Ozone dose dependent formation and removal of ozonation products of pharmaceuticals in pilot and full-scale municipal wastewater treatment plants

Ozonation using a stainless-steel membrane contactor: Gas-liquid mass transfer and pharmaceuticals removal from secondary-treated municipal wastewater

A tubular porous stainless steel membrane contactor was characterized in terms of ozone-water mass transport, as well as its application in removing 23 pharmaceuticals (PhACs) detected in the secondary-treated municipal wastewater, under continuous mode operation. The volumetric mass transfer coefficient (KLa) was evaluated based on liquid flow rate, gas flow rate, and ozone gas concentration. The KLa values were substantially improved with an increment in liquid flow rate (1.6 times from 30 to 70 dm3 h-1) and gas flow rate (3.6 times from 0.30 to 0.85 Ndm3 min-1) due to the improved mixing in the gas-liquid interface. For the lowest liquid flow rate (30 dm3 h-1), the water phase boundary layer (82%) exhibited the major ozone transfer resistance, but it became almost comparable with membrane resistance for the highest liquid flow rate (70 dm3 h-1). Additionally, the influence of the specific ozone dose (0.39, 0.53, and 0.69 g O3 g DOC-1) and ozone inlet gas concentration ( [Formula: see text]  = 27, 80, and 134 g Nm-3) were investigated in the elimination of 23 PhACs found in secondary-treated municipal wastewater. An ozone dose of 0.69 g O3 g DOC-1 and residence time of 60 s resulted in the removal of 12 out of the 23 compounds over 80%, while 17 compounds were abated above 60%. The elimination of PhACs was strongly correlated with kinetic reaction constants values with ozone and hydroxyl radicals (kO3 and kHO•), leading to a characteristic elimination pattern for each group of contaminants. This study demonstrates the high potential of membrane contactors as an appealing alternative for ozone-driven wastewater treatment.

Ecotoxicological mixture risk assessment of 35 pharmaceuticals in wastewater effluents following post-treatment with ozone and/or granulated activated carbon

Reducing the risk posed by mixtures of pharmaceuticals is a goal of current initiatives such as the European Green Deal to reduce anthropological environmental impacts. Wastewater effluent typically contains large numbers of active pharmaceutical ingredients (APIs). For some APIs, existing technology such as conventional activated sludge (CAS) wastewater treatment plants (WWTPs) have removal rates below 20 %, thus the WWTP discharges are adding to the toxic burden of receiving waters. We present an environmental risk assessment of mixtures of 35 APIs in effluent samples from 82 Northern European WWTPs using the concentration addition model, and identify the respective risk-driving APIs. This is then compared to a corresponding mixture risk assessment of effluent samples from the Danish Hillerød WWTP subjected to post-treatment with varying specific ozone doses (0.15-1.05 mgO3/mgDOC) and/or granulated activated carbon (GAC). All 82 WWTP effluent samples exceeded risk thresholds by at least a factor of 30, with a median RQSUM of 92.9, highlighting the need for effluent post-treatment and/or a substantial dilution in the recipient waters. Antibiotics, analgesics and anti-depressants were among the top risk drivers with 99 % of the average mixture risk attributable to azithromycin, diclofenac, venlafaxine, clarithromycin and mycophenolic acid. Effluent mixture risk was reduced by ozonation in a concentration-dependent manner, decreasing below threshold levels to a median RQSUM of 0.83 following treatment with 0.65 mgO3/mg DOC. Fresh GAC was also effective at reducing the mixture risk both alone and with ozone treatment, with median RQSUM of 0.04 and 0.07 respectively. To our knowledge, this is the first study to present a risk assessment of pharmaceutical mixtures in effluent comparing "conventional" WWTP processes with additional post-treatment with ozone and/or GAC for reducing the joint risks of pharmaceutical mixtures for recipient waters. We demonstrate the need for additional WWTP treatment technologies, and the efficacy of GAC and ozonation in decreasing the risk to the aquatic environment from pharmaceutical mixtures to below acceptable threshold limits.

Removal of micropollutants and ecotoxicity during combined biological activated carbon and ozone (BO3) treatment

Ozonation is a viable option to improve the removal of micropollutants (MPs) in wastewater treatment plants (WWTPs). Nevertheless, the application of ozonation is hindered by its high energy requirements and by the uncertainties regarding the formation of toxic transformation products in the process. Energy requirements of ozonation can be reduced with a pre-ozone treatment, such as a biological activated carbon (BAC) filter, that removes part of the effluent organic matter before ozonation. This study investigated a combination of BAC filtration followed by ozonation (the BO3 process) to remove MPs at low ozone doses and low energy input, and focused on the formation of toxic organic and inorganic products during ozonation. Effluent from a WWTP was collected, spiked with MPs (approximately 1 µg/L) and treated with the BO3 process. Different flowrates (0.25-4 L/h) and specific ozone doses (0.2-0.6 g O3/g TOC) were tested and MPs, ecotoxicity and bromate were analyzed. For ecotoxicity assessment, three in vivo (daphnia, algae and bacteria) and six in vitro CALUX assays (Era, GR, PAH, P53, PR, andNrf2 CALUX) were used. Results show that the combination of BAC filtration and ozonation has higher MP removal and higher ecotoxicity removal than only BAC filtration and only ozonation. The in vivo assays show a low ecotoxicity in the initial WWTP effluent samples and no clear trend with increasing ozone doses, while most of the in vitro assays show a decrease in ecotoxicity with increasing ozone dose. This suggests that for the tested bioassays, feed water and ozone doses, the overall ecotoxicity of the formed transformation products during ozonation was lower than the overall ecotoxicity of the parent compounds. In the experiments with bromide spiking, relevant formation of bromate was observed above specific ozone doses of approximately 0.4 O3/g TOC and more bromate was formed for the samples with BAC pre-treatment. This indirectly indicates the effectivity of the pre-treatment in removing organic matter and making ozone more available to react with other compounds (such as MPs, but also bromide), but also underlines the importance of controlling the ozone dose to be below the threshold to avoid formation of bromate. It was concluded that treatment of the tested WWTP effluent in the BO3 process at a specific ozone dose of 0.2 g O3/g TOC, results in high MP removal at limited energy input while no increase in ecotoxicity, nor formation of bromate was observed under this condition. This indicates that the hybrid BO3 process can be implemented to remove MPs and improve the ecological quality of this WWTP effluent with a lower energy demand than conventional MP removal processes such as standalone ozonation.

Guidance document on the impact of water treatment processes on residues of active substances or their metabolites in water abstracted for the production of drinking water

This guidance document provides a tiered framework for risk assessors and facilitates risk managers in making decisions concerning the approval of active substances (AS) that are chemicals in plant protection products (PPPs) and biocidal products, and authorisation of the products. Based on the approaches presented in this document, a conclusion can be drawn on the impact of water treatment processes on residues of the AS or its metabolites in surface water and/or groundwater abstracted for the production of drinking water, i.e. the formation of transformation products (TPs). This guidance enables the identification of actual public health concerns from exposure to harmful compounds generated during the processing of water for the production of drinking water, and it focuses on water treatment methods commonly used in the European Union (EU). The tiered framework determines whether residues from PPP use or residues from biocidal product use can be present in water at water abstraction locations. Approaches, including experimental methods, are described that can be used to assess whether harmful TPs may form during water treatment and, if so, how to assess the impact of exposure to these water treatment TPs (tTPs) and other residues including environmental TPs (eTPs) on human and domesticated animal health through the consumption of TPs via drinking water. The types of studies or information that would be required are described while avoiding vertebrate testing as much as possible. The framework integrates the use of weight-of-evidence and, when possible alternative (new approach) methods to avoid as far as possible the need for additional testing.

Performance of a Pilot-Scale Continuous Flow Ozone-Based Hospital Wastewater Treatment System

Antimicrobial resistance (AMR) is becoming a global concern. Recently, research has emerged to evaluate the human and environmental health implications of wastewater from medical facilities and to identify acceptable wastewater treatment methods. In this study, a disinfection wastewater treatment system using an ozone-based continuous flow system was installed in a general hospital located in Japan. The effectiveness of antimicrobial-resistant bacteria (ARB) and antimicrobials in mitigating the environmental impact of hospital wastewater was evaluated. Metagenomic analysis was conducted to characterize the microorganisms in the wastewater before and after treatment. The results demonstrated that ozone treatment enables effective inactivation of general gut bacteria, including Bacteroides, Prevotella, Escherichia coli, Klebsiella, DNA molecules, and ARGs, as well as antimicrobials. Azithromycin and doxycycline removal rates were >99% immediately after treatment, and levofloxacin and vancomycin removal rates remained between 90% and 97% for approximately one month. Clarithromycin was more readily removed than the other antimicrobials (81-91%), and no clear removal trend was observed for ampicillin. Our findings provide a better understanding of the environmental management of hospital wastewater and enhance the effectiveness of disinfection wastewater treatment systems at medical facilities for mitigating the discharge of pollutants into aquatic environments.

Retrospective on Exploring MXene-Based Nanomaterials: Photocatalytic Applications

Nanostructural two-dimensional compounds are grabbing the attention of researchers all around the world. This research is progressing quickly due to its wide range of applications in numerous industries and enormous promise for future technological breakthroughs. Growing environmental consciousness has made it vital to treat wastewater and avoid releasing hazardous substances into the environment. Rising consumer expectations have led to the emergence of new, frequently nonbiodegradable compounds. Due to their specific chemical and physical properties, MXenes have recently been identified as promising candidates. MXenes are regarded as a prospective route for environmental remediation technologies, such as photocatalysis, adsorption, and membrane separation, and as electrocatalytic sensors for pollution recognition because of their high hydrophilicity, inherent chemical nature, and robust electrochemistry. The development of catalysts based on MXene materials for the photocatalytic breakdown of pharmaceutical wastes in polluted water is critically evaluated in this study. With an emphasis on the degradation mechanism, the photocatalytic degradation of antibiotics using MXenes and MXene-based nanocomposites is explained in depth. We emphasize the significant difficulties in producing MXenes and their composites, as well as in the degradation of drugs. The successful use of MXenes in water filtration and suggestions for future study are also presented.

Stable isotope labeling for detection of ozonation byproducts in effluent organic matter with FT-ICR-MS

Despite effluent organic matter (EfOM) being a major consumer of ozone during wastewater treatment, little is known about ozonation byproducts (OBPs) produced from EfOM. To unambiguously identify OBPs, heavy ozone was used to ozonate EfOM, resulting in ¹⁸O labeled and unlabeled OBPs. Labeled OBPs mostly represent a single ¹⁸O transfer and were classified as either direct or indirect OBPs based on the ¹⁸O/¹⁶O intensity ratios of the isotopologues. Of the 929 labeled OBPs, 84 were unequivocally classified as direct OBPs. The remainder suggest a major contribution by indirect, hydroxyl radical induced formation of OBPs in EfOM. Overall, labelled OBPs possess a low degree of unsaturation and contributed most to OBP peak intensity - marking them as potential end products. A few direct and indirect OBPs with high peak intensity containing ¹⁸O and heteroatoms (N, S) were fragmented with CID FT-ICR-MS/MS and screened for indicative neutral losses carrying heavy oxygen. The neutral loss screening was used to detect the ¹⁸O location on the OBP and indicate the original functional group in EfOM based on known reaction mechanisms. We identified sulfoxide and sulfonic acid functional groups in selected OBPs - implying the presence of reduced sulfur in EfOM molecules - while no evidence for nitrogen containing functional groups reacting with ozone was found.

Further transformation of the primary ozonation products of tramadol- and venlafaxine N-oxide: Mechanistic and structural considerations

Ozonation has been used to effectively remove micropollutants from the secondary effluent in several wastewater treatment plants. It is known that ozonation transforms tertiary amine compounds into their respective N-oxides, however in an earlier study a mass balance could not be closed at elevated ozone concentrations, leading to the assumption that more ozonation products are possible. This study was conducted to elucidate which (hitherto unknown) ozonation products can be formed from venlafaxine and tramadol when ozonating wastewater. Ozonation experiments were performed with tramadol and venlafaxine N-oxide in two different set-ups. Both tramadol- and venlafaxine N-oxide degraded during ozonation in pure (deionized) water in both semi-continuous and batch mode ozonation set-ups. 13 and 17 new transformation products were detected from tramadol- and venlafaxine N-oxide respectively, using high resolution mass spectrometry with ESI(+) ionization. Empirical chemical formulas were proposed based on the determination of the exact masses and interpretation of the product ion spectra. These transformation products result from the addition of one to three oxygen atoms and removal of C, -CH₂, C₂H₂, C₃H₆, etc., from the parent molecule, respectively. Quenching experiments suggested that most of the transformation products originated from the direct reaction with ozone (eight for tramadol N-oxide and ten for venlafaxine N-oxide), whereas fewer products originated from the reaction with OH radicals (three for tramadol N-oxide and three for venlafaxine N-oxide). Reaction mechanisms and chemical structures of products are proposed, based on the available active sites and past literature on ozone reaction mechanisms. The experimental results are compared to theory and literature on ozone reactive sites and ozone reaction mechanisms. All in all this shows that there can be multiple ozonation products, and ozonation pathways can be complex, even if initially only one ozonation product is formed.

Inactivation of Bacteria and Residual Antimicrobials in Hospital Wastewater by Ozone Treatment

The emergence and spread of antimicrobial resistance (AMR) has become a persistent problem globally. In this study, an ozone treatment facility was established for an advanced hospital wastewater treatment in a core hospital facility in an urban area in Japan to evaluate the inactivation of antimicrobial-resistant bacteria and antimicrobials. Metagenomic DNA-seq analysis and the isolation of potential extended-spectrum β-lactamase (ESBL)-producing bacteria suggested that ozone exposure for at least 20 min is required for the adequate inactivation of DNA and ESBL-producing bacteria. Escherichia coli and Klebsiella species were markedly susceptible to 20-min ozone exposure, whereas Raoultella ornithinolytica and Pseudomonas putida were isolated even after an 80-min exposure. These ozone-resistant bacteria might play a pivotal role as AMR reservoirs in the environment. Nine antimicrobials (ampicillin, cefdinir, cefpodoxime, ciprofloxacin, levofloxacin, clarithromycin, chlortetracycline, minocycline, and vancomycin) were detected at 373 ng/L to 27 μg/L in the hospital wastewater, and these were removed (96–100% removal) after a 40-min treatment. These results facilitate a comprehensive understanding of the AMR risk posed by hospital wastewater and provides insights for devising strategies to eliminate or mitigate the burden of antimicrobial-resistant bacteria and the flow of antimicrobials into the environment. To the best of our knowledge, this is the first report on the implementation of a batch-type, plant-scale ozone treatment system in a hospital facility to execute and evaluate the inactivation of drug-resistant bacteria and antimicrobials.

Treatability of hazardous substances in industrial wastewater: case studies for textile manufacturing and leather production sectors

Hazardous substances used and produced by different industrial activities pose a potential risk to the environment and to human health. Different physicochemical and/or biological processes are used in industrial wastewater treatment; these methods, however, may not be effective in removing these substances. This study was carried out to comparatively evaluate the removal of hazardous substances through conventional wastewater treatment processes that are used by major industries in Turkey. A four-season monitoring study was carried out in textile manufacturing and leather production sectors, representing industrial activities in Turkey. Samples were analyzed for 45 priority substances defined by the European Union and 250 specific pollutants listed in the Turkish Regulation on Surface Water Quality. For both wastewaters, where biological treatment was performed after pretreatment, their characteristics showed that organics were almost completely removed. except for dichloromethane (44-51% removals) and dioxin and dioxin-like compounds (64-69% removals). Additionally, different removal ratios (16-97%) were obtained for metals; the poorer removal was observed for B, Ba, Ag, Sb, and Si. The remaining metals (Cu, Pb, Sb, V, Si for textile; Cr, Cu, Sb, Si for leather effluents) in the treated wastewaters were still higher than environmental quality standards (EQS) of receiving water bodies. The study revealed that existing treatment processes were not adequate for efficient hazardous substance removal and there is an urgent need to improve them. Finally, advanced treatment technologies were suggested for specific pollutants together with their unit treatment costs.

Evaluation of the Correspondence between the Concentration of Antimicrobials Entering Sewage Treatment Plant Influent and the Predicted Concentration of Antimicrobials Using Annual Sales, Shipping, and Prescriptions Data

The accuracy and correspondence between the measured concentrations from the survey and predicted concentrations on the basis of the three types of statistical antimicrobial use in Japan was evaluated. A monitoring survey of ten representative antimicrobials: ampicillin (APL), cefdinir (CDN), cefpodoxime proxetil (CPXP), ciprofloxacin (CFX), clarithromycin (CTM), doxycycline (DCL), levofloxacin (LFX), minocycline (MCL), tetracycline (TCL), and vancomycin (VMC), in the influent of sewage treatment plant (STP) located in urban areas of Japan, was conducted. Then, the measured values were verified in comparison with the predicted values estimated from the shipping volumes, sales volumes, and prescription volumes based on the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). The results indicate that the correspondence ratios between the predicted concentrations calculated on the basis of shipping and NDB volumes and the measured concentrations (predicted concentration/measured concentration) generally agreed for the detected concentration of antimicrobials in the STP influent. The correspondence ratio on the basis of shipping volume was, for CFX, 0.1; CTM, 2.9; LFX, 0.5; MCL, 1.9; and VMC, 1.7, and on the basis of NDB volume the measured concentration was CFX, 0.1; CTM, 3.7; DCL, 0.4; LFX, 0.7; MCL, 1.9; TCL, 0.6; and VMC, 1.6. To our knowledge, this is the first report to evaluate the accuracy of predicted concentrations based on sales, shipping, NDB statistics and measured concentrations for antimicrobials in the STP influent.

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.

Overgrowth control of potentially hazardous bacteria during storage of ozone treated wastewater through natural competition

Improving the chemical and biological quality of treated wastewater is particularly important in world regions under water stress. In these regions, reutilization of wastewater is seen as an alternative to reduce water demand, particularly for agriculture irrigation. In a reuse scenario, the treated wastewater must have enough quality to avoid chemical and biological contamination of the receiving environment. Ozonation is among the technologies available to efficiently remove organic micropollutants and disinfect secondary effluents, being implemented in full-scale urban wastewater treatment plants worldwide. However, previous studies demonstrated that storage of ozone treated wastewater promoted the overgrowth of potentially harmful bacteria, putting at risk its reutilization, given for instance the possibility of contaminating the food-chain. Therefore, this study was designed to assess the potential beneficial role of inoculation of ozone treated wastewater with a diverse bacterial community during storage, for the control of the overgrowth of potentially hazardous bacteria, through bacterial competition. To achieve this goal, ozone treated wastewater (TWW) was diluted with river water (RW) in the same proportion, and the resulting bacterial community (RW+TWW) was compared to that of undiluted TWW over 7 days storage. As hypothesized, in contrast to TWW, where dominance of Beta- and Gammaproteobacteria, namely Pseudomonas spp. and Acinetobacter spp., was observed upon storage for 7 days, the bacterial communities of the diluted samples (RW+TWW) were diverse, resembling those of RW. Moreover, given the high abundance of antibiotic resistance genes in RW, the concentration of these genes in RW+TWW did not differ from that of the non-ozonated controls (WW, RW and RW+WW) over the storage period. These results highlight the necessity of finding a suitable pristine diverse bacterial community to be used in the future to compete with bacteria surviving ozonation, to prevent reactivation of undesirable bacteria during storage of treated wastewater.

Two-Dimensional Nanomaterials for the Removal of Pharmaceuticals from Wastewater: A Critical Review

The removal of pharmaceuticals from wastewater is critical due to their considerable risk on ecosystems and human health. Additionally, they are resistant to conventional chemical and biological remediation methods. Two-dimensional nanomaterials are a promising approach to face this challenge due to their combination of high surface areas, high electrical conductivities, and partially optical transparency. This review discusses the state-of-the-art concerning their use as adsorbents, oxidation catalysts or photocatalysts, and electrochemical catalysts for water treatment purposes. The bibliographic search bases upon academic databases including articles published until August 2021. Regarding adsorption, high removal capacities (>200 mg g−1) and short equilibrium times (<30 min) are reported for molybdenum disulfide, metal-organic frameworks, MXenes, and graphene oxide/magnetite nanocomposites, attributed to a strong adsorbate-adsorbent chemical interaction. Concerning photocatalysis, MXenes and carbon nitride heterostructures show enhanced charge carriers separation, favoring the generation of reactive oxygen species to degrade most pharmaceuticals. Peroxymonosulfate activation via pure or photo-assisted catalytic oxidation is promising to completely degrade many compounds in less than 30 min. Future work should be focused on the exploration of greener synthesis methods, regeneration, and recycling at the end-of-life of two-dimensional materials towards their successful large-scale production and application.

A Review on Emerging Pollutants in the Water Environment: Existences, Health Effects and Treatment Processes

Emerging pollutants (EPs), also known as micropollutants, have been a major issue for the global population in recent years as a result of the potential threats they bring to the environment and human health. Pharmaceuticals and personal care products (PPCPs), antibiotics, and hormones that are used in great demand for health and cosmetic purposes have rapidly culminated in the emergence of environmental pollutants. EPs impact the environment in a variety of ways. EPs originate from animal or human sources, either directly discharged into waterbodies or slowly leached via soils. As a result, water quality will deteriorate, drinking water sources will be contaminated, and health issues will arise. Since drinking water treatment plants rely on water resources, the prevalence of this contamination in aquatic environments, particularly surface water, is a severe problem. The review looks into several related issues on EPs in water environment, including methods in removing EPs. Despite its benefits and downsides, the EPs treatment processes comprise several approaches such as physico-chemical, biological, and advanced oxidation processes. Nonetheless, one of the membrane-based filtration methods, ultrafiltration, is considered as one of the technologies that promises the best micropollutant removal in water. With interesting properties including a moderate operating manner and great selectivity, this treatment approach is more popular than conventional ones. This study presents a comprehensive summary of EP’s existence in the environment, its toxicological consequences on health, and potential removal and treatment strategies.

Removal of Micropollutants by Ozone-Based Processes

Micropollutants and emerging substances pose a serious problem to environmental sustainability and remediation, due to their widespread use and applications in everyday life. This group of chemicals is diverse but with common toxic and harmful properties. Their concentration in the environment is often very low; however, due to their recalcitrant nature, they are persistent in air, water, and soil. From an engineering point of view, the challenge is not straightforward. It is difficult to remove these contaminants from complex mixtures of substances by conventional methods used in wastewater and drinking water treatment. Ozonation and ozone-based AOPs are accepted processes of degradation of resistant substances or at least enhancement of their biodegradability. The aim of this review paper is to present research trends aimed at solving problems in the research and application of ozone-based processes in the removal of micropollutants from wastewater, thus preventing leakage of harmful substances into surface water, soil, and groundwater and facilitating the reuse of wastewater. Priority substances, micropollutants and emerging pollutants, as well as processes and technologies for their transformation and elimination, are briefly specified. Results obtained by the authors in solving research projects that were aimed at eliminating selected micropollutants by ozonation and ozone-based AOPs are also presented. This review focuses on selected alkylphenols, petroleum substances, and organochlorine pesticides.

Degradation and mineralization of the emerging pharmaceutical pollutant sildenafil by ozone and UV radiation using response surface methodology

Pharmaceuticals and their degradation products which are present in wastewater and superficial waters are becoming an ecological issue. This research investigated the degradation and mineralization of synthetic solutions of the pharmaceutical compound sildenafil citrate (SC) by single ozonation and ozonation jointed with UV radiation (O₃/UV). The effects of initial drug concentration (50-125 mg L^-1), inlet ozone concentration (35-125 g Nm^-3), and UV radiation on SC degradation and decrease of total organic carbon (TOC) were investigated using response surface methodology based on a central composite experimental design. Through the RSM analysis, it was possible to confirm the removal of SC for the entire experimental range. Major intermediates of SC degradation were identified and a degradation pathway was proposed. The kinetics of SC degradation was modeled as a pseudo-first-order reaction with a rate constant ranging between 0.072 and 1.250 min^-1. The SC degradation and TOC removal were strongly enhanced by increasing the concentration of gaseous ozone at the inlet and incorporating UV radiation. The highest TOC removal reached at 60 min was 75%, in the O₃/UV system, with initial SC content of 50 mg L^-1 and inlet ozone concentration of 125 g Nm^-3. The degradation rate of SC was increased 3 to 9 times in the presence of UV radiation. Ozone-based advanced oxidation processes appear as a suitable alternative for treatment of the emerging pollutant SC.

Predictive water virology using regularized regression analyses for projecting virus inactivation efficiency in ozone disinfection

Wastewater reclamation and reuse have been practically applied to water-stressed regions, but waterborne pathogens remaining in insufficiently treated wastewater are of concern. Sanitation Safety Planning adopts the hazard analysis and critical control point (HACCP) approach to manage human health risks upon exposure to reclaimed wastewater. HACCP requires a predetermined reference value (critical limit: CL) at critical control points (CCPs), in which specific parameters are monitored and recorded in real time. A disinfection reactor of a wastewater treatment plant (WWTP) is regarded as a CCP, and one of the CCP parameters is the disinfection intensity (e.g., initial disinfectant concentration and contact time), which is proportional to the log reduction value (LRV) of waterborne pathogens. However, the achievable LRVs are not always stable because the disinfection intensity is affected by water quality parameters, which vary among WWTPs. In this study, we established models for projecting virus LRVs using ozone, in which water quality and operational parameters were used as explanatory variables. For the model construction, we used five machine learning algorithms and found that automatic relevance determination with interaction terms resulted in better prediction performances for norovirus and rotavirus LRVs. Poliovirus and coxsackievirus LRVs were predicted well by a Bayesian ridge with interaction terms and lasso with quadratic terms, respectively. The established models were relatively robust to predict LRV using new datasets that were out of the range of the training data used here, but it is important to collect LRV datasets further to make the models more predictable and flexible for newly obtained datasets. The modeling framework proposed here can help WWTP operators and risk assessors determine the appropriate CL to protect human health in wastewater reclamation and reuse.

A review of the characteristics of Fenton and ozonation systems in landfill leachate treatment

The development and application of Fenton and ozonation systems in landfill leachate treatment over the last 20 years, and the current research status are reviewed in this paper, with an emphasis on the technical and economic characteristics of Fenton and ozonation systems used to treat different types of landfill leachate. To date, a total of 101 and 78 articles have been published regarding leachate treatment by Fenton and ozonation systems, respectively. These articles considered the use of two systems to treat aged leachate, biologically treated leachate and leachate comprising the concentrated solution resulting from reverse osmosis (RO). The oxidization mechanisms of the two systems used to treat landfill leachate significantly differed in terms of their optimal process parameters (e.g., initial pH value, reagent dosage, and reaction time) and removal efficiency. The Fenton and ozonation systems outperformed persulfate-based advanced oxidation technology in terms of their improved biodegradability of landfill leachate and engineering practicability. The cost of the reagents required to treat landfill leachate by Fenton and ozonation systems accounted for at least 85% of the total operating cost. In contrast to the ozonation system, the Fenton system was more cost-effective when both systems were used to treat the same type of landfill leachate. This study provides a theoretical basis for the operation of Fenton and ozonation systems and also offers technical support for landfill leachate disposal companies that opt to use these technologies.

MBBRs as post-treatment to ozonation: Degradation of transformation products and ozone-resistant micropollutants

The degradation potential of micropollutants and transformation products in biological post-treatment after ozonation is partly unknown. A pilot plant with ozonation and subsequent biological treatment in a moving bed biofilm reactor (MBBR) was thus operated over 16 months to investigate the removal of micropollutants and the formation and removal of N-oxide transformation products. Lab-scale kinetic experiments were performed in parallel. At a moderate ozone dose of 0.5 g O₃ g^-1 DOC, further degradation of gabapentin and 3 iodinated contrast media (iomeprol, iopamidol, and iohexol) could be induced by the biofilm at prolonged exposure times. To facilitate comparison of feeding regimens in biofilm systems a new surface-related degradation rate constant was introduced. The availability of substrates in the pilot MBBR influenced the micropollutant degradation kinetics with increasing and decreasing degradation rates. N-oxides from erythromycin, clarithromycin, tramadol, and venlafaxine were formed during ozonation and could not be degraded by the biofilm.

Elucidating the impacts of intermittent in-situ ozonation in a ceramic membrane bioreactor: Micropollutant removal, microbial community evolution and fouling mechanisms

In this study, impacts of in-situ ozonation applied directly in the membrane tank of a ceramic MBR (Oz-MBR) were assessed to elucidate its implications on micropollutant removal, microbial taxa and membrane fouling. The basic effluent quality (i.e., bulk organics and nutrients) of the MBR without and with in-situ ozonation was comparable. Importantly, pollutant-specific (10-26%) improvement in micropollutant removal was achieved by the Oz-MBR, which could be attributed to the increase in the abundance of microbial taxa responsible for the removal of structurally complex pollutants and/or ozone-assisted oxidation. In-situ ozonation affected the abundance of denitrifying bacteria and functional genes but total nitrogen removal by the Oz-MBR was comparable to that achieved by the control (C)-MBR. Improved mixed liquor properties, and the reduced accumulation of foulants on the membrane surface resulted in membrane fouling alleviation (53%) in the Oz-MBR. In addition, fouling models evaluated for the first time in the case of Oz-MBR indicated that the cake-complete model was suitable to explain membrane fouling mechanism. This comprehensive study demonstrates the performance of MBR coupled with in-situ ozonation, and the obtained results would serve as a useful reference for its implementation at pilot- and/or full-scale.