Optimum Chemical Oxygen Demand Research Articles

Comparative study on the removal of COD from POME by electrocoagulation and electro-Fenton methods: Process optimization

This research focuses on the Chemical Oxygen Demand (COD) treatment in palm oil mill effluent by electrocoagulation and electro-Fenton methods to solve it. Initially, the aqueous solution precipitates in acid condition at pH of about two. This study focuses on the palm oil mill effluent degradation by Fe electrodes in a simple batch reactor. This work is conducted by using different parameters such as voltage, electrolyte concentration of NaCl, volume of H2O2 and operation time. The processing of data resulted is by using response surface method coupled with Box-Behnken design. The electrocoagulation method results in the optimum COD reduction of 94.53% from operating time of 39.28 minutes, 20 volts, and without electrolyte concentration. For electro-Fenton process, experiment points out that voltage 15.78 volts, electrolyte concentration 0.06 M and H2O2 volume 14.79 ml with time 35.92 minutes yield 99.56% degradation. The result concluded that the electro-Fenton process was more effective to degrade COD of the palm-oil-mill effluent compared to electrocoagulation process.

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.

Optimization of waste stabilization pond performance for piggery waste treatment using response surface methodology

The treatment of piggery wastewater using the waste stabilisation pond was studied in a semi- continuous process. Optimization of Chemical Oxygen Demand (COD) removal was conducted using response surface methodology where pH, temperature and retention time were independent variables. The Box-Behnken design approach, an experimental design was used for creating set of experimental runs needed for optimizing COD removal. An attempt was also made to optimize COD removal by reducing hydraulic retention time while maintaining pH and temperature of a defined range. Analysis of variance (ANOVA) was conducted on model terms and the results revealed that the coefficient of determination value (R2) of % COD removal was 0.86, 0.88, and 0.86 for the anaerobic, facultative and maturation pond respectively. Highest desirability was obtained for optimum COD % removal and this was 0.89, 0.89 and 1.0 for ponds.The waste stabilisation pond treatment process can effectively be improved on for piggery wastewater treatment.DOI: http://dx.doi.org/10.5755/j01.erem.73.2.17696

Separate production of hydrogen and methane from biodiesel wastewater with added glycerin by two-stage anaerobic sequencing batch reactors (ASBR)

The objective of this study was to investigate hydrogen and methane production from biodiesel wastewater with added glycerin by using two-stage anaerobic sequencing batch reactors (ASBR) under 37 °C with a recycle ratio of the effluent from the methane ASBR unit-to-the feed flow rate of 1:1. Hydrogen ASBR unit was operated at a constant pH of 5.5 whereas the pH of methane ASBR unit was not controlled. Glycerin was added into biodiesel wastewater having 2330 mg/l COD to obtain a constant feed chemical oxygen demand (COD) of 45,000 m/l. At optimum COD loading rate 11.3 kg/m3d (based on feed COD load and methane ASBR volume), the system provided the highest overall hydrogen and methane production performance (75.15 ml H2/g glycerin removed) which was consistent with the maximum overall COD removal of 76.7% and the highest overall glycerin uptake of 90%. Most of added glycerin was converted to gaseous products with small amounts of organic acids and 1,3 propanediol. The low volumetric ratio of hydrogen ASBR unit-to-methane ASBR unit of 1:6 resulted in low hydrogen yields with high methane yields. Process performance of the two-stage ASBR system was limited by the inhibition of total volatile organic acids produced in both bioreactors.

Degradation of refractory organics in biotreated landfill leachate using high voltage pulsed discharge combined with TiO2

The effect of high voltage pulsed discharge (HVPD) combined with TiO2 on the degradation of refractory organic compounds in actual biotreated landfill leachate was investigated. The optimal chemical oxygen demand (COD) removal efficiency could achieve to 58.9% using HVPD+TiO2 within 30min at 40kV, 400Hz, and the conductivity of 4.05mscm−1 in gas-liquid pulsed discharge. The aromatic compounds decreased by 33.6% compared with HVPD alone according to the UV absorbance at 254nm. Moreover, the fluorescence intensity of humic and fulvic substances was greatly decreased. Active species such as OH radical and H2O2 were enhanced in the presence of TiO2, resulting in more high molecular weight organic matter into small molecules or mineralized. In addition, possible degradation pathways was proposed based on acetophenone, which is effective for the degradation of organic matter in biotreated landfill leachate as long as the active species increased.

Biomass recovery during municipal wastewater treatment using photosynthetic bacteria and prospect of production of single cell protein for feedstuff

ABSTRACTUtilization of photosynthetic bacteria (PSB) for wastewater treatment and production of biomass for economical single cell protein production is a feasible option. In this study, Rhodopseudomonas sp. CSK01 was used for municipal wastewater treatment and the effect of initial pH, light intensity and additional carbon source was investigated. Optimum chemical oxygen demand (COD) removal and biomass production were achieved when the initial pH and light intensity were 7 and 4000 lux, respectively. The specific growth rate, biomass yield and biomass productivity were found to be 0.4/d, 3.2 g/g COD and 2.1 g/L/d, respectively, which were improved by 100%, 167% and 200% relative to the original condition. Under the optimal conditions, COD removal reached 85% and maximum biomass was 6.2 g/L accomplished within three days of cultivation. The biomass had a relatively high protein content (60.1%) consisting of all essential amino acids. The contents of histidine, lysine, phenylalanine and leucine were superior to those of the previously described PSB. Results showed that COD removal was not improved in the presence of additional carbon sources (glucose, sucrose and malic acid). The addition of malic acid significantly increased the biomass accumulation by 279% relative to the original condition, whereas COD removal was declined due to carbon catabolite repression. In this study, PSB biomass recovery and catabolite repression are proposed in municipal wastewater treatment by Rhodopseudomonas sp.

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.

M-Al-SO4 layered double hydroxides (M=Zn, Mg or Ni): synthesis, characterization and textile dyes removal efficiency

Mg–Al, Zn–Al, and Ni–Al layered double hydroxides (LDH) materials with molar ratio (M2+/Al3+) of 3 were synthesized via co-precipitation method. The as-synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and simultaneous thermogravimetric–differential thermal analysis (TGA/DTA). XRD analyses showed that Zn–Al-SO4 had the greatest lattices parameters followed by Mg–Al-SO4 and Ni–Al-SO4. FTIR confirmed clearly the presence of sulfate anions in the structure of LDHs with the presence of carbonate impurity in the interlayer. TGA/DTA analysis indicates a better thermal stability of Zn–Al-SO4 vs. Ni–Al-SO4 and Mg–Al-SO4. The capability of the materials for textile dye removal was investigated using methyl orange (MO) as a model dye and an industrial textile effluent. Experimental results showed that pH is the most affecting factor in dye removal. The effective pH range for dye removal was between 3.5 and 5. The adsorption process can be well described by the pseudo-second-order kinetic model. The Langmuir model fit equilibrium data with exceptional maximum adsorption capacities for MO of 2,758, 1,622, and 800 mg/g, respectively, in the case of Zn–Al-SO4, Mg–Al-SO4, and Ni–Al-SO4. Color and chemical oxygen demand (COD) reduction from industrial textile effluent increased with the increase in the amount of LDHs. The optimum color and COD reduction were obtained by Zn–Al-SO4.

Optimization of operational parameters of electrocoagulation process for real textile wastewater treatment using Taguchi experimental design method

In this paper, Taguchi method was applied to determine the optimum operating conditions for textile wastewater treatment by electrocoagulation (EC) with iron electrodes. The removal efficiency of chemical oxygen demand (COD) and turbidity was considered as the performance parameters. L9 orthogonal array (OA, three factors in three levels) was selected as the experimental design for three controllable parameters mentioned above. These parameters that mainly affect the EC process were specified as initial pH, current density and electrolysis time. Each parameter was examined at three levels using Taguchi method. Performance analysis was followed by a variance analysis in order to determine the optimum levels and relative magnitude of the effect of parameters. Taguchi’s “the larger the better” performance formula was used. The optimum operating conditions in terms of COD and turbidity were found to be initial pH of 7 and 8, current density of 150 A/m2 and electrolysis time of 20 and 30 min. At the optimum conditions, COD and turbidity removal efficiencies were obtained as 42.2 and 99.1%, respectively. Operating costs of EC process for COD and turbidity removals were calculated as 1.52 and 1.73 €/m3. Besides, the UV–Vis spectrum was used to detect the changes in textile wastewater quality. In EC process, COD concentration of treated effluent was above the permitted direct discharge limits. So, active carbon was used to increase COD removal efficiency of EC process under the optimum operational conditions. COD and turbidity removal efficiencies in the EC/activated carbon (AC) process by adding 2,000 mg/l AC were 67.9 and 99.3%, respectively. Operation cost of EC/AC process is calculated as 1.64 €/m3. Besides, the operation costs at different operating conditions were also determined.

Effects of volatile solid concentration and mixing ratio on hydrogen production by co-digesting molasses wastewater and sewage sludge.

Co-digesting molasses wastewater and sewage sludge was evaluated for hydrogen production by response surface methodology (RSM). Batch experiments in accordance with various dilution ratios (40- to 5-fold) and waste mixing composition ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100, on a volume basis) were conducted. Volatile solid (VS) concentration strongly affected the hydrogen production rate and yield compared with the waste mixing ratio. The specific hydrogen production rate was predicted to be optimal when the VS concentration ranged from 10 to 12 g/l at all the mixing ratios of molasses wastewater and sewage sludge. A hydrogen yield of over 50 ml H2/g VS(removed) was obtained from mixed waste of 10% sewage sludge and 10 g/l VS (about 10-fold dilution ratio). The optimal chemical oxygen demand/ total nitrogen ratio for co-digesting molasses wastewater and sewage sludge was between 250 and 300 with a hydrogen yield above 20 ml H2/g VS(removed).

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 performance in a combined UASB and aerobic contact oxidation process treating acrylic wastewater

The lab-scale and full-scale performance of a combined mesophilic up-flow anaerobic sludge blanket (UASB) and aerobic contact oxidation (ACO) process for treating acrylic wastewater was studied. During lab-scale experiment, the overwhelmed volumetric load for UASB was above 6 kg chemical oxygen demand (COD) ·(m−3·d−1) since COD removal efficiency dropped dramatically from 73% at 6 kg COD·(m−3·d−1) to 61% at 7 kg COD·(m−3·d−1) and 53% at 8 kg COD·(m−3·d−1). Further results showed that an up-flow fluid velocity of 0.5 m h−1 for UASB obtained a highest COD removal efficiency of 75%, and the optimum COD volumetric load for the corresponding ACO was 1.00 kg COD·(m−3·d−1). Based on the configuration of the lab-scale experiment, a full-scale application with an acrylic wastewater treatment capacity of 8 m3 h−1 was constructed and operated at a volumetric load of 5.5 kg COD·(m−3·d−1), an up-flow fluid velocity of 0.5 m h−1 for UASB and a volumetric load of 0.9 kg COD·(m−3·d−1) for ACO; and the final effluent COD was around 740 mg L−1. The results suggest that a combined UASB–ACO process is promising for treating acrylic wastewater.

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

Influence of electrical field on COD removal and filterability of activated sludge

Three batch reactors were operated in order to investigate the effects of electrocoagulation and electrical field on chemical oxygen demand (COD) degradation rates, efficiencies, and filterability. The first reactor was operated with iron electrode, the second reactor was operated with relatively inert titanium electrode, and the last one was run as control without any electrical field. The electrical field application with iron electrodes increased the COD degradation rates at 0.5 and 2.5 V/cm with COD removals around 90%. However, the removal efficiencies decreased down to 70% at 5 V/cm. Increases in degradation rates were observed with titanium electrodes with time at all the three voltages. Activated sludge from the reactor with iron electrodes showed excellent filtration properties at 2.5 and 5 V/cm experiments. This was attributed to iron precipitates screening membrane foulants and preventing the formation of high resistive cake layer and pore structure rather than floc size increase. Electrocoagulation showed promising results in reducing membrane fouling. A critical voltage gradient should be maintained and the magnitude of iron electrode dissolution should be controlled in the reactor to obtain optimum COD degradation and to enhance filterability. Sludge samples from reactor with titanium electrodes showed poor filterability as voltage gradient increased (at 5 V/cm). This was attributed to the elevated soluble protein content (SMPp) concentration due to cell disruption.

Application of Carbonized Poultry Waste in the Removal of Chemical Oxygen Demand (COD) from Dye Wastewater: Kinetic Study

The removal of COD from dye wastewater by poultry waste activated carbon using KOH as an activating agent was carried out with two step process. Batch adsorption method was employed at various contact time. The study indicated optimum COD removal of 65.15% at the contact of 120 minutes and 150 minutes respectively. In the kinetic study, pseudo first-order, pseudo second-order, Natarajam and Khalaf first order and elovich model were tested but pseudo second-order showed the best fit for the adsorption process. The result further revealed that poultry waste, an available adsorbent is very effective in COD removal from dye wastewater.

Effects of flow rate and chemical oxygen demand removal characteristics on power generation performance of microbial fuel cells

Two microbial fuel cells with different oxygen supplies in the cathodic chamber were constructed. Electrogenic capabilities of both cells were compared under the same operational conditions. Results showed that binary quadratic equations can express the relationships between chemical oxygen demand degradation rate and chemical oxygen demand loading and between chemical oxygen demand removal rate and chemical oxygen demand loading in both cells. Good linear relationships between power output (voltage or power density) and flow rate and between power output and chemical oxygen demand degradation rate were only found on the cell with mechanical aeration in the cathodic chamber, but not on the cell with algal photosynthesis in the cathodic chamber. The relationships between power output and chemical oxygen demand removal rate and between power output and effluent chemical oxygen demand concentration on both cells can be expressed as binary quadratic equations. The optimum flow rates to obtain higher power density and higher Coulombic efficiency in the cell with mechanical aeration in the cathodic chamber (=0.85 mW/m2 and 0.063%) and in the cell with algal photosynthesis in the cathodic chamber (=0.65 mW/m2 and 0.05%) are about 1000 and 1460 μL/min, respectively. The optimum chemical oxygen demand removal rates to obtain higher power density and higher Coulombic efficiency in the cell with mechanical aeration in the cathodic chamber (=1.2 mW/m2 and 0.064%) and in the cell with algal photosynthesis in the cathodic chamber (=0.81 mW/m2 and 0.051%) are about 40.5 and 36.5%, respectively.

Performance evaluation of an Anaerobic Migrating Blanket Reactor in the biodegradation of perchloroethylene from industrial wastewaters

Aims: The aim of this study is to determine the PCE biodegradation potential in an Anaerobic Migrating Blanket Reactor (AMBR) that has not been used so far for the bioremediation of this compound, in high concentration, and to evaluate the system performance. Materials and Methods: This study was an Experimental - Interventional study that was done from April 2010 to March 2011, in the Isfahan University of Medical Sciences. The AMBR was used in a type of laboratory scale, with a volume of 10 L, which was divided into four compartments, for the biological degradation of PCE in a synthetic substrate. The startup was done using anaerobic digested sewage sludge. The performance of the reactor was evaluated during four periods, with a PCE loading rate of 3.75 until 75 mg PCE/L.d. The hydraulic retention time (HRT) was 32 hours. Results: Optimum chemical oxygen demand (COD) removal efficiency was obtained, 98%, with an organic loading rate (OLR) equal to 3.1 g COD/L.d. For PCE removal, the optimum efficiency was observed to be 99.8%, with a PCE loading rate equal to 37.5 mg PCE/L.d. The average COD and PCE removal rates for the whole activity period of the reactor were 91.4 and 99.5%, respectively; 1.1 ± 0.7% from the influent PCE was adsorbed on the biomass and 20% was found in the headspace. Conclusions: The AMBR reactor, which provides full-scale studies and uses real industrial wastewater polluted with PCE, is a simple, efficient, and reliable method for the treatment of PCE.

Using D-optimal experimental design to optimise remazol black B mineralisation by Fenton-like peroxidation

The mineralisation of remazol black B (RBB) was studied at concentrations ranging from 20-1000 mgL−1. The work was aimed at investigating the Fenton-like peroxidation of RBB at a concentration typically obtained in Batik cottage industries. Other response parameters were degradation and colour removal efficiencies. The parameters that were measured included total organic carbon (TOC), chemical oxygen demand (COD) as well as absorbance for mineralisation, degradation and colour. To optimise the process, the interaction effects of several controlling variables on the treatment process were examined using dispersion matrix-optimal design and response surface analysis. Four specific variables: initial dye concentration (Dye)o; the molar ratio of oxidant to dye organic strength (H2O2):(COD); the mass ratio of the oxidant to the catalyst (H2O2):(Fe3+) and reaction time (t r), were observed. Three reduced empirical models, one for each response, were developed for describing the treatment process. For 20, 510 and 1000 mgL−1, the optimum %TOC reduction and oxidation times were 44% for 95 min, 52% for 52.5 min and 68% for 10 min corresponding to 67, 81 and 75% COD reduction, respectively. The optimum COD reduction and oxidation times were 89% for 95 min, 91% for 10 min and 84% for 95 min for concentrations of 20, 510 and 1000 mg L−1, respectively. For all concentrations, total colour removal was achieved. A comparison of the results obtained in this study with literature values for traditional Fenton, photo-Fenton and photo-Fenton-like oxidation indicated that the TOC reduction obtained using the Fenton-like process was satisfactory.

Inhibitory effects of Cu (II) on fermentative methane production using bamboo wastewater as substrate

The toxic effects of Cu (II) present in bamboo industry wastewater (BIWW) upon its anaerobic biodegradability of organic content were investigated. The analysis through the Modified Gompertz model indicated that the optimum chemical oxygen demand (COD) concentration for digestion was 22,780 mg L −1 with a maximum R m (maximum CH 4 production rate) value of 2.8 mL h −1, corresponding to a specific methanogenic activity (SMA) of 2.38 mLCH 4 gVSS −1 h −1. The inhibitory effects of Cu (II) on cumulative methane production depended on its concentration and contact time. Low concentrations (5 mg L −1) of Cu (II) showed a stimulating effect on methanogenesis. Methane was not detected when the Cu (II) concentration was increased beyond 300 mg L −1. The IC 50 value of Cu (II), the Cu (II) concentration that causes a 50% reduction in the cumulative methane production, was 18.32 mg L −1 (15.9 mg Cu (II) gVSS −1).

Treatment performance evaluation of chemical oxygen demand from landfill leachate by electro‐coagulation and electro‐fenton technique

AbstractThe removal of chemical oxygen demand (COD) from landfill leachate by electro‐coagulation (EC) using iron sacrificial anode has been investigated. The process performance is analyzed in terms of COD removal efficiency and the important cost‐related parameters such as electrode and energy consumptions, as a function of initial pH, conductivity, current density, and operation time. The optimum COD removal (65.85%) was obtained with typical operating conditions: current density, 30 mA/cm2; operation time, 180 min; conductivity, 16.4 ms/cm; and initial pH, 6.54. At these conditions, the electrode and energy consumptions during the electrolysis were determined as 0.418 kg COD/kg Al and 11.092 kWh/kg COD, respectively. In addition, the EC and Fenton processes are applied together referred to as the electro‐Fenton process in the literature for the removal of COD from landfill leachate and effect of operation time and hydrogen peroxide concentration is examined. The process was very fast in the first 15 min, and then it slowed down till it was complete in 60 min. An optimum COD removal efficiency of 74.21% was obtained at 5000 ppm hydrogen peroxide dosage and 60 min. © 2010 American Institute of Chemical Engineers Environ Prog, 2012