Environmental fate and risk evolution of calcium channel blockers from chlorine-based disinfection to sunlit surface waters.

Organic micropollutants present in disinfected wastewater and discharged to sunlit surface waters may be transformed by multiple processes, such as chlorination due to the presence of chlorine residuals, solar irradiation as well as solar-irradiated chlorine residues. This study reports, for the first time, the multi-scenario degradation kinetics, transformation products, and risk evolution of calcium channel blockers (CCBs), a class of emerging pharmaceutical contaminants with worldwide prevalence in natural waters and wastewater. It was found that the chlorination of the studied CCBs (amlodipine (AML) and verapamil (VER)) was dominated by the reaction of HOCl with their neutral species, with second-order rate constants of 6.15×104 M-1 s-1 (AML) and 7.93×103 M-1 s-1 (VER) at pH 5.0-11.0. Bromination is much faster than chlorination, with the measured kapp,HOBr values of 2.94×105 M-1 s-1 and 6.58×103 M-1 s-1 for AML and VER, respectively, at pH 7.0. Furthermore, both CCBs would undergo photolytic attenuations with hydroxyl and carbonate radicals as the dominant reactive species in water. Notably, free chlorine mainly contributed to their abatement during the solar/chlorine treatment. Additionally, the halogen addition on the aromatic ring was observed during chlorination and bromination of the two CCBs. Cyclization was observed under solar irradiation only, while the aromatic ring was opened in the solar/chlorine system. Some products generated by the three transformation processes exhibited non-negligible risks of high biodegradation recalcitrance and toxicity, potentially threatening the aquatic environment and public health. Overall, this study elucidated the environmental fate of typical CCBs under different transformation processes to better understand the resulting ecological risks in these environmental scenarios.

Mitigating risks and maximizing sustainability of treated wastewater reuse for irrigation.

Scarcity of freshwater for agriculture has led to increased utilization of treated wastewater (TWW), establishing it as a significant and reliable source of irrigation water. However, years of research indicate that if not managed adequately, TWW may deleteriously affect soil functioning and plant productivity, and pose a hazard to human and environmental health. This review leverages the experience of researchers, stakeholders, and policymakers from Israel, the United-States, and Europe to present a holistic, multidisciplinary perspective on maximizing the benefits from municipal TWW use for irrigation. We specifically draw on the extensive knowledge gained in Israel, a world leader in agricultural TWW implementation. The first two sections of the work set the foundation for understanding current challenges involved with the use of TWW, detailing known and emerging agronomic and environmental issues (such as salinity and phytotoxicity) and public health risks (such as contaminants of emerging concern and pathogens). The work then presents solutions to address these challenges, including technological and agronomic management-based solutions as well as source control policies. The concluding section presents suggestions for the path forward, emphasizing the importance of improving links between research and policy, and better outreach to the public and agricultural practitioners. We use this platform as a call for action, to form a global harmonized data system that will centralize scientific findings on agronomic, environmental and public health effects of TWW irrigation. Insights from such global collaboration will help to mitigate risks, and facilitate more sustainable use of TWW for food production in the future.

Degradation of methotrexate by unactivated and solar-activated peroxymonosulfate in water: Moiety-specific reaction kinetics and transformation product-associated risks.

Anticancer drugs have raised worldwide concern owing to their ubiquitous occurrence and ecological risks, necessitating the development of efficient removal strategies in water and wastewater treatment. Although peroxymonosulfate (PMS) is known to be a promising chemical in water decontamination, limited information is available regarding the removal efficiency of anticancer drugs by PMS and solar/PMS systems. This study first reports the moiety-specific reaction kinetics and mechanisms of methotrexate (MTX), an anticancer drug with widespread attention, by PMS (unactivated) and solar-activated PMS in water. It was found that MTX abatement by the direct PMS oxidation followed second-order kinetics, and the pH-dependent rate constants increased from 0.4 M-1 s-1 (pH 5.0) to 1.3 M-1 s-1 (pH 8.0), with a slight decrease to 1.1 M-1 s-1 at pH 9.0. The presence of chloride and bromide exerted no obvious influence on the removal of MTX by PMS. Furthermore, the chemical reactivity of MTX and its seven substructures with different reactive species was evaluated, and the degradation contributions of the reactive species involved were quantitatively analyzed in the solar/PMS system. The product analysis suggested similar reaction pathways of MTX by PMS and solar/PMS systems. The persistence, bioaccumulation, and toxicity of the transformation products were investigated, indicating treatment-driven risks. Notably, MTX can be removed efficiently from both municipal and hospital wastewater effluents by the solar/PMS system, suggesting its great potential in wastewater treatment applications. Overall, this study systematically evaluated the elimination of MTX by the unactivated PMS and solar/PMS treatment processes in water. The obtained findings may have implications for the mechanistic understanding and development of PMS-based processes for the degradation of such micropollutants in wastewater.

Looking into the effects of co-contamination by micro(nano)plastics in the presence of other pollutants on irrigated edible plants.

To address water shortage challenges, treated wastewater is used to meet the demand for irrigation water in several countries worldwide. Considering the presence of pollutants in treated wastewater, its use for land irrigation might have an impact in the environment. This review article focuses on the combined effects (or potential joint toxicity) of microplastics (MPs)/nanoplastics (NPs) and other environmental contaminants present in treated wastewater on edible plants after irrigation. Initially, the concentrations of MPs/NPs in wastewater treatment plant effluents and surface waters are summarized, indicating the presence of MPs/NPs in both water matrices (i.e., wastewater after receiving treatment and lakes/rivers). Then, the results of 19 studies related to joint toxicity of MPs/NPs and co-contaminants (e.g., heavy metals and pharmaceuticals) on edible plants, are reviewed and discussed. This concurrent presence may result in several combined effects on edible plants, e.g., rapid root growth, increase in antioxidant enzymes, decrease in photosynthetic rate and increased production of ROS. These effects, as discussed in the various studies on which this review is based, can generate antagonistic or even neutral impact on plants, depending on the size of MPs/NPs and their mixing ratio with the co-contaminants. However, a combined exposure of edible plants to MPs/NPs and co-contaminants can also lead to hormetic adaptive responses. The data reviewed and discussed herein may relieve overlooked environmental impacts of treated wastewater reuse and may be useful to address challenges related to the combined effects of MPs/NPs and co-contaminants on edible plants after irrigation. The conclusions drawn in this review article are relevant to both direct (i.e., treated wastewater irrigation) and indirect (i.e., discharging treated wastewater in surface waters used for irrigation purposes) reuse, and may contribute to the implementation of the European Regulation 2020/741 on the minimum requirements for water reuse.

Chlorination of methotrexate in water revisited: Deciphering the kinetics, novel reaction mechanisms, and unexpected microbial risks.

Chlorination of a typical anticancer drug with annually ascending use and global prevalence (methotrexate, MTX) in water has been studied. In addition to the analysis of kinetics in different water/wastewater matrices, high-resolution product identification and in-depth secondary risk evaluation, which were eagerly urged in the literature, were performed. It was found that the oxidation of MTX by free available chlorine (FAC) followed first-order kinetics with respect to FAC and first-order kinetics with respect to MTX. The pH-dependent rate constants (kapp) ranged from 170.00 M-1 s-1 (pH 5.0) to 2.68 M-1 s-1 (pH 9.0). The moiety-specific kinetic analysis suggested that 6 model substructures of MTX exhibited similar reactivity to the parent compound at pH 7.0. The presence of Br- greatly promoted MTX chlorination at pH 5.0-9.0, which may be ascribed to the formation of bromine with higher reactivity than FAC. Comparatively, coexisting I- or humic acid inhibited the degradation of MTX by FAC. Notably, chlorination effectively abated MTX in different real water matrices. The liquid chromatography-high resolution mass spectrometry analysis of multiple matrix-mediated chlorinated samples indicated the generation of nine transformation products (TPs) of MTX, among which seven were identified during FAC oxidation for the first time. In addition to the reported electrophilic chlorination of MTX (the major and dominant reaction pathway), the initial attacks on the amide and tertiary amine moieties with C-N bond cleavage constitute novel reaction mechanisms. No genotoxicity was observed for MTX or chlorinated solutions thereof, whereas some TPs were estimated to show multi-endpoint aquatic toxicity and higher biodegradation recalcitrance than MTX. The chlorinated mixtures of MTX with or without Br- showed a significant ability to increase the conjugative transfer frequency of plasmid-carried antibiotic resistance genes within bacteria. Overall, this work thoroughly examines the reaction kinetics together with the matrix effects, transformation mechanisms, and secondary environmental risks of MTX chlorination.

Multiclass target analysis of contaminants of emerging concern including transformation products, soil bioavailability assessment and retrospective screening as tools to evaluate risks associated with reclaimed water reuse.

The occurrence of 200 multiclass contaminants of emerging concern (CECs) encompassing 168 medicinal products and transformation products (TPs), 5 artificial sweeteners, 12 industrial chemicals, and 15 other compounds was investigated in influent and effluent wastewater samples collected during 7 consecutive days from 5 wastewater treatment plants (WWTPs) located in Cyprus. The methodology included a generic solid-phase extraction protocol using mixed-bed cartridges followed by Ultra-High Performance Liquid Chromatography coupled with Quadrupole-Time of Flight Mass Spectrometry (UHPLC-QTOF-MS) analysis. A total of 63 CECs were detected at least in one sample, with 52 and 55 out of the 200 compounds detected in influents and effluents, respectively. Ten (10) out of the 24 families of parent compounds and associated TPs were found in the wastewater samples (influent or effluent). 1-H-benzotriazole, carbamazepine, citalopram, lamotrigine, sucralose, tramadol, and venlafaxine (>80 % frequency of appearance in effluents) were assessed with respect to their bioavailability in soil as part of different scenarios of irrigation with reclaimed water following a qualitative approach. A high score of 12 (high probability) was predicted for 2 scenarios, a low score of 3 (rare occasions) for 2 scenarios, while the rest 28 scenarios had scores 5-8 (unlikely or limited possibility) and 9-11 (possibly). Retrospective screening was performed with the use of a target database of 2466 compounds and led to the detection of 158 additional compounds (medicinal products (65), medicinal products TPs (15), illicit drugs (7), illicit drugs TPs (3), industrial chemicals (11), plant protection products (25), plant protection products TPs (10), and various other compounds (22). This work aspires to showcase how the presence of CECs in wastewater could be investigated and assessed at WWTP level, including an expert-based methodology for assessing the soil bioavailability of CECs, with the aim to develop sustainable practices and enhance reclaimed water reuse.

Investigation of the effect of microplastics on the UV inactivation of antibiotic-resistant bacteria in water.

This study investigated the effect of polyethylene and polyvinyl chloride microplastics on the UV fluence response curve for the inactivation of multidrug-resistant E. coli and enterococci in ultrapure water at pH 6.0 ± 0.1. In the absence of microplastics, the UV inactivation of the studied bacteria exhibited an initial resistance followed by a faster inactivation of free (dispersed) bacteria, while in the presence of microplastics, these 2 regimes were followed by an additional regime of slower or no inactivation related to microplastic-associated bacteria (i.e., bacteria aggregated with microplastics resulting in shielding bacteria from UV indicated by tailing at higher UV fluences). The magnitude of the negative effect of microplastics varied with different microplastics (type/particle size) and bacteria (Gram-negative and Gram-positive). Results showed that when the UV transmittance of the microplastic-containing water was not taken into account in calculating UV fluences, the effect of microplastics as protectors of bacteria was overestimated. A UV fluence-based double-exponential microbial inactivation model accounting for both free and microplastic-associated bacteria could describe well the disinfection data. The present study elucidated the effect of microplastics on the performance of UV disinfection, and the approach used herein to prove this concept may guide future research on the investigation of the possible effect of other particles including nanoplastics with different characteristics on the exposure response curve for the inactivation of various microorganisms by physical and chemical disinfection processes in different water and wastewater matrices.

Effect of ferrate pretreatment on anaerobic digestibility of primary sludge spiked with resin acids.

Resin acids are mixtures of high molecular weight carboxylic acids found in tree resins. Due to higher hydrophobicity and low solubility, they tend to adsorb on the suspended solids in pulp and paper (P&P) mill wastewater and accumulate in primary sludge through settling. Anaerobic digestion (AD) is a common practice stabilizing sludge; however, high concentration of resin acids affects the AD process. The aim of this research was mainly to determine the impact of ferrate (Fe (VI)) oxidation on selected resin acids and anaerobic digestibility of ferrate-treated primary sludge (PS) spiked with the resin acids. First, batch control oxidation of model resin acids with Fe (VI) was conducted to identify an optimum dosage, pH and contact time using a Box-Behnken design approach. Thereafter, anaerobic treatability studies of primary sludge spiked with resin acids both under control condition and optimum ferrate pretreatment were conducted. Up to 97% oxidation of resin acids occurred in pure water, while only 44%-62% oxidation of resin acids occurred in PS with an increasing Fe (VI) dosage from 0.034 to 0.137 mg Fe (VI)/mg tCODfed. The pretreatment did not affect the anaerobic biodegradability of resin acids; however, it lowered their negative influences on the PS digestibility. About 0.076 mg Fe (VI) dosage/mg tCODfed solubilized the sludge increasing the methane production by 40% compared to the untreated digester. The potential benefits of ferrate pretreatment of P&P primary sludge include resin acids oxidation and subsequent toxicity reduction, higher sludge solubilization enhancing methane production and enabling anaerobic digestion at higher COD loading.

Reactivity of nitrogen species with inorganic and organic compounds in water.

Many studies on the reactive nitrogen species (RNS, ●NO2, ●NO and ●NH2) with pollutants in water have been performed to understand the abatement of inorganic and organic compounds by these species, and the mechanisms of the formation of oxidative transformation products, especially nitrogenous oxidized byproducts. In this review, approaches to generate RNS in aqueous solution is first presented, followed by a summary of their reactivity with a wide range of compounds. The second-order rate constants (k, M-1 s-1) for the reactivity of ●NO2 and ●NO with a wide range of inorganic radical and nonradical species were correlated with thermodynamic one-electron oxidation potentials (E0). The positive correlation between log(k) versus E0 suggests one-electron transfer reactions. The Hammett-type correlations were developed for the reactions of ●NO2 and ●NH2 with organic compounds, using the unsubstituted benzene as a reference molecule (i.e., Σσo,p,m = 0) to calculate Σσo,p,m = σo + σp + σm for each organic molecule. Linear negative correlations of log(k) with Σσo,p,m were obtained for both ●NO2 and ●NH2, suggesting electrophilic substitution mechanism. The correlations presented herein may assist in eliminating organic micropollutants in water treatment and reuse processes.

Overlooked environmental risks deriving from aqueous transformation of bisphenol alternatives: Integration of chemical and toxicological insights.

Owing to the widespread prevalence and ecotoxicity of bisphenol alternatives such as bisphenol S, bisphenol F, and bisphenol AF, the past decade has witnessed the publication of a remarkable number of studies related to their transformation and remediation in natural waters. However, the reactivity, removal efficiency, transformation products (TPs), and mechanisms of such emerging pollutants by different treatment processes have not been well elucidated. Particularly, the transformation-driven environmental risks have been mostly overlooked. Therefore, we present a review to address these issues from chemical and toxicological viewpoints. Four degradation systems can be largely classified as catalytic persulfate (PS) oxidation, non-catalytic oxidation, photolysis and photocatalysis, and biodegradation. It was found that bisphenol alternatives possess distinct reactivities with different oxidizing species, with the highest performance for hydroxyl radicals. All systems exhibit superior elimination efficiency for these compounds. The inadequate mineralization suggests the formation of recalcitrant TPs, from which the overall reaction pathways are proposed. The combined experimental and in silico analysis indicates that many TPs have developmental toxicity, endocrine-disrupting effects, and genotoxicity. Notably, catalytic PS systems and non-catalytic oxidation result in the formation of coupling products as well as halogenated TPs with higher acute and chronic toxicity and lower biodegradability than the parent compounds. In contrast, photolysis and photocatalysis generate hydroxylated and bond-cleavage TPs with less toxicity. Overall, this review highlights the secondary environmental risks from the transformation of bisphenol alternatives by conventional and emerging treatment processes. Finally, future perspectives are recommended to address the knowledge gaps of these contaminants in aquatic ecosystems.

Combined sewer overflow treatment: Assessing chemical pre-treatment and microsieve-based filtration in enhancing the performance of UV disinfection.

Disinfection of combined sewer overflow (CSO) is necessary to reduce the amount of microorganisms discharged into surface waters. In this study, an efficient and cost-competitive treatment for CSO, employing UV disinfection, was developed. High suspended solids content in CSO poses a significant challenge for UV disinfection so laboratory experiments were carried out to asses the effect of chemical pre-treatment followed by micro-sieve filtration on the reduction of total suspended solids (TSS) and the increase of UV transmittance (UVT). The efficiency of UV, with and without pre-treatment, was investigated and a microbial inactivation model was developed to describe the fecal coliforms (FC) inactivation kinetics. Finally, the environmental impacts of the proposed treatment were simulated at the large-scale by stormwater management model (SWMM), and the cost of the proposed treatment train was evaluated and compared with current CSO treatment strategies. Experimental results showed that UV alone achieved 3.6-log reduction of FC at a UV fluence of 80 mJ/cm2, while a 4-log reduction of FC was achieved at a much lower UV fluence of 10 mJ/cm2, when the UV disinfection was preceded by chemical pre-treatment and microsieving filtration using a 32 µm mesh. Under these conditions, the TSS removal achieved was 73%, and the UVT increased from 14% to 32%.The SWMM showed that the proposed CSO treatment achieved a reduction in TSS by one order of magnitude and a decrease in number of FC from 1.05 × 1014 to 1.24 × 1010 CFU. The cost analysis performed herein suggests that the proposed treatment train is competitive to current CSO treatment strategies in terms of cost-effectiveness. The study demonstrates the potential of the innovative CSO treatment scheme to quickly and effectively treat a large amount of wastewater flow thus providing municipalities with a low footprint treatment unit for CSO.

Reactive High-Valent Iron Intermediates in Enhancing Treatment of Water by Ferrate.

Efforts are being made to tune the reactivity of the tetraoxy anion of iron in the +6 oxidation state (FeVIO42-), commonly called ferrate, to further enhance its applications in various environmental fields. This review critically examines the strategies to generate highly reactive high-valent iron intermediates, FeVO43- (FeV) and FeIVO44- or FeIVO32- (FeIV) species, from FeVIO42-, for the treatment of polluted water with greater efficiency. Approaches to produce FeV and FeIV species from FeVIO42- include additions of acid (e.g., HCl), metal ions (e.g., Fe(III)), and reductants (R). Details on applying various inorganic reductants (R) to generate FeV and FeIV from FeVIO42- via initial single electron-transfer (SET) and oxygen-atom transfer (OAT) to oxidize recalcitrant pollutants are presented. The common constituents of urine (e.g., carbonate, ammonia, and creatinine) and different solids (e.g., silica and hydrochar) were found to accelerate the oxidation of pharmaceuticals by FeVIO42-, with potential mechanisms provided. The challenges of providing direct evidence of the formation of FeV/FeIV species are discussed. Kinetic modeling and density functional theory (DFT) calculations provide opportunities to distinguish between the two intermediates (i.e., FeIV and FeV) in order to enhance oxidation reactions utilizing FeVIO42-. Further mechanistic elucidation of activated ferrate systems is vital to achieve high efficiency in oxidizing emerging pollutants in various aqueous streams.

Simultaneous inactivation of multidrug-resistant Escherichia coli and enterococci by peracetic acid in urban wastewater: Exposure-based kinetics and comparison with chlorine.

The presence of antibiotic resistance in wastewater sparked a great interest in investigating the inactivation of antibiotic-resistant bacteria by disinfecting agents. In this study, the inactivation kinetics of multidrug-resistant E. coli and enterococci by an emerging environmentally-friendly disinfectant, peracetic acid (PAA), in wastewater and phosphate buffer at pH 6.5 and pH 7.5, were characterized. It was demonstrated that the inactivation of the studied multidrug-resistant bacteria was governed by their exposure to PAA, i.e., integral of the PAA concentration over time (integral CT or ICT). Both regimes of the PAA inactivation of bacteria, i.e., initial resistance followed by a faster inactivation, were described well by an ICT-based Chick-Watson inactivation kinetic model. In wastewater at pH 7.5, the model-predicted ICT requirements showed that the multidrug-resistant enterococci were less susceptible to PAA than E. coli, e.g., to achieve a 3-log reduction, an ICT of 32.7 mg min/L and 23.4 mg min/L was needed, respectively. No regrowth of the studied bacteria was observed after 72 h from PAA disinfection at 25 ± 1 °C. Soluble constituents of wastewater decreased the PAA inactivation of both multidrug-resistant bacteria, i.e., higher inactivation was observed in phosphate buffer than wastewater at the same pH of 7.5. In phosphate buffer, a lower pH of 6.5 resulted in higher inactivation of multidrug-resistant E. coli compared with pH 7.5, but it did not affect the PAA inactivation of multidrug-resistant enterococci. A comparison with the most commonly used chemical disinfectant, chlorine, showed higher inactivation of both multidrug-resistant bacteria by chlorine and higher chlorine decay than PAA. The results of the present study may have implications in designing a PAA disinfection process, aiming at controlling antibiotic resistance, in terms of selecting a suitable fecal indicator and optimizing disinfectant dosing.

Peracetic Acid-Ruthenium(III) Oxidation Process for the Degradation of Micropollutants in Water.

This paper presents an advanced oxidation process (AOP) of peracetic acid (PAA) and ruthenium(III) (Ru(III)) to oxidize micropollutants in water. Studies of PAA-Ru(III) oxidation of sulfamethoxazole (SMX), a sulfonamide antibiotic, in 0.5-20.0 mM phosphate solution at different pH values (5.0-9.0) showed an optimum pH of 7.0 with a complete transformation of SMX in 2.0 min. At pH 7.0, other metal ions (i.e., Fe(II), Fe(III), Mn(II), Mn(III), Co(II), Cu(II), and Ni(II)) in 10 mM phosphate could activate PAA to oxidize SMX only up to 20%. The PAA-Ru(III) oxidation process was also unaffected by the presence of chloride and carbonate ions in solution. Electron paramagnetic resonance (EPR) measurements and quenching experiments showed the dominant involvement of the acetyl(per)oxyl radicals (i.e., CH3C(O)O• and CH3C(O)OO•) for degrading SMX in the PAA-Ru(III) oxidation process. The transformation pathways of SMX by PAA-Ru(III) were proposed based on the identified intermediates. Tests with other pharmaceuticals demonstrated that the PAA-Ru(III) oxidation system could remove efficiently a wide range of pharmaceuticals (9 compounds) in the presence of phosphate ions in 2.0 min at neutral pH. The knowledge gained herein on the effective role of Ru(III) to activate PAA to oxidize micropollutants may aid in developing Ru(III)-containing catalysts for PAA-based AOPs.

Performic Acid Disinfection of Municipal Secondary Effluent Wastewater: Inactivation of Murine Norovirus, Fecal Coliforms, and Enterococci.

Performic acid (PFA) is an emerging disinfectant to inactivate bacterial and viral microorganisms in wastewater. In this study, the inactivation kinetics of murine norovirus (MNV) by PFA, in phosphate buffer and municipal secondary effluent wastewater, are reported for the first time. PFA decay followed first-order kinetics and the inactivation of MNV was governed by the exposure of microorganisms to PFA, i.e., the integral of the PFA concentration over time (integral CT or ICT). The extension of the Chick-Watson model, in the ICT domain, described well the reduction of MNV by PFA, with determined ICT-based inactivation rate constants, kd, of 1.024 ± 0.038 L/(mg·min) and 0.482 ± 0.022 L/(mg·min) in phosphate buffer and wastewater, respectively, at pH 7.2. Furthermore, the simultaneous PFA inactivation of MNV and fecal indicators indigenously present in wastewater such as fecal coliforms and enterococci showed that 1-log reduction could be achieved with ICT of 2, 1.5, and 3.5 mg·min/L, respectively. When compared with the most commonly used peracid disinfectant of municipal wastewater, peracetic acid (PAA), the ICT requirements determined using the fitted ICT-based kinetic models were ∼20 times higher for PAA than PFA, indicating a much stronger inactivation power of the PFA molecule.

Inactivation of Murine Norovirus and Fecal Coliforms by Ferrate(VI) in Secondary Effluent Wastewater.

Ferrate(VI) (FeVIO42, Fe(VI)) is an emerging oxidant/disinfectant to treat a wide range of contaminants and microbial pollutants in wastewater. This study describes the inactivation of murine norovirus (MNV) by Fe(VI) in phosphate buffer (PB) and secondary effluent wastewater (SEW). The decay of Fe(VI) had second-order kinetics in PB while Fe(VI) underwent an initial demand followed by first-order decay kinetics in SEW. The Chick-Watson inactivation kinetic model, based on integral CT (ICT) dose, well fitted the inactivation of MNV in both PB and SEW. In PB, the values of the inactivation rate constant (kd) decreased with an increase in pH, which was related to the reaction of protonated Fe(VI) species (HFeO4-) with MNV. Higher kd was observed in SEW than in PB. The inactivation of indigenous fecal coliforms (FC) in SEW was also measured. A two-population double-exponential model that accounted for both dispersed and particle-associated FC well fitted the inactivation data with determined kd and particle-associated inactivation rate constant (kp). Results show that Fe(VI) was more effective in inactivating dispersed FC than MNV. The MNV inactivation results obtained herein, coupled with the detailed modeling, provide important information in designing an Fe(VI) wastewater disinfection process.

Inactivation kinetics of antibiotic resistant Escherichia coli in secondary wastewater effluents by peracetic and performic acids.

While disinfection processes have been central for public health protection, new concerns have been raised with respect to their ability to control the spread of antibiotic resistance in the environment. In this study, we report the inactivation kinetics by peracetic and performic acids of a typical indicator, Escherichia coli and its corresponding antibiotic-resistant subpopulation, in secondary settled wastewater effluent. Performic acid always showed greater inactivation efficiency than peracetic acid, whether or not the indicator was Ampicillin-resistant. Observed inactivation data, fitted with an exposure-based inactivation model, predicted very well the inactivation profile of both total and ampicillin resistant Escherichia coli. Notably, the antibiotic resistance percentage decreased significantly in treated wastewater compared to untreated wastewater thus making the peracid-based disinfection processes beneficial in controlling antibiotic resistance in secondary settled wastewater. Moreover, the minimum inhibitory concentration values remained unchanged. Finally, antibiotic-resistant-specific inactivation kinetics were used to predict the disinfection efficiency in continuous-flow reactors under ideal and non-ideal hydraulics thus providing useful information for future design and operation of disinfection process in antibiotic-resistance controlling mode.

Rapid removal of acesulfame potassium by acid-activated ferrate(VI) under mild alkaline conditions.

Acesulfame potassium (ACE) is a widely used artificial sweetener that has consistently been detected in wastewater and surface waters. The high-valent iron-based green oxidant known as ferrate(VI) (potassium ferrate(VI); Fe(VI)) had low reactivity with ACE (i.e. 4 h (or 240 min) contact time removed only ∼ 67% ACE) at a molar ratio of 6.0 ([Fe(VI)]:[ACE]). Comparatively, it took 60 s (or 1 min) to remove ∼94% ACE when HCl (786 µM) was added to a mixture of Fe(VI)-ACE at the same molar ratio of 6.0 (or acid-activated Fe(VI)). Significantly, the final pH (i.e. 7.6-8.1) was similar for Fe(VI) and acid-activated Fe(VI). An empirical model using response surface methodology was developed that could describe reasonably well the removal efficiency of ACE. Inorganic constituents of wastewater (Cl-, Na+, Ca2+, and Mg2+) had no significant effect on the oxidation of ACE by acid-activated Fe(VI). The degradation efficiency of ACE decreased in the presence of 10 mg/L of natural organic matter (NOM) but remained unchanged at 5 mg NOM/L. Sulfamic acid as the oxidized product of ACE was identified by liquid chromatography high resolution mass spectrometry method. Reaction pathways include ring opening of ACE through hydrolytic transformation. Acid-activated Fe(VI) has advantage of rapid removal of ACE under mild alkaline conditions of wastewater treatment plants compared to other oxidation processes such as chlorination, ozonation, and light-based processes.

Detailed modeling and advanced control for chemical disinfection of secondary effluent wastewater by peracetic acid.

Advanced control of chemical disinfection processes is becoming increasingly important in view of balancing under-treatment (low pathogen inactivation) and over-treatment (excessive consumption of disinfectant and disinfection byproducts formation) thereby providing considerable environmental and economic benefits. Conventional control strategies such as flow pacing or residual trim ignore chemical demand/decay, inactivation kinetics, and other factors governing disinfection performance in continuous-flow reactors such as reactor hydraulics and process variability. This study presents the development, verification, and pilot-scale validation of a novel CT-based real-time disinfection control strategy, derived from first principles, and applied to peracetic acid disinfection of municipal secondary effluent wastewater. Validation experiments were carried out using a 3-m3 pilot contact basin of which the hydraulic performance was first characterized by means of tracer tests and then mathematically modeled using the well-established theoretical framework of continuous stirred-tank reactors in series. The analytical model describing hydraulic performance was subsequently extended to take into account disinfectant demand/decay and microbial inactivation kinetics. The integrated model was successfully used to predict, and control, residual peracetic acid as well as microbial concentration in the pilot effluent. Validation studies conclusively supported that the novel CT-based control strategy was superior in maintaining constant disinfection performance, desired microbial counts, and low residual disinfectant under variable flow and wastewater quality. When compared with flow pacing, the CT-based control required two times less the amount of chemical for the same treatment objective (<100 cfu/100 mL). Remarkably, the CT-based control strategy could be extended to other chemical disinfection processes such as chlorination and ozonation, alone or in combination with physical treatment technologies such as membranes and ultraviolet irradiation.

Pharmaceuticals and pesticides in secondary effluent wastewater: Identification and enhanced removal by acid-activated ferrate(VI).

The emergence of resistance to antibacterial drugs and pesticides in water is unprecedented. This may have adverse consequences to human health and ecological systems. This paper first sought the identification of a wide range of pharmaceuticals and pesticides in two secondary effluent wastewaters (SEW) of different quality characteristics, followed by their removal by ferrate(VI) (Fe(VI), FeO42-). Screening for 22 pharmaceuticals and 32 pesticides, revealed that 11 pharmaceuticals and 3 pesticides in SEW of plant A, and 14 pharmaceuticals and 5 pesticides in SEW of plant B were present at concentrations higher than the liquid chromatography mass spectrometry method quantitation limit. The concentrations of pharmaceuticals and pesticides ranged from 0.15 ng/L-413.03 ng/L. Investigation of the removal of these pharmaceuticals and pesticides by Fe(VI) showed that some had recalcitrant activity towards their oxidation. Acid-activated Fe(VI) resulted in enhanced oxidation (12.6%-56.2% degradation efficiency) of 6 and 7 pharmaceuticals in SEW of plant A and plant B, respectively, at a shorter time than Fe(VI) without activation (i.e. 3-5 min versus 15-30 min). The degradation of 1 and 3 pesticides in SEW of plant A and plant B respectively, has also been enhanced by activating Fe(VI) (13.8%-86.2% degradation efficiency). Results on testing of organic matter characterization of treated SEW with and without acid-activated Fe(VI) treatment are also presented. Acid-activated Fe(VI) treatment has potential in enhancing the removal of micropollutants in real wastewater.