William J. Cooper

Taking the “Waste” Out of “Wastewater” for Human Water Security and Ecosystem Sustainability

Humans create vast quantities of wastewater through inefficiencies and poor management of water systems. The wasting of water poses sustainability challenges, depletes energy reserves, and undermines human water security and ecosystem health. Here we review emerging approaches for reusing wastewater and minimizing its generation. These complementary options make the most of scarce freshwater resources, serve the varying water needs of both developed and developing countries, and confer a variety of environmental benefits. Their widespread adoption will require changing how freshwater is sourced, used, managed, and priced.

Degradation of tetracycline antibiotics: Mechanisms and kinetic studies for advanced oxidation/reduction processes

This study involves elucidating the destruction mechanisms of four tetracyclines via reactions with ()OH and solvated electrons (e(aq)(-)). The first step is to evaluate the bimolecular rate constants for the reaction of ()OH and e(aq)(-). Transient absorption spectra for the intermediates formed by the reaction of ()OH were also measured over the time period of 1-250micros to assist in selecting the appropriate wavelength for the absolute bimolecular reaction rate constants. For these four compounds, tetracycline, chlortetracycline, oxytetracycline, and doxycycline, the absolute rate constants with ()OH were (6.3+/-0.1)x10(9), (5.2+/-0.2)x10(9), (5.6+/-0.1)x10(9), and (7.6+/-0.1)x10(9) M(-1) s(-1), and for e(aq)(-) were (2.2+/-0.1)x10(10), (1.3+/-0.2)x10(10), (2.3+/-0.1)x10(10), and (2.5+/-0.1)x10(10) M(-1) s(-1), respectively. The efficiencies for ()OH reaction with the four tetracyclines ranged from 32% to 60%. The efficiencies for e(aq)(-) reaction were 15-29% except for chlortetracycline which was significantly higher (97%) than the other tetracyclines in spite of the similar reaction rate constants for e(aq)(-) in all cases. To evaluate the use of advanced oxidation/reduction processes for the destruction of tetracyclines it is necessary to have reaction rates, reaction efficiencies and destruction mechanisms. This paper is the first step in eventually realizing the formulation of a detailed kinetic destruction model for these four tetracycline antibiotics.

Photocatalytic degradation kinetics and mechanism of environmental pharmaceuticals in aqueous suspension of TiO2: A case of β-blockers

This study investigated the photocatalytic degradation of three beta-blockers in TiO(2) suspensions. The disappearance of the compounds followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model and the rate constants were 0.075, 0.072 and 0.182 min(-1) for atenolol, metoprolol and propranolol, respectively. After 240 min irradiation, the reaction intermediates were completely mineralized to CO(2) and the nitrogen was predominantly as NH(4)(+). The influence of initial pH and beta-blocker concentration on the kinetics was also studied. From adsorption studies it appears that the photocatalytic degradation occurred mainly on the surface of TiO(2). Further studies indicated that surface reaction with OH radical was principally responsible for the degradation of these three beta-blockers. The major degradation intermediates were identified by HPLC/MS analysis. Cleavage of the side chain and the addition of the hydroxyl group to the parent compounds were found to be the two main degradation pathways for all three beta-blockers.

Methods for reactive oxygen species (ROS) detection in aqueous environments

This review summarizes direct and indirect analytical methods for the detection and quantification of the reactive oxygen species (ROS): 1O2, O2·−/HOO·, H2O2, HO·, and CO3·− in aqueous solution. Each section briefly describes the chemical properties of a specific ROS followed by a table (organized alphabetically by detection method, i.e., absorbance, chemiluminescence, etc.) summarizing the nature of the observable (associated analytical signal) for each method, limit of detection, application notes, and reaction of the probe molecule with the particular ROS.

Photosensitized degradation of amoxicillin in natural organic matter isolate solutions.

Amoxicillin is a widely used antibiotic and has been detected in natural waters. Its environmental fate is in part determined by hydrolysis, and, direct and indirect photolysis. The hydrolysis rate in distilled water and water to which five different isolated of dissolved organic matter (DOM) was added, were evaluated. In the five different DOM solutions hydrolysis accounted for 5-18% loss of amoxicillin. Direct and indirect photolysis rates were determined using a solar simulator and it appeared that indirect photolysis was the dominant loss mechanism. Direct photolysis, in a solar simulator, accounted for 6-21% loss of amoxicillin in the simulated natural waters. The steady-state concentrations of singlet oxygen, (1)ΔO(2) (∼10(-13) M) and hydroxyl radical, •OH (∼10(-17) M) were obtained in aqueous solutions of five different dissolved organic matter samples using a solar simulator. The bimolecular reaction rate constant of (1)ΔO(2) with amoxicillin was measured in the different solutions, k(ΔO(2)) = 1.44 × 10(4) M(-1) s(-1). The sunlight mediated amoxicillin loss rate with (1)ΔO(2) (∼10(-9) s(-1)), and with •OH (∼10(-7) s(-1)), were also determined for the different samples of DOM. While (1)ΔO(2) only accounted for 0.03-0.08% of the total loss rate, the hydroxyl radical contributed 10-22%. It appears that the direct reaction of singlet and triplet excited state DOM ((3)DOM(∗)) with amoxicillin accounts for 48-74% of the loss of amoxicillin. Furthermore, the pseudo first-order photodegradation rate showed a positive correlation with the sorption of amoxicillin to DOM, which further supported the assumption that excited state DOM∗ plays a key role in the photochemical transformation of amoxicillin in natural waters. This is the first study to report the relative contribution of all five processes to the fate of amoxicillin in aqueous solution.

Degradation of diclofenac by advanced oxidation and reduction processes: kinetic studies, degradation pathways and toxicity assessments.

Many pharmaceutical compounds and metabolites are found in surface and ground waters suggesting their ineffective removal by conventional wastewater treatment technologies. Advanced oxidation/reduction processes (AO/RPs), which utilize free radical reactions to directly degrade chemical contaminants, are alternatives to traditional water treatment. This study reports the absolute rate constants for reaction of diclofenac sodium and model compound (2, 6-dichloraniline) with the two major AO/RP radicals: the hydroxyl radical (•OH) and hydrated electron (e(aq)(-)). The bimolecular reaction rate constants (M(-1) s(-1)) for diclofenac for •OH was (9.29 ± 0.11) × 10(9), and for e(-)(aq) was (1.53 ± 0.03) ×10(9). To provide a better understanding of the decomposition of the intermediate radicals produced by hydroxyl radical reactions, transient absorption spectra are observed from 1 - 250 μs. In addition, preliminary degradation mechanisms and major products were elucidated using (60)Co γ-irradiation and LC-MS. The toxicity of products was evaluated using luminescent bacteria. These data are required for both evaluating the potential use of AO/RPs for the destruction of these compounds and for studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime.

Degradation mechanisms and kinetic studies for the treatment of X-ray contrast media compounds by advanced oxidation/reduction processes

The presence of iodinated X-ray contrast media compounds (ICM) in surface and ground waters has been reported. This is likely due to their biological inertness and incomplete removal in wastewater treatment processes. The present study reports partial degradation mechanisms based on elucidating the structures of major reaction by-products using gamma-irradiation and LC-MS. Studies conducted at concentrations higher than observed in natural waters is necessary to elucidate the reaction by-product structures and to develop destruction mechanisms. To support these mechanistic studies, the bimolecular rate constants for the reaction of OH and e(-)(aq) with one ionic ICM (diatrizoate), four non-ionic ICM (iohexol, iopromide, iopamidol, and iomeprol), and the several analogues of diatrizoate were determined. The absolute bimolecular reaction rate constants for diatrizoate, iohexol, iopromide, iopamidol, and iomeprol with OH were (9.58 +/- 0.23)x10(8), (3.20 +/- 0.13)x10(9), (3.34 +/- 0.14)x10(9), (3.42 +/- 0.28)x10(9), and (2.03 +/- 0.13) x 10(9) M(-1) s(-1), and with e(-)(aq) were (2.13 +/- 0.03)x10(10), (3.35 +/- 0.03)x10(10), (3.25 +/- 0.05)x10(10), (3.37 +/- 0.05)x10(10), and (3.47 +/- 0.02) x 10(10) M(-1) s(-1), respectively. Transient spectra for the intermediates formed by the reaction of OH were also measured over the time period of 1-100 micros to better understand the stability of the radicals and for evaluation of reaction rate constants. Degradation efficiencies for the OH and e(-)(aq) reactions with the five ICM were determined using steady-state gamma-radiolysis. Collectively, these data will form the basis of kinetic models for application of advanced oxidation/reduction processes for treating water containing these compounds.

Trimethoprim: kinetic and mechanistic considerations in photochemical environmental fate and AOP treatment.

Trimethoprim (TMP), a bacteriostatic antibiotic, has recently been detected in wastewater and surface waters. In this study the sunlight mediated photochemical fate, and treatment using advanced oxidation and reduction (free radical) processes, have been investigated with respect to their effect on TMP. Photochemical fate, in the presence of humic acid, and advanced oxidation treatment both involve the hydroxyl radical (OH) as one of the reactive species of interest. Another reactive oxygen species, singlet oxygen (1O2), may also be important in the photochemical fate of TMP. The bimolecular reaction rate constants of TMP with 1O2 and OH were evaluated to be (3.2±0.2)×10(6) M(-1) s(-1) and 8.66×10(9) M(-1) s(-1), respectively. The reaction kinetics for the sub-structural moieties of TMP, 1,2,3-trimethoxybenzene (TMBz) and 2,4-diaminoprimidine (DAP), was evaluated to facilitate an understanding of the loss mechanisms. For TMBz and DAP the reaction rate constants with 1O2 were <1.0×10(4) and (3.0±0.1)×10(6) M(-1) s(-1), while with OH they were 8.12×10(9) and 1.64×10(9) M(-1) s(-1), respectively. The data suggests that the 1O2 attacks the DAP and the OH radical attacks the TMBz moiety. However, for TMP, 1O2 and OH reactions accounted for only ∼19% and ∼6%, of its total photodegradation, respectively. Therefore, the reaction of TMP with excited state natural organic matter is postulated as a significant degradation pathway for the loss of TMP in sunlit waters containing natural organic matter. There was no effect of pH on the direct or indirect photolysis of TMP. To complete the study for reductive treatment processes, the solvated electron reaction rates for the destruction of TMP, TMBz and DAP were also evaluated. The absolute bimolecular reaction rates obtained were, (13.6±0.01)×10(9), (6.36±0.11)×10(7) and (10.1±0.01)×10(9) M(-1) s(-1), respectively.

Molecular characterization of effluent organic matter identified by ultrahigh resolution mass spectrometry

Effluent dissolved organic matter (EfOM) collected from the secondary-treated wastewater of the Orange County Sanitation District (OCSD) located in Fountain Valley, California, USA was compared to natural organic matter collected from the Suwannee River (SRNOM), Florida using ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Furthermore, the two different treatment processes at OCSD, activated sludge and trickling filter, were separately investigated. The blend of these two effluents was further evaluated after it had passed through the microfiltration process of the Advanced Water Purification Facility (AWPF) at Orange County Water District (OCWD). EfOM contained 872 different m/z peaks that were unambiguously assigned to exact molecular formulae containing a single sulfur atom and carbon, hydrogen and oxygen atoms (CHOS formulae). In contrast, the SRNOM sample only contained 152 CHOS formulae. The trend in CHO molecular compositions was opposite with 2500 CHO formulae assigned for SRNOM but only about 1000 for EfOM. The CHOS-derived mass peaks with highest abundances in EfOM could be attributed to surfactants such as linear alkyl benzene sulfonates (LAS), their co-products dialkyl tetralin sulfonates (DATS) and their biodegraded metabolites such as sulfophenyl carboxylic acids (SPC). The differences between the treatments were found minor with greater differences between sampling dates than treatment methods used.

Photochemical fate of atorvastatin (lipitor) in simulated natural waters

Cholesterol-lowering statin drugs are among the most frequently prescribed for reducing human blood cholesterol and they have been detected as contaminants in natural waters. In this study the photochemical behavior of atorvastatin (lipitor) was investigated at two different concentrations of 35.8 μM (20 mg L(-1)) and 35.8 nM (20 μg L(-1)) using a solar simulator and a UV reactor. Photochemical fate in natural waters can be described in most cases by the sum of the loss due to hydrolysis, direct photolysis, and, reaction with hydroxyl radical (•OH), singlet oxygen ((1)O(2)) (or O(2) ((1)D)), and excited state dissolved organic matter (DOM). The absolute bimolecular reaction rate constant with OH was measured, using pulsed radiolysis, (1.19 ± 0.04) × 10(10) M(-1) s(-1). The reaction rate constant of (1)O(2) was determined to be (3.1 ± 0.2) × 10(8) M(-1) s(-1). Under the experimental conditions used, at high atorvastatin concentration (35.8 μM) the contribution of singlet oxygen ((1)O(2)) to the photodegradation of atorvastatin in natural waters was higher than that of hydroxyl radical, and accounted for up to 23% of the loss in aqueous solutions. Whereas, at a concentration of 35.8 nM, (1)O(2) (and •OH) both played a minor role in the removal of this compound. Lastly, it also appears that atorvastatin reacts with (3)DOM* contributing to its loss in simulated natural waters.