Reuse Facilities Research Articles

Pretreatment for potable reuse: Enhancing the biological removal of 1,4-dioxane from landfill leachate through cometabolism with tetrahydrofuran.

1,4-Dioxane is a probable human carcinogen and a persistent aquatic contaminant. Cometabolic biodegradation of 1,4-dioxane is a promising low-cost and effective treatment technology; however, further demonstration is needed for treating landfill leachate. This technology was tested in two full-scale moving bed biofilm reactors (MBBRs) treating raw landfill leachate with tetrahydrofuran selected as the cometabolite. The raw leachate contained on average 82 μg/L of 1,4-dioxane and before testing the MBBRs removed an average of 38% and 42% of 1,4-dioxane, respectively. First, tetrahydrofuran was added to MBBR 1, and 1,4-dioxane removal was improved to an average of 73%, with the control MBBR removing an average of 37% of 1,4-dioxane. During this period, an optimal dose of 2mg/L of tetrahydrofuran was identified. Tetrahydrofuran was then fed to both MBBRs, where the 1,4-dioxane removal was on average 73% and 80%. Cometabolic treatment at the landfill significantly reduced the concentration of 1,4-dioxane received from the landfill at a downstream wastewater treatment and indirect potable reuse facility, reducing the load of 1,4-dioxane from 44% to 24% after the study. PRACTITIONER POINTS: Cometabolic degradation of leachate 1,4-dioxane with THF in MBBRs is a feasible treatment technology and a low-cost technique when retrofitting existing biological treatment facilities. The MBBRs can be operated at a range of temperatures, require no operational changes beyond THF addition, and operate best at a mass ratio of THF to 1,4-dioxane of 24. Source control of 1,4-dioxane significantly reduces the concentration of 1,4-dioxane in downstream wastewater treatment plants and potable reuse facilities.

Water Reuse in the Hill Country: Lessons from Existing Reuse Facilities in Texas and Opportunities to Advance Reuse in Comal County

The Greater Edwards Aquifer Alliance outlines the opportunities present in the Texas Hill Country to use recycled water to alleviate the burdens placed on the Edwards and Trinity aquifers by focusing on the present state of recycled water use in Comal County, Texas. The impacts of population growth, prolonged drought, and wastewater disposal on water sources in Comal County are analyzed along with current sources of water reuse to show where recycled water can be utilized effectively. Reclaimed water systems in seven municipalities across Texas are analyzed as case studies to provide examples for further implementation. Water reuse is integral to protecting water supplies and ensuring counties in the Hill Country can adequately protect the health, safety, and quality of life of current and future residents. Water reuse is a vastly underutilized tool in the effort to manage water supplies in the Hill Country, and there are a variety of authorization, financing, and implementation opportunities present in the region to take better advantage of this resource.

Using unsupervised learning to classify inlet water for more stable design of water reuse in industrial parks.

The water reuse facilities of industrial parks face the challenge of managing a growing variety of wastewater sources as their inlet water. Typically, this clustering outcome is designed by engineers with extensive expertise. This paper presents an innovative application of unsupervised learning methods to classify inlet water in Chinese water reuse stations, aiming to reduce reliance on engineer experience. The concept of 'water quality distance' was incorporated into three unsupervised learning clustering algorithms (K-means, DBSCAN, and AGNES), which were validated through six case studies. Of the six cases, three were employed to illustrate the feasibility of the unsupervised learning clustering algorithm. The results indicated that the clustering algorithm exhibited greater stability and excellence compared to both artificial clustering and ChatGPT-based clustering. The remaining three cases were utilized to showcase the reliability of the three clustering algorithms. The findings revealed that the AGNES algorithm demonstrated superior potential application ability. The average purity in six cases of K-means, DBSCAN, and AGNES were 0.947, 0.852, and 0.955, respectively.

Methyl nitrate as a byproduct in advanced water treatment systems: Liquid chromatographic determination method and cause of formation

Neutral low-molecular-weight organics such as methyl nitrate that can readily pass through reverse osmosis (RO) membranes employed in potable water reuse facilities attract interest owing to public health considerations. In this study, a novel determination method based on high-performance liquid chromatography, online photochemical conversion to peroxynitrite, and luminol chemiluminescence detection was developed for methyl nitrate measurement in treated water. The maximum photochemical conversion efficiency of methyl nitrate to peroxynitrite was found to be 6.5% using a 222-nm excimer lamp. The calibration curve for the developed method was linear between 1.0 × 10−9 and 1.0 × 10−7 M, and the limit of detection was 0.3 nM (0.03 μg/L) given an injection volume of 200 μL. The methyl nitrate concentrations in RO permeate from reclaimed wastewater and product water after subsequent treatment by a UV/H2O2 advanced oxidation process (AOP) were 2.2 and 22.5 nM (0.17 and 1.7 μg/L), respectively. UV irradiation of RO permeate in the laboratory using a low-pressure Hg lamp confirmed the formation of methyl nitrate in the permeate in the absence of H2O2 and residual chloramines. This chemiluminescent detection method for methyl nitrate will promote a greater understanding of the origin and formation of this treatment byproduct in reclaimed wastewater.

Unlocking system transitions for municipal solid waste infrastructure: A model for mapping interdependencies in a local context

Rapid global urbanization, urban renewal and changes in people's lifestyles have led to both an increase in waste generation and more complex waste types. In response to these changes, many local governments have invested in municipal solid waste infrastructure (MSWI) to implement circular strategies. However, matching and bridging the costly and logistically complex MSWI with the dynamic social context is a central challenge. In this paper we aim to explore the interdependencies between MSWI and the local social system, and then conceptualize and empirically validate the systemic nature of MSWI. We first review the current MSW treatment methods, corresponding infrastructure, and the challenges facing them. Then, we interrogate system-oriented concepts and use two key insights to set up a conceptual model for mapping the interdependencies in a MSWI system (MSWIS). Finally, a case study of the Dutch city of Almere is used to empirically validate the MSWIS model and identify the social systems that contribute to the development of the MSWIS. The analysis reveals that the development of MSWIS is beyond the municipality's control: efficient resource recovery facilities established by businesses under market rules and waste reuse facilities constructed by social organizations/individuals based on their own needs are key pieces of the puzzle to complete the MSWIS. This highlights the ability of the framework to capture interdependencies that go further than just the formal municipal sphere of influence.

A multi-stakeholder digital platform for regional construction and demolition waste management.

Little attention has been paid to the interaction or synergy among construction and demolition (C&D) waste management stakeholders. A framework allowing for interaction among the various C&D waste players is especially important in regions with mature C&D waste infrastructure, where various recycling, reuse and disposal facilities are present. In such an expanded infrastructure, these facilities differ in terms of the C&D waste materials they accept, the nature of the waste accepted (sorted/unsorted), as well as the services they provide. This makes developing the optimal C&D waste management plan (WMP) more cumbersome for contractors. To address the challenges arising from the poor dynamics associated with the overarching waste management infrastructure, this paper proposes a novel digital platform, namely the 'Construction and Demolition Waste Management Kernel' (C&D WMK). The C&D WMK has three main objectives: it allows for data exchange between the different stakeholders, provides guidance to contractors when developing C&D WMPs and allows for governmental supervision and regulation. This paper introduces the concept behind the C&D WMK, presents the optimization model embedded in the system, and demonstrates its application in a case study leveraging real-world data. Finally, a scenario analysis is conducted to show how the C&D WMK can be used by governments to identify pitfalls in the state of practice at the regional scale, and to determine effective solutions to enhance the C&D waste management performance.

Photolysis of chloramines in vacuum-UV and vacuum-UV/chlorine advanced oxidation processes for removal of 1,4-dioxane: Effect of water matrix, kinetic modeling, and implications for potable reuse

Advanced oxidation processes (AOPs) are a key step in eliminating persistent micropollutants in potable reuse trains. Under such conditions, chloramines are an inevitable component in the AOP feed water given their application as an antifouling agent for the upstream membrane processes. In cases when other oxidants, such as free chlorine, are to be used in the AOP treatment, the effect of background chloramines and any potential interplays between the oxidants should be considered. In this study, vacuum-UV (VUV) and VUV/Cl2 have been proposed as promising AOP alternatives for potable reuse and the effect of chloramine photolysis has been considered on the removal of 1,4-dioxane. Results indicated that while presence of chloramine reduces the treatment efficiency in the VUV AOP, coexistence of free chlorine and chloramine oxidants significantly improves 1,4-dioxane degradation rates. Experimental data and kinetic modeling both confirmed the roles of OH• and Cl2•- in 1,4-dioxane removal with 62.5% and 32.5% contribution in the VUV/Cl2/chloramines, respectively. Among the other water matrix conditions, Cl- was shown to improve the degradation rates while HCO3- suppressed the reactions by scavenging radical species. Overall, the findings of this research are informative for the design and development of VUV AOPs at small scale potable reuse facilities.

Chlorotyrosines and Oleic Acid Chlorohydrins as Byproducts in Disinfected Conventional Drinking Waters and Potable Reuse Waters

Recent research indicates that the poorly characterized high-molecular weight disinfection byproduct (DBP) fraction (more than two carbons) contributes more to cytotoxicity than the one- to two-carbon DBPs of current interest. Peptides and lipids contribute to DBP precursors in water supplies. Although partially degraded, a portion of their monomers retain their structures. Using tyrosine and oleic acid as exemplars, this study illustrates the targeted analysis of their chlorinated byproducts as an approach to characterizing high-molecular weight DBPs. After biopolymers had been digested to liberate monomers, oleic acid was detected in four of six secondary effluents from potable reuse facilities at concentrations of up to 91 nM (47 μg/L), while its chlorohydrins were detected in two effluents at concentrations of up to 1.3 nM (0.43 μg/L). Tyrosine was detected in all six effluent samples at concentrations of up to 42 nM (7.6 μg/L). 3-Chlorotyrosine was detected in four samples at concentrations of up to 3.3 nM (0.71 μg/L), and 3,5-dichlorotyrosine was detected in three samples at concentrations of up to 2.1 nM (0.53 μg/L). These DBPs were detected in conventional drinking waters, but at lower frequencies and concentrations. When detected, the contribution of chlorohydrins to cytotoxicity was comparable to some, but not all, of the one- to two-carbon DBP classes.

Tree Growth and Vegetation Diversity in Northern Idaho Forest Water Reclamation Facilities

Forest water reclamation can improve tree growth and renovate municipal wastewater. Although there are indications that long-term application may exceed forest assimilation capacity, there is limited information on the long-term effects of reclaimed water application on coniferous ecosystems. The purpose of our study was to assess the impacts of prolonged reclaimed water application on forest growth responses and vegetation diversity. We examined the effects of reclaimed water at five water reuse facilities established between 1978 and 2013 in a four-decade time series. We collected tree cores and stem measurements to determine current and retrospective increments. We assessed plant diversity with vegetation surveys. The greatest diameter response observed for reclaimed water amendment compared to controls was 166.1% for western redcedar, while Douglas-fir increased up to 116.4% and ponderosa pine increased up to 100.6%. The minimum response observed was 30.3%. Current annual increments showed that the basal area and volume were significantly greater at long-established facilities for reclaimed-water-amended plots. The understory vegetation diversity declined with application time, while overstory vegetation diversity increased with application time. We conclude that reclaimed water can be a valuable resource to improve forest productivity, but continued application without stocking control may have detrimental effects on forest growth and vegetation diversity.

Empirical Modeling of Bromate Formation and Chemical Control Strategies at Multiple Water Reuse Facilities Using Ozone

ABSTRACT As an increasing number of potable water reuse projects consider feasibility of implementing ozonation for achieving disinfection goals and removal of trace organic compounds, bromate formation presents a practical barrier. In this study, data received from five potable water reuse facilities showed that ozone dissolution method such as fine bubble diffusion resulted in lower concentrations of bromate compared to side-stream addition. When using multipoint ozone dissolution some reduction in bromate formation was also observed. Data from these facilities displayed a positive correlation between ozone (as a function of O3:TOC ratio) and bromate formation (as molar ratio of bromide converted to bromate) with lower formation as monochloramine or hydrogen peroxide concentrations increase. This study provides an empirical model with four equations which can be used to estimate the bromate formation and the required monochloramine or hydrogen peroxide dose to achieve adequate bromate control, i.e. below MCL of 10 µg/L, if a desired O3:TOC ratio and initial bromide concentration are known. The empirical model estimates for monochloramine and hydrogen peroxide were found to be in good agreement with experimental data (R2 = 0.96 and R2 = 0.87, respectively) while within a set of boundary conditions expressed by range of concentrations of typical water quality parameters.

Reuse of e-learning personalization components

Personalized learning systems use several components in order to create courses adapted to the learners’characteristics. Current emphasis on the reduction of costs of development of new resources has motivated the reuse of the e-learning personalization components in the creation of new components. Several systems have been proposed in the literature. Each system implements a specific approach and includes a set of software components. However, many of these components are not easily reusable. This paper proposes an architecture, which aims to improve the representation of learning components in a reusable and interoperable way. As a result, these components could be integrated easily for the creation of personalized learning courses. This architecture consists of five main packages: learner model, adaptation model, reuse facilities, learner interface and pedagogical knowledge. An experiment is conducted to validate the proposed architecture. The obtained results illustrate the optimal composition of e-learning personalization components through an example.

Out of Thin Air? Catalytic Oxidation of Trace Aqueous Aldehydes with Ambient Dissolved Oxygen.

Water reuse is expanding due to increased water scarcity. Water reuse facilities treat wastewater effluent to a very high purity level, typically resulting in a product water that is essentially deionized water, often containing less than 100 μg/L organic carbon. However, recent research has found that low-molecular-weight aldehydes, which are toxic electrophiles, comprise a significant fraction of the final organic carbon pool in recycled wastewater in certain treatment configurations. In this manuscript, we demonstrate oxidation of trace aqueous aldehydes to their corresponding acids using a heterogeneous catalyst (5% Pt on C), with ambient dissolved oxygen serving as the terminal electron acceptor. Mass balances are essentially quantitative across a range of aldehydes, and pseudo-first-order reaction kinetics are observed in batch reactors, with kobs varying from 0.6 h-1 for acetaldehyde to 4.6 h-1 for hexanal, while they are low for unsaturated aldehydes. Through kinetic and isotopic labeling experiments, we demonstrate that while oxygen is essential for the reaction to proceed, it is not involved in the rate-limiting step, and the reaction appears to proceed primarily through a base-promoted β-hydride elimination mechanism from the hydrated gem-diol form of the corresponding aldehyde. This is the first report we are aware of that demonstrates useful abiotic oxidation of a trace organic contaminant using dissolved oxygen.

Reclaiming wastewater with increasing salinity for potable water reuse: Water recovery and energy consumption during reverse osmosis desalination

With reverse osmosis membranes being industry-standard in many potable reuse facilities, an opportunity exists to desalinate higher-salinity streams (e.g., brine and regional brine interceptor streams) to augment traditional wastewater supplies and reduce brine disposal requirements. This study evaluates the energy consumed in recovering water from these streams at advanced water purification facilities. Scenarios without and with seawater inflow and infiltration at coastal wastewater reclamation facilities are considered. It was found that as wastewater salinity increases with increasing seawater inflow and infiltration, base case energy consumption increases, but the percent increase of energy consumption caused by mixing higher-salinity streams decreases. Multiple energy-saving strategies were evaluated, including energy recovery devices, closed-circuit reverse osmosis, and desalination of the higher-salinity streams separately from the treated wastewater. The energy savings was greater for closed-circuit reverse osmosis than for energy recovery devices and increased for both as influent salinity increases. The energy savings from desalinating higher-salinity streams separately increased as the salinity difference between the two streams increased. Addition of higher-salinity streams was also considered within the context of inorganic scaling potential, product water requirements, and discharge permits that may limit recoveries.

Experimental Study of Compressive Properties and Environmental Impact of Recycled Aggregate

As the main component of fiber-reinforced recycled aggregate concrete, the properties of recycled aggregate determine whether recycled aggregate concrete can be used in engineering applications. To study the compressive properties and environmental impact of recycled aggregate, large-scale indoor compression tests were carried out on recycled aggregate under different moisture contents, concrete aggregate ratios, dry-wet cycles, and loads. The results showed that the crushing rate and settlement first increased and then decreased upon increasing the moisture content. Upon increasing the concrete aggregate ratio, the settlement continuously decreased, and the crushing rate decreased from 157.2 to 82.5%. Upon increasing the number of dry-wet cycles, the settlement continued to increase to an upper limit of about 17.5%, and the crushing rate increased to 35%. Upon increasing the load, the settlement and crushing rate of the aggregate increased. These results show that the effects of aggregate ratio, moisture content, and dry-wet cycles on settlement were caused by crushing the aggregate. Based on this, a formula was constructed to predict the final settlement of reclaimed aggregate. The leaching amount of Cr in recycled aggregate was 0.0175–0.0375 mg/L under normal conditions, but under extreme conditions, the leaching amount of some sampling points was greater than in the standard requirements. This means that recycled aggregate may pose environmental risks that should be mitigated during use. Recycled aggregate can be used to construct sponge city storage and reuse facilities, as well as fiber-reinforced recycled aggregate concrete, but its sources need to be determined to ensure that it does not pose environmental risks.

Dissolved organic nitrogen in wastewater treatment processes: Transformation, biosynthesis and ecological impacts.

With the upgrade of wastewater treatment plants (WWTPs) to meet more stringent discharge limits for nutrients, dissolved organic nitrogen (DON) is present at an increasing percentage (up to 85%) in the effluent. Discharged DON is of great environmental concern due to its potentials in stimulating algal growth and forming toxic nitrogenous disinfection by-products (N-DBPs). This article systematically reviewed the characteristics, transformation and ecological impacts of wastewater DON. Proteins, amino acids and humic substances are the abundant DON compounds, but a large fraction (nearly 50%) of DON remains uncharacterized. Biological treatment processes play a dominant role in DON transformation (65-90%), where DON serves as both nutrient and energy sources. Despite of the above progress, critical knowledge gaps remain in DON functional duality, relationship with dissolved inorganic nitrogen (DIN) species, and coupling/decoupling with the dissolved organic carbon (DOC) pool. Development of more rapid and accurate quantification methods, modeling transformation processes, and assessing DON-associated eutrophication and N-DBP formation risks should be given priority in further investigations.

Development of the Urban Water Balance Model by Linking Water Distribution and Sewer Networks

Due to urban overcrowding, the population density of residential areas and water use per unit are increasing. Therefore, it is necessary to study the flow of water supplied to cities and to improve the healthy circulation of urban water. This study used Modelica, a non-causal analytical program. Using Open Modelica, the researchers constructed a model linking water distribution and sewerage, as the basis of a balanced urban water model. Using the programmer's toolkit provided by EPA-NET and EPA-SWMM, which are commonly used to simulate the existing water supply and sewage pipe networks, Open Modelica-based water distribution networks and sewage pipe networks can be connected and simulated based on the customer block. A model was built so that 90% of the hourly water consumption supplied to the water supply pipe network can be automatically introduced into the sewage pipe network. If a matching table is constructed to connect the nodes of the water supply pipe network and the sewer pipe network, the nodes will reflect in the graphical user interface (GUI) developed in Open Modelica. It was developed to enable modification of links, pumps, tanks, and valves. The 48-hour water supply was simulated using the developed model, and it was confirmed that water supply and sewage networks were successfully connected. In the future, we plan to develop a more expanded and realistic urban water circulation model by considering additional urban water circulation factors, such as sewage treatment, water reuse, rainwater use, storm runoff, and low-impact development facilities. Through this study, it was confirmed that Modelica can simulate changes in the system over time. Since it is a formula-based non-causal simulation language, it is possible to establish and reuse relationships between blocks through block-by-block development of urban water circulation elements. It is expected to contribute to the visualization and concretization of future urban water circulation models.

Formation and Fate of Carbonyls in Potable Water Reuse Systems.

Low molecular weight, uncharged compounds have been the subject of considerable study at advanced treatment plants employed for potable water reuse. However, previously identified compounds only account for a small fraction of the total dissolved organic carbon remaining after reverse osmosis treatment. Uncharged carbonyl compounds (e.g., aldehydes and ketones) formed during oxidation have rarely been monitored in potable water reuse systems. To determine the relative importance of these compounds to final product water quality, samples were collected from six potable water reuse facilities and one conventional drinking water treatment plant. Saturated carbonyl compounds (e.g., formaldehyde, acetone) and α,β-unsaturated aldehydes (e.g., acrolein, crotonaldehyde) were quantified with a sensitive new analytical method. Relatively high concentrations of carbonyls (i.e., above 7 μM) were observed after ozonation of wastewater effluent. Biological filtration reduced concentrations of carbonyls by over 90%. Rejection of the carbonyls during reverse osmosis was correlated with molecular weight, with concentrations decreasing by 33% to 58%. Transformation of carbonyls resulted in decreases in concentration of 10% to 90% during advanced oxidation, with observed decreases consistent with rate constants for reactions of the compounds with hydroxyl radicals. Overall, carbonyl compounds accounted for 19% to 38% of the dissolved organic carbon in reverse osmosis-treated water.

Removal of Pathogens and Chemicals of Emerging Concern by Pilot-Scale FO-RO Hybrid Units Treating RO Concentrate, Graywater, and Sewage for Centralized and Decentralized Potable Reuse

This study evaluated the water quality produced by forward osmosis-reverse osmosis (FO-RO) treatment at pilot scale of RO concentrate generated at centralized potable reuse facilities and of graywa...

Hybrid nitrate selective resin (NSR-NanoZr) for simultaneous selective removal of nitrate and phosphate (or fluoride) from impaired water sources

Reverse osmosis (RO) has been increasingly applied in municipal wastewater reuse facilities. Nitrate (N) and phosphate (P) -laden reject streams from RO demand near-complete NP removal before inland brine disposal to avoid serious eutrophication effects. In addition, elevated nitrate and fluoride levels in groundwater is a threat to public drinking water safety. Selective removal of both nitrate and phosphate, or fluoride through a single adsorbent is promising because of its small footprints, minimum sludge production, and potential NP recovery. This study presents a new ion exchange adsorbent, NSR-NanoZr, for simultaneous selective removal of both nitrate and phosphate, or fluoride. NSR-NanoZr is fabricated by doping zirconium oxide nanoparticles (ZrO2-Nano) into a nitrate selective resin (NSR), which tributyl quaternary ammonium functional groups contribute to the nitrate selectivity and Lewis acid-base interactions between ZrO2-Nano and ligands result in the high affinity towards phosphate and fluoride. Lab-scale studies showed that NSR-NanoZr exhibited a completely reversal selectivity and removed both NP selectively from municipal secondary wastewater for multiple cycles. Synergistic application of a weak-acid cation exchanger (WAC) enhanced the phosphate capacity of NSR-NanoZr due to the amphoteric sorption behavior of the ZrO2-Nano. Field-scale studies demonstrated the potential of NSR-NanoZr in removing fluoride together with nitrate.

The Impact of Advanced Treatment Technologies on the Energy Use in Satellite Water Reuse Plants

With an ever-increasing world population and the resulting increase in industrialization and agricultural practices, depletion of one of the world’s most important natural resources, water, is inevitable. Water reclamation and reuse is the key to protecting this natural resource. Water reclamation using smaller decentralized wastewater treatment plants, known as satellite water reuse plants (WRP), has become popular in the last decade. Reuse plants have stricter standards for effluent quality and require a smaller land footprint (i.e., real estate area). They also require additional treatment processes and advanced treatment technologies. This greatly increases the energy consumption of an already energy intensive process, accentuating even more the nexus between energy use and wastewater processing. With growing concerns over the use of nonrenewable energy sources and resulting greenhouse gas (GHG) emissions, WRPs are in need of energy evaluations. This paper contrasts the energy consumption of both conventional and advanced treatment processes in satellite WRPs. Results of this research provide a means for engineers and wastewater utilities to evaluate unit processes based on energy consumption as well as a foundation for making decisions regarding the sustainability of using advanced treatment technologies at reuse facilities.