Real Wastewater Treatment Research Articles

Gravity-driven composite cellulose acetate/activated carbon aluminium-based hydrogel membrane for landfill wastewater treatment

A composite cellulose acetate (CA) carbon-based aluminium hydroxide (CACG) hydrogel membrane was prepared for water purification and real leachate wastewater treatment. The composite CACG hydrogel structure was characterized using scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Initially, the study investigated the efficiency of the composite CACG hydrogel membrane in removing divalent ions such as Cu2+, Pb2+, Mg2+, and Ca2+ at 10 mg/L and 1000 mg/L concentrations from synthetic feed solutions. The results revealed that metal ions removal efficiency was higher at 10 mg/L feed concentration. The composite CACG hydrogel membrane demonstrated high selectivity for Cu2+ and Pb2+ ions, with more than 99% removal from the solution. The performance of the CACG hydrogel was evaluated in four cycles with a constant metal ions removal efficiency of over 98%. These findings suggest composite hydrogel could be a promising adsorbent material for removing metal ions from synthetic water and wastewater. The total suspended solids (TDS) were reduced by 58%. Additionally, the concentrations of arsenic (As3+), lead (Pb2+), zinc (Zn2+), copper (Cu2+), nickel (Ni2+), Manganese (Mn2+), Magnesium (Mg2+), Potassium (K+), Calcium (Ca2+), and Sodium (Na+) saw reductions of 99.9%, 98.3%, 96%, 96%, 99.6%, 93%, 74.75%, 73.6, 60%, and 14.9% respectively.

Application of machine learning algorithms and feature selection methods for better prediction of sludge production in a real advanced biological wastewater treatment plant

Although the management of sewage sludge is an important and challenging task of wastewater treatment, there is a scarcity of studies on the prediction of waste sludge. To overcome this deficiency, the present work aims to develop an appropriate model providing accurate and fast prediction of sewage sludge. With this aim, different machine learning (ML) algorithms were tested by data obtained from a real advanced biological wastewater treatment plant located in Kocaeli, Turkey. In modelling studies, a data set from January 2022 to December 2022 composed of 208 daily measurements was considered. The flow rate of the plant (Q), polyelectrolyte dosage (PD) and removed amounts of total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), total phosphorous (TP), total nitrogen (TN) were assigned as input parameters to predict sludge production (SP). The precision of the models was evaluated in terms of Mean Square Error (MSE), Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and correlation coefficient (R2). Among the various tested models Kernel Ridge Regression provided the best accuracy with R2 value of 0.94 and MAE value of 3.25. Mutual information-based feature selection (MIFS) and correlation-based feature selection (CFS) algorithms were also used in the study in order to enhance the model performance. Thus, higher prediction accuracies were achieved using the selected subset of features. Furthermore, importance contribution of features were calculated and visualized by SHapley Additive exPlanations (SHAP) technique. The overall results of the work indicate the feasibility of ML models for describing the dynamic and complex nature of SP. The process operators may benefit from this modelling approach since it enables accurate and fast estimation of sewage sludge by using fewer and easily measurable parameters.

A novel cost-effective flow-through electrode based on polyacrylonitrile carbon fiber for enhancing micropollutant degradation via electro-Fenton

Electrochemical filtration is an effective technology for treating the wastewater that containing low-concentration organic micropollutants. However, its practical application has been hindered by the lack of feasible flow-through electrodes. Herein, a physically assembled flow-through cathode, based on commercial polyacrylonitrile-based (PAN) carbon fiber (CF), was introduced in an electro-Fenton (EF) system. The conductive filtration element, created by coiling the FeOCl-functionalized CF onto a cylindrical support, exhibited effective and consistent degradation of diverse micropollutants (77.9–94.5 %, TOC: 32.4–50.5 %) after a single-pass filtration. The excellent two-electron (2 e−) oxygen reduction reaction (ORR) performance of PAN-CF, along with the enhanced mass transfer in the flow-through configuration, contributed to the pollutant degradation by generating considerable reactive oxygen species (ROSs, including H2O2 and •OH) and facilitating adequate contact between pollutants and ROSs. The integration of electrochemistry significantly improved the antifouling performance of the filter, making it promising for real wastewater treatment. Detailed calculations and comparisons further confirmed the cost advantages of the proposed flow-through electrodes. This study provides a unique solution for the design and fabrication of engineeringly and economically feasible flow-through electrodes in electrochemical filtration systems.

Biodegradability enhancement and sequential treatment of real chemical industry wastewater by chemical coagulation and Electro-Fenton processes

A sequential treatment with chemical coagulation in the first step and Electro-Fenton (EF) in the second step was applied to chemical industry wastewater. By coagulation using Poly Aluminum Chloride (PAC) as a coagulant, 57.5% chemical oxygen demand (COD), 96.8% total suspended solids (TSS), and 90.5% color index (CI) removal were obtained. In the EF process applied after chemical coagulation, the design parameters were optimized by the central composite design. Two quadratic models of the four factors were established with the COD and CI as two responses. Optimized conditions of the EF were pH 2.5, Fe2+ dose 5 mM, applied current 1 A, and reaction time 60 min. Under these conditions, the COD removal from the validation experiments was 63.5%. In total, 84.5% COD removal was achieved with the two-step treatment. By extending the reaction time in EF to ensure the discharge limits, 89.5% COD removal was reached, and the COD concentration decreased to 193 mg/L after 240 min. At the same time, the 5-day biochemical oxygen demand (BOD5)/COD ratio increased from 0.1 to 0.57 after 240 min. Consequently, the discharge limit was provided and the biodegradability was improved.

Synchronously improved permeability, selectivity and fouling resistance of Fe-N-C functionalized ceramic catalytic membrane for effective water treatment: The critical role of Fe

Constructing catalytic membrane simultaneously displaying high permeability, selectivity and antifouling performance in water treatment remains challenging. Herein, the surface and pore channels of the ceramic membrane were co-functionalized with nitrogen doped carbon supported Fe catalyst (CN-F), and the Fe content was varied to investigate its effect on performance of CN-F coupled with peroxymonosulfate (PMS) activation (CN-F/PMS) for water treatment. Results confirmed the introduced Fe (in Fe-N coordination form) greatly enhanced the permeability, selectivity and fouling resistance of CN-F. Optimal CN-F3/PMS achieved 96.5% removal and 52.1% mineralization of sulfamethoxazole in short retention duration (2.7 min), whose performance was 5.4 and 6.7 times higher than that of nitrogen doped carbon functionalized ceramic catalytic membrane (CN/PMS) and CN-F3 filtration alone, respectively. CN-F3/PMS also efficiently inhibited fouling on both surface and pores with 2.8 and 2.4 times lower flux loss than that of CN/PMS and CN-F3 filtration alone, respectively. Moreover, CN-F3/PMS displayed superior performance in long-term treatment of real coking wastewater. The outstanding performance of CN-F was mainly attributed to the dual role of supported Fe, which served as hydrophilic site for enhanced water permeation and major active site for PMS adsorption and reduction into reactive species (mainly high-valent Fe(IV)=O species) towards pollutant elimination.

Characterization of simultaneous removal of nitrogen and phosphorus by novel Raoultella ornithinolytica strain YX-4 and application in real farm wastewater treatment

A novel strain having ability to simultaneously remove ammonium nitrogen, nitrate nitrogen, nitrite nitrogen and phosphorus was isolated from swine farm wastewater and was identified as Raoultella ornithinolytica YX-4 (NCBI accession number: OR646540). Nitrogen and phosphorus balance analysis combined with amplification of key enzyme genes of metabolic pathways revealed that the strain possess heterotrophic nitrification, aerobic denitrification, phosphorus accumulation and assimilation pathways. Significant removal of ammonium nitrogen, nitrate nitrogen and nitrite nitrogen were achieved (99%, 97% and 93% respectively) with optimal culture conditions. The transcript level of key enzyme genes was detected at different incubation period, and significant up-regulation of glnA, narI, narH, nirB, nirD, ppk1, and ppk2 was noted. This is the first report of the denitrification of phosphorus accumulating organisms R. ornithinolytica and reveals tangible results of key enzyme gene expression during real wastewater treatment.

Hydrodynamic behavior and start-up performance of a periodic anaerobic baffled reactor in an "every second" switching manner treating traditional Chinese medicine wastewater.

Most studies focus on the "clockwise sequential" switching manner for a four-compartment periodic anaerobic baffled reactor (PABR), while the exploration of the "every second" option on the feasibility for real industrial wastewater treatment is rarely reported. Hence, a PABR-treating traditional Chinese medicine wastewater was run continuously in "every second" switching manner with both switching period T and hydraulic residence time of 48 h. Satisfactory start-up performance was achieved during the operation of a climbing average organic load rate at approximately 1, 2, 4, and 6 kg chemical oxygen demand (COD) m-3 d-1 for 12, 24, 24, and 6 days, respectively. The average COD removal was 87.20% after the second lifting of OLR and 89.98% after the third one. Denaturing gradient gel electrophoresis and its cluster analysis showed that the microbial communities in each compartment adapted their structure in response to the periodically changing micro-ecology conditions. Moreover, the residence time distribution test with tap water in the clean PABR was carried out in experiments and computational fluid dynamics (CFD) simulation, both of which were in good agreement. The CFD model output visualized the flow velocity field and hydrodynamic-mass transport inside the PABR. Optimization of operation pattern in PABR including switching manner and frequency depended on both the type of waste being treated and the flexibility of biomass to periodically changing micro-ecology conditions.

Single-atom catalysts-based Fenton-like processes for water contaminant management: a review

Fenton reaction is particularly effective for mineralizing stubborn organic pollutants due to the high oxidation potential of •OH with the green end product of H2O. However, exogenous addition of hydrogen peroxide (H2O2) is usually accompanied by the high operation risks and economic costs along with the storage and transportation of H2O2. Besides, inefficient activation of H2O2 due to the rapid accumulation of Fe3+ and slow regeneration of Fe2+ constrains the efficiency. Hence, heterogeneous catalysts that overcome those limitations by in-situ regenerating and activating H2O2 with high efficiency in the Fenton-like processes are promising alternatives to the conventional Fenton reactions. In this review, we give an overall summarization on the single-atom catalysts (SACs) attempted in the Fenton-like processes recently, and discuss their potential roles in the wastewater contaminant alleviation. Firstly, a brief introduction is made on the basic principles of H2O2 generation and activation in the Fenton-like processes, and the coordination environment of SACs is emphasized. Then, a detailed discussion on how the type of central metal sites and their coordination environment influence the catalytic performance from three perspectives: H2O2 activation, selective H2O2 generation via 2e− oxygen reduction reaction, and bifunctional SACs for electro-Fenton. After that, the recent advances on SACs catalyzed Fenton-like processes in the contaminant removal are introduced, and the kinetic perspective, influence of water quality, the stability and long-term performance, as well as the mass transfer and reactor scale up are discussed, respectively. Finally, the major challenges for the applications in real wastewater treatment are outlooked.

Peracetic acid-based electrochemical treatment of sulfamethoxazole and real antibiotic wastewater: Different role of anode and cathode

Although has high oxidation capacity and low toxic by-product formation potential, the feasibility, mechanism, and antibiotic treatment performance of peracetic acid (PAA)-based electrochemical system remains unknown. This work systematically studied the electro-activation process of PAA, and distinguished the different mechanisms of anode and cathode. In the PAA-based electrochemical system, the anode mainly produces BDD(•OH), and the cathode is mainly the R-O• (especially CH3CO3•). These differences lead to different degradation pathway and toxicity evolution of sulfamethoxazole (SMX). The anode transformation products (TPs) show negative toxicity and are difficult to be further removed, while TPs from PAA-dominated cathode posed electron-donating effect and a tapering ecological risk. The BDD(•OH) can well mineralize the TPs produced from cathode. Moreover, the active chlorine produced by the anode can effectively avoid the accumulation of NH4+- N released by antibiotic degradation. In an undivided cell, PAA-based treatment for real antibiotic wastewater achieved 73.9%, 59.4%, 76.9%, and 31.7% of COD, TOC, NH4+- N, and TN removal, respectively. More importantly, when PAA existed in this system, the active chlorine and AOCl accumulation are inhibited (inhibition ratio 83.5% and 82.7%, respectively). This study provides theoretical and technical support for the practical application of PAA-based electrochemical system.

Electrochemical advanced oxidation of 2,4-D herbicide and real pesticide wastewater with an integrated anodic oxidation/heterogeneous electro-Fenton process

Pesticide wastewater is accused of polluting receiving waters with toxic and non-biodegradable organic pollutants. The present study has developed an integrated electrochemical oxidation process based on PbO2 anodic oxidation and Fe/SBA-15 heterogeneous electro-Fenton (PbO2/EF-(Fe/SBA-15)) for synergistic treatment of pesticide wastewater. PbO2 electrocatalyst was prepared by anodic deposition method and Fe/SBA-15 catalyst was synthesized by incipient wetness impregnation method. To optimize and model the removal of 2,4-D, a quadratic mathematical model by orthogonal central composite design (CCD) was proposed and validated. In optimal conditions including solution pH = 5, H2O2 concentration = 2000 mg/L, applied current = 10 mA/cm2, Fe/SBA-15 dose = 1.25 g/L and 2,4-D concentration = 30 mg/L, the experimental removal efficiency of 2,4-D after 35 min of reaction in the PbO2/EF-(Fe/SBA-15) process was 99.85 %. Moreover, the kinetics of 2,4-D removal in the integrated PbO2/EF-(Fe/SBA-15) process was about 3.84 times faster than the separate PbO2 anodic oxidation, confirming a remarkable degradation synergy. The mineralization of 2,4-D was confirmed by LC-MS and TOC analyses, and considering the identified intermediates, the possible degradation pathways of 2,4-D to CO2 and H2O were suggested. Real pesticide wastewater treatment was studied under optimal conditions. COD removal efficiency in PbO2/EF-(Fe/SBA-15) process and PbO2 anodic oxidation was 71.2 % and 32.5 %, respectively. Also, the energy consumption (EC) of these two processes was 17 kWh/kg COD and 38 kWh/kg COD, respectively. The results of this study suggest the integrated PbO2/EF-(Fe/SBA-15) process is a practical and cost-effective process for non-biodegradable pesticide wastewater treatment.

Treatability of high-strength real sheep slaughterhouse wastewater using struvite precipitation coupled Fenton's oxidation: The MAPFOX process

Struvite (MAP, magnesium ammonium phosphate hexahydrate, MgNH4PO4.6H2O) precipitation-aided Fenton's OXidation (MAPFOX process) was explored in the treatment of high-strength real sheep slaughterhouse wastewater (RSSW) for the first time under a comprehensive soft-computing-based modeling study. The experimental results showed that under the highest-efficiency conditions (chemical combination of MgCl2.6H2O + NaH2PO4.2H2O, a molar ratio of Mg2+:NH4+-N:PO43–P = 1.2:1:1, a reaction pH of 9.0 ± 0.10, [NH4+-N]0 = 240 ± 20 mg/L, and a reaction time of 15 min), MAP precipitation could effectively remove more than 80 %, 60 %, 55 %, and 70 % of color, total chemical oxygen demand (TCOD), soluble COD (SCOD), and ammonium nitrogen (NH4+-N) from the raw RSSW. The results of the Fenton's oxidation used as the post-treatment unit of the proposed MAPFOX system indicated that the integrated advanced oxidation process (AOP) was able to reduce the residual pollutant levels in the MAP-pretreated RSSW to the relevant discharge standards. Under the subsequent condition of [Fe2+]0 = 90 mmol/L, [H2O2]0 = 180 mmol/L, reaction pH = 3.25, and total reaction time = 60 min, more than 97 % of color, TCOD, SCOD, and NH4+-N could be removed from the RSSW via the Fenton's oxidation after the MAP-based physicochemical treatment. According to SEM micrographs, surface morphology of dehydrated struvite exhibited irregular-shaped and overlapping sharp-edged particles of various sizes with an average size of about 50.9 μm. The Fourier Transform Infrared (FTIR) spectroscopy confirmed the active functional groups and type of bonds for the high-strength RSSW-oriented struvite (heated) within the spectral range of 4000–450 cm−1. Thermogravimetric Analysis (TGA), Derivative Thermogravimetry (DTG), Differential Thermal Analysis (DTA), and Differential Scanning Calorimetry (DSC) of the dehydrated struvite revealed that the weight loss occurred in three temperature zones, the maximum weight loss rate of 0.252 mg/min was recorded at around 224 °C and at time of 20.83 min, and the sample had strong endothermic and medium exothermic peaks at about 241 °C and 679 °C, respectively. The predictive successes of the implemented soft-computing approaches were benchmarked in terms of various statistical goodness-of-fit parameters. The performance assessment indices corroborated the superiority of the support vector machines-Pearson VII universal kernel function (SVM-PUKF)-based model (correlation coefficient (CC) = 0.9999–1.0000), mean absolute error (MAE) = 0.0222–0.0389 %, mean absolute percentage error (MAPE) = 0.0270–0.0506 %, root mean squared error (RMSE) = 0.0258–0.0415 %, coefficient of variation of RMSE (CV(RMSE) = 0.0003–0.0008, Nash–Sutcliffe efficiency (NSE) = 0.9998–1.000, Legates and McCabe's index (LMI) = 0.9894–0.9952) over other data-intelligent models in predicting the pollutant removal efficiencies. The computational results also indicated that the narrowest uncertainty bands (±1.96Se = 0.0537–0.1483 %) and the lowest amounts of expanded uncertainty (U95 = 3.1224–5.3124 %) values for all efficiency sets were achieved for the applied SVM-PUKF-based strategy. This study demonstrated the first-ever and successful application of the proposed MAPFOX process in treatability of the RSSW and capability of the implemented soft-computing strategy in modeling a highly nonlinear treatment system.

Assessment of Denitrification and Nitrification Processes during Landfill Leachate Treatment

Landfill leachate is generated from waste degradation in landfill sites, and its treatment includes biological or combined treatment with physico-chemical methods. A frequently applied technology in the biological stage of landfill leachate treatment plants is based on denitrification and nitrification. Nevertheless, with the availability of a huge number of scientific reports, the management of denitrification and nitrification (D/N) processes in the frame of real wastewater treatment plants (WWTPs) is rather difficult and always remains a critical technological problem. This study aims to perform a comparative assessment between denitrification and nitrification processes during landfill leachate treatment in three different situations in the WWTP of the Municipal Enterprise for Waste Treatment in Sofia City, Bulgaria. The comparative assessment is based on the biotransformation effectiveness of ammonium ions in the course of nitrification and of nitrates in the course of denitrification. Mixed samples (wastewater and activated sludge) were taken from the sequencing batch reactors operating in the mode of denitrification and nitrification. All physico-chemical (pH, dissolved oxygen, organics concentration, BOD5:COD, nitrogen and phosphorous) and biological (sludge volume index, sludge biotic index, quantity of aerobic heterotrophs, denitrifiers and nitrifiers, total dehydrogenase activity) indicators were investigated in the samples from the biobasins in the mode of denitrification and nitrification. The conditions for the implementation of the two processes were compared, along with the state of the activated sludge in the different reactors. The obtained results showed that denitrification was the critical process in the technology on the base of D/N. A major factor that managed the denitrification was the lower concentration of biodegradable organic matter which led to a deformation of the activated sludge structure, a decrease in the count of heterotrophic microorganisms, a decrease in the total activity of the activated sludge and an inhibition of the nitrate reductase activity. The nitrification processes were accomplished with high intensity. The results confirmed that D/N could be optimized and controlled using specific wastewater treatment technology parameters and purposely applied indicators.

UV/periodate and UV/chlorine for dye degradation and real wastewater treatment: a comparative study

Abstract The discharge of synthetic dyes into the environment poses a significant threat to both human health and the ecosystem, necessitating the treatment of contaminated water. To generate free radicals for the elimination of Direct Blue 71 (DB71) dye from aqueous solutions, periodate (PI) and chlorine (Cl2) have been employed. In this study, separate activation of PI and Cl2 was achieved using ultraviolet (UV) light. The impact of various operational parameters was investigated, resulting in the complete degradation of the dye within 12 min. The presence of ferrous and copper ions had a minor enhancing effect on the degradation rate in both systems. Scavenging experiments confirmed that HO• and IO3• were the primary agents responsible for DB71 degradation in the UV/PI system, while reactive chlorine radicals played a dominant role in the UV/Cl2 process. In terms of mineralization, application for real wastewater and energy efficiency, the UV/PI system exhibited slightly superior performance compared to the UV/Cl2 system.

Sustainable Technological Advancements for Dairy Waste Water Treatment-A Review

The dairy industry has global importance due to its essential contribution towards human nutrition as well as high economic opportunities. There is a consistent and steep growth in India's dairy sector in the last few decades and now India is one of the major milk-producing countries in the world. Highstrength dairy wastewaters, if discharged without proper treatment, severely pollute the receiving water bodies. In this scenario 'Waste as a resource' concept has been gaining the interest of researchers. The present review delineates different technological advancements for treating dairy wastewater and compares which is the better option in terms of sustainability. In the aerobic process, advanced bioaugmented systems which use bacterial and fungal consortia were found to be effective and sustainable with biological oxygen demand removal of 78.7% and 74.7%. Physio-chemical methods using natural coagulants like Moringa oleifera (MO) and pomegranate peel powder were also found to be effective with 81.8 % nitrogen removal from dairy wastewater treatment. Phytoremediation using water fern (Azolla pinnata R. Br.) was found to be efficient with dissolved solids reduction efficiency of 71.56 %. The fluidized bed anaerobic reactor unit was found to generate a biohydrogen content of 35.72±9.43% when the OLR was 53.25± 7.81 kg. COD m–3d–1. Microbial fuel cells treatment of real dairy wastewater (RDW) using Shewanella algae (MTCC-10608) has generated maximum current density and power density of 141 mA/m2 and 50 mW/m2 respectively. These two technologies are better sustainable options for dairy wastewater treatment since waste to energy aspect is satisfied.

A review of electro-Fenton and ultrasound processes: towards a novel integrated technology for wastewater treatment.

Nowadays, the presence of persistent dissolved pollutants in water has received increasing attention due to their toxic effects on living organisms. Considering the limitations of conventional wastewater treatment processes for the degradation of these compounds, advanced oxidation processes such as electro-Fenton and sono-chemical process, as well as their combination, appear as potentially effective options for the treatment of wastewater contaminated with bio-recalcitrant pollutants. In view of the importance of the development of processes using real effluents, this review aims to provide a comprehensive perspective of sono-electro-Fenton-related processes applied for real wastewater treatment. In the first section, the fundamentals and effectiveness of both homogeneous and heterogeneous electro-Fenton approaches for the treatment of real wastewater are presented. While the second part of this work describes the fundamentals of ultrasound-based processes, the last section focuses on the coupling of the two methods for real wastewater treatment and on the effect of the main operational parameters of the process. On the basis of the information presented, it is suggested that sono-electro-Fenton processes substantially increase the efficiency of the treatment as well as the biodegradability of the treated wastewater. The combined effect results from mass transfer improvement, electrode cleaning and activation, water electrolysis, and the electro-Fenton-induced production of hydroxyl radicals. The information presented in this work is expected to be useful for closing the gap between laboratory-scale assays and the development of novel wastewater technologies.

Treatment of Textile Wastewater by a Novel Clay/TiO2/ZnO-Based Catalyst, Applying a Synergic Catalytic Ozonation–Electroflocculation Process

This study aims to investigate the treatment of real textile wastewater using a novel bentonite clay/TiO2/ZnO-based ozonation catalyst. In this study, synergic electroflocculation/catalytic ozonation, catalytic ozonation, and ozonation processes are applied in a modified hybrid reactor. To the authors’ knowledge, this is the first application of bentonite clay/TiO2/ZnO as an ozonation catalyst for treating real textile wastewater. The four operational variables—ozone dose (0.2–0.8 mg/min), reaction time (0–120 min), DC voltage supply (5–15 V), and catalyst dose (0.5–2 g/L)—were studied for decolorization and for the removal of chemical oxygen demand (COD). The results showed that the combined process (electroflocculation + clay/TiO2/ZnO/O3) had the highest removal efficiencies for COD and color (97.86% and 97.90%, respectively) at optimum parameters of 10 DC volts. an ozone dose of 0.8 mg/min, and a catalyst dose of 2 g/L in textile wastewater. The results further revealed that the initial pH of wastewater plays an essential role in the process’s overall performance. The studied synergic process was efficient for real wastewater treatment under alkaline pH (6–9). Based on empirical work, we established that the synergic process is suitable for effectively treating textile wastewater.

Two-dimensional RGO-bridge S-scheme phosphorus-doped g-C3N4/Bi5O7I van der Waals heterojunctions for efficient visible-light photocatalytic treatment of real pharmaceutical wastewater

Two-dimensional RGO-bridge S-scheme phosphorus-doped g-C3N4/Bi5O7I van der Waals heterojunctions for efficient visible-light photocatalytic treatment of real pharmaceutical wastewater

Urban wastewater oxidation by bioelectrochemical systems: To what extent does the inoculum matter?

Bioelectrochemical systems offer an environmental-friendly alternative to activated sludge for future wastewater treatment but have not yet reached technological maturity. This study aims to assess the long-term influence of the inoculation strategy on real urban wastewater treatment by bioelectrochemical systems, focusing on both process performances and biofilm assembly dynamics. Four inoculation strategies were investigated in triplicates during six consecutive batches to treat primary clarifier effluent at lab scale. At the studied anodic potential (0.05 vs SHE), no long-term impact of the inoculation strategy on the performances was observed. Indeed, after three batches, electrochemical (88.0 ± 3.9 % coulombic efficiencies) and treatment performances (30.8 ± 3.9 % COD removals) converged for all inoculation strategies. Consistently, the microbial compositions of the different biofilms converged, with selection being the main assembly process. For larger scale bioelectrochemical reactors, the use of wastewater as both substrate and inoculum would be the most convenient choice, since the other inoculation strategies only displayed short-term effects.

Heterogeneous Fenton treatment of shale gas fracturing flow-back wastewater by spherical Fe/Al2O3 catalyst.

In this work, efficient Fenton strategy have been proposed for degradation of shale gas fracturing flow-back wastewater using the spherical Fe/Al2O3 supported catalyst. Prior to actual fracturing fluid treatment, the typical model wastewaters such as p-nitrophenol and polyacrylamide were employed to evaluate the catalytic properties of prepared catalyst, and then Fenton treatment of the shale gas fracturing flow-back wastewater was performed on the self-assembled catalytic degradation reactor for continuous flow purification. Results showed that under the conditions of 0.25 mol L-1 impregnating concentration, pH 4, 50 g L-1 catalyst and 0.75 mL L-1 30% H2O2, the removal efficiency of p-nitrophenol and polyacrylamide reached 74% and 61%, respectively, while the COD removal of fracturing flow-back fluid was approximately 48% with the residual 88 mg L-1 COD, meeting the emission standards of the integrated wastewater discharge standard (GB 8978-1996, COD < 100 mg L-1). This work offers new alternatives for Fenton treatment of real wastewater by efficient and low-cost supported catalysts.

Natural sunlight-driven enhanced abatement of real resin industry wastewater using sludge-derived photocatalyst: Potential to generate carbon credits

The resin manufacturing industry is one of the industrial sectors that consumes huge quantities of water and generates enormous quantities of toxic wastewater with a high level of chemical oxygen demand (COD). In the present study, the performance of an optimized copped-doped raw galvanic waste-derived (CRGW) photocatalyst was evaluated in a novel stirred tank photoreactor in batch and continuous configurations as a possible solution for the treatment of real resin industry wastewater (RIW) under natural sunlight. Under optimal operating conditions, a COD removal rate of 70.3% and 43.5% was observed in batch and continuous configurations within 4 h, respectively. The photoreactor in continuous mode was aided by a magnetic bed that anchored the photocatalyst to the reaction segment without subsequent retrieval from the treated effluent. The mixture of pollutants in the RIW underwent photodegradation due to a pronounced bathochromic shift in UV absorption. Moreover, the XRD and XPS results confirmed the crystallinity and successful charge migration in the synthesized CRGW. The applicability of the photocatalyst for degradation of RIW was demonstrated through an economic analysis, and its specific cost was determined to be 9.5 USD/m3 of treated wastewater. Furthermore, this study aims to be a step toward generating carbon credits by avoiding the release of 18 tons of CO2/yr into the atmosphere by utilizing natural sunlight for photodegradation. The reduction, avoidance, or removal of greenhouse gases is pivotal in today’s world, and carbon credits can accelerate this transformational journey towards a sustainable future.