Electrochemical decolorization and degradation of Turquoise Blue G (TBG) by pre-adapted petroleum degrading bacteria

A converged approach of electro-biological process for decolorization and degradation of toxic synthetic dyes

Being one of the leading industries worldwide, the textile industry has been consuming large quantities of groundwater and discharging huge volumes of dye-contaminated effluents into our aquatic environment. Augmentation of water sources via reuse of treated effluents is therefore highly necessary. In the present study, the decolorization and degradation of synthetic toxic dye from an aqueous solution were investigated through an electro-biological route. Initially, decolorization of synthetic dye solutions (100, 500, and 1000 mg L^-1) was carried out by electrooxidation process using mixed metal oxide and titanium as anode and cathode, respectively. The electrooxidation solutions were further treated using bacteria (Pseudomonas aeruginosa) that were isolated from petroleum-transporting pipelines. UV-Vis, TOC, chemical oxygen demand, and NMR analyses revealed that the biodegradation process with electrooxidation enhanced the mineralization of the synthetic dye solutions. An optimum NaCl electrolyte concentration of 3 g L^-1 was sufficient to produce reactive species viz., free chlorine and hypochlorite, which are responsible for the Reactive Blue 19 (RB-19) decolorization. Among the three RB-19 concentrations, the highest removal percentage was noticed at 100 mg L^-1 (100%) with energy consumption and energy costs equal to 5.44 kWh m^-3 and 0.65 USD m^-3, respectively.

Integrated approach of photo-assisted electrochemical oxidation and sequential biodegradation of textile effluent

Synthetic azo dyes are extensively used in the textile industries, which are being released as textile effluent into the environment presence of azo dyes in the environment is great environmental concern therefore treatment of textile effluent is crucial for proper release of the effluent into the environment. Electrochemical oxidation (EO) is extensively used in the degradation of pollutants because of its high efficiency. In this study, photo-assisted electrooxidation (PEO) followed by biodegradation of the textile effluent was evaluated. The pretreatment of textile effluent was conducted by EO and PEO in a tubular flow cell with TiO₂-Ti/IrO₂-RuO₂ anode and titanium cathode under different current densities (10, 15, and 20 mA cm^-2). The chemical oxygen demand level reduced from 3150 mg L^-1 to 1300 and 600 mg L^-1under EO and PEO, respectively. Furthermore, biodegradation of EO and PEO pretreated textile effluent shows reduction in chemical oxygen demand (COD) from 1300 mg L^-1 to 900 mg L^-1and 600 mg L^-1to 110 mg L^-1, respectively. The most abundant genera were identified as Acetobacter, Achromobacter, Acidaminococcus, Actinomyces, and Acetomicrobium from the textile effluent. This study suggests that an integrated approach of PEO and subsequent biodegradation might be an effective and eco-friendly method for the degradation of textile effluent.

Fluorescence determination of chloramphenicol in milk powder using carbon dot decorated silver metal-organic frameworks

Carbon dot decorated silver metal-organic frameworks (CD-MOFs) were successfully synthesized at room temperature by adding CDs during the formation of Ag-MOFs. The CD-MOFs have excellent optical property, stability, and good fluorescence intensity in water compared with other solvents. The fluorescence intensity of CD-MOFs was relatively stable in the range of pH 5-9. It was used to construct a sensitive and reliable fluorescent sensor for the determination of chloramphenicol (CAP). When the CAP was introduced into the CD-MOFs, the fluorescence at 427 nm was quenched at the excitation wavelength of 332 nm. Wide linear relationships were established for CAP with a limit of detection of 44 nM. The fluorescent sensor has been applied to determine CAP in milk powder sample with satisfied recoveries (104 to 109%) and good precision (< 4%). The photoinduced electron-transfer is the most important mechanism contributing to the fluorescence quenching. The synthesized CD-MOFs provide a new orientation for fluorescence determination of chloramphenicol in real samples.

Enhanced biodegradation of hydrophobic organic pollutants by the bacterial consortium: Impact of enzymes and biosurfactants

Hydrocarbons and their derivative compounds are recalcitrant in nature and causing adverse impacts to the environment and are classified as important pollutants. Removal of these pollutants from the atmosphere is a challenging process. Hydrophobic organic pollutants (HOPs) including crude oil, diesel, dotriacontane (C₃₂), and tetracontane (C₄₀) are subjected to the biodegradation study by using a bacterial consortium consist of Bacillus subtilis, Pseudomonas stutzeri, and Acinetobacter baumannii. The impact of pH and temperature on the biodegradation process was monitored. During the HOPs biodegradation, the impact of hydrocarbon-degrading extracellular enzymes such as alcohol dehydrogenase, alkane hydroxylase, and lipase was examined, and found average activity about 47.2, 44.3, and 51.8 μmol/mg^-1, respectively. Additionally, other enzymes such as catechol 1,2 dioxygenase and catechol 2,3 dioxygenase were found as 118 and 112 μmol/mg^-1 Enzyme as an average range in all the HOPs degradation, respectively. Also, the impact of the extracellular polymeric substance and proteins were elucidated during the biodegradation of HOPs with the average range of 116.90, 54.98 mg/L^-1 respectively. The impact of biosurfactants on the degradation of different types of HOPs is elucidated. Very slight changes in the pH were also noticed during the biodegradation study. Biodegradation efficiency was calculated as 90, 84, 76, and 72% for crude oil, diesel, C_32, and C₄₀, respectively. Changes in the major functional groups (CH, C-O-C, CO, =CH₂, CH₂, CH₃) were confirmed by FTIR analysis and intermediated metabolites were identified by GCMS analysis. The surface-active molecules along with the enzymes played a crucial role in the biodegradation process.

Concept of Flocks Fragmentation and Averaging Method for the Application of Electrocoagulation in Process for Coke Oven Wastewater Treatment

The main objective of the article is to develop the concept of flock fragmentation and the averaging method for the application of electrocoagulation in the process of treating wastewater from coke ovens. The designed solution was part of an innovative system for the coke oven wastewater treatment process. The system is dedicated to removing the hazardous elements and compounds from wastewater from leaching ashes in municipal waste incineration plants. The design of the process and its automatization was based on a quantitative simulation method. The balance equations of mass, energy, and momentum of transport, complemented by the kinetics of the related reaction, are used during the calculation of the process. The main result achieved is a practical solution-the reactor's scheme, classified due to a patent procedure in the Polish Patent Office.

Biosurfactant mediated bioelectrokinetic remediation of diesel contaminated environment

The present study integrated the electrokinetic (EK) with bioremediation (Bioelectrokinetic -BEK) of diesel hydrocarbon by Staphylococcus epidermidis EVR4. It was identified as efficient biosurfactant producing bacteria and growth parameters was optimized using response surface methodology. Upon degradation, there is a complete disappearance of peaks from nonane (C₉) to tricosane (C₂₃) and 85%, 47% of degradation of pentacosane and octacosane respectively. Marine bacterial strain, EVR4 was found to be potential to degrade the diesel with a maximum degradation efficiency of 96% within 4 d, which was due to its synergistic role of biosurfactant and catabolic enzymes (dehydrogenase, catalase and cytochrome C). The application of integrated BEK was an effective insitu method for the remediation of diesel contaminated soil by BEK (84%) than EK (67%). EVR4 as an effective strain can be employed for BIO-EK method to clean the diesel hydrocarbon polluted environment.

Sequential electrochemical oxidation and bio-treatment of the azo dye congo red and textile effluent

Textile effluent is often difficult to manage as it contains a high concentration of toxic and recalcitrant synthetic dyes. In this study, congo Red and textile effluent were treated by electrochemical oxidation using RuO₂-IrO₂ coated titanium electrode as an anode followed by biodecolorization using Pseudomonas stutzeri MN1 and Acinetobacter baumannii MN3. Effluent pre-treatment is often necessary to minimize the inhibitory effects of textile dyes on dye degrading bacterial during bio-treatment. The pre-treatment of Congo Red by electrochemical oxidation for 10 min resulted in a decolorization rate of 98% at a pH, NaCl concentration, and current density of 7, 2 g L^-1, and 20 mA cm^-2. Subsequent bio-treatment of the pretreated Congo Red enhanced the biodegradation to 93%. The COD removal efficiency in real textile effluent following electrochemical pretreatment and biological treatment using bacterial consortium were 3.8% and 93%, respectively. Therefore, integrating electrochemical oxidation and microbial consortia offers an effective and environmentally friendly approach for treating complex industrial effluents.

Adsorption of Chloramphenicol on Commercial and Modified Activated Carbons

The aim of the study was to evaluate the possibility of applying commercial activated carbons currently used in water treatment plants and modified carbon at 400 and 800 °C in the atmosphere of air, water vapour and carbon dioxide to remove chloramphenicol. Adsorption kinetics was examined for solutions with pH of 2–10. Adsorption kinetics were determined for the initial concentration of chloramphenicol of 161 mg/dm3 and the adsorption isotherm was determined for the concentrations of 161 to 1615 mg/dm3. Of the analysed activated carbons (F-300, F-100, WG-12, ROW 08 Supra and Picabiol), the highest adsorption capacity was obtained for the use of Picabiol (214 mg/g), characterized by the highest specific surface area and pore volume. The pH value of the solution has little effect on the adsorption of chloramphenicol (the highest adsorption was found for pH = 10, qm = 190 mg/g, whereas the lowest—for pH = 6, qm = 208 mg/g). Modification of activated carbon WG-12 at 800 °C caused an increase in adsorption capacity from 195 mg/g (unmodified carbon) to 343 mg/g. A high correlation coefficient was found between the capacity of activated carbons and the total volume of micropores and mesopores. Among the examined adsorption kinetics equations (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion), the lowest values of the R2 correlation coefficient were obtained for the pseudo-first order equation. Other models with high correlation coefficient values described the adsorption kinetics. The adsorption results were modelled by means of the Freundlich, Langmuir, Temkin and Dubibin–Radushkevich adsorption isotherms. For all activated carbons and process conditions, the best match to the test results was obtained using the Langmuir model, whereas the lowest was found for the Dubibin–Radushkevich model.

Electrochemical decolorization of methyl red by RuO2-IrO2-TiO2 electrode and biodegradation with Pseudomonas stutzeri MN1 and Acinetobacter baumannii MN3: An integrated approach

Textile effluent consists of enormous quantities of toxic dyes, which are being discharged into natural aqueous system and thus contaminate the water quality. Hence it is important to develop an eco-friendly and cost effective technology to treat the dyes contaminated wastewater. In this research, an integrated approach of electrochemical oxidation (EO) and biodegradation process (BP) was studied of methyl red (MR) dye. In EO, RuO₂-IrO₂-TiO₂ is used as anode and titanium mesh electrode as cathode. This was followed by BP of the treated EO effluent. Various parameters viz., pH (5-10), sodium chloride concentrations (NaCl) (1-5 g L^-1) and current density (10-30 mA cm²) were optimized. The results of the EO showed 99.96% of MR decolorization within 10 min at pH of 5, NaCl of 2 g L^-1 and current density of 30 mA cm². The EO treated MR was further treated by BP Pseudomonas stutzeri MN1, Acinetobacter baumannii MN3 and mixed consortia of MN1 and MN3. The out of three treatments, the results of mixed consortium BP showed 90% removal of COD at the end of 24 h. The phytotoxic evaluation using Vigna radiata seeds confirmed the toxicity of untreated MR solution, whereas, 100% germination was observed in treated (biodegraded) MR solution. Overall these results evidenced that MR dye was completely decolorized and mineralized by EO and BP within 10 min and 24 h respectively. Hence, this integrated approach can be used as an effective degradation method to treat dyes in the textile industry.

An integrated (electro- and bio-oxidation) approach for remediation of industrial wastewater containing azo-dyes: Understanding the degradation mechanism and toxicity assessment

A hybrid approach for the remediation of recalcitrant dye wastewater is proposed. The chlorine-mediated electrochemical oxidation of real textile effluents and synthetic samples (using Ti/IrO2-RuO2-TiO2 anodes), lead to discoloration by 92% and 89%, respectively, in 100min, without significant mineralization. The remediation was obtained through biodegradation, after removing the residual bio-toxic active chlorine species via sunlight exposition. Results show that the electrochemical discoloration enhances the effluent biodegradability with about 90% COD removal employing acclimatized naphthalene-degrading bacterial consortia, within 144h. Based on results obtained through FT-IR and GC-MS, it is likely that azo group stripping and oxidative cleavage of dyes occur due to the nucleophilic attack of active chlorine species during electro-oxidation. This leads to generation of aromatic intermediates which are further desulfonated, deaminated or oxidized only at their functional groups. These aromatic intermediates were mineralized into simpler organic acids and aldehydes by bacterial consortia. Phyto-toxicity trials on Vigna radiata confirmed the toxic nature of the untreated dye solutions. An increase in root and shoot development was observed with the electrochemically treated solutions, the same was higher in case of bio-treated solutions. Overall, obtained results confirm the capability of the proposed hybrid oxidation scheme for the remediation of textile wastewater.

Improvement in treatment of soak liquor by combining electro-oxidation and biodegradation

A combined process involving electro-oxidation and biodegradation by halophilic bacteria was applied to treat wastewater effectively for discharge.

A simple strategy for monitoring of aromatic degradation in a chloride mediated electrooxidation process

UV-Vis spectrum analysis of textile dyeing wastewater during electrooxidation.