associated with differential increases in exposure biomarkers.Our findings suggest that, although affected by sex, physical activity and polymorphisms in key metabolizing enzymes, brominated THMs in exhaled breath could be used as a non-invasive DBP exposure biomarker in swimming pools with bromide-containing source waters. This warrants confirmation with new studies.

    View details for DOI 10.1016/j.envres.2016.05.013

    View details for Web of Science ID 000378366000023

    View details for PubMedID 27214136

  • Reductive dehalogenation of disinfection byproducts by an activated carbon-based electrode system WATER RESEARCH Li, Y., Kemper, J. M., Datuin, G., Akey, A., Mitch, W. A., Luthy, R. G. 2016; 98: 354-362

    Abstract

    Low molecular weight, uncharged, halogenated disinfection byproducts (DBPs) are poorly removed by the reverse osmosis and advanced oxidation process treatment units often applied for further treatment of municipal wastewater for potable reuse. Granular activated carbon (GAC) treatment effectively sorbed 22 halogenated DBPs. Conversion of the GAC to a cathode within an electrolysis cell resulted in significant degradation of the 22 halogenated DBPs by reductive electrolysis at -1 V vs. Standard Hydrogen Electrode (SHE). The lowest removal efficiency over 6 h electrolysis was for trichloromethane (chloroform; 47%) but removal efficiencies were >90% for 13 of the 22 DBPs. In all cases, DBP degradation was higher than in electrolysis-free controls, and degradation was verified by the production of halides as reduction products. Activated carbons and charcoal were more effective than graphite for electrolysis, with graphite featuring poor sorption for the DBPs. A subset of halogenated DBPs (e.g., haloacetonitriles, chloropicrin) were degraded upon sorption to the GAC, even without electrolysis. Using chloropicrin as a model, experiments indicated that this loss was attributable to the partial reduction of sorbed chloropicrin from reducing equivalents in the GAC. Reducing equivalents depleted by these reactions could be restored when the GAC was treated by reductive electrolysis. GAC treatment of an advanced treatment train effluent for potable reuse effectively reduced the concentrations of chloroform, bromodichloromethane and dichloroacetonitrile measured in the column influent to below the method detection limits. Treatment of the GAC by reductive electrolysis at -1 V vs. SHE over 12 h resulted in significant degradation of the chloroform (63%), bromodichloromethane (96%) and dichloroacetonitrile (99%) accumulated on the GAC. The results suggest that DBPs in advanced treatment train effluents could be captured and degraded continuously by reductive electrolysis using a GAC-based cathode.

    View details for DOI 10.1016/j.watres.2016.04.019

    View details for Web of Science ID 000376805500039

    View details for PubMedID 27124125

  • Oral intake of ranitidine increases urinary excretion of N-nitrosodimethylamine CARCINOGENESIS Zeng, T., Mitch, W. A. 2016; 37 (6): 625-634

    Abstract

    The H2-receptor antagonist, ranitidine, is among the most widely used pharmaceuticals to treat gastroesophageal reflux disease and peptic ulcers. While previous studies have demonstrated that amines can form N-nitrosamines when exposed to nitrite at stomach-relevant pH, N-nitrosamine formation from ranitidine, an amine-based pharmaceutical, has not been demonstrated under these conditions. In this work, we confirmed the production of N-nitrosodimethylamine (NDMA), a potent carcinogen, by nitrosation of ranitidine under stomach-relevant pH conditions in vitro We also evaluated the urinary NDMA excretion attributable to ingestion of clinically used ranitidine doses. Urine samples collected from five female and five male, healthy adult volunteers over 24-h periods before and after consumption of 150mg ranitidine were analyzed for residual ranitidine, ranitidine metabolites, NDMA, total N-nitrosamines and dimethylamine. Following ranitidine intake, the urinary NDMA excreted over 24h increased 400-folds from 110 to 47 600ng, while total N-nitrosamines increased 5-folds. NDMA excretion rates after ranitidine intake equaled or exceeded those observed previously in patients with schistosomiasis, a disease wherein N-nitrosamines are implicated as the etiological agents for bladder cancer. Due to metabolism within the body, urinary NDMA measurements represent a lower-bound estimate of systemic NDMA exposure. Our results suggest a need to evaluate the risks attributable to NDMA associated with chronic consumption of ranitidine, and to identify alternative treatments that minimize exposure to N-nitrosamines.

    View details for DOI 10.1093/carcin/bgw034

    View details for Web of Science ID 000377915800012

    View details for PubMedID 26992900

  • Halogen radicals contribute to photooxidation in coastal and estuarine waters PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Parker, K. M., Mitch, W. A. 2016; 113 (21): 5868-5873

    Abstract

    Although halogen radicals are recognized to form as products of hydroxyl radical ((•)OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile precursor to cloud condensation nuclei, up to fivefold. Using synthetic seawater solutions, we show that the increased photodegradation is specific to dissolved organic matter (DOM) and halides, rather than other seawater salt constituents (e.g., carbonates) or photoactive species (e.g., iron and nitrate). Experiments in synthetic and natural coastal and estuarine water samples demonstrate that the halide-specific increase in photodegradation could be attributed to photochemically generated halogen radicals rather than other photoproduced reactive intermediates [e.g., excited-state triplet DOM ((3)DOM*), reactive oxygen species]. Computational kinetic modeling indicates that seawater halogen radical concentrations are two to three orders of magnitude greater than freshwater (•)OH concentrations and sufficient to account for the observed halide-specific increase in photodegradation. Dark (•)OH generation by gamma radiolysis demonstrates that halogen radical production via (•)OH scavenging by halides is insufficient to explain the observed effect. Using sensitizer models for DOM chromophores, we show that halogen radicals are formed predominantly by direct oxidation of Cl(-) and Br(-) by (3)DOM*, an (•)OH-independent pathway. Our results indicate that halogen radicals significantly contribute to the phototransformation of algal products in coastal or estuarine surface waters.

    View details for DOI 10.1073/pnas.1602595113

    View details for Web of Science ID 000376779900046

    View details for PubMedID 27162335

    View details for PubMedCentralID PMC4889391

  • Structural Modifications to Quaternary Ammonium Polymer Coagulants to Inhibit N-Nitrosamine Formation ENVIRONMENTAL SCIENCE & TECHNOLOGY Zeng, T., Li, R. J., Mitch, W. A. 2016; 50 (9): 4778-4787

    Abstract

    Quaternary ammonium cationic polymers, such as poly(diallyldimethylammonium chloride) (polyDADMAC) and epichlorohydrin-dimethylamine (Epi-DMA), are commonly used by water utilities to enhance removal of particles and dissolved organic matter (DOM) from raw waters. Unfortunately, chloramination of waters treated with quaternary ammonium polymers leads to the formation of carcinogenic N-nitrosodimethylamine (NDMA). In this study, two approaches were developed to modify polyDADMAC and Epi-DMA to inhibit N-nitrosamine formation. The first approach involved treatment of polymers with methyl iodide (MeI), an alkylating agent, to convert polymer-bound tertiary amine groups to less chloramine-reactive quaternary ammonium groups. The second approach involved synthesis of polymers bearing less chloramine-reactive quaternary ammonium groups with dipropylamino (DPA) substituents. Treatment with MeI reduced NDMA formation from polymers by ∼75%, while synthesis of DPA-based polymers eliminated NDMA formation and formed N-nitrosodipropylamine, which is 10-fold less carcinogenic than NDMA, at 20-fold lower yields. Bench-scale jar tests demonstrated that both MeI-treated and DPA-based polymers achieved similar removal of particles and DOM as the original polyDADMAC and Epi-DMA at both low and high doses, but formed significantly less N-nitrosamines. This work demonstrates two approaches for modifying quaternary ammonium cationic polymers, which may enable water utilities to meet potential future regulations on N-nitrosamines while maintaining polymer usage to meet existing regulations.

    View details for DOI 10.1021/acs.est.6b00602

    View details for Web of Science ID 000375521400022

    View details for PubMedID 27096602

  • Impact of Nitrification on the Formation of N-Nitrosamines and Halogenated Disinfection Byproducts within Distribution System Storage Facilities ENVIRONMENTAL SCIENCE & TECHNOLOGY Zeng, T., Mitch, W. A. 2016; 50 (6): 2964-2973
  • Impact of Nitrification on the Formation of N-Nitrosamines and Halogenated Disinfection Byproducts within Distribution System Storage Facilities. Environmental science & technology Zeng, T., Mitch, W. A. 2016; 50 (6): 2964-2973

    Abstract

    Distribution system storage facilities are a critical, yet often overlooked, component of the urban water infrastructure. This study showed elevated concentrations of N-nitrosodimethylamine (NDMA), total N-nitrosamines (TONO), regulated trihalomethanes (THMs) and haloacetic acids (HAAs), 1,1-dichloropropanone (1,1-DCP), trichloroacetaldehyde (TCAL), haloacetonitriles (HANs), and haloacetamides (HAMs) in waters with ongoing nitrification as compared to non-nitrifying waters in storage facilities within five different chloraminated drinking water distribution systems. The concentrations of NDMA, TONO, HANs, and HAMs in the nitrifying waters further increased upon application of simulated distribution system chloramination. The addition of a nitrifying biofilm sample collected from a nitrifying facility to its non-nitrifying influent water led to increases in N-nitrosamine and halogenated DBP formation, suggesting the release of precursors from nitrifying biofilms. Periodic treatment of two nitrifying facilities with breakpoint chlorination (BPC) temporarily suppressed nitrification and reduced precursor levels for N-nitrosamines, HANs, and HAMs, as reflected by lower concentrations of these DBPs measured after re-establishment of a chloramine residual within the facilities than prior to the BPC treatment. However, BPC promoted the formation of halogenated DBPs while a free chlorine residual was maintained. Strategies that minimize application of free chlorine while preventing nitrification are needed to control DBP precursor release in storage facilities.

    View details for DOI 10.1021/acs.est.5b05668

    View details for PubMedID 26859842

  • Ozone Promotes Chloropicrin Formation by Oxidizing Amines to Nitro Compounds. Environmental science & technology McCurry, D. L., Quay, A. N., Mitch, W. A. 2016; 50 (3): 1209-1217

    Abstract

    Chloropicrin formation has been associated with ozonation followed by chlorination, but the reaction pathway and precursors have been poorly characterized. Experiments with methylamine demonstrated that ozonation converts methylamine to nitromethane at ∼100% yield. Subsequent chlorination converts nitromethane to chloropicrin at ∼50% yield under the conditions evaluated. Similarly high yields from other primary amines were limited to those with functional groups on the β-carbon (e.g., the carboxylic acid in glycine) that facilitate carbon-carbon bond cleavage to release nitromethyl anion. Secondary amines featuring these reactive primary amines as functional groups (e.g., secondary N-methylamines) formed chloropicrin at high yields, likely by facile dealkylation to release the primary nitro compound. Chloropicrin yields from tertiary amines were low. Natural water experiments, including derivatization to transform primary and secondary amines to less reactive carbamate functional groups, indicated that primary and secondary amines were the dominant chloropicrin precursors during ozonation/chlorination. Ozonation followed by chlorination of the primary amine side chain of lysine demonstrated low yields (∼0.2%) of chloropicrin, but high yields (∼17%) of dichloronitrolysine, a halonitroalkane structural analogue to chloropicrin. However, chloropicrin yields increased and dichloronitrolysine yields decreased in the absence of hydroxyl radical scavengers, suggesting that future research should characterize the potential occurrence of such halonitroalkane analogues relative to natural radical scavenger (e.g., carbonate) concentrations.

    View details for DOI 10.1021/acs.est.5b04282

    View details for PubMedID 26752338

  • Effect of matrix components on UV/H2O2 and UV/S2O8(2-) advanced oxidation processes for trace organic degradation in reverse osmosis brines from municipal wastewater reuse facilities. Water research Yang, Y., Pignatello, J. J., Ma, J., Mitch, W. A. 2016; 89: 192-200

    Abstract

    When reverse osmosis brines from potable wastewater reuse plants are discharged to poorly-flushed estuaries, the concentrated organic contaminants are a concern for receiving water ecosystems. UV/hydrogen peroxide (UV/H2O2) and UV/persulfate (UV/S2O8(2-)) advanced oxidation processes (AOPs) may reduce contaminant burdens prior to discharge, but the effects of the high levels of halide, carbonate and effluent organic matter (EfOM) normally present in these brines are unclear. On the one hand, these substances may reduce process efficiency by scavenging reactive oxygen species (ROS), hydroxyl (OH) and sulfate (SO4(-) radicals. On the other, the daughter radicals generated by halide and carbonate scavenging may themselves degrade organics, offsetting the effect of ROS scavenging. UV/H2O2 and UV/S2O8(2-) AOPs were compared for degradation of five pharmaceuticals spiked into brines obtained from two reuse facilities and the RO influent from one of them. For UV/H2O2, EfOM scavenged ∼75% of the OH, reducing the degradation efficiency of the target contaminants to a similar extent; halide and carbonate scavenging and the reactivities of associated daughter radicals were less important. For UV/S2O8(2-), anions (mostly Cl(-)) scavenged ∼93% of the SO4(-). Because daughter radicals of Cl(-) contributed to contaminant degradation, the reduction in contaminant degradation efficiency was only ∼75-80%, with the reduction driven by daughter radical scavenging by EfOM. Conversion of SO4(-) to more selective halogen and carbonate radicals resulted in a wider range of degradation efficiencies among the contaminants. For both AOPs, 250 mJ/cm(2) average fluence achieved significant removal of four pharmaceuticals, with significantly better performance by UV/S2O8(2-) treatment for some constituents. Accounting for the lower brine flowrates, the energy output to achieve this fluence in brines is comparable to that often applied to RO permeates. However, much higher fluence was required for the least reactive pharmaceutical. Comparing AOP application to the RO influent or brine, equal or greater removal was achieved for brine treatment for comparable energy input. AOP treatment of brines could be applied to reduce, but not eliminate, contaminant burdens prior to discharge.

    View details for DOI 10.1016/j.watres.2015.11.049

    View details for PubMedID 26657355

  • Influence of Bi-doping on Mn1-xBixFe2O4 catalytic ozonation of di-n-butyl phthalate CHEMICAL ENGINEERING JOURNAL Ren, Y., Chen, Y., Zeng, T., Feng, J., Ma, J., Mitch, W. A. 2016; 283: 622-630
  • Control of nitrosamines during non-potable and de facto wastewater reuse with medium pressure ultraviolet light and preformed monochloramine ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY McCurry, D. L., Krasner, S. W., Mitch, W. A. 2016; 2 (3): 502-510

    View details for DOI 10.1039/c6ew00044d

    View details for Web of Science ID 000376360300008

  • Formation Pathways and Trade-Offs between Haloacetamides and Haloacetaldehydes during Combined Chlorination and Chloramination of Lignin Phenols and Natural Waters ENVIRONMENTAL SCIENCE & TECHNOLOGY Chuang, Y., McCurry, D. L., Tung, H., Mitch, W. A. 2015; 49 (24): 14432-14440

    View details for DOI 10.1021/acs.est.5b04783

    View details for Web of Science ID 000366872300064

    View details for PubMedID 26571080

  • Degradation of Amino Acids and Structure in Model Proteins and Bacteriophage MS2 by Chlorine, Bromine, and Ozone. Environmental science & technology Choe, J. K., Richards, D. H., Wilson, C. J., Mitch, W. A. 2015; 49 (22): 13331-13339

    View details for DOI 10.1021/acs.est.5b03813

    View details for PubMedID 26488608

  • Contribution of N-Nitrosamines and Their Precursors to Domestic Sewage by Greywaters and Blackwaters. Environmental science & technology Zeng, T., Mitch, W. A. 2015; 49 (22): 13158-13167

    View details for DOI 10.1021/acs.est.5b04254

    View details for PubMedID 26496512

  • Determinants of disinfectant pretreatment efficacy for nitrosamine control in chloraminated drinking water. Water research McCurry, D. L., Krasner, S. W., von Gunten, U., Mitch, W. A. 2015; 84: 161-170

    Abstract

    Utilities using chloramines need strategies to mitigate nitrosamine formation to meet potential future nitrosamine regulations. The ability to reduce NDMA formation under typical post-chloramination conditions of pretreatment with ultraviolet light from a low pressure mercury lamp (LPUV), free chlorine (HOCl), ozone (O3), and UV light from a medium pressure mercury lamp (MPUV) were compared at exposures relevant to drinking water treatment. The order of efficacy after application to waters impacted by upstream wastewater discharges was O3 > HOCl ≈ MPUV > LPUV. NDMA precursor abatement generally did not correlate well between oxidants, and waters exhibited different behaviors with respect to pH and temperature, suggesting a variety of source-dependent NDMA precursors. For wastewater-impacted waters, the observed pH dependence for precursor abatement suggested the important role of secondary or tertiary amine precursors. Although hydroxyl radicals did not appear to be important for NDMA precursor abatement during O3 or MPUV pretreatment, the efficacy of MPUV correlated strongly with dissolved organic carbon concentration (p = 0.01), suggesting alternative indirect photochemical pathways. The temperature dependences during pre- and post-disinfection indicated that NDMA formation is likely to increase during warm seasons for O3 pretreatment, decrease for HOCl pretreatment, and remain unchanged for MPUV treatment, although seasonal changes in source water quality may counteract the temperature effects. For two waters impacted by relatively high polyDADMAC coagulant doses, pretreatment with HOCl, O3, and MPUV increased NDMA formation during post-chloramination. For O3 pretreatment, hydroxyl radicals likely led to precursor formation from the polymer in the latter tests. MPUV treatment of polymer-impacted water increased subsequent NDMA formation through an indirect photochemical process. Many factors may mitigate the importance of this increased NDMA formation, including the low polyDADMAC doses typically applied, and simultaneous degradation of watershed-associated precursors.

    View details for DOI 10.1016/j.watres.2015.07.024

    View details for PubMedID 26232674

  • Influence of Dissolved Metals on N-Nitrosamine Formation under Amine-based CO2 Capture Conditions ENVIRONMENTAL SCIENCE & TECHNOLOGY Wang, Z., Mitch, W. A. 2015; 49 (19): 11974-11981

    View details for DOI 10.1021/acs.est.5b03085

    View details for Web of Science ID 000362629100083

    View details for PubMedID 26335609

  • Leveraging the Mechanism of Oxidative Decay for Adenylate Kinase to Design Structural and Functional Resistances ACS CHEMICAL BIOLOGY Howell, S. C., Richards, D. H., Mitch, W. A., Wilson, C. J. 2015; 10 (10): 2393-2404

    View details for DOI 10.1021/acschembio.5b00431

    View details for Web of Science ID 000363225100024

    View details for PubMedID 26266833

  • Controlling Nitrosamines, Nitramines, and Amines in Amine-Based CO2 Capture Systems with Continuous Ultraviolet and Ozone Treatment of Washwater ENVIRONMENTAL SCIENCE & TECHNOLOGY Dai, N., Mitch, W. A. 2015; 49 (14): 8878-8886

    Abstract

    Formation of nitrosamines and nitramines from reactions between flue gas NOx and the amines used in CO2 capture units has arisen as a significant concern. Washwater scrubbers can capture nitrosamines and nitramines. They can also capture amines, preventing formation of nitrosamines and nitramines downwind by amine reactions with ambient NOx. The continuous application of UV alone, or a combination of UV and ozone to the return line of a washwater treatment unit was evaluated to control the accumulation of nitrosamines, nitramines and amines in a laboratory-scale washwater unit. With model secondary amine solvents ranging from nonvolatile diethanolamine to volatile morpholine, application of 272-537 mJ/cm(2) UV incident fluence alone reduced the accumulation of nitrosamines and nitramines by approximately an order of magnitude. Modeling indicated that the gains achieved by UV treatment should increase over time, because UV treatment converts the time dependence of nitrosamine accumulation from a quadratic to a linear function. Ozone (21 mg/L) maintained low steady-state concentrations of amines in the washwater. While modeling indicated that more than 80% of nitrosamine accumulation in the washwater was associated with reaction of washwater amines with residual NOx, a reduction in nitrosamine accumulation rates due to ozone oxidation of amines was not fully realized because the ozonation products of amines reduced nitrosamine photolysis rates by competing for photons.

    View details for DOI 10.1021/acs.est.5b01365

    View details for Web of Science ID 000358557900070

  • Destruction of methyl bromide sorbed to activated carbon by thiosulfate or electrolysis. Environmental science & technology Yang, Y., Li, Y., Walse, S. S., Mitch, W. A. 2015; 49 (7): 4515-4521

    Abstract

    Methyl bromide (CH3Br) is widely used as a fumigant for postharvest and quarantine applications for agricultural products at port facilities due to the short treatment period required, but it is vented from fumigation chambers to the atmosphere after its use. Due to the potential contributions of CH3Br to stratospheric ozone depletion, technologies for the capture and degradation of the CH3Br are needed to enable its continued use. Although granular activated carbon (GAC) has been used for CH3Br capture and thiosulfate has been used for destruction of CH3Br in aqueous solution, this research explored techniques for direct destruction of CH3Br sorbed to GAC. Submerging the GAC in an aqueous thiosulfate solution achieved debromination of CH3Br while sorbed to the GAC, but it required molar concentrations of thiosulfate because of the high CH3Br loading and produced substantial concentrations of methyl thiosulfate. Submergence of the GAC in water and use of the GAC as the cathode of an electrolysis unit also debrominated sorbed CH3Br. The reaction appeared to involve a one-electron transfer, producing methyl radicals that incorporated into the GAC. Destruction rates increased with decreasing applied voltage down to ∼-1.2 V vs the standard hydrogen electrode. Cycling experiments conducted at -0.77 V indicated that >80% debromination of CH3Br was achieved over ∼30 h with ∼100% Coulombic efficiency. Sorptive capacity and degradation efficiency were maintained over at least 3 cycles. Capture of CH3Br fumes from fumigation chambers onto GAC, and electrolytic destruction of the sorbed CH3Br could mitigate the negative impacts of CH3Br usage pending the development of suitable replacement fumigants.

    View details for DOI 10.1021/es505709c

    View details for PubMedID 25789797

  • Reduction of Nitroaromatics Sorbed to Black Carbon by Direct Reaction with Sorbed Sulfides ENVIRONMENTAL SCIENCE & TECHNOLOGY Xu, W., Pignatello, J. J., Mitch, W. A. 2015; 49 (6): 3419-3426

    Abstract

    Sorption to black carbons is an important sink for organic contaminants in sediments. Previous research has suggested that black carbons (graphite, activated carbon, and biochar) mediate the degradation of nitrated compounds by sulfides by at least two different pathways: reduction involving electron transfer from sulfides through conductive carbon regions to the target contaminant (nitroglycerin) and degradation by sulfur-based intermediates formed by sulfide oxidation (RDX). In this study, we evaluated the applicability of black carbon-mediated reactions to a wider variety of contaminant structures, including nitrated and halogenated aromatic compounds, halogenated heterocyclic aromatic compounds, and halogenated alkanes. Among these compounds, black carbon-mediated transformation by sulfides over a 3-day time scale was limited to nitroaromatic compounds. The reaction for a series of substituted nitroaromatics proceeded by reduction, as indicated by formation of 3-bromoaniline from 3-bromonitrobenzene, and inverse correlation of log kobs with energy of the lowest unoccupied molecular orbital (ELUMO). The log kobs was correlated with sorbed sulfide concentration, but no reduction of 3-bromonitrobenzene was observed in the presence of graphite and sulfite, thiosulfate, or polysulfides. Whereas nitroglycerin reduction occurred in an electrochemical cell containing sheet graphite electrodes in which the reagents were placed in separate compartments, nitroaromatic reduction only occurred when sulfides were present in the same compartment. The results suggest that black carbon-mediated reduction of sorbed nitroaromatics by sulfides involves electron transfer directly from sorbed sulfides rather than transfer of electrons through conductive carbon regions. The existence of three different reaction pathways suggests a complexity to the sulfide-carbon system compared to the iron-carbon system, where contaminants are reduced by electron transfer through conductive carbon regions.

    View details for DOI 10.1021/es5045198

    View details for Web of Science ID 000351324400019

    View details for PubMedID 25671390

  • Predicting N-Nitrosamines: N-Nitrosodiethanolamine as a Significant Component of Total N-Nitrosamines in Recycled Wastewater ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS Dai, N., Zeng, T., Mitch, W. A. 2015; 2 (3): 54-58
  • Iodide, Bromide, and Ammonium in Hydraulic Fracturing and Oil and Gas Wastewaters: Environmental Implications ENVIRONMENTAL SCIENCE & TECHNOLOGY Harkness, J. S., Dwyer, G. S., Warner, N. R., Parker, K. M., Mitch, W. A., Vengosh, A. 2015; 49 (3): 1955-1963

    Abstract

    The expansion of unconventional shale gas and hydraulic fracturing has increased the volume of the oil and gas wastewater (OGW) generated in the U.S. Here we demonstrate that OGW from Marcellus and Fayetteville hydraulic fracturing flowback fluids and Appalachian conventional produced waters is characterized by high chloride, bromide, iodide (up to 56 mg/L), and ammonium (up to 420 mg/L). Br/Cl ratios were consistent for all Appalachian brines, which reflect an origin from a common parent brine, while the I/Cl and NH4/Cl ratios varied among brines from different geological formations, reflecting geogenic processes. There were no differences in halides and ammonium concentrations between OGW originating from hydraulic fracturing and conventional oil and gas operations. Analysis of discharged effluents from three brine treatment sites in Pennsylvania and a spill site in West Virginia show elevated levels of halides (iodide up to 28 mg/L) and ammonium (12 to 106 mg/L) that mimic the composition of OGW and mix conservatively in downstream surface waters. Bromide, iodide, and ammonium in surface waters can impact stream ecosystems and promote the formation of toxic brominated-, iodinated-, and nitrogen disinfection byproducts during chlorination at downstream drinking water treatment plants. Our findings indicate that discharge and accidental spills of OGW to waterways pose risks to both human health and the environment.

    View details for DOI 10.1021/es504654n

    View details for Web of Science ID 000349060300086

    View details for PubMedID 25587644

  • Synthesis and Application of a Quaternary Phosphonium Polymer Coagulant To Avoid N-Nitrosamine Formation ENVIRONMENTAL SCIENCE & TECHNOLOGY Zeng, T., Pignatello, J. J., Li, R. J., Mitch, W. A. 2014; 48 (22): 13392-13401

    View details for DOI 10.1021/es504091s

    View details for Web of Science ID 000345262900045

  • Superior Removal of Disinfection Byproduct Precursors and Pharmaceuticals from Wastewater in a Staged Anaerobic Fluidized Membrane Bioreactor Compared to Activated Sludge ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS McCurry, D. L., Bear, S. E., Bae, J., Sedlak, D. L., McCarty, P. L., Mitch, W. A. 2014; 1 (11): 459-464

    View details for DOI 10.1021/ez500279a

    View details for Web of Science ID 000350831700005

  • Impact of UV/H2O2 Pre-Oxidation on the Formation of Haloacetamides and Other Nitrogenous Disinfection Byproducts during Chlorination ENVIRONMENTAL SCIENCE & TECHNOLOGY Chu, W., Gao, N., Yin, D., Krasner, S. W., Mitch, W. A. 2014; 48 (20): 12190-12198

    View details for DOI 10.1021/es502115x

    View details for Web of Science ID 000343640900054

  • Enhanced Formation of Disinfection Byproducts in Shale Gas Wastewater-Impacted Drinking Water Supplies ENVIRONMENTAL SCIENCE & TECHNOLOGY Parker, K. M., Zeng, T., Harkness, J., Vengosh, A., Mitch, W. A. 2014; 48 (19): 11161-11169

    View details for DOI 10.1021/es5028184

    View details for Web of Science ID 000343016600020

  • Comparative in Vitro Toxicity of Nitrosamines and Nitramines Associated with Amine-based Carbon Capture and Storage ENVIRONMENTAL SCIENCE & TECHNOLOGY Wagner, E. D., Osiol, J., Mitch, W. A., Plewa, M. J. 2014; 48 (14): 8203-8211

    Abstract

    Amine-based CO2 capture is a prime contender for the first full-scale implementation of CO2 capture at fossil fuel-fired power plants postcombustion. However, the formation of potentially carcinogenic N-nitrosamines and N-nitramines from reactions of flue gas NOx with the amines presents a potential risk for contaminating airsheds and drinking water supplies. Setting regulatory emission limits is hampered by the dearth of toxicity information for the N-nitramines. This study employed quantitative in vitro bioassays for mutagenicity in Salmonella typhimurium, and chronic cytotoxicity and acute genotoxicity in Chinese hamster ovary (CHO) cells to compare the toxicity of analogous N-nitrosamines and N-nitramines relevant to CO2 capture. Although the rank order was similar for genotoxicity in CHO cells and mutagenicity in S. typhimurium, the Salmonella assay was far more sensitive. In general, mutagenicity was higher with S9 hepatic microsomal activation. The rank order of mutagenicity was N-nitrosodimethylamine (NDMA)>N-nitrosomorpholine>N-nitrodimethylamine>1,4-dinitrosopiperazine>N-nitromorpholine>1,4-dinitropiperazine>N-nitromonoethanolamine>N-nitrosodiethanolamine>N-nitrodiethanolamine. 1-Nitrosopiperazine and 1-nitropiperazine were not mutagenic. Overall, N-nitrosamines were ∼15-fold more mutagenic than their N-nitramine analogues.

    View details for DOI 10.1021/es5018009

    View details for Web of Science ID 000339227500065

    View details for PubMedID 24940705

  • Effects of Flue Gas Compositions on Nitrosamine and Nitramine Formation in Postcombustion CO2 Capture Systems ENVIRONMENTAL SCIENCE & TECHNOLOGY Dai, N., Mitch, W. A. 2014; 48 (13): 7519-7526

    View details for DOI 10.1021/es501864a

    View details for Web of Science ID 000338488700041

  • Sunlight-Driven Photochemical Halogenation of Dissolved Organic Matter in Seawater: A Natural Abiotic Source of Organobromine and Organoiodine ENVIRONMENTAL SCIENCE & TECHNOLOGY Diego Mendez-Diaz, J., Shimabuku, K. K., Ma, J., Enumah, Z. O., Pignatello, J. J., Mitch, W. A., Dodd, M. C. 2014; 48 (13): 7418-7427

    Abstract

    Reactions of dissolved organic matter (DOM) with photochemically generated reactive halogen species (RHS) may represent an important natural source of organohalogens within surface seawaters. However, investigation of such processes has been limited by difficulties in quantifying low dissolved organohalogen concentrations in the presence of background inorganic halides. In this work, sequential solid phase extraction (SPE) and silver-form cation exchange filtration were utilized to desalt and preconcentrate seawater DOM prior to nonspecific organohalogen analysis by ICP-MS. Using this approach, native organobromine and organoiodine contents were found to range from 3.2-6.4 × 10(-4) mol Br/mol C and 1.1-3.8 × 10(-4) mol I/mol C (or 19-160 nmol Br L(-1) and 6-36 nmol I L(-1)) within a wide variety of natural seawater samples, compared with 0.6-1.2 × 10(-4) mol Br/mol C and 0.6-1.1 × 10(-5) mol I/mol C in terrestrial natural organic matter (NOM) isolates. Together with a chemical probe method specific for RHS, the SPE+ICP-MS approach was also employed to demonstrate formation of nanomolar levels of organobromine and organoiodine during simulated and natural solar irradiation of DOM in artificial and natural seawaters. In a typical experiment, the organobromine content of 2.1 × 10(-4) mol C L(-1) (2.5 mg C L(-1)) of Suwannee River NOM in artificial seawater increased by 69% (from 5.9 × 10(-5) to 1.0 × 10(-4) mol Br/mol C) during exposure to 24 h of simulated sunlight. Increasing I(-) concentrations (up to 2.0 × 10(-7) mol L(-1)) promoted increases of up to 460% in organoiodine content (from 8.5 × 10(-6) to 4.8 × 10(-5) mol I/mol C) at the expense of organobromine formation under the same conditions. The results reported herein suggest that sunlight-driven reactions of RHS with DOM may play a significant role in marine bromine and iodine cycling.

    View details for DOI 10.1021/es5016668

    View details for Web of Science ID 000338488700029

  • Effect of Chemical Oxidation on the Sorption Tendency of Dissolved Organic Matter to a Model Hydrophobic Surface ENVIRONMENTAL SCIENCE & TECHNOLOGY Zeng, T., Wilson, C. J., Mitch, W. A. 2014; 48 (9): 5118-5126

    Abstract

    The application of chemical oxidants may alter the sorption properties of dissolved organic matter (DOM), such as humic and fulvic acids, proteins, polysaccharides, and lipids, affecting their fate in water treatment processes, including attachment to other organic components, activated carbon, and membranes (e.g., organic fouling). Similar reactions with chlorine (HOCl) and bromine (HOBr) produced at inflammatory sites in vivo affect the fate of biomolecules (e.g., protein aggregation). In this study, quartz crystal microbalance with dissipation monitoring (QCM-D) was used to evaluate changes in the noncovalent interactions of proteins, polysaccharides, fatty acids, and humic and fulvic acids with a model hydrophobic surface as a function of increasing doses of HOCl, HOBr, and ozone (O3). All three oxidants enhanced the sorption tendency of proteins to the hydrophobic surface at low doses but reduced their sorption tendency at high doses. All three oxidants reduced the sorption tendency of polysaccharides and fatty acids to the hydrophobic surface. HOCl and HOBr increased the sorption tendency of humic and fulvic acids to the hydrophobic surface with maxima at moderate doses, while O3 decreased their sorption tendency. The behavior observed with two water samples was similar to that observed with humic and fulvic acids, pointing to the importance of these constituents. For chlorination, the highest sorption tendency to the hydrophobic surface was observed within the range of doses typically applied during water treatment. These results suggest that ozone pretreatment would minimize membrane fouling by DOM, while chlorine pretreatment would promote DOM removal by activated carbon.

    View details for DOI 10.1021/es405257b

    View details for Web of Science ID 000335720100058

    View details for PubMedID 24697505

  • Comparison of Halide Impacts on the Efficiency of Contaminant Degradation by Sulfate and Hydroxyl Radical-Based Advanced Oxidation Processes (AOPs) ENVIRONMENTAL SCIENCE & TECHNOLOGY Yang, Y., Pignatello, J. J., Ma, J., Mitch, W. A. 2014; 48 (4): 2344-2351

    Abstract

    The effect of halides on organic contaminant destruction efficiency was compared for UV/H2O2 and UV/S2O8(2-) AOP treatments of saline waters; benzoic acid, 3-cyclohexene-1-carboxylic acid, and cyclohexanecarboxylic acid were used as models for aromatic, alkene, and alkane constituents of naphthenic acids in oil-field waters. In model freshwater, contaminant degradation was higher by UV/S2O8(2-) because of the higher quantum efficiency for S2O8(2-) than H2O2 photolysis. The conversion of (•)OH and SO4(•-) radicals to less reactive halogen radicals in the presence of seawater halides reduced the degradation efficiency of benzoic acid and cyclohexanecarboxylic acid. The UV/S2O8(2-) AOP was more affected by Cl(-) than the UV/H2O2 AOP because oxidation of Cl(-) is more favorable by SO4(•-) than (•)OH at pH 7. Degradation of 3-cyclohexene-1-carboxylic acid, was not affected by halides, likely because of the high reactivity of halogen radicals with alkenes. Despite its relatively low concentration in saline waters compared to Cl(-), Br(-) was particularly important. Br(-) promoted halogen radical formation for both AOPs resulting in ClBr(•-), Br2(•-), and CO3(•-) concentrations orders of magnitude higher than (•)OH and SO4(•-) concentrations and reducing differences in halide impacts between the two AOPs. Kinetic modeling of the UV/H2O2 AOP indicated a synergism between Br(-) and Cl(-), with Br(-) scavenging of (•)OH leading to BrOH(•-), and further reactions of Cl(-) with this and other brominated radicals promoting halogen radical concentrations. In contaminant mixtures, the conversion of (•)OH and SO4(•-) radicals to more selective CO3(•-) and halogen radicals favored attack on highly reactive reaction centers represented by the alkene group of 3-cyclohexene-1-carboxylic acid and the aromatic group of the model compound, 2,4-dihydroxybenzoic acid, at the expense of less reactive reaction centers such as aromatic rings and alkane groups represented in benzoic acid and cyclohexanecarboxylic acid. This effect was more pronounced for the UV/S2O8(2-) AOP.

    View details for DOI 10.1021/es404118q

    View details for Web of Science ID 000331774100031

    View details for PubMedID 24479380

  • Influence of Amine Structural Characteristics on N-Nitrosamine Formation Potential Relevant to Postcombustion CO2 Capture Systems ENVIRONMENTAL SCIENCE & TECHNOLOGY Dai, N., Mitch, W. A. 2013; 47 (22): 13175-13183

    Abstract

    Concerns have arisen for the possible contamination of air or drinking water supplies downwind of amine-based CO2 capture facilities by potentially carcinogenic N-nitrosamines formed from reactions between flue gas NOx and amine solvents. This study evaluated the influence of amine structure on the potential to form total N-nitrosamines within the absorber and washwater units of a laboratory-scale CO2 capture reactor, and in the solvent after a pressure-cooker treatment as a mimic of desorber conditions. Among 16 amines representing 3 amine classes (alkanolamines, straight-chain and cyclic diamines, and amino acids), the order of the amine was the primary determinant of total N-nitrosamine formation in the absorber unit, with total N-nitrosamine formation in the order: secondary amines ≈ tertiary amines ≫ primary amines. Similar results were observed upon pressure-cooker treatment, due to reactions between nitrite and amines at high temperature. For secondary and tertiary amines, total N-nitrosamine formation under these desorber-like conditions appeared to be more important than in the absorber, but for primary amines, significant formation of total N-nitrosamines was only observed in the absorber. For diamines and amino acids, total N-nitrosamine accumulation rates in washwaters were lowest for primary amines. For alkanolamines, however, total N-nitrosamine accumulation in the washwater was similar regardless of alkanolamine order, due to the combined effects of amine reactivity toward nitrosation and amine volatility. While total N-nitrosamine accumulation rates in washwaters were generally 1-2 orders of magnitude lower than in the absorber, they were comparable to absorber rates for several primary amines. Decarboxylation of the amino acid sarcosine resulted in the accumulation of significant concentrations of N-nitrosodimethylamine and N-nitrodimethylamine in the washwater.

    View details for DOI 10.1021/es4035396

    View details for Web of Science ID 000327360600069

    View details for PubMedID 24138561

  • Influence of ionic strength on triplet-state natural organic matter loss by energy transfer and electron transfer pathways. Environmental science & technology Parker, K. M., Pignatello, J. J., Mitch, W. A. 2013; 47 (19): 10987-10994

    Abstract

    Triplet state excited natural organic matter chromophores ((3)NOM*) are important reactive intermediates in indirect photochemical processes, yet the impact of salt concentrations relevant to estuarine and marine environments on (3)NOM* is poorly understood. The formation rates, pseudo-first-order loss rate constants, and steady-state concentration of (3)NOM* were monitored using the sorbate probe method in synthetic matrices with increasing ionic strength (IS) to seawater values using seawater halides or other salts. The steady-state concentration of (3)NOM* approximately doubled at seawater IS, regardless of the salt used, due to a decrease in the (3)NOM* decay rate constant. The electron transfer-mediated degradation of 2,4,6-trimethylphenol (TMP) by (3)NOM* was significantly slowed at higher IS. A model is proposed wherein high IS slows intra-organic matter electron transfer pathways, an important (3)NOM* loss pathway, leading to longer (3)NOM* lifetimes. Although IS did not appear to impact energy transfer pathways directly, the higher (3)NOM* steady-state concentrations promote energy transfer interactions. The observed decrease in decay rate constant, increase in steady-state concentration of (3)NOM* at high IS, and the inhibition of electron transfer pathways should be considered when determining the fate of organic pollutants in estuarine and marine environments.

    View details for DOI 10.1021/es401900j

    View details for PubMedID 23952218

  • Dual role for lysine during protein modification by HOCl and HOBr: lysine nitrile as a putative biomarker for oxidative stress. Biochemistry Sivey, J., D., Howell, S., C., Bean, D., J., McCurry, D., L., Mitch, W., A., Wilson, C., J. 2013; 52: 1260-1271
  • Influence of amine structural characteristics of N-nitrosamine formation potential relevant to postcombustion CO2 capture systems. Environ. Sci. Technol. Dai, N., Mitch, W., A. 2013; 47: 13175-13183
  • Application of ultraviolet, ozone, and advanced oxidation treatments to washwaters to destroy nitrosamines, nitramines, amines, and aldehydes formed during amine-based carbon capture. Environ. Sci. Technol. Shah, A., D., Dai, N., Mitch, W., A. 2013; 47: 2799-2808
  • Formation, precursors, control, and occurrence of nitrosamines in drinking water: areview. Wat. Res. Krasner, S., W., Mitch, W., A., McCurry, D., L., Hanigan, D., Westerhoff, P. 2013; 47: 4433-4450
  • The role of black carbon electrical conductivity in mediating hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) transformation on carbon surfaces by sulfides. Environ. Sci. Technol. Xu, W., Pignatello, J., J., Mitch, W., A. 2013; 47: 7129-7136
  • Relative importance of N-nitrosodimethylamine compared to total N-nitrosamines in drinking waters. Environ. Sci. Technol. Dai, N., Mitch, W., A. 2013; 47: 3648-3656
  • Formation and control of emerging C- and N-DBPs in drinking water. Journal AWWA Krasner, S., W., Mitch, W., A., Westerhoff, P., Dotson, A., D. 2012; 104: E582-E595
  • Dichloroacetonitrile and dichloroacetamidecan form independently during chlorination and chloramination of drinking waters, model organic matters and wastewater effluents. Environ. Sci. Technol. Huang, H., Wu, Q.-Y., Hu, H.-Y., Mitch, W., A. 2012; 46: 10624-10631
  • Measurement of nitrosamine and nitramine formation from NOx reactions with amines during amine-based carbon dioxide capture for post-combustion carbon sequestration. Environ. Sci. Technol. Dai, N., Shah, A., D., Hu, L., Plewa, M., J., McKague, B., Mitch, W., A. 2012; 46: 9793-9801
  • Impact of halide ions on natural organic matter-sensitized photolysis of 17β-Estradiol in saline waters. Environ. Sci. Technol. Grebel, J., E., Pignatello, J., J., Mitch, W., A. 2012; 46: 7128-7134
  • Halonitroalkanes, halonitriles, haloamides and N-nitrosamines: A critical review of nitrogenous disinfection byproduct (N-DBP) formation pathways. Environ. Sci. Technol. Shah, A., D., Mitch, W., A. 2012; 46: 119-131
  • Comparative genotoxicity of nitrosamine drinking water disinfection byproducts in Salmonella and mammalian cells. Mutation Research Wagner, E., D., Hsu, K.-M., Lagunas, A., Mitch, W., A., Plewa, M., J. 2012; 741: 109-115
  • Tradeoffs in disinfection byproduct formation associated with precursor pre-oxidation for control of nitrosamine formation. Environ. Sci. Technol. Shah, A., D., Krasner, S., W., Chen, T., C.-F., Gunten, U., von, Mitch, W., A. 2012; 46: 4809-4818
  • Comparative mammalian cell cytotoxicity of water concentrates from disinfected recreational pools. Environ. Sci. Technol. Plewa, M., J., Wagner, E., D., Mitch, W., A. 2011; 45: 4159-4165
  • Sorbic acid as a quantitative probe for the formation, scavenging and steady-state concentrations of the triplet-excited state of organic compounds. Wat. Res. Grebel, J., E., Pignatello, J., J., Mitch, W., A. 2011; 45: 6535-6544
  • Impact of UV disinfection combined with chlorination/chloramination on the formation of halonitromethanes and haloacetonitriles in drinking water. Environ. Sci. Technol. Shah, A., D., Dotson, A., D., Linden, K., G., Mitch, W., A. 2011; 45: 3657-3664
  • Effect of halide ions on organic contaminant degradation by hydroxyl radical-based advanced oxidation processes. Environ. Sci. Technol. Grebel, J., E., Pignatello, J., J., Mitch, W., A. 2010; 44: 6822-6828
  • Chapter 7 Micropollutants in water recycling: A case study of N-nitrosodimethylamine (NDMA) exposure from water versus food. Sustainability Science and Engineering Schafer, A., I., Mitch, W., A., Walewijk, S., Munoz, A., Teuten, E. 2010; 2: 203-228
  • Quaternary amines as NDMA precursors: a role for consumer products? Environ. Sci. Technol. Kemper, J., M., Walse, S., S., Mitch, W., A. 2010; 4 (44): 1224-1231
  • Influence of the method of reagent addition on dichloroacetonitrile formation during chloramination. Environ. Sci. Technol. Hayes-Larson, E., L., Mitch, W., A. 2010; 2 (44): 700-706
  • Genotoxicity of water concentrates from recreational pools after various disinfection methods. Environ. Sci. Technol. Liviac, D., Wagner, E., D., Mitch, W., A., Altonji, M., J., Plewa, M., J. 2010; 44: 3537-3332
  • Fecal coliform accumulation within a river subject to seasonally-disinfected wastewater discharges. Wat. Res. Mitch, A., A., Gasner, K., C., Mitch, W., A. 2010; 16 (44): 4776-4782
  • Comparison of byproduct formation in waters treated with chlorine and iodine: relevance to point-of-use treatment Environ. Sci. Technol. Smith, E., M., Plewa, M., J., Lindell, C., L., Richardson, S., D., Mitch, W., A. 2010; 44: 8446-8552
  • Black-carbon mediated destruction of nitroglycerin and RDX by hydrogen sulfide: relevance to in-situ remediation. Environ. Sci. Technol. Xu, W., Dana, K., E., Mitch, W., A. 2010; 44: 6409-6415
  • Application of an optimized total N-nitrosamine (TONO) assay to pools: placing N-nitrosodimethylamine (NDMA) determinations into perspective. Environ. Sci. Technol. Kulshrestha, P., McKinstry, K., C., Fernandez, B., O., Feelisch, M., Mitch, W., A. 2010; 44: 3369-3375
  • Exploring amino acid side chain decomposition using enzymatic digestion and HPLC-MS: combined lysine transformations in chlorinated waters. Anal. Chem. Walse, S., S., Plewa, M., J., Mitch, W., A. 2009; 18 (81): 7650-7659
  • Occurrence and fate of nitrosamines and their precursors in municipal sludge and anaerobic digestion systems. Environ. Sci. Technol. Padhye, L., Tezel, U., Mitch, W., A., Pavlostathis, S., G., Huang, C.-H. 2009; 9 (43): 3087-3093
  • Nitrosamine, dimethylnitramine and chloropicrin formation during strong base anion exchange treatment. Environ. Sci. Technol. Kemper, J., M., Westerhoff, P., Dotson, A., D., Mitch, W., A. 2009; 2 (43): 466-472
  • Impact of halides on the photobleaching of dissolved organic matter. Marine Chem. Grebel, J., E., Pignatello, J., J., Song, W., Cooper, W., J., Mitch, W., A. 2009; 115: 134-144
  • Abiotic degradation of RDX in the presence of hydrogen sulfide and black carbon. Environ. Sci. Technol. Kemper, J., M., Ammar, E., Mitch, W., A. 2008; 6 (42): 2118-2123
  • Degradation of tertiary alkylamines during chlorination/chloramination: implications for formation of aldehydes, nitriles, halonitroalkanes, and nitrosamines. Environ. Sci. Technol. Mitch, W., A., Schreiber, I., M. 2008; 13 (42): 4811 - 4817
  • Nitrosamine carcinogens also swim in pools. Environ. Sci. Technol. Walse, S., S., Mitch, W., A. 2008; 4 (42): 1032-1037
  • Enhanced nitrogenous disinfection byproduct formation near the breakpoint: implications for nitrification control. Environ. Sci. Technol. Schreiber, I., M., Mitch, W., A. 2007; 20 (41): 7039-7046
  • Nitrile, aldehyde and halonitroalkane formation during chlorination/chloramination of primary amines. Environ. Sci. Technol. Joo, S.-H., Mitch, W., A. 2007; 4 (41): 1288-1296
  • Nitrosamine formation pathway revisited: the importance of dichloramine and dissolved oxygen. Environ. Sci. Technol. Schreiber, I., M., Mitch, W., A. 2006; 19 (40): 6007-6014
  • Occurrence and fate of nitrosamines and nitrosamine precursors in wastewater-impacted surface waters using boron as a conservative tracer. Environ. Sci. Technol. Schreiber, I., M., Mitch, W., A. 2006; 10 (40): 3203-3210
  • Minimization of NDMA formation during chlorine disinfection of municipal wastewater by application of pre-formed chloramines. Environ. Eng. Sci. Mitch, W., A., Oelker, G., L., Hawley, E., L., Deeb, R., A., Sedlak, D., L. 2005; 6 (22): 882-890
  • The influence of the order of reagent addition on N-nitrosodimethylamine formation. Environ. Sci. Technol. Schreiber, I., M., Mitch, W., A. 2005; 10 (39): 3811-3818
  • Sources and fate of nitrosodimethylamine and its precursors in municipal wastewater treatment plants. Wat. Environ. Res. Sedlak, D., L., Deeb, R., Hawley, E., Mitch, W., Durbin, T., Mowbray, S. 2005; 1 (77): 32-39
  • Characterization and fate of N-nitrosodimethylamine (NDMA) precursors during municipal wastewater treatment Environ. Sci. Technol. Mitch, W., A., Sedlak, D., L. 2004; 5 (38): 1445-1454
  • A N-nitrosodimethylamine (NDMA) precursor analysis for chlorination of water and wastewater. Wat. Res. Mitch, W., A., Gerecke, A., Sedlak, D., L. 2003; 15 (37): 3733-3741
  • N-nitrosodimethylamine (NDMA) as a drinking water contaminant: a review. Environ. Eng. Sci. Mitch, W., A., Sharp, J., O., Trussell, R., R., Valentine, R., L., Alvarez-Cohen, L., Sedlak, D., L. 2003; 5 (20): 389-404
  • Factors controlling nitrosamine formation during wastewater chlorination. Water Sci Technol. Mitch, W., A., Sedlak, D., L. 2002; 3 (2): 191-198
  • Formation of N-nitrosodimethylamine (NDMA) from dimethylamine during chlorination. Environ. Sci. Technol. Mitch, W., A., Sedlak, D., L. 2002; 36: 588-595