Wastewater Treatment Research Articles

Predicting the removal efficiency of titanium dioxide nanoparticles in an activated sludge system using fate modeling depending on the operating conditions

Wastewater treatment plants (WWTPs) are a major discharge pathway for engineered nanoparticles (ENPs) that can potentially impact aquatic systems, making it crucial to understand ENP behavior in these facilities. In this study, we developed a fate model for titanium dioxide (TiO2) nanoparticles (NPs) to predict their removal efficiency (RE) in activated sludge (AS) systems. The model, based on material balance equations for free and sludge-attached TiO2 NPs, incorporated a linear-adsorption partition coefficient (Kd) and pseudo-second-order kinetics for TiO2 NP attachment to the activated sludge. Validated with data from three WWTPs, the model investigated RE correlations with inflow TiO2 NP concentration, sludge retention time (SRT), hydraulic retention time (HRT), mixed liquor suspended solid (MLSS) concentration, and water temperature. The model reasonably predicted the comparative performance of the WWTPs but underestimated the RE by up to ∼29 %, probably due to system simplification, limited Kd data, the presence of other Ti-containing NPs besides TiO2 NPs, and unincorporated removal mechanisms such as sweeping in the secondary clarifier. The model revealed favorable design/operating conditions for increasing the TiO2 NP RE of the AS system: shortening the SRT, increasing the MLSS concentration, and increasing the water temperature. The developed model could be useful for estimating and comparing the expected TiO2 NP REs across different WWTPs under varying operating conditions or for tracing the material flow and fate of TiO2 NPs in environmental compartments involving WWTPs, both regionally and country-wide.

Towards Achieving Circular Economy in the Production of Silica from Rice Husk as a Sustainable Adsorbent

The growing concern over water pollution and waste management requires innovative solutions that promote resource efficiency within a circular economy. This study aims to utilize rice husk (RH) as a sustainable feedstock to develop highly porous silica particles and generate valuable by-products, addressing the dual challenges of waste reduction and water contamination. We hypothesize that optimizing the production of amorphous silica from acid-washed RH will enhance its adsorptive properties and facilitate the concurrent generation of bio-oil and syngas. Amorphous silica particles were extracted from acid-washed RH with a yield of 15 wt% using a combination of acid washing at 100 °C, pyrolysis at 500 °C, and calcination at 700 °C with controlled heating at 2 °C/min. The optimized material (RH2-SiO2), composed of small (60–200 nm) and large (50–200 µm) particles, had a specific surface area of 320 m2/g, with funnel-shaped pores with diameters from 17 nm to 4 nm and showed a maximum cadmium adsorption capacity of 407 mg Cd/g SiO2. Additionally, the pyrolysis process yielded CO-rich syngas and bio-oil with an elevated phenolic content, demonstrating a higher bio-oil yield and reduced gas production compared to untreated RH. Some limitations were identified, including the need for bio-oil upgrading, further research into the application of RH2-SiO2 for wastewater treatment, and the scaling-up of adsorbent production. Despite the challenges, these results contribute to the development of a promising adsorbent for water pollution control while enhancing the value of agricultural waste and moving closer to a circular economy model.

Electrocatalysis coupled super-stable mineralization for the efficient treatment of phosphorus containing plating wastewater

The automotive, electronics, and aerospace sectors use electroless nickel plating (ENP) technology for surface treatment. Hypophosphite, a widely used reducing agent in ENP, generates large volumes of hypophosphate (H2PO2-) and nickel ions (Ni2+) in its wastewater which poses potential risks to human health. However, it is a highly challenging task to remove and recycle the H2PO2- and Ni2+ from such wastewater. In this study, a novel electrocatalysis coupled super-stable mineralization process was developed for the treatment of phosphorus-containing ENP wastewater. The electrocatalytic system, utilizing commercial lead dioxide and stainless steel as the anode and cathode, separately, achieved remarkable results in simultaneously removing H2PO2- and recycling valuable Ni2+ ions from ENP wastewater, with a 99.1 % oxidation efficiency for H2PO2- and a high recovery rate of 99.8 % for nickel. In order to meet industrial emission standards, layered double hydroxide (CaAl-LDH) and its calcined derivatives (CaAl-900) were employed as super-stable mineralizers for the further treatment of total phosphorus (TP) and residual Ni2+ in the wastewater. The mechanism underlying the enhanced treatment of ENP wastewater was elucidated through free radical quenching experiments, revealed superoxide radicals (·O2–) as the primary active species. It is noteworthy that the successful treatment of actual ENP wastewater was achieved, meeting standard discharge requirements. This study provides novel insights for achieving resource-efficient wastewater treatment and promoting environmentally friendly electroplating industries.

Associative analysis of sludge microbiota and wastewater degradation efficacy within swine farm sludge systems

Industrial wastewater management is a significant global challenge. Sludge microbiota from swine farms may play a crucial role in enhancing wastewater treatment processes, thereby reducing water pollution from industrial activities. A deeper understanding of this complex community could lead to innovative approaches for improving wastewater treatment methods. Sludge samples were collected from the anaerobic, sedimentation, and thickening tanks of ten swine farms. The microbiota communities were analyzed using 16S rRNA full-length sequencing on the PacBio platform, with subsequent data analysis conducted on the QIIME2 platform utilizing the SILVA database. Compared to anaerobic and thickening tanks, the sedimentation tanks exhibited a unique profile of sludge microbiota, with higher abundances of the phyla Proteobacteria, Bacteroidota, and Caldatribacteriota. Additionally, sludges from farms already utilized in processing industrial water—specifically farms B, G, and J—contained higher concentrations of bacteria (> 20 ng/μL), indicating the robustness of the bacterial load for practical industrial use. Furthermore, sludge from farms with higher alpha diversity, such as E, G, I, and J, exhibited enriched degradation profiles, including the degradation of aromatic compounds, polymers, industrial compounds, toluene, and vanillin. The farms were categorized based on wastewater ammonia nitrogen degradation levels, revealing a clustering effect of the microbiota from the sedimentation tanks in the Principal Coordinates Analysis (PCoA) plot. A higher relative abundance of the families Rhodocyclaceae, AKYH767, and Comamonadaceae, and a lower abundance of the families Anaerolineaceae and Christensenellaceae, were found in groups with high ammonia nitrogen reduction, suggesting potential targets for bioaugmentation strategies. In conclusion, this study underscores the critical role of microbial abundance, composition, and biodiversity in optimizing wastewater treatment and advocates for comprehensive microbiota analysis to identify suitable sludge for industrial applications.

An enzyme-fused phycobiliprotein synthesis system developed for visual whole-cell biosensors for the detection of cadmium during wastewater treatment

Transcription factor-based whole-cell biosensors are simple and inexpensive tools for monitoring heavy metals during environmental processes. However, most biosensors are depend on instrumentation or have low sensitivity. Here, all the enzymes in the phycobiliprotein synthesis system were fused with the phycocyanin apoprotein to create a system to synthesize enzyme-fused phycobiliproteins with comparable fluorescence. We replaced the biliprotein synthesis system T7 promoter with cadmium-sensing genetic elements to create two visual cadmium biosensors (Epcad-cbsA and Epcad-cbsS). Cd2+ was detected at nanomolar concentrations by measuring the fluorescence intensity and evaluating the degree of color change of the cell pellets. Moreover, good linear correlations were observed with Cd2+ concentrations up to 250nM. Compared with cellular fluorescence, our cadmium biosensor is more sensitive when cell color is used as the output signal, with detection limits of 7.6nM for Epcad-cbsA and 3.2nM for Epcad-cbsS. This visual platform was validated by assessing bioavailable cadmium during wastewater treatment. By immobilizing large amounts of phycobilin with the proteins in cells, our designed biosensors do not require pigment extraction or specialized light sources or detection devices. This work demonstrates that a biliprotein synthesis system can be a novel platform for the development of simple, low-cost, and highly sensitive visual biosensors for real-world applications.

Efficient removal of nitrate and ammonium by strain Pseudomonas poae EH-E3 under acidic pH and low-temperature conditions

The combined effect of low temperature and an acidic environment may restrict the growth and metabolic activity of microorganisms involved in nitrogen removal. To overcome poor biological nitrogen removal efficiency during low-temperature treatment of acidic wastewater, a novel pure strain of Pseudomonas poae EH-E3 was successfully isolated and screened based on its strong heterotrophic nitrification and aerobic denitrification capacity. Strain EH-E3 could completely eliminate inorganic nitrogen sources of nitrate within 30h and ammonium within 20h at 15 °C and pH 5.0, with corresponding removal efficiencies for total nitrogen of 95.13% and 91.35%, respectively. Nitrogen balance testing indicated that strain EH-E3 removed 43.25% of ammonium, 45.72% of nitrate, and 51.20% of nitrite in the form of gaseous products. Enzyme activity assays revealed that the specific activities of ammonia monooxygenase, nitrate reductase, and nitrite reductase were 0.533, 0.956, and 0.011 U/mg proteins, respectively. These findings suggest that strain EH-E3 has strong potential for use in low-temperature treatment of acidic wastewater.

Aerobic granular sludge enhances start-up and granulation in single-stage partial nitritation anammox granular sludge systems: Performance, mechanism, and shifts in bacterial communities

The rapid start-up and granulation of a single-stage partial nitritation anammox granular sludge (PN/AnGS) system under limited seed sludge conditions is crucial for its practical application. This study proposed an aerobic granular sludge (AGS) − based strategy, enhanced the enrichment of anammox bacteria (AnAOB), and shortened the start-up time of PN/AnGS system by 20.5%. In addition, the inoculation of AGS can ensure the stable operation of the system during the selective sludge discharge to washout the flocs. Microbial community structure, particle size distribution, morphology results showed that niche shift was the key to promote the enrichment of AnAOB and AGS played a decisive role in the particle characteristics of PN/AnGS. Since AGS can be directly obtained from full-scale AGS wastewater treatment plants, integrating PN/AnGS with AGS processes can transition wastewater treatment from a “linear economy” to a “circular economy”, enhancing nitrogen removal efficiency and delivering significant economic and environmental benefits.

Consequential life cycle assessment of urban source-separating sanitation systems complementing centralized wastewater treatment in Lund, Sweden

This study examined various source-separating sanitation systems to evaluate their environmental performance, providing decision-makers with insights for selecting an appropriate system for a newly developed neighborhood in Sweden. A full consequential LCA was conducted to account for resource recovery and substitution. The local wastewater treatment plant WWTP was modeled as a reference. Secondly, a urine recycling system was introduced to treat 75% of the collected urine, with the remainder piped to the WWTP. Thirdly, a black and greywater (BW&GW) treatment system handling all generated wastewater was examined. Finally, a hybrid source-separating system combining urine, black, and greywater was investigated. The results indicated that the four scenarios exhibited global warming potentials (GWP) of 78, 62, 32, and 24 kg CO2-eq per PE/ y. Recycling urine as fertilizer led to a 20% reduction in the GWP of the reference. It also reduced other impact categories, with a 55%, 65%, and 45% reduction in eutrophication, ozone depletion, and acidification, respectively. The BW&GW system achieved a 60% reduction over the reference GWP, mainly due to fertilizer, biogas, and cleanwater recovery. Integrating urine, black, and greywater recycling in the final scenario achieved a 25% reduction compared to the BW&GW scenario, primarily due to lowering of the ammonia stripping GWP and the additional fertilizer recovery. Based on sensitivity analyses, switching citric acid for sulfuric acid reduced the GWP of the urine stabilization unit process by 101%, from 15.47 to -0.14 kg CO2-eq per PE/ y. Ultimately, the findings suggest that the fully decentralized source-separating sanitation system incorporating urine, blackwater, and greywater recycling, particularly when combined with 70% energy recovery at the urine concentrator, is most favorable.

Clean energy production and wastewater treatment by Exophiala dermatitidis: first findings

A single-chamber microbial fuel cell (MFC) was constructed to evaluate the capacity of Exophiala dermatitidis EXF-8193 as an electron-donor microorganism. The working electrodes were made of unidirectional carbon fiber and the voltage generation was evaluated for 120h. The maximum voltage value reached was 176mV after 93hours of operation. At the same time, the degradation of the Basic Blue 9 (BB9) was studied and a 70% decolorization was achieved in 120h. Optimization studies were conducted to maximize the electrical energy produced. In the first stage, the individual influence of the variables: carbon source, shape and area of the anode was analyzed. It was obtained that glucose, a T-shaped anode and an anodic area of 12 cm2 provided the best voltage values, generating 175.8 ± 0.57mV, 175.8 ± 0.57mV and 310.53 ± 1.22mV, respectively. In the second stage of the investigation, multiparametric optimization was carried out using the Response Surface Methodology (RSM) with a Box Behnken experimental design. A second-order model was the best fit, with R2 = 91.7. Finally, the MFC operation was optimized, with 284mV being the most favorable voltage when the cell is operated maintaining the optimal conditions for each parameter.

Amino acid functionalized carboxymethyl cellulose-based crosslinked aerogels for efficient removal of dye and metal ion from aqueous solution

In order to protect water resources and maintain sustainable development of society, it is crucial to design the adsorption materials with high adsorption capacity and environmental friendliness to effectively remove the pollutants in wastewater. In this study, amino acid functionalized carboxymethyl cellulose-based aerogels were successfully prepared by combining grafting, blending, freeze-drying and crosslinking technologies. The aerogels exhibited outstanding adsorption properties for methylene blue (MB) and lead ions (Pb (II)) with adsorption capacities of 461.68 and 304.60 mg/g, respectively. The adsorption experiment showed that the adsorption process of aerogels for MB conformed to Freundlich adsorption isotherm model and quasi-second-order kinetics model, and the adsorption process for Pb (II) conformed to Langmuir model and quasi-second-order kinetics model. Furthermore, the aerogels displayed excellent recyclability, with the removal efficiency of over 90.0 % for MB and only 14.0 % reduction for Pb (II) after 6 cycles. It is evident that the aerogels hold great potential for application in wastewater treatment, which has important practical significance for environmental protection and high-value utilization of natural polymers.

Proactive Monitoring of Changes in the Microbial Community Structure in Wastewater Treatment Bioreactors using Phospholipid Fatty Acid Analysis

Diverse microbial community structures (MCS) in wastewater treatment plants (WWTPs) are vital for effectively removing nutrients and chemicals from wastewater. However, the regular monitoring of MCS in WWTP bioreactors remains unattractive owing to the skill and cost required for deploying modern microbial molecular techniques in the routine assessment of engineered systems. In contrast, low-resolution methods for assessing broad changes in the MCS, such as phospholipid fatty acid (PLFA) analysis, have been used effectively in soil studies for decades. Despite using PLFA analysis in soil remediation studies to capture the long-term effects of environmental changes on MCS, its application in WWTPs, where the microbial mass is dynamic and operational conditions are more fluid, remains limited. In this study, microbial communities in a controlled pilot plant and 12 full-scale activated sludge plants (ASPs) were surveyed over a two-year period using PLFA analysis. This study revealed that changes in the MCS in wastewater bioreactors could be detected using PLFA analysis. The MCS comprised 59% Gram-negative and 9% Gram-positive bacteria, 31% fungi, and 1% actinomycetes. The abundances of Gram-negative bacteria and fungi were strongly inversely correlated, with an R2 = 0.93, while the fatty acids cy17:0 and 16:1ω7c positively correlated (R2 = 0.869). Variations in temperature, solid retention time, and WWTP configuration significantly influenced the MCS in activated sludge reactors. This study showed that WWTP bioreactors can be routinely monitored using PLFA analysis, and changes in the bioreactor profile that may indicate imminent bioreactor failure can be identified.

Evaluation of titanium dioxide/catechol polyurethane composite for antimicrobial resistance and wastewater treatment

In this study, a novel approach for the environmentally conscious extraction of titanium dioxide from ilmenite ore while limiting the environmental impact and enhancing the advantage from an economic process. Leaching conditions were tested with different acids for effective separation of the TiO2 and were optimized concerning different experimental parameters. TiO2 and TiO2NPs were characterized using with different tools. Catechol polyurethane foam immobilized with TiO2NPs was prepared and its antimicrobial action was tested against Gram-negative bacterium E. coli, Gram-positive bacterium B. cereus, and fungus A. niger. CAT-PUF /TiO2NPs showed antimicrobial effect against E. coli, B. cereus, and A. niger with inhibition zones of 27 ± 0.14, 12 ± 0.14, and 22 ± 0.06 mm, respectively. Incorporating bioinformatics, this research contributes to the burgeoning field of nanotechnology-enabled antimicrobial materials, offering insights into the potential applications of CAT-PUF/TiO2NPs in combating microbial threats. Through bio-informatics tools, the potential toxicity of the synthesized nanoparticles was assessed, providing valuable insights into their safety profile and environmental impact. Furthermore, simulating the binding affinity between the nanoparticles and target biomolecules, such as cell membrane proteins or enzyme receptors, this aspect of the research sheds light on the mechanistic underpinnings of their antimicrobial efficacy.

Photocatalyst for Antibiotics Degradation by In Situ Growth of Direct Z-Type Bi2S3/Bi4Ti3O12 Heterojunction.

Effective removal of antibiotics from aqueous solutions has emerged as a hot research topic in wastewater treatment. Photocatalytic degradation of antibiotics is one of the most effective methods to reduce ecological damage and environmental pollution. In this work, a novel photocatalyst consisting of Z-type heterojunction Bi2S3/Bi4Ti3O12 (BS/BTO) with visible light responses was prepared by an in situ growth method, and the obtained material was used for the degradation of tetracycline hydrochloride (TC). The best performing photocatalyst was BS/BTO-2, which exhibited high photocatalytic activity. The rates of TC degradation reached 97.9% within 40 min of illumination. The photocatalyst demonstrated a high stability and reproducibility even after 5 cycles. Electron spin resonance (EPR) tests and quenching experiments established that ·O2- and h+ were the main species responsible for the elimination of TC. On the basis of theoretical calculations and experimental data, a possible mechanism for the photocatalytic degradation of TC has been proposed. The heterojunction structure, which effectively increases the visible light absorption range and decreases the compounding efficiency of photogenerated electrons and holes, is principally responsible for the photocatalytic performance of BS/BTO. Additionally, liquid chromatography-mass spectrometry (LC-MS) was utilized to investigate the formation and degradation of reaction intermediates. The nontoxicity of the solution after tetracycline degradation was verified by cultivating wheat seeds. This work offers guidance for bismuth-based photocatalysts in the field of sustainable wastewater treatments.

Integrated urban wastewater management through on-site generation and application of ferrous carbonate

Integrated urban water management is an increasingly popular concept that cost-effectively maximizes system-wide performance by holistically considering all aspects of water and wastewater sectors. An innovative technology enabling production of high-quality bioenergy and an iron salt, ferrous carbonate (FeCO3), represents a significant opportunity for integrated urban water management. This study experimentally evaluates the effect of in-sewer FeCO3 dosing on the performance of sewers and the downstream wastewater treatment plants. Two continuous-flow laboratory-scale urban wastewater systems, each consisting of sewer reactors, a sequencing batch wastewater treatment reactor, and an anaerobic digester, were operated in parallel. After establishing comparable performance, one served as the control without any chemical dosing, while the other received a dosing of 10mgFe/L of FeCO3 in its sewer reactors. Compared to the control, the FeCO3-dosed experimental system reduced dissolved sulfide concentrations by 32.2±3.3% (at 0.58±0.05mgS/mgFe, or 1.0molFe/molS) in sewer reactors, decreased phosphate concentrations by 38.3%±3.2% (at 0.37±0.04mgP/mgFe, or 1.5molFe/molP) in sequencing batch reactors, and lowered dissolved sulfide concentrations by 72.0±4.2% (18.9±2.4mgS/L) in the anaerobic sludge digester. Iron accumulated in the sludge and improved sludge settleability by 33.9±5.5% and enhanced dewaterability of anaerobically digested sludge by 15.9±2.0%. The findings indicate multiple benefits from the integrated use of FeCO3, potentially being as a substitute for the currently used iron salts in urban wastewater systems.

Chemical characterization of activated carbon derived from Napier grass, rubber wood, bamboo, and hemp

This study examines the process and analysis of activated carbons that use H2SO4, H2O2, and NaOH as activating agents. The distinct chemical methods employed by each activator impacted the ash and carbon content, surface properties, and functional groups of the activated carbons, exhibiting notable disparities. The ash level varied from 6.86% to 37.08%. H2SO4-activated carbons had the lowest ash content, suggesting better elimination of inorganic contaminants. The iodine number, which serves as a measure of adsorption capacity, was consistent among all samples, with values ranging from 800 to 950 mg g-1. This indicates that the three activating agents effectively increased the surface area and porosity. The BET surface areas varied between 9.14 and 167.42 m2 g-1, whereas the BJH adsorption surface areas ranged from 9.68 to 28.89 m2 g-1. The pore volumes ranged from 0.0071 to 0.0595 cm2 g-1, while the sizes ranged from 0.51 to 8.2 nm. These measurements suggest the presence of both micropores and mesopores. The FTIR spectra exhibited comparable functional groups among all samples, such as OH, CH, C=C, and C-O. The SEM-EDX and XPS tests showed that there was a lot of carbon. The carbon content was highest in H2O2-activated carbons because they were exposed to less severe oxidative conditions. These activated carbons comply with the requirements set by IUPAC and ASTM. They are suitable for catalytic processes and liquid adsorption, such as water and wastewater treatment. Subsequent research should aim to improve activation conditions to get the highest possible carbon content and optimise surface characteristics.

Developing PVDF hollow fiber membrane enhanced by braided tube and modified by bionic coating for treating aldehyde-containing wastewater

This study originates from the difficulties encountered in the wastewater treatment from a large-scale methionine production line. Despite the superior performance of the polytetrafluoroethylene (PTFE) membrane, significant issues still persist. The PTFE layer tend to peer off leading to substandard effluent quality, and membrane fouling rate is relatively rapid. To overcome the peeling issue, braided tubes were used to enhance the mechanical strength. To improve the interface bonding between the PVDF layer and braided tubes, two modifiers are introduced to modify the surfaces of braided tubes. Then, the embedded braided tube enhanced PVDF membrane is prepared. On this basis, the one-step bionic coating PVDF (OSBC-PVDF) membrane was prepared by utilizing the polydopamine coating, polyethylene glycol and Cu nanoparticles. It was found that the embedded structure resembling “teeth and gums” formed, significantly improving the mechanical properties to prevent the peeling off of the separation layer. The optimal reaction temperature, reaction time and modifier dosage for preparing the OSBC-PVDF membrane are separately 25 °C, 2 h and 20 g. More importantly, the OSBC-PVDF membrane has withstood the test of 300 days of continuous operation. The stable water quality of the effluent demonstrated that the above issues had been overcome.

Evaluation of large-scale poultry manure-derived biochar for efficient cadmium removal in zinc smelter wastewater

Cadmium (Cd), a carcinogen, is released from industrial activities like metal refineries and battery runoff, with significant contamination reported near zinc smelters in Korea. This study addresses the issue using an efficient, economical adsorption process with waste-derived biochar-based adsorbents known for high Cd removal. Poultry manure (PM), typically used as fertilizer, can lead to environmental pollution if mismanaged; therefore, it was pyrolyzed to produce biochar. The resulting poultry manure biochar (PMBC) was produced on a large scale (15 ton/day), demonstrating feasibility for large-scale implementation. The effectiveness of PMBC as an adsorbent for Cd was evaluated using wastewater discharged from a zinc smelter. The Cd adsorption capacity of PMBC (60.39 mg/g) was lower than that (302.0 mg/g) of hen manure biochar produced at a laboratory scale in our previous study but was comparable to other biochars reported in the literature. Response surface methodology analysis indicated that reaction time, dose, and agitation significantly influenced Cd removal by PMBC, whereas pH had a negligible impact. Notable contributions to Cd adsorption include the release of K+ from PMBC and the presence of O-containing functional groups. Under continuous flow conditions with real wastewater, Cd was not detected in the effluent for the initial 8 h, and PMBC sustained a removal efficiency of 40.77% until saturation was reached. The results from wastewater treatment and large-scale biochar production offer valuable insights into the potential of biochar as a medium for addressing environmental issues in real-world applications.

Ion-exchange formation of Ag2CO3-Ag3PO4 binary nanostructure on electrospun polyurethane nanofibers for enhanced photocatalytic degradation and antibacterial activities

In this study, a hybrid Ag2CO3-Ag3PO4/PU NFs membrane was prepared by electrospinning followed by ion-exchange methods. The obtained samples were characterized by SEM, EDS, XRD, and IR techniques. The Ag2CO3-Ag3PO4/PU NFs membrane composite exhibited excellent photocatalytic performance (100 % of the dye removal within 70 min) towards the degradation of methylene blue (MB) under visible light irradiation. This remarkable performance was mainly due to the efficient separation of the photogenerated charge carriers. In addition, the composite showed good antibacterial performance against Salmonella typhimurium and Staphylococcus aureus. The results obtained from the photocatalytic and antibacterial studies showed that the prepared material can be proposed as a multifunctional material in wastewater treatment and environmental applications.

Efficient activation of peroxyacetic acid by cobalt-iron alloy/oxide heterojunctions anchored in defect-rich biochar for pesticide degradation in water: Unravelling the radical-unradical mechanism

The activation processes of peracetic acid (PAA-AOPs) have garnered significant attention in wastewater treatment. In this study, an amorphous carbon-modified bimetallic CoFe alloy/oxide catalyst (CoFe@DBCx-y, where x represents biomass mass and y represents pyrolysis temperature) was developed to activate PAA for the degradation of organochlorine pesticides (OCPs). Due to the size effect, biochar dynamically regulates the particle size of metal species, which is influenced by the pyrolysis temperature. Among these systems, the CoFeDBC2.0–700/PAA oxidation system effectively removed 95.7 % of 2,4-dichlorophenoxyacetic acid (2,4-D), exhibiting a kinetic constant 1.7 times higher than that of the Nano/PAA system. Furthermore, quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that high-valent metal oxides (MIV = O) and singlet oxygen (1O2) are the primary active species responsible for the removal of 2,4-D, whereas organic radicals (RO·) and hydroxyl radicals (·OH) play a secondary role. Electrochemical and Raman spectroscopy tests revealed the formation of a metastable surface complex (≡Co(III)–OO(O)CCH3) between PAA and the catalyst, which acted as an intermediate oxidant to generate reactive oxygen species (ROS) through a chain reaction. Carbon defects in the biochar functioned as an electron source, continuously replenishing the electrons consumed in the reaction and facilitating the valence cycling between Co and Fe. This study provides new insights into the remediation of pesticide-contaminated wastewater using PAA-AOPs with heterogeneous bimetallic carbon-based catalysts.

Performance of a pilot-scale microbial electrolysis cell coupled with biofilm-based reactor for household wastewater treatment: simultaneous pollutant removal and hydrogen production.

The septic tank is the most commonly used decentralized wastewater treatment systems for household wastewater treatment in on-site applications. The removal rate of various pollutants is lower in different septic tank configurations. The integration of a microbial electrolysis cells (MEC) into septic tank or biofilm-based reactors can be a green and sustainable technology for household wastewater treatment and energy production. In this study, a 50-L septic tank was converted into a 50-L MEC coupled with biofilm-based reactor for simultaneous household wastewater treatment and hydrogen production. The biofilm-based reactor was integrated by an anaerobic packed-bed biofilm reactor (APBBR) and an aerobic moving bed biofilm reactor (aeMBBR). The MEC/APBBR/aeMBBR was evaluated at different organic loading rates (OLRs) by applying voltage of 0.7 and 1.0V. Result showed that the increase of OLRs from 0.2 to 0.44kg COD/m3 d did not affect organic matter removals. Nutrient and solids removal decreased with increasing OLR up to 0.44kg COD/m3 d. Global removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), ammoniacal nitrogen (NH4+), total phosphorus (TP) and total suspended solids (TSS) removal ranged from 81 to 84%, 84 to 85%, 53 to 68%, 88 to 98%, 11 to 30% and 76 to 88% respectively, was obtained in this study. The current density generated in the MEC from 0 to 0.41 A/m2 contributed to an increase in hydrogen production and pollutants removal. The maximum volumetric hydrogen production rate obtained in the MEC was 0.007 L/L.d (0.072 L/d). The integration of the MEC into biofilm-based reactors applying a voltage of 1.0V generated different bioelectrochemical nitrogen and phosphorus transformations within the MEC, allowing a simultaneous denitrification-nitrification process with phosphorus removal.