The physicochemical properties and chemical reactivity of dissolved organic matter (DOM) are of tremendous practical significance in both natural and engineered aquatic and terrestrial systems. DOM is frequently extracted, fractionated, and concentrated from environmental samples using a variety of operationally defined physical and chemical processes in order to facilitate study of specific physicochemical properties and aspects of its chemical reactivity. This study was conducted to systematically examine the influence of operationally defined physical and chemical characterization methods on observed DOM physicochemical properties and reactivity with aqueous chlorine. The effects of chemical separation were evaluated by applying an existing resin adsorption based procedure which simultaneously extracts and fractionates DOM and inorganic constituents into hydrophobic and hydrophilic acid, base, and neutral dissolved material matrix (DMM) fractions. Physical separation based on DOM apparent molecular weight (AMW) was also evaluated using batch ultrafiltration (UF) data in conjunction with a suitable membrane permeation model. Linear independence of membrane solute transport was theoretically described using non-equilibrium thermodynamics and experimentally demonstrated for AMICON® YC/YM series UF membranes. Mass balances on DMM fraction constituents in untreated and previously coagulated natural waters indicated that quantitative recovery (100 ± 2%) of DOM constituents was achieved, while recovery of inorganic constituents such as iron and aluminum was substantially incomplete (30%-74%). Comparison of whole-water DOM properties with those mathematically reconstituted from DMM fractions demonstrated a marked shift in DOM properties toward lower AMW. Evidence of pH induced partial hydrolysis of protein, polysaccharide, and ester DOM components was also observed. Decreased specific Cl2 demand (mmol DCl2/ mmol DOM) and specific trihalomethane formation (mmol THM/mmol DOM) following chemical fractionation were attributed to increased molar DOM concentration and decreased DOM association with colloidal iron oxide surfaces. Collectively, the results of this research indicate that operational characterization methods result in alteration of DOM physicochemical properties and reactivity with aqueous chlorine, and caution is therefore advisable when interpreting the results of studies conducted using chemically extracted or fractionated DOM. / Ph. D.

An engineered biological filtration (biofiltration) process treating a nutrient-enriched, low-alkalinity, organic-laden surface water downstream of conventional coagulation-clarification and upstream of an ultrafiltration (UF) membrane process was assessed for its treatment effectiveness. The impact of biofiltration pretreatment on UF membrane performance was evaluated holistically by investigating the native source water chemistry and extending the analysis into the drinking water distribution system. The biofiltration process was also compared in treatment performance to two alternative pretreatment technologies, including magnetic ion exchange (MIEX®) and granular activated carbon (GAC) adsorption. The MIEX®, GAC adsorption, and biologically active carbon (BAC) filtration pretreatments were integrated with conventional pretreatment then compared at the pilot-scale. Comparisons were based on collecting data regarding operational requirements, dissolved organic carbon (DOC) reduction, regulated disinfection byproduct (DBP) formation, and improvement on the downstream UF membrane operating performance. UF performance, as measured by the temperature corrected specific flux or mass transfer coefficient (MTC), was determined by calculating the percent MTC improvement relative to the existing conventional-UF process that served as the control. The pretreatment alternatives were further evaluated based on cost and non-cost considerations. Compared to the MIEX® and GAC pretreatment alternatives, which achieved effective DOC removal (40 and 40 percent, respectively) and MTC improvement (14 and 30 percent, respectively), the BAC pretreatment achieved the lowest overall DOC removal (5 percent) and MTC improvement (4.5 percent). While MIEX® relies on anion exchange and GAC relies on adsorption to target DOC removal, biofiltration uses microorganisms attached on the filter media to remove biodegradable DOC. Two mathematical models that establish an empirical relationship between the MTC improvement and the dimensionless alkalinity to substrate (ALK/DOC) ratio were developed. By combining the biofiltration results from the present research with findings of previous studies, an empirical relationship between the MTC improvement versus the ALK/DOC ratio was modeled using non-linear regression in Minitab®. For surface water sources, UF MTC improvement can be simulated as a quadratic or Gaussian distribution function of the gram C/gram C dimensionless ALK/DOC ratio. According to the newly developed empirical models, biofiltration performance is optimized when the alkalinity to substrate ratio is between 10 and 14. For the first time a model has thus been developed that allows for a predictive means to optimize the operation of biofiltration as a pretreatment prior to UF membrane processes treating surface water.

The research presented in this dissertation provides the results of a comprehensive assessment of the water treatment requirements for the City of Sarasota. The City’s drinking water supply originates from two sources: (1) brackish groundwater from the Downtown well field, and (2) Floridan surficial groundwater from the City’s Verna well field. At the time the study was initiated, the City treated the brackish water supply using a reverse osmosis process that relied on sulfuric acid for pH adjustment as a pretreatment method. The Verna supply was aerated at the well field before transfer to the City’s water treatment facility, either for softening using an ion exchange process, or for final blending before supply. For the first phase of the study to evaluate whether the City can operate its brackish groundwater RO process without acid pretreatment, a three-step approach was undertaken that involved: (1) pilot testing the plan to reduce the dependence on acid, (2) implementing the plan on the fullscale system with conservative pH increments, and (3) continuous screening for scale formation potential by means of a “canary” monitoring device. Implementation of the study was successful and the annual savings in operating expenditure to the City is projected to be about $120,000. From the acid elimination study, using the relationship between electrical conductivity in water and total dissolved solids in water samples tested, a dynamic approach to evaluate the performance of the reverse osmosis plant was developed. This trending approach uses the mass transfer coefficient principles of the Homogeneous Solution Diffusion Model. Empirical models iv were also developed to predict mass transfer coefficients for solutes in terms of total dissolved solids and sodium. In the second phase of the study, the use of nanofiltration technology to treat aerated Verna well field water was investigated. The goal was to replace the City’s existing ion exchange process for the removal of hardness and total dissolved solids. Different pretreatment options were evaluated for the nanofiltration pilot to remove colloidal sulfur formed during pre-aeration of the groundwater. Sandfilters and ultrafiltration technology were evaluated as pretreatment. The sandfilter was inadequate as a pre-screen to the nanofiltration pilot. The ultrafiltration pilot (with and without a sandfilter as a pre-screen) proved to be an adequate pretreatment to remove particulates and colloids, especially the sulfur colloids in the surficial groundwater source. The nanofiltration pilot, was shown to be an efficient softening process for the Verna well field water, but it was impacted by biofoulants like algae. The algae growth was downstream of the ultrafiltration process, and so chlorination was used in the feed stream of the ultrafiltration process with dechlorination in the nanofiltration feed stream using excess bisulfite to achieve stable operations. Non-phosphonate based scale inhibitors were also used to reduce the availability of nutrients for biofilm growth on the nanofiltration membranes. The combined ultrafiltration-nanofiltration option for treatment of the highly fouling Verna water samples is feasible with chlorination (to control biofouling) and subsequent dechlorination. Alternatively, the study has shown that the City can also more economically and more reliably use ultrafiltration technology to filter all water from its Verna well field and use its current ion exchange process for removal of excess hardness in the water that it supplies

Produced water (PW) is an oil and gas extraction byproduct that contains a variety of contaminants. PW was traditionally disposed of in deep injection wells or released into the environment. However, these practices may have environmental consequences. The reuse of PW for power water injection (PWI) can help to reduce these impacts by providing a renewable source of water that can be used to maintain production pressure and increase oil recovery. Additionally, the reuse of PW can save oil companies money on water treatment, transporting and disposal costs. Ultrafiltration membranes are used to separate oil from water in produced water. However, ultrafiltration membranes are susceptible to severe fouling by oil molecules, which can reduce their performance. This research investigated the use of Pebax® coating to improve the performance of ultrafiltration membranes for oily-water mixture. The results showed that Pebax® coating can enhance the resistance of membranes to fouling to fouling. The optimal balance between fouling resistance and water flux was found to be achieved by applying very thin coating layers and using appropriate solvents (e.g., n-Butanol). The Pebax® coating creates an essentially defect-free layer on the membrane surface, as seen by the SEM images. Additionally, the coated membranes outperformed the untreated membranes in terms of fouling resistance. This result demonstrated that oil molecules showed less adhesion on the surface and penetration inside membrane pores, thus reducing fouling. Overall, the findings of this research point to PEBAX® coating as a potential means of enhancing the ability of ultrafiltration membranes to resist fouling in the process of separating oil from water. To analyze the long-term performance of coated membranes and to optimize the coating procedure, additional research is required.

No description available.

No description available.

Copper in drinking water elicits a persisting bitter, metallic, or astringent taste. Characteristics and perception mechanisms of copper sensation have not been fully understood. Saliva is assumed to influence copper sensations via binding of salivary electrolytes or proteins with copper. The interaction between salivary components and copper is thought to influence sensory perception by affecting volatility of aroma compounds, de-lubricating salivary proteins, and by controlling solubility of copper. A recent study suggested that intensity of copper taste may be dependent on the amount of solubilized copper, which increases at lower pH. This research was performed to identify 1) the temporal sensory characteristics of copper; 2) the effect of pH on perception of copper sensation; 3) the nature of copper-protein interaction and its impact on sensory perception. The effect of copper on the volatility of aroma compounds and the role of copper-protein interaction in volatile chemistry were investigated using a model mouth system containing artificial saliva at different pH levels. Headspace concentration of each volatile was measured using SPME-GC analysis. Copper (2.5 mg/L) in the model system increased headspace concentration of volatiles (hexanal, butyl acetate, 2-heptanone, and ethyl hexanoate, 0.5 microL/L each) at pH 6.5, but no change in volatility was observed at pH 7.0. At pH 7.5, presence of copper in the artificial saliva decreased headspace volatile concentration. Effect of copper on volatiles at pH 6.5 may be due to increased solubility of copper at lower pH. Copper seems to facilitate hydrophobic binding between mucin and aroma compounds at pH 7.5, possibly by exposing hydrophobic sites of mucin. A time-intensity (TI) test was performed to identify the effect of pH on temporal characteristics of copper sensation. Metallic taste, bitterness, and astringency were major attributes of drinking water containing 2.5 mg/L and 5 mg/L Cu. All three attributes were responsible for the lingering aftertaste of copper. TI test results of copper solutions did not show a common TI pattern of astringency that is characterized with slow onset and longer duration time. Increase in pH of water from 5.5 to 7.5 inhibited metallic taste of copper, but did not reduce bitterness and astringency. The level of soluble copper at pH 7.5 decreased by 50 % compared to that at pH 5.5. Soluble copper concentration and temporal profile of sensory attributes of copper solutions at different pH levels suggest that soluble copper species decide the perception of copper sensation by controlling metallic taste. The nature of copper-protein interaction and its implication on mechanisms of sensory perception were studied by investigating binding of copper to high molecular weight fractions of human saliva. At the copper concentration < 10 mg/L, most copper exists as unbound copper form while about 60 % of copper was found in protein fractions or with precipitated salivary debris. This result suggests that copper is in a soluble unbound form in saliva at low concentration (<10 mg/L) and assumed to be available for taste receptors. At higher concentration, copper either becomes insoluble or binds with proteins. Insoluble copper species are thought to cause astringency. When copper was added at the concentration equal to or greater than 10 mg/L, two salivary proteins of molecular weight 29 kDa and 33 kDa formed insoluble complexes with copper. Low molecular weight mucin (MG2), alpha-amylase, basic proline-rich proteins (PRPs), and a protein of MW 45 kDa also bound with copper. In summary, sensations elicited or influenced by copper are thought to be determined by what copper species are dominant in the mouth. Soluble copper species and insoluble copper species are assumed to interact with different sensory receptors, resulting in metallic taste or astringency. This speciation process is influenced by pH conditions, composition of other electrolytes, and organic chelators such as proteins. / Ph. D.

Anthropogenically generated antibiotic resistance genes (ARGs) are considered emerging contaminants, as they are associated with a critical human health challenge, are persist independent of a bacterial host, are subject to transfer between bacteria, and are present at amplified levels in human-impacted environments. Given the gravity of the problem, there is growing interest in advancing water treatment processes capable of limiting ARG dissemination. This study examined the potential for membrane treatment of microconstituent ARGs, and the effect of wastewater colloids on their removal. Native and spiked extracellular vanA (vancomycin resistance) and blaTEM (β-lactam resistance) ARGs were tracked by quantitative polymerase chain reaction through a cascade of membrane filtration steps. To gain insight into potential associations occurring between ARGs and colloidal material, the wastewater colloids were characterized by scanning electron microscopy, as well as in their protein, polysaccharide, and total organic carbon content. The results suggest that extracellular DNA (eDNA) containing ARGs interacts with wastewater colloids, and can both be protected against degradation and be removed more efficiently in the presence of wastewater colloidal material. Thus, ARG removal may be achievable in sustainable water reuse scenarios using lower cost membranes than would have been selected based on molecular size alone. As membranes are likely to play a vital role in water sustainability, the results of this study enable consideration of ARG removal as part of a comprehensive strategy to manage emerging contaminants and to minimize overall public health risks. / Master of Science

The purpose of this study was to characterize the leachate from a landfill in Pennsylvania that had been pretreated by activated sludge and propose the most efficient treatment for this effluent. These samples had been pretreated in a sequencing batch reactor that also was operated to remove nitrogen by nitrification/denitrification. The SBR samples were found to have low BOD, high COD, high TOC and a very low BOD/COD ratio. These SBR decant samples have poor UV transmittance and hence quench UV light. Five treatment methods were evaluated, coagulation, ultrafiltration, combined coagulation/ultrafiltration, combined ultrafiltration/oxidation and combined filtration/fentons. These processes were tested for their ability to remove BOD and TOC and also to evaluate the improvement in UV transmittance. It was found that coagulation; Ultrafiltration and Ultrafiltration combined with coagulation do not work in improving the transmittance properties though there is a significant BOD and TOC removal with these processes. Ultrafiltration combined with oxidation was found to work the best in terms of TOC removal. In this study, four oxidants, KMnO?, H?O?, NaOCl and Fenton's reagent were used. It was observed that Fenton's reagent was capable of removing 90% TOC at a dose of 1g/L each of iron salt and hydrogen peroxide at a pH of 4.5. Since Fentons reagent was found to be the most effective method, hence, efforts were made to optimize the oxidation process with Fenton's. The two parameters which were studied were the initial pH and the chemical dosage. The initial pH was varied from a value of 2.5 to 6.5. The range of iron salt and peroxide dose used was from 0.05 to 0.1 g/L. Additional studies were conducted using samples filtered through a 0.45 um filter and oxidized with Fenton's reagent. The Fenton's process for oxidation of filtrates from the 0.45?m filter was also optimized with respect to pH and chemical dosage to determine the most economical operating conditions. The maximum transmittance of 57% was obtained for an iron dose of 0.075 g/L and a peroxide dose of 0.075 g/L at a pH of 4.5. This is in comparison to the transmittance of unoxidized 1K ultrafiltrate which was found to be 21.5%. There was a significant difference in the performance of 1K and 0.45um filtrates in terms of TOC removal and percentage transmittance. The oxidation process for improving the UV transmittance of leachate can therefore be economically optimized depending upon the desired efficiency by varying the operational parameters. / Master of Science

Ultrafiltration studies were conducted to determine a treatment approach to remove color and organic carbon from the pulp and paper wastewaters at the Union Camp Corporation, Franklin, VA. Analysis of data collected during this research indicate that ultrafiltration can produce an effluent with less than 5 color units and less than 5 mg/L TOC (99% and 97% removal respectively). The data also indicate that biotreatment of the wastes prior to ultrafiltration removes the smaller molecular weight organic compounds, making ultrafiltration more effective. Pretreatment by pH adjustment and alum coagulation were not effective in improving ultrafiltration performance. Concentration studies indicate that volume reductions up to 95% may be accomplished without excessive membrane fouling. Membrane cleaning with caustic, hypochlorite and detergent produced identical results. It is expected that ultrafiltration would be a more cost effective method of color and TOC removal than coagulation, and would not require sludge disposal. / M.S.