Optimum Chemical Oxygen Demand Removal Research Articles

In-ground lagoon anaerobic digester in the treatment of palm oil mill effluent (POME): Effects of process parameters and optimisation analysis

Most researchers analyse and optimise the anaerobic performance based on the data generated from pilot plants and laboratory scaled experiments, but not from the industrial scale biogas plant. Therefore, this study aims to evaluate, compare, and optimise the performances of an In-ground Lagoon Anaerobic Digester under mesophilic conditions in four different biogas plants (BGP A, B, C and D) located in Malaysia, for total chemical oxygen demand (COD) removal and total biogas produced. Organic loading rate (OLR), temperature, recirculation ratio (RR) and plant location are found to have significant effects on COD removal and biogas production. Sensitivity analysis shows that BGP A, B, and C show a similar trend of sensitivity, i.e., OLR > Temperature > RR. Conversely, the temperature has the highest sensitivity contributing to the Chemical Oxygen Demand (COD) removal for plant D. Despite having a similar anaerobic digester design for each biogas plant, the optimum operating parameters of OLR, temperature and recirculation ratio vary from plant to plant. BGP B can achieve the highest COD removal (1.21 X 106 kg CODin/month) as well as biogas production rate (4.12 X 105 Nm3/month), with a corresponding methane yield of 0.28 Nm3 CH4/kg CODremoved when the optimal operating parameters for OLR, temperature and RR are configured at 1.60 kg CODin/m3 day, 37.7 °C and 2.08 respectively. It could be concluded that moderate OLR (<1.6), moderate T (<44 °C), and moderate RR (<2.3) are required to achieve optimum COD removal and biogas production for each biogas plant.

Treatment of Dairy Wastewater by Electrocoagulation using Iron Filings Electrodes

This study investigated the treatment of dairy wastewater using the electrocoagulation method with iron filings as electrodes. The study dealt with real samples collected from local factory for dairy products in Baghdad. The Response Surface Methodology (RSM) was used to optimize five experimental variables at six levels for each variable, for estimating chemical oxygen demand (COD) removal efficiency. These variables were the distance between electrodes, detention time, dosage of NaCl as electrolyte, initial COD concentration, and current density. RSM was investigated the direct and complex interaction effects between parameters to estimate the optimum values. The respective optimum value was 1 cm for the distance between electrodes, (60 – 120) min for detention time, 250 mg NaCl/L added, C0/6 = 5,775 mg COD/L as initial COD concentration, and 7.884 - 8.077 mA/cm2 as current provided. At the optimum parameter values, the optimum COD removal efficiency was 73.4%. Meanwhile, the study also performed removal efficiency for nitrogen (N) and phosphate (P) due to their effects on the aquatic life and systems. The optimum removal efficiency for phosphorus and nitrogen was 98.0% and 80.3%, respectively. Due to its effects on the environment and to comply with local legislations, treating these wastewaters using eco-friendly processes was highly recommended taking in consideration the economic feasibility, flexibility and easiness to operate. In addition, the study proved that the high surface area for iron filings played a crucial role in removing process.

Optimisation of operating conditions during coagulation-flocculation process in industrial wastewater treatment using Hylocereus undatus foliage through response surface methodology.

In exploring the application of natural coagulants in industrial wastewater treatment, plant-based coagulants have been gaining more interests due to their potential such as biodegradability and easy availability. Hylocereus undatus foliage as a plant-based coagulant has been proven to be efficient during the coagulation-flocculation process; however, limited research has been reported focusing only on palm oil mill effluent (POME) and latex concentrate wastewater. In addition, no previous study has been carried out to determine the performance evaluation of Hylocereus undatus foliage in treating different types of wastewater incorporating different operating conditions using optimization techniques. Hence, this study employed response surface methodology (RSM) in an attempt to determine the performance evaluation of the coagulant in paint wastewater treatment. Four independent factors such as the pH value, coagulant dosage, rapid mixing speed and temperature were chosen as the operating conditions. Three water parameters such as turbidity, chemical oxygen demand (COD) and suspended solids (SS) were chosen as responses in this study. Results revealed that through central composite design (CCD) via Design Expert software, the optimum conditions were achieved at pH 5, coagulant dosage of 300mg/L, rapid mixing speed of 120rpm and temperature at 30°C. The experimental data was observed to be close to the model predictions with the optimum turbidity, COD and SS removal efficiencies found to be at 62.81%, 59.57% and 57.23%, respectively.

Low cost electrocoagulation process for treatment of contaminated water using aluminium electrodes from recycled cans

Electrocoagulation has been used to successfully treat diverse types of wastewaters. This treatment is carried out when there is an electro-dissolution of soluble anodes to form metal hydroxide flocks within the effluent. In this work an electrocoagulation setup was used to treat water from a contaminated stream. Aluminium anodes produced from recycled cans were used as electrodes. The contact time and voltage during electrocoagulation were varied and the corresponding effects on pH, Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and electrode weight gain/loss were observed. The average TDS of the raw water before Electrocoagulation was 286.7 mg/L. At 10 V, 20 V and 30 V, the average TDS of 246.3 mg/L, 227.3 mg/L and 220.7 mg/L were obtained after 120 min of electrocoagulation. The reduction in TDS signified improved anode dissolution and thus improved water quality. The results show that optimum COD and BOD removal efficiencies of 90.7% and 97.67% were obtained at 10 V.

Sustainable landfill leachate treatment: Optimize use of guar gum as natural coagulant and floc characterization

Sustainable wastewater treatment necessitates the application of natural and green material in the approach. Thus, selecting a natural coagulant in leachate treatment is a crucial step in landfill operation to prevent secondary environmental pollution due to residual inorganic coagulant in treated effluent. Current study investigated the application of guar gum in landfill leachate treatment. Central composite design in response surface methodology was used to optimize the performance of Chemical Oxygen Demand (COD) removal. Quadratic model developed indicated the optimum COD removal 22.57% at guar gum dosage of 44.39 mg/L, pH 8.56 (natural pH of leachate) and mixing speed 79.27 rpm. Scanning electron microscopy showed that floc was compact and energy-dispersive-x-ray analysis showed that guar gum was capable to adsorb multiple ions from the leachate. Structural characterization using Fourier Transform Infrared analysis demonstrated that hydrogen bonding between guar and pollutant particles was involved in coagulation and flocculation process. Therefore, guar gum coagulant present potential to be an alternative in leachate treatment where pH requirement is not required during treatment. Simultaneously, adsorption by guar gum offers added pollutant removal advantage.

Removal of disperse and reactive dyes from aqueous solutions using ultrasound-assisted electrocoagulation

This study investigates the effectivenesses of electrocoagulation, ultrasound, and ultrasound-assisted electrocoagulation processes for the removal of color and chemical oxygen demand (COD) from aqueous dye solutions. The coupling of electrocoagulation processes with ultrasound has been found useful for water and wastewater treatment in recent years. These experimental results demonstrate that ultrasound-assisted electrocoagulation processes provide greater color and COD removal than ultrasound or electrocoagulation processes alone. The optimum conditions for the combined process were found to be Fe-Fe-SS-SS/Al-Al-SS-SS (electrode connection type) in the monopolar electrode connection mode; 75 and 50 A m−2 (current density) for RR241 and DB 60, respectively, at a fixed frequency of 40 kHz; and an ultrasound power of 180 W in a 1 L aqueous solution. Under these optimum conditions, the color and COD removal efficiencies for an aqueous solution of 100 mg L−1 reached 99–99.9% and 100 - 100% for RR241 and DB 60, respectively. Complete removal was achieved for both COD and color by employing a combination of ultrasound-assisted electrocoagulation (US + EC) with only 4 min of electrolysis, while the traditional EC treatment achieved removal of approximately 87% of COD and 92% color for both dyes using the MP-P connection mode for 5 min. Conversely, ultrasound power alone removed approximately 34–60% of color and 30–36% of COD for RR241 and DB 60, respectively. Compared with the traditional EC treatment, the combination of ultrasound irradiation and electrocoagulation treatment significantly reduced electrode passivation and increased the removal of pollutants in shorter operation times.

Application of the central composite design to mineralization of olive mill wastewater by the electro/FeII/persulfate oxidation method

The olive mill wastewater is a major environmental problem, which is waiting for effective treatment. In this study, the mineralization of olive mill wastewater was investigated using the electro/FeII/persulfate process. The central composite design was utilized to examine the effect of each experimental variables (concentration of persulphate and FeII, treatment time and constant current) on the mineralization of olive mill wastewater. The optimum chemical oxygen demand removal percentage was obtained as 71.2% where the reaction conditions were 200 mA current, 250 mM persulphate, 25 mM FeII, and 6 h reaction time. In addition, the maximum percentage of total phenolic removal and the energy consumption were 88% and 4.50 kWh/kgCOD, respectively, which were obtained at the same reaction conditions mentioned above. ANOVA test was used to examine the reliability of the experimental method. The R2 and adjusted R2 coefficients were obtained as 0.9634 and 0.9305, respectively. Optimum experimental parameters were determined and theoretical equations were obtained for the degradation of olive mill wastewater. For the treatment of olive mill wastewater, an environmentally friendly oxidation process was examined and the effect of each experimental variables was clearly demonstrated. The obtained data was optimized for future applications.

Pretreatment of Food Industry Wastewater by Coagulation: Process Modeling and Optimization

In this study, coagulation processes using FeCl36H2O and Al2(SO4)318H2O as coagulants were employed and designed for chemical oxygen demand (COD) and total suspended solids (TSS) removal from food industry wastewater via response surface methodology (RSM). RSM was used for the optimization of coagulation processes and evaluation of the effects and interactions between process variables (pH, coagulant dosage and reaction time). ANOVA was used to analyze the experimental data obtained in the study and secondary regression models were developed by using Statgraphics Centurion XVI.I software. The optimum conditions were pH 9, dosage 1500 mg/L and time 25 min for maximum COD removal efficiency for FeCl36H2O and pH 9, dosage 1493 mg/L and time 25 min for Al2(SO4)318H2O. Under optimum conditions, COD and TSS removal efficiencies were 46.4% and 96.7% for FeCl36H2O and 31.2% and 96.2% for Al2(SO4)318H2O, respectively. ANOVA results showed that the responses of model have high coefficient values (R2 &amp;gt; 0.80), and hence the second order regression model can be explained with these experimental data. The proposed model fits very well with the experimental data with R2 of 0.9677 for COD and 0.9543 for TSS removal for FeCl36H2O and 0.9456 for COD and 0.9260 for TSS removal for Al2(SO4)318H2O, respectively. Model results showed that the RSM for coagulation processes using both coagulants is a powerful tool for optimizing the experimental conditions. Moreover, it can be concluded that both coagulation processes may be an effective alternative pre-treatment process for food industry wastewater.

Methane Production by Anaerobic Digestion of Spent Wash in Continuous Stirred Tank Reactor

DSW (Distillery Spent Wash) is superfluous residual liquid waste produced during the process of alcohol production. It is one of the most critical environmental issues which cause pollution. Despite strictness of standards imposed on effluent quality, partially or untreated effluent very often finds access to surface and groundwater. The distillery wastewater becomes a serious risk to the water quality in several regions around the globe. The ever-increasing generation of DSW lead to take an attempt to investigate a few aspects of anaerobic digestion of spent wash collected from a distillery. In the present study CSTR (Continuous Stirred Tank Reactor) was used at laboratory scale. The study was carried out to evaluate the performance of CSTR after the effective startup and the gradual increment in the OLR (Organic Loading Rate). The maximum methane gas (CH4) of 71.68 ml at the OLR of 1.0g of COD (Chemical Oxygen Demand)/L was observed. The optimum COD removal efficiency of the CSTR was 91% corresponding to OLR of 1g of COD/L. The pH ranges from 7.1-7.3 gave better performance and maximum stability of the process. By increasing the ORL, the VFA (Volatile Fatty Acids) content was also increased and reached to the 1.5g COD/L. However, the removal efficiency of TS (Total Solids) increased at an accelerated rate of OLR.

Comparison of electrocoagulation and photocatalytic process for treatment of industrial dyeing wastewater: Energy consumption analysis

AbstractSeveral processes have been used for dye and chemical oxygen demand (COD) removal from wastewater. Comparision of these methods are important in terms of efficiency and energy consumption. In recent years, advanced oxidation processes (AOPs) and electrocoagulation (EC) are the best methods for industrial dyeing wastewater treatment. In this study, comparision of energy consumption related to EC and photocatalytic process has been investigated. Effect of operational parameters on efficieny of both methods were studied. Effective parameters in EC treatment were initial pH, current density and distance between electrodes. In the photocatalytic process initial pH, photocatalyst concentration and aeration are effective parameters. Decolorization, COD removal, and energy consumption are as responses. Under the optimum conditions, decolorization and COD removal for EC and photocatalytic process were 85.57 and 34.48%, and 81.39 and 67%, respectively. Considering the same time for both methods, decolorization was the same, but COD removal was higher in photocatalytic processs. Energy consumption of EC process (&lt;0.01 kWh/m3.order of pollutant removal) was very lower than photocatalytic process (&gt;100 kWh/m3.order of pollutant removal). Since the wastewater treatment process must be economic, EC process was chosen. Another method such as photocatalytic processs must be selected due to improve the output.

Application of response surface methodology to optimize the COD removal efficiency of an EGSB reactor treating poultry slaughterhouse wastewater

Abstract The poultry slaughterhouse industry consumes a large volume of potable water for bird processing and equipment cleaning, which culminates in the generation of high strength poultry slaughterhouse wastewater (PSW). The wastewater contains high concentrations of organic matter, suspended solids, nitrogen and nutrients. Most poultry slaughterhouses in South Africa (SA) discharge their wastewater into the municipal sewer system after primary treatment. Due to its high strength, PSW does not meet SA's industrial discharge standards. Discharge of untreated PSW to the environment raises environmental health concerns due to pollution of local rivers and fresh water sources, leading to odour generation and the spread of diseases. Thus, the development of a suitable wastewater treatment process for safe PSW discharge to the environment is a necessity. In this study, a biological PSW treatment process using an Expanded Granular Sludge Bed (EGSB) was evaluated. Response surface methodology coupled with central composite design was used to optimize the performance of the EGSB reactor. The dependant variable used for optimization was chemical oxygen demand (COD) removal as a function of two independent variables, hydraulic retention time (HRT) and organic loading rate (OLR). The interactions between HRT, OLR and COD removal were analysed, and a two factorial (2FI) regression was determined as suitable for COD removal modelling. The optimum COD removal of 93% was achieved at an OLR of 2 g-COD/L/d and HRT of 4.8 days. The model correlation coefficient (R2) of 0.980 indicates that it is a good fit and is suitable for predicting the EGSB's COD removal efficiency.

Chemically Enhanced Primary

The Chemically enhanced process is considered to be a physicochemical technology for domestic wastewater treatment. The objective of this paper is to improve the efficiency of primary treatment processes and reducing the Hazardous Material and cost of the secondary treatment stage either by eliminating a biological treatment, where conditions and standards allow or by reducing the secondary treatment requirements. Analysis of physicochemical parameters as well as the treatment efficiency of aluminum sulfate (alum), ferric chloride (FeCl3), lime (CaO), and seawater was used. The effect of pH and the coagulant dosages were studied as well as mixing and settling time. Conditions were optimized according to the removal efficiencies measured in terms of reduction in the concentration of total suspended solids (TSS), biological oxygen demand (BOD5), and chemical oxygen demand (COD). The optimum COD removal % was achieved at a settling time of 20 minutes, while at pH~6, alum gave a high turbidity % removal of approximately 90% at the dose of 70 mg/l. FeCl3 gave a high turbidity % removal of approximately 95% at the dose of 40 mg/l. Turbidity removal and TSS removal gave a similar pattern at a settling time of 10-20 minutes, where best results were achieved. The results also showed that at pH~4, FeCl3 gave high COD% removal of approximately 90% at the dose of 40 mg/l. By studying the effect of stirrers’ speed (rpm), the results showed that an increase in the mixing intensity, above 80 rpm decreases the removals of COD, Turbidity and TSS when using alum as a coagulant.

Chemically Enhanced Primary

The Chemically enhanced process is considered to be a physicochemical technology for domestic wastewater treatment. The objective of this paper is to improve the efficiency of primary treatment processes and reducing the Hazardous Material and cost of the secondary treatment stage either by eliminating a biological treatment, where conditions and standards allow or by reducing the secondary treatment requirements. Analysis of physicochemical parameters as well as the treatment efficiency of aluminum sulfate (alum), ferric chloride (FeCl3), lime (CaO), and seawater was used. The effect of pH and the coagulant dosages were studied as well as mixing and settling time. Conditions were optimized according to the removal efficiencies measured in terms of reduction in the concentration of total suspended solids (TSS), biological oxygen demand (BOD5), and chemical oxygen demand (COD). The optimum COD removal % was achieved at a settling time of 20 minutes, while at pH~6, alum gave a high turbidity % removal of approximately 90% at the dose of 70 mg/l. FeCl3 gave a high turbidity % removal of approximately 95% at the dose of 40 mg/l. Turbidity removal and TSS removal gave a similar pattern at a settling time of 10-20 minutes, where best results were achieved. The results also showed that at pH~4, FeCl3 gave high COD% removal of approximately 90% at the dose of 40 mg/l. By studying the effect of stirrers’ speed (rpm), the results showed that an increase in the mixing intensity, above 80 rpm decreases the removals of COD, Turbidity and TSS when using alum as a coagulant.

Treatment of slaughterhouse wastewater with the electrochemical oxidation process: Role of operating parameters on treatment efficiency and energy consumption

In this study, investigation of the applicability and efficiency of electrochemical oxidation (EO) processes for slaughterhouse wastewater was targeted by evaluating the treatment efficiency and energy consumption values together. The effect of operating parameters such as type of supporting electrolyte (SE) (Na2SO4, NaNO3 and NaCl), concentration of SE (0.01-0.1 M), initial wastewater pH (3–9), current density (CD) (4.73–14.20 mA/cm2) and dilution rate of wastewater (1/1-1/4) on removal of chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), total suspended solids (TSS) and color were investigated. The most effective electrolyte type was observed as NaCl. With the use of 0.025 M NaCl and 25 °C reaction temperature, at fixed 4.73 mA/cm2 CD and pH of 7.03 for 4 h reaction time, the optimum conditions for both energy consumption and removal efficiency for treatment of SWW were obtained. At optimum conditions, TSS, TOC, COD, TN and color removal efficiencies were found as; 99.5%, 88.0%, 92.2%, 93.5% and 99.9%, respectively, and the energy consumption under these conditions were 153.57 kWh/m3 and 14.12 kWh/kg COD. The energy cost was calculated as 1.69 $/kg COD. Also, results distinctly show that almost full mineralization of organics is obtained after 4 h treatment. Unluckily, taking into account the large volumes of effluent produced per slaughtering cycle, the need for long treatment times is impractical, yet if the reactor is developed to include hydrodynamic conditions or combined with another treatment process which is shorter than the EO treatment time a novel setup may be possible.

Application of Response Surface Methodology for Sago Wastewater Treatment by Ozonation

A treatment method based on the degradation of sago processing wastewater using ozonation process was conducted in this research study. The optimization of the process variables was designed with the aid of software called Design Expert and the technique was called response surface methodology (RSM) in Central composite design. The effect of ozonation variables like pH, treatment time and ozone concentration on the reduction of chemical oxygen demand (COD) of sago waste water was investigated. Interestingly, two different types of results like maximum removal of COD and optimum removal of COD were observed. Maximum COD removal of 62.45% was at pH 9.8, ozonation time 95.7 min, ozone dose 42% and optimum COD removal 0f 56.7% was at pH 9.8, ozonation time 35.7 min, and ozone dose 42%. Bacterial count was found to be nil after ozonation and microscopic observation of biomass proved that the sludge content had effectively reduced after ozonation treatment. It was determined that the ozonation of sago wastewater was a promising effort in wastewater treatment.

A comprehensive study on the electrocatalytic degradation, electrochemical behavior and degradation mechanism of malachite green using electrodeposited nanostructured β-PbO2 electrodes

This work has investigated the electrocatalytic degradation of malachite green (MG) in aqueous solution with G/β-PbO2, SS316/β-PbO2, Ti/β-PbO2 and Pb/β-PbO2 electrodes. These electrodes show high oxygen evolution over-potential and excellent electrochemical degradation efficiency for organic pollutants. The optimum conditions for the degradation of MG were obtained by studying the effects of different parameters, such as initial current densities and initial MG concentration. The remaining organic compounds concentrations (color) and chemical oxygen demand (COD) removal efficiency were investigated and compared. The results indicate that the efficiency of G/β-PbO2 electrode for both color and COD removals is more than those of other electrodes. At the optimum conditions, the color and COD removal efficiencies of MG reached up to 100% and 94%, respectively. The observed degradation rate of MG was found to vary in the order G/β-PbO2> SS316/β-PbO2> Ti/β-PbO2> Pb/β-PbO2. Moreover, in this paper, the electrochemical behavior and adsorption characteristic of MG in aqueous solutions with different pH values were studied in details at glassy carbon electrode using both constant-current coulometry and cyclic voltammetry techniques. This study has led to the proposed mechanism for the oxidation pathway of MG and determine the absorption properties of MG in acidic, neutral and basic solutions. We also proposed the mineralization pathway of MG at β-PbO2 electrode.

An efficient technique for dairy wastewater treatment

The aim of this study was to consider the efficiency of the electro‐Fenton process for organic compound reduction in an industrial dairy effluent. Experiments were conducted to evaluate the effect of several parameters, such as reaction time, pH, H2O2/Fe2+ molar ratio and volume fraction of H2O2 to dairy wastewater (mL/L), on the process performance. The Taguchi technique was applied to investigate the optimum operating conditions. The optimum chemical oxygen demand removal (93.24%) was experimentally obtained at a pH value of 7.58, reaction time of 87.13, current density of 58.5, H2O2/Fe2+ molar ratio of 3.62 and volume fraction of H2O2 to dairy wastewater of 1.39 mL/L.

Alcoholic wastewater treatment using electro-Fenton technique modified by Fe2O3 nanoparticles

In this research, the effects of several parameters such as reaction time, current density, pH, H2O2/Fe2+ molar ratio, and volume fraction of H2O2 to alcoholic wastewater (ml/l) on the electro-Fenton process were investigated. For this purpose, iron nanoparticles were deposited on graphite electrodes. Efficiency of electrochemical oxidation process was tested by Chemical Oxygen Demand (COD) determination. The optimum COD removal (66.15%) was obtained at pH of 2.84, reaction time of 69.29min, current density of 51.54mA, H2O2/Fe2+ molar ratio of 3.7 and volume fraction of H2O2 to alcoholic wastewater of 1.62ml/l. It was concluded that the electro-Fenton process with graphite electrodes coated by iron nanoparticles was more efficient than the electro-Fenton with iron electrodes.

High-strength distillery wastewater treatment using catalytic sub- and supercritical water

In the current research, we have studied the catalytic sub- and supercritical water (SCW) treatment of distillery wastewater (DWW) in a batch tubular reactor. Experiments were conducted in the temperature range of 250–400°C, reaction time of 30–120min at constant pressure of 25MPa with the aim of chemical oxygen demand (COD) and color removal. The initial COD concentration was 60,000mgl−1, regarded as high-strength wastewater. The experiments were performed in the presence and absence of different homogeneous (MnSO4·7H2O, ZnSO4·7H2O) and heterogenous (TiO2, CuO, MnO2) catalysts. The obtained results showed that increasing the temperature from 250°C to 400°C has a positive influence on both COD reduction (18.3–50%) and color removal (up to 48.5%) within 30min and without catalyst, while reaction time has no significant effect. By applying both homogeneous and heterogeneous catalysts, COD and color removal efficiencies were considerably increased. The optimum COD removal efficiencies of 74.4% and 75.1% were obtained by CuO (10wt%) and MnO2 (10wt%), respectively at 400°C and 30min, while the highest COD removal efficiency was 80.9% at 400°C, 120min and 5wt% of CuO. Addition of catalysts also greatly influenced color removal, such that MnO2 could remove up to 98.2% of wastewater color at 400°C in 30min.

Evaluation of an electrocoagulation process for the treatment of bagasse-based pulp and paper industry wastewater

In this study, an attempt was made to investigate the efficiency of continuous electrocoagulation process (CEC) to treat bagasse-based pulp and paper industry wastewater. Different operating conditions such as initial pH (5–9), current density (15–35 mA/cm2), electrode distance (4–6 cm) and flow rate (25–55 ml/min) were varied in order to study the removal efficicency of chemical oxygen demand (COD) and total suspended solids (TSS). Electrical enrgy consumption (EEC) of the process was also investigated. Four factors three level Box–Behnken response surface design (BBD) was used to evaluate the effect of process variables on CEC. From the BBD results, second-order polynomial models were developed and all the process variables have significant effect on the removal efficiencies. 3D response surface contour plots were used to study the interactive effects of the process conditions. Under the optimum operating conditions COD and TSS removal efficiencies were found to be 84 and 91% with EEC of 15.25 Wh. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 411–419, 2015