Real Drinking Water Research Articles

A dansyl-based fluorescent probe for sensing Cu2+ in aqueous solution

A fluorescent probe based on a glycyl-L-tyrosine-modified dansyl derivative (D-GT) is designed and synthesized. D-GT demonstrated great detection performance toward Cu2+ in an aqueous solution. Fluorescence quenching occurred due to the coordination of Cu2+ with D-GT. The sensitive detection of D-GT to Cu2+ was applied in aqueous solution within a wide pH span (6–12). A 1:1 coordinate stoichiometric way and an association constant of 6.47 × 104 M−1 between D-GT and Cu2+ were determined. The measured detection limit for Cu2+ in HEPES buffer solution (10 mM, pH 7.4) was 0.69 μM. The probe displayed an appropriate sensitivity toward Cu2+ in real drinking water samples and living cells, which reveals the potential applications of D-GT in complicated environments.

Synergistic effect of sulfidated nano zerovalent iron and persulfate on inactivating antibiotic resistant bacteria and antibiotic resistance genes

Antimicrobial resistance continues to be a rising global threat to public health. It is well recognized that wastewater treatment plants are reservoirs of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). However, traditional disinfection techniques are not effective to simultaneously remove ARB and ARGs, and the dynamic analysis of ARB inactivation have also been deficient. In this study, sulfidated nano zerovalent iron (S-nZVI) coupled with persulfate (PS) was applied to simultaneously remove both ARB (E. coli K-12 with RP4 plasmid) and ARGs (extra- and intracellular ARGs). S-nZVI/PS completely inactivated ARB (~7.8-log reduction) within 10 min and degraded all extracellular ARGs (~8.0-log reduction) within 5 min. These efficiencies were significantly higher (decay rate constant, k = 0.138 min−1) than those achieved individually (S-nZVI: k = 0.076 min−1; PS: k = 0.008 min−1), implying a synergistic effect between S-nZVI and PS against ARB and ARGs. The efficient removal rate of ARB was also supported by confocal microscopy and microfluidics at a single-cell level. The complete inactivation of ARB by S-nZVI/PS was also demonstrated in real drinking water and real wastewater effluent that contained natural organic matter and suspended solids. Regrowth assays showed that the treated ARB was not observed after 72 h or longer incubation, suggesting that ARB was permanently inactivated by radicals such as SO4•- and •OH. The destruction of bacterial cells compromised the removal efficiency of the intracellular ARGs, with only ~4.0-log reduction after 60 min treatment by S-nZVI/PS. Collectively, our results suggest the feasibility of S-nZVI coupled with PS for simultaneous ARB and ARGs removal in real water matrices.

Modeling of residual chlorine in a drinking water network in times of pandemic of the SARS-CoV-2 (COVID-19)

Due to the outbreak of the novel coronavirus disease there is a need for public water supply of the highest quality. Adequate levels of chlorine allow immediate elimination of harmful bacteria and viruses and provide a protective residual throughout the drinking water distribution network (DWDN). Therefore, a residual chlorine decay model was developed to predict chlorine levels in a real drinking water distribution network. The model allowed determining human exposure to drinking water with a deficit of residual chlorine, considering that it is currently necessary for the population to have clean water to combat coronavirus Covid 19. The chlorine bulk decay rates (kb) and the reaction constant of chlorine with the pipe wall (kw) were experimentally determined. Average kb and kw values of 3.7 d− 1 and 0.066 m d− 1 were obtained, respectively. The values of kb and kw were used in EPANET to simulate the chlorine concentrations in a DWDN. The residual chlorine concentrations simulated by the properly calibrated and validated model were notably close to the actual concentrations measured at different points of the DWDN. The results showed that maintaining a chlorine concentration of 0.87 mg L− 1 in the distribution tank, the residual chlorine values in the nodes complied with the Ecuadorian standard (0.3 mg L− 1); meanwhile, about 45% of the nodes did not comply with what is recommended by the WHO as a mechanism to combat the current pandemic (0.5 mg L− 1). This study demonstrated that residual chlorine modeling is a valuable tool for monitoring water quality in the distribution network, allowing to control residual chlorine levels in this pandemic season.

Laccase and horseradish peroxidase for green treatment of phenolic micropollutants in real drinking water and wastewater.

Biologically active micropollutants that contain diverse phenolic/aromatic structures are regularly present in wastewater effluents and are even found in drinking water. Advanced green technologies utilizing immobilized laccase and/or peroxidase, which target these micropollutants directly, may provide a reasonable alternative to standard treatments. Nevertheless, the use of these enzymes is associated with several issues that may prevent their application, such as the low activity of laccase at neutral and basic pH or the necessity of hydrogen peroxide addition as a co-substrate for peroxidases. In this study, the activity of laccase from Trametes versicolor and horseradish peroxidase was evaluated across a range of commonly used substrates (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), syringaldazine, and guaiacol). Moreover, conditions for their optimal performance were explored along with an assessment of whether these conditions accurately reflect the effectivity of both enzymes in the degradation of a mixture of bisphenol A, 17α-ethinylestradiol, triclosan, and diclofenac in tap drinking water and secondary wastewater effluent. Laccase and horseradish peroxidase showed optimal activity at strongly acidic pH if ABTS was used as a substrate. Correspondingly, the activities of both enzymes detected using ABTS in real waters were significantly enhanced by adding approximately 2.5% (v/v) of McIlvaine's buffer. Degradation of a mixture of micropollutants in wastewater with 2.5% McIlvaine's buffer (pH 7) resulted in a substantial decrease in estrogenic activity. Low degradation efficiency of micropollutants by laccase was observed in pure McIlvaine's buffer of pH 3 and 7, compared with efficient degradation in tap water of pH 7.5 without buffer. This study clearly shows that enzyme activity needs to be evaluated on micropollutants in real waters as the assessment of optimal conditions based on commonly used substrates in pure buffer or deionized water can be misleading.

Removal of antibiotics in sand, GAC, GAC sandwich and anthracite/sand biofiltration systems

Drinking water biofiltration offers the possibility of the removal of trace level micropollutants from source water. Sand, granular activated carbon (GAC), GAC sandwich (a layer of GAC loaded in the middle of sand bed), and anthracite-sand dual biofilters were set-up in duplicate at bench-scale to mimic the filtration process in real drinking water treatment works. During the 3-month system operation, removal of five antibiotics (amoxicillin, clarithromycin, oxytetracycline, sulfamethoxazole, and trimethoprim) and overall biofilter performance were evaluated. Natural surface water spiked with a mixture of the target antibiotics was used as feedwater to the biofilters. Results showed that the target antibiotics were substantially removed (>90%) by GAC-associated biofilters and partially removed (≤20%) by sand alone and anthracite-sand biofilters. In particular, the GAC sandwich biofilter exhibited superior performance compared to sand/anthracite biofilter, and the comparisons among all biofilters indicated that both adsorption and biodegradation contributed to the removal of the target antibiotics in the GAC-associated biofilters. Adsorption kinetics showed that sulfamethoxazole fitted with pseudo-first-order adsorption model, while trimethoprim, amoxicillin, oxytetracycline and clarithromycin fitted the pseudo-second-order model. All antibiotics fitted the Langmuir model according to the isotherm experiment. To date, this is the first study evaluating the removal of antibiotics by GAC sandwich biofilters. Overall, this research will provide useful information which can be used for optimising or updating existing biofiltration processes in industry to reduce antibiotic residues from source water.

Colorimetric detection of Hg(II) by γ-aminobutyric acid-silver nanoparticles in water and the assessment of antibacterial activities

In this work, we report the synthesis of silver nanoparticles (AgNPs) via a wet-chemical reduction procedure using citrate (Cit) and γ-aminobutyric acid (GABA) as stabilizers. The formation of GABA-Cit@AgNPs was confirmed by UV–vis spectroscopy with a surface plasmon resonance band at 393 nm clearly confirming the formation of silver nanoparticles. AgNPs were characterized using UV–vis spectroscopy, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential. The as-prepared AgNPs can be used for the detection of hazardous mercury ions (Hg2+) in water by colorimetric method with a limit of detection (LOD) and limit of quantitation (LOQ) of 2.37 μM and 3.99 μM, respectively. The linear working range for Hg2+ detection is 5–35 μM and the sensor probe was applied to investigate Hg2+ in real drinking water samples with satisfied results. Rapid response to Hg2+ is also observed when the nanoparticles are composited within hydrogels. Moreover, GABA-Cit@AgNPs shows antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The fast and sensitive response of the proposed Hg2+ sensor, together with its antibacterial activities, makes GABA-Cit@AgNPs potentially applicable for the development of cheap, portable, colorimetric sensors in fieldwork.

Effects of residual disinfectants on the redox speciation of lead(ii)/(iv) minerals in drinking water distribution systems.

This study investigated the reaction kinetics on the oxidative transformation of lead(ii) minerals by free chlorine (HOCl) and free bromine (HOBr) in drinking water distribution systems. According to chemical equilibrium predictions, lead(ii) carbonate minerals, cerussite PbCO3(s) and hydrocerussite Pb3(CO3)2(OH)2(s), and lead(ii) phosphate mineral, chloropyromorphite Pb5(PO4)3Cl(s) are formed in drinking water distribution systems in the absence and presence of phosphate, respectively. X-ray absorption near edge spectroscopy (XANES) data showed that at pH 7 and a 10 mM alkalinity, the majority of cerussite and hydrocerussite was oxidized to lead(iv) mineral PbO2(s) within 120 minutes of reaction with chlorine (3 : 1 Cl2 : Pb(ii) molar ratio). In contrast, very little oxidation of chloropyromorphite occurred. Under similar conditions, oxidation of lead(ii) carbonate and phosphate minerals by HOBr exhibited a reaction kinetics that was orders of magnitude faster than by HOCl. Their end oxidation products were identified as mainly plattnerite β-PbO2(s) and trace amounts of scrutinyite α-PbO2(s) based on X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. A kinetic model was established based on the solid-phase experimental data. The model predicted that in real drinking water distribution systems, it takes 0.6-1.2 years to completely oxidize Pb(ii) minerals in the surface layer of corrosion scales to PbO2(s) by HOCl without phosphate, but only 0.1-0.2 years in the presence of bromide (Br-) due the catalytic effects of HOBr generation. The model also predicts that the addition of phosphate will significantly inhibit Pb(ii) mineral oxidation by HOCl, but only be modestly effective in the presence of Br-. This study provides insightful understanding on the effect of residual disinfectant on the oxidation of lead corrosion scales and strategies to prevent lead release from drinking water distribution systems.

Achieving drinking water compliance levels for metaldehyde with an acclimated sand bioreactor

Metaldehyde removal was delivered to below the 0.1 μg L−1 regulatory concentration in a laboratory scale continuous upflow fluidised sand bioreactor that had undergone acclimation through selective enrichment for metaldehyde degradation. This is the first reported case of successful continuous flow biological treatment of metaldehyde from real drinking water sources treating environmentally realistic metaldehyde concentrations. The impact of the acclimation process was impermanent, with the duration of effective treatment directly related to the elevated concentration of metaldehyde used during the enrichment process. The efficacy of the approach was demonstrated in continuous flow columns at both laboratory and pilot scale enabling degradation rates of between 0.1 and 0.2 mg L−1 h−1. Future work needs to focus on optimisation of the sand bioreactor and the acclimation process to ensure viability and feasibility of the approach at full scale.

A dual-responsive and highly sensitive fluorescent probe for Cu2+ and pH based on a dansyl derivative

Herein, a dansyl-based fluorescent probe bearing a glycylglycine group (GG-Dns) is reported. The probe demonstrates suitable selectivity and sensitivity towards Cu2+ in aqueous media over a wide pH range (6–13) through a fluorescence “turn-off” mechanism. The determined detection limit is 0.29 μM (Cu2+ concentration), and the association constant is 3.09 × 104 M−1, with 1:1 coordinate stoichiometric ratio. The probe displays an appropriate detection performance for Cu2+ in real drinking water samples, indicating the potential applicability of GG-Dns even in complex environments. Furthermore, in aqueous environments with pH below 6, GG-Dns is sensitive toward pH changes within a narrow range and with a fluorescence “on-off” function. The sensitive detection characteristics of Cu2+ can be ascribed to the coordination performance of GG moiety to Cu2+, whereas pH responsiveness is ascribed to the protonation of Dns moiety's dimethylamine group.

Inkjet Printed Multi-Walled Carbon Nanotube Sensor for the Detection of Lead in Drinking Water

The heavy metal lead has been a pollutant in our environment for many centuries and at low concentrations, lead can damage the human central nervous system, liver, kidney, and cardiovascular system and cause physiological and neurological problems in developing children who are most susceptible to lead poisoning. Lead in drinking water is currently regulated in the United States by the Environmental Protection Agency (EPA) with a maximum contamination level (MCL) of 15 ppb and the World Health Organization (WHO) has a MCL of 10 ppb of lead. Researches have identified high levels of lead in drinking water samples across the globe and the neurological development of young children is of great concern. A need for a rapid, sensitive, selective, reproducible, and affordable sensor for the trace detection of lead in true drinking water samples is needed. The detection of Pb2+ was performed using an inkjet printed multi-walled carbon nanotube (IJP-MW-CNT) electrode employing Osteryoung square wave stripping voltammetry (OSWV) as the detection method. The MW-CNT ink was prepared in water using bile salts (BS) as a surfactant, which were washed out extensively with DI water before using the printed MW-CNTs as electrodes. The IJP-MW-CNT electrode was used as the working electrode with a platinum wire and glass capillary Ag/AgCl as auxiliary and reference electrode, respectively. The electrodes performance was optimized in 0.1 M acetate buffer (pH = 4.3) and had a linear range of 5 – 50 ppb (R2 = 0.98235) a sensitivity of 20.15 nA/ppb and a limit of detection (LOD) of 1.632 ppb for Pb2+. The analytical applicability of electrode was tested in a real drinking water sample (i.e.) Cincinnati tap water with a linear range of 15 – 70 ppb (R2 = 0.98752) a sensitivity of 2.654 nA/ppb and a LOD of 1.269 ppb for Pb2+. The IJP-MW-CNT electrode’s results are comparable between different electrodes, and reproducible using the same electrode multiple times. The electrode can be easily and quickly be fabricated without modifications or in-situ additives needed, which makes up-scale production a feasible option. The sensor has been shown to perform well in an environmental sample (Cincinnati tap water) without any sample preparation or changes.The IJP-MW-CNT electrode can be implemented for the affordable and rapid detection of lead on-site in true water samples.

A method for highly sensitive detection of silver nanoparticles using a micro-resonator and DNA assisted conjugation

Silver nanoparticles (AgNPs) have garnered significant interest owing to their unique properties and therefore, AgNPs have widespread application. However, there have been recent reports about the risks posed by AgNPs to human health and a highly sensitive tool for detecting AgNPs in aquatic environments is required to prevent their harmful effects on humans. In this article, we propose highly sensitive detection of AgNPs using a micro-resonator and the DNA assisted conjugation method. The detection method is based on the resonance frequency shift of the resonator upon adsorption of conjugated AgNPs. We have used the DNA assisted AgNPs conjugation method to amplify the mass of the detection target. By using this micro-resonator in combination with the conjugation method, we were able to achieve highly sensitive and selective detection of AgNPs, with detection limits of approximately 10 ng/mL in distilled water, which is at least 10 times more sensitive than that described in previous reports. Further, we also performed detection in real drinking water samples.

Diclofenac removal from water by photocatalysis- assisted filtration using activated carbon modified with N-doped TiO2

The aim of this study was to develop powdered and granular activated carbon modified with N doped TiO2, namely PAC-TiO2N and respective, GAC-TiO2N by sol-gel method, starting from commercial activated carbon, for the removal from water of diclofenac (DCF), an emerging pollutant. The synthesized materials were characterized systematically and morphostructural, light absorption and electrical charge properties were determined. The sorption and photocatalytic capacities of both materials were determined by batch experiments based on the kinetic models and the effect of operational parameters. GAC-TiO2N was selected for further testing in fixed bed-column experiments envisaging its potential integration with real drinking water treatment technology. The GAC-TiO2N tested in UV irradiation-assisted fixed bed-column filtration for DCF removal exhibited a great potential for practical application, by testing in simulated coexisting DCF and humic acids (HAs) and real surface water spiked with DCF (Bega River, Timisoara city, Romania). About 80% removal efficiency was noticed for both DCF and HAs and about 70% of the organic matter was removed (expressed as total organic carbon- TOC indicator). UV irradiation during filtration allowed the activation of the GAC-TiO2N filtration layer without TiO2 loss, which led to longer life-times due to the potential “self-cleaning” effect and its good stability.

Nitrogen-rich covalent organic frameworks as solid-phase extraction adsorbents for separation and enrichment of four disinfection by-products in drinking water

Disinfection by-products (DBPs) in drinking water can pose a health risk to humans. In this work, a new nitrogen-rich covalent organic frameworks (TpTt-COFs) was synthesized and applied firstly as a novel solid-phase extraction (SPE) trapping media for four ultra-trace levels of DBPs in drinking water samples. Under the optimal conditions, these DBPs were absorbed on a SPE cartridge; then, the DBPs were eluted with the optimized volume of eluent. The concentrated elution was detected and quantified by gas chromatography-mass spectrometry. Low limits of detection (0.0004–0.0063 ng mL−1), wide linearity (0.002–50 µg L−1), good reproducibility (1.54–2.88%) and repeatability (1.28–3.40%) were obtained. This novel method has been successfully applied to the analysis of ultra-trace levels DBPs in real drinking water samples. These accurate experimental results by this method indicated that the novel TpTt-COFs as a SPE trapping material was an attractive option for efficient and effective analysis of ultra-trace levels DBPs in future.

Removing per‐ and polyfluoroalkyl substances from groundwaters using activated carbon and ion exchange resin packed columns

AbstractHuman exposure to per‐ and polyfluoroalkyl substances (PFAS) in drinking water is of growing concern as a result of increasing reports of occurrence and potential regulation. Adsorption of PFAS by granular activated carbon (GAC) or ion exchange (IX) resin is a suitable treatment technique. However, few studies compare PFAS removal in continuous flow GAC or IX adsorption systems using real drinking water sources. In this study, rapid small‐scale column tests (RSSCTs) were used to investigate the effects of PFAS type and chain length on adsorption by GAC and IX resin for six groundwaters used as drinking water supplies. Seven PFAS substances with chain lengths of C4–C9 were detected in the groundwaters with the sum of their concentrations (ΣPFAS) ranging from 156 to 7,044 ng/L. Adsorption capacities (qΣPFAS) were calculated to compare the removal capacity among different sorbents and qΣPFAS values ranged from 10.3 to 228 ng PFAS/mg sorbent after about 100,000 bed volumes treated. Coal‐based GACs had higher adsorption capacity compared with coconutshell‐based GAC, which was likely due to higher mesopore and macropore volumes. IX resins performed better than GAC in removing PFAS, but they were not effective in treating short‐chain perfluorocarboxylic acids (PFCAs). Perfluorosulfonic acids (PFSAs) broke through later than PFCAs with the same chain length. Within PFSA or PFCA classes, shorter‐chain PFAS species always broke through before longer‐chain PFAS. Statistical analysis demonstrated that PFAS with higher hydrophobicity and molecular weight are more amenable to GAC adsorption. Empirical models were developed and predicted PFAS breakthrough. By quantifying PFAS selectivity and removal efficiency, this work provides benchmark data for commercially available treatment technologies and guidance toward specific PFAS classes for which new treatment technologies may be most beneficial.

Rapid defluoridation of drinking water by calcium carbonate nanoadsorbent: characterization, adsorption studies and application to real samples’ treatment

Abstract Groundwater contamination of fluoride is a serious global issue leading to its excessive intake and subsequently numerous adverse health issues. This research was designed to assess the efficiency of nanoadsorbent for removal of fluoride levels from water. For this purpose, calcium carbonate nanoparticles (average particle size 14.6 nm) were prepared and later applied for effective removal of fluoride from simulated as well as real drinking water (DW) samples collected from different areas of Lahore, Pakistan. The particles were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and atomic force microscopy. Physico-chemical parameters were studied in batch mode which revealed high adsorption capacity (i.e. 754.36 mg g−1) at room temperature and neutral pH within 10 min. The kinetic isotherms (general, pseudo-first, and pseudo-second order), diffusion studies (intra-particle diffusion and particle diffusion models), and adsorption models (Langmuir, Freundlich, Liu, and Redlich–Peterson) were also applied to evaluate the suitability of adsorption process. The applicability of nanoadsorbent to fluoride-contaminated real DW samples led to 98–100% efficacy of defluoridation.

Cucumber peel bead biosorbent for multi-ion decontamination of drinking water collected from a mine region in New Zealand

ABSTRACT Cucumber peel as a bead was examined for its ability to remove heavy metals from drinking water. Deionised laboratory water was spiked with seven toxic ions namely, arsenic, cadmium, chromium, copper, mercury, lead and nickel at 0.1 mg L−1 and kinetic studies were performed over 72 h. Kinetic data were modelled using film diffusion, pore diffusion, Weber-Morris, pseudo-first-order, pseudo-second-order and Elovich equation. The bead surface was imaged before and after biosorption using scanning electron microscopy coupled with energy dispersive spectroscopy (EDS). Results indicated that different ions contained in a multi-ion solution were biosorbed by different mechanisms and at different rates. Equilibrium biosorption for Cd, Hg and Ni was ∼91, 90 and 67%, respectively, at 24 h. These ions diffused through the pores of the bead, as they were not identified by EDS, and their biosorption increased with an increase in temperature. The least biosorbed ions were As and Cr with ∼21 and 17% equilibrium biosorption, respectively. The removal of only Cu, Hg, Pb and Ni was pH-dependent. Cucumber peel beads removed all spiked ions from real drinking water collected near the Macraes gold mine in New Zealand, but the biosorption percentage was lower for Cd, Cu, Pb and Ni compared to spiked deionised laboratory water. The results of this study suggest that cucumber peel when immobilised on a sodium alginate bead can be used as a potential biosorbent for the removal of multiple toxic ions from drinking water and their use warrants further examination in contaminated drinking water.

Development of a Multiresidue Method for Endocrine-Disrupting Pesticides by Solid Phase Extraction and Determination by UHPLC-MS/MS from Drinking Water Samples.

A rapid and efficient method based on solid phase extraction and liquid chromatography-tandem mass spectrometry was validated, allowing the determination of the endocrine-disrupting herbicides (acetochlor, alachlor, amitrole and atrazine), fungicides (carbendazim, triadimefon, penconazole and propiconazole), and insecticides (carbaryl and carbofuran) in drinking water. Low method detection limits (0.01-0.64ng/L) and method quantification limits (0.03-2.13ng/L) were obtained with satisfactory recoveries and precision for the endocrine-disrupting pesticides. The method was applied for real drinking water samples collected in the area of the city of Hangzhou (Zhejiang, China); the results showed that carbendazim, atrazine and acetochlor were detected in the drinking water samples and acetochlor was the most detected analyte.

Comparative study of multiple thiol-based self-assembled monolayer coatings for the SERS detection of nitrite, nitrate, and perchlorate anions in water.

Raman-based sensors represent a promising solution to enable both detection and fingerprinting of anionic pollutants in the water distribution network. Due to the weak nature of Raman scattering, a signal intensity enhancement mechanism, such as surface enhanced Raman spectroscopy (SERS), is required. Given the combination of SERS being a first layer effect and the low affinity for metallic surfaces shown by anions, functionalization of the SERS substrates using positively charged self-assembled monolayers (SAMs) is required to guarantee a strong SERS signal. In this work, the performance of three thiol-based coatings, namely, 2-mercapto-4-methyl-pyrimidine, cysteamine, and 2-dimethyl-amino-ethanethiol, is systematically compared for the detection of nitrite, nitrate, and perchlorate ions in water. For each coating, the limit of detection of those analytes is studied in combination with commercial SERS substrates. Cysteamine-coated SERS substrates are shown to provide the lowest limit of detection for the three analytes of this study. Evaluation of this coating on real drinking water samples is reported.

Comparative cytotoxicity of halogenated aromatic DBPs and implications of the corresponding developed QSAR model to toxicity mechanisms of those DBPs: Binding interactions between aromatic DBPs and catalase play an important role

Halogenated aromatic disinfection byproducts (DBPs) are a new group of emerging DBPs identified recently. They have been detected in disinfected drinking water, wastewater effluents, recreational water and oil/gas produced water, at concentrations of ng/L to μg/L in general. Previously studies have demonstrated that most of them can induce developmental toxicity and growth inhibition in aquatic organisms based on in vivo bioassays. In this study, to further understand the adverse effects of aromatic DBPs to human health, the comparative cytotoxicity of 15 halogenated aromatic DBPs belonging to four subgroups (i.e., halophenols, halonitrophenols, halohydroxybenzaldehydes and halohydroxybenzoic acids) was evaluated with mammalian Chinese Hamster Ovary cells. The results indicated that the selected aromatic DBPs exhibited an in vitro toxicity rank order of halonitrophenols > halophenols > halohydroxybenzaldehydes > halohydroxybenzoic acids. The potential toxicity mechanisms involved with the antioxidant system were investigated by using molecular docking analysis between key antioxidant enzymes (i.e., catalase, superoxide dismutase, and glutathione S-transferase) and aromatic DBPs. Based on the observed cytotoxicity data and screening the candidate descriptors (including binding energies between the aromatic DBPs and key antioxidant enzymes as well as physical-chemical/quantum-chemical/topological descriptors), a QSAR model was developed as log (LC50) −1 = − 1.050ECAT + 0.300EHOMO − 0.238ELUMO− 0.164, indicating the importance of the interactions of aromatic DBPs towards catalase and the electrophilic/nucleophilic reactivity of aromatic DBPs in the toxicity mechanisms. In addition, the occurrence of the aromatic DBPs in tap water and finished water was studied in a mega city Shenzhen located in South China. Results showed that halogenated aromatic DBPs commonly existed in Shenzhen drinking water at ng/L levels, and three nitrogenous aromatic DBPs were detected in real drinking water for the first time. The major toxicity drivers among the target aromatic DBPs were identified through the integration of the measured concentrations and observed cytotoxicity; notably, DBPs with the highest concentrations may not contribute the highest proportions of overall toxicity.

Quality Fuzzy Predictive Control of Water in Drinking Water Systems

With the big demand on water supply during the last century due to population growth, the approbation of new technology to assure water quality at lower cost is essential. This paper presents a drinking water distribution system (DWDS) based on a nonlinear fuzzy modeling technique. The approach uses a multi-input multi-output (MIMO) Takagi–Sugeno (T–S) fuzzy model, which is relevant for constructing a large class of nonlinear processes. The proposed framework is validated on a real drinking water distribution system, the MIMO fuzzy T–S model was implemented, in the context of nonlinear predictive control to regulate the water quality (the chlorine concentration in drinking water). The objective is to keep the system outputs within upper and lower limits from the requirement of health regulations.