Removal of urea in ultrapure water system by urease-coated reverse osmosis membrane

Among the various substances found in the feed source for the production of ultrapure water (UPW), urea is challenging to remove because it is a small molecular weight molecule that is not easily oxidized and does not carry a charge under neutral pH conditions. Urease enzyme, found in various organisms such as plants and bacteria, catalyze the hydrolysis of urea into carbon dioxide and ammonia. In this study, urease was immobilized on the polyamide layer of a reverse osmosis (RO) membrane to remove urea in UPW systems. The removal efficiency of urea by urease-coated RO membrane showed up to 27.9 % higher urea removal efficiency compared to the pristine membrane. This increase in urea removal can be attributed to both physical and biological effects from the urease coating on the membrane. Firstly, urease on the membrane surface can act as an additional physical barrier for urea to pass through. Secondly, urea can be hydrolyzed by the enzyme when it passes through the urease-coated RO membrane. In a two-pass RO system typical for UPW production, the removal of urea by a urease-coated membrane would be enhanced by twofold. This overall method can significantly increase the removal efficiency of urea in UPW systems, especially when considering the compounded removal by the urease coating, rejection by RO, and additional reactions by other treatment processes. Moreover, urea in UPW systems can be removed without the installment of additional processes by simply coating urease on the existing RO membranes.

Using selectivity to evaluate aqueous- and resin-phase denitrification during biological ion exchange

An increased fertilizer application for agricultural purposes has resulted in increased nitrate (NO3-) levels in surface water and groundwater around the globe, highlighting demand for a low-maintenance NO3- treatment technology that can be applied to nonpoint sources. Ion exchange (IEX) is an effective NO3- treatment technology and research has shown that bioregeneration of NO3- laden resins has the potential to minimize operational requirements and brine waste production that often prevents IEX application for decentralized treatment. In this work, batch denitrification experiments were conducted using solutions with low IEX selectivity capable of supporting the growth of denitrifying bacteria, while minimizing NO3- desorption from resins, encouraging resin-phase denitrification. Although only 15% of NO3- was desorbed by the low selectivity solution, this initial desorption started a cycle in which desorbed NO3- was biologically transformed to NO2-, which further desorbed NO3- that could be biotransformed. Denitrification experiments resulted in a 43% conversion rate of initially adsorbed NO3-, but biotransformations stopped at NO2- due to pH limitations. The balance between adsorption equilibria and biotransformation observed in this work was used to propose a continuous-flow reactor configuration where gradual NO3- desorption might allow for complete denitrification in the short retention times used for IEX systems.

Life cycle assessment and life cycle cost analysis of anion exchange and granular activated carbon systems for remediation of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs)

Anion exchange resin (AER) and granular activated carbon (GAC) have emerged as prominent technologies for treatment of waters contaminated with per- and polyfluoroalkyl substances (PFASs). This study compares the life cycle environmental impacts and life cycle costs of remediating PFAS-contaminated groundwater with these competing technologies, using field pilot data to inform model inputs. Comparative analysis indicates that AER systems employing single-use "PFAS-selective" resins have lower environmental impacts and costs than systems using regenerable resins or GAC adsorbents, supporting its use in future remediation efforts. Use of GAC operated as a single-use adsorbent led to the highest emissions as well as the highest treatment costs, with thermally-reactivated GAC proving to be less impactful than regenerable AER treatment. Sensitivity analyses highlighted the dominance of media usage rate (MUR), which is highly dependent on the selected PFAS treatment goals, to determine environmental impacts and costs over a 30-year system life cycle. Selection of very stringent changeout criteria (e.g., detection of any PFASs in effluent) significantly reduces the advantages of single-use resins. For regenerable AER, environmental impacts were dominated by management of the PFAS-contaminated brine/co-solvent waste stream used to regenerate the adsorbent, as well as the cosolvent content of the regenerant mixture and the cosolvent recovery efficiency achieved via on-site distillation. High impacts estimated for GAC adsorption, the result of high MUR relative to ion exchange media, can be significantly reduced if spent adsorbents are reused after thermal reactivation, but impacts are still greater than those predicted for single-use ion exchange systems. Findings are expected to hold across a range of diverse sites, including drinking water systems treating more dilute sources of PFAS contamination, as PFAS breakthrough was not found to be highly sensitive to sourcewater PFAS concentrations.

Solar distillation of human urine to recover non-potable water and metal phosphate mineral

Human urine is a readily available nutrient source that can complement commercial fertilizer production, which relies on finite mineral resources and global supply chains. This study evaluated the effectiveness of a simplified solar distillation process for urine to recover phosphorus (P) and nitrogen for agricultural use and water for non-potable purposes. Synthetic fresh, synthetic hydrolyzed, real fresh, and real hydrolyzed urine were exposed to direct sunlight for 6 h in a simple distillation apparatus, which produced distillation bottoms and distillate. Metal phosphate precipitation in the distillation bottoms was evaluated to recover P. The non-potable water was recovered as distillate. Hydrolyzed urine recovered more metal phosphate solid in the distillation bottoms and had a higher conductivity in the distillate than fresh urine. Hydrolyzed urine also achieved greater distillate volume recovery than fresh urine. Hydrolyzed urine had a greater presence of UV-absorbing organics in the distillate than fresh urine and therefore produced a lower-quality product water. There was no significant correlation between the daily high air temperature and the volume of distillate recovered. This study provides a comprehensive data set on simplified solar distillation of human urine considering the fate of nutrients and water for different types of urine.

Perspective: Phosphorus monitoring must be rooted in sustainability frameworks spanning material scale to human scale

Phosphorus (P) is a finite resource, and its environmental fate and transport is complex. With fertilizer prices expected to remain high for years and disruption to supply chains, there is a pressing need to recover and reuse P (primarily as fertilizer). Whether recovery is to occur from urban systems (e.g., human urine), agricultural soil (e.g., legacy P), or from contaminated surface waters, quantification of P in various forms is vital. Monitoring systems with embedded near real time decision support, so called cyber physical systems, are likely to play a major role in the management of P throughout agro-ecosystems. Data on P flow(s) connects the environmental, economic, and social pillars of the triple bottom line (TBL) sustainabilty framework. Emerging monitoring systems must account for complex interactions in the sample, and interface with a dynamic decision support system that considers adaptive dynamics to societal needs. It is known from decades of study that P is ubiquitous, yet without quantitative tools for studying the dynamic nature of P in the environment, the details may remain elusive. If new monitoring systems (including CPS and mobile sensors) are informed by sustainability frameworks, data-informed decision making may foster resource recovery and environmental stewardship from technology users to policymakers.

Removal of perfluoroalkyl acids and common drinking water contaminants by weak-base anion exchange resins: Impacts of solution pH and resin properties

The underlying chemistry of weak-base (WB) anion exchange resins (AERs) for contaminant removal from water is not well documented in the literature. To address this, batch adsorption experiments were conducted at pH 4, 7, and 10 using two representative WB-AERs (polyacrylic IRA67 and polystyrene IRA96) and two representative strong-base (SB) AERs (polyacrylic IRA458 and polystyrene A520E), of differing polymer composition, for the removal of nitrate, sulfate, 3-phenylpropionic acid (3-PPA) as surrogate for natural organic matter, and six perfluoroalkyl acids (PFAAs). Under acidic (pH 4) and neutral (pH 7) conditions, the selectivity of AERs for each contaminant was predominantly influenced by polymer composition followed by the size of the resin functional group. This result reflected the WB-AERs being fully protonated and functioning identical to SB-AERs. Isotherm model parameters revealed WB-AER had higher capacity than SB-AER with analogous polymer composition and porosity regardless of resin selectivity for each contaminant. Under basic conditions (≥ pH 10), contaminant removal by WB-AERs declined due to deprotonation of the tertiary amine functional groups. Removal of PFAAs by the more hydrophobic polystyrene WB-AER (IRA96) remained approximately constant with changing pH, which was possibly due to electrostatic interactions with remaining protonated amine functional groups on the resin.

Phosphorus removal by steel slag from tile drainage water: Lab and field evaluations

Basic oxygen furnace (BOF) and blast furnace (BF) steel slags are well suited for phosphorous (P) removal from nonpoint sources such as agricultural runoff. However, the reported mechanism(s) of removal varies from study to study which complicates implementation for unique environmental conditions that may interfere with the removal mechanism(s). This work compared laboratory column experiments and field filter experiments to provide insights on the influence of relevant field conditions (water alkalinity, slag grain size distribution, BF:BOF slag ratio, and water stagnation) on P removal by BF and BOF steel slag mixtures. Alkalinity was the most influential variable in lab-scale slag columns that received 250 mg/L alkalinity water and achieved complete P removal throughout the 3-h experiment, while identical columns receiving 500 mg/L alkalinity water averaged 52% P removal and only 14% removal after 2.5 h. Batch regeneration and adsorption experiments were conducted on the exhumed BOF/BF slag mixture from the field filter to evaluate strategies for increasing field P removal capacity. The adsorption capacity of steel slags was effectively regenerated by 0.01 M Al₂(SO₄)₃, which allowed for an additional 34% P removal in batch adsorption tests. The acid neutralization capacity of slag samples was effectively regenerated by 1 M NaOH, which allowed previously expended slag to reach a pH of 9.7 even in high alkalinity test water. The results presented here show that BF slag and Al₂(SO₄)₃ regeneration of BF slag is best suited for high alkalinity influent conditions and removes P through adsorption while BOF slag and NaOH regeneration perform best under low alkalinity conditions and removes P through mineral precipitation.

Pilot study comparison of regenerable and emerging single-use anion exchange resins for treatment of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs)

This study reports the results of an 8-month pilot study comparing both regenerable and emerging single-use anion exchange resins (AERs) for treatment of per- and polyfluoroalkyl substances (PFASs) at a source zone impacted by historical use of aqueous film-forming foam (AFFF). Two regenerable (Purolite A860 and A520E) and three single-use (Purolite PFA694E, Calgon CalRes 2301, and Dowex PSR2+) AERs were tested in parallel, collecting effluent samples after treatment for 30-sec and 2-min total empty bed contact time (EBCT). Results demonstrate that single-use AERs significantly outperform regenerable resins, particularly for treatment of long-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs). No detectable concentrations of ≥C7 PFCAs or PFSAs were observed within 150,000 bed volumes (BVs) after treatment with the single-use resins (2-min EBCT). Analysis of effluent samples following 30-sec EBCT treatment shows that even the shortest-chain PFSAs do not reach 50% breakthrough within the first 350,000 BVs, though differences in removal of short-chain PFCAs was less dramatic. The regenerable polyacrylic A860 resin performed very poorly compared to all polystyrene resins, with >90% breakthrough of all PFASs occurring within 10,000 BVs. The greater affinity of polystyrene resins is attributed to increased hydrophobic interactions in addition to electrostatic ion exchange. Analysis of breakthrough profiles reveals empirical correlation with ion exchange affinity coefficients (logK_ex) measured in batch experiments. Postmortem analysis of PFASs extracted from spent resins revealed chromatographic elution behavior and competition among PFASs for adsorption to the resins. PFSAs and long-chain PFCAs were preferentially adsorbed to earlier sections in the AER columns, whereas short-chain PFCAs were competitively displaced towards the later sections of the columns and into the effluent, consistent with effluent concentrations of the latter structures exceeding influent values. These results provide insights into the mechanisms that govern PFAS adsorption to AERs in real multisolute groundwater matrices and support findings from other diverse sites regarding PFAS affinity, elution behavior, and competition for exchange sites.

Life cycle environmental impacts of regeneration options for anion exchange resin remediation of PFAS impacted water

Although anion exchange resin (AER) treatment is considered an effective technology for removing per- and polyfluoroalkyl substances (PFASs) from impacted water, the environmental impacts associated with AER regeneration have not been systematically explored. In particular, the trade-offs of altering the composition of the regeneration solution and disposing of or recycling the waste regeneration solution are not known. To fill these important gaps in the literature, this research conducted a comparative life cycle assessment (LCA) of an AER-based PFAS remediation system with different regeneration scenarios including disposing of waste regeneration solution via incineration, reusing the organic cosolvent and brine fractions of the waste regeneration solution, and altering the composition of the regeneration solution to avoid organic cosolvent or NaCl. The results show that disposing of waste regeneration solution via incineration, without recycling organic cosolvent or brine, had the greatest environmental impact, and that incineration accounted for the greatest impact among contributing processes. Recycling of the cosolvent (or cosolvent and brine) fraction of the waste regeneration solution resulted in lower environmental impacts due to reduced mass of waste disposed of via incineration. Replacing NaCl in the brine with an alternative salt resulted in higher environmental impacts, with salts derived from chemical production, such as ammonium chloride and potassium carbonate, showing the largest increases in impacts. The results of this research highlight the importance of understanding the fate of PFASs during incineration, and the need for PFAS destruction technologies that can be coupled to AER regeneration to avoid incineration.

Pre- and post-flushing of three schools in Arizona due to COVID-19 shutdown

A one-day water sampling and flushing study was conducted for three schools in Maricopa County that experienced prolonged building inactivity due to the COVID-19 pandemic: an elementary school, middle school, and high school. Grab samples were taken at hand washing sinks, water fountains, and hose bibbs before and after flushing. Samples were analyzed for free chlorine, UVA254, copper, lead, total trihalomethanes, pH, conductivity, temperature, and Legionella species. All three schools experienced an increase in free chlorine post-flush. Copper concentrations were higher for first draw samples than post-flush samples for all schools. Conductivity, temperature, and pH did not see a major change after flushing. UVA254 values decreased after flushing. Bromoform species saw a 20% increase after flushing at the elementary school. Legionella spp. did not decrease post-flush at the elementary school. Overall, flushing changed the water quality at the schools. However, equipment flushing may be necessary to fully remediate Legionella spp.

ARTICLE IMPACT STATEMENT

Prolonged closure of buildings causes water quality issues such as lack of disinfectant and Legionella. Flushing can restore water quality.

Anion exchange resin removal of per- and polyfluoroalkyl substances (PFAS) from impacted water: A critical review

A key gap in the literature on the treatment of per- and polyfluoroalkyl substances (PFAS) in impacted water is the absence of a review article dedicated to anion exchange resin (AER) treatment. This gap is important because previous research has consistently shown adsorption by AER to be one of the most effective treatment processes for PFAS removal from impacted water, and AER is one of the most commonly deployed technologies in the field. Given the scope of the previous review articles on PFAS removal by various adsorbent types, the sections on AER do not explore the full depth of PFAS and AER interactions nor cover the breadth of AER testing conditions. Accordingly, the goal of this paper was to critically review the available peer-reviewed literature on PFAS removal from water by AER. The specific objectives of the review were to synthesize the previous literature results on (1) batch adsorption behavior, (2) impact of water chemistry conditions, (3) continuous-flow adsorption, (4) adsorption modeling, (5) regeneration, and (6) weak-base AER. Following from critical review of the literature, the future research priorities discussed include: (i) improving the underlying science that governs PFAS-resin interactions, (ii) improving methods for resin regeneration and management of PFAS-contaminated concentrate streams, and (iii) comparative life cycle environmental and economic analyses for ion exchange treatment systems relative to competing technologies.

A transition management framework to stimulate a circular phosphorus system

As the global population is projected to increase by two billion people by 2050, so will the demand for phosphorus (P), an essential nutrient for all living organisms and a major driver of eutrophication. To sustainably meet these challenges, we apply the conceptual framework of transition management (TM) to demonstrate how the trajectory of the current linear P use system could be strategically shifted toward a more circular P system. We present US case studies to examine P transitions management in intensive agriculture, wastewater disposal, and food waste management. Our goal is twofold. By first understanding past transitions in P management in the USA, we can build upon these insights for future management. This can then be applied to other global regions such as developing countries to bypass stages of transition as they intensify agriculture, incorporate sewers into cities, and expand waste management, to avoid becoming entrenched in unsustainable P management. We suggest how spaces for experimentation and collaboration can be created, how and which actor networks can be mobilized, and what action strategies and policies can be recommended to accelerate their transition to P sustainability. Our case studies show that while substantial improvements have been made, the transition toward a circular economy of P is far from complete. Our findings point to the value of utilizing TM for future progress in the US Development of TM frameworks for managing P in other regions of the world may enable them to achieve sustainable P development faster and more effectively than the USA.

Removal of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) Using Ion-Exchange and Nonionic Resins

Despite benefits to the firefighting industry, the release of per- and polyfluoroalkyl substances (PFASs) from aqueous film-forming foam (AFFF) into aquatic systems poses significant risks to human health and other organisms. While anion-exchange technologies have proven to be effective for removing perfluoroalkyl acids (PFAAs) from water, their effectiveness for removing the diverse PFAS structures discovered in AFFF remains unknown. Here, we report on the adsorption of 75 PFASs, including 63 polyfluorinated substances, in a diluted AFFF mixture using 14 commercially available ion-exchange (IX)/nonionic resins and granular activated carbon (GAC). Results showed that anion-exchange resins (AERs) exhibited significant adsorption of PFASs compared to cation-exchange resins (CERs), nonionic resins (NIRs), and GAC regardless of the PFAS's predicted charge. Isotherm data showed that macroporous AERs have a higher PFAS adsorption capacity compared to gel-type AERs. Cross-correlation comparison of PFAS/Cl^- selectivity coefficients (K_ex) for each PFAS-AER combination showed that the hydrophobicity of the AER functional group, and polymer matrix played a dominant role in determining resin affinity for PFASs. PFAS structural characteristics also significantly affected adsorption, with increasing chain length and a net negative charge increasing the extent of adsorption. Results from this study provide guidelines for the selection of resins to adsorb a wider range of PFASs and meaningful insights for the development of quantitative models for IX treatment of AFFF-impacted water.

Ammonium and potassium removal from undiluted and diluted hydrolyzed urine using natural zeolites

There is limited research comparing nutrient removal in concentrated and dilute waste streams. Accordingly, the goal of this research was to study the effect of dilution on ammonium and potassium removal from real hydrolyzed urine using natural zeolites. The performance of two natural zeolites, clinoptilolite and chabazite, was studied and compared using batch equilibrium experiments at four dilution levels defined as urine volume divided by total solution volume (expressed as a percent): 100%, 10%, 1% and 0.1%. The adsorption behavior of other exchangeable ions, namely sodium, calcium, and magnesium, in clinoptilolite and chabazite was studied to improve the understanding of ion exchange stoichiometry. Ammonium and potassium removals were highest in undiluted urine samples treated with clinoptilolite or chabazite. This is a key finding as it illustrates the benefit of collecting undiluted urine via source separation. High removal of ammonium and potassium by clinoptilolite and chabazite was also achieved in 10% urine solutions, which are representative of water-efficient flush systems and show that nutrient recovery is possible for diluted urine as well. Chabazite showed higher ammonium and much higher potassium removal than clinoptilolite. Finally, the results showed that clinoptilolite and chabazite demonstrated stoichiometric exchange between ammonium and potassium in urine solutions with mobile cations in the zeolites.

Removal of natural organic matter by ion exchange: Comparing regenerated and non-regenerated columns

Dissolved organic matter (DOM) in water has adverse impacts on the water treatment process and is effectively removed by ion exchange (IEX). Some researchers have proposed the term biological ion exchange (BIEX) for the process of continuous DOM removal by ion exchange without the need for chemical regeneration that results in brine waste. Surface water with moderate dissolved organic carbon (DOC) concentrations (4-6 mg/L) and high sulfate concentrations (80 - 120 mg/L) was fed to two regenerated and two non-regenerated columns for 12,500 bed volumes (9 months) with the goal of investigating the effects of chemical and possibly biological regeneration on long-term IEX operation. Chemically regenerated columns achieved between 60 and 80% DOC removal for the entirety of the experiment, while non-regenerated columns achieved steady DOC removal of ~50%. Inorganic ion analysis showed that biological activity had minimal impact on DOC removal, and the main mechanism of removal was secondary IEX between sulfate (SO₄^2-) and fractions of DOC with high affinities for ion exchange. Fluorescence and specific UV absorbance at 254 nm (SUVA 254) data showed that fractions of DOC with higher SUVA 254 values (terrestrial-like fractions) were better removed by secondary IEX than those with lower SUVA 254 values (aquatic/microbial-like fractions). Scanning electron microscopy showed that biofilms on non-regenerated resins covered 5-15% of the resin surface and are composed of numerous species of bacteria with varying functions, with some protozoa present.

Impact of acetic acid addition on nitrogen speciation and bacterial communities during urine collection and storage

The rate of urea hydrolysis in nonwater urinals is influenced by the volume of urination events and the frequency of urinal use. Inhibition of urea hydrolysis with acetic acid addition has been demonstrated at the laboratory scale but it was not able to fully represent the conditions of a real restroom with real urine collection. The goal of this study was to understand the effects of acid addition for control of urea hydrolysis on nutrient concentrations and bacterial communities in human urine during collection and storage. Three control logics were used to determine the schedule of acid addition: (i) acid addition after every urination event, (ii) acid addition during periods of high building occupancy, and (iii) acid addition during periods of low building occupancy. Wifi logins were used to approximate building occupancy and to create the control logics used in the study. All three control logics were able to inhibit urea hydrolysis. The bacterial communities were identified to determine the impact of acid addition on the community structure. The collection of urine by nonwater urinals alone did not reduce the presence of enteric bacteria commonly found when collecting urine with urine-diverting toilets. Acid addition reduced the community diversity and created conditions for higher relative abundances of the order Enterobacteriales. Finally, results from stored acidified urine showed that urea hydrolysis inhibition is reversible and is influenced by the amount of acid added at the urinal. The amount of acid added can influence the rate of hydrolysis in the storage tanks and can be used to select for urea- or ammonia-nitrogen for nutrient recovery. This study is the first of its kind to inhibit urea hydrolysis in nonwater urinals in a real restroom with real urine, and is the first to identify the bacterial communities in urine collected solely with nonwater urinals.

Ammonia Recovery from Hydrolyzed Human Urine by Forward Osmosis with Acidified Draw Solution

Forward osmosis (FO) is a low-pressure membrane process that can selectively separate low molecular weight neutral compounds such as ammonia from urine. However, an understanding of how un-ionized ammonia transfers is vital for maximizing ammonia recovery. Therefore, this research aimed to determine the transport behavior of low molecular weight neutral nitrogen compounds in order to maximize ammonia recovery from real hydrolyzed human urine by FO. Using urea as a model, batch FO experiments concluded that low molecular weight neutral compound transfer is dependent on concentration equilibrium between the feed and draw solutions due to its ability to freely move across the FO membrane. Therefore, 50% recovery is the theoretical maximum that could be achieved. However, novel strategic pH manipulation between the feed and the draw solution allowed for up to 86% recovery of ammonia by keeping the draw solution pH < 6.5 and the feed solution pH > 11, overcoming the 50% recovery barrier. An economic analysis showed that ammonia recovery by FO has the potential to be more economically favorable compared to ammonia air stripping or ion exchange if the proper draw solute is chosen.

Comparative removal of Suwannee River natural organic matter and perfluoroalkyl acids by anion exchange: Impact of polymer composition and mobile counterion

Anion exchange resin (AER) adsorption is an established technology for water treatment and groundwater remediation. Two contaminants amenable to AER treatment are natural organic matter (NOM) and per- and polyfluoroalkyl substances (PFAS), specifically anionic perfluoroalkyl acids (PFAAs) such as perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). NOM is ubiquitous in natural waters and is often targeted for removal. PFAS occurrence in water resources is a human health concern. Accordingly, the goal of this research was to provide new insights on the use of AER for water treatment considering separate and combined removal of NOM and PFAAs. Batch experiments were conducted comparing polystyrene and polyacrylic AER in both chloride- and sulfate-forms using natural groundwater spiked with Suwannee River natural organic matter (SRNOM) and/or six PFAAs. The polymer composition of the AER had a significant impact on contaminant removal with polystyrene resin more effective for PFAA removal and polyacrylic resin more effective for SRNOM removal. Both resins had type I quaternary ammonium functional groups; however, the polyacrylic resin had trimethyl ammonium whereas the polystyrene resin had triethyl ammonium. Therefore, the influence of polymer composition could not be isolated conclusively from functional group chemistry. Polystyrene AER showed greater removal of PFAAs with sulfonate than carboxylate head group and 8-carbon than 4-carbon chain length. Removal of SRNOM and PFAAs by both resin polymer compositions were greater when sulfate was the mobile counterion ion than chloride. The results of this research have important implications for using AER for water treatment and remediation. Foremost, polymer composition and mobile counterion form of the resin can be selected to target specific contaminants and maximize contaminant removal. When contaminants have unique interactions with AER such as SRNOM and polyacrylic resin and PFAAs and polystyrene resin, the presence of one contaminant does not impact removal of the other contaminant.

Opportunities for Building-Scale Urine Diversion and Challenges for Implementation

Urine diversion (i.e., urine source separation) has been proposed as a more sustainable solution for water conversation, nutrient removal and recovery, and pharmaceutical sequestration. As wastewater regulations become more stringent, wastewater treatment plants reach capacity, and water resources become more strained, the benefits of urine diversion become more appealing. By using nonwater urinals and urine-diverting toilets, urine diversion systems seek to collect undiluted human urine for nutrient recovery and pharmaceutical sequestration. Urine is a unique, nutrient-rich waste stream that constitutes an overall low volume of waste entering a wastewater treatment plant. If urine is separated at the building-scale, various technologies can be used to recover nutrients and sequester pharmaceuticals at their most concentrated location. However, the implementation of urine diversion requires a paradigm shift from conventional comingling of wastewater and centralized treatment to source separation and decentralized treatment. This Account proposes a vision for building-scale implementation of urine diversion with the goal of clarifying the opportunities and challenges in this context. The main components of urine, i.e., nitrogen, phosphorus, potassium, and pharmaceuticals, are major drivers for technology development and system implementation. Stepping back, the benefits from water conservation and effects on wastewater treatment are an extension of the system boundary that can impact the sustainability of adjacent systems. However, major challenges have been identified in the literature as hurdles for widespread implementation of urine diversion. Challenges include the comparison of recovering nutrients at the wastewater plant versus at the source, the collection and storage of urine, the ability to recover nutrients and sequester pharmaceuticals, and the overall environmental and economic impacts of urine diversion systems. While these challenges exist, studies have been conducted to address some of the underlying research questions. As more research is conducted, the vision of a seamless urine diversion system with building-wide plumbing and storage comes closer to reality. As such, the application of urine diversion systems will benefit from technology development and research to fill gaps that have been identified. It is important to classify urine diversion systems as a process and not a product. This has implications for the way these systems are evaluated, as their impact on peripheral systems can be of benefit to different stakeholders. In the same light, new research areas, such as cyber-physical systems, reverse logistics, and sustainability transitions, can be applied to urine diversion as approaches for ensuring a robust process for widespread implementation. However, established technologies should be constantly reassessed and enhanced by newer techniques. For example, membrane distillation, eutectic freeze concentration, and solar evaporation should be considered for nutrient recovery and volume reduction because they offer benefits over conventional technologies. Finally, the human behavior component of urine diversion cannot be ignored, as negative user acceptance and improper maintenance of these systems can have a detrimental impact on their future implementation.

Real-Time Monitoring and Control of Urea Hydrolysis in Cyber-Enabled Nonwater Urinal System

This research used a cyber-physical system (CPS) to monitor and control the extent of urea hydrolysis in nonwater urinals. Real-time pH and conductivity data were used to control urea hydrolysis inhibition under realistic restroom conditions with acetic acid addition. Variable urination frequencies and urination volumes were used to compare three conditions that affect the progression of urea hydrolysis. Mechanistic and conceptual models were created to evaluate the factors that influence the progression of urea hydrolysis in nonwater urinals. It was found that low urination volumes at low frequencies created ideal conditions for urea hydrolysis to progress. Alternatively, high urination volumes at high frequencies created pseudo-inhibitory conditions because it did not allow for sufficient reaction time or mixing with older urine in the urinal trap. The CPS was used to control urea hydrolysis inhibition by two logics: (1) reactively responding to a pH threshold and (2) predictively responding to past measurements using four lasso regression models. Results from the control logic experiments showed that acid was added once per hour under low use conditions and once in a 4 h experiment for high use conditions. The CPS allowed for full control of urine chemistry in the nonwater urinal, reducing the conditions (i.e., clogging and malodor) that have led to the removal of nonwater urinals in the United States.

Physical-chemical interactions between pharmaceuticals and biochar in synthetic and real urine

This research advances the knowledge of the pharmaceutical removal interactions by biochar in synthetic and real urine through the use of reference adsorbents and adsorbate probes. Earlier work has combined biochar and urine for pharmaceutical removal, however, the interactions that influence adsorption are unknown. In this study, bamboo biochar and softwood biochar were chosen as the representative materials and the model pharmaceuticals were naproxen and paracetamol. To further investigate the physical-chemical interactions, two nonpolar adsorbates, para-xylene and dimethylnaphthalene, were tested. Graphite and anion exchange resin, were used to isolate van der Waals and electrostatic interactions, respectively. Experimental kinetic and equilibrium data were fit to multiple adsorption models where the pseudo-second order and Freundlich exhibited the best fit, respectively. The Freundlich and Langmuir parameters had similar trends showing that softwood had the highest adsorption capacity. The model parameters indicated higher selectivity for nonpolar para-xylene and dimethylnaphthalene by graphite and polar paracetamol and naproxen by softwood biochar. The decreasing trend of importance of key interactions for pharmaceutical sorption to biochar are: van der Waals > hydrogen bonding > electrostatic interactions. No statistically significant difference was found between urine age (fresh vs. hydrolyzed) and pharmaceutical removal; however, the urine matrix (synthetic vs. synthetic with metabolites vs. real urine) did show a statistically significant difference on pharmaceutical removal where synthetic urine had comparatively greater adsorption. As constituents (i.e., metabolites) were added to urine matrices, reduced adsorption of pharmaceuticals was observed, indicating that adsorption processes should be tested in real urine for accuracy.

Human Urine as a Fertilizer in the Cultivation of Snap Beans ( Phaseolus vulgaris) and Turnips ( Brassica rapa)

The main reason for implementing human urine diversion is to produce a local and renewable source of fertilizer for agriculture. Accordingly, the goal of this research was to compare human urine fertilizer and synthetic fertilizer in the cultivation of snap beans and turnips by evaluating the yield, plant tissue chemical composition, nutrient uptake efficiency, soil nutrient content, and leachate nutrient content between plots. Four fertilizer treatments were evaluated: (1) synthetic fertilizer, (2) urine supplemented with synthetic fertilizer, (3) urine only, and (4) a no-fertilizer control, referred to as treatments 1, 2, 3, and 4, respectively. Plants fertilized by treatments 1 and 2 produced the highest yield for fall turnips and spring snap beans. The turnip yield for the urine-only treatment was significantly higher than the no-fertilizer control. Overall, the results showed that supplemented urine fertilizer can be used as an alternative to synthetic fertilizer with comparable yields, and urine-only fertilizer can significantly increase yields over the no-fertilizer control. The results also suggest that nutrients in urine are available in a form favorable for plant uptake.

Managing Diffuse Phosphorus at the Source versus at the Sink

Judicious phosphorus (P) management is a global grand challenge and critical to achieving and maintaining water quality objectives while maintaining food production. The management of point sources has been successful in lowering P inputs to aquatic environments, but more difficult is reducing P discharges associated with diffuse sources, such as nonpoint runoff from agriculture and urban landscapes, as well as P accumulated in soils and sediments. Strategies for effective diffuse-P management are imperative. Many options are currently available, and the most cost-effective and practical choice depends on the local situation. This critical review describes how the metrics of P quantity in kg ha^-1 yr^-1 and P form can influence decision-making and implementation of diffuse-P management strategies. Quantifying the total available pool of P, and its form, in a system is necessary to inform effective decision-making. The review draws upon a number of " current practice" case studies that span agriculture, cities, and aquatic sectors. These diverse examples from around the world highlight different diffuse-P management approaches, delivered at the source in the catchment watershed or at the aquatic sink. They underscore workable options for achieving water quality improvement and wider P sustainability. The diffuse-P management options discussed in this critical review are transferable to other jurisdictions at the global scale. We demonstrate that P quantity is typically highest and most concentrated at the source, particularly at farm scale. The most cost-effective and practically implementable diffuse-P management options are, therefore, to reduce P use, conserve P, and mitigate P loss at the source. Sequestering and removing P from aquatic sinks involves increasing cost, but is sometimes the most effective choice. Recovery of diffuse-P, while expensive, offers opportunity for the circular economy.

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.

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.

Integrated bicarbonate-form ion exchange treatment and regeneration for DOC removal: Model development and pilot plant study

The application of bicarbonate-form anion exchange resin and sodium bicarbonate salt for resin regeneration was investigated in this research is to reduce chloride ion release during treatment and the disposal burden of sodium chloride regeneration solution when using traditional chloride-form ion exchange (IX). The target contaminant in this research was dissolved organic carbon (DOC). The performance evaluation was conducted in a completely mixed flow reactor (CMFR) IX configuration. A process model that integrated treatment and regeneration was investigated based on the characteristics of configuration. The kinetic and equilibrium experiments were performed to obtain required parameters for the process model. The pilot plant tests were conducted to validate the model as well as provide practical understanding on operation. The DOC concentration predicted by the process model responded to the change of salt concentration in the solution, and showed a good agreement with pilot plant data with less than 10% difference in terms of percentage removal. Both model predictions and pilot plant tests showed over 60% DOC removal by bicarbonate-form resin for treatment and sodium bicarbonate for regeneration, which was comparable to chloride-form resin for treatment and sodium chloride for regeneration. Lastly, the DOC removal was improved by using higher salt concentration for regeneration.

Life cycle assessment and costing of urine source separation: Focus on nonsteroidal anti-inflammatory drug removal

Urine source separation has the potential to reduce pharmaceutical loading to the environment, while enhancing nutrient recovery. The focus of this life cycle assessment (LCA) was to evaluate the environmental impacts and economic costs to manage nonsteroidal anti-inflammatory drugs (NSAIDs) (i.e., diclofenac, ibuprofen, ketoprofen and naproxen) and nutrients in human urine. Urine source separation was compared with centralized wastewater treatment (WWT) (biological or upgraded with ozonation). The current treatment method (i.e., centralized biological WWT) was compared with hypothetical treatment scenarios (i.e., centralized biological WWT upgraded with ozonation, and urine source separation). Alternative urine source separation scenarios included varying collection and handling methods (i.e., collection by vacuum truck, vacuum sewer, or decentralized treatment), pharmaceuticals removal by ion-exchange, and struvite precipitation. Urine source separation scenarios had 90% lower environmental impact (based on the TRACI impact assessment method) compared with the centralized wastewater scenarios due to reduced potable water production for flush water, reduced electricity use at the wastewater treatment plant, and nutrient offsets from struvite precipitation. Despite the greatest reduction of pharmaceutical toxicity, centralized treatment upgraded with ozone had the greatest ecotoxicity impacts due to ozonation operation and infrastructure. Among urine source separation scenarios, decentralized treatment of urine and centralized treatment of urine collected by vacuum truck had negligible cost differences compared with centralized wastewater treatment. Centralized treatment of urine collected by vacuum sewer and centralized treatment with ozone cost 30% more compared with conventional wastewater treatment.

Student support and perceptions of urine source separation in a university community

Urine source separation, i.e., the collection and treatment of human urine as a separate waste stream, has the potential to improve many aspects of water resource management and wastewater treatment. However, social considerations must be taken into consideration for successful implementation of this alternative wastewater system. This work evaluated the perceptions of urine source separation held by students living on-campus at a major university in the Southeastern region of the United States. Perceptions were evaluated in the context of the Theory of Planned Behavior. The survey population represents one group within a community type (universities) that is expected to be an excellent testbed for urine source separation. Overall, respondents reported high levels of support for urine source separation after watching a video on expected benefits and risks, e.g., 84% indicated that they would vote in favor of urine source separation in residence halls. Support was less apparent when measured by willingness to pay, as 33% of respondents were unwilling to pay for the implementation of urine source separation and 40% were only willing to pay $1 to $10 per semester. Water conservation was largely identified as the most important benefit of urine source separation and there was little concern reported about the use of urine-based fertilizers. Statistical analyses showed that one's environmental attitude, environmental behavior, perceptions of support within the university community, and belief that student opinions have an impact on university decision makers were significantly correlated with one's support for urine source separation. This work helps identify community characteristics that lend themselves to acceptance of urine source separation, such as those related to environmental attitudes/behaviors and perceptions of behavioral control and subjective norm. Critical aspects of these alternative wastewater systems that require attention in order to foster public acceptance after implementation are also highlighted, such as convenient and aesthetically pleasing methods for waterless toilet paper disposal.

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.

Characteristics and DBP formation of dissolved organic matter from leachates of fresh and aged leaf litter

Dissolved organic matter (DOM) was leached from leaves of two trees commonly grown in subtropical regions, Pinus elliottii (commonly known as slash pine) and Schima superba (S. superba), and its degradation pattern and potential for forming disinfection byproducts (DBPs) were evaluated. The leaves were exposed in the field for up to one year before leaching. The DOM leached from slash pine litter contained on average 10.4 mg of dissolved organic carbon (DOC) per gram of dry weight; for S. superba the average was 37.2 mg-DOC/g-dry weight. Ultraviolet and visible light absorbance, fluorescence, and molecular weight analysis indicated that more aromatic/humic and higher molecular weight compounds are formed as leaf litter ages. A 4-component parallel factor analysis of the fluorescence data showed that the intensity of peaks related with protein-like components decreased gradually during biodegradation, while that of peaks attributed to humic-acid-like components increased continuously. Fresh slash pine leachates formed on average 40.0 μg of trihalomethane (THM) per milligram of DOC, while S. superba leachates formed 45.6 μg. THM formation showed peak values of 55.7 μg/mg DOC for slash pine and 74.9 μg/mg DOC for S. superba after 8 months of aging. The formation of haloacetonitrile (HAN) and trichloronitromethane (TCNM) increased with increasing leaf age, while chloral hydrate (CH) formation did not show such a trend. Specific UV absorbance showed some positive correlation with DBPs, but humic-acid-like and protein-like absorbance peaks correlated with CH and TCNM yields in only some leaf samples.

Development and validation of a novel modeling framework integrating ion exchange and resin regeneration for water treatment

Models have been developed to simulate the process of ion exchange for water treatment. However the modeling of resin regeneration process, which can predict regeneration efficiency and residual stream for determining technology sustainability, was not incorporated into previous models. Therefore a model integrating both ion exchange and resin regeneration considering regeneration efficiency is needed for evaluating and improving ion exchange technology. This study developed an integrated model aiming to simulate ion exchange and resin regeneration in different configurations (fixed bed, fluidized bed) for the first time. The integrated model has been validated via comparing model predictions with experimental data. The impacts of dimensionless groups (i.e. the Péclet number, the diffusion modulus, and the Biot number) on ion exchange breakthrough curve have been analyzed using this model. In addition, this integrated model has been used to optimize the regeneration frequency to improve the overall performance of ion exchange. It demonstrated this integrated model could be a useful tool for further studies in ion exchange technology.

Effects of natural organic matter on calcium and phosphorus co-precipitation

Phosphorus (P), calcium (Ca) and natural organic matter (NOM) naturally occur in all aquatic ecosystems. However, excessive P loads can cause eutrophic or hyper-eutrophic conditions in these waters. As a result, P regulation is important for these impaired aquatic systems, and Ca-P co-precipitation is a vital mechanism of natural P removal in many alkaline systems, such as the Florida Everglades. The interaction of P, Ca, and NOM is also an important factor in lime softening and corrosion control, both critical processes of drinking water treatment. Determining the role of NOM in Ca-P co-precipitation is important for identifying mechanisms that may limit P removal in both natural and engineered systems. The main goal of this research is to assess the role of NOM in inhibiting Ca and P co-precipitation by: (1) measuring how Ca, NOM, and P concentrations affect NOM's potential inhibition of co-precipitation; (2) determining the effect of pH; and (3) evaluating the precipitated solids. Results showed that Ca-P co-precipitation occurs at pH 9.5 in the presence of high natural organic matter (NOM) (≈30 mg L(-1)). The supersaturation of calcite overcomes the inhibitory effect of NOM seen at lower pH values. Higher initial P concentrations lead to both higher P precipitation rates and densities of P on the calcite surface. The maximum surface density of co-precipitated P on the precipitated calcite surface increases with increasing NOM levels, suggesting that NOM does prevent the co-precipitation of Ca and P.

Life cycle comparison of centralized wastewater treatment and urine source separation with struvite precipitation: Focus on urine nutrient management

Alternative approaches to wastewater management including urine source separation have the potential to simultaneously improve multiple aspects of wastewater treatment, including reduced use of potable water for waste conveyance and improved contaminant removal, especially nutrients. In order to pursue such radical changes, system-level evaluations of urine source separation in community contexts are required. The focus of this life cycle assessment (LCA) is managing nutrients from urine produced in a residential setting with urine source separation and struvite precipitation, as compared with a centralized wastewater treatment approach. The life cycle impacts evaluated in this study pertain to construction of the urine source separation system and operation of drinking water treatment, decentralized urine treatment, and centralized wastewater treatment. System boundaries include fertilizer offsets resulting from the production of urine based struvite fertilizer. As calculated by the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI), urine source separation with MgO addition for subsequent struvite precipitation with high P recovery (Scenario B) has the smallest environmental cost relative to existing centralized wastewater treatment (Scenario A) and urine source separation with MgO and Na3PO4 addition for subsequent struvite precipitation with concurrent high P and N recovery (Scenario C). Preliminary economic evaluations show that the three urine management scenarios are relatively equal on a monetary basis (<13% difference). The impacts of each urine management scenario are most sensitive to the assumed urine composition, the selected urine storage time, and the assumed electricity required to treat influent urine and toilet water used to convey urine at the centralized wastewater treatment plant. The importance of full nutrient recovery from urine in combination with the substantial chemical inputs required for N recovery via struvite precipitation indicate the need for alternative methods of N recovery.

Degradation of pharmaceuticals and metabolite in synthetic human urine by UV, UV/H2O2, and UV/PDS

To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09-8.53) × 10(9) M(-1)·s(-1) with hydroxyl radical, and (2.35-16.1) × 10(9) M(-1)·s(-1) with sulfate radical. In fresh urine matrix, the pharmaceuticals' indirect photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the indirect photolysis was strongly affected by inorganic urine constituents. Chloride had no apparent impact on UV/H2O2, but significantly raised the hydroxyl radical concentration in UV/PDS. Carbonate species reacted with hydroxyl or sulfate radical to generate carbonate radical, which degraded SMX and TMP, primarily due to the presence of aromatic amino group(s) (k = 2.68 × 10(8) and 3.45 × 10(7) M(-1)·s(-1)) but reacted slowly with acetyl-SMX. Ammonia reacted with hydroxyl or sulfate radical to generate reactive nitrogen species that could react appreciably only with SMX. Kinetic simulation of radical concentrations, along with products analysis, helped elucidate the major reactive species in the pharmaceuticals' degradation. Overall, the AOPs' performance was higher in the hydrolyzed urine than fresh urine matrix with UV/PDS better than UV/H2O2, and varied significantly depending on pharmaceutical's structure.

Predictive capability of chlorination disinfection byproducts models

There are over 100 models that have been developed for predicting trihalomethanes (THMs), haloacetic acids (HAAs), bromate, and unregulated disinfection byproducts (DBPs). Until now no publication has evaluated the variability of previous THM and HAA models using a common data set. In this article, the standard error (SE), Marquardt's percent standard deviation (MPSD), and linear coefficient of determination (R(2)) were used to analyze the variability of 87 models from 23 different publications. The most robust models were capable of predicting THM4 with an SE of 48 μg L(-1) and HAA6 with an SE of 15 μg L(-1), both achieving R(2) > 0.90. The majority of models were formulated for THM4. There is a lack of published models evaluating total HAAs, individual THM and HAA species, bromate, and unregulated DBPs.

Ion-exchange selectivity of diclofenac, ibuprofen, ketoprofen, and naproxen in ureolyzed human urine

This research advances the knowledge of ion-exchange of four non-steroidal anti-inflammatory drugs (NSAIDs) - diclofenac (DCF), ibuprofen (IBP), ketoprofen (KTP), and naproxen (NPX) - and one analgesic drug-paracetamol (PCM) - by strong-base anion exchange resin (AER) in synthetic ureolyzed urine. Freundlich, Langmuir, Dubinin-Astakhov, and Dubinin-Radushkevich isotherm models were fit to experimental equilibrium data using nonlinear least squares method. Favorable ion-exchange was observed for DCF, KTP, and NPX, whereas unfavorable ion-exchange was observed for IBP and PCM. The ion-exchange selectivity of the AER was enhanced by van der Waals interactions between the pharmaceutical and AER as well as the hydrophobicity of the pharmaceutical. For instance, the high selectivity of the AER for DCF was due to the combination of Coulombic interactions between quaternary ammonium functional group of resin and carboxylate functional group of DCF, van der Waals interactions between polystyrene resin matrix and benzene rings of DCF, and possibly hydrogen bonding between dimethylethanol amine functional group side chain and carboxylate and amine functional groups of DCF. Based on analysis of covariance, the presence of multiple pharmaceuticals did not have a significant effect on ion-exchange removal when the NSAIDs were combined in solution. The AER reached saturation of the pharmaceuticals in a continuous-flow column at varying bed volumes following a decreasing order of DCF > NPX ≈ KTP > IBP. Complete regeneration of the column was achieved using a 5% (m/m) NaCl, equal-volume water-methanol solution. Results from multiple treatment and regeneration cycles provide insight into the practical application of pharmaceutical ion-exchange in ureolyzed urine using AER.

Evaluating UV/H₂O₂, UV/percarbonate, and UV/perborate for natural organic matter reduction from alternative water sources

Natural organic matter (NOM) continues to increase in drinking water sources due to many factors, including changes in land use and global climate. Water treatment facilities will need to evaluate the best treatment options to account for these higher NOM levels. The UV/H₂O₂ advanced oxidation process (AOP) is one treatment option that has shown success at reducing high levels of NOM. As a result, this study evaluated the UV/H₂O₂ for the reduction of NOM in a high NOM water matrix, the Florida Everglades. In addition to liquid H₂O₂, sodium percarbonate and sodium perborate were used as oxidants to evaluate their performance as alternatives to liquid H₂O₂. Results showed that all three oxidants were able to reduce aromatic carbon (UV₂₅₄) by 46-66% and dissolved organic carbon (DOC) by 11-19% at UV fluences of 2.6-2.7 J cm(-2) and an H₂O₂ dose of 100 mg L(-1). When the UV fluences were increased to 21.8-26.1 J cm(-2) at an H₂O₂ dose of 100 mg L(-1), UV₂₅₄ reduction increased to 79-97% and DOC to 42-82% for all three oxidants. All three oxidants performed statistically similar for UV₂₅₄ reduction. However, for DOC reduction, H₂O₂ performed statically better than both percarbonate and perborate, and perborate performed statistically better than percarbonate. While the UV/H₂O₂ AOP is effective for NOM reduction in high NOM waters, advances in electrical efficiency are needed to make it economically feasible.

Diclofenac removal in urine using strong-base anion exchange polymer resins

One of the major sources of pharmaceuticals in the environment is wastewater effluent of which human urine contributes the majority of pharmaceuticals. Urine source separation has the potential to isolate pharmaceuticals at a higher concentration for efficient removal as well as produce a nutrient byproduct. This research investigated the efficacy of using strong-base anion exchange polymer resins to remove the widely detected and abundant pharmaceutical, diclofenac, from synthetic human urine under fresh and ureolyzed conditions. The majority of experiments were conducted using a strong-base, macroporous, polystyrene resin (Purolite A520E). Ion-exchange followed a two-step removal rate with rapid removal in 1 h and equilibrium removal in 24 h. Diclofenac removal was >90% at a resin dose of 8 mL/L in both fresh and ureolyzed urine. Sorption of diclofenac onto A520E resin was concurrent with desorption of an equivalent amount of chloride, which indicates the ion-exchange mechanism is occurring. The presence of competing ions such as phosphate and citrate did not significantly impact diclofenac removal. Comparisons of three polystyrene resins (A520E, Dowex 22, Dowex Marathon 11) as well as one polyacrylic resin (IRA958) were conducted to determine the major interactions between anion exchange resin and diclofenac. The results showed that polystyrene resins provide the highest level of diclofenac removal due to electrostatic interactions between quaternary ammonium functional groups of resin and carboxylic acid of diclofenac and non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Diclofenac was effectively desorbed from A520E resin using a regeneration solution that contained 4.5% (m/m) NaCl in an equal-volume mixture of methanol and water. The greater regeneration efficiency of the NaCl/methanol-water mixture over the aqueous NaCl solution supports the importance of non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Experiments with ketoprofen, in addition to diclofenac, suggest that polystyrene anion exchange resins can be used to selectively remove other acidic pharmaceuticals from urine.