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- All Subjects: Water resources management
Description
Hydrophobic ionizable organic compounds (HIOCs) like per- and polyfluoroalkyl substances (PFAS), certain pharmaceuticals, and surfactants have been detected in groundwater, wastewater, and drinking water. Anion exchange resin treatment is an effective process for removal of anionic contaminants from water. Spent anion exchange resins are conventionally regenerated with high alcohol by volume (ABV) methanol in solution with brine. While effective for regeneration of resins saturated with inorganic anions such as sulfate, nitrate, and perchlorate, HIOCs prove more resistant to regeneration. This research investigated the efficacy of using novel cosolvent solutions with brine to regenerate resins saturated with organic carboxylate and sulfonate anions to understand the effects cosolvent properties have on regenerative ability. Experiments were conducted on six PFAS compounds to evaluate trends in regeneration for three alcohols. For all PFAS species, equivalent ABV and brine solutions showed greatest regeneration with 1-propanol over ethanol and methanol. Experiments with the pharmaceutical sodium diclofenac were conducted showing similar regeneration of 75% methanol and 25% 1-propanol for equivalent salt concentrations and higher regeneration with 1-propanol than ethanol and methanol for equivalent ABV. A series of experiments with surfactant dodecylbenzene sulfonate determined that the key parameters to determine regeneration of the resin for an alcohol cosolvent solution were cosolvent volume fraction, molar mass, Kow value, solution ionic strength, and dielectric constant. Individual assessments on the cost-effectiveness, flammability, and sustainability of cosolvent solutions point to possible future experiments and opportunities for recycled distillery waste streams as regenerative solutions for anion exchange resin.
ContributorsGraham, Cole David (Author) / Boyer, Treavor H (Thesis advisor) / Conroy-Ben, Otakuye (Committee member) / Garcia Segura, Sergio (Committee member) / Arizona State University (Publisher)
Created2022
Description
Membrane fouling, especially inorganic fouling, is a significant obstacle to treatinghighly saline brine using membrane distillation (MD). In this study, microbubbles (MBs) were injected into the feed tank of a lab-scale direct contact membrane distillation (DCMD) system, and its effect on permeate flux over time was examined. A synthetic inland reverse osmosis (RO) brine with a high scaling tendency was used as a feed solution. Results showed a sharper flux decline in the absence of MBs compared to when MBs are continuously injected into the feed tank. The introduction of MBs reduced the formation of salt precipitations on the membrane surface, which was the primary cause of the decline in flux. The use of intermittent MBs injection instead of continuous MB injection was evaluated as a way to reduce energy consumption; with a 15 min MBs injection every 2h, similar benefits were found for intermittent injection compared to continuous injection, indicating that providing MBs continuously is not needed to mitigate scale formation. These results show that MBs can be a potential chemical-free method to prevent scaling in desalination systems treating high saline solutions.
ContributorsAlghanayem, Rayan (Author) / Perreault, Francois (Thesis advisor) / Lind, Mary Laura (Committee member) / Sinha, Shahnawaz (Committee member) / Arizona State University (Publisher)
Created2022
Description
Granular activated carbon (GAC) is effectively used to remove natural organic matter (NOM) and to assist in the removal of disinfection byproducts (DBPs) and their precursors. However, operation of GAC is cost- and labor-intensive due to frequent media replacement. Optimizing the use of GAC is necessary to ensure treatment efficiency while reducing costs. This dissertation presents four strategies to reduce improve GAC usage while reducing formation of DBPs. The first part of this work adopts Rapid Small Scale Tests (RSSCTs) to evaluate removal of molecular weight fractions of NOM, characterized using size exclusion chromatography (SECDOC). Total trihalomethanes (TTHM), haloacetic acids (HAA5) and haloacetonitriles (HAN) formation were quantified after treatment with GAC. Low MW NOM was removed preferentially in the early bed volumes, up until exhaustion of available adsorption sites. DBP formation potential lowered with DOC removal. Chlorination prior to GAC is investigated in the second part of this work as a strategy to increase removal of NOM and DBP precursors. Results showed lower TTHM formation in the effluent of the GAC treatment when pre-chlorination was adopted, meaning this strategy could help optimize and extend the bed life if GAC filters. The third part of this work investigates in-situ GAC regeneration as an alternative to recover adsorption capacity of field-spent GAC that could potentially offer new modes of operation for water treatment facilities while savng costs with reactivation of spent GAC in an external facility. Field-spent GACs were treated with different oxidant solutions and recovery in adsorption capacity was evaluated for NOM and for two micro pollutants. Recovery of GAC adsorption capacity was not satisfactory for most of conditions evaluated. This indicates that in-situ GAC regeneration could be more effective when the adsorbates are present at high concentrations. Lastly, this work investigates the impact of low molecular weight polyDADMAC on N-nitrosodimethylamine (NDMA) formation. Water treatment facilities rely on polyDADMAC as a coagulant aid to comply with NOM removal and turbidity requirements. Since polymer-derived NDMA precursors are not removed by GAC, it is essential to optimize the use and synthesis of polyDADMAC to reduce NDMA precursors during water treatment.
ContributorsFischer, Natalia (Author) / Westerhoff, Paul (Thesis advisor) / Hristovski, Kiril (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2017
Description
This dissertation investigates the mechanisms that lead to fouling, as well as how an understanding of how these mechanisms can be leveraged to mitigate fouling.
To limit fouling on feed spacers, various coatings were applied. The results showed silver-coated biocidal spacers outperformed other spacers by all measures. The control polypropylene spacers performed in-line with, or better than, the other coatings. Polypropylene’s relative anti-adhesiveness is due to its surface free energy (SFE; 30.0 +/- 2.8 mN/m), which, according to previously generated models, is near the ideal SFE for resisting adhesion of bacteria and organics (~25 mN/m).
Previous research has indicated that electrochemical surfaces can be used to remove biofilms. To better elucidate the conditions and kinetics of biofilm removal, optical coherence tomography microscopy was used to visualize the biofouling and subsequent cleaning of the surface. The 50.0 mA cm-2 and 87.5 mA cm-2 current densities proved most effective in removing the biofilm. The 50.0 mA cm-2 condition offers the best balance between performance and energy use for anodic operation.
To test the potential to incorporate electrochemical coatings into infrastructure, membranes were coated with carbon nanotubes (CNTs), rendering the membranes electrochemically active. These membranes were biofouled and subsequently cleaned via electrochemical reactions. P. aeruginosa was given 72h to develop a biofilm on the CNT-coated membranes in a synthetic medium simulating desalination brines. Cathodic reactions, which generate H2 gas, produce vigorous bubbling at a current density of 12.5 mA cm-2 and higher, leading to a rapid and complete displacement of the biofilm from the CNT-functionalized membrane surface. In comparison, anodic reactions were unable to disperse the biofilms from the surface at similar current densities.
The scaling behavior of a nanophotonics-enabled solar membrane distillation (NESMD) system was investigated. The results showed the NESMD system to be resistant to scaling. The system operated without any decline in flux up to concentrations 6x higher than the initial salt concentration (8,439 mg/L), whereas in traditional membrane distillation (MD), flux essentially stopped at a salt concentration factor of 2x. Microscope and analytical analyses showed more fouling on the membranes from the MD system.
To limit fouling on feed spacers, various coatings were applied. The results showed silver-coated biocidal spacers outperformed other spacers by all measures. The control polypropylene spacers performed in-line with, or better than, the other coatings. Polypropylene’s relative anti-adhesiveness is due to its surface free energy (SFE; 30.0 +/- 2.8 mN/m), which, according to previously generated models, is near the ideal SFE for resisting adhesion of bacteria and organics (~25 mN/m).
Previous research has indicated that electrochemical surfaces can be used to remove biofilms. To better elucidate the conditions and kinetics of biofilm removal, optical coherence tomography microscopy was used to visualize the biofouling and subsequent cleaning of the surface. The 50.0 mA cm-2 and 87.5 mA cm-2 current densities proved most effective in removing the biofilm. The 50.0 mA cm-2 condition offers the best balance between performance and energy use for anodic operation.
To test the potential to incorporate electrochemical coatings into infrastructure, membranes were coated with carbon nanotubes (CNTs), rendering the membranes electrochemically active. These membranes were biofouled and subsequently cleaned via electrochemical reactions. P. aeruginosa was given 72h to develop a biofilm on the CNT-coated membranes in a synthetic medium simulating desalination brines. Cathodic reactions, which generate H2 gas, produce vigorous bubbling at a current density of 12.5 mA cm-2 and higher, leading to a rapid and complete displacement of the biofilm from the CNT-functionalized membrane surface. In comparison, anodic reactions were unable to disperse the biofilms from the surface at similar current densities.
The scaling behavior of a nanophotonics-enabled solar membrane distillation (NESMD) system was investigated. The results showed the NESMD system to be resistant to scaling. The system operated without any decline in flux up to concentrations 6x higher than the initial salt concentration (8,439 mg/L), whereas in traditional membrane distillation (MD), flux essentially stopped at a salt concentration factor of 2x. Microscope and analytical analyses showed more fouling on the membranes from the MD system.
ContributorsRice, Douglas, Ph.D (Author) / Perreault, Francois (Thesis advisor) / Abbaszadegan, Morteza (Committee member) / Fox, Peter (Committee member) / Lind-Thomas, Mary Laura (Committee member) / Arizona State University (Publisher)
Created2019