Maximum Chemical Oxygen Demand Reduction Research Articles

Removal of pharmaceuticals from wastewater by electrochemical oxidation using cylindrical flow reactor and optimization of treatment conditions

This paper examines the use of electrooxidation for treatment of wastewater obtained from a pharmaceutical industry. The wastewater primarily contained Gentamicin and Dexamethasone. With NaCl as supporting electrolyte, the effluent was treated in a cylindrical flow reactor in continuous (single pass) mode under various current densities (2–5 A/dm2) and flow rates (10–40 L/h). By cyclic voltammetric (CV) analysis, the optimum condition for maximum redox reaction was determined. The efficiency of chemical oxygen demand (COD) reduction and power consumption were studied for different operating conditions. From the results it was observed that maximum COD reduction of about 85.56% was obtained at a flow rate of 10 L/h with an applied current density of 4 A/dm2. FT-IR spectra studies showed that during electrooxidation, the intensities of characteristic functional groups such as N-H, O-H were reduced and some new peaks also started to appear. Probable theory, reaction mechanism and modeling were proposed for the oxidation of pharmaceutical effluent. The experimental results demonstrated that electrooxidation treatment was very effective and capable of elevating the quality of treated wastewater to the reuse standard prescribed for pharmaceutical industries.

Treatment of bio-digester effluent by electrocoagulation using iron electrodes

The present paper deals with chemical oxygen demand (COD) reduction of a bio-digester effluent (BDE) in a batch electrocoagulation (EC) reactor using iron electrode. A central composite (CC) experimental design has been employed to evaluate the individual and interactive effects of four independent parameters on the COD removal efficiency. The parameters studied are current density ( j): 44.65–223.25 A/m 2; initial pH (pH 0): 2–8; inter-electrode distance ( g): 1–3 cm and electrolysis time ( t): 30–150 min. The results have been analyzed using Pareto analysis of variance (ANOVA). Analysis showed a high coefficient of determination value ( R 2 = 0.8547) and satisfactory prediction for second-order regression model. Graphical response surface and contour plots have been used to locate the optimum values of studied parameters. Maximum COD and color reduction of 50.5% and 95.2%, respectively, was observed at optimum conditions. Present study shows that EC technique can be employed in distilleries to reduce the pollution load before treatment in aerobic treatment plants to meet the discharge standards.

Electrochemical oxidation for the treatment of textile industry wastewater

This study elucidates the reduction of organics from textile effluents through electrochemical oxidation technique. Effect of pH and current intensity were investigated in this system. It was found that degradation was maximum at the current intensity of 0.6A and at a pH of 1.3. Under the same experimental conditions the removal of chemical oxygen demand (COD), total solids, total dissolved solids and total organic carbon were found to be approximately 68%, 49.2%, 50.7% and 96.8%, respectively. Effect of current intensity on color removal was also investigated as a function of electrolysis time (30–210minutes) and it showed that maximum removal efficiency (96%) was reached within 60minutes at 0.6A. While studying the effect of pH on COD removal, it was observed that a decrease in pH to an optimum of 1.3 showed maximum COD reduction of 68%. These results suggest an important role of these parameters in electrochemical process for removing organic pollutants.

Anaerobic Biogas Generation from Sugar Industry Wastewaters in Three-Phase Fluidized-Bed Bioreactor

The studies are undertaken to develop an effective anaerobic continuous digestion process for biogas generation from sugar industry wastewaters using actively digested sludge from a sewage plant, in three-phase fluidized bed bioreactor. Attempts are made to optimize hydraulic retention time (HRT), initial feed pH, feed temperature and flow rate of feed (organic loading rate) for maximum production of methane gas and maximum removal of chemical oxygen demand (COD) and biological oxygen demand (BOD) of sugar industry wastewaters. The optimum conditions for the system are: digestion time, 8 h; initial pH of feed, 7.5; feed temperature, 40oC; feed flow rate, 14 L/ min with maximum organic loading rate (OLR), 39.513 kg COD m �3 h �1 . The organic loading rates (OLR) are calculated on the basis of COD inlet in the bioreactor at different flow rates. The maximum expansion of the bed is observed as 23.67 m at optimum feed flow rate of 14 L/ min. The maximum methane gas concentration is 63.56% ( v/v ) of the total biogas generation at optimum process parameters. The maximum biogas yield rate is 0.835 m 3 /kg COD m �3 h �1 with maximum methane gas yield rate of 0.530 m 3 /kg COD m �3 h �1 (63.56% v/v ) at optimum process parameters. The values for maximum reduction of COD and BOD are 76.82% ( w/w ) and 81.65% ( w/w ) with maximum OLR of 39.513 kg COD m �3 h �1 at optimum conditions.

COD and BOD reduction from coffee processing wastewater using Avacado peel carbon

The aim of this study was the assessment of reduction of chemical oxygen demand (COD) and biological oxygen demand (BOD) of wastewater from coffee processing plant using activated carbon made up of Avacado Peels. The complete study was done in batch mode to investigate the effect of operating parameters. The results of the COD and BOD concentration reduction with avocado peel carbon (APC) and commercial activated carbon (CAC) were compared and optimum operating conditions were determined for maximum reduction. Adsorption isotherm was also studied besides the calculation of optimum treatment parameters for maximum reduction of COD and BOD concentration from effluent of the coffee processing plant. The maximum percentage reduction of COD and BOD concentration under optimum operating conditions using APC was 98.20% and 99.18% respectively and with CAC this reduction was 99.02% and 99.35% respectively. As the adsorption capacity of APC is comparable with that of CAC for reduction of COD and BOD concentration, it could be a lucrative technique for treatment of domestic wastewater generated in decentralized sectors.

Photocatalytic and electrochemical combined treatment of textile wash water

Various chemical and physical processes for treatment of textile effluent are not destructive but they only transfer the contaminants from one form to another. The presence of high concentration of organic dye and total dissolved solids (TDS) in the effluent that are not removed by biological treatment must be eliminated by an alternative method to the conventional ones is the advanced oxidation process (AOP). A procion blue dye effluent was treated by photo and electrochemical oxidation process as well as by combining photocatalytic degradation using TiO 2 suspensions. Chemical oxygen demand (COD) and colour removal can be used to follow the degradation of the organic pollutant. The effects of pH, current density, flow rate of effluent that passes into the reactor and supporting electrolyte were studied. Comparative studies were carried out on photocatalytic and electrochemical process to degrade the procion blue. The maximum COD reduction and colour removal were 96 and 100%, respectively. Photodegradation efficiency of dye was high when photolysis was carried out in the presence of 40 mg/l of TiO 2.

Electrochemical treatment of Procion Black 5B using cylindrical flow reactor—A pilot plant study

The paper presents the results of an efficient electrochemical treatment of Procion Black 5B—a pilot plant study. Experiments were conducted at different current densities and selected electrolyte medium using Ti/RuO 2 as anode, stainless-steel as cathode in a cylindrical flow reactor. By cyclic voltammetric analysis, the best condition for maximum redox reaction rate was found to be in NaCl medium. During the various stages of electrolysis, parameters such as COD, colour, FTIR, UV–vis spectra studies, energy consumption and mass transfer coefficient were computed and presented. The experimental results showed that the electrochemical oxidation process could effectively remove colour and the chemical oxygen demand (COD) from the synthetic dye effluent. The maximum COD reduction and colour removal efficiencies were 74.05% and 100%, respectively. Probable theory, reaction mechanism and modeling were proposed for the oxidation of dye effluent. The results obtained reveal the feasibilities of application of electrochemical treatment for the degradation of Procion Black 5B.

Chemical Oxygen Demand (COD) Reduction in Domestic Wastewater by Fly Ash and Brick Kiln Ash

The potential of fly ash, brick kiln ash and commercial activated carbon is determined for the reduction of chemical oxygen demand (COD) from domestic wastewater. Laboratory experiments are conducted for investigating the effect of treatment time, adsorbent dose, pH of the media, initial COD concentration, agitation speed and particle size of adsorbents on the COD reduction from the domestic wastewater. Starting with an initial COD concentration of 1080 mg/l the maximum COD reduction achieved for fly ash was 87.84%, brick kiln ash was 83.22% and commercial activated carbon was 99.35 %. These values were achieved when the wastewater was treated with activated carbon for 180 min, fly ash 250 min and brick kiln ash 300 min and the adsorbent dose was kept respectively at 40 g/l, 60 g/l and 45 g/l for activated carbon, fly ash and brick kiln ash. Agitation speed was kept constant at 600 rpm and the pH was maintained at 2 for activated carbon and fly ash and 5 for brick kiln ash. The maximum percent reduction is for 0.053 mm or smaller size of the particles. Though the adsorption capacity of the ash for reducing the COD is lower than that of the commercial activated carbon, the low material cost can make it an attractive option for the treatment of domestic wastewater.

Continuous methanogenesis of black liquor of pulp and paper mills in an anaerobic baffled reactor using an immobilized cell system

AbstractAn anaerobic baffled reactor together with an immobilized cell system has been proposed for methanogenesis of the black liquor from pulp and paper mills in a continuous system. A maximum chemical oxygen demand reduction of 50%, and biogas generation of 10 L d−1, having methane content of 66% (v/v) at an organic loading rate (OLR) of 7 kg m−3 d−1 with hydraulic retention time of 2 days, were recorded. OLR values higher than 7 kg m−3 d−1 were toxic to methanogenesis and destabilized the reactor system. Copyright © 2006 Society of Chemical Industry

Thermochemical Precipitation as a Pretreatment Step for the Chemical Oxygen Demand and Color Removal from Pulp and Paper Mill Effluent

In the present work, the removal of chemical oxygen demand (COD) and color of paper mill wastewater due to the thermochemical precipitation of dissolved solids was studied in the temperature range from 20 to 95 °C using different catalysts/chemicals. The homogeneous CuSO4 catalyst was found to be the most active in comparison to the other heterogeneous catalysts under similar operating conditions. The pH value showed a pronounced effect on the precipitation process. At an optimum initial pH of 5.0, a maximum COD reduction of 63.3% was obtained with a catalyst concentration of 5 kg m-3, although the maximum color removal was 92.5% using a CuSO4 concentration of 2 kg m-3. The residual copper in the supernatant works as a good catalyst for wet air oxidation of the supernatant. Thermogravimetric analysis showed that the thermal oxidation of the solid residue follows an one-way transport diffusion model with first-order irreversible reaction kinetics. The heating value of the precipitate was found to be compar...

Continuous cultivation of the yeast Candida utilis at different dilution rates on pineapple cannery effluent

Candida utilis was grown on a pineapple cannery effluent in a chemostat at dilution rates ranging between 0.05 and 0.65 h−1 to establish optimal conditions for biomass production and chemical oxygen demand (COD) reduction. Sucrose, fructose and glucose were the main sugars in the effluent. Maximum value for cell yield coefficient and productivity were (0.686, gx/gs) and (2.96, gx/l/h) at a dilution rate of 0.425 and 0.475 h−1, respectively, while maximum COD reduction (98%) was attained at a dilution rate of 0.1 h−1. The maintenance coefficient attained a value of (0.093, gs/gx/h). An increase in dilution rate produced a higher protein content of the biomass.

Decolorization and biodegradation of anaerobically digested sugarcane molasses spent wash effluent from biomethanation plants by white-rot fungi

Four white-rot fungal cultures were examined for their ability to decolorize and bioremediate anaerobically digested molasses spent wash (DMSW) generated by biomethanation plants. Two cultures Coriolus versicolor and Phanerochaete chrysosporium showed an ability to decolorize and reduce the chemical oxygen demand (COD) of diluted DMSW (12·5% v/v). Both cultures required an additional labile carbon source to carry out decolorization while additional organic nitrogen did not significantly improve it further. Optimum growth and decolorization occurred at 35–40°C, pH 5·0, glucose at 3–5%(w/v). Maximum decolorization (71·5 and 53·5%) and COD reduction (90·0 and 73·0%) were achieved in 6·25% (v/v) DMSW medium by C. versicolor and P. chrysosporium, respectively. These values decreased significantly at higher concentrations of DMSW (12·5 and 25% v/v), nevertheless both cultures have profound potential applications in reducing the pollution of DMSW effluent prior to its disposal.

Modelling for waste water treatment by Rhodopseudomonas palustris Y6 immobilized on fibre in a columnar bioreactor.

A kinetic model of continuous treatment of waste water by Rhodopseudomonas palustris Y6 immobilized on soft fibre in a columnar bioreaction system was established. Good agreement was found between the model prediction and the experimental data from continuous operation [initial chemical oxygen demand (COD) concentration = 29.700 g/l] of the system. The optimum operational conditions for the maximum COD reduction capacity were investigated from the model prediction and the experimental data. The waste water treatment process may significantly increase the waste reduction capacity because a large amount of active biomass for COD reduction is immobilized in the system, resulting in operation stability. The results presented here provide a useful basis for further scaling up and efficient operation of waste water treatment processes.

Wet air oxidation studies of coal gasification wastewaters

The kinetics of wet oxidation of coal gasification wastewater were studied. Experimental studies explored the effect of temperature and residence time on the extent of reaction by conducting constant volume batch tests in a 1-liter high pressure autoclave. The extent of reaction was determined by measuring the chemical oxygen demand (COD) and phenol concentrations of the wastewater at various times. The effect of temperature was studied from 205 to 251°C with residence times from 30 to 90 minutes. The experimental data obtained were used to fit Arrhenius expressions of the reactions. A mathematical model consisted of two first-order reactions in series showing a maximum COD reduction of 60% and a maximum phenol reduction of 95%, both at 251°C and a 90 minute residence time. The activation energies for COD and phenol reduction were both found to be 8.0 kcall.