Initial Chemical Oxygen Demand Concentration Research Articles

Comparative study between activated sludge process (ASP) and moving bed bioreactor (MBBR) for treating composite chrome tannery wastewater

The comparative performance of a laboratory-scale MBBR and an ASP system has been studied in batch mode of operation for the removal of organic carbon from composite chrome tannery wastewater. The reactors were operated under initial MLSS concentration 2000-2500 mg/L for both the systems and 20g/L of PVC rings was introduced as moving bio-carrier in the MBBR. Corrugated PVC ring of diameter 12.5 and height 15 mm was used for providing attached surface in the present batch study. Total batch period was taken maximum 7.5 hrs and the influent chemical oxygen demand (COD) was provided in the range of 100 ± 50mg/L to 500 ± 50 mg/L. It was observed that 85-90% of COD removal could be obtained at the end of 7.5 hrs. in the MBBR system for initial COD concentration of 150-250 mg/L as compared to ASP reactor, which showed only 60-70% removal. However, in case of MBBR system COD removal efficiency marginally decreased with higher initial COD concentration like the ASP reactor. A sharp inhibition was also observed in the ASP reactor when initial concentration increased to the range of 300-500 mg/L. Apart from that a steady growth of attached biomass was noticed on the media surface of the MBBR system.

Potential of novel wastewater treatment system featuring microbial fuel cell to generate electricity and remove pollutants

A new design of a pilot-scale constructed wetland managed with a membraneless microbial fuel cell (CW-MFC) was tested here to assess its potential to generate electricity and remove pollutants under different operating conditions. In the CW-MFC, the cathode was half vertically inserted into the matrixes of constructed wetland (CW) and half exposed to the air to benefit from both surrounding wetland plant growth and the atmosphere thereby ensured its demand for oxygen as well. A series of periodic and regular voltages were obtained after four cycles of wastewater treatment in the batch flow experiment with influent chemical oxygen demand (COD) 228mg/L. The maximum voltage output (0.588±0.01V) for these four cycles lasted for 34, 35, 37 and 42h, respectively. A steady set of maximum voltage (0.529V) outputted over a wetland operation period of 15 days in the continuous flow experiment with the hydraulic retention time of 10h. The maximum power density was 9.6mW/m2 and the maximum current density was 55mA/m2 according to the cathode area. Under batch flow mode, the COD removal rate was 91.2% and the outstanding removal rates of total nitrogen, ammonium nitrogen and total phosphorus appeared ranging between 95% and 99% while electricity generated from the CW-MFC. The influence of temperature on electricity generation was investigated and the result showed that the maximum voltage output values were inversely relative to the lasting duration of the voltage. Influent COD concentrations also affected the highest voltage output and continuous electricity generation of CW-MFC, and the higher initial COD concentration elevated the electricity generation. Thus, the new CW-MFC has high potentials not only of bioelectricity generation but also of the high pollutant removal rates.

Sugar and volatile fatty acids dynamic during anaerobic treatment of olive mill wastewater

ABSTRACTBiogas production has been the main route used to exploit olive mill wastewater (OMW), after pretreatment and/or in combination with other effluents, but more recently the production of chemicals and biopolymers by biotechnological routes has deserved increasing attention by the scientific community. The present paper aims to explore the potential of fresh OMW as a source of volatile fatty acids (VFAs) and biogas. The time profile of VFAs production and the corresponding sugar consumption was followed by high-performance liquid chromatography, in batch anaerobic assays. The experimental results have revealed the very high potential of the OMW for the production of VFAs, mainly due to the high sugar concentration in the effluent (37.8 g/L) and its complete conversion into VFAs, in a time period of 2–3 days. The most abundant VFAs were acetic (48–50%), n-butanoic (12–27%), iso-pentanoic (12–14%) and propanoic (5–13%). The ratio of VFA containing even and odd carbon chains increased with the reduction in the initial chemical oxygen demand concentration of the samples used in the experiments. The conversion of the VFAs to biogas was inhibited at concentrations of 3.5 g/L of VFAs.

Optimization of coagulation–flocculation process for combined sewer overflow wastewater treatment using response surface methodology

A different type of combined sewer overflow (CSO) problem in dry weather, with characteristic of high organic pollutant loads and wide variations, has been becoming one of the most serious urban river pollution problems in China. The performance of coagulation–flocculation process in this type of CSO wastewater treatment was investigated in this study, using polyaluminum ferric chloride sulfate (PAFCS) as coagulant. A 23 full-factorial central composite design and response surface methodology were applied to evaluate the effects and interactions for the chemical oxygen demand (COD) removal efficiency by three factors including initial COD concentration, initial suspended solid concentration, and coagulant dosage. A quadratic model was obtained and the analysis of variance results indicated clearly that experimental data could fit the equation well with a R2 of 95.15%. There is a significant interaction between the initial COD concentration and coagulant dosage for COD removal efficiency. The experimental data and model predictions agreed well. The quadratic model was demonstrated to be an appropriate approach in prediction of the coagulant dosage or COD removal efficiency in this type CSO wastewater treatment using coagulation–flocculation process.

Treatment of landfill leachate using immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles

This study investigated the performance of immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles in the treatment of raw landfill leachate with a very low biodegradability ratio (BOD5/COD) of 0.09. The effects of various operating parameters, such as initial chemical oxygen demand (COD) concentration, pH, temperature, and biosorbent dosage, were evaluated with respect to the removal efficiency of total organic carbon (TOC) and ammonia nitrogen (NH3–N). For the immobilized biosorbents, an optimum pH of 6.0 for TOC and 7.0 for NH3–N were found suitable for TOC and NH3–N removal at temperature of 37°C, respectively. The most superior removal efficiencies of TOC and NH3–N of landfill leachate were over 75% and 74% in 72h at an initial COD concentration of 200mgL−1, respectively. In addition, heavy metals were partly removed by the immobilized biosorbents during the process of landfill leachate treatment. The species and mass percentage of organic compounds in landfill leachate after the treatment were found to have considerably declined according to the gas chromatography coupled with mass spectrometry (GC–MS) system. These results indicate that the immobilized P. chrysosporium loaded with nitrogen-doped TiO2 nanoparticles could be a convenient and efficient method for the treatment of landfill leachate.

Use of Bacillus consortium in waste digestion and pathogen control in shrimp aquaculture

The wastewater from shrimp aquaculture industry contains high concentration of nitrogen and carbon. The use of microorganisms to remove nitrogen and carbon from shrimp aquaculture wastewater was investigated. A consortium of Bacillus species was used to enhance the performance of a sequencing batch reactor (SBR) for the treatment of shrimp aquaculture wastewater. An SBR is a variation of the activated sludge biological treatment process. This process accomplishes equalization, aeration, and clarification in a timed sequence in a single reactor basin to take the place of multiple tanks in conventional treatment systems. This is achieved through sequencing stages, which includes fill, react, settle, decant, and idle. The shrimp wastewater initially contained a high concentration of carbon and nitrogen. By operating the reactor sequentially, viz, aerobic, anaerobic, and aerobic modes, nitrification and denitrification were achieved as well as removal of carbon. Specifically, the initial chemical oxygen demand concentration of 1996 mg/L was reduced to 4 mg/L within eight days of reactor operation. Ammonia in the wastewater was nitrified within three days. The denitrification of nitrate was achieved by the anaerobic process and more than 99% removal of nitrogen was observed. The addition of Bacillus consortium also controlled the growth of shrimp pathogen, Vibrio harveyi in the wastewater.

Performance of Combined Ozone and Fenton Process in Treating Different Leachate Concentrations

Background : Leachate pollution is one of the main problems in landfill- ing, and researchers have yet to find an effective solution to this problem. The tech- nology that can be used may differ based on the type of leachate produced. The most problematic parameters in leachate are chemical oxygen demand (COD), ammonia, and color. Material and Methods : The performance of ozone/Fenton in advanced oxidation process (AOPs) in treating stabilized leachate was investigated. The opti- mal dosages of Fenton reagent (0.05 mol L-1 (1,700 mg/L) H2O2 and 0.05 mol L-1 (2,800 mg/L) Fe2+) were determined through preliminary experiments and added to the leachate sample into the ozone reactor. The input ozone concentration in a 2 L leachate sample was 80 g/m3 NTP ± 0.5% under 1 bar pressure. The initial COD varied between 250 and 2360 mg/L, color varied between 470 Pt. Co. to 4530 Pt. Co., and NH3-N varied between 150 mg/l to 1170 mg/L. Results : the maximum re- moval efficiency was 87% for COD, 100% for color, and 22% for NH3-N at lowest leachate concentration. The lowest amount of consumed ozone (1.28 KgO3/ Kg COD) corresponded to the initial concentration of COD (2000 mg/L) with 60% re- moval of COD during 1 h ozonation. The biodegradability (BOD5/COD) improved from 0.09 in raw leachate to 0.27 at 500 mg/L initial COD. Conclusion : The current study revealed that the use of ozone/Fenton (O3/H2O2/Fe2+) in AOPs is more effi- cient in removing COD and color in low concentrations of semi-aerobic stabilized leachate and in improving biodegradability.

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.

Continuous electrocoagulation of cheese whey wastewater: An application of Response Surface Methodology

In this study, treatment of cheese whey wastewater was performed using a uniquely-designed continuous electrocoagulation reactor, not previously encountered in the literature. An iron horizontal rotating screw type anode was used in the continuous mode. An empirical model, in terms of effective operational factors, such as current density (40, 50, 60 mA/cm2), pH (3, 5, 7) and retention time (20, 40, 60 min), was developed through Response Surface Methodology. An optimal region characterized by low values of Chemical Oxygen Demand (COD) was determined. As a result of experiments, a linear effect in the removal efficiency of COD was obtained for current density and retention time, while the initial pH of the wastewater was found to have a quadratic effect in the removal efficiency of COD. The best fit nonlinear mathematical model, with a coefficient of determination value (R2) of 85%, was defined. An initial COD concentration of 15.500 mg/L was reduced to 2112 mg/L with a removal efficiency of 86.4%. In conclusion, it can be said that electrocoagulation was successfully applied for the treatment of cheese whey wastewater.

Process modeling and evaluation of petroleum refinery wastewater treatment through response surface methodology and artificial neural network in a photocatalytic reactor using poly ethyleneimine (PEI)/titania (TiO2) multilayer film on quartz tube

In this study, poly ethyleneimine (PEI)/Titania (TiO2) multilayer film on quartz tubes have been successfully fabricated via a layer-by-layer (LbL) self-assembly method. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area analysis were carried out for characterization of the layers on quartz tube. The SEM pictures showed that the film surface is smooth and uniform. The BET characterization verified the formation of multilayer thin film. The photocatalytic activity of the PEI/TiO2 multilayer deposited on the quartz tubes was evaluated in the treatment of raw petroleum refinery wastewater (PRW) under UV light irradiation in three annular photocatalytic reactors. This study examined the impact of initial chemical oxygen demand (COD) concentration, H2O2 concentration, pH and reaction time on the PRW treatment and the results were used to generate both a response surface methodology (RSM) model and an artificial neural network (ANN) model. Maximum COD removal (98 %) was achieved at the optimum conditions (initial COD concentration of 300 mg/l, hydrogen peroxide concentration of 8.8 mM, pH of 5 and reaction time of 120 min). A comparison between the model results and experimental data gave a high correlation coefficient (R ANN 2 = 0.9632, R RSM 2 = 0.943) and showed that two models were able to predict COD removal from PRW by PEI/TiO2/UV process. However, ANN model was superior to RSM model with higher value of coefficient of determination (0.9632ANN > 0.94RSM) and the lower root mean square error (RMSE) (3.377AAN < 3.569RSM). The average percentage error for ANN and RSM models was 0.18 and 0.73, respectively, indicating the superiority of ANN in capturing the nonlinear behavior of the system. It was clear that the best networks were able to predict the experimental responses more accurately than the multiple regression analysis.

Bioelectricity generation from coconut husk retting wastewater in fed batch operating microbial fuel cell by phenol degrading microorganism

Dual chamber microbial fuel cell (MFC) operated at fed batch mode for the treatment of retting wastewater has potently achieved both current generation and phenol removal. Hydraulic retention time (HRT) of the reactor was varied from 40 days to 10 days. COD (chemical oxygen demand) removal was 91% at 40 days HRT, with an initial COD concentration of 530 ± 50 g m−3. Retting wastewater with an initial phenol concentration of 320 ± 60 g m−3 procured a highest phenol removal of 93% at 40 days HRT of the microbial fuel cell. Maximum power density of 362 mW m−2 was achieved using retting wastewater at HRT of 20 days with an internal resistance of 150 Ω in a dual chambered MFC. The bacterial strains in anode region, reported to be responsible for potential phenol removal, were identified as Ochrobactrum sp. RA1 (KJ408266), Ochrobactrum sp. RA2 (KJ408267) and Pesudomonas aeruginosa RA3 (KJ408268) using phylogenetic analysis. The study reveals that, dual chambered MFC effectively removed the phenol from retting wastewater along with power generation.

Influence of applied voltage and COD on the bioelectrochemical degradation of organic matter

Organic matter degradation was examined in an air cathode bioelectrochemical system (BES) operated in a fed-batch mode operation. The organic matter degradation rate in the air cathode BES was significantly affected by the initial concentration of organic matter with a chemical oxygen demand (COD) ranging from 25 to 600 mg/L, and by the applied voltage of 100 and 300 mV. When the initial COD concentration was less than 100 mg/L, the substrate affinity to bacteria at an applied voltage of 300 mV was slightly higher than that at 100 mV, but the substrate degradation potential that was evaluated by the ratio of maximum substrate degradation rate to saturation constant did not vary at 100 and 300 mV applied voltages. For initial COD concentrations higher than 300 mg/L, the substrate degradation potential at an applied voltage of 100 mV was higher than that at 300 mV. The anode and cathode potentials in the BES were affected by both the applied voltage and initial COD concentration, but the effect of applied voltage on the potential was increasingly important with decrease in COD concentration. The coulomb efficiency at an applied voltage of 100 mV was higher than that at 300 mV, but decreased with increase in initial COD concentration in the BES. The air cathode BES with applied voltage is an advanced wastewater treatment system for organic pollutants.

Carbon attrition during continuous electrolysis in carbon bed based three-phase three-dimensional electrode reactor: Treatment of recalcitrant chemical industry wastewater

The performance of a carbon bed based three-dimensional electrode reactor (TDR) in terms of chemical oxygen demand (COD) removal from recalcitrant chemical industry wastewater was assessed. The pH and temperature changes in the TDR during electrolysis were correlated with COD removal efficiency. The carbon weight loss and particle size reduction due to erosion of carbon particles during electrolysis was also examined. Two cases of experiments were performed; ‘case I’ employed a high surface area Indcarb-60 GAC, whereas a low surface area carbon (GAC-10) was used for ‘case II’. The other experimental variables are, initial COD concentration, hydraulic retention time (HRT) and the duration of electrolysis. The experimental results showed that TDR could remove COD efficiently (49±7%). The apparent Faradic efficiency and specific electrical energy consumption were estimated to be 3.42% and 6.59kWhkg−1 COD for case I and 0.78% and 28.65kWhkg−1 COD for case II. Use of high surface area carbon in TDR is inferred to be beneficial. However, the GAC particles in TDR were found to undergo slow attrition during electrolysis. It is inferred that carbon attrition may prove to be a major setback for scale up attempts as it can lead to gradual loss in liquid holding capacity of carbon bed due to stratification and filling of voids in the carbon bed with carbon fine dust.

Preparation of poly ethyleneimine (PEI))/nano titania (TiO2) multilayer film on quartz tube by layer-by-layer self-assembly and its applications for petroleum refinery wastewater treatment

Poly ethyleneimine (PEI)/titania (TiO2) multilayer film on quartz tubes have been successfully fabricated via a layer-by-layer (LbL) self-assembly method. scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) surface area analysis were carried out for characterization and determination of the morphology and roughness of the prepared thin films on quartz tube. AFM and SEM images indicated that the film surface is smooth and uniform, and thickness of the film was estimated to be around 120nm. The BET characterization proved the formation of multilayer thin film. The photocatalytic activity of the PEI/TiO2 multilayer deposited on the quartz tubes was evaluated in the treatment of raw petroleum refinery wastewater (PRW) under UV light irradiation in three annular photocatalytic reactors. Our preliminary study showed that the most significant variables on the PRW treatment in these photoreactores are initial chemical oxygen demand (COD) concentration, H2O2 concentration, pH and reaction time. Thus, further experiments and optimization were performed using response surface methodology (RSM) based on three-level central composite design to evaluate process conditions. Maximum COD removal (98%) was achieved at the optimum conditions (initial COD concentration of 200mg/L, Hydrogen peroxide concentration of 8.8mM, pH of 6 and reaction time of 120min).

Kinetics studies of catalytic ozonation of distillery effluent

The decolorization and degradation of pollutant in the distillery effluent using catalytic ozonation process were studied. The effect of various experimental parameters such as ferrous ion concentration (2–10 mM), initial chemical oxygen demand (COD) concentration (250–1000 ppm), effluent initial pH (2–10), and H2O2 concentration (25–200 mM) has been studied on the percentage color removal. The color removal increases with increase in ferrous ion concentrations, initial pH, and H2O2 concentration. However the percentage color removal decreases with increasing initial COD concentration. Three different systems of O3; O3/Fe2+, O3/Fe2+/H2O2 were compared for the percentage color removal. It has been observed from investigation that ozonation alone is not effective to decolorize and in removal of COD in the effluent. The results show that catalytic ozonation gives 81.61% color removal for the effluent. Further, the kinetic study has been carried out for the percentage color removal of the distillery effluent.

Development of Rapid Chemical Oxygen Demand Analysis Using Ozone as Oxidizing Agent

A new and environmental friendly method for the rapid determination of Chemical Oxygen Demand (COD) as a measure of organic pollution was developed. Ozone was used as an oxidizing agent in the current method. Experiment was setup in 500mL glass bottle containing 390mL distilled water and 10mL wastewater sample at 31°C. The extent of dissolved ozone reacted with the wastewater sample was monitored through an ozone sensor. Reaction time of 60seconds achieved good linear correlation between the extent of ozone degradation and the wastewater concentrations. The results showed that the rate and extent of ozone degradation are linearly proportional to the initial COD concentrations in range of 0-80mg/L for the glucose- containing distilled water and canteen wastewater.

Biodegradation of Bisphenol-A in aerobic membrane bioreactor sludge

Bisphenol-A (BPA) biodegradation was studied in a membrane bioreactor under aerobic conditions. The effects of the initial BPA concentration and initial chemical oxygen demand (COD) concentration on BPA biodegradation were investigated. The degradation process followed a first-order kinetic (more than 98% of BPA was removed) with a kinetic rate constant of 1.134 h(-1) using an initial BPA concentration of 1.0 mg L(-1). The kinetic rate constant decreased to 0.611 h(-1) when the initial BPA concentration increased to 5.0 mg L(-1). The initial COD concentration (400 and 2,000 mg L(-1)) did not affect the biodegradation kinetic of BPA.

Effects of partial ozonation on activated sludge process for the minimization of excess sludge production during biological treatment

Minimization of excess sludge production may be achieved by either changes in operational conditions or by the treatment of recycled activated sludge. It was investigated using ozone-treated return activated sludge in lab-scale activated sludge process operated continuously with optimum conditions determined using Box–Behnken experimental design method as 400 mg/L initial chemical oxygen demand concentration (CODi), 25 h hydraulic retention time, and 25 d solid retention time, respectively. Batch experiments were carried out in order to determine the optimum ozone dose of 0.05g O3/g total solid considering disintegration degree (DD). Ozone reactor (OR) and control reactor (CR) were evaluated considering sludge reduction capacity, effluent quality, and sludge characteristics. About 61 and 40% reductions can be achieved in mixed liquor suspended solid concentration and observed sludge yield value in OR compared to CR, respectively. The effluent quality in terms of COD and NH4–N removal in OR was not significantly affected by ozonation. The dewatering capacity was slightly weakened while little improvement was observed in filtering capacity in OR compared to CR, in terms of capillary suction time and specific resistance to filtration. Particle size changed and sludge destruction led to an increase of small particles.

Biodegradation of TCP in a Sequencing Batch-Fluidized Bed Bioreactor with Waste Coke Particles as the Carrier

AbstractThis study investigated the biodegradation of synthetic wastewater containing 2,4,6-trichlorophenol (TCP) in a sequencing batch-fluidized bed bioreactor (SBFBBR) with waste coke particles (WCPs) as the biofilm carrier. The irregular surfaces of WCPs (diameter range from 0.6 to 2.3 mm) rendered them ideal biomass carriers. The attached biomass was 4.0–4.5 mg volatile suspended solids (VSS)/g WCPs 3 weeks after reactor start-up, and the biofilm thicknesses were 35–110 μm. Biodegradation, not adsorption-degradation or volatilization-degradation, was found to be the main TCP removal mechanism. At the initial chemical oxygen demand (COD) concentration of 300 mg L−1, removal of COD was more efficient and faster than that of TCP. The air-water ratio (ranging from 0.280 to 0.58 min−1) exerted negligible effects at dissolved oxygen (DO) concentrations above 2 mg L−1. Maximum TCP degradation (62.1% after 3 h retention time and 75.8% after 6 h) occurred at initial COD concentration of 45 mg L−1. TCP can ...

Supercritical water oxidation of N-phenylglycinonitrile wastewater

ABSTRACT N-phenylglycinonitrile wastewater was treated with supercritical water oxidation (SCWO), at temperatures ranging from 375 to 550°C, a pressure of 25 MPa, residence times ranging from 5 to 60 s, and initial reactant concentrations ranging from 2,400 to 24,400 mg O2/L in terms of chemical oxygen demand (COD). Results showed that when the initial COD of the wastewater was low and the oxidant was abundant, the temperature and residence time had significant effect on COD removal, while the initial COD concentration and oxidant dose did not show significant effects. A global rate expression was regressed from the complete set of data. An assumed pseudo-first-order global rate expression was determined with activation energy of 52.9(±2.9) kJ mol−1 and a preexponential factor of 3.6(±1.4) × 102 s−1.