Predicting trace organic compound attenuation by ozone oxidation: Development of indicator and surrogate models

Ferrate(VI) assists in reducing cytotoxicity and genotoxicity to mammalian cells and organic bromine formation in ozonated wastewater

Ozonation of wastewater containing bromide (Br-) forms highly toxic organic bromine. The effectiveness of ozonation in mitigating wastewater toxicity is minimal. Simultaneous application of ozone (O3) (5 mg/L) and ferrate(VI) (Fe(VI)) (10 mg-Fe/L) reduced cytotoxicity and genotoxicity towards mammalian cells by 39.8% and 71.1% (pH 7.0), respectively, when the wastewater has low levels of Br-. This enhanced reduction in toxicity can be attributed to increased production of reactive iron species Fe(IV)/Fe(V) and reactive oxygen species (•OH) that possess higher oxidizing ability. When wastewater contains 2 mg/L Br-, ozonation increased cytotoxicity and genotoxicity by 168%-180% and 150%-155%, respectively, primarily due to the formation of organic bromine. However, O3/Fe(VI) significantly (p < 0.05) suppressed both total organic bromine (TOBr), BrO3-, as well as their associated toxicity. Electron donating capacity (EDC) measurement and precursor inference using Orbitrap ultra-high resolution mass spectrometry found that Fe(IV)/Fe(V) and •OH enhanced EDC removal from precursors present in wastewater, inhibiting electrophilic substitution and electrophilic addition reactions that lead to organic bromine formation. Additionally, HOBr quenched by self-decomposition-produced H2O2 from Fe(VI) also inhibits TOBr formation along with its associated toxicity. The adsorption of Fe(III) flocs resulting from Fe(VI) decomposition contributes only minimally to reducing toxicity. Compared to ozonation alone, integration of Fe(VI) with O3 offers improved safety for treating wastewater with varying concentrations of Br-.

Dynamic Modelling, Process Control, and Monitoring of Selected Biological and Advanced Oxidation Processes for Wastewater Treatment: A Review of Recent Developments

This review emphasizes the significance of formulating control strategies for biological and advanced oxidation process (AOP)-based wastewater treatment systems. The aim is to guarantee that the effluent quality continuously aligns with environmental regulations while operating costs are minimized. It highlights the significance of understanding the dynamic behaviour of the process in developing effective control schemes. The most common process control strategies in wastewater treatment plants (WWTPs) are explained and listed. It is emphasized that the proper control scheme should be selected based on the process dynamic behaviour and control goal. This study further discusses the challenges associated with the control of wastewater treatment processes, including inadequacies in developed models, the limitations of most control strategies to the simulation stage, the imperative requirement for real-time data, and the financial and technical intricacies associated with implementing advanced controller hardware. It is discussed that the necessity of the availability of real-time data to achieve reliable control can be achieved by implementing proper, accurate hardware sensors in suitable locations of the process or by developing and implementing soft sensors. This study recommends further investigation on available actuators and the criteria for choosing the most appropriate one to achieve robust and reliable control in WWTPs, especially for biological and AOP-based treatment approaches.

Atomically dispersed copper sites on titanium zirconium oxide accelerate the simultaneous oxidative removal of organic carbon and ammonia from landfill leachate

Landfill leachate is a refractory wastewater. Low-temperature catalytic air oxidation (LTCAO) has shown considerable potential for leachate treatment owing to its green and simple operation, but the simultaneous removal of chemical oxygen demand (COD) and ammonia from leachate remains challenging. Herein, TiZrO₄ @Cu_SA hollow spheres with high-loading single-atom Cu were synthesized using isovolumic vacuum impregnation and co-calcination methods, and the catalyst was applied to the LTCAO treatment of real leachate. Consequently, the removal rate of UV₂₅₄ reached 66% at 90 °C within 5 h, while that for COD was 88%. Simultaneously, the NH₃/NH₄⁺ (33.5 mg/L, 100 wt%) in the leachate was oxidized to N₂ (88.2 wt%), NO₂^--N (11.0 wt%), and NO₃^--N (0.3 wt%) owing to the effect of free radicals. The single-atom Cu co-catalyst in TiZrO₄ @Cu_SA exhibited a localized surface plasmon resonance effect at the active center, which could quickly transfer electrons to O₂ in water to form O₂^.- with a high activation efficiency. The degradation products were determined and the deduced pathway was as follows: the bonds joining benzene rings were first broken, and then the ring structure was further opened to produce acetic acid and other simple organic macromolecules, which were finally mineralized to CO₂ and H₂O.

DOM tracking and prediction of rural domestic sewage with UV-vis and EEM in the Yangtze River Delta, China

Compared with the urban sewage treatment plants, the operation of rural decentralized sewage facilities is trapped by the absence of professionals, thus having to be run dependently on the self-adaptive operation of the facilities, which makes timely monitoring particularly important. In this study, organic pollutants in rural domestic sewage and urban domestic sewage are analyzed using ultraviolet-visible (UV-vis) absorption spectroscopy, fluorescence excitation-emission matrix (EEM) and Fourier transform infrared reflectance (FTIR). Compared with the UV-vis absorption spectrum, EEM can not only make up the deficiency in the detection of some easily degradable organics in sewage, but also reveal the transformation of different components, thus indicating timely the treatment progress of rural sewage. Linear fitting of COD and spectrum shows that UV₂₅₄ combined with fluorescence excitation-emission at Ex/Em = 250/330 nm might be more suitable for the prediction of COD in rural water than the UV₂₅₄ alone. This is of great significance for guiding the self-adaptive operation of rural domestic sewage facilities, improving their stability and efficiency, so as to improve the rural living environment.

Surrogate-based follow-up of activated carbon adsorption preceded by ozonation for removal of bulk organics and micropollutants from landfill leachate

Although combined ozonation with activated carbon (AC) adsorption is a promising technique for leachate treatment, little is known about how ozone-induced changes in leachate characteristics affect the organics adsorption, especially in view of emerging micropollutants (MPs) removal. Furthermore, the online monitoring of MPs is challenging but desirable for efficient treatment operation. This study investigates how preceding ozonation impacts the adsorption of bulk organics (expressed as chemical oxygen demand (COD)) and ozone-recalcitrant MPs, i.e., primidone, atrazine and alachlor, in leachate using batch and column adsorption tests. Additionally, a new surrogate-based model was evaluated for predicting MPs breakthrough. Batch tests revealed that ozonation results in a decreasing apparent affinity of COD towards AC, but the non-adsorbable part did not obviously change. The adsorption of MPs in ozonated leachate was (1-41%) higher than that in non-ozonated leachate, especially for the more hydrophobic alachlor and atrazine, due to a reduced sites competition from bulk organics. Column adsorption showed that ozonation delayed COD and MPs breakthrough due to the reduced COD loading and sites competition, respectively. An increased empty bed contact time (EBCT, 10-40 min) led to an increased COD uptake by a factor of 3.0-3.2 for ozonated and non-ozonated leachates, while MPs adsorption also increased, suggesting that pore blockage rather than site competition could be the dominant inhibitory effect. The data from column adsorption demonstrate the applicability of developed surrogate-based model for predicting MPs breakthrough. Particularly, the fitting parameters were not affected by change of leachate characteristics, while they were impacted by change of EBCT.

Ozonation of organic compounds in water and wastewater: A critical review

Ozonation has been applied in water treatment for more than a century, first for disinfection, later for oxidation of inorganic and organic pollutants. In recent years, ozone has been increasingly applied for enhanced municipal wastewater treatment for ecosystem protection and for potable water reuse. These applications triggered significant research efforts on the abatement efficiency of organic contaminants and the ensuing formation of transformation products. This endeavor was accompanied by developments in analytical and computational chemistry, which allowed to improve the mechanistic understanding of ozone reactions. This critical review assesses the challenges of ozonation of impaired water qualities such as wastewaters and provides an up-to-date compilation of the recent kinetic and mechanistic findings of ozone reactions with dissolved organic matter, various functional groups (olefins, aromatic compounds, heterocyclic compounds, aliphatic nitrogen-containing compounds, sulfur-containing compounds, hydrocarbons, carbanions, β-diketones) and antibiotic resistance genes.

Identification of surrogates for rapid monitoring of microbial inactivation by ozone for water reuse: A pilot-scale study

The complex contaminants in reclaimed water sources and delayed feedback of microbial detection have brought tremendous challenges to disinfection process control. The identification of sensitive and online surrogates for indicating microbial inactivation efficacy is vital to evaluate and optimize the disinfection technologies and processes. This study analyzes the inactivation of microbial indicators during ozone disinfection at a pilot-scale study over 5 months. It is identified that total fluorescence (TF) intensity, ultraviolet absorbance at 254 nm (UV₂₅₄) and intracellular adenosine triphosphate (cATP) concentration can act as surrogates in predicting microbial inactivation by ozone. Particularly, the empirical linear correlations for log removal values (LRV) of TF, UV₂₅₄ and cATP concentration are developed for the inactivation of four widely applied microbial indicators, namely the total coliforms, fecal coliforms, Escherichia coli (E. coli) and heterotrophic plate count (HPC) (R² = 0.86-0.96). Validation analyses are further conducted to verify the robustness and effectiveness of empirical models. Notably, TF is considered as the most efficient surrogate due to its high sensitivity, accuracy and reliability, whereas cATP concentration is an efficient supplement to directly reflect total microbial counts. The study is important to provide a rapid and reliable approach for ozone disinfection efficiency evaluation and prediction.

Formation and control of disinfection by-products from iodinated contrast media attenuation through sequential treatment processes of ozone-low pressure ultraviolet light followed by chlorination

Different groups of disinfection by-products (DBPs) were studied through the degradation of iopamidol by the sequential oxidation process of ozone-low pressure ultraviolet light (O₃-LPUV) followed by chlorination. This paper investigates the attenuation of iopamidol under this sequential treatment and the effect of chlorine contact time (30 min versus 3 days) to control the formation potential of DBPs: trihalomethanes (THMs), haloacetonitriles (HANs) and haloacetamides (HAMs). Thirty target DBPs among the 9 iodinated-DBPs (I-DBPs), were monitored throughout the sequential treatment. Results showed that O₃-LPUV removed up to 99% of iopamidol, while ozone and LPUV alone removed only 90% and 76% respectively. After chlorine addition, O₃-LPUV yielded 56% lower I-DBPs than LPUV. Increasing chlorine contact time resulted in higher concentrations of all DBP groups (THMs, HANs, and HAMs), with the exception of I-DBPs. One new iodinated-haloacetamide, namely chloroiodoacetamide (CIACM) and one iodoacetonitrile (IACN) were detected. These results suggest the iodine incorporated in iopamidol may be a precursor for iodinated-nitrogenous-DBPs, which are currently not well studied.

Comparison of the new Cl2/O3/UV process with different ozone- and UV-based AOPs for wastewater treatment at pilot scale: Removal of pharmaceuticals and changes in fluorescing organic matter

This work critically compared the removal of fluorescing PARAFAC components and selected pharmaceuticals (carbamazepine, fluoxetine, gemfibrozil, primidone, sulfamethoxazole, trimethoprim) from a tertiary wastewater effluent by different UV- and ozone-based advanced oxidation processes (AOPs) operated at pilot-scale. Investigated AOPs included UV/H₂O₂, UV/Cl₂, O₃, O₃/UV, H₂O₂/O₃/UV, and the new Cl₂/O₃/UV. AOPs comparison was accomplished using various ozone doses (0-9 mg/L), UV fluences (191-981 mJ/cm²) and radical promoter concentrations of Cl₂ = 0.04 mM and H₂O₂ = 0.29 mM. Chlorine-based AOPs produced radical species that reacted more selectively with pharmaceuticals than radical species and oxidants generated by other AOPs. Tryptophan-like substances and humic-like fluorescing compounds were the most degraded components by all AOPs, which were better removed than microbial products and fulvic-like fluorescing substances. Removal of UV absorbance at 254 (UV₂₅₄) nm was always low. Overall, chlorine-based AOPs were more effective to reduce fluorescence intensities than similar H₂O₂-based AOPs. The Cl₂/O₃/UV process was the most effective AOP to degrade all target micro-pollutants except primidone. On the other hand, the oxidation performance of pharmaceuticals by other ozone-based AOPs followed the order H₂O₂/O₃/UV > O₃/UV > O₃. UV/Cl₂ process outcompeted UV/H₂O₂ only for the removal of trimethoprim and sulfamethoxazole. Correlations between the removal of pharmaceuticals and spectroscopic indexes (PARAFAC components and UV₂₅₄) had unique regression parameters for each compound, surrogate parameter and oxidation process. Particularly, a diverse PARAFAC component for each investigated AOP resulted to be the most sensitive surrogate parameter able to monitor small changes of pharmaceuticals removal.

Ozonation Treatment Increases Chlorophenylacetonitrile Formation in Downstream Chlorination or Chloramination

Chlorophenylacetonitriles (CPANs) are an emerging group of aromatic nitrogenous disinfection byproducts (DBPs). However, their dominant precursors and formation pathways remain unclear, which hinders the further development of effective control strategies. For the first time, CPAN precursors were screened by conducting formation potential (FP) tests on real water samples from six drinking water treatment plants (DWTPs). The average overall removal of CPAN precursors across all six DWTPs was only 10%. Moreover, ozonation increased CPAN precursors by 140% on average. Fluorescence spectroscopy showed a dramatic reduction in aromatic proteins, tyrosine-like proteins, and tryptophan-like proteins following ozonation. Low-apparent-molecular-weight (AMW) (<1 kDa) substances were correlated with the CPAN FP in these samples. We therefore hypothesized that protein fragments with low AMW, such as amino acids, are important CPAN precursors during downstream chlor(am)ination. Two aromatic free amino acids, tyrosine and tryptophan, were selected to investigate the formation of CPANs during chlor(am)ination. Both amino acids were found to act as CPAN precursors for the first time. CPAN formation pathways from these model precursors were proposed based on the frontier molecular orbital theory and intermediate products identified using high-resolution mass spectrometry. This study provides a powerful theoretical foundation for controlling CPAN formation in drinking water.

Surrogates for on-line monitoring of the attenuation of trace organic contaminants during advanced oxidation processes for water reuse

The large number of trace organic contaminants (TrOCs) in wastewater has resulted in severe concerns to human health. Ozonation and UV/H₂O₂ are widely used to remove TrOCs in wastewater treatment process. Owing to the trace concentrations of TrOCs in wastewater, real-time monitoring of the abatement efficiency of TrOCs through ozonation and UV/H₂O₂ is quite challenging. Instead of a direct measurement of all the TrOCs, the research community has begun to use different surrogates to monitor the attenuation of TrOCs during AOPs. Various surrogates have been developed over the past few decades. In this review, the different types of surrogates are summarized, including ultraviolet spectroscopy and fluorescence spectroscopy. Strong linear correlations have been found for the removal of TrOCs using AOPs, and the abatement of UV absorption spectroscopy at 254 nm or total fluorescence (TF). Moreover, a two-phase linear correlation can better describe the ozone-resistant TrOCs compared with a single linear correlation. Two different kinds of predictive models exist that use surrogates as the input for ozonation: the regression model and kinetic model. The development of the models requires a further understanding of the impacts of water quality, seasonal variations, and storm events on the kinetic parameters. For the in situ monitoring system, the light-emitting diode (LED) is one of the most promising light sources, although the sensitivity and accuracy still need to be improved.

Fluorescence excitation/emission matrices as a tool to monitor the removal of organic micropollutants from wastewater effluents by adsorption onto activated carbon

Monitoring the removal of organic micropollutants (OMPs) in advanced wastewater treatment facilities requires expensive and time-consuming analytical methods that cannot be installed online. Spectroscopic techniques such as fluorescence excitation/emission spectroscopy were demonstrated to offer the potential for monitoring OMPs removal in conventional wastewater treatment plants or ozonation pilots but their application to activated carbon (AC) adsorption processes was only investigated at lab scale and not in real treatment facilities. In this study, indexes from fluorescence emission/excitation matrices (EEMs) were used to find correlations with the removal of 28 OMPs from a large-scale AC pilot in fluidized bed employed for wastewater advanced treatment, as well as from batch experiments. Differences in OMPs removal could be observed depending on the operational conditions (i.e. pilot or batch experiments, contact time, type of AC) and the physico-chemical properties of the molecules. 7 PARAFAC components were derived from the fluorescence EEMs of 60 samples obtained before and after adsorption. Positive correlations were obtained between the removal of fluorescence indexes and most OMPs, and correlation coefficients were much higher than the ones obtained with UV₂₅₄, confirming the interesting potential of fluorescence spectroscopy to accurately monitor adsorption performances at the industrial scale. The highest correlation coefficients were obtained for OMPs having the best removals while the ones that were refractory to adsorption, as well as to interactions with DOM, exhibited weak correlations. These results suggest that interactions between OMPs and fluorescing DOM and their subsequent co-adsorption onto AC were at the origin of the correlations found. Lower correlations were also found for the most biodegradable OMPs, which indicated that the occurrence of biological effects could make the monitoring of these compounds more challenging.

Pretreatment using UV combined with CaO2 for the anaerobic digestion of waste activated sludge: Mechanistic modeling for attenuation of trace organic contaminants

Trace organic contaminants (TOrCs) in waste active sludge (WAS) have caused many concerns due to their recalcitrance and detriment to the performance of anaerobic digestion (AD). In this study, UV (2 h) combined with calcium peroxide (CaO₂, 0.1 g g^-1-VSS (VSS, volatile suspended solid) was proposed as a suitable sludge pretreatment to enhance the AD performance with an increase in the production of maximum total short-chain fatty acids (421.3 %) and methane (119.2 %). Meanwhile, above 50 % removal efficiency for 19 detected TOrCs was achieved. UV and CaO₂ had a synergistic effect on the subsequent AD of WAS. Both UV and Ca(OH)₂ produced by CaO₂ played important roles in the dissolution of WAS and the subsequent AD, while UV-direct and OH-indirect photolysis accounted for TOrCs attenuation. In order to predict TOrCs attenuation by UV/CaO₂ treatment, a TOrCs photolysis model was tentatively established using carbamazepine as an indicator. This predictive model expressed a good prediction with adj-R² = 0.94, and the difference of predicted and measured values was within 27.3 %. This work evaluates a sludge pretreatment for simultaneously TOrCs attenuation and methane accumulation, laying foundation for promotion of sludge resource recycling.

Quantification of the electron donating capacity and UV absorbance of dissolved organic matter during ozonation of secondary wastewater effluent by an assay and an automated analyzer

Ozonation of secondary wastewater treatment plant effluent for the abatement of organic micropollutants requires an accurate process control, which can be based on monitoring ozone-induced changes in dissolved organic matter (DOM). This study presents a novel automated analytical system for monitoring changes in the electron donating capacity (EDC) and UV absorbance of DOM during ozonation. In a first step, a quantitative photometric EDC assay was developed based on electron-transfer reactions from phenolic moieties in DOM to an added chemical oxidant, the radical cation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS^·+). The assay is highly sensitive (limit of quantification ∼0.5 mg_DOC·L^-1) and EDC values of model DOM isolates determined by this assay were in good agreement with values determined previously by mediated electrochemical oxidation (slope = 1.01 ± 0.07, R² = 0.98). In a second step, the photometric EDC measurement method was transferred onto an automated fluidic system coupled to a photometer (EDC analyzer). The EDC analyzer was then used to monitor changes in EDC and UV absorbance of secondary wastewater effluent treated with ozone. While both parameters exhibited a dose-dependent decrease, a more pronounced decrease in EDC as compared to UV absorbance was observed at specific ozone doses up to 0.4 mg_O3·g_DOC^-1. The concentration of 17α-ethinylestradiol, a phenolic micropollutant with a high ozone reactivity, decreased proportionally to the EDC decrease. In contrast, abatement of less ozone-reactive micropollutants and bromate formation started only after a pronounced initial decrease in EDC. The on-line EDC analyzer presented herein will enable a comprehensive assessment of the combination of EDC and UV absorbance as control parameters for full-scale ozonation.

Development of fluorescence surrogates to predict the ferrate(VI) oxidation of pharmaceuticals in wastewater effluents

The removal of pharmaceuticals from wastewater effluents is an emerging concern for environmental scientists and engineers. Ferrate(VI) (Fe^VIO₄^2-, Fe^VI) is a promising oxidant and the removal of pharmaceuticals from wastewater effluents has been investigated in this study. Firstly, Fe^VI oxidation of selected pharmaceuticals was examined by determining the apparent second-order rate constants (k_app) in buffer solutions as a function of pH (5.0-9.5). At pH 8.0, k_app of cimetidine, famotidine, nalidixic acid, ronidazole, dimetridazole, tinidazole, and caffeine are (1.6 ± 0.2)×10³, (7.8 ± 0.3)×10², 2.6 ± 0.4, 1.7 ± 0.1, 0.9 ± 0.3, 0.2 ± 0.1, and < 0.1 M^-1 s^-1, respectively. However, k_app could not be directly employed to predict the removal of pharmaceuticals in the effluents due to the inhibited or enhanced effects of effluent organic matters (EfOM). Therefore, an alternative approach of spectroscopic surrogates was investigated since fluorophore was co-degraded with pharmaceuticals in the wastewater effluents. Particularly, the humic-like fluorescent peak correlated well with the pharmaceutical attenuation. The relationship of the reduction of fluorescence and the removal of pharmaceuticals could be described through a universal equation: [Formula: see text] . The practical utility of the fluorescence surrogate was validated by applying to field samples. Monitoring the changes of the fluorescence surrogate provides a promising, rapid, and inexpensive method for estimating the degradation of pharmaceuticals during Fe^VI treatment of wastewater effluents.

Statistical profiling for identifying transformation products in an engineered treatment process

This study demonstrated statistical profiling consisting of the analysis of variance (ANOVA) and fold change to efficiently identify transformation products of an organic model compound (i.e., carbamazepine, CBZ) in ozonation. To this end, liquid chromatography (LC)-quadrupole time-of-flight mass spectrometry (QTOF-MS) was employed to measure the accurate masses of CBZ transformation products. Subsequently, statistical profiling was applied to differentiating features that are uniquely present in the ozonated samples from those in blanks and control (i.e., CBZ sample without ozonation). The identified transformation products had significant statistical power (i.e., power, 1-β > 0.8) in post hoc power analysis, which suggests that the profiling procedure can be an efficient means of reducing false negative in data analysis. 2-quinazolinone was newly reported here as a tentative transformation of CBZ during ozonation. In addition, a transformation product with one less carbon than CBZ, often called "anomalous" transformation product, was also found. While statistical profiling was applied to a model experiment, such an approach can be further utilized to screen many features with a higher data complexity such as non-targeted screening (NTS) and non-target analysis (NTA) for environmental samples.

Paradigm shifts and current challenges in wastewater management

Wastewater is a significant environmental and public health concern which management is a constant challenge since antiquity. Wastewater research has increased exponentially over the last decades. This paper provides a global overview of the exponentially increasing wastewater research in order to identify current challenges and paradigm shifts. Besides households, hospitals and typical industries, other sources of wastewater appear due to emerging activities like hydraulic fracturing. While the composition of wastewater needs constant reassessment to identify contaminants of interest, the comprehensive chemical and toxicological analysis remains one of the main challenges in wastewater research. Moreover, recent changes in the public perception of wastewater has led to several paradigm shifts: i) water reuse considering wastewater as a water resource rather than a hazardous waste, ii) wastewater-based epidemiology considering wastewater as a source of information regarding the overall health of a population through the analysis of specific biomarkers, iii) circular economy through the implementation of treatment processes aiming at harvesting valuable components such as precious metals or producing valuable goods such as biofuel. However, wastewater research should also address social challenges such as the public acceptance of water reuse or the access to basic sanitation that is not available for nearly a third of the world population.

Monitoring NDMA precursors throughout membrane-based advanced wastewater treatment processes by organic matter fluorescence

This study investigates the potential of fluorescence excitation/emission matrices (EEM) measurement as a tool to predict N-Nitrosodimethylamine (NDMA) formation in water reuse applications. In particular, samples from a pilot-scale membrane biological reactor (MBR) followed by nanofiltration (NF) advanced water treatment plant, are used for the study. Concentrations of both, specific NDMA precursors and NDMA formation potential (FP) are correlated with different EEM peaks. The specific precursors investigated are: erythromycin, azithromycin, clarithromycin, venlafaxine, o-desmethylvenlafaxine, ranitidine and citalopram, while the NDMA FP is conventionally measured by the NDMA formation potential test. EEM peaks investigated are obtained by fluorescence regional integration as well as by the peak picking method generating I₁, I₂, I₃, I₄, and I₅ peaks. Results showed that protein-like materials are correlated with the bulk NDMA FP and specific NDMA precursors. Additionally, selected fluorescence peaks such as I₁, I₂ and I₄ are strongly correlated with NDMA precursors throughout the MBR-NF pilot plant. The removal of NDMA precursors and EEM peaks also correlated well (R² > 0.8). This data shows that fluorescence EEM can be a promising tool to monitor the concentration of NDMA precursors and their removal in water reuse application.

Elimination of isothiazolinone biocides in reverse osmosis concentrate by ozonation: A two-phase kinetics and a non-linear surrogate model

Elimination of commercial Kathon biocide (methyl-isothiazolinone (MIT) and chloro-methyl-isothiazolinone (CMIT) mixture) by ozonation was investigated in real RO influent and concentrate. MIT and CMIT had different reactivities (second-order-rate-constants) with molecular ozone and OH. Ozonation of biocides followed an instantaneous phase (16.6 %-36.9 % contributions) and then a gradual phase (33.6 %-78.8 % contributions). Newly developed kinetics including both phases demonstrated that O₃ oxidation contributed 25.6 %-39.8 % and <10 % of MIT and CMIT eliminations, respectively, and OH oxidation contributed 60.2 %-74.4 % and >90 % of MIT and CMIT eliminations, respectively. OH oxidation at the instantaneous phase accounted 15.7 %-37.9 % of total OH oxidation. Mass ratios of O₃/DOC of 0.24 and 0.32 were needed for ∼80 % eliminations of MIT and CMIT in RO concentrate, respectively. The kinetics including both phases allowed a para-chlorobenzoic acid indicator model to predict MIT and CMIT elimination better than that including gradual ozonation only, with 58.9 %-96.0 % lower relative error. The attenuations of electron-donating-moiety indicated that O₃ may preferentially react with chromophores through aromatic cleavage and electrophilic extraction, while ^•OH may non-selectively react with chromophores through predominant electrophilic addition. A surrogate model for biocide elimination by UVA₂₅₄ loss was proposed to be nonlinear rather than linear, which reduced 31.8 %-71.3 % surrogating error.

Continuous versus single H2O2 addition in peroxone process: Performance improvement and modelling in wastewater effluents

Ozonation combined with continuous addition of H₂O₂ was studied as potential strategy for the effective abatement of ozone-resistant micropollutants from wastewater effluents. Oxidant doses within and beyond immediate ozone demand completion were tested. Through experiments involving the continuous addition of H₂O₂ in a semi-continuous contactor, it was demonstrated that this new approach could lead to a 36 % reduction of the overall O₃ needs for a constant H₂O₂/O₃ molar ratio of 0.25 compared to single ozonation, representing a 28 % reduction in energy consumption. This improvement was mainly attributed to H₂O₂ addition during the secondary ozonation stage, where the direct ozone demand becomes less important. The OH-exposure per consumed ozone (i.e., R_OHO3 concept) calculation demonstrated that higher (0.5-1) and lower (0.25) oxidant relationships work better in improving the process performance during initial and secondary stages, respectively. Moreover, continuous versus total initial addition of H₂O₂ were compared and the first one showed better performance, representing differences in energy costs up to 21 %. Finally, two strategies for the real-time control of the O₃-recalcitrant MPs fate were tested, one based on the R_OHO3 concept and the other on UVA₂₅₄ monitoring. Both resulted in accurate predictions (R² > 0.96) for different compounds, effluents and processes.

Characterizing the molecular weight distribution of dissolved organic matter by measuring the contents of electron-donating moieties, UV absorbance, and fluorescence intensity

Electron-donating moieties (EDM) have recently been used to characterize the redox properties and treatability of dissolved organic matter during water and wastewater treatment. In this study, size exclusion chromatography followed by a derivatization-spectrometric method was developed to determine the molecular weight (MW) distribution of EDM in dissolved organic matter. The relationships between EDM concentration and chromophore content (indicated by UVA₂₅₄), fluorophore content (indicated by fluorescence), and dissolved organic carbon (DOC) concentration were analyzed for different MW fractions. In general, natural organic matter (NOM) showed higher total EDM concentration and higher EDM average MW than effluent organic matter (EfOM). For NOM, fractions with MW between 1.8 k and 6.9 k Da accounted for most of the EDM (45.4%-48.6%), followed by the fractions with MW < 1.8 k Da (25.6%-42.4%). By contrast, the EDM in EfOM occurred predominantly in fractions with MW < 1 k Da (51.8%-58.6%), with lower concentrations in fractions with MW > 1.8 k Da (<20.2%). The heterogeneous MW distribution of EDM was strongly correlated to the presence of chromophores, but not DOC or fluorophores. The EDM difference between MW fractions suggested that the fraction with MW 1.8-6.9 k Da (40.7%-47.1%) and the fractions with MW < 1 k Da (50.2%-58.8%) should be the dominant oxidant consumers in NOM and EfOM, respectively. When the EDM was normalized by the DOC for each MW fraction (EDM_MW/DOC_MW), the EDM_MW/DOC_MW of relatively high-MW fractions (>1.8 k Da) is 1.2-1.9 times of relatively low-MW (<1 k Da) fractions for both NOM and EfOM, which indicates that higher-MW fractions are more susceptible to chemical oxidations. The relationship between EDM change and UVA₂₅₄ change varied for different MW fractions during advanced ozonation treatment, because of the different oxidation mechanisms in operation for MW fractions. The ozonation of EfOM fractions with higher MW (>1.8 k Da) and lower MW (<1 k Da) preferentially resulted in benzoquinone formation and ring-cleavage, respectively.

Modelling of emerging contaminant removal during heterogeneous catalytic ozonation using chemical kinetic approaches

This study evaluated the prediction of emerging contaminant (EC) removal during heterogeneous catalytic ozonation by chemical kinetic models. Six ECs with differing ozone reactivity were spiked in a synthetic water and a groundwater, then treated by conventional ozonation and heterogeneous catalytic ozonation with α- or β-MnO₂ catalysts. Results show that catalysts did not considerably influence the removal of ECs with high and intermediate ozone reactivity (diclofenac, gemfibrozil, and bezafibrate), but enhanced the removal efficiencies of ECs with low ozone reactivity (2,4-dichlorophenoxyacetic acid, clofibric acid, and ibuprofen) to varied extent (˜10-30%). The removal efficiencies of ECs could be reasonably predicted using chemical kinetic models based on the ozone (O₃) and hydroxyl radical (OH) rate constants of ECs, pseudo-first-order rate constants observed for EC adsorption on the MnO₂ catalysts, and O₃ and OH exposures observed for catalytic ozonation. Furthermore, the model reveals that ECs are removed mainly by O₃ and/or •OH oxidation during heterogeneous catalytic ozonation, while adsorption of ECs on catalysts contributes negligibly. Therefore, the removal efficiencies of ECs could be satisfactorily predicted using a simplified model based only on the O₃ and OH rate constant and the O₃ and OH exposures.

Environmental fate of pharmaceutical compounds and antimicrobial-resistant bacteria in hospital effluents, and contributions to pollutant loads in the surface waters in Japan

Environmental fate of 58 pharmaceutical compounds (PhCs) grouped into 11 therapeutic classes in the three different waters, hospital effluent, sewage treatment plant (STP) and river water, was estimated by combination of their quantitative concentration analysis and evaluation of their extent of contribution as loading sources. At the same time, distribution of six classes of antimicrobial-resistant bacteria (AMRB) in the same water samples was estimated by screening of individual PhC-resistant microbes grown on each specific chromogenic medium. The results indicate that 48 PhCs were detected ranged from 1 ng/L (losartan carboxylic acid) to 228 μg/L (acetaminophen sulfate) in hospital effluent, and contribution of the pollution load derived from hospital effluent to STP influent was estimated as 0.1% to 15%. On the other hand, contribution of STP effluent to river water was high, 32% to 60% for antibacterials, antipertensives and X-ray contrast media. In the cases for AMRB, detected numbers of colonies of AMRB in hospital effluent ranged from 29 CFU/mL to 1805 CFU/mL, and the estimated contribution of the AMRB pollution load derived from hospital effluent to STP influent was as low as 0.1% (levofloxacin and olmesartan) to 5.1% (N-desmethyl tamoxifen). Although the contribution of STPs as loading sources of PhCs and AMRB in surface waters was large, ozonation as an advanced water treatment system effectively removed a wide range of both PhCs and AMRB in water samples. These results suggest the importance of reducing environmental pollutant loads (not only at STPs but also at medical facilities) before being discharged into the surface waters, to both conserve water and keep the water environment safe. To our knowledge, this is the first report to show the distribution and contribution of AMRB from hospital effluent to the surface waters.

MP-UV/CaO2 as a pretreatment method for the removal of carbamazepine and primidone in waste activated sludge and improving the solubilization of sludge

Medium-pressure ultraviolet light (MP-UV) combined with calcium peroxide (CaO₂) as a pretreatment technology for removing carbamazepine (CBZ) and primidone (PMD) in waste active sludge (WAS) and improving the solubilization of sludge were investigated. CBZ and PMD were effectively removed and the removal fitted pseudo-first kinetics under MP-UV/CaO₂ treatment with R² > 0.97. The higher CaO₂ dosage and lower initial volatile suspended solids (VSS) concentration were conductive to the removal of CBZ and PMD. Of the CaO₂ hydrolysates, Ca(OH)₂ played a more important role than H₂O₂ during MP-UV/CaO₂ treatment. The removal of the target compounds was attributed to direct photolysis and indirect photolysis caused by •OH, ³DOM^*, and ¹O₂, in which •OH played a vital role with > 62.2% contribution to the overall degradation rate. A model predicting the steady concentration of •OH in WAS ([VSS] ≈ 8.6 g L^-1) under MP-UV/CaO₂ treatment with CaO₂ dosage ranging from 0 to 0.5 g g^-1-VSS was proposed and validated. Moreover, major intermediates of CBZ and PMD were detected and the probable transformation pathways during MP-UV/CaO₂ treatment were proposed. In addition, MP-UV/CaO₂ promoted the sludge solubilization effectively. Considering both the pharmaceutical degradation and sludge solubilization, the optimum operation condition with 0.2 g-CaO₂ g^-1-VSS combined with 7 h MP-UV irradiation is recommended. Under this condition, more than 92.3% of CBZ and 90.3% of PMD were removed, and soluble chemical oxygen demand (SCOD) increased by 657% and 13.6% compared with sole 10 h CaO₂ (0.2 g g^-1-VSS) treatment and 7 h MP-UV treatment, respectively.

Consolidated vs new advanced treatment methods for the removal of contaminants of emerging concern from urban wastewater

Urban wastewater treatment plants (WWTPs) are among the main anthropogenic sources for the release of contaminants of emerging concern (CECs) into the environment, which can result in toxic and adverse effects on aquatic organisms and consequently on humans. Unfortunately, WWTPs are not designed to remove CECs and secondary (e.g., conventional activated sludge process, CAS) and tertiary (such as filtration and disinfection) treatments are not effective in the removal of most CECs entering WWTP. Accordingly, several advanced treatment methods have been investigated for the removal of CECs from wastewater, including consolidated (namely, activated carbon (AC) adsorption, ozonation and membranes) and new (such as advanced oxidation processes (AOPs)) processes/technologies. This review paper gathers the efforts of a group of international experts, members of the NEREUS COST Action ES1403 who for three years have been constructively discussing the state of the art and the best available technologies for the advanced treatment of urban wastewater. In particular, this work critically reviews the papers available in scientific literature on consolidated (ozonation, AC and membranes) and new advanced treatment methods (mainly AOPs) to analyse: (i) their efficiency in the removal of CECs from wastewater, (ii) advantages and drawbacks, (iii) possible obstacles to the application of AOPs, (iv) technological limitations and mid to long-term perspectives for the application of heterogeneous processes, and (v) a technical and economic comparison among the different processes/technologies.

Ecotoxicity and environmental fates of newly recognized contaminants-artificial sweeteners: A review

Artificial sweeteners (ASs) are used in countless application in daily life. ASs are newly recognized as pollutants due to their high detection frequency in various environmental media, which has aroused great concern. This review presents the current knowledge of AS ecotoxicity and possible elimination routes in the environment. The obtained results indicate that the negative impacts of ASs are more severe than previously expected. More attention should be paid to the chronic and metabolite toxicities of ASs. Moreover, numerous processes (physical, chemical and biological) have been reported to be able to degrade ASs. However, the elimination efficiency varies greatly depending on the specific AS and the particular experimental conditions. Cyclamate and saccharin are easily removed, while sucralose and acesulfame are generally persistent. Additionally, there is a large gap in the ASs removal efficiency between bench tests and full-scale studies. The potential for microbial degradation of persistent ASs was reported in some regions, but clarification of the underlying mechanisms is necessary to increase the likelihood of using this approach in wide applications with a satisfactory performance.

Removal of trace organic chemicals in wastewater effluent by UV/H2O2 and UV/PDS

In this study, we comparatively investigated the degradation of 12 trace organic chemicals (TOrCs) during UV/H₂O₂ and UV/peroxydisulfate (PDS) processes. Second-order rate constants for the reactions of iopromide, phenytoin, caffeine, benzotriazole, and primidone with sulfate radical (SO₄^•-) were determined for the first time. Experiments were conducted in buffered pure water and wastewater effluent with spiked TOrCs. UV/PDS degraded all TOrCs more efficiently than UV/H₂O₂ in buffered pure water due to the higher yield of SO₄^•- than that of hydroxyl radical (^•OH) at the same initial molar dose of PDS and H₂O₂, respectively. UV/PDS showed higher selectivity toward TOrCs removal than UV/H₂O₂ in wastewater effluent. Compounds with electron-rich moieties, such as diclofenac, venlafaxine, and metoprolol, were eliminated faster in UV/PDS whereas UV/H₂O₂ was more efficient in degrading compounds with lower reactivity to SO₄^•-. The fluence-based rate constants ( [Formula: see text] ) of TOrCs in wastewater effluent linearly increased as a function of initial H₂O₂ dose during UV/H₂O₂, possibly due to the constant scavenging impact of the wastewater matrix on ^•OH. However, exponential increase of k_obs-UV/PDS with increasing PDS dose was observed for most compounds during UV/PDS, suggesting the decreasing scavenging effect of the water matrix (electron-rich site of effluent organic matter (EfOM)) after initial depletion of SO₄^•- at low PDS dose. Fulvic and humic-like fluorophores appeared to be more persistent during UV/H₂O₂ compared to aromatic protein and soluble microbial product-like fluorophores. In contrast, UV/PDS efficiently degraded all identified fluorophores and showed less selectivity toward the fluorescent EfOM components. Removal pattern of TOrCs during pilot-scale UV/PDS was consistent with lab-scale experiments, however, overall removal rates were lower due to the presence of higher concentration of EfOM and nitrite.

Dynamic validation of online applied and surrogate-based models for tertiary ozonation on pilot-scale

New robust correlation models for ozonation, based on UVA₂₅₄ and fluorescence surrogate parameters and developed considering kinetic information, have been applied at pilot-scale. This model framework is validated with the aim for operators to control the ozone dose for the removal of trace organic contaminants (TrOCs) in effluents from full-scale municipal wastewater treatment plants. The inflected correlation model between ΔTrOCs and the surrogates predicts the removal of TrOCs (based on statistical evidence) solely using the 2nd order reaction rate constant with ozone (k_O3) and in a more adequate manner than similar single correlation models. This allows the use of this new model for current and future TrOCs under investigation which is highly interesting when imposed discharge limits might include more and other TrOCs in future. The use of UVA₂₅₄ might be preferable at the current timing for online monitoring of TrOC abatement as the model showed a good predictive power (based on statistical evidence and visual confirmation). Reliable online sensors are more widespread (and commercially) available compared to fluorescence sensors which are still under development, with the exception of a few examples. Nevertheless, the data processing of the fluorescence signals, isolating the different intensities associated with moieties reacting similarly to ozone might even increase the predictive power, given the lower degree of interference (i.e. less scattering).

Sample handling and data processing for fluorescent excitation-emission matrix (EEM) of dissolved organic matter (DOM)

In environmental engineering and science, fluorescent excitation-emission matrix (EEM) has increasingly been utilized to characterize chromophoric dissolved organic matter (CDOM). This study aims to delineate EEM data processing, including calculation of total fluorescence (TF) which is an emerging water quality parameter often used as a surrogate for micropollutant removal by advanced water treatment processes. In addition, sample handling procedures such as storage, use of preservatives, and oxidant quenching agents were evaluated. In this study, three antimicrobial preservatives were tested: sodium azide, sodium omadine, and thymol. All the tested preservatives altered optical properties of samples, and were therefore not suitable for the preservation of EEM samples. Without preservative, storage of samples at 4 °C maintained TF within 7.5% of its original value for 21 days, while TF of samples stored at the room temperature more drastically changed (up to 15%). The impacts of three oxidant quenching agents including ascorbic acid, sodium bisulfite, and sodium thiosulfate on EEM were also tested. Among the quenching agents, sodium bisulfite was found to be suitable since it little influenced optical properties of samples while the other two were not favorable due to interference. We also scrutinized the use of TF as surrogate to monitor micropollutant rejection by nanofiltration membrane.

Surrogate-Based Correlation Models in View of Real-Time Control of Ozonation of Secondary Treated Municipal Wastewater-Model Development and Dynamic Validation

New robust correlation models for real-time monitoring and control of trace organic contaminant (TrOC) removal by ozonation are presented, based on UVA₂₅₄ and fluorescence surrogates, and developed considering kinetic information. The abatement patterns of TrOCs had inflected shapes, controlled by the reactivity of TrOCs toward ozone and HO^• radicals. These novel and generic correlation models will be of importance for WRRF operators to reduce operational costs and minimize byproduct formation. Both UVA₂₅₄ and fluorescence surrogates could be used to control ΔTrOC, although fluorescence measurements indicated a slightly better reproducibility and an enlarged control range. The generic framework was validated for several WRRFs and correlations for any compound with known kinetic information could be developed solely using the second order reaction rate constant with ozone (k_O3). Two distinct reaction phases were defined for which separate linear correlations were obtained. The first was mainly ozone controlled, while the second phase was more related to HO^• reactions. Furthermore, parallel factor analysis of the fluorescence spectra enabled monitoring of multiple types of organic matter with different O₃ and HO^• reactivity. This knowledge is of value for kinetic modeling frameworks and for achieving a better understanding of the occurring changes of organic matter during ozonation.

Optimization of the precursor removal of dichloroacetonitrile (DCAN), an emerging nitrogenous disinfection by-product, in an up-flow BAC filter

The process parameters of the up-flow biological activated carbon filter (UBACF) were optimized in a pilot-scale trial for controlling the precursor of dichloroacetonitrile (DCAN), an emerging nitrogenous disinfection by-product. The experiments were performed using a central composite design (CCD) with the response surface methodology (RSM). The results showed that the removal efficiencies of formation potentials (FP) of DCAN increased from 28.9% to 64.4% with the optimized ozone dose, expansion rate of BAC and backwashing cycle, being scheduled to 1.52 mg/L, 27% and 9.5 d, respectively. Excitation and emission matrix (EEM) spectra indicated that the fluorescence peaks of aromatic protein (AP) and soluble microbial products-like (SMPs)-like region were weakened significantly in the effluent of improved process (IP) with optimization, which were main precursors of DCAN. The bacterial community before and after the optimization of UBACF was determined using the high-throughput sequencing technology. The class and genus of microorganism demonstrated that the IP had a more diverse microbial community and more even distribution of species in BAC filter. It was favor of the growth of Alphaproteobacteria, Bacilli and Betaproteobacteria attached to the BAC particles, which could biodegrade effectively the precursors of DCAN.

Interaction between Diethyldithiocarbamate and Cu(II) on Gold in Non-Cyanide Wastewater

A surface-enhanced Raman scattering (SERS) detection method for environmental copper ions (Cu2+) was developed according to the vibrational spectral change of diethyldithiocarbamate (DDTC) on gold nanoparticles (AuNPs). The ultraviolet-visible (UV-Vis) absorption spectra indicated that DDTC formed a complex with Cu2+, showing a prominent peak at ~450 nm. We found Raman spectral changes in DDTC from ~1490 cm-1 to ~1504 cm-1 on AuNPs at a high concentration of Cu2+ above 1 μM. The other ions of Zn2+, Pb2+, Ni2+, NH₄⁺, Mn2+, Mg2+, K⁺, Hg2+, Fe2+, Fe3+, Cr3+, Co2+, Cd2+, and Ca2+ did not produce such spectral changes, even after they reacted with DDTC. The electroplating industrial wastewater samples were tested under the interference of highly concentrated ions of Fe3+, Ni2+, and Zn2+. The Raman spectroscopy-based quantification of Cu2+ ions was able to be achieved for the wastewater after treatment with alkaline chlorination, whereas the cyanide-containing water did not show any spectral changes, due to the complexation of the cyanide with the Cu2+ ions. A micromolar range detection limit of Cu2+ ions could be achieved by analyzing the Raman spectra of DDTC in the cyanide-removed water.