Total Organic Carbon Reduction Research Articles

Photocatalytic decomposition of metronidazole by zinc hexaferrite coated with bismuth oxyiodide magnetic nanocomposite: Advanced modelling and optimization with artificial neural network

The objective of the present study was to employ a green synthesis method to produce a sustainable ZnFe12O19/BiOI nanocomposite and evaluate its efficacy in the photocatalytic degradation of metronidazole (MNZ) from aqueous media. An artificial neural network (ANN) model was developed to predict the performance of the photocatalytic degradation process using experimental data. More importantly, sensitivity analysis was conducted to explore the relationship between MNZ degradation and various experimental parameters. The elimination of MNZ was assessed under different operational parameters, including pH, contaminant concentration, nanocomposite dosage, and retention time. The outcomes exhibited high a desirability performance of the ANN model with a coefficient correlation (R2) of 0.99. Under optimized circumstances, the MNZ elimination efficiency, as well as the reduction in chemical oxygen demand (COD) and total organic carbon (TOC), reached 92.71%, 70.23%, and 55.08%, respectively. The catalyst showed the ability to be regenerated 8 times with only a slight decrease in its photocatalytic activity. Furthermore, the experimental data obtained demonstrated a good agreement with the predictions of the ANN model. As a result, this study fabricated the ZnFe12O19/BiOI nanocomposite, which gave potential implication value in the effective decontamination of pharmaceutical compounds.

Sustainable green synthesis of SnO2 quantum dots: A stable, phase-pure and highly efficient photocatalyst for degradation of toxic dyes

A facile, scalable, green, convenient, high yield and environmentally sustainable strategy has been devised to synthesize SnO2 quantum dots as fine amorphous powder using an aqueous extract of edible and abundantly available marine alga, Ulva sp. The phytochemicals present in the alga have served as capping and stabilizing agent in the synthesis. The structure, morphology, optical properties and chemical oxidation state of the materials were investigated by UV–Vis, FT-IR, Raman, XRD, XPS, TEM, SEM, EDAX and BET techniques. The size of as-synthesized SnO2 nanoparticles were <5 nm indicating the formation of quantum dots (QDs). Retrievable and reusable, the as prepared SnO2 QDs served as highly efficient photocatalyst for fast degradation of water soluble toxic dyes viz., methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) individually, also their binary mixtures, MB-MO, MB-RhB and ternary mixtures MB-MO-RhB under naturally available scattered sunlight. A significant reduction in total organic carbon (TOC) by the SnO2 QDs catalyst suggests that it efficiently converted MB, MO, and RhB dyes into less harmful intermediate products or directly into CO2 and H2O, making them environmentally benign. The catalytic performances of the newly prepared material were assessed to be much higher than several reported SnO2 or metal doped SnO2 nanomaterials. The as-synthesized SnO2 QDs photocatalyst could be recovered reused for at least five consecutive catalytic cycles without any decline in efficiency indicating the high stability of the photocatalyst.

Simultaneous removal of sulfamethazine and sulfate via electrochemical oxidation and capacitive Deionization: Mechanisms of in-situ activation and strategies of the hybrid system

Electrochemical oxidation (EO) is a well-established method for pollutants removal. However, excessive addition of oxidant during EO may cause secondary pollution. Moreover, the unprocessed ions in the wastewater can cause further contamination. This research introduces a hybrid process that combines EO with capacitive deionization (CDI), in situ catalytically utilizing sulfate (SO42-) and removing sulfamethazine (SMZ). This process realized by layered porous MXene-modified biochar electrodes (BCM) that demonstrate electrocatalytic and adsorption properties. The electrochemical oxidation system, constructed using BCM cathode and boron-doped diamond anode, harnesses in situ generation of oxidants from SO42-, leading to the complete degradation of 30 mg/L sulfamethazine in 30 min through adsorbed radicals and metastable active species at the biphasic interface. Subsequently, the BCM-2 exhibits excellent CDI performance at 1.2 V, achieving a desalination capacity of 15.40–65.97 mg/g in 100–1000 mg/L Na2SO4 solution. By combining EO with CDI, BCM simultaneously removes sulfamethazine and sulfate, resulting in a 60 % reduction in total organic carbon and a 14.4 % decrease in electrical conductivity after one process cycle. Moreover, BCM exhibits favorable cytocompatibility.

Batch electrocoagulation system for the treatment of Borneo urban river in relation to the industrial zone

Urbanization activities on Borneo Island have degraded the water quality of some urban rivers due to increased anthropogenic activities which leading to elevated levels of total organic carbon (TOC) and reduced access to clean water sources. As such, this study aims to develop a batch electrocoagulation treatment system to reduce the TOC levels in Borneo urban river for domestic consumption. Correspondingly, this study analyses the effect of electric current and residence time on TOC reduction efficiency. Subsequent, this study has found that the TOC levels in treated urban river water met domestic consumption safety standard by utilizing a batch electrocoagulation treatment system at 5 A of electric current and 25 minutes of residence time. The treatment system achieves 82.83% of maximum TOC reduction efficiency by decreasing the initial TOC levels from 5.65 mg/L to 0.97 mg/L. The energy operating cost analysis done in this study has reported that electrocoagulation treatment system could generate 116.51 g Al(OH)3 per meter cubic of urban river water at a cost of United States Dollars (USD) 0.32 per m3. Additionally, the reduction of TOC levels in urban river by using in-situ aluminium hydroxide coagulants follows Freundlich isotherm model with a regression coefficient of 0.99, thus, exhibiting a multilayer adsorption. The aluminium hydroxide coagulants could reduce TOC from urban river at 1.40 min−1 of adsorption rate and 0.20 mg/g of maximum adsorption capacity. From the energy dispersive X-ray analysis conducted, this study has observed the presence of electrocoagulation flocs that are constituted with aluminium hydroxide coagulants and carbon element which indicated the occurrence of adsorption process. Overall, this study demonstrates that the batch electrocoagulation treatment system could be utilized to reduce the TOC level from Borneo urban river with an adsorption process which is deemed suitable for domestic consumption at a reasonable cost.

Activation of periodate by biocarbon-supported multiple modified nanoscale iron for the degradation of bisphenol A in high-temperature aqueous solution.

As reported, the persistent toxic and harmful pollutant bisphenol A (BPA) from industrial emissions has been consistently found in aquatic environments inhabited by humans. Periodate (PI)-based advanced oxidation processes (AOPs) have been employed to degrade BPA, although activating PI proves more challenging compared to other oxidants. A novel nano iron metal catalyst, sulfided nanoscale iron-nickel bimetallic nanoparticle supported on biocarbon (S-(nFe0-Ni)/BC) was synthesized and utilized to activate PI for the removal of BPA. The morphology, structure, and composition of S-(nFe0-Ni)/BC were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), and fourier-transform infrared spectrum (FTIR). The catalyst demonstrates an excellent ability to activate PI, achieving a BPA removal efficacy of 86.4%, accompanied by a 33% reduction in total organic carbon (TOC) in the {S-(nFe0-Ni)/BC}/PI system. BPA degradation exhibited a significant change at the 5-min mark. In the first stage (0-5min), nonlinear dynamic fitting research, combined with scavenging experiments, unveiled the competitive degradation of pollutants primarily driven by iodate radical ( ), singlet oxygen , and hydroxyl radical ( ). The competitive dynamics aligned with the ExpAssoc model. The contribution rates of different active species during the second stage (5-120min) were calculated. The contributions of main species to BPA removal follow the order of > > throughout the entire process. The influence of various parameters, such as the dosage of S-(nFe0-Ni)/BC, initial PI concentration, BPA concentration, pH, temperature, and the presence of coexisting anions, was also examined. Finally, a plausible reaction mechanism in the system is proposed, suggesting that the {S-(nFe0-Ni)/BC}/PI system involves a heterogeneous synergistic reaction occurring primarily on the surface of S-(nFe0-Ni)/BC. Therefore, this study proposes a promising approach for PI-based AOPs to degrade organic pollutants, aiming to mitigate the irreversible harm caused by such pollutants to organisms and the environment.

Enhanced photodegradation of oxytetracycline antibiotic in wastewater by implementing ZnO-loaded carbon fiber

The antibiotic oxytetracycline (OCA) exhibits high insolubility in the natural environment, posing a significant challenge for its removal. This study synthesized a porous structure and a high-surface-area carbon fiber, incorporating zinc oxide (ZnO/CFB) for the effective removal of OCA in wastewater. The material characterization revealed exceptional optical and photochemical properties of ZnO/CFB, featuring a reduced band gap energy of 2.7 eV. ZnO/CFB exhibited robust performance in the photodegradation of OCA in wastewater, achieving an impressive removal efficiency of 86.7%. Remarkably, the reduction of total organic carbon (TOC) reached an outstanding 97.5%. LC-MS analysis confirmed the complete oxidation of OCA and its intermediates, transforming them into inorganic substances within 60 min. This study introduces an efficient strategy for eliminating antibiotic pollutants from wastewater, highlighting the potential of ZnO/CFB as an effective and stable photocatalyst for environmental remediation.

Assessment of Microplastics in Hanumante River of Kathmandu Valley

Plastic debris is one of the most significant organic pollutants in the aquatic environment. Researchers are currently focusing on the impact of micro and nano-scale plastic waste on aquatic systems. In this study, we investigated the distribution of plastic pellets and fragments present in the freshwater ecosystem. The goal was to assess microplastic (MP) abundance in the Hanumante River, a tributary of the Bagmati River, and analyze their properties. Sample collection involved the bottle sampling method. Filtration, wet peroxide oxidation, density separation, gravimetric analysis, and microscopic examination were performed to study the characteristics of microplastics. The study was conducted by following the guidelines of the National Oceanic and Atmospheric Administration (NOAA) protocol. Gravimetric analysis was applied to calculate the reduced mass of the sample after total organic carbon reduction. Results showed that the maximum amount of reduced sample was obtained from the sample taken from sample taken from Madhyapur Thimi area (~3.593g) and the minimum amount of reduced sample was obtained from the sample taken from the Shiva temple Jagati area (~2.130g). Microscopic inspection showed that samples taken from different locations were composed of an average of 14–23 microplastics per liter of sample. FT-IR analysis was performed to analyze the characteristics of microplastics and the type of polymers present in the sample which showed the abundance of polymer materials like polyethylene, polypropylene, and polycarbonates. The findings imply that appropriate plastic waste management measures be implemented in the communities to safeguard the ecosystem benefits derived from the river.

Assessment of the potentials of Autochthonous lipase-producing bacteria in the treatment of palm oil mill effluent

Pollution caused by the release of untreated palm oil mill effluent (POME) is a major environmental concern. This research assessed the potentials of single and consortium ofautochthonous lipase-producing bacteria as a non-invasive procedure in the biotreatment ofPOME. The identity of lipase-producing bacteria in POME were determined using morphological and biochemical techniques. Identified isolates were monitored for POME utilization by measurement of optical density at 600 nm in 25 ml Bushnell Haas broth supplemented with 0.25 ml sterilized POME. Individual isolates and consortium were then used for the bioremediation of POME. Quality parameters including pH, total suspended solid (TSS), oil and grease, chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), total organic matter (TOM) and total nitrogen (TN) of the raw and treated effluents were evaluated. The population (CFU/ml) of total heterotrophic, POME - utilizing and lipolytic bacteria were 3.9 x 106, 2.8 x 106 and 3.5 x 105 respectively. The lipolytic bacterial isolates include Brenneria nigrifluens, Bacillus circulans and Paenibacillus pectinilyticus. Results revealed varying pH of 5.03 and 6.81 - 7.26 for untreated and treated respectively. The lipolytic bacteria from POME caused reduction efficiency of 100% in TSS and oil and grease contents of the treated effluents relative to the raw samples. The COD, BOD, TOC, TOM and TN reduction ranged 17.90 - 93.55, 1.66 - 90.52, 16.34 - 59.79 %, 6.18 - 80.78 % and 11.71 - 93.66 % respectively. This research indicated that POME indigenous lipase-producing bacteria improved POME quality and therefore suggestive of their potentials in the bioremediation of POME-contaminated environment with the consortium being most effective.

Advancing continuous flow techniques in effective trimethoprim oxidation: combatting bacterial resistance in wastewater.

This work describes an innovative catalytic process for aqueous trimethoprim degradation, using a fixed-bed continuous flow reactor packed with a manganese(III) meso-substituted porphyrin covalently immobilized functionalized aminopropyl silica gel as the catalyst and H2O2 as a green oxidant. It exhibits remarkable activity and stability, maintaining its performance over extended periods (up to 8 hours) and achieving significant reductions in total organic carbon (TOC = 80%). Importantly, microbiological assays confirmed that this degradation process effectively converts trimethoprim into non-resistance-inducing products.

Bentonite/cerium-modified LDH composite catalyst for catalytic ozonation of high-concentration indigo carmine dye solution

This research tackles the pressing issue of high-concentration indigo carmine (IC) dye degradation, where concentrations reach as high as 6000 mg/L. We synthesized a novel catalyst comprising a bentonite-supported cerium-modified magnesium-aluminum layer double hydroxide (Mg-Al-Ce LDH) composite. Our investigation focused on the catalytic prowess of two versions of this catalyst in decolorizing and degrading the IC dye. Remarkably, these catalysts swiftly decolorized the dye solution within 20 min and achieved an impressive 95% Total Organic Carbon (TOC) removal in 60 min, significantly outperforming the 50% TOC reduction by ozonation without a catalyst. Bentonite's role as a support material was crucial, bolstering the catalysts' stability in demanding conditions. This study heralds a breakthrough in high-concentration dye waste treatment, marking a significant stride toward eco-friendly wastewater management practices.

Comparison of the PFAS and physical-chemical parameter fluctuations between an ash landfill and a MSW landfill

Studies of per- and polyfluoroalkyl substances (PFAS) fluctuations at landfills have focused on municipal solid waste (MSW) leachate. Few studies exist that evaluate fluctuations (defined by the coefficient of variation, CV) in MSW incinerator ash (MSWA) landfill leachate and that evaluate PFAS fluctuations in stormwater, groundwater, and treated liquids on-site. In this study, aqueous landfill samples (leachate, treated leachate, stormwater, gas condensate, ambient groundwater, and effluent from a groundwater remediation system) were collected from a MSW and an MSWA landfill geographically located within close proximity (less than 40 km). The objective of this study was to compare the leachate compositions between these two landfill types and to evaluate temporal variations. Results indicated that the CV of total detected PFAS concentrations in leachate was higher for the MSW landfill (CV = 43 %) compared to the MSWA landfill (CV = 16 %). The total detected PFAS concentration in MSW leachate samples (mean: 9641 ng/L) was higher than in MSWA leachate samples (mean: 2621 ng/L) (p < 0.05). Within a landfill, PFAS concentrations were correlated (rs > 0.6, p < 0.05) with alkalinity, total organic carbon (TOC), and ammonia. Results from the on-site leachate treatment system at the MSW landfill indicated reductions in COD, TOC, and ammonia; however, the ∑26PFAS concentration increased 3 % after the treatment. Overall, results demonstrated that differences between landfill types and fluctuations in PFAS within landfills should be considered when designing landfill leachate collection and treatment systems to remove PFAS. The comparative analysis in this study can provide insights into optimizing leachate management for MSW and MSWA landfills.

Sequential use of a continuous-flow electrocoagulation reactor and a (photo)electro-Fenton recirculation system for the treatment of Acid Brown 14 diazo dye

The decolorization and TOC removal of solutions of Acid Brown 14 (AB14) diazo dye containing 50 mg L−1 of total organic carbon (TOC) have been first studied in a continuous-flow electrocoagulation (EC) reactor of 3 L capacity with Fe electrodes of ∼110 cm2 area each. Total loss of color with poor TOC removal was found in chloride, sulfate, and/or hydrogen carbonate matrices after 18 min of this treatment. The best performance was found using 5 anodes and 4 cathodes of Fe at 13.70 A and low liquid flow rate of 10 L h−1, in aerated 39.6 mM NaCl medium within a pH range of 4.0–10.0. The effluent obtained from EC was further treated by electro-Fenton (EF) using a 2.5 L pre-pilot flow plant, which was equipped with a filter-press cell comprising a Pt anode and an air-diffusion cathode for H2O2 electrogeneration. Operating with 0.10–1.0 mM Fe2+ as catalyst at pH 3.0 and 50 mA cm−2, a similar TOC removal of 68 % was found as maximal in chloride and sulfate media using the sequential EC-EF process. The EC-treated solutions were also treated by photoelectro-Fenton (PEF) employing a photoreactor with a 125 W UVA lamp. The sequential EC-PEF process yielded a much higher TOC reduction, close to 90 % and 97 % in chloride and sulfate media, respectively, due to the rapid photolysis of the final Fe(III)-carboxylate complexes. The formation of recalcitrant chloroderivatives from generated active chlorine limited the mineralization in the chloride matrix. For practical applications of this two-step technology, the high energy consumption of the UVA lamp in PEF could be reduced by using free sunlight.

Intensification of diclofenac removal through supported liquid membrane and ozonation

Pharmaceutical contaminants are frequently encountered at trace concentrations in various environmental ecosystems. This study introduces a significant approach to water treatment and environmental remediation by combining liquid membrane and ozonation. Initially, diclofenac is transported across the supported liquid membrane using a neutral organic extractant Cyanex 923. The highest removal efficiency was achieved with a 40 % concentration of Cyanex923 dissolved in kerosene, resulting in a permeability of 10.2 cm/h. Additionally, diclofenac is extracted from different environmental matrices such as tap water and real effluent of wastewater, and the effect of ions species was studied. The post-ozonation in the stripping phase resulted in removal of pharmaceuticals and 72 % reduction of total organic carbon at pH = 10 and 45.3 g/Nm3 initial ozone concentration. The study also investigates the identification and tracking of the most prevalent by-product of diclofenac over time.

Degradation of Ampicillin with antibiotic activity removal using persulfate and submersible UVC LED: Kinetics, mechanism, electrical energy and cost analysis

Effective water treatment to remove antibiotics and its activity from contaminated water is urgently needed to prevent antibiotic-resistant bacteria (ARB) emergence. In this study, we investigated degradation of Ampicillin (AMP), an extensively used β-lactam antibiotic, using submersible Ultraviolet C Light Emitting Diode (λmax = 276 nm) irradiation source, and Persulfate (UVC LED/PS system). Pseudo first order rate constant (kobs) for degradation of AMP (1 ppm) by UVC LED/PS system was determined to be 0.5133 min−1 (PS = 0.2 mM). kobs value at pH 2.5 (0.7259 min−1) was found to be higher than pH 6.5 (0.5133 min−1) and pH 12 (0.1745 min−1). kobs value for degradation of AMP in deionized water spiked with inorganic anions (Cl−=0.5369 min−1,SO42−=0.4545 min−1, NO3−=0.1526 min−1, HCO3−=0.0226 min−1), in real tap water (0.1182 min−1) and simulated ground water (0.0372 min−1) were presented. Radical scavenging experiment reveal involvement of sulfate radical anion and hydroxyl radical in UVC LED/PS system. EPR analysis confirms the generation of sulfate radical anion and hydroxyl radical. Importantly, 74% reduction of total organic carbon (TOC) occurred within 60 min of AMP treatment by UVC LED/PS system. Seven degradation by-products were identified by high resolution mass spectrometry, and degradation pathways were proposed. Antibacterial activity of AMP towards Bacillus subtilis and Staphylococcus aureus was completely removed after UVC LED/PS treatment. ECOSAR model predicted no very toxic degradation by-products generation by UVC LED/PS system. Electrical Energy per order (EEo) and cost of UVC LED/PS system were determined to be 0.9351 kW/m3/order and ₹ 7.91/m3 ($ 0.095/m3 or € 0.087/m3), respectively. Overall, this study highlights, UVC LED/PS system as energy efficient, low-cost, and its potential to emerge as sulfate radical anion based advanced oxidation process (AOP) to treat water with antibiotics.

Advancing produced water treatment: Scaling up EC-MF-MDC technology from lab to pilot scale

Membrane distillation integrated with crystallization (MDC) holds promise for sustainable produced water treatment. Addressing challenges like fouling and wetting, common due to high inorganic content and oil-grease presence, requires efficient pretreatment for stable performance. To establish a compact, manageable treatment solution, we examined a pilot-scale integrated electro-coagulation (EC) - microfiltration (MF) system as pretreatment. This step produced 3600 L daily, significantly improving water quality. A remarkable 40% reduction in total organic carbon, 22-fold decrease in total suspended solids, and 600-fold decrease in turbidity underscore its effectiveness. This enhances the suitability for subsequent membrane distillation. In addition, a significant decrease in fouling and scale formation was observed. Long-term batch and continuous MD tests investigated crystallization between MD cycles that prevents significant flux decline. Implementing continuous MDC increased total water recovery six-fold, with stable membrane performance over six cycles, recovering approximately 10% of feed per cycle. These observations highlight the scalable potential of the less-explored integrated treatment (EC-MF-MDC) for effective produced water treatment. This study suggests the viability of the integrated approach for sustainable, larger-scale produced water treatment.

Preparation of Co-C/N flower-like single-atom catalysts via TCPP coordination confinement for enhanced activation of peroxymonosulfate

The design and preparation of highly efficient advanced oxidation processes (AOPs) catalysts is a crucial research area in the field of water pollution control. Herein, a single-atom AOP catalyst Co-N/C material (TPM-650) has been synthesized through the pyrolysis of the flower-shaped Co-TCPP MOF precursor, which is designed based on coordination confinement with TCPP. HAADF-STEM image analysis confirms the uniform distribution of single Co atoms throughout the TPM-650 material, which served as the highly efficient catalytic centers and can achieve 99.99% catalytic degradation of MG dyes in 24 min with only trace dosage ([TPM-650] = 1 mg/L, pseudo-first-order kinetic model, Kobs=0.302 min−1) and low leaching of Co ions (0.348 μg/L). Under optimal condition, the degradation of MG exhibits a high turnover number (dTON) of 68.5 mmol h−1 gcat−1 and a significant reduction in total organic carbon (TOC) by 58.7%. Radical quenching experiments and EPR measurements demonstrated that various reactive oxygen species (•SO4−, •OH, 1O2, MIV(O)/MV(O)) contributes to accelerating MG degradation. The enhanced efficiency and stability were attributed to the ultrathin layer supported single-atom Co-N/C structure, high mesopore volume, and synergy between the catalyst and peroxymonsulfate (PMS) with a synergy index of 16.5. This study not only reports a highly efficient and stable advanced oxidation catalyst Co-N/C, but also confirms that the nitrogen-coordinated Co sites are the primary active sites responsible for PMS activation; thus providing valuable insights into designing efficient transition metal-based AOP catalyst via coordination method for environmental remediation.

Continuous Treatment of Refractory Wastewater from Research and Teaching Laboratories via Supercritical Water Oxidation–Experimental Results and Modeling

Teaching and research laboratories generate wastes of various compositions and volumes, ranging from diluted aqueous solutions to concentrated ones, which, due to milder self-regulation waste-management policies, are carelessly discarded, with little attention given to the consequences for the environment and human health. In this sense, the current study proposes the application of the supercritical water oxidation (SCWO) process for the treatment of complex refractory wastewater generated in research and teaching laboratories of universities. The SCWO, which uses water in conditions above its critical point (T &gt; 647.1 K, p &gt; 22.1 MPa), is regarded as an environmentally neutral process, uniquely adequate for the degradation of highly toxic and bio-refractory organic compounds. Initially, the wastewater samples were characterized via headspace gas chromatography coupled with mass spectrometry. Then, using a continuous tubular reactor, the selected operational parameters were optimized by a Taguchi L9 experimental design, aiming to maximize the total organic carbon reduction. Under optimized conditions—that is, temperature of 823.15 K, feed flow rate of 10 mL min−1, oxidizing ratio of 1.5 (50% excess over the oxygen stoichiometric ratio), and sample concentration of 30%—TOC, COD, and BOD reductions of 99.9%. 91.5% and 99.2% were achieved, respectively. During the treatment process, only CO2, methane, and hydrogen were identified in the gaseous phase. Furthermore, the developed methodology was applied for the treatment of wastewater samples generated in another research laboratory and a TOC reduction of 99.5% was achieved, reinforcing the process’s robustness. A thermodynamic analysis of SCWO treatment of laboratory wastewater under isothermal conditions was performed, using the Gibbs energy minimization methodology with the aid of the GAMS® 23.9.5. (General Algebraic Modeling System) software and the CONOPT 4 solver. Therefore, the results showed that SCWO could be efficiently applied for the treatment of wastewater generated by different teaching and research laboratories without the production of harmful gases and the addition of hazardous chemicals.

Microbial-earthworm ecofilters (MEES) for urban wastewater treatment

Water is an absolute necessity for life and water scarcity is a major problem all over the world. Reusing household wastewater for non-potable water applications is one of the solutions to tackle this problem. Many developing countries lack the technological resources to construct and operate costly wastewater treatment plants. They need cost-effective wastewater treatment options so that both economic aspects and human needs can be met easily. Centralized sewage treatment systems are unable to achieve future demands for sustainable wastewater management in developing countries due to the growing population and needs. The present work examines the effectiveness of treating urban wastewater with microbial-earthworm eco filters (MEEs) (reactor 2) and the filter unit without earthworms (reactor 1). Results of the use of the vermi-biofiltration wastewater treatment unit comprising the biological filtration treatment unit, Eisenia fetida earthworm species, live soil organisms, and natural stones to treat household wastewater are reported herein. The biological oxygen demand (BOD), total dissolved solids (TDS), chemical oxygen demand (COD), and total organic carbon (TOC) were monitored for seven weeks. These parameters exhibited a decreasing trend in both the filtration units. A 75 % reduction in TOC for reactor 2 shows the effectiveness of the proposed system for the utilization of wastewater from urban households. Reactor 2 also showed a reduction in BOD, COD, and TDS approximately in the range of 85, 90, and 30 % respectively. This technique seems to be useful for developing a low-cost and useful household purification system in water-scarce areas using harmless bio-organisms.

Exploring the intensifying effect of periodate/hydroxylamine oxidation process for the effective mineralization of textile dyes effluents with consideration of environmental matrices

AbstractThis study delved into the potential of periodate/hydroxylamine process (PI/HA) as an efficient method for the degradation and mineralization of textile dyes. The PI/HA process generates a range of reactive oxygen species (ROS), which can degrade organic pollutants. The effects of processing conditions, common minerals, organic components, including humic acid and surfactants, and various real environmental matrices, i.e. deionized water, seawater, natural mineral water and treated wastewater effluent, on the PI/HA process efficiency were examined. The results showed that the PI/HA process could remove over 50% of initial dyes concentration in just 10 s, with 80% removal achieved at 10 min using a PI/HA molar ratio of 1 (1.5/1.5 mM). Further adjustments could result in 100% removal in less than 5 min. The process efficiently abated organic matter, with total organic carbon (TOC) reductions exceeding 80% at 60 min and ~90% at 120 min. Radical scavengers showed that •OH played a dominant role (~76%), while 1O2 contributed to a lesser extent (~8.5%). The degradation was more efficient at lower pH, a higher PI to HA molar ratio. The process was unaffected by low concentrations of common mineral anions and surfactants. Higher degradation levels were observed in natural mineral water and seawater.

Nickel–iron-driven heterogenous bio-electro-fenton process for the degradation of methylparaben

Discharge of emerging contaminants such as parabens in natural water bodies is a grievous concern. Among parabens, methylparaben (MP) is most prevalent due to its extensive usage in personal care and food products and has been purported to trigger hormonal-related diseases. In this regard, the bio-electro-Fenton (BEF) process garners attention for remediating refractory compounds because of its ability to generate in situ hydroxyl radicals (•OH) utilising the energy harvested from electroactive microorganisms. In the present investigation, a Ni–Fe-driven heterogenous BEF system (BEF-MFC) was used to degrade MP from different matrices. At neutral catholyte pH, 99.54 ± 0.22% of MP was removed from an initial concentration of 10 mg/L in 240 min of retention time with an estimated treatment cost of about 1.01 $/m3. The removal rate ameliorated when the catholyte pH was dropped to 3.0 and by imposing an external voltage of 0.5 V, requiring just 120 min to achieve comparable MP removal efficiencies. However, catalyst leaching was higher at acidic pH (leaching of Fe ions = 0.44 mg/L and Ni ions = 0.06 mg/L) and applying external voltage increased the treatment cost slightly to 1.08 $/m3. Further, treatment of 10 mg/L MP-spiked real wastewater at pH of 7.0 with the BEF-MFC attained 85.70 ± 3.30% and 56.50 ± 1.70% reduction in MP and total organic carbon, respectively, in 240 min. In addition, a maximum power density of 205.90 ± 2.27 mW/cm2 was harvested in the BEF-MFC; thus, portraying the dual benefit of Ni–Fe heterogeneous catalyst. Even though, Ni–Fe performed reasonably well as Fenton-cum-cathode catalyst, future endeavours should be poised to fine-tune catalysts to accelerate H2O2 and •OH generation, which will reinforce the scalability of this system.