Julie R. Peller

Ultrasonic mineralization of a reactive textile azo dye remazol black B

The degradation of a reactive black dye in oxygen saturated aqueous solution has been investigated using a high frequency ultrasonic generator. The OH radical initiated oxidative degradation of the dye results in 65% mineralization as measured by the decrease in the total organic content. Ion chromatography indicates that the only remaining components are oxalate, sulfate and nitrate ions.

Kinetics and mechanism of (•)OH mediated degradation of dimethyl phthalate in aqueous solution: experimental and theoretical studies.

The hydroxyl radical ((•)OH) is one of the main oxidative species in aqueous phase advanced oxidation processes, and its initial reactions with organic pollutants are important to understand the transformation and fate of organics in water environments. Insights into the kinetics and mechanism of (•)OH mediated degradation of the model environmental endocrine disruptor, dimethyl phthalate (DMP), have been obtained using radiolysis experiments and computational methods. The bimolecular rate constant for the (•)OH reaction with DMP was determined to be (3.2 ± 0.1) × 10(9) M(-1)s(-1). The possible reaction mechanisms of radical adduct formation (RAF), hydrogen atom transfer (HAT), and single electron transfer (SET) were considered. By comparing the experimental absorption spectra with the computational results, it was concluded that the RAF and HAT were the dominant reaction pathways, and OH-adducts ((•)DMPOH1, (•)DMPOH2) and methyl type radicals (•)DMP(-H)α were identified as dominated intermediates. Computational results confirmed the identification of transient species with maximum absorption around 260 nm as (•)DMPOH1 and (•)DMP(-H)α, and these radical intermediates then converted to monohydroxylated dimethyl phthalates and monomethyl phthalates. Experimental and computational analyses which elucidated the mechanism of (•)OH-mediated degradation of DMP are discussed in detail.

Hydroxyl radical-mediated advanced oxidation processes for textile dyes: a comparison of the radiolytic and sonolytic degradation of the monoazo dye Acid Orange 7

Acid Orange 7, a textile azo dye, has been partially mineralized and degraded using γ-radiolysis and sonolysis. These two different advanced oxidation processes (AOP) are effective in producing ⋅OH radicals and cause complete destruction of the chromophore. The reaction mechanism of dye degradation has been probed by analyzing the reaction products with HPLC. In both cases, the final end products of degradation are oxalate and formate ions. The intermediates observed are all similar. While hydroxybenzenesulfonic acid is the major observed reaction intermediate in the oxidation processes, the pulse radiolysis studies indicate that the OH radical initiated pathway for attack occurs via the initial formation of 1,2-naphthaquinone and subsequent breakdown into oxalic acid.

Studies in Radiation Chemistry: Application to Ozonation and Other Advanced Oxidation Processes

Advanced oxidation/reduction processes (AORPs) are an alternative water treatment that is becoming more widely utilized. Our radiation-chemistry based studies are being used to develop a fundamental understanding of AOP treatment options, and are divided into three complementary types of contaminants; disinfection by-products (DBPs), emerging pollutants of concern (EPoCs), and natural organic matter (NOM). More than 600 DBPs have been identified, and one class that appears to have severe potential adverse health effects is the halonitromethanes (HNMs). Of the nine HNMs, trichloronitromethane (chloropicrin) is the most common, with levels up to 180 nM in US drinking waters. EPoCs are of interest because of their biological activity at low concentrations in water and while the initial focus was on endocrine disruptor chemicals (EDCs) this class has now been expanded to include many other recalcitrant chemicals such as hormones, antibiotics, industrial contaminants, and health care products. Natural organic matter is one of the most common radical scavengers in natural waters and therefore may adversely affect AOPs. Our approach is to study NOM both directly and using model compounds thought to be representative of structural components of this complex material.

Effects of molecular ozone and hydroxyl radical on formation of N-nitrosamines and perfluoroalkyl acids during ozonation of treated wastewaters

N-Nitrosamines—toxic disinfection byproducts commonly associated with chloramination—have recently been shown to increase after ozonation of some surface waters and treated wastewaters. In addition to five nitrosamines, two perfluoroalkyl acids (PFAAs) are included in the most recent U.S. EPA Contaminant Candidate List due to potential public health risks. In this manuscript, the potential roles of molecular ozone (O3) and hydroxyl radical (˙OH) were investigated in the formation of N-nitrosamines and PFAAs in treated wastewaters. The results herein are based on controlled bench-scale experiments designed to isolate the effects of O3 with the use of t-butanol as a ˙OH scavenger. Nitrous oxide gas saturated samples were exposed to gamma radiation to isolate the effects of ˙OH, and para-chlorobenzoic acid was used to assess ˙OH exposure. This study found that the presence of molecular ozone versus the hydroxyl radical promoted N-nitrosodimethylamine (NDMA) formation. Six other N-nitrosamines showed very little or no formation upon the ozonation of six treated wastewaters up to an O3 : TOC ratio of 1.0. For PFAAs, perfluorohexanoic acid (PFHxA) formed the highest and most consistently upon ozonation (up to an O3 : TOC ratio of 2.0) of the same six treated wastewaters. Presence of molecular ozone (more so than hydroxyl radical), appears to promote the formation of PFHxA and perfluorobutane sulfonic acid (PFBS). The effect of pH in the range of 6–8 upon the formation of NDMA and PFAAs was found to be minimal. These findings provide new understanding of the formation of oxidation byproducts during ozonation of reclaimed wastewaters. Depending on future regulatory determinations, NDMA and a few PFAAs could be of concern for potable reuse treatment systems that employ ozone.

Prevalence of toxin-producing Clostridium botulinum associated with the macroalga Cladophora in three Great Lakes: growth and management

The reemergence of avian botulism caused by Clostridium botulinum type E has been observed across the Great Lakes in recent years. Evidence suggests an association between the nuisance algae, Cladophora spp., and C. botulinum in nearshore areas of the Great Lakes. However, the nature of the association between Cladophora and C. botulinum is not fully understood due, in part, to the complex food web interactions in this disease etiology. In this study, we extensively evaluated their association by quantitatively examining population size and serotypes of C. botulinum in algal mats collected from wide geographic areas in lakes Michigan, Ontario, and Erie in 2011-2012 and comparing them with frequencies in other matrices such as sand and water. A high prevalence (96%) of C. botulinum type E was observed in Cladophora mats collected from shorelines of the Great Lakes in 2012. Among the algae samples containing detectable C. botulinum, the population size of C. Botulinum type E was 10(0)-10(4) MPN/g dried algae, which was much greater (up to 10(3) fold) than that found in sand or the water column, indicating that Cladophora mats are sources of this pathogen. Mouse toxinantitoxin bioassays confirmed that the putative C. botulinum belonged to the type E serotype. Steam treatment was effective in reducing or eliminating C. botulinum type E viable cells in Cladophora mats, thereby breaking the potential transmission route of toxin up to the food chain. Consequently, our data suggest that steam treatment incorporated with a beach cleaning machine may be an effective treatment of Cladophora-borne C. botulinum and may reduce bird mortality and human health risks.

Virulence and biodegradation potential of dynamic microbial communities associated with decaying Cladophora in Great Lakes

Cladophora mats that accumulate and decompose along shorelines of the Great Lakes create potential threats to the health of humans and wildlife. The decaying algae create a low oxygen and redox potential environment favoring growth and persistence of anaerobic microbial populations, including Clostridium botulinum, the causal agent of botulism in humans, birds, and other wildlife. In addition to the diverse population of microbes, a dynamic chemical environment is generated, which involves production of numerous organic and inorganic substances, many of which are believed to be toxic to the sand and aquatic biotic communities. In this study, we used 16S-rDNA-based-amplicon sequencing and microfluidic-based quantitative PCR approaches to characterize the bacterial community structure and the abundances of human pathogens associated with Cladophora at different stages (up to 90days) of algal decay in laboratory microcosms. Oxygen levels were largely depleted after a few hours of incubation. As Cladophora decayed, the algal microbial biodiversity decreased within 24h, and the mat transitioned from an aerobic to anaerobic environment. There were increasing abundances of enteric and pathogenic bacteria during decomposition of Cladophora, including Acinetobacter, Enterobacter, Kluyvera, Cedecea, and others. In contrast, there were no or very few sequences (<0.07%) assigned to such groups in fresh Cladophora samples. Principal coordinate analysis indicated that the bacterial community structure was dynamic and changed significantly with decay time. Knowledge of microbial communities and chemical composition of decaying algal mats is critical to our further understanding of the role that Cladophora plays in a beach ecosystems structure and function, including the algal role in trophic interactions. Based on these findings, public and environmental health concerns should be considered when decaying Cladophora mats accumulate Great Lakes shorelines.

Hydroxyl Radical Probes for the Comparison of Secondary Treated Wastewaters

The majority of the wastewater treatment facilities in the United States treat to secondary treatment, as required by the Clean Water Act. However, because of the growing list of chemical pollutants commonly detected in treated wastewaters, advanced oxidation processes (AOPs) are finding application as treatment options. AOPs are defined by the use of the hydroxyl radicals as the major oxidant. For such applications to be cost-effective and optimized, a full understanding of the radical chemistry must be achieved. This chemistry can be complex, with both reactivity and efficiency of radical reactions strongly dependent upon the contaminants and overall water quality. In this work, the degradation efficiencies of two probe molecules, caffeine and sulfamethoxazole, were studied in secondary treated wastewaters from Southern California and Northwest Indiana. These radical efficiencies showed significant differences; therefore, further solution modifications, kinetic radical scavenging, and production measurements were performed to elucidate the causes of these differences.

Analytical Measurements to Improve Nonpoint Pollution Assessments in Indiana's Lake Michigan Watershed

The Salt Creek watershed in Porter County, Indiana, is a subwatershed within the Little Calumet-Galien watershed, the only one in Indiana that discharges to Lake Michigan. The state-approved watershed management plan for Salt Creek requires monthly measurements of general chemistry parameters, discharge, turbidity, and Escherichia coli concentrations from May to October. This pilot study was designed to utilize the strengths of the watershed management component in combination with research science measurements and analyses, to assess the nonpoint sources of pollution more accurately. The outcomes of the first-year study, which focused on dissolved anions, fluorescent whitening agents (FWAs), total suspended solids and discharge loads from September 2010 through April 2011, demonstrate the substantial increase in comprehension gained from such partnerships. While basic measurements of pH, dissolved oxygen, and other parameters offer an idea of the waterways health, the chloride, nitrate, and total suspended solids (TSS) loads showed significant seasonal stresses; and the chloride and nitrate concentrations provided insights into specific nonpoint pollution sources.

Can Incongruent Studies Effectively Characterize Long-Term Water Quality?

Abstract Science-based measurements and studies are vital for the protection of freshwater resources, systems, and habitats. Scientists are trained to plan and implement projects to address environmental and public health challenges such as water quality problems. The most successful programs for public benefit require coordination between experienced scientists, resource managers, and interested citizens and include long-term goals. For the assessment and protection of resources, scientists should be assigned prominent roles, and administrators and others should utilize their strengths to avoid fragmented data collections, irregularities in measurements and follow-up, or abandonment of final objectives. The requirements for useful water quality monitoring projects are addressed in the context of the watershed management plans in the state of Indiana, with a focus on the Salt Creek watershed in Northwest Indiana, which drains into Lake Michigan.