Wastewater Samples Research Articles

Development of a new synchronous fluorescence spectrometry combined with Al3+ sensitized for simultaneous and rapid determination of trace flumequine, ciprofloxacin and doxycycline hydrochloride residues in wastewater

Antibiotics are a new type of environmental pollutants. Due to its wide application in many fields, antibiotic residues are ubiquitous in the wastewater environments. Given their potential threat on water ecosystem functioning and public health, the detection of antibiotic residues in wastewater environments has become very necessary. Based on the complexation of Al3+ with flumequine (FLU), ciprofloxacin (CIP) and doxycycline hydrochloride (DOX), their molecular conjugated area were increased and fluorescence intensity were enhanced, combined with synchronous fluorescence spectrometry (SFS) had good selectivity and high sensitivity, a novel method of Al3+ sensitized synchronous fluorescence spectrometry for the determination of FLU, CIP and DOX residues in wastewater was established. When the wavelength difference (Δλ) was selected 115.0 nm, synchronous fluorescence spectra of the three antibiotics could be well separated and the interference of wastewater matrix were eliminated primely. The new SFS made good use of spectral separation instead of conventional chemical separation, and the actual wastewater sample could be directly determined after simple filtration. The experiment results showed that the concentrations of FLU, CIP and DOX in the range of 0.5000–800.0 ng·mL-1, 0.5000–640.0 ng·mL-1 and 10.00–3500 ng·mL-1 had a good linear relationship with fluorescence intensity. The detection limits of three antibiotics were 0.02054 ng·mL-1, 0.03956 ng·mL-1 and 0.8524 ng·mL-1, respectively. Recovery rates of three antibiotics in wastewater samples were 90.72%-98.23%, 88.68%-95.08% and 85.94%-96.70%. The new SFS established in this experiment had the advantages of simple, rapid, sensitive, accurate and good selectivity. Simultaneous and rapid detection of FLU, CIP and DOX residues in wastewater was successfully realized. It had good application prospects in real-time water quality monitoring.

Electrochemical sensor based on Y-shaped DNA by “one-pot” method for mercury detection

A DNA electrochemical sensor based on Y-shaped DNA probes was successfully designed for Hg2+ detection. The sensor was modified with carbon self-doping graphite-like carbon nitride (C-g-C3N4) and electrodeposited gold nanoparticles (EAu) to enhance conductivity and enrich the binding sites for DNA. DNA probe (S1) binded on the modified electrode via –SH, forming a stable Y-shaped DNA double helix structure with probe S2 and probe S3 anchoring on gold nanoparticles (nanoAu) in the presence of Hg2+ solution. The Y-shaped DNA duplex, with its tight and nondeformable rigid structure, created well-defined stereoscopic reaction areas and efficiently captures Hg2+ due to its structural differences, thereby improving the signal response. Moreover, larger amounts of methyleneblue (MB) could be loaded to provide adequate electrochemical response signal. The proposed sensor possessing signal amplification ability displayed a linear relationship between the square wave voltammetry (SWV) peak currents. Under the optimal conditions, Hg2+ could be detected in the range from 5000.0 to 5.0 nM with a detection limit of 8.5 pM. The sensor was also tested with tap water, river and medical wastewater samples. It showed the good recovery and accuracy and represented a promising method for Hg2+ detection.

Season and side-chain length affect the occurrences and behaviors of phthalic acid esters in wastewater treatment plants

Emerging pollutants (EPs) are prevalent in aquatic environments globally. Researchers strive to understand their occurrence and behavior prior to their release into the environment. In this study, we examined five wastewater treatment plants (WWTPs), collected 50 wastewater samples and 10 sludge samples. We explored the sources and destinations of phthalic acid esters (PAEs) within these WWTPs using mass balance equations. Wastewater treatment diminished the frequency and concentration of PAEs, and decreased the fraction of short-chain PAEs. We confirmed the increased concentration of PAEs post-primary treatment and modified the mass balance equation. Calculations suggest that weaker “the mix” in winter than in summer and stronger sedimentation in winter than in summer resulted in high efficiency of PAEs removal by winter wastewater treatment. The mass flux of biodegradation was influenced by the combination of biodegradation efficiency and the strength of the particular type of PAEs collected, with no seasonal differences. Mass fluxes for sludge sedimentation were mainly influenced by season and were higher in winter than in summer. This study enhances our understanding of emerging pollutants in manual treatment facilities and offers insights for optimizing wastewater treatment methods for water professionals.

Strength and functionalized borage biochar for effective elimination of nickel contamination: Insight into batch and dynamic flow mode treatment applications

A silica gel-modified borage biochar (BB@Si) was first produced and used as a binding agent for potentially hazardous Ni2+ ions in aqueous systems. The recommended biochar was more effective in eliminating Ni2+ than pristine biochar (BB). Its maximum qm could reach up to 1.39 × 10−3 mol/g at 30 °C, and sorption isotherms showed that the Langmuir model could more accurately define its sorption behavior. The Dubinin-Radushkevich isotherm also revealed that the average sorption energy ranged from 11.00 to 11.14 kJ/mol. Zeta potential tests, SEM images, and FT-IR scans confirmed the interactions between BB@Si and Ni2+ ions. Dynamic flow treatment studies showed high uptake effectiveness when the flow rate and amount of BB@Si were suitable. Nickel desorption yield of around 80% from BB@Si was noted with 0.01 M HCl. The BB@Si column's breakthrough and exhausted points were identified to be 45 and 352 min, respectively. Its maximum exhaustion capacity value was determined to be 52.73 mg/g. Ni2+ removal from the actual wastewater sample exceeded 75%. The resulting outcomes imply the immense potential of employing BB@Si in the treatment of Ni2+– contaminated aqueous systems.

Evaluating storage conditions and enhancement strategies on viral biomarker recovery for WBE applications.

Wastewater-based epidemiology (WBE) is a valuable disease surveillance tool. However, little is known on how factors such as transportation, storage, and wastewater characteristics influence the accuracy of the quantification methods. Hence, this study investigated the impact of storage temperatures and physicochemical characteristics of wastewater on SARS-CoV-2 and influenza A stability using droplet digital PCR. Additionally, strategies to enhance viral recovery were explored. Municipal influent wastewater stored between ±25 and -80 °C was assessed for a period of 84 days to determine viral degradation. Degradation up to 94.1% of influenza A and SARS-CoV-2 was observed in all samples with the highest at ±25 °C. Viral degradation was correlated to the changes in wastewater physicochemical characteristics. The low degradation observed of SARS-CoV-2 in the spiked pellets were indicative of viral adhesion to wastewater solids, which correlated with changes in pH. Ultrasonication frequencies ranging from 4 to 16 kHz, increased SARS-CoV-2 concentrations in the supernatant between 3.30 and 35.65%, indicating viral RNA attachment to wastewater solids. These results highlight the importance of additional pretreatment methods for maximizing RNA recovery from wastewater samples. Based on these findings, it was deduced that wastewater preservation studies are essential, and pretreatment should be included in the WBE methodology.

Dynamics of antimicrobial resistance and susceptibility profile in full-scale hospital wastewater treatment plants.

Drug resistance has become a matter of great concern, with many bacteria now resist multiple antibiotics. This study depicts the occurrence of antibiotic-resistant bacteria (ARB) and resistance patterns in five full-scale hospital wastewater treatment plants (WWTPs). Samples of raw influent wastewater, as well as pre- and post-disinfected effluents, were monitored for targeted ARB and resistance genes in September 2022 and February 2023. Shifts in resistance profiles of Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii antimicrobial-resistant indicators in the treated effluent compared to that in the raw wastewater were also worked out. Ceftazidime (6.78 × 105 CFU/mL) and cefotaxime (6.14 × 105 CFU/mL) resistant species showed the highest concentrations followed by ciprofloxacin (6.29 × 104 CFU/mL), and gentamicin (4.88 × 104 CFU/mL), in raw influent respectively. WWTP-D employing a combination of biological treatment and coagulation/clarification for wastewater decontamination showed promising results for reducing ARB emissions from wastewater. Relationships between treated effluent quality parameters and ARB loadings showed that high BOD5 and nitrate levels were possibly contributing to the persistence and/or selection of ARBs in WWTPs. Furthermore, antimicrobial susceptibility tests of targeted species revealed dynamic shifts in resistance profiles through treatment processes, highlighting the potential for ARB and ARGs in hospital wastewater to persist or amplify during treatment.

Are we using more sugar substitutes? Wastewater analysis reveals differences and rising trends in artificial sweetener usage in Swedish urban catchments

The market for artificial sweeteners as substitutes for conventional sugar (sucrose) is growing, despite potential health risks associated with their intake. Estimating population usage of artificial sweeteners is therefore crucial, and wastewater analysis can serve as a complement to existing methods. This study evaluated spatial and temporal usage of artificial sweeteners in five Swedish communities based on wastewater analysis. We further compared their levels measured in wastewater with the restrictions during the COVID-19 pandemic in Sweden and assessed health risks to the Swedish population. Influent wastewater samples (n = 194) collected in March 2019-February 2022 from communities in central and southern Sweden were analyzed for acesulfame, saccharin, and sucralose using liquid-chromatography coupled with tandem mass spectrometry. Spatial differences in loads for individual artificial sweetener were observed, with sucralose being higher in Kalmar (southern Sweden), and acesulfame and saccharin in Enköping and Östhammar (central Sweden). Based on sucrose equivalent doses, all communities showed a consistent prevalence pattern of sucralose > acesulfame > saccharin. Four communities with relatively short monitoring periods showed no apparent temporal changes in usage, but the four-year monitoring in Uppsala revealed a significant (p < 0.05) annual increase of ∼19 % for sucralose, ∼9 % for acesulfame and ∼8 % for saccharin. This trend showed no instant or delayed effects from COVID-19 restrictions, reflecting positively on the studied population which retained similar exposure to the artificial sweeteners despite potential pandemic stresses. Among the three artificial sweeteners, only acesulfame’s levels were at the lower end of the health-related threshold for consumption of artificially sweetened beverages; yet, all were far below the acceptable daily intake, indicating no appreciable health risks. Our study provided valuable, pilot insights into the spatio-temporal usage of artificial sweeteners in Sweden and their associated health risks. This shows the usefulness of wastewater analysis for public health authorities wishing to assess future relevant interventions.

Adsorption efficiency of chitosan/clinoptilolite (CS/CZ) composite for effective removal of Cd+2 and Cr+6 ions from wastewater effluents of dairy cattle farms.

The wastewater effluent is responsible for the major ecological impact of the dairy sectors. To avoid the negative consequences of heavy metal pollution on the ecosystem, creative, affordable, and efficient treatment methods are now required before the effluent flows into the surrounding area. This study was aimed at assessing the effectiveness of three different adsorbents for Cd+2 and Cr+6 ions from wastewater effluents of dairy farms, including chitosan (CS), clinoptilolite zeolite (CZ), and chitosan/clinoptilolite zeolite (CS/CZ) composite. The adsorption kinetics of the CS/CZ composite were established using the effects of the key variables (pH, agitation speed, adsorbent concentrations, and contact durations). The removal (%) and adsorption capacities, qe (mg/g), were calculated using the data from the adsorption kinetics. Wastewater samples (n = 60) were collected from the wastewater effluents of five farms. Cd+2 and Cr+6 ion concentrations in all collected samples were determined. Following the CS/CZ composite creation, it was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (X-RD), and Fourier-transform infrared spectrum (FT-IR). The CS/CZ composite had an adsorption capacity of 92.4 and 96.5 mg/g for both Cd+2 and Cr+6 ions at a concentration of 2.0 g/100 ml, respectively, while the CZ adsorption capacities for the two ions were 87.5 mg/g and 61.0 mg/g, respectively, at 4.0 g/100 ml concentration. The CS was achieved at 55.56 mg/g and 33.3 mg/g, respectively, at the same concentration. The efficiency of heavy metal removal was enhanced by increasing adsorbent concentration, agitation speed, and contact duration. Using CS/CZ composite at 2.0 g/100 ml concentration, 180 min of contact time, and 300 rpm agitation speed, the greatest removal efficiencies for Cd+2 and Cr+6 ions (96.43 and 98.75%, respectively) were demonstrated.

Wastewater threshold as an indicator of COVID-19 cases in correctional facilities for public health response: A modeling study

Although prison facilities are not fully isolated from the communities in which they are located, most of the population is confined and requires high levels of health vigilance and protection. This study aimed to examine the dynamic relationship between facility-level wastewater viral concentrations and the probability of at least one positive COVID-19 case within the facility. The study period was from January 11, 2021 to May 8, 2023. Wastewater samples were collected and analyzed for SARS-CoV-2 (N1) and pepper mild mottle virus (PMMoV) three times weekly across 14 prison facilities in Kentucky (USA). Positive clinical case reports were also provided. A hierarchical Bayesian facility-level temporal model with a latent lagged process was developed. We modeled facility-specific SARS-CoV-2 (N1) normalized by the PMMoV wastewater concentration ratio threshold associated with at least one COVID-19 clinical case at an 80 % probability. The threshold differed among facilities. Across the 14 facilities, our model demonstrates a mean capture rate of 94.95 % via the N1/PMMoV ratio threshold with pts≥0.5. However, as the pts threshold was set higher, such as at ≥0.9, the mean capture rate of the model was reduced to 60 %. This robust performance underscores the effectiveness of the model for accurately detecting the presence of positive COVID-19 cases among incarcerated people. The findings of this study provide a facility-specific threshold model for public health response based on frequent wastewater surveillance.

Inclusive study of peanut shells derived activated carbon as an adsorbent for removal of lead and methylene blue from water

Green and efficient agro-waste-based activated carbon has been prepared utilizing peanut shells for adsorptive elimination of an industrial dye, methylene blue, and lead from polluted water. The carbonaceous biomass obtained from peanut shells was chemically activated using either NaOH, ZnCl2, or steam and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2 adsorption and desorption studies. The adsorption process was optimal for methylene blue at alkaline pH, while pH 4.5 was optimal for Pb (II) adsorption. The adsorption takes place through pseudo-second-order kinetic, and the rate-governing step of the adsorption procedure are intraparticle diffusion and film diffusion. Furthermore, the thermodynamics of the adsorption process has been studied, and the obtained Gibbs free energy (ΔG°) values are negative (− 35.90 to − 43.59 kJ mol−1) indicating the spontaneous adsorption of the investigated pollutants on the prepared activated carbon. As per the correlation coefficient, the obtained results were best fit by the Langmuir isotherm with maximum adsorption capacity of 303.03 mg g−1 for methylene blue and 130.89 mg g−1 for Pb (II). The activated carbon successfully removed methylene blue and Pb (II) with %removal exceeding 95%. The mechanisms of interaction of Pb (II) with the activated carbon is a combination of electrostatic interaction and ion exchange, while methylene blue interacts with the activated carbon via π–π interaction, hydrogen bonds, and electrostatic interaction. Thus, the prepared activated carbon has been employed to decontaminate wastewater and groundwater samples. The developed agro-waste-based activated carbon is a promising, cost-efficient, green, and accessible tool for water remediation.

Beyond target chemicals: updating the NORMAN prioritisation scheme to support the EU chemicals strategy with semi-quantitative suspect/non-target screening data

BackgroundPrioritisation of chemical pollutants is a major challenge for environmental managers and decision-makers alike, which is essential to help focus the limited resources available for monitoring and mitigation actions on the most relevant chemicals. This study extends the original NORMAN prioritisation scheme beyond target chemicals, presenting the integration of semi-quantitative data from retrospective suspect screening and expansion of existing exposure and risk indicators. The scheme utilises data retrieved automatically from the NORMAN Database System (NDS), including candidate substances for prioritisation, target and suspect screening data, ecotoxicological effect data, physico-chemical data and other properties. Two complementary workflows using target and suspect screening monitoring data are applied to first group the substances into six action categories and then rank the substances using exposure, hazard and risk indicators. The results from the ‘target’ and ‘suspect screening’ workflows can then be combined as multiple lines of evidence to support decision-making on regulatory and research actions.ResultsAs a proof-of-concept, the new scheme was applied to a combined dataset of target and suspect screening data. To this end, > 65,000 substances on the NDS, of which 2579 substances supported by target wastewater monitoring data, were retrospectively screened in 84 effluent wastewater samples, totalling > 11 million data points. The final prioritisation results identified 677 substances as high priority for further actions, 7455 as medium priority and 326 with potentially lower priority for actions. Among the remaining substances, ca. 37,000 substances should be considered of medium priority with uncertainty, while it was not possible to conclude for 19,000 substances due to insufficient information from target monitoring and uncertainty in the identification from suspect screening. A high degree of agreement was observed between the categories assigned via target analysis and suspect screening-based prioritisation. Suspect screening was a valuable complementary approach to target analysis, helping to prioritise thousands of substances that are insufficiently investigated in current monitoring programmes.ConclusionsThis updated prioritisation workflow responds to the increasing use of suspect screening techniques. It can be adapted to different environmental compartments and can support regulatory obligations, including the identification of specific pollutants in river basins and the marine environments, as well as the confirmation of environmental occurrence levels predicted by modelling tools.Graphical

Banana peels as a green bioadsorbent for removing metals ions from wastewater

Bioadsorption using agricultural waste offers a promising approach for removing toxic metals from wastewater. This study explores the potential of chemically activated banana peels (BPs) as a green and cost-effective bioadsorbent for Cu(II) and Zn(II) removal. Fourier-transform infrared (FTIR) spectroscopy revealed the presence of functional groups like alcohols, phenols, and amino acids on activated BPs, potentially responsible for metal ion binding. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of cavities on the BPs surface and the existence of oxygen and potassium. The adsorption capacity of BPs was investigated under various conditions, including pH, contact time, sorbent dosage, metal concentration, and temperature. This study used Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich (D–R) isotherm models to describe the equilibrium results of Cu (II) and Zn (II) adsorption. The Langmuir isotherm model best described the adsorption process, suggesting monolayer coverage of metal ions on the BPs surface. Maximum adsorption capacities were 3.2 mg g−1 for Cu(II) and 2.8 mg g−1 for Zn(II), demonstrating the effectiveness of BPs in metal removal. Kinetic studies indicated pseudo-first-order (PFO) behavior for Cu(II) and pseudo-second-order (PSO) behavior for Zn(II) adsorption. Thermodynamic analysis revealed a spontaneous and exothermic process (negative Gibbes free energy (ΔG°) and enthalpy (ΔH°) with decreased randomness [negative entropy (ΔS°)] at the biosorption interface. Finally, the BPs sorbent was successfully applied to remove different metal ions from real wastewater samples collected from the El Wadi drain.

Bioremediation of petroleum refinery wastewater using Bacillus subtilis IH-1 and assessment of its toxicity.

Environmental contamination from petroleum refinery operations has increased due to the rapid population growth and modernization of society, necessitating urgent repair. Microbial remediation of petroleum wastewater by prominent bacterial cultures holds promise in circumventing the issue of petroleum-related pollution. Herein, the bacterial culture was isolated from petroleum-contaminated sludge samples for the valorization of polyaromatic hydrocarbons and biodegradation of petroleum wastewater samples. The bacterial strain was screened and identified as Bacillus subtilis IH-1. After six days of incubation, the bacteria had degraded 25.9% of phenanthrene and 20.3% of naphthalene. The treatment of wastewater samples was assessed using physico-chemical and Fourier-transform infrared spectroscopy analysis, which revealed that the level of pollutants was elevated and above the allowed limits. Following bacterial degradation, the reduction in pollution parameters viz. EC (82.7%), BOD (87.0%), COD (80.0%), total phenols (96.3%), oil and grease (79.7%), TKN (68.8%), TOC (96.3%) and TPH (52.4%) were observed. The reduction in pH and heavy metals were also observed after bacterial treatment. V. mungo was used in the phytotoxicity test, which revealed at 50% wastewater concentration the reduction in biomass (30.3%), root length (87.7%), shoot length (93.9%), and seed germination (30.0%) was observed in comparison to control. When A. cepa root tips immersed in varying concentrations of wastewater samples, the mitotic index significantly decreased, suggesting the induction of cytotoxicity. However, following the bacterial treatment, there was a noticeable decrease in phytotoxicity and cytotoxicity. The bacterial culture produces lignin peroxidase enzyme and has the potential to degrade the toxic pollutants of petroleum wastewater. Therefore the bacterium may be immobilised or directly used at reactor scale or pilot scale study to benefit the industry and environmental safety.

High throughput and sensitive quantitation of tobacco-specific alkaloids and nitrosamines in wastewater

Tobacco-specific alkaloids and nitrosamines are important biomarkers for the estimation of tobacco use and human exposure to tobacco-specific nitrosamines that can be monitored by wastewater analysis. Thus far their analysis has used solid phase extraction, which is costly and time-consuming. In this study, we developed a direct injection liquid chromatography-tandem mass spectrometry method for the quantification of two tobacco-specific alkaloids and five nitrosamines in wastewater. The method achieved excellent linearity (R2 > 0.99) for all analytes, with calibration ranging from 0.10 to 800 ng/L. Method limits of detection and quantification were 0.17 ng/L (N-nitrosonornicotine, NNN) and 1.0 ng/L (N-nitrosoanatabine (NAT) and NNN), with acceptable accuracy (100 % ± 20 %) and precision (± 15 %). Analyte loss during filtration was < 15 %, and the relative matrix effect was < 10 %. The method was applied to 43 pooled wastewater samples collected from three wastewater treatment plants in Australia between 2017 and 2021. Anabasine and anatabine were detected in all samples at concentrations of 5.0 – 33 ng/L and 12 – 41 ng/L, respectively. Three of the five tobacco-specific nitrosamines (NAT, NNN, and (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol) (NNAL)) were detected, in < 50 % of the wastewater samples, with concentrations nearly ten times lower than the tobacco alkaloids (< 1.0 – 6.2 ng/L). In-sewer stability of the nitrosamines was also assessed in this study, with four (NAT, NNAL, NNN, and N-nitrosoanabasine (NAB)) being stable (i.e. < 20 % transformation over 12 h in both control reactor (CR) and rising main reactor (RM) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) being moderately stable (< 40 % loss over 12 h in RM). This direct injection method provides a high-throughput approach in simultaneous investigation of tobacco use and assessment of public exposure to tobacco-specific nitrosamines.

Complete removal of organophosphate pesticides from wastewaters with sustainable ionic liquid-based aqueous two-phase strategy

Due to extensive food production, organophosphate pesticides (OPs) are widely utilized for crop protection, leading to their presence in the environment. The focus of this study was the design of an efficient aqueous biphasic system (ABS) strategy for OP removal, namely, malathion (MAL), azinphos-methyl (AZM), and chlorpyrifos (CHP) from water. Different ionic liquids (ILs) with symmetrical cations were selected as ABS phase-formers (tetrabutylphosphonium salicylate, tetrabutylammonium salicylate, 1,3-dibutylimidazolium dicyanamide, 1,3-dibutylimidazolium salicylate and 1,3-dibutylimidazolium bromide) with citrate salt as a salting-out agent. Initially, phase diagrams were determined, followed by partition studies revealing that the partition of MAL and CHP aligns with the IL- ABS formation trend, while the AZM partition is governed by specific interactions with ILs. For optimization studies, tetrabutylphosphonium-salicylate i.e. [TBP][Sal]-based ABS was chosen, due to obtained high extraction efficiencies of over 99.3 %. After establishing the effects of pH, temperature, tie-line length, and phase ratio on extraction performance, extraction of OPs from a real wastewater sample further confirmed the effectiveness of the designed method achieving complete removal of each pesticide. Furthermore, recovery of IL was achieved using an antisolvent method to precipitate CHP followed by IL-reuse in three consecutive cycles without efficiency decreased. Finally, it was demonstrated that [TBP][Sal] exhibits low cytotoxic potential, indicating that the presence of low amounts of this IL in aqueous media could be acceptable from ecotoxicological standpoint. This study showcased the exceptional potential of the proposed technology for the efficient and sustainable treatment of wastewater contaminated with OPs, affirming its capability to treat significant wastewater volumes.

The use of Fe3O4/MnO2-Ag nano-photocatalyst to remove dyes from real wastewater samples under visible light

The use of Fe3O4/MnO2-Ag nano-photocatalyst to remove dyes from real wastewater samples under visible light

Efficient degradation of Rhodamine B by visible-light-driven biomimetic Fe(III) complex/peroxymonosulfate system: The key role of FeV=O

Advanced oxidation systems (AOS) hold promise for tackling refractory dyes in wastewater, yet the quest for efficient systems tailored to the degradation of dye remains a formidable hurdle. Here, a novel visible-light-driven AOS, consisting of biomimetic Fe(III) salen complex (FeL, salen= N, N-bis(salicylidene)ethylenediamine) and peroxymonosulfate (PMS), was proposed for highly efficient degradation of Rhodamine B (RhB), a model dye. The proposed AOS was capable of degrading 94.8 % RhB in 40 min, outperforming the typical Fe3+-based system, which achieved only 52.6 % pollutant degradation under identical conditions. As indicated by experimental results and theoretical calculations, the unique Fe-N2O2 coordination structure of FeL facilitated the adsorption of terminal O (O3) at PMS site, thereby enhancing the heterolysis of the O-O bond and generating high-valent iron-oxo species (i.e., FeⅤ=O) rather than radicals (SO4•−, HO•). The system demonstrated robust resistance to interference from environmental anions (Cl−, NO3−, HCO3−, SO42−), pH variations (initial pH 3.0–11.0) and humic acid. More attractively, it achieved 87.3 % chroma and 37.6 % chemical oxygen demand (COD) removal in real dye wastewater samples. This work may shed light on the understanding and development of biomimetic Fe complexes-based AOS for wastewater treatment.

‘Off–On’ determination of lead (Pb2+) and fluoride (F−) ion in fish and wastewater samples using N, S co-doped carbon quantum dots (N, S-CQDs)

Lead is a global priority pollutant. Its presence in aquatic systems is harmful to the human health. Fluoride is essential to the human body, especially in dental health. However, excess fluoride in the body can lead to serious health concerns. Therefore, a simple approach to monitoring lead and fluoride in environmental samples is paramount. In this study, we synthesized N and S co-doped carbon quantum dots under the hydrothermal method by employing citric acid, glutamine, and sodium sulphide (Na2S) as precursors. Characterization of the developed nanosensor was carried out using Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectrophotometer, ultraviolet–visible spectroscopy (UV–Vis), and X-ray diffraction (XRD). The as-prepared nanosensor is spherical with an average particle diameter of 3.45 ± 0.86 nm and emits light in the green region of the spectrum. This material was employed as an ‘on–off’ and ‘off–on’ fluorescent sensor to determine Pb2+ and F− rapidly and selectively. The fluorescence was quenched (turned off) in the presence of Pb2+ because of the strong interaction between Pb2+ ions and the surface functional groups of the as-synthesized material. Subsequently, the quenched fluorescence of the N, S-CQDs + Pb2+ system was restored (turned on) upon the introduction of F− ions, owing to the formation of ionic bonds between Pb2+ and F−. The N S-CQDs were selective towards Pb2+. At the same time, the N, S-CQDs + Pb2+ system exhibited selectivity towards F− ions amidst other ions with low detection limits (LODs) of 13.35 nM and 43.17 nM for Pb2+ and F−, respectively. The dynamic quenching mechanism was suggested based on the absorption spectra and lifetime results. Satisfied recoveries of 89.30–116.40% for Pb2+ and 90.22–115.05% for F- (RSD < 5) were obtained in practical samples of wastewater and fish. We believe that the as-synthesized N S-CQDs can effectively serve as reliable, accurate, and swift nanosensor for detecting Pb2+ and F− in environmental samples.

Development of a "turn off" fluorescent molecularly imprinted nanoparticle-based sensor for selective captopril quantification in synthetic urine and wastewater samples.

The combination of silica nanoparticles with fluorescent molecularly imprinted polymers (Si-FMIPs) prepared by a one-pot sol-gel synthesis method to act as chemical sensors for the selective and sensitive determination of captoprilis described. Several analytical parameters were optimized, including reagent ratio, solvent, concentration of Si-FMIP solutions, and contact time. Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and the ninhydrin assay were used for characterization. The selectivity was evaluated against molecules belonging to other drug classes, such as fluoroquinolones, nonacid nonopioids, benzothiadiazine, alpha amino acids, and nitroimidazoles. Under optimized conditions, the Si-FMIP-based sensor exhibited a working range of 1-15 µM, with a limit of detection (LOD) of 0.7 µM, repeatability of 6.4% (n = 10), and suitable recovery values at three concentration levels (98.5% (1.5 µM), 99.9% (3.5 µM), and 99.2% (7.5 µM)) for wastewater samples. The sensor provided a working range of 0.5-15 µM for synthetic urine samples, with an LOD of 0.4 µM and a repeatability of 7.4% (n = 10) and recovery values of 93.7%, 92.9%, and 98.0% for 1.0 µM, 3.5 µM, and 10 µM, respectively. In conclusion, our single-vessel synthesis approach for Si-FMIPs proved to be highly effective for the selective determination of captopril in wastewater and synthetic urine samples.

Adaption and application of cell-based bioassays to whole-water samples

The increasing presence of contaminants of emerging concern in wastewater and their potential environmental risks require improved monitoring and analysis methods. Direct toxicity assessment (DTA) using bioassays can complement chemical analysis of wastewater discharge, but traditional in vivo tests have ethical considerations and are expensive, low-throughput, and limited to apical endpoints (mortality, reproduction, development, and growth). In vitro bioassays offer an alternative approach that is cheaper, faster, and more ethical, and can provide higher sensitivity for some environmentally relevant endpoints. This study explores the potential benefits of using whole water samples of wastewater and environmental surface water instead of traditional solid phase extraction (SPE) methods for in vitro bioassays testing. Whole water samples produced a stronger response in most bioassays, likely due to the loss or alteration of contaminants during SPE sample extraction. In addition, there was no notable difference in results for most bioassays after freezing whole water samples, which allows for increased flexibility in testing timelines and cost savings. These findings highlight the potential advantages of using whole water samples in DTA and provide a framework for future research in this area.