Initial COD Concentration Research Articles

Electrocoagulation For Oil and Grease Wastewater Treatment Using Iron Electrodes

Batch electrocoagulation (EC) experiments were carried out to evaluate the removal of COD and O&G from wastewater using iron electrodes. The effects of operating parameters such as current intensity, initial COD concentration and contact time on COD and O&G removal efficiency had been investigated. It was found that increasing current intensity increased COD and O&G removal efficiency. Initial COD concentration had a little effect on removal efficiencies. Results showed that the COD removal efficiencies after 60 min. was 80.87 – 84.1 % at current of 1.3 A, 96.1 - 97.9 % at 1.6 A and after 45 min. was 97.9 - 98.6 % at 1.9 A. It can be noticed that after 60 min, for initial COD concentration of1280 mg/l the percentage COD removal was 83.13%, at 11.6 volt and 1.3 ampere, 97.5%, at 14 volt and 1.6 ampere and was 98.6 % at 16.4 volt and 1.9 ampere ,after 45 min .

Thermally activated persulfate treatment and mineralization of a recalcitrant high TDS petrochemical wastewater

Abstract Thermally activated persulfate efficiency for the treatment of a recalcitrant high TDS wastewater was investigated. The specific character of studied wastewater was high TDS content of around 23820 mg/L and BOD5/COD ratio of 0.07. Effective operational parameters including initial pH values of 3–9, reaction temperature of 40–80°C and persulfate concentrations of 0.5–5 g/L for COD removal were investigated in batch mode experiments. Removal efficiency was pH and temperature dependent. The COD and TOC removal of 94.3% and 82.8% were obtained at persulfate concentration of 4 g/L, initial pH value of 5 and temperature of 70°C after 180 min for initial COD concentration of 1410 mg/L. The pseudo first-order kinetic model was best fitted with COD removal (R2 = 0.94).

Assessment of effective parameters in landfill leachate treatment and optimization of the process using neural network, genetic algorithm and response surface methodology

Abstract In this paper, the Fenton process was found to be an effective technique to treat leachates when the drawbacks of this process were minimized by choosing proper catalyst, considering effective parameters and introducing optimum conditions. Analytic hierarchy process (AHP) was used to select the favorable catalyst between FeSO4 and FeCl2. Meanwhile, central composite design was used for test design of the experiments along with response surface methodology (RSM) and artificial neural network (ANN) for modeling. The effective variables included pH, [ H 2 O 2 ] / [ Fe 2+ ] , Fe 2+ dosage and initial COD concentration while removal COD, sludge to iron ration (SIR) and organic removal to sludge ratio (ORSR) were considered as targets. For all three targets, the effective factors were considered using sensitivity analysis. Finally, response surface methodology and genetic algorithm (GA) were used for optimization of the process. According to AHP sensitivity analysis results, priority percentage for FeCl2 and FeSO4 were 64% and 36%, respectively. Comparing RSM and ANN, it was found that ANN provided higher prediction ability while both models were statistically adequate (with R 2 > 0 .90 ) . The effective factors for COD removal, SIR and ORSR were respectively as follows: Fe 2+ dosage, pH and [ H 2 O 2 ] / [ Fe 2+ ] . The main focus of optimization was to achieve high removal efficiencies for COD when generated sludge is still low. Hence, results from RSM and GA indicated that both methods proposed approximately similar operational conditions. In the end, a practical formula was proposed for BOD5/COD ratio enhancement for each leachate.

Reuse of Ferric Sludge by Ferrous Sulfide in the Fenton Process for Nonylphenol Ethoxylates Wastewater Treatment

In this paper, Fenton process was determined to be an effective technique to treat the refractory Nonylphenol ethoxylates (NPEOs) wastewater. The COD removal efficien-cies above 89% were obtained when the initial COD concentration was 12000mg/L. However, A large number of ferric sludge (SS=8.724g/L) would be produced after the Fenton oxidation of the wastewater and must be disposed appropriately. A novel process for Fenton sludge reused by low-cost ferrous sulfide (FeS) was also investi-gated. Experimental results show that the Fenton sludge could be reduced to produce a certain amount of Fe2+ in the acidic mixed liquor by ferrous sulfide. This mixed liquor from Fenton sludge could be used as the new catalyst in the Fenton process and was also highly effective for the NPEOs wastewater treatment. The residual ferrous sulfide from the mixed liquor could be used for the next batch of the reaction

Kinetic evaluation on the degradation process of anaerobic digestion fed with piggery wastewater at different OLRs

A kinetic model was developed to predict the degradation of organic matters,biogas production and the intermediate products considering the inhibition of pH, H2 and H2S. The sensitivity of COD, acetate, butyrate and propionate to the kinetic parameters and the influence of pH, H2 and H2S were also analysed. The results showed that the model could be well used to predict the anaerobic process. The maximum kinetic constants corresponding to the degradation of organic matters appeared at 5.3kg COD/m3. From the degradation kinetic values of acetate, butyrate and propionate, it could be seen that the order of VFAs converted into methane was propionate>butyrate>acetate; From the degradation kinetic value of COD, it could be seen that the order of COD converted into VFAs was acetate>butyrate>propionate. With the increase of OLR, there were inhibitions existing in the anaerobic digester which showed up in the increase of concentration of H2 and H2S. Through the sensitivity analysis, the initial concentration of COD was the most sensitive parameter which made great influence on the anaerobic digestion process.

Boron-doped diamond oxidation of amoxicillin pharmaceutical formulation: Statistical evaluation of operating parameters, reaction pathways and antibacterial activity

The electrochemical oxidation of a commercial amoxicillin formulation over a boron-doped diamond (BDD) anode was investigated. The effect of initial COD concentration (1–2 g/L), current density (30–50 mA/cm2), treatment time (15–90 min), initial pH (3–9) and electrolyte concentration (2–4 g/L NaCl) on COD removal was assessed through a factorial design methodology. For the range of conditions in question, the first three single effects, as well as the interaction between COD and time were the most important ones in terms of mass of COD removed.Liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) was employed to identify major transformation by-products (TBPs); thirteen compounds were detected as TBPs of AMX electrochemical degradation, while several others appear in the original formulation. AMX degradation occurs though the following pathways: (i) hydroxylation mainly in the benzoic ring, (ii) opening of β-lactam ring followed by decarboxylation, hydroxylation and re-arrangement, and (iii) bond cleavage between the carbons of amino and amide groups. Furthermore, the process is accompanied by the release of several ions, i.e. nitrate, sulfate and ammonium.The antibiotic activity of AMX up to 1000 mg/L was tested against Klebsiella pneumoniae and Enterococcus faecalis reference strains; both bacteria are completely inactivated at this concentration but the activity is reduced substantially at lower concentrations. Oxidized samples still exhibit some antibacterial activity (50–60%) which is due to TBPs and active chlorine species present in the liquid phase. The latter are generated from chloride ions and enhance considerably AMX degradation rates.

Isolation and screening of microalgae from agro-industrial wastewater (POME) for biomass and biodiesel sources

Indigenous microalgae (KR349061) were isolated from the agro-industrial wastewater and screened in order to determine their potential for biomass and biodiesel sources. Bold’s Basal Medium was used to isolate the colonies from sample. The nutrient contents were altered in order to optimize the growth of the microalgae. The isolates were identified based on the morphology and microscopic appearance of the isolated colonies. It was seen that the isolates comprised of several common green microalgae and cyanobacteria, among which the ideal candidate was selected and further investigated. Lipid content was determined for the strains that showed rapid growth. The results showed that Chlamydomonas incerta achieved highest lipid content of biomass (42.6%) after 2 d, also highest lipid productivity of 0.197 mg/L/d was observed when the initial COD concentration was 500 mg/L. C. incerta also showed higher growth rate and higher amount of lipid was examined for its potential as sustainable biodiesel feedstock along with its higher biomass yield.

A hybrid system comprising an aerobic biological process and electrochemical oxidation for the treatment of black table olive processing wastewaters

In this work table olive processing wastewaters (TOPW) were treated by aerobic biological processes using indigenous microorganisms originating from TOPW, as well as the combination of two successive steps, i.e. aerobic biological treatment followed by electrochemical oxidation over a boron-doped diamond anode.In the single aerobic biological processes, experiments in suspended and attached growth reactors (trickling filters) were carried out using different TOPW feed concentrations of 5500 ± 350, 7500 ± 650 and 15,000 ± 1050 mg dissolved COD L−1. Two different operating modes were used to investigate the optimum performance of the filter, i.e. batch and SBR with recirculation. The latter mode with recirculation of 0.5 L min−1 led to high removal rates of dissolved COD and total phenolic compounds, up to 96.5% and 64.5%, respectively, for the initial COD concentration of 7500 mg dissolved COD L−1.Depending on the type and operating conditions of the bioreactors, residual COD ranged between a few hundred and a few thousand mg L−1, while decolorization could not be achieved even under the most favorable conditions. A biologically treated effluent with residual dissolved COD of 5100 mg L−1 was completely mineralized and decolorized at 187.5 mA cm−2 applied current density; complete removal of COD, color and total phenolic compounds was achieved in 180–240 min, 30–60 min and 30 min of electrochemical oxidation, respectively. Lower treatment times and current densities were needed to polish effluents with lower organic loads.

Treatment of highly concentrated tannery wastewater using electrocoagulation: Influence of the quality of aluminium used for the electrode

This paper deals with the ability of electrocoagulation (EC) to remove simultaneously COD and chromium from a real chrome tanning wastewater in a batch stirred electro-coagulation cell provided with two aluminium-based electrodes (aluminium/copper/magnesium alloy and pure aluminium). Effects of operating time, current density and initial concentration of Cr(III) and COD have been investigated. The concentrations of pollutants have been successfully reduced to environmentally acceptable levels even if the concentrated effluent requires a long time of treatment of around 6h with a 400A/m2 current density. The aluminium alloy was found to be more efficient than pure aluminium for removal of COD and chromium. Dilution of the waste has been tested for treatment: high abatement levels could be obtained with shorter time of treatment and lower current densities. Energy consumption of the electrocoagulation process was also discussed. The dilution by half of the concentrated waste leads to a higher abatement performance of both COD and chromium with the best energy efficiency.

Methodology to determine the specific hydrogenic activity (SHA) of waste sludges

Production of hydrogen is influenced by the pH, the concentration of organic matter, and the concentration of sludge. A short-term test is presented in which the specific hydrogenic activity of a waste sludge is calculated in order to quantify its hydrogen production capacity. To determine the ideal conditions for the measurement of SHA was used glucose in concentrations of 1000; 2000; 4000; 8000; 12,000; 16,000; and 20,000 mg O2 L−1; sludge in concentrations of 1250; 2500; 5000; and 7500 mg TVS L−1; and pH adjustments of 5.0; 5.5; 6.0; and 6.5. Given the initial concentration of soluble COD of 12,000 mg O2 L−1, sludge concentration of 2500 mg TVS L−1, and pH of 6.0, the highest SHA obtained was 483 mLH2 g TVS−1 h−1. As to volumetric measurements, given the initial concentration of organic matter of 8000 mg L−1, biomass concentration of 5.000 mg TVS L−1, and pH of 5.5, the volume of produced hydrogen per mass of soluble COD added reached a maximum of 38 mL gCOD−1.

A comparative study on the efficiency of ozonation and coagulation–flocculation as pretreatment to activated carbon adsorption of biologically stabilized landfill leachate

The present work investigates the potential of coagulation–flocculation and ozonation to pretreat biologically stabilized landfill leachate before granular activated carbon (GAC) adsorption. Both iron (III) chloride (FeCl3) and polyaluminium chloride (PACl) are investigated as coagulants. Better organic matter removal is observed when leachate was treated with FeCl3. At a dose of 1mg FeCl3/mg CODo (CODo: initial COD content), the COD and α254 removal was 66% and 88%, respectively. Dosing 1mg PACl/mg CODo resulted in 44% COD and 72% α254 removal. The settle-ability of sludge generated by PACl leveled off at 252mL/g, while a better settle-ability of 154mL/g was obtained for FeCl3 after dosing 1mg coagulant/mg CODo. For ozonation, the percentage of COD and α254 removal increased as the initial COD concentration decreased. Respectively 44% COD and 77% α254 removal was observed at 112mg COD/L compared to 5% COD and 26% α254 removal at 1846mg COD/L. Subsequent activated carbon adsorption of ozonated, coagulated and untreated leachate resulted in 77%, 53% and 8% total COD removal after treatment of 6 bed volumes. Clearly showing the benefit of treating the leachate before GAC adsorption. Mathematical modeling of the experimental GAC adsorption data with Thomas and Yoon–Nelson models show that ozonation increases the adsorption capacity and breakthrough time of GAC by a factor of 2.5 compared to coagulation–flocculation.

Microbial reduction and precipitation of vanadium (V) in groundwater by immobilized mixed anaerobic culture

Vanadium is an important contaminant impacted by natural and industrial activities. Vanadium (V) reduction efficiency as high as 87.0% was achieved by employing immobilized mixed anaerobic sludge as inoculated seed within 12h operation, while V(IV) was the main reduction product which precipitated instantly. Increasing initial V(V) concentration resulted in the decrease of V(V) removal efficiency, while this index increased first and then decreased with the increase of initial COD concentration, pH and conductivity. High-throughput 16S rRNA gene pyrosequencing analysis indicated the decreased microbial diversity. V(V) reduction was realized through dissimilatory reduction process by significantly enhanced Lactococcus and Enterobacter with oxidation of lactic and acetic acids from fermentative microorganisms such as the enriched Paludibacter and the newly appeared Acetobacterium, Oscillibacter. This study is helpful to detect new functional species for V(V) reduction and constitutes a step ahead in developing in situ bioremediations of vanadium contamination.

Studies on various operating parameters for the removal of COD from pulp and paper industry using electrocoagulation process

This study describes a batch electrocoagulation process for treating pulp and paper industry wastewater using iron plates. The effect of various operating parameters such current density, initial effluent pH, initial COD concentration, electrode combination and interelectrode distance on the removal of percentage COD and power consumption were investigated. The experimental results showed that 85% COD removal with 5.16 kWh/m3 of power consumption was observed for initial COD concentration of 2,500 ppm with current density of 0.40 A/dm2, initial effluent pH of 7.0 with interelectrode distance 1 cm at the end of the 120 min of operation. It was observed that, an increase in current density, decrease in the effluent COD concentration, Fe/Fe electrode combination, and decrease in interelectrode distance improved the COD removal efficiency. Optimum initial effluent pH for highest COD removal was 7.0. Furthermore in this investigation, extraction of lignin from the pulp and paper industrial effluent also carried out and analyzed by FT-IR system.

Feasibility study on the application of membrane distillation process to treat high strength wastewater

【In this study, we applied a membrane distillation process to investigate a feasibility of treating a wastewater with high concentration of organic matters including nitrogen and phosphorus. The laboratory scale experiment was performed by using a hydrophobic PVDF membrane with the pore size of $0.22{\mu}m$ and porosity of 75%. The installation was direct contact type where the temperature difference between a feed and permeate side was controlled to have a range from 20 to $60^{\circ}C$ . We observed a flux variation and a concentration changes of COD, $PO{_4}^{3-}$ -P, $NH_4{^+}$ -N and conductivity of feed side as well as permeate side with various temperature differences (20 to $60^{\circ}C$ ), cross flow velocities (0.09 to 0.27 m/s) through the module, and pH (6.6 to 12.0) of the feed that has the initial concentration of COD about 1,000 mg/L, total nitrogen 390 mg/L, total phosphorus 10 mg/L, conductivity of $7,000{\mu}s/cm$ . The results showed that the average flux was ranged from 4 to $40L/m^2/hr$ which was almost similar with the flux of NaCl and deionized water used as a feed solution. The lowest flux was obtained at the operating condition with the temperature difference of $20^{\circ}C$ and cross flow velocity of 0.09 m/s while the highest one was measured with $60^{\circ}C$ and 0.27 m/s. Above 99% of COD and $PO{_4}^{3-}$ -P in the feed could be rejected regardless of an operating condition. However, the removal rate of ammonium nitrogen was varied from 64 to 99% depending on the pH of feed solution.】

Pilot-scale treatment of pharmaceutical berberine wastewater by Fenton oxidation

Fenton oxidation was used to treat the berberine finished mother liquor wastewater in pilot scale. To evaluate berberine and COD removal efficiency, the main factors, including pH, H2O2 dosage, Fe2+/H2O2 mass ratio and the water flow (Q), were optimized using response surface methodology (RSM). The results showed that under the optimal conditions, pH 3, H2O2/COD molar ratio of 1.25, Fe2+/H2O2 molar ratio of 0.1, Q 100 L/h [with hydraulic retention time (HRT) of 2.5 h], the COD and berberine removal efficiencies were 35.6 and 91.4 % at initial COD concentration of 4061 mg/L and berberine concentration of 709 mg/L, respectively. The (BOD5)/(COD) ratio (B/C) of the wastewater increased from 0 to 0.3, indicating significantly improved biodegradability of wastewater.

Degradation Kinetics of Photoelectrocatalysis on Landfill Leachate Using Codoped TiO2/Ti Photoelectrodes

The photoelectrocatalytic (PEC) oxidation degradation of landfill leachate rejected by reverse osmosis (RO) using a Cu/N codoped TiO2/Ti photoelectrode was kinetically investigated in terms of COD concentration. The key factors affecting the reaction rate of PEC oxidation and the removal efficiency of COD concentration were studied, including the COD concentration of landfill leachate, potential bias applied, pH value of landfill leachate, and the reaction temperature of photoelectrocatalytic reactor. The apparent kinetic model was applied to describe the photoelectrocatalysis reaction. The results showed that the kinetic equation for photoelectrocatalytic oxidation of landfill leachate was fitting well with the experimental data (R2 = 0.967~0.998), with average activation energy Ea = 6.35 × 104 J·mol−1. It was found that there was an optimal bias voltage of 20 V and low pH value was favorable for COD removal in landfill leachate. The reaction order of initial COD concentration (1.326) is higher than that of potential bias (1.102) and pH value (0.074), which indicates that the reaction rate can be controlled efficiently through adjusted initial concentration. The experiments demonstrated that potential bias would approach its statured value with increasing potential bias.

Preliminary Study of Photosynthetic Bacteria Treating Hydrothermal Liquefaction Wastewater

Post hydrothermal liquefaction wastewater (PHWW) was generated during biocrude oil production. It contains lots of carbon, nitrogen and phosphorous elements, which can cause environmental pollution and resource waste. Using photosynthetic bacteria (PSB) to treat this kind of wastewater can realize pollutants elimination and resource recovery. In this work, the feasibility of using PSB to treat PHWW was firstly investigated, and the treatment conditions were optimized. Results showed that the PSB can effectively degrade PHWW. The optimal initial COD concentration, inoculum size and light intensity for PSB to treat PHWW were 6000-10000 mg/L, 50 mg/L and 1000-3500 lux, respectively. With the initial COD concentration of 9000 mg/L, inoculum size of 50 mg/L and light intensity of 1000 lux, the COD, NH3-N, TP removal and biomass production reached to 71%, 90%, 47.2% and 773 mg/L, respectively. This showed that using PSB to treat PHWW can be an alternative method for PHWW nutrients recovery and pollutant treatment.

Photocatalytic degradation of Tire Cord manufacturing wastewater using an immobilized nanoTiO2 photocatalytic reactor

In this study, an immobilized nanoTiO2 photocatalyst was developed for the degradation of Tire Cord manufacturing wastewater with low BOD5/COD ratio (0.1–0.2). The interactive effects of three numerical independent factors (initial COD concentration, initial pH, and reaction time) on the process performance were studied. The process performance was evaluated by monitoring three process responses including COD removal efficiency, specific COD removal rate and BOD5/COD ratio after treatment. The process was modeled and analyzed using response surface methodology. Maximum COD removal efficiency and BOD5/COD ratio were modeled to be 38% and 0.5, respectively, at CODin of 350 mg/l and initial pH of 11. The photocatalytic process induced by O3 and O3/H2O2 showed a remarkable improvement in the process responses studied. Photocatalytic process with sequence regeneration with ozonation could achieve higher COD removal efficiency and BOD5/COD ratio relative to that obtained from regeneration by aeration.

Treatment of linear alkyl benzene (LAB) production wastewater in an integrated photocatalysis and biological treatment process

The initial biodegradability of the organic matter present in the linear alkyl benzene (LAB) production wastewater estimated as the BOD5/COD was low 0.12. To decrease the time and operational cost necessary for the mineralization of LAB wastewater, an optimum operation condition of the integrated photocatalysis and biological treatment was investigated. An immobilized TiO2 photocatalytic reactor under UVA (365nm) irradiation and a continuous feeding intermittent discharge (CFID) bioreactor were employed in this study. The effects of initial COD concentration, reaction time and initial pH on COD removal efficiency and BOD5/COD ratio were studied in photocatalytic reactor. The maximum COD removal efficiency and BOD5/COD ratio for the photocatalytic reaction alone were found 37% and 0.45, respectively at initial COD 400mg/l and pH of 3 after 240min. The remaining COD concentration after the photocatalytic reaction (after 120min) was about 280mg/l with BOD5/COD=0.4 which was used as feed for the CFID bioreactor. The bioreactor was operated at hydraulic retention time (HRT) 12h and mixed liquor volatile suspended solid (MLVSS) 5000mg/l a corresponding to organic loading rate (OLR) and food to microorganism (F/M) ratio of 0.74g COD/ld and 0.148d−1, respectively. The integrated system showed a good performance with about 80% total COD removal efficiency. It is concluded that this combination (PCR–CFID) was a good strategy to achieve a high COD removal efficiency in a short period of time and lower cost for such a low biodegradable wastewater.

Ozonation of an effluent of oil refineries for COD and sulfide removal

Wastewater treatment for water reuse is one of the main concerns in oil refineries since it can lead to high economic and environmental benefits. This paper deals with treatment of an effluents of Shiraz oil refinery called Slops reservoirs effluent by means of ozone as an advanced oxidation agent. For this purpose, ozone is well dispersed at a dose of 5 g/h and effective transferred concentration of 2335 mg/L using a gas distributor into a semi-batch reactor containing 1 L of the wastewater. In order to determine the efficiency of the treatment, the removal percentage of COD and sulfide was selected as studying parameters. The effects of initial sulfide and COD concentrations, presence of UV light, initial pH, and temperature were investigated on the studying parameters. According to the obtained results, the highest removal rate occurred during the first 30 min reaction time. Also it has been observed that, for the initial sulfide concentration of 350 mg/L and the initial COD concentration of 975 mg/L, the ozonation process after 45 min resulted in 100% sulfide removal under optimum initial pH of 9.4 and optimum temperature of 15°C and presence of UV light. While at the same conditions, 92% of COD removal has been achieved for 60 min ozonation. Also, water turbidity level significantly reduced during the treatment.