Decrease In Chemical Oxygen Demand Research Articles

EFFECT OF RECYCLING OF ELEMENTAL CHLORINE FREE BLEACHING EFFLUENT TREATED BY ELECTROCOAGULATION ON PAPER PROPERTIES

This study aimed to determine the effect of recycling elemental chlorine free (ECF) bleaching effluent (D0EpD1 and OD0EpD1) after treatment through electrocoagulation under optimum conditions on paper properties. The effect of pH, current density, time and dose of electrolyte on the reduction of chemical oxygen demand (COD) and color was studied. Maximum decrease in COD and color was found under optimum conditions (i.e., pH 7, treatment time of 30 min, current density of 29.16 mA/cm2, and 1 g/L NaCl). Under these optimum conditions, the reduction in COD and color was of 79.9% and 99.10%, respectively. The reduction in the strength properties of paper, caused by recycling, was found to be insignificant, but a decline of 2.11% for D0EpD1 and of 1.43% for OD0EpD1 in brightness was found. Using the electrocoagulation method to treat the bleaching effluent can prove to have valuable potential towards wastewater utilization, pollution control, and sustainable development of the industry.

Bio-energy generation and treatment of tannery effluent using microbial fuel cell

In this study, Graphite Particle (GP) and Carbon Cloth (CC) are employed as anode electrodes to study both bio-energy generation, and decrease of Chemical Oxygen Demand (COD) simultaneously using tannery effluent. The influence of electrodes distance (10 cm and 20 cm) on electricity production was evaluated. COD removal level of GP (75%) and CC (60%), maximum power outputs for 10 cm distance (600 ± 5 mW m−2) & (500 ± 10 mW m−2) and for 20 cm distance (520 ± 5 mW m−2) and also (430 ± 20 mW m−2) GP and CC were noted correspondingly. The outcomes of different parameters of MFC namely pH, conductivity, COD concentration, membrane thickness and size of bio-energy generation from tannery effluent in the MFC were investigated. The experimental results reveal that electrode provides highest power output with 10 cm distance between anode and cathode chamber. As a result, GP electrode is gradually viable, biocompatible, effective and adaptable for field application in MFC. The GP electrode has high potential for more power output, when compared to the CC electrode. The MFC system performance was improved with increasing effluent COD concentration (2340–4720 ppm), anolyte conductivity (1.6–8.1 mS cm−1) and membrane area (9–20 cm2). The system working with conductivity of 8.1 mS cm−1 and its effluent COD concentration of 4720 ppm generated the maximum peak power density of 44.69 mW m−2 with respective current density of 109 mA m−2. The findings thus show that considerable power production and effluent treatment can be achieved by MFC.

Treatment of thin stillage by Aspergillus oryzae and its effect on alcoholic fermentation in syrup liquid.

The microbial degradation of thin stillage for environment-friendly treatment has been studied extensively in recent years, and useful compounds in the treated-thin stillage are expected to be utilized in the subsequent fermentation. In this study, an Aspergillus oryzae H18, suitable for growing in thin stillage, was isolated from soil and served to degrade the organic matter in thin stillage, with the increase in pH (from 3·75 to 4·8) and decrease in chemical oxygen demand (COD, 81·3% removal rate). The effect of thin stillage as backset water after degradation of the strain H18 on alcohol production in syrup liquid was investigated. Compared with zero addition of thin stillage, the alcohol yield in mixed syrup liquid increased by 8·6% when the concentration of treated-thin stillage was 20%. After the addition of nutrients at proper concentration (0·5% urea, 1% molasses, 0·25% NaCl, 0·2% NaH2 PO4 , 0·3% MgSO4 and 0·25% CaCl2 ) in thin stillage, the alcohol yield in yeast fermentation was increased by 32·7% when mixed syrup liquid (with 40% thin stillage treated by H18) was employed, in comparison to control group without thin stillage addition. Meanwhile, the fermentation time was shortened, and alcohol production rate was enhanced.

Spatial variation of physicochemical parameters in a constructed wetland for wastewater treatment: An example of the use of the R programming language

Introduction: The implementation of wastewater treatment systems such as constructed wetlands has a growing interest in the last decade due to its low cost and high effectiveness in treating industrial and residential wastewater. Objective: To evaluate the spatial variation of physicochemical parameters in a constructed wetland system of sub-superficial flow of Pennisetum alopecuroides (Pennisetum) and a Control (unplanted). The purpose is to provide an analysis of spatial dynamic of physicochemical parameters using R programming language. Methods: Each of the cells (Pennisetum and Control) had 12 piezometers, organized in three columns and four rows with a separation distance of 3,25m and 4,35m, respectively. The turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (N-NH4), organic nitrogen (N-org.) and phosphorous (P-PO4-3) were measured in water under in-flow and out-flow of both conditions Control and Pennisetum (n= 8). Additionally, the oxidation-reduction potential (ORP), dissolved oxygen (DO), conductivity, pH and water temperature, were measured (n= 167) in the piezometers. Results: No statistically significant differences between cells for TKN, N-NH4, conductivity, turbidity, BOD, and COD were found; but both Control and Pennisetum cells showed a significant reduction in these parameters (P<0,05). Overall, TKN and N-NH4 removal were from 65,8 to 84,1% and 67,5 to 90,8%, respectively; and decrease in turbidity, conductivity, BOD, and COD, were between 95,1-95,4%; 15-22,4%; 65,2-77,9% and 57,4-60,3% respectively. Both cells showed ORP increasing gradient along the water-flow direction, contrary to conductivity (p<0,05). However, OD, pH and temperature were inconsistent in the direction of the water flow in both cells. Conclusions: Pennisetum demonstrated pollutant removal efficiency, but presented results similar to the control cells, therefore, remains unclear if it is a superior option or not. Spatial variation analysis did not reflect any obstruction of flow along the CWs; but some preferential flow paths can be distinguished. An open-source repository of R was provided.

Effects of Bacillus methylotrophicus WM‐1 on water quality dynamics and cultural fish in grass carp culture system

Microbial agents have been widely used in the Chinese aquaculture industry due to their advantages of enhancing the immunity of aquatic animal, improving disease resistance and improving the aquaculture environment. In previous studies, we found a highly antagonistic Aeromonas hydrophila strain, Bacillus methylotrophicus WM-1, isolated from grass carp (Ctenopharyngodon idella) culture systems. The purpose of this study was to investigate the impact of WM-1 on cultured water and fish. Strain WM-1 was mixed into the feed and fed to the grass carp for 30 days, set control group (CG, 0 CFU/g feed), low concentration group (LG, 103 CFU/g feed), medium concentration group (MG, 105 CFU/g feed) and high concentration group (HG, 107 CFU/g feed). Water quality and physiological indicators of grass carp were tested. Compared with CG, the concentrations of total phosphorus (TP) and soluble reactive phosphorus (SRP) were significantly increased in the MG in the early stage (before day 18, p < 0.05), whereas decreased in the long stage. After the 12th day, treatment groups showed a significant decrease in chemical oxygen demand (COD) (p < 0.05). Total nitrogen (TN), ammonia nitrogen (), nitrite () and nitrate () had no significant difference (p > 0.05). In grass carp serum, GPT activity in MG and HG was significantly reduced, SOD activity was significantly increased, and POD in MG was significantly higher than LG and HG (p < 0.05). In the liver, the GPT activity of the LG was significantly increased (p < 0.05). Other indicators (the specific growth rate and condition factor of grass carp, serum GOT, AKP and POD activity, total liver protein content, liver SOD, POD, AKP and GPT activity, haemocyte counts) have no significant difference between CG and treatment groups (p > 0.05). The results show that WM-1 is safe for water quality and culture objects, and has the effects of improving water quality and the immunity of grass carp. The corrent results combined with WM-1 effectively inhibit A. hydrophila shown that WM-1 can be applied to aquaculture production as a probiotics.

Optimizing Electro-oxidation, Electrocoagulation and Electro-Fenton processes for Treating Model Pesticide Wastewater containing Bromuconazole

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; In this work the removal efficiency of Bromuconazole and chemical oxygen demand (COD) from aqueous solution using different electrochemical processes (electro-oxidation process (EOP), electrocoagulation process (ECP) and electro- Fenton process (EFP) were investigated. All experiments were achieved at the natural pH of solution. The effects of some parameters such as current density and H2O2 concentration on COD and pesticide removal efficiency have been carried out at an initial pH of ˷8.45, current density 5,10,15,20 mA/cm2, an initial pesticide concentration of 300 mg/L, 5mM Na2SO4 support electrolyte and temperature of 30oC. The COD decrease at the end of 80 minutes of treatment from ˷1200 to 167.52 mg/L by EOP, to 248.26 mg/L by ECP, and to 237.94 mg/L by EFP. Results showed that a high COD reduction was obtained by EOP (85.59%), followed by EFP (80.48%) and electrocoagulation at (79.51 %) with a constant current density of 20, 20, 15 mA/cm2 respectively. The removal of bromuconazole pesticide exhibited a pseudo-second-order reaction with rate constant 0.0009 mg-1Lmin-1. Moreover, energy consumption, the cost of degradation and sludge formation were also determined.

Impact of Active Chlorines and •OH Radicals on Degradation of Quinoline Using the Bipolar Electro-Fenton Process

Quinoline is a typical nitrogenous heterocyclic compound, which is carcinogenic, teratogenic, and mutagenic to organisms, and its wastewater is difficult to biodegrade directly. The bipolar electro-Fenton process was employed to treat quinoline solution. The process/reaction conditions were optimized through the single factor experiment. The degradation kinetics of chemical oxygen demand (COD) was analyzed. To get the degradation mechanism and pathways of quinoline, the intermediate products were identified by gas chromatograph–mass spectrometer (GC–MS). By using sodium chloride as supporting electrolyte in the electro-Fenton reaction system with initial pH 3.0, conductivity 15,800 µs/cm, H2O2 concentration 71 mmol/L, current density 30.5 mA/cm2, and applied voltage 26.5 V, 75.56% of COD was decreased by indirect oxidation with electrogeneration of hydroxyl radicals (•OH) and active chloric species in 20 min. The COD decrease of quinoline solution followed the first order reaction kinetic model. The main products of quinoline degradation were 2(1H)-quinolinone, 4-chloro-2(1H)-quinolinone, 5-chloro-8-hydroxyquinoline, and 5,7-dichloro-8-hydroxyquinoline. Furthermore, two possible degradation pathways of quinoline were proposed, supported with Natural charge distribution on quinoline and intermediates calculated at the theoretical level of MN15L/6-311G(d).

Biological treatment of Hydrothermal Liquefaction (HTL) wastewater: Analytical evaluation of continuous process streams

In order to deal with hydrothermal liquefaction wastewater (HTWW), a new anaerobic-aerobic continuous process was developed. The process, which included a sequence of Up-Flow Anaerobic Sludge Blanket (UASB) and downstream aerobic Continuously Stirred Tank Reactor (CSTR), was tested on the HTWW obtained from Waste to Fuel® demo plant developed by ENI s.p.a. [1]. Performance of the system was evaluated in term of methane yield and chemical oxygen demand (COD) abatement capability. Detailed fate of organic compounds was evaluated through different analytical techniques, highlighting main issues and potential of HTWW biological treatment. The system was fed with neat HTWW (189 gCOD L−1) for 2.5 y, with variable organic loading rate (OLR) and minimal external inputs. UASB reactors converted most of HTWW organics into volatile fatty acids (VFA) and methane with concurrent precipitation of oily like insoluble, whereas aerobic CSTR removed VFA from anaerobic effluent. Under regime conditions (ORL equal to 0.5 gCOD L−1 d−1) COD decreased from 189 to 6.6 gCOD L-1, showing 97 % COD abatement with the coupled anaerobic-aerobic treatment. Such a COD abatement was obtained by means of multiple effects, namely biomethanation, precipitation of organic matter and aerobic oxidation of fermentation products (VFA produced in anaerobic digestion) and subsequent aerobic oxidation (in downstream aerobic reactor). These effects accounted for 43, 40 and 17 % of the total COD decrease, respectively. Inhibition phenomena were the key challenge for improving methane yields and system productivities. The overall results confirmed that valorization of HTWW is a feasible task, albeit rather challenging.

Ultrafiltration for the recovery of proteins from surimi washing water

The aim of this study was to evaluate the efficiency of the ultrafiltration process (UF) in the cleansing treatment of the tilapia surimi washing water and in the recovery of components. After producing surimi, the water generated in the washing operations was subjected to UF in a 30 kDa polyethersulfone membrane. Unfiltered washing waters and UF permeate and concentrate were analyzed for pH, total solids (TS) and fixed solids (FS), total proteins, and lipids. The chemical oxygen demand (COD) was determined in the original water and in the permeate. The concentrate was dehydrated in a spray dryer and analyzed for amino acids and carotenoids. The permeate showed a significant decrease in TS, proteins and COD, indicating that UF was efficient in removing the organic load from the waters. The percentage of protein recovery by UF was 93.12% and the dehydrated concentrate had all the essential amino acids, being leucine (5.47%), lysine (6.49%), valine (3.59%), and phenylalanine (3.68%) those with the highest concentrations, and also 0.67 mg/100 g of carotenoids. The application of UF has proved to be viable both in the recovery of valuable compounds and in the decontamination of water, contributing to the sustainability of the fish productive sector.

Evaluation of the aerobic and anaerobic degradation of an industrial effluent from vegetable tannery processing of leather on batch reactors

&lt;p&gt;In this study, the aerobic and anaerobic biodegradability of the industrial wastewater from the vegetable tanning process were evaluated. Water from a food wastewater treatment system was used as seed inoculum for the aerobic process and mature granular methanogenic sludge from a brewery industrial wastewater plant was used for the anaerobic process. The water from the tanning industry had a biological to chemical oxygen demand ratio of 33% with values of total chemical oxygen demand (COD) in the range of 342000 mg O2/L and total dissolved solids of 506595 mg/L. The assay of the tannery effluent under aerobic conditions resulted in a decrease of COD of 39.2% and a degradation of tannins lower than 12% after 26 days, while the anaerobic degradation showed a COD reduction of 65% with a 39% of degradation of tannins. The production of methane and Volatile Fatty Acids, during the anaerobic treatment, suggests a potential adaptation of biological organisms present in the mature anaerobic granular methanogenic sludge.&lt;/p&gt;&#x0D;

Protocol to select efficient microorganisms to treat coffee wastewater

The coffee processing wastewater (CPWW) requires treatment before being disposed of in the environment or reused due to its high organic and inorganic composition and a low pH. The indigenous microbiota from CPWW is highly diverse and could be selected as inoculums in treatment waste plants. Considering the physico-chemical characteristics of wastewater coffee, we elaborate on steps to select the microbial consortium that showed positive impact via decreasing the pollutant parameters of this effluent. The effectiveness was confirmed using wastewater from different origins with different chemical characteristics. A bacterial consortium composed by Serratia marcescens CCMA 1010 and CCMA 1012, Corynebacterium flavescens CCMA 1006, and Acetobacter indonesiensis CCMA 1002 was selected as the inoculums-based phenotypic assays. The mixed inoculum showed a highly active population (11.18 log CFU mL−1), promoting an 85% decrease in biochemical oxygen demand and a 60% decrease in chemical oxygen demand. There was also an 80% reduction in phosphorus and nitrogen. The final pH changed from 6.0 to 7.5. Additionally, the eco-toxicity using Daphnia similis was reduced by more than 59%. The microbial inoculum was efficient in the biological treatment in CPWWs, demonstrating the efficiency and robustness of the selected strains, independent of the physico-chemical characteristics of wastewater.

Combining photocatalytic process and biological treatment for Reactive Green 12 degradation: optimization, mineralization, and phytotoxicity with seed germination.

In this study, we show that the combination of a photocatalytic process (as a pretreatment step) combined with the conventional biological treatment of wastewaters can improve the process and achieve satisfactory efficiency. In this context, Reactive Green 12 (RG-12) solutions were photocatalytically pretreated using TiO2-impregnated polyester as supported catalyst under UV light in batch reactor. Photocatalysis as pretreatment (during 4 and 8h of irradiation) was combined with 7days of aerobic biological treatment using activated sludge. As first assays, respiratory tests revealed that the removal of RG-12 was improved by 5.4% and 11.7% for the solutions that were irradiated for 4 and 8h in the presence of TiO2, respectively. However, 34.5% and 19% of dye solution was discolored after 7days of biological treatment for the pretreated solutions during 4 and 8h of UV light exposure, respectively. The discoloration efficiency obtained by the combined processes achieved 59.6% and 74.9% for the samples under photocatalysis during 4 and 8h, respectively. A significant decrease in chemical oxygen demand (COD) of about 74.9% was achieved after photocatalysis/biodegradation processes. In addition, a decrease in the phytotoxicity was obtained as followed by the germination index (GI) values of cress seeds that increased from 46.2 to 88.7% after 8h of photocatalysis and then to 92.8% after further 7days of biological treatment.

Effects of Hydraulic Retention Time, COD/SO42− Ratio, Influent Iron Concentration, and Sulfate Kinetics on Treatment of a Synthetic Acid Mine Drainage

The effects of hydraulic retention time (HRT), chemical oxygen demand (COD), and influent Fe2+ concentrations were studied in an up-flow anaerobic sludge blanket reactor for acid mine drainage treatment using whey as a carbon source. The reactor was operated in four phases: phase I: HRT of 16 h, COD/SO42− ratio of 1.0, and an influent Fe2+ of 100 mg/L; phase II: HRT of 16 h, COD/SO42− ratio of 0.8, and an influent Fe2+ of 100 mg/L; phase III: HRT of 24 h, COD/SO42− ratio of 0.8, and an influent Fe2+ of 100 mg/L; and phase IV:HRT of 24 h, COD/SO42− ratio of 0.8, and an influent Fe2+ of 200 mg/L. The best performance was in phase I, with sulfate removal of 70 ± 8%, COD removal of 80.8 ± 7.3%, effluent pH of 6.7 ± 0.17, and sulfide generation of 91.5 ± 30.3 mg/l. The reactor reduced Cu concentrations by 92.4 ± 2.7%, Zn by 48.5 ± 4.0%, and Fe by 99.4 ± 0.4% for the entire study. Increasing the HRT and COD/SO42− ratio caused a decrease in COD and sulfate removal. The increase in influent Fe2+ in phase IV improved the results, but not enough to reestablish the phase I results. Still, the reactor presented steady metal removal and sulfide generation during the entire study.

The Membrane-Less Microbial Fuel Cell (ML-MFC) with Ni-Co and Cu-B Cathode Powered by the Process Wastewater from Yeast Production

Research related to measurements of electricity production was combined with parallel wastewater parameter reduction in a membrane-less microbial fuel cell (ML-MFC) fed with industry process wastewater (from a yeast factory). Electrodes with Ni–Co and Cu–B catalysts were used as cathodes. A carbon electrode (carbon cloth) was used as a reference due to its widespread use. It was demonstrated that all analyzed electrodes could be employed as cathodes in ML-MFC fed with process wastewater from yeast production. Electricity measurements during ML-MFC operations indicated that power (6.19 mW) and current density (0.38 mA·cm−2) were the highest for Ni–Co electrodes. In addition, during the exploitation of ML-MFC, it was recorded that the chemical oxygen demand (COD) removal per time for all types of electrodes was similar to the duration of COD decrease in the conditions for wastewater aeration. However, the COD reduction curve for aeration took the most favorable course. The concentration of NH4+ in ML-MFC remained virtually constant throughout the measurement period, whereas NO3− levels indicated almost complete removal (with a minimum increase in the last days of cell exploitation).

Photocatalytic oxidative degradation of hydrocarbon pollutants in refinery wastewater using TiO2 as catalyst.

This study reports the photocatalytic oxidative degradation of hydrocarbon pollutants present in refinery wastewater under UV light using Fe2 O3 , MnO2 , TiO2 , and ZnO as catalysts. Among the catalysts, TiO2 exhibited the highest photocatalytic degradation activity, that is, 92, 98.8, 91.5, and 93% conversion for benzene, toluene, phenol, and naphthalene, respectively, in the model refinery wastewater under the optimum reaction conditions of pH 3, 30°C, 90-min reaction time, and 100mg/L catalyst dose. The photocatalytic degradation of a real refinery wastewater sample containing 69.23% aliphatics, 25.36% aromatics, 3.2% oxygenates, and 2.21% naphthenic hydrocarbons under the optimum conditions revealed a net decrease in chemical oxygen demand (93.2%), that is, from 970mg/L to 65mg/L. GC-MS analysis of the reaction products confirmed that using UV/TiO2 system, complete photodegradation of the parent hydrocarbons occurred, but some oxygenated byproducts were also observed. This study provides useful reference information for the treatment of wastewater from oil refineries to cope with the increasing environmental issues. PRACTITIONER POINTS: Benzene, toluene, phenol and naphthalene were successfully degraded by UV/TiO2 system, under 30°C, 1hr, pH 3 and 100mg catalyst. Photocatalytic oxidation of Refinery wastewater (Attock Oil refinery, Pakistan), UV/ TiO2 system resulted in 93.92% COD removal. GC-MS analysis shows complete removal of parent hydrocarbons from refinery wastewater, leaving only traces of oxygenated hydrocarbons as oxidation byproducts.

Studies on decreasing Chemical Oxygen Demand (COD) and Phosphate on laundry wastewater using anaerobic and phytoremediation with algae plants (Hydrillaverticillata)

In reducing the pollutant load contained in laundry wastewater such as COD and phosphate levels can be processed through anaerobic process and will be followed by phytoremediation methods. The purpose of this study is to reduce levels of COD and phosphate in laundry wastewater. This research was conducted in a laboratory scale with variations in plant mass. One type of aquatic plants that has the potential in phytoremediation waste management is algae (Hydrillaverticillata). The initial step in this research was carried out the seeding stage in anaerobic reactors with the aim of breeding bacteria with a suspended culture method which was marked by a decrease in COD with +10% fluctuations. Followed by the running stage in the anaerobic reactor until the reduction in COD ≥60% then, the stage of neutralization and acclimatization of plants with the aim of removing impurities in plants and adaptation of plants with microorganisms in wastewater. The last stage is the running stage of the phytoremediation process which is carried out by observing the value of COD and Phosphate in wastewater with variations in plant mass of 50, 100, 150, 200 and 250 grams in each reactor with contact time treatment for 7 days. Based on the analysis of COD parameters for each plant after anaerobic and phytoremediation processes on the last day the average efficiency of COD removal at 50 grams of plant mass is 86.34%, 100 gram plant mass of 81.81%, plant mass of 150 grams of 85.21%, 200 gram plant mass of 90.87% and 250 gram plant mass of 87.47% while the results of the analysis of Phosphate COD parameters for each plant the average removal efficiency of Phosphate in 50 gram plant mass is -25 %, 100 gram plant mass of -298.81%, 150 gram plant mass of -417.86%, 200 gram plant mass of -501.19% and 250 gram plant mass of -462.5%.

Sonophotocatalytic degradation of sulfadiazine by integration of microfibrillated carboxymethyl cellulose with Zn-Cu-Mg mixed metal hydroxide/g-C3N4 composite

This research aimed to prepare a recoverable sonophotocatalyst, in which microfibrillated carboxymethyl cellulose (MFC) acted as the Zn-Cu-Mg-mixed metal hydroxide/graphitic carbon nitride (MMH/g-C3N4) carrier. The characteristics of bare and composite sonophotocatalysts were analyzed by the XRD, FT-IR, BET, DRS, PL and FE-SEM equipped with the EDX mapping. The performance of prepared composites (MMH/g-C3N4@MFC) with various weight ratios of the MMH/g-C3N4 was studied for the sonophotocatalytic degradation of sulfadiazine (SDZ) as the model emerging contaminant. 93% of SDZ was degraded using the most effective catalyst (MMH/g-C3N4@MFC3) with 15% weight ratio of the MMH/g-C3N4 under the desired operating conditions including solution pH of 6.5, SDZ concentration of 0.15 mM and ultrasonic power of 300 W. The MMH addition to the g-C3N4 structure increased the separation of charge carriers generated via the visible light or ultrasound irradiations. Moreover, the MMH/g-C3N4 was dispersed uniformly on the MFC and consequently, more active sites were available to form reactive oxygen species (ROS), compared to powder form. Hydroxyl radicals (•OH) were determined as the main ROS in the SDZ degradation by performing a series of scavenging experiments. Less than 10% decrease in the degradation efficiency of SDZ was observed during five subsequent experiments, which indicated the proper retention of the MMH/g-C3N4 particles in the MFC. The adequate mineralization of SDZ (83% decrease in chemical oxygen demand (COD)) was obtained after 200 min of treatment. Eventually, ten degradation intermediates were identified by the GC-MS analysis and a plausible degradation mechanism for the contaminant was proposed.

Electro-oxidative decolorization and treatment of model wastewater containing Acid Blue 80 on boron doped diamond and platinum anodes

This paper aims to study the decolorization and degradation of textile dye Acid Blue 80 using indirect electrochemical oxidation on active platinum (Pt) and non-active boron doped diamond (BDD) anodes in the presence and formation of chloride ions. Ultraviolet-visible (UV–VIS) spectroscopy helped to monitor the rate of decolorization in relation to the amount of electrolyte, input voltage as well as current density. The effect of pH on the rate of decolorization was also assessed. Following the decolorization of model wastewater, we monitored the subsequent degradation of Acid Blue 80 by repeatedly measuring the values of total organic carbon (TOC), total nitrogen (TN), chemical oxygen demand (COD) and adsorbable organically bound halogens (AOX). Using liquid chromatography-mass spectrometry (LC-MS), we analyzed the reaction mixture and examined the mechanism of Acid Blue 80 decomposition both with the presence and with the exclusion of chloride ions. In the presence of chloride ions, oxidation was also accompanied by substrate chlorination, along with the formation AOX. Their concentration culminated between 6 and 12 h of electro-oxidation, which was then followed by a decrease in AOX values across the entire pH range of 3.0–11.0. After 24 h, Acid Blue 80 was mineralized by 90% at pH = 3.0 on the BDD anode, coupled with a 99% decrease in COD. Under the same conditions, the Pt anode showed a 94% decrease in COD and 64% in TOC.

Dual Valorization of Olive Mill Wastewater by Bio-Nanosynthesis of Magnesium Oxide and Yarrowia lipolytica Biomass Production.

This research investigates an efficient dual valorization of olive mill wastewater in the biosynthesis of magnesium oxide nanoparticles and in the depollution of the effluent by Yarrowia lipolytica growth evaluation. After removal of polyphenols, the recovered biophenols were reacted with the magnesium precursor to provide magnesium oxide nanoparticles. In order to confirm the biosynthesized magnesium oxide nanoparticles, several analyses were undertaken. The Fourier transform infrared spectrum gives a broad absorption at 658 cm-1 confirming the presence of the magnesium oxide nanoparticles, while the UV/VIS absorption spectroscopy reveals an intense transition with a maximum absorption at 300 nm. The X-ray diffraction and transmission electron microscopy analyses show that nanoparticles are in pure cubic crystalline with spherical and hexagonal shapes (average size is 19.4 nm). The zeta potential analysis illustrates a negative potential proving a good stability of the biosynthesized nanoparticles. Nanoparticles were assigned for their in vitro antibacterial activity against Escherichia coli, Enterobacter aerogenes, Salmonella typhimurium, Staphylococcus cohnii, and Bacillus niacini. The evaluation of the growth of Yarrowia lipolytica on the recovered olive mill wastewater after removal of polyphenols yielded 3.2 g/L of the Yarrowia biomass in 72 h without nutriment additions, providing an important decrease of chemical oxygen demand (73 %).

Integrated electrochemical processes for textile industry wastewater treatment: system performances and sludge settling characteristics

Textile wastewater containing toxic dyes needs efficient treatment before being released into the environment. Certain dyes are known or presumed to have carcinogenic potential for humans. In this work, hybrid electrochemical processes including electrocoagulation (EC) alone and combined with electro Fenton (EF), anodic oxidation (AO) and peroxi-coagulation (PC) were tested to treat real textile wastewater using a batch reactor. A sequential EC and EF (EC-EF) process was found to be more effective. The experimental results indicated that the effectiveness of the treatment decreases in the following order: EC-EF > EC-AO > EC-PC > EC. EC-EF results showed a decrease in chemical oxygen demand (COD, 97%), total organic carbon (98%), total suspended solids (98%), and the concentration of metal species; showing that the treatment of such wastewater type can be achieved by combined EC-EF process in a one-pot bench-scale reactor. The electrical energy consumption, the iron dissolution, and the biological oxygen demand/COD ratios of EC and EC-EF processes were evaluated. Characterization of the sludge generated during EC treatment at current density of 20 mA cm− 2 was carried out. Precipitation, adsorption, and electrochemical oxidation/reduction of organic dyes and metallic ions occurred during the treatment. This investigation shows the efficiency of combined EC-EF to treat textile wastewater.