Wastewater Treatment Techniques Research Articles

Computer-aided batch process design, techno-economic and uncertainty analyses of bio-clarified water recovery from south-eastern Nigerian brewery wastewater

Biocoagulation-flocculation-sedimentation (bioclarification) is one of the main wastewater treatment techniques. Despite its effectiveness in treating brewery wastewater for water reuse, the scale-up process for the reclaimed brewery water from wastewater has rarely been documented in the literature. This study presents the computer-aided process design, techno-economic and uncertainty analyses of bioclarified water production from brewery wastewater. The base-case simulation model, process scale-up design and economics were performed in Aspen Batch Process Developer. Process profitability indices (Net Present Value: (NPV), Internal Rate of Return: (IRR) and Payback Time: PBT) were evaluated in a user-defined developed Microsoft-excel version 2018. Monte-Carlo-Simulation in Crystal-Ball-Oracle software was used to perform the sensitivity and uncertainty analyses. The process scale-up simulation results gave annual production capacity (45,000,000 L/year), batch size (9800 L/batch) and annual number of batches produced (4564 batches/year). Base case capacity results showed that the total capital investment, NPV, IRR and PBT are $2,416,358.62, $2,790,608, 36% and 3.27years respectively. Sensitivity analysis shows that production capacity and product selling price have the highest contribution for both NPV and IRR respectively. Certainties of base-case model were 90.27% for the IRR and 99.51% for the NPV. This study showed that brewery wastewater bioclarification scale-up design is feasible.

Synthesis of Bamboo-based Activated Carbon through Physico-chemical Activation for Coal-runoff Wastewater Treatment

Bamboo-based activated carbon (BAC) has been successfully synthesized through a physico-chemical technique. The characteristics of BAC were investigated using Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FTIR), and X-Ray Diffraction (XRD). Evaluating BAC performance on coal-runoff wastewater was carried out by varying contact times and adding low-level alum on remediation of pH and Total Suspended Solid (TSS). The results confirm that BAC performs well in stabilizing pH, indicated by the neutral pH, after 10 minutes of interaction. The TSS with BAC treatment and 1% BAC-Alum combination reduced the TSS value from 880 mg/L to levels below the threshold for wastewater quality standards, 387 mg/L and 73 mg/L, respectively. This combination can be an alternative coal-runoff wastewater treatment technique for better environmental quality.

Potentials of Constructed Wetland for the Treatment of Wastewater from Cocopeat Production Industry

The cocopeat production industry generates a significant amount of wastewater containing high organic loads and chemical residues, posing environmental challenges and economic concerns. This study aims to assess the potential of constructed wetlands as an innovative and sustainable approach for managing coco peat production industry wastewater. An artificial wetland was created and filled with 30% soil, 40% sand, 10% bio and hydrochar, and 20% gravel along with Canna indica was used as the plant component. Three types of hydraulic loading rates were studied: 5 ml/min, 10 ml/min, and 15 ml/min, with a retention time of 7 days.
 The results showed that the wastewater contains significant levels of Electrical Conductivity (5.24 – 6.31 dS m-1), Total Dissolved Solids (4190 - 5150 mg/L), Biochemical Oxygen Demand (730 - 818 mg/L), and Chemical Oxygen Demand (1825 – 2045 mg/L). The utilization of artificial wetlands along with Canna indica decreased the pollution loads by 42% of Electrical Conductivity, 41% of Biochemical Oxygen Demand, and Chemical Oxygen Demand, 45% of Total Suspended Solids, and 55% of Total Dissolved Solids.
 Based on the above results, constructed wetlands are recognized as a reliable wastewater treatment technique and a good solution for the treatment of coirpith washwater, which is a step towards a greener and more sustainable future. By integrating these natural filtration systems into the wastewater treatment process, industries can foster a harmonious coexistence with the environment, ensuring a balance between economic growth and environmental well-being.

Removal and Recovery of Copper from Industrial Waste Streams: Design of an Electrochemical Cell

Copper (Cu) exists in a variety of wastewater and process streams in a host of chemical, manufacturing, and commercial industries. These instances include complex streams from chemical-mechanical planarization (CMP) processes in the semiconductor industry, rinse streams from plating baths at electroplaters, and commercial discharge to surface waters requiring Cu concentrations to be well below 1 ppm. Conventionally, the removal of Cu from wastewater has followed two routes: (1) precipitation with an iron-based coagulant and (2) ion exchange (IX) to selectively removal lower concentrations of Cu.1 Coagulation approaches, while effective, produce a notable amount of sludge waste that must be disposed of properly. Recovery of specific metals from this sludge is also quite difficult, meaning that the value in the metals that are removed with the sludge would be lost. IX, while also a long-validated technology, needs to be used under highly specific conditions and often leads to unreliable separations, particularly during production upsets in upstream equipment.Electrochemical separations can alleviate many of the problems in existing wastewater treatment techniques. In particular, capacitive deionization (CDI) as an electrochemical separation route has seen significant development over the last decade, highlighting the ability for electrochemical cells to be used in new and useful ways.2 However, CDI often suffers from diminished separation lifetime and lack of high selectivity during the separation process, although gains in selectivity have been recently explored.3 In this talk, the use of a new electrochemical process will be reviewed for the selective removal and recovery of Cu.4 Use of asymmetric carbon electrodes in an electrochemical cell is found to provide localized conditions capable of effectively removing >95% of Cu from an influent stream while symmetric configurations offer much lower levels of Cu removal. Design of the carbon electrodes for fast Cu removal kinetics along with approaches to design of the electrochemical cell for high throughput will be reviewed. Electrode density, surface area, and spacing are found to impact the effectiveness of the resulting separation. Lifetime of this new separation process will also be reviewed with demonstrations of >20 hours of operation. Degradation mechanisms and the ability to mitigate loss of performance will be presented.

Advances on sonophotocatalysis as a water and wastewater treatment technique: efficiency, challenges and process optimisation.

Due to water shortage and increased water pollution, various methods are being explored to improve water quality by treating contaminants. Sonophotocatalysis is a combination of two individual water treatment processes i.e., photocatalysis and sonocatalysis. With advantages including shorter reaction times and enhanced activity, this technique shows possible futuristic applications as an efficient water treatment technology. Herein, background insight on sonophotocalysis as a water and wastewater treatment technique as well as the general mechanism of activity is explained. The commonly used catalysts for sonophotocatalytic applications as well as their synthesis pathways are also briefly discussed. Additionally, the utilisation of sonophotocatalysis for the disinfection of various microbial species as well as treatment of wastewater pollutants including organic (dyes, pharmaceuticals and pesticides) and inorganic species (heavy metals) is deliberated. This review also gives a critical analysis of the efficiency, enhancement strategies as well as challenges and outlooks in this field. It is thus intended to give insight to researchers in the context of facilitating future developments in the field of water treatment, and advancing sonophotocatalysis towards large-scale implementation and commercialization.

Wastewater Problems Analysis and Their Treatment Using Eco-friendly Techniques: An Overview

In the current changing environment where almost all activities involve the use of clean water, waste water is discharged in a huge amount, which not only pollutes the environment but also causes many diseases in human as well as in animal. The scarcity of the most limited natural resource, "clean water" for daily use is decreasing day by day. So, the present study was done to assess various harmful effects of wastewater and techniques to overcome these effects through different plant-based wastewater treatment methods. There are few researches conducted to overcome the problem of wastewater biologically, the researchers used different plans to treat wastewater which absorb toxic substances up to a greater extent and clean the water efficiently. In the current study, some environmentally friendly wastewater treatment techniques—such as seaweed-based flocculants, mangrove plants, phyto-accumulation, Phyto remediation etc.—are discussed in order to better understand how they work and to advocate for their widespread use.

Assessment of the Potentials of Theobroma Cacao Pod-Feldspar Composite Adsorbent for Heavy Metal Removal in Waste Water

Purpose: Most conventional wastewater treatment techniques for the removal heavy metals are highly expensive and may, create sludge disposal problems. Adsorption techniques are relatively cheaper particularly when the process is carried out using low-cost materials and biomass. This paper is on the assessment of the potentials of a modified feldspar composite absorbent developed from waste agricultural biomass (Theobroma cocoa pod) and feldspar mineral in the removal of heavy metals from wastewater.
 Methodology: The physicochemical analysis were carried out on the wastewater samples before and after treatment with modified feldspar composite using standard methods. Portions of the samples were directly digested and analysed for Pb, Cd, Cr and As, while the second portions were treated with the modified Theobroma cocoa pod-Felspar (TCPF) adsorbent under optimum conditions before analysing for the heavy metals. The desorption (cleaning) of the TCPF adsorbent after the adsorption of the heavy metals (Pb, Cd, As and Cr) from the wastewater was carried out with 0.1 M HCl.
 Findings: The AAS analysis revealed that, the concentrations of the heavy metals in the wastewater before treatment with TCPF were higher and followed Pb>Cr>Cd>As trend and were above WHO and NESREA standards. The values for the samples treated with TCPF were lower and followed Cr>As>Pb>Cd trend and were within the standards. The differences between the values for the individual metals in the wastewater before and after treatment with the TCPF adsorbent were significant at p< 0.05. The adsorption efficiency of the TCPF was high for Pb (98.92%), Cd (96.88%) and Cr (97.18). Similarly, the TCPF showed high desorption efficiency with 76.8% for Pb, 90.6% for Cd, 94.4% for As and 80.3% for Cr.
 Unique contribution to theory policy and practice: The modified composite (TCPF) has shown some significant potentials for use in the removal of the selected heavy metals from wastewater and industrial effluent.

Isotherm and kinetic investigations of sawdust-based biochar modified by ammonia to remove methylene blue from water

Chemical industry effluent may pose significant environmental risks to both human health and the economy if it is not properly managed. As a result, scientists and decision-makers are paying increasing attention to developing a sustainable, low-cost wastewater treatment technique. This work aims to investigate the adsorption of Methylene Blue (MB) dye present in water using biochar derived from sawdust modified by boiling in an ammonia solution (SDBA). The properties of SDBA were characterized by BET, SEM, XRD, BJH, FT-IR, DTA, EDX and TGA analyses. The presence of –OH and –NH groups in SDBA was confirmed by FTIR, which proved that the NH4OH treatment of biochar successfully added nitrogen groups on its surface. The influence of pH (2 to 12), MB dye initial concentration (20 to 120 mg/L), adsorbent dosage (0.5 to 4.0 g/L) and contact time (0 to 180 min) on the adsorption process has been investigated. The adsorption of MB dye is more favorable at basic pH, with optimum adsorption at pH 8. Using a starting concentration of 20 mg/L of MB dye and a 4.0 g/L SDBA dose, the maximum percent clearance of MB dye was 99.94%. Experimental results were fitted to the Freundlich (FIM), Tempkin (TIM) and Langmuir (LIM) isotherm models (IMs). The FIM fitted the equilibrium data well, with a 643.74 mg/g Qm. Various error function models were used to test the data obtained from IMs. According to Error Function results, experimental data showed that it fits better for LIM and FIM. Kinetic studies indicated that the MB dye adsorption procedure followed pseudo-second-order (PSOM) kinetics based on film diffusion (FDM), pseudo-first-order (PFOM) and intra-particle diffusion models (IPDM). MB dye sorption on the SDBA involved electrostatic interaction, surface participation, hydrogen bond and π–π interactions. The adsorption mechanism of MB dye by SDBA was proposed as physical adsorption via the electrostatic attraction process. SDBA is an effective adsorbent in removing MB dye from water. Six adsorption–desorption cycles of the MB dye were run through the regeneration of SDBA with only a minimal amount of adsorption capacity loss, demonstrating the reusability of manufactured SDBA.

Bioremediation of Azo Dye Brown 703 by Pseudomonas aeruginosa: An Effective Treatment Technique for Dye-Polluted Wastewater

Dye-polluted wastewater poses a serious threat to humans’, animals’ and plants’ health, and to avoid these health risks in the future, the treatment of wastewater containing dyes is necessary before its release to environment. Herein, a biological approach is used; the textile azo dye brown 703 is degraded utilizing Pseudomonas aeruginosa. The bacterial strain was isolated from textile wastewater dumping sites in Mingora, Swat. The optimization for bacterial degradation was carried out on the nutrient broth medium, which was then subjected to a variety of environmental physicochemical conditions and nutritional source supplementation before being tested. Under micro-aerophilic circumstances, the maximum decolorization and degradation of dye occurred at a 20 ppm dye concentration within 3 days of incubation at a neutral pH and 38 °C. The decrease in the intensity of the absorbance peak in the UV–Vis spectrum was used to measure the extent of decolorization. Initially, 15 bacterial strains were isolated from the textile effluent. Out of these strains, Pseudomonas aeruginosa was found to be the most potent degrading bacteria, with a degradation extent of around 71.36% at optimum conditions. The appearance and disappearance of some new peaks in the FT-IR analysis after the degradation of brown 703 showed that the dye was degraded by Pseudomonas aeruginosa. The GC–MS analysis performed helped in identifying the degraded compounds of azo dye that were utilized in illustrating the under-study process of brown 703 degradation. The biodegradation brought about by Pseudomonas aeruginosa can be employed successfully in the future as an eco-friendly approach with far reaching results.

Combined ozone, photo, and electrocoagulation technologies-An innovative technique for treatment of distillery industrial wastewater

Electrocoagulation with ozone and photo is a hybrid electrochemical and AOP techniques used to treat wastewater and industrial effluent. In the present study, the effects of combining O3, UV, and EC processes on color removal as well as the related COD removal and EEC from the treatment of DIW were assessed. The results showed that, compared to other hybrid processes like O3/EC, UV/EC, UV/O3, and single processes of EC, O3, and UV, the combined process of O3/UV/EC is significantly more effective for treating DIW in terms of COD removal (98.99%) and complete color removal with a required EEC of 9.7 kWhr m-3. Number of process variables, including reaction time (1 to 5 hr), O3 (0.8 to 4 g L-1), UV (8 to 32 W), current density (0.08 to 0.23 A dm-2), pH (1 to 11), COD (1000 to 6000 mg L-1), inter-electrode distance (0.75 to 3.75 cm), and combination of electrodes were studied to analyze how they affected. The optimum operating circumstances underwent testing and shown outstanding effectiveness in eliminating the COD and determination of EEC from DIW. Overall, it was clear from the results that combined treatment approaches could be more effective in removing the pollutant successfully from DIW.

Imperative assessment on the current status of rubber wastewater treatment: Research development and future perspectives

The environment has been significantly impacted by the rubber industry through the release of large quantities of wastewater during various industrial processes. Therefore, it is crucial to treat the wastewater from the rubber industry before discharging it into natural water bodies. With the understanding that alarmingly depleting freshwater sources need to be preserved for future generations, this paper reviews the status of the rubber industry and the pollution caused by them, focusing mainly on water pollution. The review pays special attention to the recent advancements in wastewater treatment techniques for rubber industry wastewater categorizing them into pre-treatment, secondary, and tertiary treatment processes while discussing the advantages and disadvantages. Through a comprehensive analysis of existing literature, it was determined that organic content and NH4+ are the most frequently focused water quality parameters, and despite some treatment methods demonstrating superior performance, many of the methods still face limitations and require further research to improve systems to handle high organic loading on the treatment systems and to implement them in industrial scale. The paper also explores the potential of utilizing untreated or treated wastewater and byproducts of wastewater treatment in contributing towards achieving several United Nations sustainable development goals (UN-SDGs); SDG 6, SDG 7, SDG 9, and SDG 12.

Performance of membrane photobioreactor for integrated Spirulina strain cultivation and nutrient removal of membrane bioreactor effluent

Water reuse by wastewater treatment techniques is implemented to promote a circular economy strategy and alleviate water shortage. The microalgae-based wastewater treatment is an environmentally friendly tool to treat secondary or tertiary wastewater by removing the remaining nutrients, primarily dissolved nitrogen (N) and phosphorus (P). This research aimed to study the membrane photobioreactor (MPBR) performance to treat nitrate nitrogen (NO3-N) and phosphate (PO4) that remained in the membrane bioreactor (MBR) effluent by varying hydraulic retention times (HRTs) and solids retention times (SRTs). Bench-scale of MPBR (63 L) was continuously operated by cultivating Spirulina sp. TISTR 8875. The LED light intensity of 3000–5000 lux was provided 24 h daily. The experimental studies evaluated HRTs in the range of 6.4–9.7 days and SRTs at 20, 40, 60, and 80 days, and the microalgae cells were not removed (infinite SRT). The results showed that the HRT range of 7.7–7.8 days and SRT range of 60–80 days exhibited NO3-N and PO4 removal efficiencies of 39.3–40.9% and 43.8–46.6%, respectively, with the NO3-N and PO4 removal rates of 2.47–2.55 and 0.22–0.23 mg/L-d, respectively. In addition, iron (Fe) in the form of FeEDTA, has been added to the microalgae cultivation at a concentration of 0.07 g/L. It was found that Fe plays an essential role in the growth of microalgae and increases nutrient removal efficiency. The experimental results indicate that the cultivation of Spirulina sp. TISTR 8875 is expected to treat nutrients by the MPBR system as a promising water reuse and nutrient recovery potential.

Hybrid biofilm system based on corncob coupling with scrap iron for synergistic nitrogen removal and phosphorus recovery in low-carbon source wastewater

Low-carbon source wastewater (LCSW) challenged the nutrients removal capability of traditional wastewater treatment techniques, becoming a hidden problem of eutrophic waters. Thus, a hybrid biofilm system (HBS) was developed based on corncob coupled with scrap iron for synergistic nitrogen removal and phosphorus recovery in LCSW. Corncob provided the sustainable carbon source by hydrolyzing and fermenting coupling with dissimilatory iron reduction (DIR) process, resulting in a maximum release of over 191.2 mg/L COD and supporting nitrogen removal of 83.5 % in HBS with HRT at 6 h. Meanwhile, scrap iron supported the DIR process and chemical precipitation by Fe3+ release, generating vivianite with Fe2+ for phosphate recovery (97.1 %) in HBS. By microbial community analysis, heterotrophic denitrification was the primary process for nitrogen removal, which benefitted from hydrolyzing and fermenting bacteria. After chemical precipitation, phosphorus recovery was realized by biological solubilization and DIR process, which were functioned by Acinetobacter calcoaceticus, Bacillus aryabhattai and Bacillus sp. X12014, etc. The DIR process was the critical driving force that coupled organics degradation with synergistic removal of N and P.

A Perspective Review on Sugar Industry Wastes, Uses and Treatment Techniques

The increase in sugarcane production involves a proportional increase in sugar industry waste. As a result of such a growing trend, the sugar industry is observing severe environmental problems due to a lack of permanent solution for their waste management. Therefore, immediate consideration is needed to find suitable methods of waste management. The sugar industry waste and effluent are the main sources of environmental pollution and associated with health risks. In this paper, various sources of solids and liquids wastes from the sugar manufacturing industry are reviewed. Different effective and economical sugar industry wastewater treatment techniques are also discussed. The sources and uses of some waste like bagasse, bagasse fly ash, and pressmud have also been discussed.

Highly Efficient FeIII‐initiated Self‐cycled Fenton System in Piezo‐catalytic Process for Organic Pollutants Degradation

AbstractPiezo‐catalytic self‐Fenton (PSF) system has been emerging as a promising technique for wastewater treatment, while the competing O2 reductive hydrogen peroxide (H2O2) production and FeIII reduction seriously limited the reaction kinetics. Here, we develop a two‐electron water oxidative H2O2 production (WOR−H2O2) coupled with FeIII reduction over a FeIII/BiOIO3 piezo‐catalyst for highly efficient PSF. It is found that the presence of FeIII can simultaneously initiate the WOR−H2O2 and reduction of FeIII to FeII, thereby enabling a rapid reaction kinetics towards subsequent Fenton reaction of H2O2/FeII. The FeIII initiating PSF system offers exceptional self‐recyclable degradation of pollutants with a degradation rate constant for sulfamethoxazole (SMZ) over 3.5 times as that of the classic FeII‐PSF system. This study offers a new perspective for constructing efficient PSF systems and shatters the preconceived notion of FeIII in the Fenton reaction.

Highly Efficient Fe(III)-initiated Self-cycled Fenton System in Piezo-catalytic Process for Organic Pollutants Degradation.

Piezo-catalytic self-Fenton (PSF) system has been emerging as a promising technique for wastewater treatment, while the competing O2 reductive hydrogen peroxide (H2O2) production and Fe(III) reduction seriously limited the reaction kinetics. Here, we develop a two-electron water oxidative H2O2 production (WOR-H2O2) coupled with Fe(III) reduction over a Fe(III)/BiOIO3 piezo-catalyst for highly efficient PSF. It is found that the presence of Fe(III) can simultaneously initiate the WOR-H2O2 and reduction of Fe(III) to Fe(II), thereby enabling a rapid reaction kinetics towards subsequent Fenton reaction of H2O2/Fe(II). The Fe(III) initiating PSF system offers exceptional self-recyclable degradation of pollutants with a degradation rate constant for sulfamethoxazole (SMZ) over 3.5 times as that of the classic Fe(II)-PSF system. This study offers a new perspective for constructing efficient PSF systems and shatters the preconceived notion of Fe(III) in the Fenton reaction.

Emerging contaminants in conventional and advanced biological nutrient removal based wastewater treatment plants in India- insights into the removal processes

Emerging contaminants (ECs) in the environment are a cause of concern due to their potential toxic effects. The study investigates the fate of 20 ECs covering a wide range of physical-chemical properties in ten full-scale municipal wastewater treatment plants (WWTPs). The plants were based on conventional technologies such as waste stabilization pond, upflow sludge blanket reactor, activated sludge process, and biological nutrient removal-based technologies such as anoxic-aerobic process, anaerobic-anoxic-aerobic process, biodenipho process, sequencing batch reactor, and densadeg-biofor process. Covering all the wastewater and sludge treatment lines, the mass balance approach was followed to investigate the fate of ECs at each treatment stage. The amount of ECs entering and leaving the WWTPs ranged from 0.82 to 11.94 kg/day and 0.027 to 0.70 kg/day, respectively. Antibiotics showed limited removal and were detected in the 0.006 to 0.18 kg/day range. The ECs were mainly detected in the aqueous phase in all the treatment steps. However, the contribution from the particulate and sludge phase cannot be neglected. The sorption of ECs on sludge depended on the sludge's characteristics. It was found to be the highest in the primary sludge. The measured sorption coefficient indicated that both hydrophobic and electrostatic interactions of ECs with the sludge are insufficient in explaining the sorption behaviour of a contaminant. The mass balance studies show biodegradation as the major removal pathway in all the WWTPs. The study provides the environmental mass load of ECs from Indian WWTPs. It will help understand the removal mechanisms of ECs in different types of wastewater treatment techniques.

Thermodynamics, kinetics and isothermal studies of tartrazine adsorption onto microcline/MWCNTs nanocomposite and the regeneration potentials

The quest for a cheap, effective, and eco-friendly wastewater treatment technique that is free of secondary toxic byproducts, calls for the fabrication of a nature-friendly adsorbent with a robust capacity to decontaminate polluted water sources and be recycled. To this end, we report the fabrication of novel nanocomposite (KMCM) from microcline (KMC) and multiwall carbon nanotubes (MWCNTs). The adsorbents (KMC and KMCM) were characterized using XRD, BET, SEM, TGA and FTIR. The novel and low-cost nano sorbent were designed for the elimination of tartrazine (Tatz) from wastewater. The adsorption of Tatz onto KMC and KMCM was influenced by adsorbent dose, initial Tatz concentration, contact time and solution pH. Experimental data acquired from the equilibrium studies were well addressed by the Langmuir isotherm model. The maximum uptake capacity of 37.96 mg g−1 and 67.17 mg g−1 were estimated for KMC and KMCM. The kinetics for the adsorption of Tatz onto KMC and KMCM was best expressed by pseudo-second-order and Elovich models. The thermodynamic parameters revealed that the uptake of Tatz onto KMC and KMCM was an endothermic (ΔH: KMC = 35.0 kJ mol−1 and KMCM = 42.91 kJ mol−1), entropy-driven (ΔS: KMC = 177.6 J K−1 mol−1 and KMCM = 214.2 J K−1 mol−1) and spontaneous process. Meanwhile, KMCM demonstrated good reusability potential and superior adsorption efficiency when compared to other adsorbents.

Activation of sodium percarbonate by micro amounts of copper for highly efficient degradation of acid orange 7

In recent years, activation of sodium percarbonate (SPC) has been regarded as very appealing technologies in the elimination of organic pollutants. In this work, the activation of SPC using micro amounts of Cu(II) (at μM level) towards acid orange 7 (AO7) degradation was explored. Experimental results displayed that nearly 97.5% of AO7 could be removed within 15 min using 20 µM Cu(II) and 0.4 mM SPC. Effects of Cu(II) concentration, SPC concentration, pH value and coexisting anions were investigated. Compared with conventional Fenton oxidation, which could only work under acidic pH conditions, Cu(II)-catalyzed SPC (Cu(II) /SPC) system could work under near-neutral or alkaline solutions. Furthermore, AO7 decomposition was barely impacted by Cl−, SO42− and NO3−, while 5 mM HCO3− inhibited the degradation of AO7. Electron paramagnetic resonance analysis confirmed the existence of multiple reactive oxygen species in the reaction (HO•, O2•–, 1O2). However, free radical scavenging experiments demonstrated that the degradation of AO7 was mainly due to the carbonate radicals (CO3•−) and singlet oxygen (1O2). The interaction between Cu(I) and Cu(II) was confirmed and the production of Cu(III) was proved to act as a degradation agent for AO7. The degradation of AO7 could be divided into two pathways. The study suggests a simple, economic and efficient technique for dye wastewater treatment using SPC triggered by micro-amount Cu(II).

Exploring the resilience of constructed wetlands to harmful algal blooms disturbances: A study on microbial response mechanisms

Constructed wetlands (CWs) have emerged as a promising environmentally sustainable technique for wastewater treatment. However, the susceptibility of CWs to disturbances caused by harmful algal blooms (HABs) raises concerns. This study aimed to investigate the impact of HABs on the pollutants’ removal performance of CWs and the response of rhizosphere microbial community. Results revealed that CWs possessed an adaptive capacity that enabled them to recover caused by HABs. The rhizosphere was found to stimulate the occurrence of Acinetobacter, which played a critical role to help resist HABs disturbance. This study also observed an increased dissimilatory nitrate reduction metabolic pathway which promoted denitrification and enhanced the nitrogen removal efficiency of CWs. Additionally, the structural equation model further suggested that dissolved oxygen exerted a significant influence on the microbial activities and then affected the pollutants removal performance. Overall, our findings shed light on the mechanism for CW stability maintenance during HABs disturbance.