Challenges of municipal wastewater reclamation for irrigation by MBR and NF/RO: Physico-chemical and microbiological parameters, and emerging contaminants

Azithromycin removal from water via adsorption on drinking water sludge-derived materials: Kinetics and isotherms studies

In this study, we utilized drinking water treatment sludge (WTS) to produce adsorbents through the drying and calcination process. These adsorbents were then evaluated for their ability to remove azithromycin (AZT) from aqueous solutions. The L-500 adsorbent, derived from the calcination (at 500°C) of WTS generated under conditions of low turbidity in the drinking water treatment plant, presented an increase in the specific surface area from 70.745 to 95.471 m2 g-1 and in the total pore volume from 0.154 to 0.211 cm3 g-1, which resulted in a significant AZT removal efficiency of 65% in distilled water after 60 min of treatment. In synthetic wastewater, the rate of AZT removal increased to 80%, in comparison, in a real effluent of a municipal wastewater treatment plant, an AZT removal of 56% was obtained. Kinetic studies revealed that the experimental data followed the pseudo-second-order model (R2: 0.993-0.999, APE: 0.07-1.30%, and Δq: 0.10-2.14%) suggesting that chemisorption is the limiting step in the adsorption using L-500. This finding aligns with FTIR analysis, which indicates that adsorption mechanisms involve π-π stacking, hydrogen bonding, and electrostatic interactions. The equilibrium data were analyzed using the nonlinear Langmuir, Freundlich, and Langmuir-Freundlich isotherms. The Langmuir-Freundlich model presented the best fitting (R2: 0.93, APE: 2.22%, and Δq: 0.06%) revealing numerous interactions and adsorption energies between AZT and L-500. This adsorbent showed a reduction of 19% in its AZT removal after four consecutive reuse cycles. In line with the circular economy principles, our study presents an interesting prospect for the reuse and valorization of WTS. This approach not only offers an effective adsorbent for AZT removal from water but also represents a significant step forward in advancing sustainable water treatment solutions within the framework of the circular economy.

Preparation of La-doped Ti/SnO2-Sb2O4 anode and its electrochemical oxidation performance of rhodamine B

In this paper, La-doped Ti/SnO2-Sb2O4 electrode was prepared by electrodeposition and used for electrochemical degradation of rhodamine B. The optimum preparation conditions of the electrode were optimized as deposition time of 15 min and calcination at 500 ℃ for 2 h. The water treatment conditions were selected as initial pH 3.0, electrolyte Na2SO4 concentration 0.1 M, current density 30 mA cm-2, and initial rhodamine B concentration 20 mg L-1; the color and TOC removal of RhB reached 99.78% and 82.41% within 30 min. The FESEM, XRD, XPS, CV, LSV, and EIS characterization studies demonstrated that Ti/SnO2-Sb2O4-1%La electrode had a dense structure and the highest oxygen evolution potential (2.14 V) and lowest charge transfer resistance (0.198 Ω cm-2), indicating that doped La has lower energy consumption. Moreover, La doping can expand the specific surface area, active site, performance of pollutant degradation, and service life of the electrode. Especially, the service life of Ti/SnO2-Sb2O4-1%La is increased by three times, and the maximum life span reaches 90 min (1000 mA cm-2, 1 M H2SO4). Free radical quenching experiments show that ·OH plays a major role in the degradation of RhB. The Ti/SnO2-Sb2O4-1%La electrode prepared in this paper and its results will provide data support and reference for the design of efficient electrocatalytic electrode.

Trading-off greenhouse gas emissions and 741/2020 European Union water reuse legislation: An experimental MBR study

A trade-off between greenhouse emissions (direct and indirect) and operational costs in the water treatment sector is of great importance, although only few literature studies exist. The paper presents a comprehensive experimental study on a Membrane Bioreactor (MBR) pilot plant at the Water Resource Recovery Facility of Palermo University (Italy). The MBR pilot plant was aimed at reducing carbon footprint while producing water suitable for water reuse in agriculture. Multiple scenarios were assessed to unveil the best operational variables including the assessment of the reclaimed water quality index for water reuse. Results showed the lowest operational costs for the MBR of 5.05 € cent/m3 with Class B according to 741/2020 European legislation. Results revealed optimised values, in terms of airflow rate and backwash frequency, of 0.8 m3/m2/h and 12 times/h, respectively. The highest N2O emission was measured in correspondence of scenario S5 (airflow rate of 1.6 m3/m2/h) with 0.40 mg N2O-N/m2/h in agreement with previous literature studies. The obtained results could effectively address the operators to find a trade-off between operational costs and water quality.

Prioritization of organic contaminants in a reclaimed water irrigation system using wide-scope LC-HRMS screening

A prioritization procedure was developed and implemented at the local level to identify the most relevant organic contaminants of emerging concern (CECs) in an agricultural area irrigated with reclaimed water. A wide-scope screening methodology based on UPLC-HRMS analysis was applied to holistically characterize the CEC footprint in water and its spatial and temporal variations. One hundred and fifty-eight CECs, including pharmaceuticals, industrial chemicals, and pesticides, among others, were identified with a confidence level of 2 in the water samples investigated. After water treatment in the reclamation plant and transport within the irrigation channel network, more than a hundred compounds were still detected at the location where water is abstracted for crop irrigation. Compound ecotoxicity and occurrence (semi-quantified concentrations or peak intensity) were the parameters used to prioritize CECs in the water used for irrigation. Results pointed at venlafaxine, O-desmethyl-venlafaxine, galaxolidone, theophylline/paraxanthine, oxybenzone, and N-phenyl-1-naphtylamine, among others, as CECs of concern in the investigated area. This study provides a simple and cost-effective approach to detecting site-specific priority pollutants that could otherwise be overlooked by national or European regulations. The prioritization tool provided contributes to rationally designing monitoring and attenuation programs and efficiently managing water resources, by ensuring the safety of reclaimed water applications.

Current research trends on emerging contaminants pharmaceutical and personal care products (PPCPs): A comprehensive review

Pharmaceutical and personnel care products (PPCPs) from wastewater are a potential hazard to the human health and wildlife, and their occurrence in wastewater has caught the concern of researchers recently. To deal with PPCPs, various treatment technologies have been evolved such as physical, biological, and chemical methods. Nevertheless, modern and efficient techniques such as advance oxidation processes (AOPs) demand expensive chemicals and energy, which ultimately leads to a high treatment cost. Therefore, integration of chemical techniques with biological processes has been recently suggested to decrease the expenses. Furthermore, combining ozonation with activated carbon (AC) can significantly enhance the removal efficiency. There are some other emerging technologies of lower operational cost like photo-Fenton method and solar radiation-based methods as well as constructed wetland, which are promising. However, feasibility and practicality in pilot-scale have not been estimated for most of these advanced treatment technologies. In this context, the present review work explores the treatment of emerging PPCPs in wastewater, via available conventional, non-conventional, and integrated technologies. Furthermore, this work focused on the state-of-art technologies via an extensive literature search, highlights the limitations and challenges of the prevailing commercial technologies. Finally, this work provides a brief discussion and offers future research directions on technologies needed for treatment of wastewater containing PPCPs, accompanied by techno-economic feasibility assessment.

Effects of high-strength landfill leachate effluent on stress-induced microalgae lipid production and post-treatment micropollutant degradation

This research investigates the effects of landfill leachate effluent concentrations from moving bed biofilm reactor (MBBR) on stress-induced Chlorella vulgaris and Scenedesmus armatus lipid production and post-treatment micropollutant degradation. The effluent concentrations were varied between 25%, 50%, 75%, and 100% (v/v). The landfill leachate influent was treated using two-stage moving bed biofilm reactor under 24 h and 18 h hydraulic retention time (HRT). The results indicated that the effluent concentration was positively correlated with the stress-induced microalgae lipid production in the post-treatment of residual micropollutants. C. vulgaris and S. armatus completely remove residual micropollutants in the effluent. The superoxide dismutase and peroxidase activity were positively correlated with the cellular lipid content. The lipid content of C. vulgaris and S. armatus cultivated in the 18 h HRT effluent were 31-51% and 51-64%, while those in the 24 h HRT effluent were 15-16% and 5-19%. The optimal condition of microalgae cultivation for the post-treatment of residual micropollutants was 50-75% (v/v) effluent concentrations under 18 h HRT, achieving the highest lipid production of 113-116 mg/L for C. vulgaris and 74-75 mg/L for S. armatus. Essentially, the MBBR landfill leachate effluent holds promising potential as a substrate for microalgae lipid production.

Validation of Recycled Nanofiltration and Anion-Exchange Membranes for the Treatment of Urban Wastewater for Crop Irrigation

One of the alternative sources to tackle the problem of water shortage is the use of reclaimed water from wastewater treatment plants for irrigation purposes. However, when the wastewater has a high conductivity value, it becomes unusable for crop irrigation and needs a more specific treatment. In this work, recycled nanofiltration (rNF) membranes and anion-exchange membranes (rAEMs) obtained from end-of-life RO membranes were validated to evaluate their application capability in saline wastewater treatment. The use of recycled membranes may represent an advantage due to their lower cost and reduced environmental impact associated with their production, which integrates membrane-based technology into a circular economy model. Both recycled membranes were tested in crossflow filtration and electrodialysis (ED) systems. The results of the rNF membrane showed a high selective rejection of divalent ions (SO42− (>96%) and Ca2+ and Mg2+ (>93%)). In the case of the ED process, the comparison between rAEMs and commercial membranes showed an appropriate demineralization rate without compromising the power consumption. Finally, the quality of both system effluents was suitable for irrigation, which was compared to the WHO guideline and validated by the 7-week lettuce crop study.

Construction of SnO2/g-C3N4 an effective nanocomposite for photocatalytic degradation of amoxicillin and pharmaceutical effluent

The current study mainly focused on the fabrication of 2D graphitic carbon nitride-supported tin oxide nanoparticles (SnO₂/g-C₃N₄) for the effective degradation of Amoxicillin (AMX). Tin oxide (SnO₂) NPs were prepared by green and easy modification technique, and then it is decorated over g-C₃N₄ nanosheets. The structural morphology and surface composition of the synthesized SnO₂/g-C₃N₄ nanocomposite were fully analysed by UV-Vis, XRD, XPS, and HR-SEM with EDAX, FT-IR, and BET analysis. The (HR-TEM) microscopy, the size of SnO₂ NPs which as a diameter is about 6.2 nm. The Raman analysis revealed that the SnO₂/g-C₃N₄ composite had a moderate graphitic structure, with a measured I_D/I_g value of 0.79. The degradation efficiency of antibiotic pollutant AMX and pharma effluent treatment was monitored by UV spectroscopy. The optical band gap of SnO₂ (2.9 eV) and g-C₃N₄ (2.8 eV) photocatalyst was measured by Tauc plots. To investigate the mechanism through the photodegradation efficiency of the catalyst was analysed by using different Scavenger EDTA-2Na holes (h⁺) has a greater contribution towards the degradation process. Under visible irradiation, SnO₂/g-C₃N₄ nanocomposite has exhibited an excellent degradation performance of 92.1% against AMX and 90.8% for pharmaceutical effluent in 80 min.

Techno-economic assessment of decentralized polishing schemes for municipal water reclamation and reuse in the industrial sector in costal semiarid regions: The case of Barcelona (Spain)

This study demonstrates the techno-economic reliability of an innovative fit-for-use treatment train to boost municipal reclaimed water reuse fore industrial uses in the Barcelona Metropolitan Area (BMA). The relatively high conductivity (2090 μS/cm) and hardness (454 mg/L) of reclaimed water in the BMA (e.g. Water Reclamation Plant (WRP) of El Baix Llobregat, Barcelona, Spain), together with the restrictive water quality demands in industrial uses, claims for the implementation of advanced reclamation schemes based on desalination technologies such as reverse osmosis (RO). The study assesses the benefits of two potential pre-treatments of the RO stage: (i) ultrafiltration (UF) or (ii) an innovative high-performance nano-structured polymeric adsorbent (CNM); in which a permeability decline of 5% was observed when CNM was used as a pre-treatment, while a stable permeability of RO was found when was fed by the UF effluent. On the other hand, generic cost curves have been calculated for the technologies evaluated and were applied to estimate capital and operational expenditures (CAPEX and OPEX) for the scale-up in three different industrial sites (e.g., chemical, waste management and electro-coating industries). The economic assessment indicates that the use of municipal reclaimed water is economically competitive in front of the use of tap water in the BMA, providing savings between 0.13 and 0.52 €/m³ for the waste management industry and between 0.49 and 0.98 €/m³ for the electrocoating industry. On the other hand, the use of groundwater in one of the industrial sites and its relatively low cost implied that, although it is necessary a RO, the current cost of water is significantly lower.

Oxidative stress and metal homeostasis alterations in Danio rerio (zebrafish) under single and combined carbamazepine, acetamiprid and cadmium exposures

Contaminants of emerging concern (CEC) are routinely detected in aquatic environments, especially pharmaceuticals, such as carbamazepine (CBZ), and neonicotinoid pesticides, like acetamiprid (ACT). CECs can interact with each other and with other legislated contaminants like Cd, resulting in unknown effects. Most studies evaluate only the effects of single contaminant exposures on aquatic biota. Therefore, the aim of the present study was to assess the effects of both single and combined CBZ, ACT and Cd exposures on zebrafish brain and liver oxidative stress parameters and metal homeostasis. The biomarkers catalase (CAT), glutathione-S-transferase (GST), total thiols (TOT), metallothionein (MT) and malondialdehyde (MDA) and the essential elements Ca, Cu, K, Na, Mg, Mn and Zn were evaluated after 96-hour static exposures. CBZ, ACT and Cd single (brain and liver) and combined (liver) treatments resulted in oxidative effects in both fish organs, also leading to metal (Ca, Mg, K, Mn, Zn and Cu) homeostasis alterations. ACT exposure resulted in the greatest adverse effects in the brain, while CBZ was the cause of major element homeostasis and oxidative stress alterations in the liver. Lower LPO levels were observed in the combined treatments compared to single treatments, suggesting interactions and contaminant effect attenuation. This study is the first to evaluate the initial effects of combined CBZ, ACT and Cd exposures in zebrafish, paving the way for further investigations concerning other biomarkers during longer exposure times.

Pharmaceutical compounds used in the COVID-19 pandemic: A review of their presence in water and treatment techniques for their elimination

During the COVID-19 pandemic, high consumption of antivirals, antibiotics, antiparasitics, antiprotozoals, and glucocorticoids used in the treatment of this virus has been reported. Conventional treatment systems fail to efficiently remove these contaminants from water, becoming an emerging concern from the environmental field. Therefore, the objective of the present work is to address the current state of the literature on the presence and removal processes of these drugs from water bodies. It was found that the concentration of most of the drugs used in the treatment of COVID-19 increased during the pandemic in water bodies. Before the pandemic, Azithromycin concentrations in surface waters were reported to be in the order of 4.3 ng L-1, and during the pandemic, they increased up to 935 ng L-1. Laboratory scale studies conclude that adsorption and advanced oxidation processes (AOPs) can be effective in the removal of these drugs. Up to more than 80% removal of Azithromycin, Chloroquine, Ivermectin, and Dexamethasone in aqueous solutions have been reported using these processes. Pilot-scale tests achieved 100% removal of Azithromycin from hospital wastewater by adsorption with powdered activated carbon. At full scale, treatment plants supplemented with ozonation and artificial wetlands removed all Favipiravir and Azithromycin, respectively. It should be noted that hybrid technologies can improve removal rates, process kinetics, and treatment cost. Consequently, the development of new materials that can act synergistically in technically and economically sustainable treatments is required.

Occurrences and removal of pharmaceutical and personal care products from aquatic systems using advanced treatment- A review

Pharmaceuticals, personal care items, steroid hormones, and agrochemicals are among the synthetic and indigenous products that make up micropollutants, also known as emerging contaminants. Pharmaceutical and personal care products (PPPs) are a class of developing micropollutants that can harm living organisms even at low concentrations. Many are detected in surface water and wastewater from the treatment process, with quantities ranging from ng L-1 to gL-1; however, residual PPPs at dangerously high levels have indeed recently been recognized in the ecosystem. Residential sewage treatment plant (STP) dump the largest majority of these pollutants into the environment on a regular basis. As a result of its robust structure, it has a longer lifespan in the environment. This review article discusses how surface water pollutants such pesticides, petroleum hydrocarbons, and perfluorinated compounds affect water quality, as well as the most cost-effective adsorbents for removing these PPPs. The goal of this study is to provide information about the origins of PPP, as well as diagnostic procedures and treatment options. Research on developing contaminants is also aimed at evaluating the efficacy and affordability of adsorption.

Microbial Technologies Employed for Biodegradation of Neonicotinoids in the Agroecosystem

Neonicotinoids are synthetic pesticides widely used for the control of various pests in agriculture throughout the world. They mainly attack the nicotinic acetylcholine receptors, generate nervous stimulation, receptor clot, paralysis and finally cause death. They are low volatile, highly soluble and have a long half-life in soil and water. Due to their extensive use, the environmental residues have immensely increased in the last two decades and caused many hazardous effects on non-target organisms, including humans. Hence, for the protection of the environment and diversity of living organism's the degradation of neonicotinoids has received widespread attention. Compared to the other methods, biological methods are considered cost-effective, eco-friendly and most efficient. In particular, the use of microbial species makes the degradation of xenobiotics more accessible fast and active due to their smaller size. Since this degradation also converts xenobiotics into less toxic substances, the various metabolic pathways for the microbial degradation of neonicotinoids have been systematically discussed. Additionally, different enzymes, genes, plasmids and proteins are also investigated here. At last, this review highlights the implementation of innovative tools, databases, multi-omics strategies and immobilization techniques of microbial cells to detect and degrade neonicotinoids in the environment.

Membrane bioreactors for hospital wastewater treatment: recent advancements in membranes and processes

Discharged hospital wastewater contains various pathogenic microorganisms, antibiotic groups, toxic organic compounds, radioactive elements, and ionic pollutants. These contaminants harm the environment and human health causing the spread of disease. Thus, effective treatment of hospital wastewater is an urgent task for sustainable development. Membranes, with controllable porous and nonporous structures, have been rapidly developed for molecular separations. In particular, membrane bioreactor (MBR) technology demonstrated high removal efficiency toward organic compounds and low waste sludge production. To further enhance the separation efficiency and achieve material recovery from hospital waste streams, novel concepts of MBRs and their applications are rapidly evolved through hybridizing novel membranes (non hydrophilic ultrafiltration/microfiltration) into the MBR units (hybrid MBRs) or the MBR as a pretreatment step and integrating other membrane processes as subsequent secondary purification step (integrated MBR-membrane systems). However, there is a lack of reviews on the latest advancement in MBR technologies for hospital wastewater treatment, and analysis on its major challenges and future trends. This review started with an overview of main pollutants in common hospital waste-water, followed by an understanding on the key performance indicators/criteria in MBR membranes (i.e., solute selectivity) and processes (e.g., fouling). Then, an in-depth analysis was provided into the recent development of hybrid MBR and integrated MBR-membrane system concepts, and applications correlated with wastewater sources, with a particular focus on hospital wastewaters. It is anticipated that this review will shed light on the knowledge gaps in the field, highlighting the potential contribution of hybrid MBRs and integrated MBR-membrane systems toward global epidemic prevention.

Current advances in microalgae-based bioremediation and other technologies for emerging contaminants treatment

Emerging contaminants (EC) have been detected in effluents and drinking water in concentrations that can harm to a variety of organisms. Therefore, several technologies are developed to treat these compounds, either for their complete removal or degradation in less toxic by-products. Some technologies applied to the treatment of EC, such as adsorption, advanced oxidative processes, membrane separation processes, and bioremediation through microalgal metabolism, were identified by thematic maps. In this review, we used a bibliometric software from >1000 articles. These manuscripts, in general, present removals from 0% to 100% for different ECs. This efficiency varies between treatment technologies and the contaminants' physical-chemical properties and their concentration and operational parameters. This review explored the bioremediation of EC through microalgae with greater emphasis. The main mechanisms of action of microalgae in the bioremediation of ECs are biodegradation bioadsorption, and bioaccumulation. Also, physicochemical properties and removal efficiencies of >50 emerging contaminants are presented. Although there are challenges related to the generation of more toxic by-products and economic and environmental viability, these can be minimized with advances in the development of treatment technologies and even through the integration of different techniques to make the treatment of contaminants emerging from environmental media more sustainable.

Simultaneous degradation of 30 pharmaceuticals by anodic oxidation: Main intermediaries and by-products

The anodic oxidation (AO) of 30 pharmaceuticals including antibiotics, hormones, antihistaminics, anti-inflammatories, antidepressants, antihypertensives, and antiulcer agents, in solutions containing different supporting electrolytes media (0.05 M Na₂SO₄, 0.05 M NaCl, and 0.05 M Na₂SO₄ + 0.05 M NaCl) at natural pH was studied. A boron-doped diamond (BDD) electrode and a stainless-steel electrode were used as anode and cathode, respectively, and three current densities of 6, 20, and 40 mA cm^-2 were applied. The results showed high mineralization rates, above 85%, in all the tested electrolytic media. 25 intermediaries produced during the electrooxidation were identified, depending on the supporting electrolyte together with the formation of carboxylic acids, NO₃^-, SO₄^2- and NH₄⁺ ions. The formation of intermediates in chloride medium produced an increase in absorbance. Finally, a real secondary effluent spiked with the 30 pharmaceuticals was treated by AO applying 6 mA cm^-2 at natural pH and without addition of supporting electrolyte, reaching c.a. 90% mineralization after 300 min, with an energy consumption of 18.95 kW h m^-3 equivalent to 2.90 USD m^-3. A degradation scheme for the mixture of emerging contaminants in both electrolytic media is proposed. Thus, the application of anodic oxidation generates a high concentration of hydroxyl radicals that favors the mineralization of the pharmaceuticals present in the spiked secondary effluent sample.

Removal and environmental risk assessment of contaminants of emerging concern from irrigation waters in a semi-closed microalgae photobioreactor

The present study evaluated the efficiency of a semi-closed, tubular, horizontal photobioreactor (PBR) to treat a mixture of irrigation and rural drainage water, focusing in the removal of different contaminants of emerging concern (CECs), and evaluating the environmental impact of the resulting effluent. Target CECs included pharmaceuticals, personal care products and flame retardants. Of the 13 compounds evaluated, 11 were detected in the feed water entering the PBR, and diclofenac (DCF) (1107 ng L^-1) and N,N-diethyl-toluamide (DEET) (699 ng L^-1) were those present at the greatest concentrations. The best removal efficiencies were achieved for the pharmaceuticals diazepam (94%), lorazepam (LZP) (83%) and oxazepam (OXA) (71%), and also for ibuprofen (IBU) (70%). For the rest of the CECs evaluated, attenuation was similar to that obtained after conventional wastewater treatment, ranging from basically no elimination (carbamazepine (CBZ) and tris-(2-chloroethyl) phosphate (TCEP)) to medium efficiencies (DCF and tributyl phosphate (TBP) (50%)). Environmental risk assessment based on hazard quotients (HQs) resulted in HQ values < 0.1 (no risk associated) for most of the compounds and most of the trophic levels considered. Values between 1 and 10 (moderate risk) were obtained for tonalide (AHTN) (fish) and CBZ (invertebrates). The most sensitive trophic level was green algae, whereas fish and aquatic plants were the most resilient. Our results suggest that microalgae-based treatments could become a green, cost-effective alternative to conventional wastewater treatment regarding the efficient elimination of these contaminants.

The Removal of Selected Inorganics from Municipal Membrane Bioreactor Wastewater Using UF/NF/RO Membranes for Water Reuse Application: A Pilot-Scale Study

Membrane technology has advanced substantially as a preferred choice for the exclusion of widespread pollutants for reclaiming water from various treatment effluent. Currently, little information is available about Ultrafiltration (UF)/Nanofiltration (NF)/Reverse Osmosis (RO) performance at a pilot scale as a practical engineering application. In this study, the effluent from a full-scale membrane bioreactor (MBR) municipal wastewater treatment works (MWWTWs) was treated with an RO pilot plant. The aim was to evaluate the effect of operating conditions in the removal of selected inorganics as a potential indirect water reuse application. The influent pH, flux, and membrane recovery were the operating conditions varied to measure its influence on the rejection rate. MBR/RO exhibited excellent removal rates (>90%) for all selected inorganics and met the standard requirements for reuse in cooling and irrigation system applications. The UF and NF reduction of inorganics was shown to be limited to meet water standards for some of the reuse applications due to the high Electron Conductivity (EC > 250 μS·cm-1) levels. The MBR/NF was irrigation and cooling system compliant, while for the MBR/UF, only the cooling system was compliant.

Preparation and electrochemical treatment application of Ti/Sb-SnO2-Eu&rGO electrode in the degradation of clothianidin wastewater

This work investigated the preparation of Ti/Sb-SnO₂ electrode co-doped with graphene and europium and the electrochemical degradation of clothianidin in aqueous solution with Ti/Sb-SnO₂-Eu&rGO electrode. The physicochemical properties of different electrodes were characterized by using the scanning electron microscopy, X-ray diffraction, oxygen evolution potential and cyclic voltammetry tests. The results indicated that the Ti/Sb-SnO₂-Eu&rGO electrodes have a compact structure and fine grain size and have a higher oxygen evolution overpotential than Ti/Sb-SnO₂-None, Ti/Sb-SnO₂-Eu and Ti/Sb-SnO₂-rGO electrodes. Among the four electrodes, the Ti/Sb-SnO₂-Eu&rGO electrode showed the highest efficiency and was chosen as the experimental electrode. The main influence factors on the degradation of clothianidin, such as initial pH, electrolyte concentration, current density and initial concentration of clothianidin, were analyzed. The results showed that the removal rate of clothianidin can reach 96.44% under the optimal conditions for 120 min treatment. Moreover, a possible degradation pathway including the fracture of internal bonds of clothianidin such as the N-N bond, the C-N bond that connects nitroguanidine to the thiazole ring and mineralization was elucidated by intermediate products identified by HPLC-MS method and Fourier transform infrared spectroscopy (FTIR). This paper introduces the Ti/Sb-SnO₂-Eu&rGO electrode into an electrocatalytic degradation system and could provide basic data and technique support and guidance for the clothianidin wastewater pollution control.

Tricks and tracks in removal of emerging contaminants from the wastewater through hybrid treatment systems: A review

In recent years, many biological and physicochemical treatment technologies have been investigated for the removal of the emerging contaminants (ECs) from the wastewater matrix. However, due to the deficiency of these treatments to completely degrade the ECs in wastewater, hybrid systems were explored using the distinguishing removal potential of the different treatment processes. This review gives an insight on such hybrid systems combining several physical, chemical and biological treatments for the fast and eco-efficient removal of ECs from wastewater. Most of the hybrid systems have applied biological treatments first and then physical or chemical treatments. The hybrid system of membrane bioreactor (MBR) followed by membrane filtrations (RO/NF) effectively removed a suite of ECs such as pharmaceuticals, beta blockers, pesticides and EDCs. Some of the hybrid systems of constructed wetlands and waste stabilization ponds showed promising potential for the biosorptive removal of pharmaceuticals and some beta blockers. The hybrid systems combining activated sludge process and physical processes such as ultrafiltration (UF), reverse osmosis (RO) and gamma radiations are considered as the cost effective technologies and had better removal of trace organic pollutants. The hybrid system of MBR coupled with UV oxidation, activated carbon and ultrasound, and ozonation followed by ultrasounds, completely degraded some ECs and many pharmaceuticals. The review also synthesizes the trend followed by the hybrid system processes for the removal of various categories of ECs. The future research directions for the ECs removal utilizing hybrid nanocomposites and green sustainable technology have been suggested.