Percentage Removal Of Chemical Oxygen Demand Research Articles

Oil removal from an oil-in-water emulsion by electrochemical process using Taguchi method

In this study an electrochemical treatment process of an oil-in-water emulsion was investigated using an anode composed of carbon-polytetrafluoroethylene and manganese oxide as an electrocatalyst. The effects of operating parameters including initial chemical oxygen demand (COD), NaCl concentration, pH, voltage and time on decreasing COD of the emulsion were studied. The Taguchi method was used in the design of experiments, and to analyze data. L16(45) orthogonal array was selected for experimental designing. Analysis of variance was applied to determine optimum conditions and the most significant parameters affecting the response of the process. According to the results of analysis, time is the most effective parameter, with percentage contribution of 65.6% followed by NaCl concentration of 17.49%, voltage of 7.29%, and initial COD concentration of 7.09%. Also it was found that pH has an insignificant effect on COD removal percentage. The optimum conditions were found as follows: the fourth level of initial COD (1,200 mg/L) and NaCl concentration (1,500 mg/L), third level of voltage (5 V) and fourth level of time (180 min). Finally the confirmation test was performed under optimum conditions. Observed value of this experiment (70.11%) was within the range of confidence limit of predicted performance (73.19 ± 5%).

Dragon Fruit Foliage Plant‐Based Coagulant for Treatment of Concentrated Latex Effluent: Comparison of Treatment with Ferric Sulfate

The effectiveness of dragon fruit foliage as a natural coagulant for treatment of concentrated latex effluent was investigated and compared with ferric sulfate, a chemical coagulant. Dragon fruit is a round and often red‐colored fruit with scales‐like texture and is native to south American countries which is also cultivated and heavily marketed in southeast Asian countries. Its foliage represents a part of its overall plant system. Latex effluent is one of the main byproduct from rubber processing factories in Malaysia. Three main parameters investigated were chemical oxygen demand (COD), suspended solids (SS), and turbidity of effluent. Coagulation experiments using jar test were performed with a flocculation system where the effects of latex effluent pH as well as coagulation dosage on coagulation effectiveness were examined. The highest recorded COD, SS, and turbidity removal percentages for foliage were observed for effluent pH 10 at 94.7, 88.9, and 99.7%, respectively. It is concluded that the foliage showed tremendous potential as a natural coagulant for water treatment purposes. The foliage could be used in the pretreatment stage of Malaysian latex effluent prior to secondary treatment.

Electro-hydrolysis of cheese whey solution for hydrogen gas production and chemical oxygen demand (COD) removal using photo-voltaic cells (PVC)

Abstract Diluted cheese whey (CW) solution was used for hydrogen gas production by electro-hydrolysis using photo-voltaic cells (PVC) as source of electricity. Effects of initial chemical oxygen demand (COD) concentration on the rate and yield of hydrogen gas production were investigated using a completely mixed and sealed reactor with aluminum electrodes. Cumulative hydrogen gas formation (CHF) increased with increasing initial COD concentration. The highest cumulative hydrogen gas volume (26472 mL), hydrogen gas production rate (4553 mL d −1 ), hydrogen yield (7004 mL H 2 g −1 COD), and percent COD removal (21.5%) were obtained with initial COD of 35172 mg L −1 . H 2 gas formation from water control was only 5365 mL. pH of the CW solution increased with decreasing conductivities during the course of experiments. Gas phase contained more than 99% H 2 at the end of experiments. The highest energy efficiency (20.4%) was also obtained with the highest COD content. Nearly pure hydrogen gas formation by electro-hydrolysis of cheese whey using PVC panels was proven to be an effective method.

Optimization of the landfill leachate treatment by the Fenton process

AbstractThe Fenton process was used with the objective of improving the biodegradability of the leachate pretreated biologically up to a value compatible with a subsequent biological treatment. The optimum reaction and settlement pH was 3, both for the organic matter removal and for the improvement of the biodegradability. The chemical oxygen demand (COD) removal increased at increasing Fe2+ dosages, from 75.6% for 300 mg/L to 89.0% for 1400 mg/L. The most significant enhancement (84.8%) was obtained with 800 mg Fe2+/L. However, the biological oxygen demand/chemical oxygen demand ratio (BOD/COD) was almost the same at all the Fe2+ dosages, around 0.29. Moreover, varying the H2O2 concentration between 600 and 3600 mg/L, COD removal percentages were between 85.9 and 89.0%. However, the BOD/COD ratio increased at increasing H2O2 dosage up to 3000 mg/L, from 0.12 at 600 mg/L to 0.29 at 3000 mg/L.

Influence of Experimental Parameters in the Treatment of Distillery Effluent by Electrochemical Oxidation

The electrochemical oxidation of distillery effluent was studied in a batch reactor in the presence of supporting electrolyte NaCl using Mixed Metal Oxide (MMO) electrode. The effect of operating parameters such as current density, initial pH, and initial electrolyte concentration on the percentage of Chemical Oxygen Demand (COD) removal, power consumption, and current efficiency were studied. The maximum percentage removal of COD was observed to be 84% at a current density of 3 A/dm2at an electrolyte concentration of 10 g/l with an effluent COD concentration of 1000 ppm and at an initial pH of 6. The operating parameters for the treatment of distillery effluent by electrochemical process were optimized using response surface methodology by CCD. The quadratic regression models with estimated coefficients were developed for the percentage removal of COD and power consumption. It was observed that the model predictions matched with experimental values with an R2 value of 0.9504 and 0.9083 for COD removal and power consumption respectively. The extent of color removal and oxidation of organic compounds were analyzed using UV spectrophotometer and HPLC.

Experimental Evaluation of Activated Sludge–Biofilm Reactor: Influence of Composite Media

AbstractExperimental studies were conducted on a 5-L laboratory-scale activated sludge–biofilm reactor in two phases: phase I with 30% filling (Bioflow 9) and Phase II with 60% filling [Biofilm 9 (30%), Flocor (15%), and BioBall (15%)]. The substrate used in the study was prepared by diluting the vinasse with tap water and adding urea, KH2PO4 (source of nitrogen and phosphorous), and MgSO4, resulting in a chemical oxygen demand (COD)/N/P ratio of 300/10/1.COD/N/P=300/10/1. At 30% Bioflow 9 filling, increasing the influent COD concentration [while maintainig the same hydraulic residence time (HRT)] reduced the efficiency of COD removal. At 60% filling, it was observed that increasing the feed composition while maintaining the same HRT reduced the percentage removal of COD and NH4+-N. The sludge concentration within the reactor slightly increased with increase in feed concentration and a stage is reached where the sludge settling in the settling tank was very poor while the yield of the sludge increased to ...

Hydrogen gas production from olive mill wastewater by electrohydrolysis with simultaneous COD removal

Diluted olive mill wastewater (OMW) was subjected to direct current (DC) voltages (0.5–4.0 V) for hydrogen gas production with simultaneous chemical oxygen demand (COD) removal by electrohydrolysis. The highest cumulative hydrogen production (3020 ml) and hydrogen yield (2500 ml H 2 g −1 COD) were obtained with 3 V DC voltage while the highest current intensity (80 mA), percent hydrogen (95%) in the gas phase, hydrogen gas formation rate (614 ml d −1), percent COD removal (44%) and energy conversion efficiency (95%) were realized with 2 V. Hydrogen gas production by electrolysis of water was negligible for all voltages. COD removal from OMW with no DC voltage application was usually lower than that obtained with DC power application. Hydrogen gas production by electrohydrolysis of OMW was proven to be a fast and effective method with simultaneous COD removal.

Anaerobic baffled reactor treatment of biodiesel-processing wastewater with high strength of methanol and glycerol: reactor performance and biogas production

AbstractBiodiesel-processing factories employing the alkali-catalyzed transesterification process generate a large amount of wastewater containing high amount of methanol, glycerol, and oil. As such, wastewater has high potential to produce biogas using anaerobic treatment. The aim of this research was to investigate the performance of an anaerobic baffled reactor for organic removal and biogas production from biodiesel wastewater. The effect of different organic loading rates, varying from 0.5 kg m−3 d−1 to 3.0 kg m−3 d−1 of chemical oxygen demand, was determined using three 22 L reactors, each comprising five separate compartments. Wastewater was pretreated with chemical coagulants to partially remove oil prior to experimentation. Results show that the anaerobic baffled reactor operated at 1.5 kg m−3 d−1 of chemical oxygen demand and ten days of hydraulic retention time provided the best removal efficiencies of 99 % of chemical oxygen demand, 100 % of methanol, and 100 % of glycerol. Increasing the organic loading rate over 1.5 kg m−3 d−1 of chemical oxygen demand led to excessive accumulation of volatile fatty acids thereby making the pH drop to a value unfavorable for methanogenesis. The biogas production rate was 12 L d−1 and the methane composition accounted for 64–74 %. Phase-separated characteristics revealed that the highest chemical oxygen demand removal percentage was achieved in the first compartment and the removal efficiency gradually decreased longitudinally. A scanning electron microscopic study indicated that the most predominant group of microorganisms residing on the external surface of the granular sludge was Methanosarcina.

Photo‐Degradation of C.I. Disperse Blue 56 by UV Irradiation Combined with Manganese Minerals

Photo-degradation of C.I. Disperse Blue 56 (DB56) by UV irradiation combined with manganese minerals (UV/MM) was investigated in this paper. Through comparative study with the UV/titanium dioxide (TiO2) process, it was found that the UV/MM method had similar photodegradation efficiency to UV/TiO2 and was slightly more effective in removing the toxicity. In the conditions of DB56 concentration = 400 mg/L, pH = 9.0, manganese minerals dosage = 20 g/L, room temperature (25 degrees C), dissolved oxygen (O2) = 50 L/h, and reaction time = 1 hour, the color and chemical oxygen demand removal percentages were up to approximately 94 and 51%, respectively. The results of this study indicate that UV/MM is an alternative approach that should be explored further in the treatment of dyeing wastewaters.

Impact of electrooxidation on combined physicochemical and membrane treatment processes: Treatment of high strength chemical industry wastewater

Industrial wastewaters containing high concentrations of organics, particularly of recalcitrant nature, demand a unique type of treatment approaches often requiring two or more processes operated in tandem. In this paper, the effectiveness of combined treatment processes viz., coagulation/flocculation (C/F), electrooxidation (EO) and membrane (M) processes for tackling organic load in a segregated chemical industry wastewater is reported. The wastewater is characterized by strong color, high concentrations of salinity, total kjeldhal nitrogen (TKN) and chemical oxygen demand (COD). Three different combined process; i) UF–RO (CP-I); ii) C/F–EO–UF–RO (CP-II) and iii) C/F–EO1–EO2–UF–RO (CP-III) were investigated. The overall COD and TDS removal efficiencies in that order were: CP-I, 73% and 82%; CP-II, 84% and 85%, and CP-III, 93% and 87%. The percent COD and TDS removals at each stage of the combined process were evaluated and the impact of EO process on the overall performance of the process schemes was discussed. It emerged that intermediate level EO process considerably reduces organic load in the effluent, while large part of TDS removal can be attributed to final RO treatment. Thus, the combined treatment processes appear to be promising for obtaining greater efficiency of organic and salinity load removals.

Electrochemical degradation of the Acid Blue 62 dye on a β-PbO2 anode assessed by the response surface methodology

The electrochemical degradation of the anthraquinonic dye Acid Blue 62 in a filter-press reactor on a Ti/Pt/β-PbO2 anode was investigated using the response surface methodology with the variables: current density, pH, [NaCl], and temperature. The system’s modeling was carried out with the charge required for 90% decolorization (Q90) and the chemical oxygen demand removal percentage after a 30 min electrolysis (COD30), with good correlations between predicted and observed values. Best conditions for decolorization were attained in acidic solutions (pH = 4) with medium to high [NaCl] (1.0–2.0 g L−1) and lower temperature due to the prevalent oxidant species HOCl and Cl2. Optimal conditions for COD30 removal were attained at high current densities in pH > 5 solutions with high [NaCl], when the prevalent oxidant species are HOCl and OCl−. The lowest charge per unit volume of the electrolyzed solution necessary for total mineralization was attained at pH 11.

Electrochemical degradation of the reactive red 141 dye on a β-PbO2 anode assessed by the response surface methodology

The electrochemical degradation of the Reactive Red 141 dye using a filter-press reactor with a β-PbO2 anode was investigated through the application of the response surface methodology. The charge required for 90% decolorization (Q90) and the chemical oxygen demand removal percentage after 30 min electrolysis (COD30) were used to model the system. The investigated independent variables were the current density, pH, NaCl concentration, and temperature. Low values of Q90 (0.2-0.3 A h L-1) were obtained at acidic conditions (pH 1-3) and high concentrations of NaCl (1.0-2.0 g L-1), when Cl2 and HOCl are the predominant oxidant species. The best values of COD30 were obtained at high current densities and acidic to neutral conditions (pH 5-7); however, the consequent energy consumption makes the process not economically feasible under these conditions. For strongly acidic solutions, specific energy consumptions associated to Q90 as low as 0.79 kW h m-3 were attained.

Pretreatment of palm oil mill effluent by electrocoagulation and coagulation.

Palm oil mill effluent (POME) is wastewater generated from the palm oil milling process. It is regarded as a highly polluting wastewater as it has a high chemical oxygen demand (COD), and contains high levels of oil and suspended solids. Pretreatment of POME is desirable before a subsequent biological or other treatment. This paper reports a study of POME pretreatment by (1) electrocoagulation and (2) conventional coagulation with Al2(SO4)3. At an optimal condition with a current density of 20 A/m 2 for 5 min at 313 K and pH 5, the percentage of oil, COD, suspended solids, and total solids removal by electrocoagulation were 72%, 64%, 53%, and 43%, respectively. The electrical consumption under this condition was in the order of 0.10 kWh/m 3 . The addition of NaNO3 improved the electrocoagulation, and it may also be beneficial for a subsequent biological treatment. At high current densities and/or long electrocoagulation time, POME treatment produced bubbles, which decrease the efficiency of oil removal. This effect did not occur in conventional coagulation. However, chemical coagulation limits oil removal from POME due to the effect of pH. Overall, electrocoagulation should cause less environmental damage than conventional chemical coagulation by Al2(SO4)3 as it treats POME without the need to add sulphate ions.

CHEMICAL OXIDATION OF TREATED TEXTILE EFFLUENT BY HYDROGEN PEROXIDE AND FENTON PROCESS

In this study the possibility to apply the oxidation process for treating textile effluents, by using hydrogen peroxide and Fenton process was evaluated through determining the color and chemical oxygen demand (COD) removal. The experimental variables studied include the dosages of hydrogen peroxide and iron salts, oxidation time and pH value. The result showed that oxidation process using hydrogen peroxide alone is inefficient in COD and color removal, since only 25 % of COD removal and 21.3 % of color removal were obtained at 100 mg/L H2O2 dosage, pH 5 and 60 minutes contact time. Fenton process is normally used in textile wastewater treatment. However, in Malaysia, it is a new technology applied for treatment of textile effluents. Results obtained from this study showed that Fenton process is efficient in removing color. The color removal reaches a maximum of 90% at reaction time of 30 minutes under the action of the Fenton reagent. Although the COD removal is not very effective using Fenton process, in this study it still complies standard B in Environmental Quality Act, 1974. The percentage of COD removal obtained from this experiment is 67.1 % and the concentration is 85 mg/L under 125 mg/L H2O2 dosage, 3 mg/L Fe 2+ dosage and pH 4. From this study one may conclude that Fenton process for the treatment of textile effluent favors rather the removal of color than of COD.

Photooxidation Degradation of Reactive Brilliant Red K‐2BP in Aqueous Solution by Ultraviolet Radiation/Sodium Hypochlorite

AbstractPhotooxidation degradation of Reactive Brilliant Red K‐2BP (K‐2BP) aqueous solution by ultraviolet irradiation/sodium hypochlorite (UV/NaClO) was investigated. The effects of NaClO dosage, pH, temperature and initial dye concentrations were studied. A possible degradation pathway of K‐2BP was investigated. Acidic or neutral conditions were beneficial to the decolorization of K‐2BP aqueous solution. However, alkaline conditions facilitated chemical oxygen demand (COD) removal. Increasing the solution temperature from 20 to 50°C increased the removal of color and COD. However, at 60°C, the final percentage color and COD removal decreased by approximately 17 and 10%, respectively. Based on the products indentified and theoretical analysis, N=N cleavage and C‐N cleavage were possible initial steps in the degradation of K‐2BP. From the results of this work, we conclude that treatment of UV/NaClO is an efficient method to degrade K‐2BP in aqueous solution.

Periwinkle shell: Based granular activated carbon for treatment of chemical oxygen demand (COD) in industrial wastewater

AbstractThe present investigation was undertaken to compare the adsorption efficiency of a low cost adsorbent, periwinkle shell—based granular activated carbon (PSC) with the adsorption efficiency of the commercial activated carbon (CAC) and a ratio 1:1 mixture of PSC and CAC (PSC/CAC) with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of industrial wastewater. The influence of treatment time, adsorbent dose, pH of the media, agitation speed and adsorbent particle size on the rate of percent COD removal is evaluated. PSC has shown quite effective adsorbent capacity for COD removal with 77.5% efficiency. Though its capacity is slightly lower than that of CAC with 79% efficiency, however the low material cost makes it an attractive option for the treatment of COD. The equilibrium adsorption study can be described by the Linear, Langmuir and Freundlich models. The mechanisms of the rate of adsorption of COD were analysed using the Elovich equation and a pseudo‐second‐order model. The models provided a very high degree of correlation of the experimental adsorption rate data suggesting either model could be used in design applications.

High power generation with simultaneous COD removal using a circulating column microbial fuel cell

AbstractBACKGROUND: A circulating column microbial fuel cell (MFC) with Cu anode and AuCu air cathode was used for power generation and chemical oxygen demand (COD) removal from synthetic wastewater. The column was operated in repeated‐fed batch mode using acclimated anaerobic sludge. The contents of the column MFC were circulated while the feed wastewater was fed to the reactor in fed‐batch mode. Effects of feed COD concentration and COD loading rate on voltage difference, power density and percentage COD removal were investigated.RESULTS: The highest voltage difference (650 mV), power density (40 W m−2) were obtained with a feed COD of 6400 mg L−1, yielding 45% COD removal with a COD loading rate of nearly 90 mg h−1. Low COD loadings (<90 mg h−1) caused substrate limitations, and high loadings (>90 mg h−1) resulted in inhibition of COD removal and power generation. The highest percentage COD removal (50%) was obtained with feed COD content of 10.35 g L−1 or a COD loading rate of 145 mg h−1.CONCLUSION: The power densities obtained with the circulating column MFC were considerably higher than those reported in the literature due to elimination of mass transfer limitations by the high circulation rates, proximity of electrodes and small anode surface area used in this study. Further improvements may be possible with optimization of the operating parameters. Copyright © 2009 Society of Chemical Industry

COD, 2,4,6-trichlorophenol (TCP) and toxicity removal from synthetic wastewater in a rotating perforated-tubes biofilm reactor

Synthetic wastewater containing different concentrations of 2,4,6-trichlorophenol (TCP) was biologically treated using a novel rotating perforated-tubes biofilm reactor (RTBR) for chemical oxygen demand (COD), TCP and toxicity removal. Performance of the reactor was investigated as function of major operating variables such as the feed TCP and COD concentrations and A/ Q (biofilm surface area/feed flow rate) ratio. A Box–Behnken statistical experiment design method was used by considering the feed TCP (0–400 mg L −1), COD (1000–4000 mg L −1) and A/ Q ratio (23–163 m 2 d m −3) as the independent variables while percent TCP, COD, and toxicity removals were the objective functions. The results were correlated with the quadratic model since this was found to be the most suitable one. Response function coefficients were determined by correlating the experimental data with the response function. Percent TCP, COD and toxicity removals estimated from the response functions were in good agreement with the experimental results. TCP, COD and toxicity removals increased with increasing A/ Q ratio and decreasing feed TCP concentrations. Percent toxicity removals were always lower than TCP removals indicating presence or formation of some toxic by products from TCP biodegradation. For the feed TCP of 400 mg L −1, the optimum conditions resulting in maximum COD (99%), TCP (100%) and toxicity (93%) removals were A/ Q ratio of nearly 165 m 2 d m −3 and feed COD of 2985 mg L −1.

Enhanced biological nutrient removal by the alliance of a heterotrophic nitrifying strain with a nitrogen removing ecosystem

Nitrogen removal from synthetic wastewater was investigated in an airlift bioreactor (ALB), augmented with a novel heterotrophic nitrifier Pseudonocardia ammonioxydans H9 T under organic carbon to nitrogen ratios (C org/N) ranging from 0 to 12. Effect of the inoculated strain was also determined on the settling properties and the removal of chemical oxygen demand (COD). Two laboratory scale reactors were set up to achieve a stable nitrifying state under the same physicochemical conditions of hydraulic retention time (HRT), temperature, pH and dissolved oxygen (DO), and operated under the sequencing batch mode. The level of DO was kept at 0.5– 1.5 mg/L by periodic stirring and aeration. Each specific C org/N ratio was continued for duration of 3 weeks. One of the reactors (BR2) was inoculated with P. ammonioxydans H9 T periodically at the start of each C org/N ratio. Sludge volumetric index (SVI) improved with the increasing C org/N ratio, but no significant difference was detected between the two reactors. BR2 showed higher levels of nitrogen removal with the increasing heterotrophic conditions, and the ammonia removal reached to the level of 82%–88%, up to10% higher than that in the control reactor (BR1) at C org/N ratios higher than 6; however, the ammonia removal level in experimental reactor was up to 8% lower than that in control reactor at C org/N ratios lower than 2. The COD removal efficiency progressively increased with the increasing C org/N ratios in both of the reactors. The COD removal percentage up to peak values of 88%–94% in BR2, up to 11% higher than that in BR1 at C org/N ratio higher than 4. The peak values of ammonia and COD removal almost coincided with the highest number (18%–27% to total bacterial number) of the exogenous bacterium in the BR2, detected as colony forming units (CFU). Furthermore, the removal of ammonia and COD in BR2 was closely related to the number of the inoculated strain with a coefficient index ( R 2) up to 0.82 and 0.85 for ammonia and COD, respectively. These results suggest that it was more efficient for both the ammonia and carbon nutrient removals in a reactor inoculated with a heterotrophic nitrifier at high C org/N ratio, inferring that the heterotrophic nitrifers would be practically more available in the treatment of wastewater with high level of ammonia and COD.

Decomposition of dimethyl phthalate in an aqueous solution by ozonation with high silica zeolites and UV radiation

This study investigates the enhanced ozonation of dimethyl phthalate (DMP), which is a pollutant of concern in water environments, with high silica zeolites and ultraviolet (UV) radiation. Semibatch ozonation experiments are performed under various reaction conditions to examine the effects of inlet gas ozone concentration, high silica zeolite dosage, and UV radiation intensity on the decomposition of DMP. The complete removal of DMP can be efficiently achieved via both O 3 and O 3/UV treatments. Note that the presence of high silica zeolites accelerates the decomposition rate of DMP in the O 3 process. On the other hand, the removal efficiencies of both chemical oxygen demand (COD) and total organic carbons (TOC) are significantly enhanced by employing the ozonation combined with UV radiation. The O 3/UV process is also advantageous for the utilization efficiency of fed ozone especially in the late ozonation period. Furthermore, the correlation between the COD removal percentage (%) and the mole ratio of ozone consumed to the DMP treated (mol mol −1) is obtained. The clear-cut removal relationship of the TOC with COD during the ozonation of DMP has also been presented. Consequently, the results evaluate the flexibility of ozonation system associated with high silica zeolites and UV radiation for the removal of DMP and provide the useful information in engineering application.