Potable Reuse Research Articles

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.

Pilot-scale demonstration of dissolved organic nitrogen removal from an advanced water reclamation facility using enhanced coagulation

Most wastewater treatment facilities that satisfy stricter discharge restrictions for nutrients, remove dissolved inorganic nitrogen (DIN) species efficiently, leaving dissolved organic nitrogen (DON) to be present at a higher proportion (up to 85 %) of total nitrogen (TN) in the effluent. Discharged DON promotes algae growth in receiving water bodies and is a growing concern in effluent potable reuse applications considering its potential to form hazardous nitrogenous disinfection byproducts (N-DBPs). Enhanced coagulation is an established process in the advanced water treatment train for most potable reuse applications. However, so far, no information has been collected at the pilot scale to address DON removal efficiency and process implications by enhanced coagulation under real conditions. This study performed a comprehensive evaluation of DON removal from the effluent of the Truckee Meadows Water Reclamation Facility (TMWRF) by enhanced coagulation over the course of 11 months at the pilot scale. Three different coagulants (aluminum sulfate (alum), poly‑aluminum chloride (PACl), ferric chloride (FC)) and a cationic polymer coagulant aid (Clarifloc) were used. Optimum doses for each coagulant and polymer and ideal pH were determined by jar tests and applied at the pilot. Alum (24 mg/L) resulted in highly variable DON removal (6 % – 40 %, 21 % on average), which was enhanced by the addition of polymer, leading to 32 % DON removal on average. PACl (40 mg/L) and FC (100 mg/L) resulted in more consistent DON removal (on average 45 % and 57 %, respectively); however, polymer addition exerted minimal enhancement for these coagulants. Overall, enhanced coagulation effectively reduced DON in the tertiary effluent at the pilot scale. The treatment showed auxiliary benefits, including dissolved organic carbon (DOC) and orthophosphate removal.

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.

Understanding questions and concerns about potable water reuse: An analysis of survey write‐in responses

AbstractUrban centers around the world are grappling with the challenges associated with population increases, drought, and projected water shortages. Potable water reuse (i.e., purification of municipal wastewater for reuse as drinking water) is an option for supplementing existing water supplies. Public perception research on potable water reuse has predominantly employed surveys with multiple‐choice questions that constrain survey respondents to describe their concerns by choosing from several response options. This research examines hundreds of write‐in responses to a large public survey in Albuquerque, New Mexico, to provide a detailed analysis of residents' questions and concerns about potable water reuse. Findings demonstrate that allowing respondents to voice their actual concerns adds richness and nuance that cannot be obtained from multiple‐choice response data alone. Especially with controversial resource considerations, such as potable water reuse, planners would benefit from a full understanding of the problem before engaging with the community.

Efficacy of simultaneous advanced oxidation and adsorption for treating municipal wastewater for indirect potable reuse

The main scope of this study was to compare the efficacy of different advanced oxidation processes (AOPs) combined with adsorption for treating secondary treated effluent of municipal wastewater in a continuous-lab-scale reactor. The results revealed enhanced removal of biological oxygen demand (BOD: C0: 14.1 and Ct: 0 mg L−1 (100%)), chemical oxygen demand (COD: C0: 40.5 and Ct: 4 mg L−1 (≤90%)), and total organic carbon (TOC: C0: 15.2 and Ct: 3.02–3.63 mg L−1 (∼80%)) by UV/PMS, O3/PMS, UV/O3/H2O2, and UV/O3/MnO2 processes followed by glass packed bed reactor (GPBR). Complete inactivation of the bacterial count was observed for all the studied processes. The GPBR showed the additional advantage of termination in the regrowth of bacterial count on the filtering medium. The gas-chromatography and mass spectrometry (GC-MS) analysis showed that AOP followed by adsorption reduced the concentrations of the by-products in the treated effluent. Overall, the synergy between AOP and adsorption improved the effluent quality to meet various indirect potable reuse (IPR) applications.

Comparison of Oxidants Used in Advanced Oxidation for Potable Reuse: Non-Target Analysis and Bioassays

Free chlorine (HOCl) and monochloramine (NH2Cl) are less-used oxidants than hydrogen peroxide (H2O2) in ultraviolet advanced oxidation processes (UV-AOPs) but have garnered interest from the water reuse industry and scientific community because they can be more cost-effective than H2O2 and provide a protective disinfectant residual. The destruction of organic compounds, creation of UV-AOP byproducts, and change in toxicity during UV-AOP with H2O2, HOCl, NH2Cl, or ambient residual chloramine were evaluated in recycled wastewater by suspect and non-target screening as well as bioanalytical tests (bioassays). Ten compounds were identified in reverse osmosis (RO) permeate via suspect screening with removal near 100% by UV/H2O2 and UV/HOCl, greater than decomposition by UV/NH2Cl and UV/ambient (∼60%), based on suspect screening mass spectrometry peak area. Non-target analysis based on organic features in mixed-mode cation exchange cartridge extracts indicated that UV/H2O2 destroyed a similar or slightly greater fraction of organic compounds, formed fewer transformation products, and reduced the summed peak area of non-target features to the greatest extent. Fewer chlorinated byproducts were produced from the RO permeate treated by UV/H2O2 than exposure to the chlorine-containing oxidants. Addition of NH2Cl to RO permeate resulted in a slight increase in the bioassay oxidative stress response but dropped below the response limit for all samples after UV-AOP for all oxidants.

Control of Pre-formed Halogenated Disinfection Byproducts with Reuse Biofiltration.

Disinfection byproduct (DBP) pre-formation is a major issue when prechlorination is used before or during advanced treatment of impacted drinking water sources. Control strategies for pre-formed DBPs before final disinfection, especially for currently nonregulated although highly toxic DBP species, are not yet established. This study evaluated the biodegradation potential of pre-formed DBPs, including haloacetonitriles (HANs), haloacetamides (HAMs), and haloacetaldehydes (HALs), during biofiltration with sand, anthracite, and biological activated carbon of three wastewater effluents under potable reuse conditions. Up to 90%+ removal of di- and trihalogenated HANs, HAMs, and HALs was observed, and removal was associated with active heterotrophic biomass and removal of biodegradable organic carbon. Unlike the microbial dehalogenation pathway of haloacetic acids (HAAs), removal of HANs and HAMs appeared to result from a biologically mediated hydrolysis pathway (i.e., HANs to HAMs and HAAs) that may be prone to inhibition. After prechlorination, biofiltration effectively controlled pre-formed DBP concentrations (e.g., from 271 μg/L to as low as 22 μg/L in total) and DBP-associated calculated toxicity (e.g., 96%+ reduction). Abiotic residual adsorption capacity in biological activated carbon media was important for controlling trihalomethanes. Overall, the toxicity-driving DBP species exhibited high biodegradation potential and biofiltration showed significant promise as a pre-formed DBP control technology.

Life cycle energy use and greenhouse gas emissions for a novel algal-osmosis membrane system versus conventional advanced potable water reuse processes: Part I

This study applied a life cycle assessment (LCA) methodology for a comparative environmental analysis between an innovative algae resource recovery and near zero-liquid discharge potable reuse system (i.e., the main system) versus a conventional potable reuse system (i.e., the benchmark system) through energy use and greenhouse gas (GHG) emissions. The objective of this study is to demonstrate that pilot-scale data coupled with LCA would provide valuable information for system optimization, integration, and improvements for the design of environmentally sustainable full-scale systems. This study also provides decision-makers valuable information regarding the energy demand and environmental impact of this innovative main system compared to a typical tried-and-true system for potable water reuse. The main system consists of a novel algal-based wastewater treatment coupled with a dual forward osmosis and seawater reverse osmosis (Algal FO-SWRO) membranes system for potable water recovery and hydrothermal liquefaction (HTL) to recover biofuels and valuable nutrients from the harvested algal biomass. The benchmark system refers to the current industry standard technologies for potable water reuse and waste management including a secondary biological treatment, microfiltration (MF), brackish water reverse osmosis (BWRO), ultraviolet/advanced oxidation process (UV-AOP), and granular activated carbon (GAC), as well as anaerobic digestion for sludge treatment. Respective energy and GHG emissions of both systems were normalized and compared considering 1 m3 of water recovered. Based on an overall water recovery of 76% designed for the benchmark system, the energy consumption totaled 4.83 kWh/m3, and the system was estimated to generate 2.42 kg of CO2 equivalent/m3 with most of the emissions coming from the biological treatment. The main system, based on an overall water recovery of 88%, was estimated to consume 4.76 kWh/m3 and emit 1.49 kg of CO2 eq/m3. The main system has high environmental resilience and can recover bioenergy and nutrients from wastewater with zero waste disposal. With the application of energy recovery devices for the HTL and the SWRO, increase in water recovery of the FO membrane, and replacement of the SWRO membrane with BWRO, the main system provides an energy-competitive and environmentally positive alternative with an energy demand of 2.57 kWh/m3 and low GHG emissions of 0.94 kg CO2 eq/m3.

Techno-economic assessment of a novel algal-membrane system versus conventional wastewater treatment and advanced potable reuse processes: Part II

This study developed a comprehensive techno-economic assessment (TEA) framework to evaluate an innovative algae resource recovery and near zero-liquid discharge potable reuse system (i.e., the main system) in comparison with a conventional potable water reuse system (i.e., the benchmark system). The TEA study aims to estimate the levelized costs of water of individual units and integrated processes including secondary wastewater treatment, advanced water purification for potable reuse, and sludge treatment. This would provide decision-makers valuable information regarding the capital and operational costs of the innovative main system versus a typical potable water reuse treatment train, along with possible routes of cost optimization and improvements for the design of full-scale facilities. The main system consists of (i) a novel algal-based wastewater treatment coupled with a dual forward osmosis and seawater reverse osmosis (Algal FO-SWRO) membranes system for potable water reuse and hydrothermal liquefaction (HTL) to produce bioenergy and subsequent nutrients extraction from the harvested algal biomass. The benchmark system includes (ii) an advanced water purification facility (AWPF) that consists of a conventional activated sludge biological treatment (CAS), microfiltration (MF), brackish water reverse osmosis (BWRO), ultraviolet/advanced oxidation process (UV-AOP), and granular activated carbon (GAC), with anaerobic digestion for sludge treatment. Capital expenditures (CAPEX) and operational expenditures (OPEX) were calculated for each unit of both systems (i.e., sub-systems). Based on a 76% overall water recovery designed for the benchmark system, the water cost was estimated at $2.03/m3. The highest costs in the benchmark system were found on the CAS and the anaerobic digester, with the UV-AOP combined with GAC for hydrogen peroxide (H2O2) quenching as the driving factor in the increased costs of the system. The cost of the main system, based on an overall 88% water recovery, was estimated to be $1.97/m3, with costs mostly driven by the FO and SWRO membranes. With further cost reduction and optimization for FO membranes such as membrane cost, water recovery, and flux, the main system can provide a much more economically viable alternative in its application than a typical benchmark system.

Identifying and aggregating high-quality pathogen data: a new approach for potable reuse regulatory development

Studies measuring pathogens in wastewater were screened based on data relevance and quality criteria. Distributions of aggregated datasets can be used to support development of pathogen treatment requirements for direct potable reuse.

Characterization of Reverse Osmosis Reject Wastewater Generated from Sulaibiya Wastewater Treatment Plant

Sulaibiya Wastewater Treatment Plant (Kuwait) is considered as one of the largest wastewater treatment plants that use Reverse Osmosis (RO) membranes in their processes to reclaim water from municipal wastewaters for indirect potable water reuse. This result in considerable wastewater treatment brine which needs to be further investigated before discharge. Samples were collected on daily basis from the RO reject wastewater (brine wastewater) for one month and analyzed in situ and in the laboratory. The results obtained showed that the brine wastewater met the requirements of the Kuwait Environment Public Authority with the exception of biochemical oxygen demand, total dissolved solids, and total phosphate. In Kuwait, the brine wastewater is either used for deep-well injection or is discharged to the seawater. Based on the monitoring results, potential reuse options of wastewater brine include surface water discharge, sewer disposal, deep-well injection, and land application. Treatment options via evaporation ponds using membrane filters will further enhance the quality of the brine wastewater.

Science-based pathogen treatment requirements for direct potable reuse

This study specifies science-based pathogen treatment requirements for direct potable reuse using high-quality monitoring data and probabilistic approaches to ensure consistent and reliable protection of public health.

Stay in the loop: lessons learned about the microbial water quality in pipe loops transitioned from conventional to direct potable reuse water

A transition from a conventional drinking water system to direct potable reuse was simulated in pilot-scale pipe loops. To our knowledge, this study is the first to investigate the microbial impacts of the transition to treated water augmentation.

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.

Potable Reuse and PFAS

Key Takeaways Per‐ and polyfluoroalkyl substances (PFAS) are concerns in water sources because of their potential health effects, widespread detection, and environmental persistence. Potable reuse guidelines and regulations often include monitoring requirements for contaminants of emerging concern. Advanced water treatment technologies used in potable reuse, primarily reverse osmosis and granular activated carbon, are effective at removing PFAS. Regulatory frameworks for potable reuse and PFAS management are evolving at the same time; each framework needs to consider aspects of the other.

Epoxy lining influence on recycled water quality during pipeline transit for potable reuse.

An epoxy treatment was applied to a pipeline used to convey advanced treated recycled water from a purification facility to a recharge site. The epoxy treatment was applied to prevent further deterioration (corrosion) of the interior cement mortar lining (CML). A soil column study was conducted to evaluate the effect of the epoxy liner on the clogging potential of water before and after conveyance. The clogging potential was represented by differences in the column's relative hydraulic conductivity and water quality, between the treatment plant and injection site, before and after epoxy lining. Hydraulic conductivity of columns at the injection well site declined rapidly before epoxy and improved considerably after epoxy application. Total suspended solids (TSS) and cellular adenosine triphosphate (cATP) median concentrations improved significantly. Before epoxy, TSS increased with pipeline transit from 0.005 to 0.053 (mg/L) compared with 0.009 mg/L after epoxy. Before epoxy, cATP increased from 0.14 to 1.6pg/ml across pipeline transit compared with 0.37 pg/ml after epoxy. Aluminum and nitrate followed similar trends. Results indicate that epoxy liner reduced the clogging potential of high purity recycled water, likely due to a decrease in particle and biomass load (clogging constituents) accumulated during pipeline transit. PRACTITIONER POINTS: Clogging potential of advanced treated recycled water increases with pipeline transit. Epoxy lining the pipeline used for conveyance reduces the particulate and microbial loading of the highly purified water. Applying epoxy to pipelines used to convey advanced treated recycled water has the dual benefit of infrastructure protection and improving water quality. Reducing particle and microbial load in the advanced treated recycled water can reduce maintenance frequencies and elongate production periods for MAR applications.

Combined process of chemically enhanced sedimentation and rapid filtration for urban wastewater treatment for potable reuse

ABSTRACT The objective of this study is to propose a new post-treatment of effluents from Upflow Anaerobic Sludge Blanket (UASB) using rapid filtration, aiming at the production of water for potable reuse. The final quality of the effluent produced by the treatment using gravel, sand, clinoptilolite and activated carbon associated with disinfection was evaluated by physical chemical analysis, heavy metals and persistent organic contaminants. Experiments were carried out in jar test, filter operation time, evaluation of the efficiency using peracetic acid and free chlorine as disinfectant and all results were statistically analysed. The best conditions were those using 20 mg/L of ferric chloride and natural pH of the effluent (≈ 7.0), which resulted in less reagent consumption. The use of intermediate fund discharges made it possible to obtain approximately 91% of recovered water efficiency. The effluent treated under these conditions showed DOC <2.0 mg/L, COD <1.0 mg/L, BOD <1.0 mg/L, turbidity <1.0 NTU, TSS <1.0 mg/L, ammonia <0.1 mg/L, total phosphorus <0.1 mg/L and surfactants <0.1 mg/L. The disinfection process with free chlorine and PAA allowed the total inactivation of faecal coliforms and total coliforms. The treatment using rapid filtration with disinfection by chlorine reached the appropriate level for urban, environmental, industrial and indirect potable water reuse.

A comparative evaluation of reverse osmosis membrane performance when combined with anaerobic or aerobic membrane bioreactors for indirect potable reuse applications

The filtration performance and fouling behaviour of reverse osmosis (RO) membranes was investigated for the post-treatment of aerobic (Ae) and anaerobic (An) MBR effluents treating municipal wastewater for potable reuse. Both MBR effluents followed by RO can produce a water quality sufficient for indirect potable water reuse, while fluorescence excitation-emission scan suggests RO can effectively remove disinfection by-products precursors, ensuring the safety for chlorine based reuse water distribution by rejecting the dissolved organic matters in MBR effluents. AnMBR effluent leads to more fouling when compared to the AeMBR effluent with an average membrane fouling resistance of 12.35 × 1013 m−1 and 8.97 × 1013 m−1. Elemental analysis and membrane surface imaging results demonstrate that the foulant deposition sequence is organic and colloidal at first, followed by inorganic substances, while TOC and Ca are the most deposited foulants from both effluents. The unremoved ammonia in the AnMBR effluent may partially go through in the RO permeate and exceed the threshold in Singapore's PUB NEWater standard, while experiencing a significantly higher deposition rate of 13.8 % than the nitrate (0.02 %) from the AeMBR effluent. The findings suggest that the combination of AnMBR with RO offers a more sustainable approach than with the AeMBR but nutrients removal, with the potential of recovery, is recommended before the RO membranes to limit the fouling propensity and achieve a permeate of sufficient quality.

Detecting industrial discharges at an advanced water reuse facility using online instrumentation and supervised machine learning binary classification

Industries occasionally discharge slugs of concentrated pollutants to municipal sewers. These industrial discharges can cause challenges at wastewater treatment plants (WWTPs) and reuse systems. For example, elevated total organic carbon that is refractory through biological wastewater treatment increases the required ozone dose, or even exceeds the capacity of the ozone unit, resulting in a treatment pause or diversion. So, alert systems are necessary for potable reuse. Machine learning has many advantages for alert systems compared to the status quo, fixed thresholds on single variables. In this study, industrial discharges were detected using supervised machine learning and hourly data from sensors within a WWTP and downstream advanced treatment facility for aquifer recharge. Thirty-five different types of machine learning models were screened based on how well they detected an industrial discharge using default tuning parameters. Six models were selected for in-depth evaluation based in their training set accuracy, testing set accuracy, or event sensitivity: Boosted Tree, Cost-Sensitive C5.0, Oblique Random Forest with Support Vector Machines, penalized logistic regression, Random Forest Rule-Based Model, and Support Vector Machines with Radial Basis Function Kernel. After optimizing the tuning parameters and variable selection, Boosted Tree had the highest testing set accuracy, 99.2%. Over the 5-day testing set, it had zero false positives and would have detected the industrial discharge in 1 h. However, setting fixed thresholds based on the maximum normal datapoint within the training set resulted in nearly as good testing set accuracy, 98.3%. Overall, this study was a successful desktop proof-of-concept for a machine learning-based alert system for potable reuse.

Filling Source Water Protection Gaps With Enhanced Source Control for Potable Reuse

Filling Source Water Protection Gaps With Enhanced Source Control for Potable Reuse