Treatment Of Synthetic Wastewater Research Articles

Ultrasound assisted electrochemical oxidation of synthetic dye wastewater

ABSTRACT This study reports the treatment of synthetic dye wastewater in a sono-electrochemical reactor. The influence of three different supporting electrolytes (Na2SO4, NaCl, and Na2NO3) on % decolorisation was studied and higher decolorisation was observed with NaCl. The increase in applied current density (0.25, 0.5, 0.75, 1, 1.25 A/dm2) enhanced the color removal and the optimum current density arrived was 1.25 A/dm2. The % decolorisation was studied at three different pH (3, 7 & 11), and about 95.7% decolorisation was observed at pH 3. The inter electrode distance of 1 cm gave highest decolorisation. The addition of Na2SO4 and Na2NO3 in the sonolyzer bath did not influence the % decolorisation significantly. The sono-electrochemical process gave 99.16% decolorisation and 91.15% COD reduction while the electrochemical process gave 94.79% decolorisation and 76.82% COD reduction. The optimum electrolyte concentration, current density, pH and electrode distance of 0.5 g/L, 1.25 A/dm2, 3, and 1 cm, respectively gave highest decolorisation. The reaction kinetics of the sono-electrochemical oxidation treatment was also investigated. The higher mineralisation rate at a lower residence time indicates that the combined treatment is promising for degrading recalcitrant compounds present in wastewater.

Acceleration of the startup process of an anaerobic baffled reactor utilizing electrolyte regeneration

The objective of this study was to examine the performance of an electrolytic anaerobic baffled reactor (EABR) that contained five rectangular compartments in the treatment of low-strength synthetic wastewater. The effect of integration of electrolysis into an anaerobic baffled reactor (ABR) on the startup process, removal of chemical oxygen demand (COD), production of volatile fatty acids (VFAs), and profile of the pH of the EABR were investigated. With a low-strength influent (COD = 600 mg/L), the results indicated that COD removal was 92 % and that the VFAs were negligible by the third compartment. Also, VFA analysis showed that propionic acid was found in the first two compartments. This finding is aligned with compartment-wise profiles of COD removal, which was the highest in the initial compartments and which decreased longitudinally down the reactor. Monitoring the pH profile elucidated that the largest drop in pH was observed in the first two compartments, which is attributed to acidogenesis and acetogenesis activities. The proposed integration could decrease the startup process time to 12 d or less for low-strength feed of synthetic wastewater. This study demonstrated the significance of maintaining a stable pH for the optimal functioning of a diverse bacterial community by integrating bioelectrochemical processing in anaerobic digestion, as well as the application of the potential strategies to optimize the startup process of ABR. The optimization of the startup process of ABR through the integration of bioelectrochemical processing can contribute to Sustainable Development Goal 9 (Industry, Innovation, and Infrastructure) by promoting sustainable technological advancements and fostering sustainable industrialization.

Performance of electro-Fenton process for the treatment of synthetic sulphidic spent caustic waste stream generated from petroleum refineries

Sulphidic spent caustic (SSC) is an alkaline waste stream which is generated during caustic scrubbing of liquefied petroleum gas and ethylene products. Due to presence of high concentrations of sulphides and phenols, the waste stream requires proper treatment before mixing with the low strength wastewater streams produced from other refinery operations. Electrochemical process is an emerging treatment method that can work efficiently at ambient conditions. The present study reports performance of electro-Fenton (EF) process for the treatment of synthetic SSC wastewater (sulphides = 10 g L−1, phenol = 2 g L−1 and pH = 12.9). The EF runs were carried out for 2 h duration in a reactor equipped with iron electrodes. The effects of H2O2 dose (0.26–1.3 M), current density (1–20 mA cm−2), pH (4.5–12.9) and stirring speed (100–1000 rpm) were investigated on removal of pollutants. The H2O2 was rapidly consumed in initial 30 min during which the significant fraction of the pollutants was degraded or removed. The optimum conditions for EF process were found to be as follows: pH = 4.5, H2O2 dose = 1.05 M, current density = 5 mA cm−2 and stirring speed = 500 rpm. At these conditions, the maximum sulphide and phenol removals from the wastewater were 98% and 91%, respectively. The results will be helpful to the wastewater treatment plant operators worldwide dealing with high concentrations of such pollutants.

Exploring the scalability of solar-activated persulfate with iron-EDDS in raceway pond reactors for advanced wastewater treatment

In this study, the removal of microcontaminants (MCs) by the activation of persulfate (PS) with Fe(III)-EDDS under natural solar radiation in a low-cost raceway pond reactor (RPR) was investigated. The primary focus was to evaluate the effect of the Fe(III)-EDDS molar ratio, initial iron concentration, PS concentration, and initial pH on process performance while using sulfamethoxazole (SMX) and carbamazepine (CBZ) as model MCs. The investigation encompassed three different water matrices: natural water, synthetic municipal wastewater treatment plant (MWWTP) secondary effluent, and actual MWWTP secondary effluent. During experiments in natural water, it was found that 0.1 mM Fe(III) at a 1:2 molar ratio and 0.2 mM Fe(III) at a 1:1 molar ratio resulted in the most adequate operational conditions. Further experiments revealed a general decrease in process efficiency due to water matrix effects; however, this could be compensated by increasing the initial PS concentration and decreasing the initial operation pH. For example, the use of 0.2 mM Fe(III) at a 1:1 Fe(III):EDDS molar ratio, with 2 mM PS at pH 6, allowed for an 80% removal of the MCs sum in approximately 20 min, along with a significant decrease in chronic toxicity (Selenatrum Capricornutum) when working with actual waters. Nonetheless, the final experiment, focused on simultaneous MCs removal and wild bacteria inactivation in actual MWWTP secondary effluent, showed only a 1.6–1.8 log reduction of Escherichia coli, total coliforms, and Enterococcus faecalis. As such, further studies about the solar/Fe(III)-EDDS/PS process are needed to explore new strategies that improve its disinfection efficiency.

Magnetic biochar derived from peanut shells facilitates antibiotic degradation and fouling control in anaerobic membrane bioreactor for antibiotic pharmaceutical wastewater treatment

Anaerobic membrane bioreactor is an attractive option for antibiotic pharmaceutical wastewater treatment, but the unsatisfied treatment performance and membrane fouling issue hindered its wide application. Herein, magnetic biochar (MBC) derived from peanut shells was added to AnMBR for synthetic pharmaceutical wastewater treatment containing sulfamethoxazole (SMX). The results indicated that the treatment performance was improved with 80 % of COD and over 90 % of SMX removal. This can be explained by the adsorption capacity of MBC and improved microbial activity due to the direct interspecies electron transfer enhancement with MBC addition. Membrane fouling was also alleviated due to the adsorption and magnetic bio-effect of MBC, leading to the reduced soluble microbial product (SMP) (22.2 to 6.3 mg/gVSS) and extracellular polymer substance (EPS) concentration (18.9 to 14.2 mg/gVSS), and enlarged particle size (60.6 to 113.4 μm). Microbial diversity analyses indicated that hydrolysis and acidogenesis bacteria (Bacteroidetes and Choloflexi phyla), methanogenic archaea (Methanobacterium and Methanosaeta), and bacteria related to electron transfers (unclassified_f_Geobacteraceae) were enriched due to the presence of MBC. Additionally, the SMX plausible biotransformation pathway and removal mechanism further validated that MBC addition can improve the SMX biodegradation and biotranformation. Importantly, the MBC addition facilitates antibiotic degradation and fouling alleviation of AnMBR, which makes AnMBR a more attractive choice treating for antibiotic pharmaceutical wastewater.

Membrane bioreactor and advanced oxidation processes for combined treatment of synthetic wastewater containing naproxen, bisphenol A, and sulfamethoxazole

Environmental and health issues caused by the abundance of emerging pollutants in the aquatic environment motivate the research into wastewater treatment methods. In the present study, a membrane bioreactor (MBR) and advanced oxidation processes (AOPs) were combined for the efficient treatment of a synthetic wastewater containing naproxen (NPX), bisphenol A (BPA), and sulfamethoxazole (SMX). The MBR setup consisted of a sequencing batch reactor (SBR) linked to an external filtration system. Track-etch membranes (TEM) with pore size of 10 nm, 50 nm, and 100 nm and a phase inversion membrane (PIM) were used. The total organic carbon (TOC) removal for the SBR was in the range of 78–86 %, while the degradation of NPX, BPA, and SMX observed was 11 %, 45 %, and 6 %, respectively. All of the four membranes tested showed insignificant TOC removal efficiencies ranging from 1 % to 6 %. In the case of emerging pollutants, the highest removal values were observed for the 10 nm TEM: 11 %, 93 %, and 14 % for NPX, BPA, and SMX, respectively. The removal of BPA using membranes was possibly linked to sorption and size exclusion. Finally, the effluents from SBR and MBR were treated using UV-driven AOPs. Persulfate (PS) was used as an oxidant, and UV light, zero-valent iron (ZVI), goethite, and iron (II) sulfate heptahydrate were used as activators. Complete mineralization of TOC and removal of emerging pollutants were achieved after 30 min for MBR effluents using UV/PS 10 mM /ZVI 25 mg/L, which shows the high potential of using MBR and AOPs in combination.

Robust ceramic-based graphene membrane for challenging water treatment with enhanced fouling and scaling resistance.

Membrane fouling and scaling are two challenges for efficient treatment of hypersaline wastewater, greatly hindering separation performance and operation stability of desalination membranes. In this work, we report a smooth ceramic-based graphene desalination membrane, exhibiting enhanced anti-fouling and anti-scaling ability and operational performance for efficient treatment of both synthetic and real industrial wastewaters, outperforming polypropylene (PP) membrane. For treatment of hypersaline waters containing organic or inorganic substance, we demonstrate that the graphene membrane exhibits more stable water flux and almost complete salt rejection (>99.9%) during constant operation. Enhanced anti-fouling and desalination performance of graphene membrane could be attributed to the lower attractive interaction force with foulant (-4.65 mJ m-2), lower surface roughness (Ra=2.2±0.1nm) and higher affinity with water than PP membrane. Furthermore, an anti-scaling mechanism enabled by graphene membrane is evidenced, with a highlight on the roles of smooth graphene surface with lower roughness, less nucleation sites and lower binding force with scaling crystals. Importantly, even for industrial petrochemical wastewater, such a graphene membrane also exhibits relatively more stable water flux and promising oil and ions rejection during long-term operation, outperforming PP membrane. This study further confirms a promising practical application potential of robust ceramic-based graphene membrane for efficient treatment of more challenging hypersaline wastewater with complicated compositions, which is not feasible by conventional desalination membranes.

Joint Multi-Optimization of an Extremophilic Microbial Bioanode for Mitigation of Mixed Hazardous Azo Dyes in Textile Synthetic Wastewater

Bioelectrochemical systems (BESs), rather than physicochemical processes, are used for wastewater remediation, electricity production, and zero carbon dioxide emission. Textile effluents contain organic and inorganic compounds that can fuel BESs. The main goal of this study was to understand the interplay between the anode material, its surface area, the potential applied to the working electrode (WE), and the concentration of the co-substrate, and how these factors lead to the formation of highly efficient thermohalophilic bioanodes (THB) retrieved from Chott El Djerid (SCD) hypersaline sediment for the treatment of synthetic textile wastewater. To this end, twenty-seven bioanode formation experiments were designed using a Box-Behnken matrix and response surface methodology to understand concomitant interactions. All experiments were conducted in electrochemical reactors of final volume 750 mL inoculated with 80% of enrichment medium containing three azo dyes at a concentration of 300 ppm and 20% of biocatalyst microbial SCD source, at 45 °C. The optimal levels were predicted using NemrodW software as carbon felt (CF) anode material, 6 cm2 anode surface, 7 g/L glucose concentration, and −0.1 V applied potential. These theoretical results were experimentally validated, using maximum current output of 5.23 ± 0.30 A/m2, decolorization rate of 100%, and a chemical oxygen demand (COD) removal rate of 96 ± 1%. Illumina Miseq results revealed that bacterial community harbored the bioanode was dominated at phylum level by Firmicutes (67.1%). At the species level, the biofilm was mainly colonized by Orenia metallireducens species (59.5%). Obtained findings show a promising application of THB in the degradation of recalcitrant molecules as well as for the energy recovery.

Production and utilization of the Chlorella vulgaris microalgae biochar as the fuel pellets combined with mixed biomass

The current study focuses on the capability of microalgae biochar as fuel pellets. Additionally, the study aims to investigate the treatment of synthetic saline wastewater through microalgae cultivation, which is an essential tool for meeting the sustainable environment requirements of nations. Microalgae have the tendency to absorb harmful pollutants from wastewater and use them as nutrients for their growth. In this study, Chlorella vulgaris was cultivated in sewage wastewater, and the cultivated samples were collected to produce biochar through a microwave-assisted pyrolysis process. Growing microalgae in wastewater reduces the concentration of ammonia and total phosphorus, and both toxic pollutants are completely absorbed after 60 days of cultivation. The cultivated microalgae underwent pyrolysis to produce biooil, synergetic gas, and biochar. The microwave-assisted pyrolysis process was used to produce the biochar, which was then mixed with agro-waste to form fuel pellets at an equal mass ratio. Three different samples at various concentrations of biochar were examined. Based on the findings, it is evident that the calorific value of the fuel pellets is enhanced upon the addition of biochar. Moreover, there is an increase in the burning time of the pellets made from microalgae-based biochar. Furthermore, microalgae cultivation in wastewater reduced ammonia and total phosphorus content, and the biochar produced from the harvested microalgae improved the ultimate stress, heating value, and bulk density of the pellets. The addition of biochar to the pellets reduced moisture content and increased combustion time, making it a highly justifiable option.

Investigation of Biosorption Properties of Water Hyacinth Root in Textile Effluent and Synthetic Wastewater Treatment

Investigation of Biosorption Properties of Water Hyacinth Root in Textile Effluent and Synthetic Wastewater Treatment

Enhanced Removal of Phosphorus from Aqueous Solutions by Cation-Modified Hydrochar

In this study, cassava stem-derived hydrochar was modified with sodium hydroxide (NaOH) treatment, followed by loading of minerals, was used to prepare cation-modified hydrochars with enhanced phosphate removal ability. Cassava stems were converted to hydrochar by hydrothermal carbonization at 240 °C for 60 min, then it was soaked in 2 M NaOH for 3 h. The NaOH-treated hydrochars were then loaded with iron (Fe), magnesium (Mg) and calcium (Ca). The cassava stems and the derived hydrochars were analyzed for carbon, hydrogen, nitrogen and oxygen content, surface morphology and elemental compositions. Methylene Blue Numbers (MBN) measured surface area and porosity, and pH at the point of zero charge (pHpzc) was determined. Modification with Fe, Mg and Ca improved phosphate removal efficiency of the resulting hydrochars. Treatment of synthetic wastewater containing 50 mg P/L at pH 7 with the dosage of 2 g/L of the cation-modified hydrochars for 360 min showed that phosphate removal efficiency of these modified hydrochars were - Fe-modified 81 %, Mg-modified 66 % and Ca-modified 56 %. When the adsorbent dosage increased to 20 g/L, more than 98 % of phosphate was removed by the hydrochars modified with Fe, Ca and Mg. In the same conditions, phosphate removal efficiency was for the NaOH-treated hydrochars - 89 %, hydrochar derived from cassava steam - 69 % and the starting material - 59 %. The phosphate removal ability of these cation-modified hydrochars increased even when initial phosphorus concentration was increased to 100 mg P/L. This work demonstrated that an abundant agricultural residue, cassava stems, can be converted into effective phosphate adsorbents. HIGHLIGHTS Cassava stem were converted to hydrochar by aqueous carbonization at elevated temperature and pressure - hydrothermal carbonization (HTC) Sequential steps of alkali treatment and chemical modification, following HTC, were used to improve the phosphate removal ability of the cassava stem-derived hydrochar Loading of minerals (Fe, Mg and Ca) was a vital way to increase the adsorption of phosphates on hydrochar Phosphorus removal efficiency of Fe-loaded hydrochar was better than Mg- and Ca-loaded hydrochars Cation-modified hydrochars showed good phosphate removal ability over a wider concentration range GRAPHICAL ABSTRACT

Enhanced treatment of synthetic wastewater by bioaugmentation with a constructed consortium

Bioaugmentation by adding well-functioning mixed microorganism consortia represents a potentially useful approach to improve contaminant removal in wastewater treatment plants (WWTPs). However, unfavorable environmental conditions (i.e., low temperatures) can severely inhibit microbial activity, drawing our attention to constructing cold-tolerant microorganism preparations and investigating their availability in practical applications. Here we screened four in situ functional isolates from the activated sludge of secondary sedimentation tanks in WWTPs to construct a psychrophilic microbial consortium, which was used to perform bioaugmentation for enhanced removal of nitrogen and phosphorus under low temperatures. The consortium was established by cocultivation of four isolates, characterized by 16 S rRNA as the COD-degrading bacterium Aeromonas sp. Z3, aerobic denitrifying bacterium Acinetobacter sp. HF9, nitrifying bacterium Klebsiella sp. X8, and polyphosphate-accumulating bacterium Pseudomonas sp. PC5 respectively. The microorganism preparation was composed of Z3, HF9, X8, and PC5 under the ratio of 1: 1: 3: 1, which can exert optimal pollutant removal under the conditions of 12 °C, 6.0–9.0 pH, 120–200 r‧min−1, and a dosage of 5% (V/V). A 30-day continuous operation of the bioaugmented and control sequencing batch reactors (SBRs) was investigated, and the bioaugmented SBR showed a shorter start-up stage and a more stable operating situation. Compared to the control SBR, the COD, NH4+-N, TN, and TP removal efficiency of the bioaugmented SBR increased by an average of 7.95%, 9.05%, 9.54%, and 7.45% respectively. The analysis of the microbial community revealed that the introduced isolates were dominant in the activated sludge and that functional taxa such as Proteobacteria, Bacteroidota, and Actinobacteria were further enriched after a period of bioaugmentation. The study provides some basis and guidance for the practical application of how to strengthen the stable operation of WWTPs under low temperatures.

Effects of High Pharmaceutical Concentrations in Domestic Wastewater on Membrane Bioreactor Treatment Systems: Performance and Microbial Community.

Despite pharmaceuticals being widely detected in water-bodies worldwide, what remain unclear are the effects of high pharmaceutical concentrations on the treatment efficiency of biological wastewater treatment processes, such as membrane bioreactor (MBR) systems. This study investigated the efficiency of MBR technology in the treatment of synthetic wastewater containing a mixture of five typical pharmaceuticals (ofloxacin, sulfamethoxazole, sulfamethylthiadiazole, carbamazepine and naproxen) with a total concentration of 500 µg/L. Both the control MBR (MBRc) without pharmaceutical dosing and the MBR operated with high influent pharmaceutical concentrations (MBRe) were operated under room temperature with the same hydraulic retention time of 11 h and the same sludge retention time of 30 d. The removal efficiency rates of total nitrogen and total phosphorus were 83.2% vs. 90.1% and 72.6% vs. 57.8% in the MBRc vs. MBRe systems, and both MBRs achieved >98% removal of organics for a 180-day period. The floc size decreased, and membrane fouling became more severe in the MBRe system. Microbial diversity increased in the MBRe system and the relative abundances of functional microbe differed between the two MBRs. Furthermore, the total relative abundances of genes involved in glycolysis, assimilating nitrate reduction and nitrification processes increased in the MBRe system, which could account for the higher organics and nitrogen removal performance. This work provides insights for MBR operation in wastewater treatment with high pharmaceutical concentrations.

Assessment of the Anaerobic-Oxic-Anoxic (AOA) system on the removal of pharmaceuticals and the effect of recirculation on denitrification process

The human organism does not entirely absorb pharmaceuticals, which increasingly presence has been recorded in sanitary sewage. The complex chemical structure of these compounds interferes with their removal in wastewater treatment plants, resulting in their discharge into receiving water bodies. In this study, the performance of an Anaerobic-Oxic-Anoxic (AOA) system was evaluated in the treatment of synthetic wastewater containing 17α-ethinylestradiol (EE2), acetaminophen (ACE), and ibuprofen (IBU). In addition, the influence of recirculation rate was verified to improve nitrogen removal. In Phase 1, the AOA system achieved removal efficiencies higher than 87% for Chemical Oxygen Demand (COD), higher than 60% for Total Ammonia Nitrogen (TAN), 55% for EE2, 85% for IBU, and 99% for ACE when operated with 2.4 L h−1 at HRT of 8 h, and air flowrate of 5 L min−1. In Phase 2, with no addition of micropollutants, the system was operated with 2.4 L h−1 at HRT of 8 h, intermittent air flowrate of 5 L min−1 (3 h aeration; 1 h no aeration), under recirculation rates of 0%, 100%, and 200%. AOA system achieved COD removal efficiencies greater than 90% under these conditions. At 100% and 200% recirculation rates, nitrification increased from 83.6% to 85.3% and 89.4%, and denitrification from 28% to 79% and 88%, respectively. AOA system maintained high removal of organic matter and removal of pharmaceuticals greater than 50%, obtained mainly by biodegradation, in Phase I. In addition, recirculation, without adding external carbon source, improved denitrification in Phase II.

Carbon dioxide sequestration and wastewater treatment via an innovative self-sustaining algal microbial fuel cell

In this research, the utilization of an algal assisted-microbial fuel cell (AMFC) that employed photosynthetic microorganisms as cathode catalysts was demonstrated for the treatment of synthetic wastewater (SWW), power generation, and carbon sequestration. The power and biomass generation of two photosynthetic microorganisms, namely Chlorella sorokiniana and Tetradesmus sp., were evaluated. The electrogenic activity of Citrobacter frundii present in the SWW was analyzed using cyclic and linear sweep voltammetry. The AMFC exhibited a higher power density of 47.57 ± 0.95 mW/m3 with Chlorella sorokiniana in comparison to Tetradesmus sp. (46.56 ± 0.95 mW/m3). Additionally, the effect of CO2 supply on AMFC performance was investigated. The simultaneous treatment and energy recovery from low-grade waste such as SWW was found to be feasible with COD removal efficiency of 74 ± 0.6% in both AMFCs. Furthermore, the elementary analysis of lyophilized biomass of Chlorella sorokiniana and Tetradesmus sp in SWW-B showed maximum carbon content of 49.3% and 49.1%, respectively. The maximum biomass concentration and carbon fixation rate were determined to be 2.8 ± 0.03 g L−1 d−1 and 1.4 ± 0.001 g L−1 d−1, respectively for Chlorella sorokiniana. Additionally, the series of experimental results show that the stacked AMFCs had the capability to light the 3.0 V LED bulb. These findings suggest that AMFCs have the potential for sustainable bioelectricity generation and wastewater treatment with added benefits of carbon sequestration and biomass production.

Iron/carbon conductive materials for enhancing anaerobic treatment of synthetic acrylamide wastewater

AbstractBACKGROUNDMost studies have focused on the degradation of acrylamide (AM) by a single strain. There are relatively few studies on the treatment of AM by anaerobic activated sludge. Previous studies have shown that conductive particles can change the mode of electron transport between anaerobic microorganisms. Therefore, this study compared the enhancement effect of three different particles (Fe3O4, granular activated carbon (GAC), graphite) on the treatment of synthetic AM wastewater by anaerobic activated sludge under different temperature conditions (30, 25, 20 °C) and particle dose (2, 6 g L−1).RESULTSThe results showed that 6 g L−1 GAC improved the removal rate of chemical oxygen demand (COD) and AM by 22.95% and 19% compared with the control group at 30 °C, respectively, indicating that the addition of GAC contributes to the degradation of AM and improves COD removal rate. Results of high‐performance liquid chromatography (HPLC) showed that the activated sludge with GAC obviously promoted the degradation of AM. Besides, a large amount of propionic acid was detected in all experimental groups during the reaction, and the activated sludge with GAC promoted degradation of propionic acid.CONCLUSIONAnaerobic activated sludge supplemented with sufficient GAC can not only absorb and degrade AM synchronously but also accelerate the conversion of intermediates, such as acrylic and propionic acids. Based on the results of HPLC and liquid chromatography–mass spectrometry, a possible method of degradation of AM by anaerobic activated sludge was proposed. © 2023 Society of Chemical Industry (SCI).

Treatment of synthetic textile wastewater containing Acid Red 182 by electro-Peroxone process using RSM

The Azo dyes are primarily utilized in textile industries. Treatment of textile wastewater because of the presence of recalcitrant dyes using conventional processes is greatly challenging and ineffective. So far, no experimental work has been conducted on the decolorization of Acid Red 182 (AR182) in aqueous media. Hence, in this novel experimental work, the treatment of AR182 from the Azo dyes family was explored using the electro-Peroxone (EP) process. For the optimization of operating factors, including AR182 concentration, pH, applied current, and O3 flowrate in the decolorization of AR182, Central Composite Design (CCD) was utilized. The statistical optimization presented a highly satisfactory determination coefficient value and a satisfactory second-order model. The expected optimum conditions by the experimental design were as the following: AR182 concentration at 483.12 mg.L−1, applied current at 0.627,113 A, pH at 8.18284 and O3 flowrate at 1.13548 L min−1. The current density is directly proportional to dye removal. However, increasing the amount of applied current beyond a critical value has a contradictory impact on dye removal performance. The dye removal performance in both acidic and highly alkaline environments was negligible. Hence, ascertaining the optimum pH value and conduction of the experiment at that point is critical. At optimum points, the decolorization performance in predicted and experimental conditions for AR182 were 99 and 98.5%, respectively. The outcomes of this work clearly substantiated that the EP can be successfully utilized for the decolorization of AR182 in textile wastewater.

Benchmark and strategy development for microbial fuel cells in industrial wastewater treatment

The chemical energy hidden in wastewater can be extracted, turning an energy‐intensive treatment process into an energy‐independent one. However, conventional aerobic treat‐ ment is very energy intensive, and anaerobic treatment requires a post‐treatment step to meet stringent discharge requirements. Therefore, Microbial Fuel Cells (MFCs) have attracted a lot of attention because of their ability to extract electrical energy directly from wastewater during the treatment process. Since combustion losses can be avoided, theoretically the greatest energy value can be obtained from the organic load. However, most MFC research is currently still taking place on a laboratory scale in the treatment of synthetic or municipal wastewater. Commercialization of MFC technology will require large‐scale plants, for which a suitable MFC design and operation concepts must first be identified, since neither configuration nor operating system has been clearly established yet. In addition, no specific concepts and application fields currently exist for the treat‐ ment of industrial wastewater.Consequently, with regard to MFCs in industrial wastewater treatment, the aim of this work is to develop a benchmark that serves for modeling the required overall efficiency of MFCs and to identify the most relevant key factors in order to derive enhancement strate‐ gies. By providing an overview of current MFCs in industrial wastewater treatment and developing a benchmark, the targets for long‐term operation of MFCs can be established allowing critical factors for design and operation to be identified. The resulting enhance‐ ment strategies were validated and the overall evaluation with the developed benchmark allowed an assessment regarding the commercialization potential.Compared to the first MFC design (MFC 1.0), the enhanced MFC design (MFC 2.0) increased the power density by a factor of up to 11 and extended the long‐term stability to one year by increasing the specific cathode surface area and reducing the electrode spacing in conjunction with avoiding fiber clogging on the anode side. In addition to using beneficial brewery wastewater with high content of easily degradable organic acids and high conductivity, the performance of the MFC was further stabilized and improved by changing the operating mode to continuous operation and reducing the hydraulic re‐ tention time to 6 h, resulting in a mean organic removal rate of 6.5 ± 1.9 kg/(m3 · d). Although the overall energy efficiency is low compared to anaerobic treatment, the enor‐ mous wastewater treatment potential forms the basis for MFCs to become an alternative to conventional treatment technologies if self‐sufficient treatment is targeted. Due to the wide range of operating conditions and the modularity of stack systems, MFCs can become a promising option especially for industrial wastewater treatment.

Wastewater Treatment and Electricity Generation with Different Cathode Solutions in MFC

A microbial fuel cell (MFC) with cathode and anode chambers was utilized to generate power while simultaneously removing COD from wastewater. By utilizing various oxidant solutions, it is possible to increase the generated voltage. The anode chamber was used for anaerobic treatment of synthetic wastewater (approximately 1000 mg/L), whereas the cathode chamber contained various oxidant solutions such as dilute hydrogen peroxide (300 mg/L), KMnO4 (300 mg/L), K2Cr2O7 (300 mg/L) and Fenton reagent (H2O2/Fe(II), 300/20 mg/L). Aerobic wastewater treatment and intermittent ozonation were also tested in the cathode chamber. With intermittent ozonation of the cathode chamber, the highest power output (382 mW/m2) was obtained. At the conclusion of the operation period, the COD concentration in the anode chamber decreased from 1170 mg/L to 650 mg/L, resulting in nearly 45% COD removal. In the cathode chamber, the use of diluted KMnO4 and H2O2 solutions produced high power densities of 35 and 23 W/m2, respectively, while the other oxidants produced low power densities. At the end of 72 hours, the COD content of the anaerobic chamber decreased from 800 mg/L to nearly 333 mg/L, resulting in nearly 59% COD removal for the KMnO4 solution. Considering the high cost of ozonation, it is recommended that either aerobic wastewater treatment or dilute KMnO4/H2O2 solutions should be used in the cathode chamber for high power generation.

Electrocoagulation process for the decolorization of wastewater containing Reactive Red 195 and CFD simulation of the hydrodynamic in a continuous-flow single-channel reactor

Abstract The highly colored textile effluents require efficient treatment before being released into the environment. In this study, a continuous-flow single-channel reactor operating in closed- circuit was used to apply electrocoagulation for the treatment of synthetic textile wastewater. First, the characterization of the hydrodynamic within the reactor is evaluated by Computational Fluid Dynamics simulation using the k-ε turbulence model (Comsol Multiphysics®). Apart from a non-uniform distribution of the velocities inside the reactor, no particular anomaly was observed. Second, the decolorization efficiency was examined under various current intensities, electrolysis times, and initial dye concentrations. By operating under a current intensity of 100 mA instead of 50 mA, the required electrolysis time to achieve a decolorization efficiency of 80% decreased by 40%, while the specific electrode consumption remained slightly unchanged at about 0.19 kg Al·kg−1. At a current intensity of 100 mA and an electrolysis time of 26 min, and the increase in the initial dye concentration from 10 to 50 mg·L−1 the decolorization efficiency decreased remarkably while the specific electrode consumption was kept constant at about 0.15 kg Al·kg−1 dye removed. The knowledge obtained through this study can be used for the transposition from batch to continuous mode.