The presence of pharmacologically active and persistent compounds in drinking water sources is an environmental and public health concern. Sources of pharmaceuticals in the aquatic environment include wastewater treatment plant effluents and veterinary use. Antibiotics are of special concern because of their role in the spread of bacterial resistance. Conventional drinking water treatment processes are often ineffective for removing trace organic contaminants. Ozonation processes have demonstrated the ability to remove pharmaceutical compounds from drinking water supplies. During the ozonation of drinking water, the primary oxidants are ozone and hydroxyl radicals formed during the decomposition of ozone. Both oxidants contribute to the removal of pharmaceutical compounds; however, the relative rates of destruction by these two oxidants depends on the treatment operating conditions, the background water chemistry and the structure and reactivity of the target compound. This study investigated the relative impact of natural water characteristics, such as pH, the carbonate system, and natural organic matter, on the removal of the fluoroquinolone antibiotic ciprofloxacin by ozonation processes. Rate constants for k"O3, Cip obtained at pH 7 were approximately one order of magnitude higher than at pH 5 because ciprofloxacin changes from a positively charged cation to a neutral species over this pH range. The results showed that there was very little variation of the rate constants for ciprofloxacin oxidation by O₃ or hydroxyl radicals regardless of the carbonate concentration or the presence of the two organic matters studied in this research. Typical values for k"O3, Cip and k"HO°, Cip obtained at pH 7 ranged between 1.49x10⁴ and 1.64x10⁴ M⁻¹s⁻¹ and 1.29x10¹⁰ to 1.80x10¹⁰ M⁻¹s⁻¹, respectively. However, the presence of carbonate and other hydroxyl radical scavengers did have an impact on O₃ and hydroxyl radical exposure. The relative impact of these two oxidants changed depending on the pH of the system and the presence of carbonate and natural organic matter. / text

Anthropogenically-derived substances, including pharmaceuticals and personal care products, endocrine-disrupting chemicals, and pesticides, are increasingly being detected in drinking water supplies and wastewater effluents. Concerns over the presence of these compounds in water supplies include their ability to impart toxicological activity, their capacity to spread antibiotic resistance, and their potential to affect cell-signaling processes. For these reasons, water treatment processes geared towards removal of these trace organic contaminants are vital. In this work, ozone was used to treat four pharmaceutical contaminants: ciprofloxacin, cyclophosphamide, erythromycin, and ifosfamide. Ciprofloxacin and erythromycin are antibiotic/antimicrobial compounds, and cyclophosphamide and ifosfamide are chemotherapy agents. Ozone effectively transformed all four pharmaceuticals, even in the presence of background natural organic matter, which exerts a considerable ozone demand. The apparent rate constants for the reaction of the pharmaceuticals with ozone at pH 7 were determined: 3.03 M-1s-1 for cyclophosphamide; 7.38 M-1s-1 for ifosfamide; 1.57×104 M-1s-1 for ciprofloxacin; and 7.18×104 M-1s-1 for erythromycin. Cyclophosphamide and ifosfamide, which do not react quickly with ozone, exhibited high rate constants (2.7×109 M-1s-1) for transformation by hydroxyl radicals, which are formed through ozone decomposition. Nevertheless, complete removal of cyclophosphamide and ifosfamide was achievable using a novel continuous aqueous ozone addition reactor and an ozone-based advanced oxidation process (peroxone). In ozone-based processes, pharmaceuticals are systematically transformed via complex oxidative pathways towards CO2, H2O, and the oxidized forms of other elements. Intermediate oxidation products containing oxygen atoms or hydroxyl groups substituted into the chemical structure of the parent pharmaceutical were identified using liquid chromatography-mass spectrometry (LC-MS). Given the structural similarity of intermediate oxidation products to the parent pharmaceuticals, an antimicrobial activity assay was employed to monitor the removal of pharmacological activity associated with ciprofloxacin, erythromycin, and their respective intermediate oxidation products throughout treatment. For solutions containing ciprofloxacin or erythromycin, ozone was able to completely eliminate the corresponding antimicrobial activity. Ciprofloxacin intermediate oxidation products were pharmacologically active; however, erythromycin’s intermediate products did not contribute to the residual antimicrobial activity. These results suggest that the design of conventional and advanced ozone-based processes must incorporate ozone demand from background organic matter and account for destruction of pharmacologically active intermediates. / text

Natural organic matter (NOM) occurs ubiquitously in drinking water supplies and is problematic since it serves as a precursor to disinfection by-products (DBPs) formation. Stricter DBP regulations will drive utilities to consider advanced treatment processes for DBP control through NOM removal. Herein, the transformation of NOM in homogeneous (UVA/H2O2 and UVA/Fe/H2O2) and heterogeneous (UVA/TiO2) Advanced Oxidation Processes (AOPs) were studied. Organic matter from three different sources was investigated in this work, specifically a commercial humic acid, and two Australian surface water sources. The transformation of the organic matter as a result of oxidation was investigated through multiple analytical techniques, such as UV-Vis spectroscopy, DOC analysis, high performance size exclusion chromatography (HPSEC), resin fractionation, liquid chromatography with organic carbon detection (LC-OCD) and disinfection byproducts formation potential. The multi-analysis approach is required due to the complex and heterogeneous nature of NOM. Each analytical technique provides complementary information on different properties of NOM, leading to a comprehensive understanding on how AOPs transform the chemical and physical properties of NOM. Both homogeneous and heterogeneous AOPs were found to be effective for NOM removal. However, complete mineralisation was not achieved, even under prolonged irradiation. Large aromatic and hydrophobic organics were degraded into lower molecular weight hydrophilic compounds, which had weak UV absorbance at 254 nm. In the UVA/TiO2 treatment, multi-wavelength HPSEC analysis demonstrated the formation of low molecular weight compounds with strong absorbance at wavelength lower than 230 nm. These residual organic compounds, though recalcitrant, had a low reactivity to chlorine to form THMs, and were identified to be low molecular weight acids and neutral compounds from LC-OCD analysis. Finally, the current work reports the novel synthesis of magnetic photocatalyst for NOM oxidation from low cost precursors to solve the separation problem of nano-sized particles. Magnetite particles were coated with a layer of protective silica from sodium silicate precursor. Photoactive titanium dioxide was then deposited onto the silica coated particles using titanium tetrachloride precursor. The as-prepared magnetic photocatalyst exhibited excellent stability and durability. Although the photoactivity of the magnetic photocatalyst is lower than commercial TiO2 photocatalyst, it can be easily recovered by magnetic field.

A variety of approaches were conducted to obtain a comprehensive understanding of the adsorption of Natural Organic Matter (NOM) isolates on metal oxides (MeO). Adsorption experiments with a series of small molecular weight (MW), oxygenated, aromatic organic acids were performed with Aluminum oxide (Al2O3), Titanium oxide (TiO2), and Zirconium oxide (ZrO2) surface. The experiments were conducted in batch mode at pH 4.2 and 7.6. The adsorption of simple organic acids was described by Langmuir model, and exhibited strong dependence on the relative abundance of carboxyl group, aliphaticity/aromaticity, length of alkyl chain, and the presence of hydroxyl group. The adsorption of the model compounds was high at low pH and decreased with increasing the pH. Isolated NOM fraction of strong humic character, i.e., hydrophobic (HPO) (high in MW, aromaticity, and acidity), i.e., Suwannee River fulvic acid (SRW HPO), showed strong adsorption on all MeO. However, fractions with similar acidic character, and lower MW exerted weak adsorption. NOM fraction that incorporated polysaccharides and proteins like structures (i.e., biopolymers) was not significantly adsorbed compared to HPO fractions. Interestingly, biopolymer adsorption on Heated Aluminum oxide particles (HAOP) was higher than that on Al2O3, TiO2, and ZrO2. These different adsorption profiles were related to their physicochemical characteristics of NOM and MeO, and thus, showed different interacting mechanisms and were studied by Atomic Force Microscopy (AFM). Hydrogen bonding was suggested as the main mechanism between NOM of strong hydrophilic character (i.e., biopolymers) and Al2O3, TiO2 and ZrO2 coated wafers. The strength of the hydrogen bonding was influenced by the hydrophilicity degree of MeO surface, ionic strength, and cation type. NOM fractions with strong humic character showed repulsive forces that are electrostatic in nature with MeO of high negative charge density. Hydrogen bonding and ligand exchange mechanisms are proposed to control the adsorption mechanism at high ionic strength with less negatively-charged MeO surface. Strong interactions forces was recorded between NOM molecules with different properties, more specifically with high MW humic and non humic fractions. These forces are controlled by cation type, and NOM chemical structure.

Ceramic membranes offer more advantageous performances than conventional polymeric membranes. However, membrane fouling caused by Natural Organic Matters (NOM) contained in the feed water is still become a major problem for operational efficiency. A new method of ceramic membrane pre-coating with Powdered Activated Carbon (PAC), which allows extremely contact time for adsorbing aquatic contaminants, has been studied as a pre-treatment prior to ceramic microfiltration membrane. This bench scale study evaluated five different types of PAC (SA Super, G 60, KCU 6, KCU 8 and KCU 12,). The results showed that KCU 6 with larger pore size was performed better compared to other PAC when pre-coated on membrane surface. PAC pre-coating on the ceramic membrane with KCU 6 was significantly enhance NOM removal, reduced membrane fouling and improved membrane performance. Increase of total membrane resistance was suppressed to 96%. The removal of NOM components up to 92%, 58% and 56% for biopolymers, humic substances and building blocks, respectively was achieved at pre-coating dose of 30 mg/l. Adsorption was found to be the major removal mechanism of NOM. Results obtained showed that biopolymers removal are potentially correlated with enhanced membrane performance.

The Chlorine-Ammonia Process was developed recently as a preoxidation process to minimize the formation of bromate during ozonation of the waters containing a significant bromide concentration. Chlorine is added first, followed by ammonia 5-10 minutes later, with the goal of sequestering bromide in monobromamine before the subsequent ozonation step. The goal of this research was to improve the Chlorine-Ammonia Process by introducing a very short prechlorination step (i.e., 30 seconds before addition of ammonia) to minimize overall disinfection by-product formation. Also, in this strategy, formation of a powerful halogenating agent, HOBr, is minimized and bromochloramine (NHBrCl) is used predominantly instead of monobromamine to sequester bromide during ozonation. To support this improved approach to bromide sequestration, this study examined the formation and decay of bromochloramine as a function of operating conditions, such as pH and Cl2/N ratio, and refined a chemical kinetic model to predict haloamine concentrations over time. Two natural organic matter (NOM) sources were used in this study (Lake Austin, Texas and Claremore Lake, Oklahoma) to study the effect of NOM on monochloramine and total chlorine decay after 30 seconds of prechlorination. The rate of the reaction between haloamines and fast and slow sites on the NOM was estimated. A kinetics model was developed to model total chlorine decay after a short prechlorination time. The model is based on the Unified Haloamine Kinetic Model developed by Pope (2006). Pope`s model failed to model the initial monochloramine concentration after 30 seconds prechlorination time as well as the monochloramine and total chlorine decay over time. The modified model shows an excellent prediction of monochloramine and total chlorine decay after 30 seconds prechlorination time at pH range of 6.5-8.0 and over a carbonate buffer concentration range of 2-10 mM. The model includes a new bromochloramine decay scheme via the reaction with monochloramine and with itself. In addition, new rate constants for the reaction of HOCl with bromide ion and reaction of HOBr with monochloramine were added. The hypobromous acid formation rate was found to be an acid-catalyzed reaction, which confirms the finding of Kumar et al. (1987). A new value of the acid catalysis effect of hydrogen ion was estimated. New terms were introduced to the hyprobromous acid formation rate including the acid catalysis effect of bicarbonate, carbonic acid, and ammonium ion. In addition, the reaction of HOBr with monochloramine to form bromochloramine was found to be an acid-catalyzed reaction, and a new value of the rate constant was estimated. / text

The dissolved air flotation (DAF) has been used in drinking water treatment for its excellent algae and natural organic matter (NOM) removal. DAF drinking water treatability test are often conducted in a DAF jar test apparatus. Although, DAF jar test studies showed that they were able to predict NOM removals at full-scale facilities well, they have not always been successful in predicting the turbidity removals. One possible reason of the DAF jar test inaccuracy results could be associated to the small jar diameter, which may create wall effects. Therefore, the first two objectives of this research are: a) to develop and test a new, larger diameter and larger volume batch bench-scale dissolved air flotation system (LB-DAF) to better simulate turbidity removals in drinking water applications; b) to confirm these results by comparing the LB-DAF and full-scale DAF turbidity removals for two other source waters. The raw water characteristics of the three plants were quite different and the testing was performed at different times of the year. The development/optimization of the LB-DAF evaluated the impact of different variables (i.e., mixing intensity, water depth/tank diameter ratio, impeller shape, saturator pressure and recycle ratio). The results showed that the LB-DAF predicted well the full-scale DAF turbidity removals at three water treatment plants, and these predictions were better than those of DAF jar tests. For the LB-DAF design and operational variables evaluated had a limited impact on the turbidity removals. The LB-DAF predicted well DAF full-scale turbidity removals regardless of water temperature. This is an indication of the robustness of the DAF system. Ballasted sedimentation (BS) is a compact coagulation/flocculation and sedimentation process combination that has become very popular because it is very compact and because it can handle large variations in raw water turbidity and NOM. The literature survey did not initially identify studies on the BS treatment of algal impacted waters, for which DAF is considered particularly suitable. Thus, the third main objective of this dissertation was to compare the efficiency of BS with that conventional gravity settling (CGS), and that of DAF for the treatment of an algal impacted water via jar tests. These comparisons were performed at the Belleville Water Treatment Plant using Bay of Quinte water, one of the most eutrophic zones of Lake Ontario. Unfortunately, a change of weather prior to the testing resulted in raw water samples with relatively low concentrations of algae and cyanobacteria. The testing showed that DAF and BS had very similar NOM, cyanobacteria/algae (chlorophyll a and phycocyanin) removals.; however, the BS required microsand addition, polymer addition and a slightly higher alum dose. Only for turbidity removal the DAF was somewhat superior. It is suggested that these comparison experiments be repeated with waters that are more impacted by algae and cyanobacteria.

Nanoparticles have gained growing attention of the scientific community over the past few decades due to their high potential to be used in diverse industrial applications. Nanoparticles often possess superior characteristics, such as catalytic activity, photochemical activity, and mechanical strength, compared to their bulk counterparts, making them more desirable in different industrial applications. During the past few decades, the use of the nanoparticles in various industries has been increased. With increasing usage release of nanoparticles into the environment has also increased. There is a growing concern about the nanoparticle toxicity and numerous studies have shown the toxic effects of different nanoparticles on various plants, animals, and microorganisms in the environment. Toxicity of nanoparticles is often attributed to their morphology and their ability to undergo different transformations in the environment. These transformations include aggregation, dissolution, and surface adsorption. Natural organic matter (NOM) are the most abundant natural ligands in the environment which include Humic acid and Fulvic acid. These high molecular weight organic molecules have complex structures and contain many different functional groups such as carboxylic acid groups, hydroxyl, amino and phenolic groups that can interact with the nanoparticle surface. The nature and the intensity of the interaction are dependent on several factors including the size and the surface functionality of nanoparticles and pH of the medium. The smaller the nanoparticle, the higher the adsorption of NOM due to the high surface to volume ratio of smaller particles. Functional groups on the surface dictate the surface charge of the nanoparticles in water depending on the acidity. The higher the acidity, higher the adsorption of NOM due to increased electrostatic attractions between positively charged nanoparticles and the negatively charged NOM molecules. Adsorbed NOM on nanoparticles affect the other transformations such as aggregation and dissolution and can in turn alter the reactivity and toxicity of the nanoparticles. Therefore, effect of NOM is an important factor that should be considered in environmental toxicity related studies of nanoparticles.

Zinc deficient soils, or soils with low Zn bioavailability, are widespread, which exacerbates Zn deficiency in human as crops grown on these soils have low Zn content. Often crop yields are also compromised. Fertilizers based on soluble Zn salts often have limited efficacy in such soils. In this research, we evaluate the performance of polymer coated and bare ZnO nanoparticles (NPs) in an attempt to overcome limitations of soluble Zn salts in alkaline soils. We first synthesized 20-30 nm bare ZnO NPs with different surface chemistries to impart colloidal stability to the particles. Bare ZnO were treated in phosphate solution under certain conditions leading to the formation of a core made of ZnO NPs that is covered by a shell of amorphous Zn3(PO4)2 (core-shell NPs). This confers a negative charge to the particles over a wide pH range. The addition of nonionic (neutral dextran) and polyelectrolyte (negatively charged dextran sulfate (DEX(SO4)) during the synthesis resulted in the formation of DEX and DEX(SO4) ZnO NPs. Dextran has a minimal effect on the surface charge of ZnO but dextran sulfate confers a net negative charge. Bare and core-shell ZnO NPs were both electrostatically stabilized whereas DEX and DEX(SO4) ZnO NPs were sterically and electrosterically stabilized, respectively. We investigated the effect of treating seeds with ZnO NPs on the growth and accumulation of Zn in wheat (Triticum aestivum) seedlings in comparison to ZnSO4. All ZnO NPs stimulated seedling growth. Seedlings accumulated higher Zn concentrations when treated with ZnO NPs than with ZnSO4. Zinc sulfate was toxic even at the lower exposure concentrations, which was demonstrated by significantly lower germination success and seedling growth. In the second experiment, we investigated the effect of pH on the attachment and dissolution of ZnO NPs in soil, as compared to ZnSO4. Soil pH was adjusted to 6 and 8, then the soil was spiked with 100 mg Zn/kg soil in the form of ZnSO4, bare, DEX, DEX(SO4), and core-shell ZnO NPs. The results showed that DEX and core-shell ZnO NPs had significantly higher total Zn in soil solution compared to ZnSO4 at pH 8, with little dissolution. Dissolved Zn was similar among treatments except ZnSO4 at pH 6, indicating little dissolution of the ZnO NPs at either pH value. We also found that the engineered coatings dictate the behavior of the particles in simple aqueous systems, but their properties are altered in natural soil solutions because of the dominant effect of natural organic matter (NOM) on their surface chemistry. Based on the outcomes of the previous two experiments, we selected DEX and bare ZnO NPs to test the efficacy of ZnO NPs in delivering Zn to the grain of wheat under greenhouse conditions. We performed two independent studies where seeds were either treated with the NPs or grown in a soil spiked with Zn at pH 6 and 8 and spiked with Zn treatments (nano and ionic). We found that treating seeds with bare ZnO NPs significantly enhanced grain Zn concentrations as compared to the control, DEX-ZnO NPs, and ZnSO4. There were no differences in grain Zn concentration of plants treated with ionic or nano Zn treatments regardless of the soil pH. This work has elucidated important principles which will help carry forward efforts at developing effective ZnO NP-based fertilizers. It also suggests that treatment of seeds with ZnO NPs is more effective than amending soil or treating seeds with ZnSO4.

The association between natural organic matter (NOM) and iron (Fe) minerals was widely found in soil and sediments and has been shown to impact the fate of Fe minerals and NOM. Ferrihydrite, a ubiquitous Fe mineral, serves as important sink for NOM and rapidly transforms to secondary Fe minerals in the presence of Fe(II). The associated NOM has been found to influence the Fe(II)-catalyzed ferrihydrite transformation pathway, but it remains unclear how various NOM affects this transformation and the implication. This study specifically investigates how different species of NOM affect Fe(II)-catalyzed ferrihydrite transformation under different C/Fe ratios. A series of Fe isotope tracer experiments were conducted to measure Fe atom exchange and electron transfer between aqueous Fe(II) and ferrihydrite in the presence of diverse NOM species. The fate of Ni during Fe(II)-catalyzed transformation of NOM-Fh coprecipitate was also investigated. Ferrihydrite was found less susceptible to Fe(II)-catalyzed transformation with increasing C/Fe ratio and fulvic acids and Suwannee River NOM (SRNOM) in the coprecipitates need lower C/Fe ratio than humic acids to completely inhibit formation of secondary Fe minerals. At C/Fe ratios where ferrihydrite transformed to secondary minerals, goethite was dominant in ferrihydrite coprecipitated with humic acids, whereas lepidocrocite was favored in ferrihydrite coprecipitated with fulvic acids and SRNOM. Adsorbed SRNOM may be more inhibitive than coprecipitated SRNOM on Fe(II)-catalyzed ferrihydrite transformation under similar C/Fe ratios. Despite no secondary mineral transformation at high C/Fe ratios, Mössbauer spectra indicated electron transfer still occurred between Fe(II) and ferrihydrite coprecipitated with fulvic acid and SRNOM. In addition, isotope tracer experiments revealed that a significant fraction of structural Fe(III) in the ferrihydrite mixed with the aqueous phase Fe(II) (~85%). After reaction with Fe(II), Mössbauer spectroscopy indicated some subtle changes in the crystallinity, particle size or particle interactions in the coprecipitate. The effect of coprecipitated SRNOM on Ni(II) distribution during Fe(II)-catalyzed ferrihydrite transformation was investigated with adsorbed Ni(II) and coprecipitated Ni(II). Ni(II) adsorbed on ferrihydrite was more resistant to acid extraction after Fe(II)-catalyzed transformation and suggested that structural incorporation of Ni into secondary Fe minerals occurred. With coprecipitated SRNOM, ferrihydrite did not transform to secondary minerals in the presence of Fe(II) but extensive Fe atom exchange between aqueous Fe(II) and structural Fe(III) still occurred. Limited change in Ni stability was observed, suggesting there was only small portion of Ni redistributed in the presence of Fe(II). Pre-incorporated Ni(II) in Ni-SRNOM-Fh coprecipitate was partially released (6-8 %) in the presence of Fe(II), but the distribution of remaining Ni(II) in the solid did not change measurably. Our observation suggests that the presence of SRNOM limited the redistribution of Ni most likely because of limited transformation of ferrihydrite to secondary minerals.