Chemical Oxygen Demand Of Wastewater Research Articles

Experimental study of microwave-catalytic oxidative degradation of COD in livestock farming effluent by copper-loaded activated carbon

ABSTRACT The problem of massive discharge of livestock wastewater is becoming more and more severe, causing irreversible damage to the ecological environment, and how to treat livestock wastewater efficiently and rapidly deserves to be studied in depth. In this work, CuO/granular activated carbon (GAC) loaded catalysts were prepared and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption/desorption techniques, and X-ray energy spectroscopy (EDS). The results showed that CuO was successfully attached to the GAC surface with good adsorption performance. The effects of catalyst dosage, H2O2 dosage, initial pH, microwave power and microwave irradiation time in different reaction systems on the degradation efficiency of chemical oxygen demand (COD) in wastewater were investigated, and the orthogonal experiments were used to explore the importance ranking of these factors. The highest degradation rate of COD was found to be enhanced by 12.1% in the reaction system of CuO/GAC, and the initial pH had the greatest effect on the COD removal rate. The combined MW/catalyst/H2O2 method used in this work provided a rapid and effective degradation of COD in wastewater, which can be helpful for reference in other microwave catalytic oxidation studies.

Alkaline Prehydrolysis Prolongs Resin Life and Enhances the Adsorption of Phenolic Compounds

Phenolic compounds in oil wastewater are highly toxic and refractory. Hydrolysis at pH 12 for 12 h makes these compounds more vulnerable to attack and destruction. Under the binding and precipitation of polyaluminum chloride (PAC) at pH 8, the chemical oxygen demand (COD) was significantly reduced by 38%. The simulation found that hydrolysis + flocculation was a complex multistep process. The COD removal rate was mainly controlled by the prehydrolysis process. The metabolic pathway suggested that the m-cresol produced in the factory was oxidized to low water-soluble aldehyde. Alkaline hydrolysis converted the aldehyde into m-toluene-methanol, which was conducive to being captured by the PAC. Fourier transform infrared spectroscopy (FTIR) showed that the alkaline dehydrogenation of two m-methylphenyl carbinols produced a molecule that was removed by the resin. Generally, the particle size of the residue after alkaline hydrolysis was 6.4–8.3 nm, which was included in the pore size range of the resin. Therefore, the resin adsorption capacity for the hydrolyzed substances increased to 47,000 mg L−1, with 93% renewability. In short, hybrid technology reduces the concentration burden of the resin inflow and controls the molecular size of adsorbed substances for repurification. It strengthens the treatment effect of high COD wastewater and provides innovative ideas for extending the service life of resin.

Effect of lignocellulose/montmorillonite immobilized Bacillus sp. on monosodium glutamate wastewater.

A group of Bacillus sp. was extracted from monosodium glutamate wastewater. Lignocellulose/montmorillonite composite was selected as the carrier. Lignocellulose/montmorillonite composite immobilized Bacillus sp./calcium alginate microspheres were prepared by immobilized microorganism techniques. The microspheres were used to treat monosodium glutamate wastewater with significantly reduced ammonia nitrogen (NH3-N) and chemical oxygen demand (COD) concentrations. The optimum preparation conditions of microspheres in the treatment of NH3-N and COD of monosodium glutamate wastewater were studied. The concentration of sodium alginate was 2.0 wt%, lignocellulose/montmorillonite was 0.06 wt%, Bacillus sp. was 1.0 wt%, CaCl2 solution was 2.0 wt%, coagulation time was 12h, and the removal capacities of NH3-N and COD were 44832 and 78345mg/L, respectively. The surface structure, element content, functional group change, and crystal structure of the microspheres were characterized by SEM, EDS, and other methods. The results showed that the -COOH in lignocellulose/montmorillonite and the -OH in the Bacillus sp. form intermolecular hydrogen bonds. The Si-O and Al-O bonds in lignocellulose/montmorillonite reacted with sodium ions in sodium alginate. New crystal structures appear inside the material after crosslinking, and the microspheres was formed. Thus, the study has shown that the microspheres were successfully prepared and contributes to the treatment of NH3-N and COD in monosodium glutamate wastewater. This work can provide an interesting strategy for the removal of COD and NH3-N in industrial wastewater by reasonably combining bio-physicochemical processes.

Fungal Strain as Biological Tool to Remove Genotoxicity Effect of Phenolic Compounds from Olive Mill Wastewater

This study aims to select fungi isolates to reduce olive mill wastewater (OMWW) chemical oxygen demand (COD) and phenolic compounds (PC), as well as their genotoxicity effect. Treatment with mold, isolated by an innovative technique using phenolic compound-selective media, showed a reduction rate of about 4% for COD and 2% for PC during one month of incubation without optimization of the treatment conditions. Whereas this percentage reached 98% and 96% for COD and PC, respectively, after only 12 days of treatment, when the C:N ratio was adjusted to 30 by adding urea as a nitrogen source at 150 rpm agitation speed. Genetic sequence homology of the most efficient mold isolate showed 100% similarity to Penicillium chrysogenum. High-performance liquid chromatography analysis of phenolic extracts of untreated OMWW showed the presence of five compounds—hydroxytyrosol at 1.22 g.L−1, tyrosol at 0.05 g.L−1, caffeic acid at 0.16 g.L−1, p-coumaric acid at 0.05 g.L−1 and oleuropein at 0.04 g.L−1—that were eliminated during the degradation process at 88.82%. Genotoxicity, assessed by the Vicia-faba root cell, showed a significant decrease in micronucleus frequency of about 96% after fungal treatment. These results confirm the positive role of fungal treatment of OMWW to eliminate genotoxicity and their ability to improve the agronomic potential.

Effect of bio-electrochemical systems on the removal of organic and inorganic membrane fouling from anaerobic membrane bioreactors

To alleviate the fouling of membrane bioreactors, a coupling system was constructed in which a conductive membrane served as the anode of a bio-electrochemical system, whereas ordinary carbon felt served as the cathode. The membrane module showed approximately 90 % performance for wastewater chemical oxygen demand removal. As the external resistance increased from 50 to 1500 Ω, the number of operating days increased from 25 to 62. The respective concentrations of polysaccharide and protein on R-1500 membrane surface were 6.81- and 2.05-fold greater than the concentrations on the R-50 membrane, and the concentration of Ca2+ on the surface of the R-50 membrane was 1.48-fold greater than the concentration on the R-1500 membrane. Therefore, inorganic fouling is the main type of membrane fouling in coupled systems with low external resistance. For coupled systems with higher external resistance, severe organic fouling eventually causes membrane blockage. Variance partitioning analysis showed that the micro-electric field contributed to 95.34 % of the effect on the control of membrane fouling, significantly greater than the 67.19 % contributed by the current. Therefore, in the system where organic and inorganic fouling coexists, appropriate enhanced field strength (increase in external resistance) is particularly important for membrane fouling control.

Industrial indigo dyeing wastewater purification: Effective COD removal with peroxi-AC electrocoagulation system

Direct current (DC) electrocoagulation has obvious decolorization effect on indigo dyeing wastewater produced in actual production, while the removal rate of chemical oxygen demand (COD) was less than 40%, accompanied by serious electrode corrosion and high energy consumption. In order to enhance the COD removal rate, reduce the electrode loss and power consumption, a peroxi-alternating current (AC) electrocoagulation (EC) system was constructed. With COD as the main evaluation index, the effects of power type, electrode combination and process parameters on COD removal rate and decolorization rate were focused on and explored, as well as revealing the degradation mechanism of COD. The results showed that AC electrocoagulation enhanced the floc adsorption capacity by improving the floc structure, and the COD removal rate after treatment was 51.19%. The coupled system of peroxi-AC electrocoagulation further removed sulfite and residual dyes in the wastewater, and the COD removal and decolorization rate of the treated wastewater reached 78.09% and 98.47%, respectively. In addition, the specific energy consumption analysis of COD removal showed that the coupled system was far less energetic than the DC electrocoagulation process, with only 30% of its energy consumption. The uniform corrosion of the electrode under the action of AC weakened the passivation, which reduced the electrode loss and power consumption by 22.73% and 43.75%, respectively. Results from the present work indicated that the peroxi-AC EC system could be an effective method for reducing the concentration of COD in indigo dyeing wastewater.

Integrated Photocatalytic Oxidation and Adsorption Approach for the Robust Treatment of Refinery Wastewater Using Hybrid TiO2/AC

This study reports the removal of hydrocarbon (HC) pollutants from petroleum refinery wastewater by integrated photocatalytic oxidation and adsorption using a TiO2/AC hybrid material. The hybrid adsorbent/catalyst was prepared by the impregnation of TiO2 over AC and characterized by FTIR, SEM, EDX, and XRD analyses. Under the optimized reaction conditions of pH 3, 30 °C, and 1000 mg TiO2/AC per 500 mL of sample in 50 min, the integrated photocatalytic oxidation-adsorption achieved a net percentage removal of benzene, toluene, aniline, and naphthalene of 91% from model HC solutions. Under these conditions, for the treatment of real refinery wastewater, TiO2/AC caused a 95% decrease in chemical oxygen demand (COD). The integrated photocatalytic oxidation and adsorption using TiO2/AC showed a clear advantage over the individual adsorption and photocatalytic oxidation using AC and TiO2, whereby about the same level of removal of model HCs and a decrease in the COD of refinery wastewater was attained in 105 min and 90 min, respectively, utilizing larger adsorbent/catalyst dosages. GC-MS analysis revealed that during the integrated process of adsorption-photocatalytic oxidation, all the parent HCs and oxidation byproducts were completely removed from the refinery wastewater. Based on the outstanding performance, cost-effectiveness, and environmental greenness, the newly designed TiO2/AC via the integrated adsorption-photocatalytic oxidation can be counted as an effective alternative route for the large-scale processing of refinery wastewater.

Phytoremediation: A Novel Review on the Efficacy of Aquatic Plants in the Wastewater Treatment

Wastewater causes significant environmental harm. Researchers have created a variety of approaches to address this issue. In this study, phytoremediation technology was used to remove pollutants from wastewater so that it could be used for other purposes. This technology is one of the most promising because it is inexpensive, ecologically benign, and effective at removing pollutants. Using a methodical mapping approach, the aquatic plant is treated for domestic, commercial, and municipal wastewater as part of the phytoremediation process. Additionally, a comparative descriptive approach was used for the studied variables in the exclusions where it has been found that Eichhornia Crassipes is an aquatic weed that detached NO2- and NO3- up to 93% of industrial wastewater, High CNP-content wastewater was treated using canna lilies. The removal of BOD3 (biological oxygen demand) and COD (chemical oxygen demand) ranged from 69.8 to 96.4% and 63.6 to 99.1%, respectively. In 21 days, Azolla filiculoides eliminated from municipal wastewater BOD (63%), PO43 (84%), SO42- (83%), Cl (76%), NO3- (76%), COD (79%), and EC (49%).

Compact fluidic electrochemical sensor platform for on-line monitoring of chemical oxygen demand in urban wastewater

• Carbon-silica (C/SiO 2 ) thin films produced by sol–gel chemistry. • C/SiO 2 electrode fabrication at wafer-scale by photolithography / etching process. • Excellent electrochemical performance shown by the fabricated electrodes. • Electrochemical sensor integrated in a modular fluidic system for in-field use. • Cu NPs-modified C/SiO 2 sensor used for on-line analysis of COD in urban wastewater. The rapid expansion of urban areas has given rise to the generation of large amounts of wastewater that pose a growing pressure on the surrounding ecosystems. Effective water quality surveillance programs demand the implementation of in-field tests to monitor water safe discharge in the environment after being adequately treated. This paper describes the manufacturing and application of a miniaturized electrochemical sensor for measuring dissolved chemical oxygen demand (COD) in surface waters entering and exiting urban wastewater treatment plants (UWWTP). Thin-film carbon electrodes are produced on Si/SiO 2 substrates by a combined sol–gel material synthesis and photolithography/dry etching process at the wafer level and show superior electrochemical performance compared with the glassy carbon standard electrode. Three-electrode electrochemical cells of planar configuration are produced and the COD sensor is manufactured by electrodepositing copper nanoparticles (Cu NPs) on the working electrode under controlled potentiostatic conditions. A simple fluidic electrochemical sensor device is fabricated and allows for the Cu NPs electrodeposition as well as analytical sensor performance in an automatic fashion. A linear range up to 670 mg·L -1 O 2 and a limit of detection of 30 mg·L -1 O 2 are achieved. The ability of this electrochemical sensor approach to monitoring the soluble organic load of urban wastewater in real-time is evaluated by analyzing three samples collected in different locations of an UWWTP. The COD values estimated with the sensor are in excellent agreement with those obtained using the standard dichromate method provided by an accredited laboratory. This analytical platform provides a robust, user-friendly low-maintenance flow sensor approach for deployed analysis of COD that could aid to control the effectiveness of water treatment processes, especially when facing water influents containing organic overloads due to changing weather conditions or any anthropogenic phenomena.

Sequential coagulation/flocculation and sonolytic oxidation using persulfate and hydrogen peroxide for real rubber processing industry wastewater treatment: Kinetic modelling and treatment cost analysis

Rubber processing industry consumes huge quantity of water, uses chemicals and produces enormous quantity of toxic wastewater with high level of chemical oxygen demand (COD), solids and turbidity. In this study, treatability of rubber processing industry effluent using a sequential coagulation-flocculation (CF) followed by sonolytic oxidation was studied with the real wastewater collected from a rubber processing industry located near to Agartala, Tripura, the second largest rubber producing state in India. Initially aluminium sulfate was used as coagulant in the CF process to reduce the COD of the wastewater followed by only ultrasonication (CF + US), sonolytic oxidation using persulfate (CF + US + PS), sonolytic oxidation using hydrogen peroxide (CF + US + H2O2) and sonolytic oxidation using both persulfate and hydrogen peroxide (CF + US + PS + H2O2) as oxidants. Real rubber processing wastewater was also treated with only sonication (US). Firstly, the only CF process (aluminium sulphate dose: 500 mg/L) could reduce the COD of wastewater from 18267 mg/L to 12800 mg/L (COD removal: 29.93 %). Thereafter, CF + US (sonication time: 30 min), CF + US + PS (PS dose: 500 mg/L), CF + US + H2O2 (H2O2 dose: 0.75 mmol/L), and CF + US + PS + H2O2 (PS dose: 500 mg/L and H2O2 dose: 0.75 mmol/L) resulted to effluent COD value to ∼ 6800 mg/L, 4200 mg/L, 3200 mg/L and ∼ 1600 mg/L, respectively. The CF + US + PS + H2O2 process was the best option among the considered combination of treatment techniques to treat the real rubber processing industry effluent in terms of COD removal (%). Kinetic analysis for the degradation of COD in various treatment processes were found to be consistent with pseudo second order kinetic model. The treatment cost analysis revealed that COD degradation by CF + US + H2O2 process cost ∼ 2.5 USD/kg of COD removal with 82.48 % of COD removal.

Removal of Nutrients and COD in Wastewater from Vietnamese Piggery Farm by the Culture of Chlorella vulgaris in a Pilot-Scaled Membrane Photobioreactor

The treatment of nutrients and organic contaminants in wastewater using microalgae has drawn significant interest thanks to its advantages of environmental friendliness, low cost, CO2 emission reduction, and recycling of valuable biomass. Among other algae species, Chlorella sp. showed good vitality, simplicity in cultivation, and high nutrient accumulation in harsh conditions of wastewater. In this study, Chlorella vulgaris was inoculated in a membrane photobioreactor (MPBR) with piggery digestate to investigate the C. vulgaris growth rate and the removal efficiency of nutrients and chemical oxygen demand (COD). The results indicated that the cultivation of C. vulgaris in an MPBR system exhibited continuous and simultaneous removal of NH4+, PO43−, and COD from two-fold diluted piggery wastewater. Both the algae growth rate and nutrient removal depended on the liquid hydraulic retention time in the MPBR. The highest removal efficiency of NH4+ (74.55%), PO43− (70.20%), and COD (65.85%) was obtained in the longest HRT of 5 days with the highest microalgae biomass concentration of around 1.1 g/L. The algae washout phenomenon was negligible in the continuous cultivation in the MPBR system. Compared to the cultivation in batch mode, the MPBR could achieve a similar algae growth rate and treatment efficiency with a much shorter hydraulic retention time.

Optimisation of chemical oxygen demand removal from animal house wastewater using central composite design

In the developing world, most animal farmhouses dispose of their wastewater without treatment and that creates conditions for the spread of diseases. To discourage this practice, there is the need to provide relatively simpler wastewater treatment options. Thus, this research work sought to optimise the chemical oxygen demand (COD) removal efficiency of a simple anaerobic digester by determining the optimum concentrations of rhamnolipid biosurfactant and potassium phosphate buffer needed to make the anaerobic digester remove COD efficiently. The central composite design was used for the optimization study. In the one factor at a time experiment, increasing the concentration of the potassium phosphate buffer from 1.07 g/l K2HPO4 + 0.53 g/l KH2PO4 to 1.37 g/l K2HPO4 + 0.83 g/l KH2PO4 increased the COD removal efficiency of the anaerobic digester from 19.3 to 24.7%. Also, increasing the concentration of rhamnolipid from 80 to 320 mg/l increased the efficiency of the digester from 24.2 to 26%. The percentage COD removal was highly improved (> 85%) in the optimisation study when both rhamnolipid and buffer were combined at high levels (+ 1). The model built from the central composite design reflected a good fit of the data obtained with R2 of 82.5% and a p value of 0.000. This study therefore demonstrated that a simple anaerobic digester can be used to remove COD in wastewater by optimising the concentrations of rhamnolipid and potassium phosphate buffers in the treatment system.

Degradation of COD in antibiotic wastewater by a combination process of electrochemistry, hydroxyl-functionalized ball-milled zero-valent iron/Fe3O4 and Oxone

ABSTRACT In this study, the significant iron-based material, hydroxyl-functionalized ball-milled zero-valent iron/Fe3O4 (HFB-ZVI/Fe3O4) was employed for the experiments. The performance of the Electro + HFB-ZVI/Fe3O4 + Oxone system for the degradation of chemical oxygen demand (COD) in antibiotic wastewater was investigated. A direct current was applied between a graphite plate anode and two iron plate cathodes, and a series of operational parameters, such as applied electric current, the dosage of HFB-ZVI/Fe3O4 composite, the dosage of Oxone, and initial solution pH, were explored to evaluate the oxidation process. The application of electric current enhanced the gradual degradation of COD and the increase of current intensity accelerated COD degradation. The neutral condition was favourable for the rapid degradation of COD in a short reaction time by the Electro + HFB-ZVI/Fe3O4 + Oxone process and promoted the degradation efficiency of COD. An increase of electric current gradually decreased the reaction solution pH, the larger the electric current applied in the reaction process, the lower the final pH of the reaction solution. Under the optimal experimental conditions (1 g/L HFB-ZVI/Fe3O4 composite, 0.3 g/L Oxone, current intensity = 500 mA, initial solution pH = 7.85), Electro + HFB-ZVI/Fe3O4 + Oxone achieved 99% COD degradation in antibiotic wastewater. Radicals quenching experiments indicated the contribution to COD degradation by hydroxyl radicals (HO•), sulphate radicals (SO4 •–) and other oxidants were 66.03%, 24.014% and 9.756%, respectively. The possible mechanism of COD degradation in the Electro + HFB-ZVI/Fe3O4 + Oxone system was also discussed in this study. The findings in this work provided useful information for the treatment of wastewater.

Recovery of Acid and Alkaline from Industrial Saline Wastewater by Bipolar Membrane Electrodialysis under High-Chemical Oxygen Demand Concentration

Actual high saline wastewater containing concentrated organics and sodium chloride is a bioenergy and renewable resource. This study compared two different bipolar membrane electrodialysis membranes from two companies' stacks to recover HCl and NaOH from sodium chloride solution and actual chemical wastewater. The results demonstrated that the electrolysis rates were around 1.5 kg/m2h, the HCl and NaOH production rates were about 0.9 kg/m2h, energy consumption was in the range of 1.05-1.27 kWh/kg, and the economic benefits were above 1 yuan/h in BMED systems. From analyzing the performance of seven different BMED membrane stacks, the B2 stack was chosen for electrolyzing actual high salt wastewater to observe the effect of chemical oxygen demand on BMED systems, where electrolytic salt performance, HCl-NaOH alkali production rates, and energy consumption show linear dependence on time for 5000 mg/L chemical oxygen demand wastewater. It illustrated chemical oxygen demand can enhance energy consumption and reduce electrolytic salt performance and the acid and alkali production rates, due to improving the membrane area resistance. In this study, the effect of high COD saline wastewater on the performance of a BMED membrane stack was clarified and the mechanism was analyzed for its practical application in treating chemical high salt wastewater.

Reduction of COD and TOC concentration in pharmaceutical wastewater using Fe2+ catalyzed ozone: Full-scale case study

This work was carried out to improve the performance of an ozonation system used for wastewater treatment in a pharmaceutical industry. In order to improve the mineralization of organic matter, ferrous sulfate was applied as a catalyst to the reaction system. After this, the pH of the water was adjusted to 8.5–10, so that the process is carried out under alkaline conditions. Finally, O3 was injected through a Venturi tube in order to improve the mass exchange between gas and water. Preliminary operating data indicate that the treatment system achieves chemical oxygen demand (COD) removals of less than 10%. The tests were conducted at full scale and the water quality variables were analyzed at different reaction times. It was determined that for an ozone dose equal to 10 g/h and 10 mg/L Fe2+ and an initial water pH equal to 9, 4.5 hours were required to achieve a reduction of 30.73% COD and 36.85% total organic carbon (TOC). The results obtained with an initial pH higher than 9.5 indicate that the effectiveness of the process is reduced, a fact that may be caused by the rapid formation of insoluble Fe(OH)3, which decreases the availability of the catalyst for the formation of OH* radicals in the water.

Developing an Efficient Processing System Treatment for the High Concentration of Eucalyptus Chemical Mechanical Pulp Wastewater.

The current wastewater treatment method shows low efficiency in treating wastewater with high concentrations of chemical mechanical pulp (CMP). Therefore, a chlorine dioxide Pretreatment Anaerobic Treatment (DPAT) was developed and applied to treat the CMP wastewater to obtain higher efficiency, obtaining the following results: The biodegradability of CMP wastewater improved after chlorine dioxide pretreatment. The COD of wastewater treated with chlorine dioxide was reduced from 5634 mg/L to 660 mg/L. The removal rate for chemical oxygen demand (COD) was 88.29%, 29.13% higher than the common anaerobic treatment. The reasons for the high efficiency of the DPAT treatment were that chlorine dioxide pretreatment removed the toxic substances in the original wastewater and thereby promoted the proliferation and growth of the anaerobe. The results show that pretreatment with chlorine dioxide can effectively enhance the biodegradability of high-concentration CMP wastewater. Therefore, DPAT treatment of high-concentration CMP wastewater is beneficial to environmental protection.

Study of BOD, COD and TSS Removal in Batik Industry Wastewater using Electrocoagulation Method

<p>Central Java, especially Pekalongan, is one of the largest batik centres with a high amount of batik waste and has the potential to pollute the environment. Wastewater treatment using the electrocoagulation method as an alternative to environmental pollution prevention in Pekalongan Regency. This study determined the effect of stress and resistance time on decreasing COD, BOD and TSS levels in batik wastewater. The analysis performed on the samples included BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), TSS (total suspended solids), and pH. Voltage variations of 12, 24, and 30 volts and holding times of 90, 120, 150, and 180 minutes were applied. A pair of aluminium metals (Al-Al) was used with a thickness of 0.1 cm, an area of 12x14 cm, and a volume of 2500 ml. The results showed that the voltage and contact time decreased the amount of COD, BOD and TSS. In addition, the results showed that the electrocoagulation method at a voltage of 30 volts and a contact time of 180 minutes could reduce COD levels by 75.78%, TSS levels by 93.9%, and BOD levels by 83.75%.</p>

Photovoltaic-driven electrochemical remediation of drilling fluid wastewater with simultaneous hydrogen production.

In this work, we studied the application of photovoltaic solar energy for driving the electrochemical processes of electrocoagulation and electrooxidation to remediate drilling fluid wastewater, and simultaneously harvest energy in the form of electrolytic hydrogen gas produced at the cathode. The electrocoagulation was performed with sacrificial aluminium electrodes and electrooxidation with dimensionally stable boron-doped diamond electrodes in batch-wise and continuously operated mode, and their efficiency in both pollutants removal and hydrogen gas production was elucidated. The parameters affecting the efficiency of the applied electrochemical processes, such as applied current density, pH, electroprocessing time and flow rate, were investigated. The electrochemical processing was monitored by measuring the chemical oxygen demand (COD) of treated wastewater. The electrocoagulation treatment conducted with current densities of 30, 60 and 90 mA/cm2 reduced the wastewater COD by about 67%, whereas the electrooxidation treatment at the same conditions yielded a COD removal of over 95%. The amount of produced hydrogen was 171 L/g COD removed from treated wastewater.

Catalytic ozonation of aqueous 4-methylquinoline by fluorinated ceramic honeycomb

Metal-free catalysts for catalytic ozonation have attracted more and more attentions to eliminate the risk of secondary pollution of heavy metals in water or wastewater treatment. Herein we prepared fluorinated ceramic honeycomb (FCH) with the dip-calcination method using NH4F as the modifier over ceramic honeycomb (CH) to catalyze the ozonation of 4-methylquinoline (4-Meq), a typical harmful quinoline derivate discharged from coal or petroleum industries. The ozonation degraded 54.9% of 4-Meq and removed 14.4% of chemical oxygen demand (COD) in 30 min, while the FCH catalytic ozonation degraded 77.8% of 4-Meq and removed 29.2% of COD. In addition, FCH has a stable catalytic performance and can effectively remove 4-Meq as well as COD in real coal gasification wastewater. The fluorination endows the surface of the FCH with abundant Si–F groups as active acid sites and aluminum-attached hydroxyl groups, and then enhance the ozone decomposition to generate free reactive oxygen species (ROS). Those ROS includes free hydroxyl radicals, free superoxide radicals as well as singlet oxygen, and the free hydroxyl radical plays a major role in the degradation and COD removal of 4-Meq. The degradation of 4-Meq follows two pathways of the demethylation, benzene ring opening and the pyridine ring-opening. This work demonstrates an efficient catalyst for ozonation to root out the risk of the heavy metals pollution from catalysts, and provides an insightful understanding of the FCH catalytic ozonation.

Impact of continuous electrochemical degradation of eucalyptus alkaline peroxide mechanical pulping wastewater

Levels of pollutants in pulp and papermaking wastewater are an important issue for environmental protection. High concentrations of contaminants can seriously affect the environment if they are not processed. Therefore, treating paper wastewater is a necessary option for governments to select appropriate treatment methods to remove the multi-component pollutants. In this study, the impact of continuous electro-degradation of eucalyptus alkaline peroxide mechanical pulping wastewater was studied. An electrolytic treatment method performed at a low voltage was used. Through the electrolysis method, the wastewater chemical oxygen demand was decreased by 98%, and color-generating groups were nearly all destroyed. During the electrolysis process, the pH value of wastewater continuously decreased and finally reached 2.5. Lowering the pH of the waste solution will help increase the electrolysis efficiency of the wastewater. A total of 5.8 g of alkali was obtained. The wastewater precipitation before and after electrolysis was analyzed by X-ray photoelectron, Fourier transform infrared, and energy-dispersive X-ray spectroscopies.