Bench-Scale Testing of a Magnetic Ion Exchange Resin for Removal of Natural Organic Material

The objective of this research was to compare enhanced coagulation with anion exchange for removal of disinfection by-product (DBP) precursors (i.e. natural organic matter (NOM) and bromide). Several anion exchange resins were evaluated for their capacity and rate of NOM and bromide removal. Treatment with a magnetic ion exchange resin (MIEX) was the primary focus of this study. Raw waters from four utilities in California were evaluated. The waters had low turbidity, low to moderate organic carbon concentrations, a wide range of alkalinities, and moderate to high bromide ion concentrations. Large volumes of treated water were generated using the appropriate doses of alum and MIEX as determined by preliminary jar-tests. The treated waters were compared based on removal of ultraviolet (UV) absorbance, dissolved organic carbon (DOC), trihalomethane formation potential (THMFP), and haloacetic acid formation potential (HAAFP). All four bromine- and chlorine-containing THMs (THM4) and all nine bromine- and chlorine-containing HAAs (HAA9) were analyzed. The waters were also fractionated before and after treatment to determine the molecular weight distribution and hydrophobic/hydrophilic character of the DOC. The results indicated that treatment with MIEX is more effective than coagulation at removing UV absorbance and DOC. Treatment with MIEX and treatment with MIEX followed by coagulation yielded similar results, suggesting that treatment with MIEX removes a wide fraction of organic matter including the fraction preferentially removed by coagulation. MIEX treatment reduced the THM4FP and HAA9FP in all waters, and did so to a greater extent than coagulation. Treatment with MIEX was most effective in raw waters having a high specific UV absorbance(SUVA) and a low anionic composition. Following MIEX treatment and subsequent chlorination, there was a shift to the more brominated THM and HAA species as compared to chlorination of the raw water. MIEX also removed bromide to varying degrees, depending on the raw water alkalinity and initial bromide ion concentration. Treatment with MIEX removed a greater amount and a wider range of organic acid fractions and molecular weight fractions than coagulation. Based on kinetic studies, MIEX resin showed the fastest rate of removal of UV absorbance and DOC compared to three other traditional ion exchange resins that also exhibited a high capacity for removal of UV-absorbing materials and DOC.Master of Science in Environmental Engineerin

Total Value of Phosphorus Recovery

Phosphorus (P) is a critical, geographically concentrated, nonrenewable resource necessary to support global food production. In excess (e.g., due to runoff or wastewater discharges), P is also a primary cause of eutrophication. To reconcile the simultaneous shortage and overabundance of P, lost P flows must be recovered and reused, alongside improvements in P-use efficiency. While this motivation is increasingly being recognized, little P recovery is practiced today, as recovered P generally cannot compete with the relatively low cost of mined P. Therefore, P is often captured to prevent its release into the environment without beneficial recovery and reuse. However, additional incentives for P recovery emerge when accounting for the total value of P recovery. This article provides a comprehensive overview of the range of benefits of recovering P from waste streams, i.e., the total value of recovering P. This approach accounts for P products, as well as other assets that are associated with P and can be recovered in parallel, such as energy, nitrogen, metals and minerals, and water. Additionally, P recovery provides valuable services to society and the environment by protecting and improving environmental quality, enhancing efficiency of waste treatment facilities, and improving food security and social equity. The needs to make P recovery a reality are also discussed, including business models, bottlenecks, and policy and education strategies

Pinpointing drivers of widespread colonization of Legionella pneumophila in a green building: Roles of water softener system, expansion tank, and reduced occupancy

IntroductionLegionella pneumophila is an opportunistic pathogen that is a key contributor to drinking water-associated disease outbreaks in the United States. Prolonged water stagnation periods in building plumbing systems due to low occupancy, especially during building shutdowns, breaks, and holidays, can lead to water quality deterioration and (re)colonization of buildings with L. pneumophila. Water monitoring in buildings typically relies on grab samples with small datasets.MethodsIn this study, a larger dataset was created by sampling a Leadership in Energy and Environmental Design (LEED)-certified data-rich commercial building for L. pneumophila and physical-chemical water quality during the COVID-19 pandemic after reduced building occupancy. A proxy for human occupancy rates using WIFI logins was recorded throughout the study period.ResultsL. pneumophila was observed in grab samples taken throughout the building, where concentrations generally increased with greater distances from the building point of entry to locations throughout the building. Factors conducive to microbial growth were identified in the building including fluctuations in water temperatures, lack of chlorine residual, a low water heater setpoint, colonized water-saving fixtures, prolonged stagnation throughout the building; especially in an expansion tank designed to reduce pressure issues during demand fluctuations, and the presence of oversized softener tanks with ion exchange resin that contributed to chlorine residual removal as well as colonization of the resin with L. pneumophila.DiscussionFlushing and thermal disinfection alone did not resolve the problem, and replacement of the expansion tank ultimately resolved the L. pneumophila issue. As ad-hoc approaches are logistically- and time-intensive, more proactive approaches are needed for informing preventative and corrective actions for reducing the risk of exposure to opportunistic pathogens in the building plumbing

Removal of natural organic matter by anion exchange: Multiscale experimentation and mathematical modeling

Natural organic matter (NOM) is ubiquitous in the aquatic environment and is of concern because it impacts engineered and natural processes. For example, during water treatment, NOM reacts with chlorine to form disinfection byproducts that may be associated with adverse health effects. The conventional water treatment process sequence of coagulation, flocculation, clarification, and filtration is the most common treatment approach used to remove NOM. Anion exchange treatment, however, has the potential to be more effective than conventional treatment. To realize the potential of anion exchange technology, an improved understanding of the interactions among NOM, raw water characteristics, anion exchange resins, and process operating parameters is required. The experimental scale, flow regime, and test water were systematically varied to investigate the removal of NOM by anion exchange treatment. Bench-scale batch experiments were conducted using synthetic model waters containing NOM isolates and commercially available anion exchange resins, including a magnetic ion exchange (MIEX) resin. The charge density of the NOM isolates was fundamental to understanding anion exchange reactions. Ion exchange was clearly shown to be the mode of removal of NOM by anion exchange resins. Pilot-scale continuous-flow experiments were conducted using a local raw drinking water and MIEX resin. The effective resin dose, which is the product of the resin concentration and the resin regeneration ratio, was identified as the most important process operating parameter. The pilot plant study demonstrated that anion exchange treatment could be operated more effectively than previously believed. In addition, the pilot-scale continuous-flow tests and bench-scale batch experiments gave consistent results. A mathematical model describing the removal of NOM by anion exchange in a completely mixed flow reactor was developed based upon insights gained from the pilot-scale continuous-flow study. Model predictions were found to be in good agreement with experimental data. The validated mathematical model was used to evaluate the relative influence of operating parameters, anion exchange resin properties, and NOM characteristics on process performance. The mathematical model was also used to evaluate various treatment scenarios. This dissertation presents a unified framework for understanding the removal of NOM by anion exchange treatment

Mimicking and Inhibiting Urea Hydrolysis in Nonwater Urinals

Nonwater urinals are critical in the implementation of building-scale water conservation and urine diversion systems. However, because of the composition of urine and the prevalence of the urease enzyme that hydrolyzes urea, minerals readily precipitate in nonwater urinals and pipes. This leads to clogging, malodor, and possible replacement of nonwater urinals with flush urinals. Accordingly, the goal of this research was to provide an improved understanding of the urea hydrolysis process in nonwater urinals to benefit water conservation and phosphate recovery efforts. Acetic acid addition was used in nonwater urinals to inhibit the urea hydrolysis reaction by lowering the pH, thereby making the precipitation of calcium- and magnesium-containing minerals less favorable. Of the acids tested, 2.5 mL of 2500 mequiv/L acetic acid added after every urination event was able to inhibit urea hydrolysis in synthetic urine and real urine as indicated by the pH and conductivity of the effluent urine. Acid addition also allowed for 43% more phosphate recovery via struvite precipitation in the acetic acid addition synthetic urine than the synthetic urine with no acid addition

Alkaline Earth Metal Cation Exchange: Effect of Mobile Counterion and Dissolved Organic Matter

The goal of this research was to provide an improved understanding of the interactions between alkaline earth metals and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca²⁺ and Mg²⁺ considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane concentrate, and precipitative softening

Fixed Bed Modeling of Nonsteroidal Anti-Inflammatory Drug Removal by Ion-Exchange in Synthetic Urine: Mass Removal or Toxicity Reduction?

Ion-exchange removal of nonsteroidal anti-inflammatory drugs (NSAIDs) in synthetic urine can selectively remove pharmaceuticals with minimal coremoval of nutrients to enhance nutrient recovery efforts. However, the effect of endogenous metabolites in urine on ion-exchange removal, and the corresponding reduction in ecotoxicity potential of pharmaceuticals in treated urine entering the environment, is unknown. To assess treatment efficacy, this work paired predicted breakthrough curves determined by the homogeneous surface diffusion model to an in vitro bioassay to evaluate COX-1 inhibition. The presence of endogenous metabolites in urine significantly impacted pharmaceutical removal, by competing for ion-exchange sites on the resin and reducing the resin capacity for pharmaceuticals. This indicates ion-exchange would be ineffective at removing NSAIDs and other negatively charged compounds in urine. Due to hydrolysis of pharmaceutical metabolites back to the parent compound, treatment systems should be designed based on the ultimate pharmaceutical concentration in ureolyzed urine. Mass removal and COX-1 inhibition followed a nonlinear correlation and mixture toxicity followed the generalized concentration addition model. This work demonstrates the importance of evaluating removal of contaminants of emerging concern, such as pharmaceuticals, using a risk-based approach to ecotoxicity end points in conjunction with mass removal

Behavior of Reoccurring PARAFAC Components in Fluorescent Dissolved Organic Matter in Natural and Engineered Systems: A Critical Review

Fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) has been widely used to characterize dissolved organic matter (DOM). Characterization is based on the intensity and location of independent fluorescent components identified in models constructed from excitation–emission matrices (EEMs). Similar fluorescent components have been identified in PARAFAC studies across a wide range of systems; however, there is a lack of discussion regarding the consistency with which these similar components behave. The overall goal of this critical review is to compare results for PARAFAC studies published since the year 2000 which include one or more of three reoccurring humic-like components. Components are compared and characterized based on EEM location, characteristic ecosystems, and behavior in natural and engineered systems. This synthesis allows PARAFAC users to more confidently infer DOM characteristics based on identified components. Additionally, behavioral inconsistencies between similar components help elucidate DOM properties for which fluorescence spectroscopy with PARAFAC may be a weak predictive tool