Advanced Water Treatment Processes Research Articles

Attenuation of phenylnaphthenic acids related to oil sands process water using solar activated calcium peroxide: Influence of experimental factors, mechanistic modeling, and toxicity evaluation

Refractory naphthenic acids (NAs) are among the primary toxic compounds in oil sands process water (OSPW), a matrix with a complex chemical composition that poses challenges to its remediation. This study evaluated the effectiveness of calcium peroxide (CaO2) combined with solar radiation (solar/CaO2) as an advanced water treatment process for degrading model NAs (1,2,3,4-tetrahydronaphthalene-2-carboxylic acid, pentanoic acid, and diphenylacetic acid) in synthetic water (STW) and provide preliminary insights in treating real OSPW. Solar light and CaO2 acted synergistically to degrade target NAs in STW (>67 of synergistic factor) following a pseudo-first-order kinetic (R2 ≥ 0.95), with an optimal CaO2 dosage of 0.1 g L–1. Inorganic ions and dissolved organic matter were found to hinder the degradation of NAs by solar/CaO2 treatment; however, the complete degradation of NAs was reached in 6.7 h of treatment. The main degradation mechanism involved the generation of hydroxyl radicals (•OH), which contributed ∼90% to the apparent degradation rate constant (K), followed by H2O2 (4–5%) and 1O2 (0–5%). The tentative transformation pathways of three NAs were proposed, confirming an open-ring reaction and resulting in short-chain fatty acid ions as final products. Furthermore, a reduction in acute microbial toxicity and genotoxic effect was observed in the treated samples, suggesting that solar/CaO2 treatment exhibits high environmental compatibility. Furthermore, the solar/CaO2 system was successfully applied as a preliminary step for real-world applications to remove natural NAs, fluorophore organic compounds, and inorganic components from OSPW, demonstrating the potential use of this technology in the advanced treatment of oil-tailing-derived NAs.

Development of an Elementary Reaction-Based Kinetic Model to Predict the Aqueous-Phase Fate of Organic Compounds Induced by Reactive Free Radicals.

ConspectusAqueous-phase free radicals such as reactive oxygen, halogen, and nitrogen species play important roles in the fate of organic compounds in the aqueous-phase advanced water treatment processes and natural aquatic environments under sunlight irradiation. Predicting the fate of organic compounds in aqueous-phase advanced water treatment processes and natural aquatic environments necessitates understanding the kinetics and reaction mechanisms of initial reactions of free radicals with structurally diverse organic compounds and other reactions. Researchers developed conventional predictive models based on experimentally measured transformation products and determined reaction rate constants by fitting with the time-dependent concentration profiles of species due to difficulties in their measurements of unstable intermediates. However, the empirical treatment of lumped reaction mechanisms had a model prediction limitation with respect to the specific parent compound's fate. We use ab initio and density functional theory quantum chemical computations, numerical solutions of ordinary differential equations, and validation of the outcomes of the model with experiments. Sensitivity analysis of reaction rate constants and concentration profiles enables us to identify an important elementary reaction in formating the transformation product. Such predictive elementary reaction-based kinetics models can be used to screen organic compounds in water and predict their potentially toxic transformation products for a specific experimental investigation.Over the past decade, we determined linear free energy relationships (LFERs) that bridge the kinetic and thermochemical properties of reactive oxygen species such as hydroxyl radicals (HO•), peroxyl radicals (ROO•), and singlet oxygen (1O2); reactive halogen species such as chlorine radicals (Cl•) and bromine radicals (Br•); reactive nitrogen species (NO2•); and carbonate radicals (CO3•-). We used literature-reported experimental rate constants as kinetic information. We considered the theoretically calculated aqueous-phase free energy of activation or reaction to be a kinetic or a thermochemical property, and obtained via validated ab initio or density functional theory-based quantum chemical computations using explicit and implicit solvation models. We determined rate-determining reaction mechanisms involved in reactions by observing robust LFERs. The general accuracy of LFERs to predict aqueous-phase rate constants was within a difference of a factor of 2-5 from experimental values.We developed elementary reaction-based kinetic models and predicted the fate of acetone induced by HO• in an advanced water treatment process and methionine by photochemically produced reactive intermediates in sunlit fresh waters. We provided mechanistic insight into peroxyl radical reaction mechanisms and critical roles in the degradation of acetone and the formation of transformation products. We highlighted different roles of triplet excited states of two surrogate CDOMs, 1O2, and HO•, in methionine degradation. Predicted transformation products were compared to those obtained via benchtop experiments to validate our elementary reaction-based kinetic models. Predicting the reactivities of reactive halogen and nitrogen species implicates our understanding of the formation of potentially toxic halogen- and nitrogen-containing transformation products during water treatment processes and in natural aquatic environments.

Enhancing manganese removal through pre-deposition of powdered activated carbon-manganese oxide (PAC-MnOx) film on gravity-driven ceramic membrane: The impact of biofilm integrity and fluid dynamics

Manganese is widely distributed in the natural environment, and its presence in drinking water poses a risk to human health. In this study, an integrated pre-deposited powdered activated carbon (PAC) and manganese oxide (MnOx) bio-functional layer of inorganic origin was coupled with gravity-driven ceramic membrane (GDCM) reactor. The study aims to investigate the effects of the membrane pore size and functional layer integrity on the Mn2+ removal and flux. The results reveal that the average Mn2+ removal efficiency of the large pore size membranes (300 kDa and 0.45 μm) was lower (75 % – 78 %) compared to those with smaller pores (15 kDa and 50 kDa) (87 % – 88 %) during long-term operation. Such differences are attributed to a period of manganese leakage before the PAC-MnOx matured in large-pore membrane units and a longer residence time in small-pore membranes. The functional layer leaded to reversible fouling, which was more prominent in membranes with larger pores (contributing to 93 % of total resistance) than those with smaller ones (ranging from 51.7 % to 61.9 %). Although the damaged functional layer resulted in occasional high Mn2+ concentrations in the effluent, it did not significantly impact long-term flux development. Optical coherence tomography (OCT), in conjunction with COMSOL analysis, non-destructively evaluate biofilm formation process and indicate a homogeneous flow field and mass transfer in the “dual layers” (active film layer and ceramic membrane layer) of the GDCM. The presence of manganese-oxidizing bacteria (Hyphomicrobium, Reyranella, and Pseudomonas) in the GDCM reactor was verified using confocal laser scanning microscopy (CLSM) and high-throughput sequencing. Additional material characterization revealed that a portion of the PAC-MnOx exhibited characteristics of birnessite, with autocatalytic oxidation of Mn2+, and that Mn (III) and Mn (IV) were the primary species in MnOx, which exhibited excellent catalytic oxidation and adsorption capabilities for Mn (II), respectively. Overall, the developed PAC-MnOx GDCM system shows great promise in efficiently removing manganese and producing water of desired quality, thereby holding potential in applications across several sectors of advanced water treatment processes.

Per- and poly-fluoroalkyl substances removal in multi-barrier advanced water purification system for indirect potable reuse.

The study evaluated the removal efficacy of per- and poly-fluoroalkyl substances (PFAS) across various advanced water treatment (AWT) processes in a field-scale AWT train using secondary effluent samples from a full-scale water reclamation facility (WRF). Samples collected from April to October 2020 revealed PFCAs as the dominant PFAS compounds in the WRF secondary effluent, with PFPeA having the highest average concentration and PFSAs in notably lower amounts. Temporal fluctuations in total PFAS concentrations peaked in September 2020, which may reflect the seasonality in PFAS discharges related to applications like AFFFs and pesticides. In assessing AWT processes, coagulation-flocculation-clarification-filtration system showed no notable PFAS reduction, while ozonation resulted in elevated PFBS and PFBA concentrations. Biological activated carbon (BAC) filtration effectively removed long-chain PFAS like PFOS and PFHxS but saw increased concentrations of short-chain PFAS post-treatment. Granular activated carbon (GAC) filtration was the most effective treatment, reducing all PFSAs below the detection limits and significantly decreasing most PFCAs, though short-chain PFCAs persisted. UV treatment did not remove short-chain PFCAs such as PFBA, PFPeA, and PFHxA. The findings highlight the efficacy of AWT processes like GAC in PFAS reduction for potable reuse, but also underscore the challenge presented by short-chain PFAS, emphasizing the need for tailored treatment strategies. PRACTITIONER POINTS: Secondary effluents showed higher concentrations of PFCAs compared to PFSAs. Advanced water treatment effectively removes long-chain PFAS but not short-chain. Ozonation may contribute to formation of short-chain PFAS. BAC is less effective on short-chain PFAS, requiring further GAC treatment.

Colloid-bound radicals formed in NOM-enhanced Fe(III)/peroxymonosulfate process accelerate the degradation of trace organic contaminants in water

The omnipresence of natural organic matter (NOM) in water bodies traditionally hinders the degradation of trace organic contaminants (TrOCs) in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). This study elucidates the positive role of NOM in enhancing the degradation of TrOCs through the Fe(III)/PMS process. During this process, NOM reduces Fe(III), yielding semiquinone-like radical (NOM•) and concurrently forming NOM-Fe(III) colloids. In addition to the Fe(II)-mediated activation pathway, Fe(III) sites on NOM-Fe(III) colloids effectively transfer electrons from NOM• or some redox-active moieties to PMS, resulting in the generation of long-lived colloid-bound SO4•−, which can readily undergo hydrolysis to produce HO•. The stabilization of SO4•− and HO• by NOM-Fe(III) colloids, combined with their moderate adsorption of TrOCs, results in surface-confined reactions that significantly enhance TrOC removal, despite the presence of concurrent quenching reactions between radicals and NOM. Further, the significant positive correlation between the phenolic contents of eight NOM types and TrOC degradation kinetics suggests phenolic moieties as the primary electron source for PMS activation. By in-situ utilizing NOM in raw water, a PMS-amended iron coagulation process with 0.2 mM Fe(III) and PMS effectively removes 90–100 % of six coexisting TrOCs. This study unveils the previously unrecognized role of colloid-bound radicals in decontamination processes, offering valuable insights into harnessing NOM's influence in advanced oxidation water treatment processes.

Inactivation of antibiotic-resistant bacteria in hospital wastewater by ozone-based advanced water treatment processes

The emergence and spread of antimicrobial resistance (AMR) continue on a global scale. The impacts of wastewater on the environment and human health have been identified, and understanding the environmental impacts of hospital wastewater and exploring appropriate forms of treatment are major societal challenges. In the present research, we evaluated the efficacy of ozone (O3)-based advanced wastewater treatment systems (O3, O3/H2O2, O3/UV, and O3/UV/H2O2) for the treatment of antimicrobials, antimicrobial-resistant bacteria (AMRB), and antimicrobial resistance genes (AMRGs) in wastewater from medical facilities. Our results indicated that the O3-based advanced wastewater treatment inactivated multiple antimicrobials (>99.9%) and AMRB after 10–30 min of treatment. Additionally, AMRGs were effectively removed (1.4–6.6 log10) during hospital wastewater treatment. The inactivation and/or removal performances of these pollutants through the O3/UV and O3/UV/H2O2 treatments were significantly (P < 0.05) better than those in the O3 and O3/H2O2 treatments. Altered taxonomic diversity of microorganisms based on 16S rRNA gene sequencing following the O3-based treatment showed that advanced wastewater treatments not only removed viable bacteria but also removed genes constituting microorganisms in the wastewater. Consequently, the objective of this study was to apply advanced wastewater treatments to treat wastewater, mitigate environmental pollution, and alleviate potential threats to environmental and human health associated with AMR. Our findings will contribute to enhancing the effectiveness of advanced wastewater treatment systems through on-site application, not only in wastewater treatment plants (WWTPs) but also in medical facilities. Moreover, our results will help reduce the discharge of AMRB and AMRGs into rivers and maintain the safety of aquatic environments.

Assessing the efficiency of ozone-based advanced drinking water treatment processes in removing antibiotics and antibiotic-resistant genes: Pilot-scale research

With the widespread use of antibiotics, the emergence of antibiotics and antibiotic resistance genes (ARGs) poses a potential threat to public health. Drinking water plants are both the source and sink of these pollutants. In this study, we investigated and analyzed the distribution of four major types of antibiotics and ARGs in a drinking water plant with advanced treatment processes (ozone and activated carbon units) located in the central region of China. Among these treatment processes, the ozone process had significant removal effects on antibiotics and resistance genes, ranging from 15.10–91.17 % and 0.07–1.27 log, (except for ermA and qnrD) respectively. A correlation analysis of the concentrations of antibiotics and ARGs revealed a significant correlation (0.95 < r < 1) between antibiotics and ARGs, as well as between different types of ARGs. Additionally, the mechanism of ozone in the lab- and pilot-scale tests was analyzed to improve the removal capacity of ozone units for target pollutants. The experimental results showed that the removal efficiency of antibiotics and ARGs by ozone could be effectively improved by increasing the ozone dosage (5 mg/L), pH (9), and reaction time (10 min). The removal efficiency of the pollutants ranged between 36.65 % and 96.01 %. Under optimal reaction conditions, the results of the pilot-scale ozone experiment were significantly better than the actual treatment effects in drinking water plants. Our findings provide a theoretical basis for the optimization of the ozone process in actual drinking water plants.

Dissolved Organic Matter Fractions and Their Removal in Full-Scale Drinking Water Treatment Process

Objectives:The objective of this study is to investigate characteristics about removal of dissolved organic matter (DOM) and its fraction for improving operation efficiency in an advanced water treatment plant. Methods:The monitoring of water quality was conducted at five processes such as raw water, pre-oxidation, after sedimentation, post-ozonation, after biological activated carbon (BAC) from July 2020 to August 2021 in advanced water treatment process (AWTP) supplying 180,000m&lt;sup&gt;3&lt;/sup&gt;/day. The concentration of DOC (dissolved organic carbon) and number of algae were monitored and LC-OCD was used to fractionate DOC to four species, biopolymer (BP), humic substance (HS), building blocks (BB), and low molecular weights (LMWs). Results and Discussion:The characteristics of raw water showed that the concentration of DOC and the number of algae increased with an increase in water temperature. The portion of BP and HS significantly increased at low and high water temperature, respectively, while BB and LMWs maintained the similar portion. The removal efficiency of DOC in the AWTP was achieved at 59% with each species of BP, HS, BB, and LMWs obtaining removal efficiency of 87%, 65%, 26%, and 52%, respectively. Coagulation/sedimentation/filtration showed removal efficiency of 84%, 56%, 20%, and 18% for BP, HS, BB, and LMWs, respectively, corresponding to their molecular weight. The effect of post-ozonation would be negligible except for BP. In BAC, removal efficiency of 49% and 12% were obtained for LMWs and BB (low molecular weight, respectively. As a result, the BP portion significantly decreased due to high removal efficiency, while BB portion was increased in the final treated water compared to raw water. Conclusion:Most of DOM was removed in coagulation/sedimentation/filtration and BAC, whereas oxidation process such as pre-chlorination, pre-ozonation and post-oxidation did not have an effect on DOM removal. In coagulation/sedimentation/filtration, 84% and 54% of the BP and HS were removed, while BAC removed 49% and 12% of LMWs and BB, respectively. It has been recommended to improve the removal efficiency of BB, which obtained the lowest removal efficiency in AWTP, and to enhance the removal efficiency of LMWs in BAC to inhibit microbial regrowth in the distribution system.

Understanding the influence of dissolved organic nitrogen characteristics on enhanced coagulation performance for water reuse

With the recent focus on using advanced water treatment processes for water reuse, interest is growing for utilizing enhanced coagulation to remove dissolved chemical species. Up to 85% of the nitrogen in wastewater effluent is made up of dissolved organic nitrogen (DON), but there is a knowledge gap regarding its removal during coagulation, which can be influenced by DON characteristics. To address this issue, tertiary-treated wastewater samples were analyzed before and after coagulation with polyaluminum chloride and ferric chloride. Samples were size-fractionated into four molecular weight fractions (0.45 μm, 0.1 μm, 10 kDa, and 3 kDa) using vacuum filtration and ultrafiltration. Each fraction was further evaluated by coagulating it separately to assess DON removal during enhanced coagulation. The size fractionated samples were also separated into hydrophilic and hydrophobic fractions using C18 solid phase extraction disks. Fluorescence excitation-emission matrices were used to investigate the characteristics of dissolved organic matter contributing to DON during the coagulation process. The results showed that DON compounds of size <3 kDa constituted a majority of the total DON. Coagulation removed more than 80% DON from size fractions 0.45 μm–0.1 μm and 0.1 μm-10 kDa, but less than 20% was removed from 10 kDa to 3 kDa and <3 kDa fractions. Coagulation on pre-filtered samples removed 19% and 25% of the <3 kDa DON fraction using polyaluminum chloride and ferric chloride, respectively. In all molecular weight fractions, hydrophilic DON compounds were found to be dominant (>90%), and enhanced coagulation was not effective in removing hydrophilic DON compounds. LMW fractions respond poorly to enhanced coagulation due to their hydrophilic nature. Enhanced coagulation effectively removes humic acid-like substances, but poorly removes proteinaceous compounds such as tyrosine and tryptophan. This study's findings provide insights into DON behavior during coagulation and factors affecting its removal, potentially improving wastewater treatment strategies.

Carbon footprint analysis and carbon neutrality potential of desalination by electrodialysis for different applications

Low-carbon water production technologies are indispensable for achieving sustainable development goals and mitigating global climate change. However, at present, many advanced water treatment processes lack a systematic assessment of related greenhouse gas (GHG) emissions. Thus, quantifying their life-cycle GHG emissions and proposing strategies toward carbon neutrality is urgently needed. This case study focuses on electrodialysis (ED), an electricity-driven desalination technology. To analyze the carbon footprint of ED desalination in various applications, a life cycle assessment model was developed based on industrial-scale ED processes. For seawater desalination, the carbon footprint is 59.74 kg CO2-eq/metric ton removed salt, which is one order of magnitude lower than that of high-salinity wastewater treatment and organic solvent desalination. Meanwhile, the power consumption during operation is the main hotspot of GHG emissions. Power grid decarbonization and improved waste recycling in China are projected to reduce the carbon footprint up to 92%. Meanwhile, the contribution of operation power consumption is expected to reduce from 95.83% to 77.84% for organic solvent desalination. Through sensitivity analysis, significant non-linear impacts of process variables on the carbon footprint were determined. Therefore, it is recommended to optimize the process design and operation to reduce power consumption based on the current fossil-based grid. GHG reduction for module production and disposal should also be emphasized. This method can be extended to general water treatment or other industrial technologies for carbon footprint assessment and reducing GHG emission.

Advanced water treatment process by simultaneous coupling granular activated carbon (GAC) and powdered carbon with ultrafiltration: Role of GAC particle shape and powdered carbon type

In current ultrafiltration systems, limited removal for small-sized contaminants and membrane fouling remain longstanding obstacles to overcome. Herein, a novel process by simultaneous coupling powered carbon (PC) and fluidized granular activated carbon (GAC) with ultrafiltration was proposed aiming to achieve high effluent quality and mitigated membrane fouling. This study conducted mechanistic explorations on the performances of different-shaped GAC particles on fouling control and PC release during fluidization, meanwhile comparing the utilizations of powdered activated carbon (PAC) and biochar in terms of their adsorption, deposition and interactions with aquatic contaminants during filtration. The results showed that the effluent COD of biochar-UF was slightly higher than PAC-UF attributed to lower specific surface area and pore volume present on biochar. Compared with PAC-UF, the biochar-UF without fluidized GAC exhibited higher fouling propensity due to more organics attached on membranes via bridging with Ca2+ released by the biochar. Concurrently, distinct morphologies were found for PAC and biochar depositions, where PAC uniformly dispersed on membranes but biochar tended to agglomerate. Interestingly, fluidized spherical GAC (RGAC) with highest particle momentum and least energy consumption appeared highly effective in reducing fouling associated with biochar, and the overall fouling rate of RGAC-biochar-UF was even lower than RGAC-PAC-UF system. More importantly, substantial amount of small-sized PC was released by two cylindrical-shaped GACs, which were determined to be around 12–16 mg/L in contrast to merely 3.4 mg/L produced from RGAC. Consequently, the RGAC-biochar-UF system achieved commensurate effluent quality but better permeability than RGAC-PAC-UF along with a 20% expenditure saved, which might be a promising water treatment system more suitable for large-scale applications.

Removal and distribution of antibiotics and resistance genes in conventional and advanced drinking water treatment processes

With the extensive detection of antibiotics and antibiotic resistance genes (ARGs) in drinking water treatment plants, the safety of drinking water has received increased attention. Therefore, the distribution and removal of antibiotics and ARGs in drinking water systems require further investigation. In this study, nine typical antibiotics, nine ARGs, and one integron in two drinking water plants were investigated by high pressure liquid chromatography with tandem mass spectrometry and real-time quantitative polymerase chain reaction analyses. Sulfonamides were the dominant antibiotic in the two drinking water treatment plants (WP-A and WP-B). The removal effect of advanced water treatment on total antibiotic concentration was significantly higher than that of conventional treatment. Sul gene was the dominant gene in the raw water of the two plants. After undergoing different treatment units, the finished water in WP-A and WP-B exhibited Sul gene concentrations of 54.06 genes/mL and 67.9 genes/mL, respectively. In the conventional treatment process, adding a sand filtration unit before the flocculation unit can improve the removal efficiency of antibiotics and ARGs. In the advanced treatment process, the post ozonization unit using the strong oxidation of O3 could effectively remove antibiotics and ARGs. Although the activated carbon unit can effectively remove antibiotics, the removal effect of ARGs is poor. Chlorination has a poor effect on the removal of antibiotics, but it can effectively remove ARGs. This study can provide a basis for understanding the fate of antibiotics and ARGs in drinking water systems.

Optimization of a hybrid process combining nanofiltration and electrodialysis for the treatment of surface water in the Mekong Delta region

The coastal area of the Mekong Delta is facing a huge problem of water supply quality due to pesticide (intensive agriculture) and salinity (sea water intrusion) contamination. Their simultaneous presence makes this water complex and requires advanced water treatment processes in order to meet the Vietnamese Guideline for drinking water quality. The objective of this work is to develop an efficient surface water treatment based on electrodialysis and nanofiltration technologies. The approach consists in using electrodialysis in a first stage for salinity removal to improve, in the second stage, the performance of nanofiltration for the removal of pesticides. The question that arises is to what extent should electrodialysis desalination be carried out in order to effectively remove the pesticide and salinity in the second stage (nanofiltration) at a reasonable cost? To answer this question, an experimental design methodology was employed to describe and optimize the entire hybrid system. Experiments carried out under the optimal conditions deduced from the modeling gave experimental results in good agreement with the predictions allowing to validate the optimization approach.

Pilot-scale evaluation of forward osmosis membranes for volume reduction of industrial wastewater

Water treatment is a key aspect for the sustainable management of oil & gas operations. Osmotic concentration (OC) is an advanced water treatment process, adapted from forward osmosis (FO), that does not require water recovery from the draw solution. In this study, two commercial hollow fiber FO membranes [Module 1, cellulose triacetate (CTA) and Module 2, thin film composite (TFC)] were evaluated at pilot scale using actual process water obtained from a gas production facility. The evaluation focused on assessing the membrane productivity, fouling potential and chemical cleaning efficiency while normalizing the performance using a theoretical model that account for the variability of the operating conditions. Performance tests showed that Module 2 has a higher flux compared to Module 1, 9.9 L/m2·h vs 1.7 L/m2·h; and lower specific reverse solute flux (RSF) for most of the ions. Additionally, Module 1 benchmark experiment showed a 13% flux loss attributed to inorganic fouling (calcium phosphate precipitation) while the flux loss in Module 2 was <5% possibly due to enhanced module hydrodynamics and variation in membrane chemistry. Chemical cleaning (citric acid) proved to be successful in restoring the flux for Module 1. From the 8.1 mg/L organic carbon present in the feed, advanced organic characterization revealed that certain group of hydrophilic organics are able to pass through Module 1, but not Module 2, translating to a specific forward organic solute flux of 0.9 mg/L and 0.1 mg/L for Module 1 and 2, respectively. Finally, key sustainable and environmental considerations were presented in support of further development of process implementation. The OC process has strong potential for full-scale installation; however, demonstrating its performance in the field would be the next step necessary for successful implementation of the technology.

Inactivation of Antibiotic-Resistant Bacteria in Wastewater by Ozone-Based Advanced Water Treatment Processes.

The inactivating effect of ozone (O3)-based advanced oxidation processes (AOPs) (O3/H2O2, O3/UV, and O3/UV/H2O2 systems) on antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB) in sewage treatment plant (STP) wastewater was investigated. The AMRB were grouped into six classes: carbapenem-resistant Enterobacteriaceae (CRE), extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E), multidrug-resistant Acinetobacter (MDRA), multidrug-resistant Pseudomonas aeruginosa (MDRP), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE); these classes constituted the World Health Organization (WHO) global priority list of AMRB. The results indicate that O3-based advanced wastewater treatment inactivated all AMRB and AMSB (>99.9%) after 10 min of treatment, and significant differences (p < 0.5) were not observed in the disinfection of AMRB and AMSB by each treatment. Altered taxonomic diversity of micro-organisms based on 16S rRNA gene sequencing via O3/UV and O3/UV/H2O2 treatment showed that advanced wastewater treatments not only inactivated AMRB but also removed antimicrobial resistance genes (AMRGs) in the wastewater. Consequently, this study recommends the use of advanced wastewater treatments for treating the STP effluent, reducing environmental pollution, and alleviating the potential hazard to human health caused by AMRB, AMSB, and infectious diseases. Overall, this study provides a new method for assessing environmental risks associated with the spread of AMRB and AMSB in aquatic environments, while keeping the water environment safe and maintaining human health.

Critical Review on the Photodegradation Ability of Graphene and its Derivatives against Malachite Green, Methylene Blue, and Methyl Orange

Owing to the oxidizing, catalytic ability, and adsorbing property, graphene-based composites and their derivatives have been an ideal component for water purification and thereof. The colossal poly-aromatic π−π network and oxygen-rich groups within the functionalized graphene materials play a decisive interaction with the water pollutants viz. agricultural run-off, industrial dye effluents, and bio-medical waste via electrostatic interactions, hydrogen bonding, and photon enriched oxidations. Among various pollutant dyes, malachite green (MG), methylene blue (MB), and methyl orange (MO) have been used extensively by aqua cultural farms, tanneries, research fraternities, and textile industries due to their multifarious usage. This review unveils the cost-effective graphene preparation from various chemical synthesis processes over other conventional methods and its effectiveness in removing MG, MB, and MO with composites comprising carbonaceous materials, metal oxides, metal hybrids, and conducting organic polymers. The adsorption capacities, pseudo-1st order kinetics, degradation efficiency, and pH had been highlighted chronologically to draw a conclusive nature of graphene and its derivatives as a potential remedial against these three pollutant dyes. This article also focused on various emerging materials that had been used with functionalized graphene recently to enhance degradation efficiency and expunge multiple toxic dyes for advanced water treatment processes.

Synergistic oxidation-filtration process of electroactive peroxydisulfate with a cathodic composite CNT-PPy/PVDF ultrafiltration membrane

Ultrafiltration is an advanced water treatment process which performs poorly in the removal of small molecule organic pollutants, and is susceptible to irreversible membrane fouling. In this study, a new carbon nanotube cross-linked polypyrrole composite ultrafiltration membrane (CNT-PPy/PVDF) was fabricated, and exhibited excellent conductivity, hydrophilicity, and permeability in a novel electro-filtration activated peroxydisulfate (PDS) system (EFAP) for cathodic electrochemical activation of PDS. The EFAP showed satisfactory performance in removal of series of small molecule organic pollutants (i.e., carbamazepine, sulfamethoxazole, phenol, diclofenac.) and stable removal ratio (remaining above 90% after 20 operating cycles). Further study proved the electric field could effectively protect the cathodic CNT-PPy/PVDF membrane from oxidative damage through continual free electrons injection. Besides, the EFAP achieved up to 95% flux recovery and 80% reduction of irreversible membrane fouling (bovine serum albumin as the model foulant). Moreover, experiments confirmed that the in situ generated •OH, SO4•−, and 1O2 were the main reactive oxygen species contributing to small organics removal, while the irreversible membrane fouling mitigation was mainly due to the electrical repulsion, SO4•− and •OH, rather than 1O2. This new type of EFAP may provide a promising and sustainable approach in organic emerging contaminants control in water treatment.

AWWA Water Science Author Spotlight

Having recently published an article in AWWA Water Science, Anthony Kennedy answered questions from the publication's editor-in-chief, Kenneth L. Mercer, about the research. Stannous Chloride Reduction–Filtration for Hexavalent and Total Chromium Removal From Groundwater Anthony Kennedy, Rachel Croft, Leah Flint, and Miguel Arias-Paic At the time of the research, I worked at the United States Bureau of Reclamation (USBR). I currently work at Corona Environmental Consulting, developing a research focus related to advanced water treatment processes and process optimization. Anthony enjoys backcountry skiing in Grand Teton National Park, March 2021. I've had two great mentors so far in my career: Professor Summers at CU Boulder and Dr. Miguel Arias-Paic at USBR. Professor Summers’ best advice was to focus on what is important and to not get caught up in minutia that can degrade your confidence. Dr. Arias-Paic said that for most problems we face in water treatment, a technological solution already exists; we just need to be more creative in how we apply those technologies. The primary motivations for the research were the cost and logistical challenges associated with brine generated from ion exchange treatment. Although ion exchange brine volume from regenerations can be significantly minimized, it still contains high levels of total dissolved solids and hexavalent chromium, in addition to other metals such as arsenic, vanadium, and uranium, and must ultimately face hazardous waste disposal. With stannous chloride, rapid-sand-filter backwash waste can also contain high levels of the less toxic trivalent chromium, but without the high total dissolved solids, making it more suitable for discharge to wastewater collection systems or sludge-drying ponds. In my personal life, I'm very conscious of my consumption and environmental impact. In my research, I try to simplify technologies and processes such that they use a more sustainable material or consume fewer materials, chemicals, etc., compared with conventional technologies, with the goal of meeting the same treatment target. Three challenges are (1) actual implementation of water treatment research; (2) widespread adoption and implementation of direct potable reuse to mitigate the effects of climate change on the drinking water industry; and (3) funding for drinking water, wastewater, and water reuse infrastructure. In July 2021, Anthony visited Parco Naturale Puez Odle in South Tyrol, Italy. I grew up near Pittsburgh, which has seen a comeback due in large part to a hardworking, motivated, but also modest and humble, populace. I take the same approach with my research—just sound, thorough research that can be used to improve the design, operation, and potentially the sustainability of water treatment facilities. To learn more about Anthony's research, visit the article, available online at https://doi.org/10.1002/aws2.1174.

Removal of natural organic matter in full-scale conventional and advanced water treatment plants: Assimilable organic carbon and its precursors

This study aimed to investigate the performance of three full-scale long-time water treatment plants with influent from Taihu Lake for the removal of natural organic matter (NOM) and assimilable organic carbon (AOC), emphasizing on the processes of pre- and post-ozonation and biological activated carbon filtration (BACF). High-performance size exclusion chromatography (HPSEC) separation, hydrophilicity/hydrophobicity resin fractionation and excitation-emission matrix (EEM) fluorescence spectroscopy were applied to determine NOM fraction variation in purification processes and their relationships with AOC. The results indicated that NOM fractions with high hydrophilicity (NHPI) and lower molecular weight (1 kDa - 10 kDa) likely contributed to the majority of AOC. The advanced water treatment processes behaved negative removals of AOC since the BACF with long-time operation introduced large amounts of AOC precursors and could cause drastic rebound of AOC upon chlorination disinfection. Finally, during exposure to ozone, the formation rate of AOC showed a linear relationship with UV254 and total fluorescence intensity (TFI) and each regional fluorescence intensity (RFI) with slight interference by the presence of particulate organic matter (POM). This study provides useful information for variation of NOM and its associated bio-availability during conventional and advanced processes in full-scale water treatment plants.

Removal Behavior of Protein-like Dissolved Organic Matter During Different Water Treatment Processes in Full-Scale Drinking Water Treatment Plants

Protein-like dissolved organic matter (pDOM), which is ubiquitous in natural waters, is a critical precursor of nitrogenous disinfection byproducts. Recently, the control and elimination of pDOM have been a growing concern during drinking water treatment processes. In this study, a high-performance size exclusion chromatography system coupled with photo-diode array, fluorescence detector, and online organic carbon detector (HPSEC-PDA/FLD/OCD) was used to determine the removal behaviors of different-sized pDOM from two full-scale drinking water treatment plants (DWTPs). Coagulation and activated carbon adsorption were selected for bench-scale experiments to further assess the removal behavior of pDOM during conventional water treatment processes. The results showed that different-sized pDOM fractions exhibited different removal characteristics. Pre-oxidation can effectively remove some tyrosine-like and tryptophan-like components with high MW, and as the oxidization effect was enhanced, more high MW fractions decomposed into low MW ones. Conversely, some aliphatic pDOM fractions in high MW (e.g., aliphatic proteins) were not subject to pre-oxidation removal. The coagulation-sedimentation unit was efficient in removing high MW fractions, specifically tryptophan-like fractions. Additionally, some pDOM components may be released during coagulation. pDOM with low MW and high hydrophobicity were easily removed during activated carbon filtration. However, long-term operation of the activated carbon filter may breed microorganisms, resulting in the partial release of pDOM fractions. Moreover, UV disinfection processes promoted the degradation of low MW pDOM components. Due to the complex water quality and uncontrollable microbial activities, the aforementioned water treatment units did not exhibit a synergistic effect on pDOM removal. In comparison with humic-like substances, pDOM was susceptible to water quality changes, and its removal was limited in the surveyed DWTPs. Therefore, DWTPs must strengthen pDOM monitoring in influent and effluent and adjust the operating parameters of different treatment units in a timely manner. Moreover, the combination of advanced water treatment processes, such as ozone-biological activated carbon process and nanofiltration, should also be considered to strictly control pDOM component removal.