Enhancing Biodegradability of Textile Wastewater by Ozonation Processes: Optimization with Response Surface Methodology

ABSTRACT

In this study, an ozonation process was used to increase biodegradability of textile wastewater by considering chemical oxygen demand (COD) and color removal. Response surface methodology was applied in order to determine the significance of independent variables which are initial pH, reaction time and ozone dose. While a biological oxygen demand (BOD)/COD rate of 0.315 was obtained at optimum conditions, which are pH 9, 75 min of reaction time and 26 mg/L ozone dose, color and COD removal was obtained at 74% and 39%, respectively. BOD/COD ratio value increased from 0.18 to 0.32 by ozonation process. In addition, k coefficient for BOD also increased from 0.21 to 0.30 d^?1.     

用UV/H2O2,UV/O3,UV/H2O2/O3催化处理城市固体垃圾填埋渗出物

The performance of UV/H2O2, UV/O3, and UV/H2O2/O3 oxidation systems for the treatment of municipal solid-waste landfill leachate was investigated. Main objective of the experiment was to remove total organic carbon (TOC), non-biodegradable organic compounds (NBDOC) and color. In UV/H2O2 oxidation experiment, with the increase of H2O2 dosage, removal efficiencies of TOC and color along with the ratio of biochemical oxygen demand (BOD) to chemical oxygen demand (COD) of the effluent were increased and a better performance was obtained than the system H2O2 alone. In UV/H2O2 oxidation, under the optimum condition H2O2 (0.2 time), removal efficiencies of TOC and color were 78.9% and 95.5%, respectively, and BOD/COD ratio was significantly increased from 0.112 to 0.366. In UV/O3 oxidation, with the increase of O3 dosage, removal efficiencies of TOC and color along with BOD/COD ratio of the effluent were increased and a better performance was obtained than the system O3 alone. Under the optimum condition UV/O3     

Electrocoagulation process for the post-treatment of anaerobically treated urban wastewater

Suitability of the electrocoagulation (EC) process for the post-treatment of anaerobically treated urban wastewater was assessed, in batch system employing real effluent from an upflow anaerobic sludge blanket (UASB) reactor. Response surface methodology (RSM) was used to optimize three important process parameters, namely current density, electrolysis time and initial pH. At the optimum conditions of pH 7.07, electrolysis time 18.0 min and current density 15.0 mA/cm², chemical oxygen demand (COD), turbidity and phosphate removal efficiencies observed were 71.0%, 98.5% and >99.9%, respectively, which were very close to the model-predicted values. High removals of suspended solids (SS; 87.5%), biochemical oxygen demand (BOD) (83.3%) and total coliforms (99.994%) were also obtained at the optimum conditions.     

Incidence of an Ozonation Stage on the Treatment of Cherry Stillage by Activated Sludge

This article presents a laboratory study of the ozonation of diluted cherry stillage, a high-strength wastewater. Influence of variables, kinetics, and the effects of an ozonation stage coupled with the biological treatment by activated sludge are addressed. Single activated sludge processing was shown effective to remove biological oxygen demand (BOD) and chemical oxygen demand (COD) but polyphenols were reduced to a lesser extent. On the other hand, direct wastewater ozonation did not reduce COD and total organic carbon (TOC) appreciably, and foaming problems were experienced when a high gas flow rate was applied. However, polyphenols and UV₂₅₄ absorbance decreased substantially by means of ozonation. To best achieve complete cherry stillage purification, two ways of coupling ozonation with activated sludge are proposed. Ozonation prior to activated sludge is advised for high-concentration wastewater to reduce polyphenol concentration, thus removing inhibiting effects. For wastewater with low polyphenol concentration the sequence activated sludge–ozonation–activated sludge is preferred to enhance the overall process performance in terms of oxidation efficiency and sludge settling.     

Emissions From Kiln Drying of Pinus radiata Timber: Analysis,Recovery, and Treatment

The effect of drying schedules was investigated on the volatile organic compounds (VOCs) emission from kiln drying of Pinus radiata timber. An enclosed drying system has been invented to recover the VOCs emission and the heat in the drying medium. A new technology, called TOCKDOST, was also developed for treatment of the emission condensate for safe discharge to the environment. The condensate had high chemical oxygen demand (COD) of 256–280 mg l^?1, high total organic carbon (TOC) of 56–69 mg l^?1, and low pH of about 3.7, and thus required treatment before being discharged to the environment. After numerous trials, it has been found that the most effective treatment was to use Fenton's reagent followed by activated carbon adsorption. With optimum treatment conditions, the average COD was reduced by 93%, TOC was reduced by 87%, and pH was increased to about 6.     

A study of A2/O process in El-Berka WWTP by replacing the anaerobic selector with UASB and adopting a hybrid system in the oxic zone

ABSTRACT

A multistage system comprising an upflow anaerobic sludge blanket (UASB) followed by anoxic unit and then oxic activated sludge (AS) with biofilm is studied in El-Berka WWTP, Egypt. Different organic loading wastewaters of chemical oxygen demand (COD) less than 500 mg/L till 3000 mg/L are tested during the study. The hydraulic retention time (HRT) varies for each loading from 7.5 to 10 to 15 h. The UASB reactor accomplishes the removal efficiency of 50%–70% of influent COD. The overall system performs the removal efficiency of 95% of influent COD and NH₄-N. Also, the results are verified by a modified mathematical model.     

Efficient mineralization of sugar industry wastewater by catalytic wet air oxidation as an eco-friendly method and its kinetic modelling

In this study, catalytic wet air oxidation using lanthanum cobalt oxide (LaCoO₃) as catalyst was employed for the efficient treatment of synthetic sugar industry wastewater in a single process. A parametric study was performed to determine the optimum conditions. The results showed that reaction temperature and theoretical air percentage were the most effective parameters. Sugar derivatives were almost completely destroyed at the optimum conditions and total organic carbon (TOC) and chemical oxygen demand (COD) removals were determined as 91% and 87%, respectively, indicating a high mineralization degree, which was the main goal of advanced oxidation. The reaction kinetics were investigated by pseudo-homogeneous and heterogeneous models based on two different parameters: sucrose and TOC concentration. The degree of fit showed that the reaction order was determined as two for the pseudo-homogeneous approach. According to the surface concentration calculations for heterogeneous models, the presence of mass transfer limitations was only observed for oxygen as gas reactant. All heterogeneous models also fitted the reaction rate data accurately, but the Mars–van Krevelen was the selected model for sucrose and TOC oxidation with the best fit.     

A comparative study of electrocoagulation and electro-Fenton for food industry wastewater treatment: Multiple response optimization and cost analysis

ABSTRACT

In this study, response surface methodology was applied for food wastewater by electrocoagulation (EC) and electro-Fenton (EF) processes. The optimum conditions for the chemical oxygen demand (COD) removal were found to be 21.36 min, pH 10 and 86 mA/cm² in EC, whereas 27.11 min, pH 2.38, 86 mA/cm² and H₂O₂/COD:2 in EF process. COD removal efficiencies were determined to be 29.4% for EC and 59.1% for EF processes and higher than 99% total suspended solids removal efficiencies were achieved. It can be concluded that high COD removal was obtained (4998 mg/L COD removal by EC and 10,047 mg/L COD removal by EF).     

Fenton试剂对垃圾渗滤液中腐殖质的氧化/混凝作用

采用Fenton试剂处理反渗透浓缩垃圾渗滤液,通过COD,TOC,UV254以及COD/TOC等表征手段考察氧化/混凝作用对COD和腐殖质去除效果的影响。结果表明,Fenton试剂对浓缩渗滤液中腐殖质去除（11.9 % ~ 89.5 %）高于总COD去除（9.6 % ~ 75.2 %）;渗滤液中腐殖质降解和COD去除具有较好的相关性。混凝作用（CODcoag,HScoag）受氧化作用（CODoxid,HSoxid）的影响并与之相反,氧化作用越大,混凝作用越小。(COD/TOC)oxid变化表明,在[H₂O₂]>80 mmol.L^-1,pH=2.0~4.0, [Fe ²⁺ ]=40~160 mmol.L^-1,反应时间2 h的实验条件下,渗滤液中有完全氧化过程发生,同时(COD/TOC)coag的变化说明经混凝作用去除的有机物氧化态高于其它实验区间。     

Enhancing the ozonation of industrial wastewater with electrochemically generated copper(II) ions

This study evaluates the effect of adding electrochemical copper(II) ions into an ozonation process for treating industrial wastewater. Combining the processes resulted in a synergy that enhanced the reduction of physicochemical parameters (COD, TOC, color, turbidity, Z-Potential, and conductivity). In only 15 minutes the integrated process reduced the COD by 83%, TOC by 78 %, color by 93%, turbidity by 77%, and conductivity by 27% at relatively low current density (12.5 mA cm^?2). Thus, the combination of the electrochemical and ozonation processes noticeably improves wastewater quality, decreases the process time, and reduces the sludge production.     

Optimum Process Parameters for the Treatment of Landfill Leachate Using Powdered Activated Carbon Augmented Sequencing Batch Reactor (SBR) Technology

The sequencing batch reactor (SBR) process was used for the treatment of raw landfill leachate. Optimum preliminary parameters of leachate/activated sludge ratio, powdered activated carbon (PAC) dosage, and settling time were studied. Optimum obtained parameters (mixing ratio of 10%, PAC dosage of 10 g/L, and settling time of 1.5 h) were applied on two types of SBRs, namely, non-powdered and powdered activated carbon (NPAC and PAC, respectively). Consequently, the effect of factors, the aeration rate and contact time, on both NPAC and PAC reactors were studied. Response surface methodology was used for the design, analysis, and optimization of the experiments. Removal efficiencies of ammonia (NH₃-N), color, chemical oxygen demand (COD), total dissolved salts (TDS), and sludge volume index (SVI) were measured for 13 experiments. Based on the obtained results, the optimum aeration rate and contact time for both NPAC and PAC reactors were 2 and 1 L/min and 5.56 and 5.5 h, respectively. Better performance (in terms of NH₃-N, color, COD, and TDS removal efficiencies and SVI values) was exhibited by PAC reactors rather than NPAC.     

Performance of a ZVI‐UASB reactor for azo dye wastewater treatment

BACKGROUND: Zero valent iron (ZVI) is expected to be helpful for creating an enhanced anaerobic environment that might improve the performance of the anaerobic process. Based on this idea, a ZVI packed upflow anaerobic sludge blanket reactor (ZVI‐UASB) was developed to enhance azo dye wastewater treatment. RESULTS: The ZVI‐UASB reactor was less influenced by a decrease in the operational temperature from 35 °C to 25 °C than a reference UASB reactor that did not contain ZVI. In addition, chemical oxygen demand (COD) and color removal efficiencies of the ZVI‐UASB reactor at an HRT of 12 h exceeded those of the reference reactor at an HRT of 24 h. The hydraulic circulation in the ZVI bed enhanced the function of ZVI so that it improved the COD and color removal efficiencies. Moreover, fluorescence in situ hybridization experiments revealed that the abundance of Archaea in the sludge of the ZVI bed was significantly higher than that at the reactor bottom, which made the reactor capable of greater COD removal under low temperature and short HRT conditions. CONCLUSION: This ZVI‐UASB reactor could adapt well to changes in the operational conditions during wastewater treatment. Copyright © 2010 Society of Chemical Industry     

Textile wastewater treatment efficiency by Fenton oxidation with integration of membrane separation system

This work investigates the performance of an integrated Fenton-Ultrafiltration treatment scheme to treat textile wastewater. The treated effluent is particle-free at a quality higher than that obtained by any novel membrane based process or Fenton oxidation in singularity. The study is divided into three parts: part one, Fenton process was optimized for COD: H₂O₂ (wt/wt), H₂O₂: Fe⁺² (wt/wt) and pH to attain highest degradation removal and lowest sludge generation. The process efficiency was analyzed by considering COD, TOC and color removal as key parameters. Part two, the process was scaled up to 5?L and efficiency of integrated system was investigated under optimized conditions by using two different types of membranes at different operating pressures. Part three, the performance of membrane process was studied in terms of flux behavior and its recovery. The treated effluent has COD, TOC and color removal values of 48.0?mg/L, 1.2?mg/L and >99% respectively. These values are compliant to typical discharge environmental standards.     

Experimental study on electrocoagulation of textile wastewater by continuous horizontal flow through aluminum baffles

We investigated the feasibility of applying a continuous textile wastewater (TWW) treatment, which was accomplished by using electrocoagulation (EC) unit with zigzag horizontal flow across a series of mono-polar aluminum plate baffles. The effects of operating parameters such as current density (20-80 A/m²) and detention time (5-40 min) on turbidity, color, chemical oxygen demand (COD), total suspended solids (TSS) and total dissolved solids (TDS) removal were studied. The optimum conditions were determined as 60 A/m² and 20min by monitoring zeta potential (ζ) of effluent. At the optimum conditions, removal efficiencies for turbidity (97.63%), color (87.87%), COD (93.3%), TSS (94.02%), and TDS (52.13%) were observed. Further, addition of 4mg/L of NaCl dose in the TWW modified conductivity suitably, thereby reducing electrical energy consumption per cubic meter of waste water and specific electrical energy consumption (SEEC) from 13.33 to 2.67kWh/m³, and 23.84 to 4.77kWh/kg Al, respectively. Comparing the EC with conventional coagulation process, EC showed better pollutant removal efficiency.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O₃, H₂O_2, and Fe²⁺ dosages. H₂O₂ addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV₂₅₄) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV₂₅₄when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.     

Decolorization and COD reduction of disperse and reactive dyes wastewater using chemical-coagulation followed by sequential batch reactor (SBR) process

This paper summarizes the results of disperse and reactive dyes wastewater treatment processes aiming at the destruction of the wastewater's color and chemical oxygen demand (COD) reduction by means of coagulation/flocculation (CF) followed by sequential batch reactor (SBR) process. The color removal efficiency of magnesium chloride aided with lime [MgCl₂/CaO] was compared with that of alum [Al₂ (SO₄)₃] and lime [Cao]. The experimental results showed that treatment with lime alone (600 mg/l) at pH value of 11.7 proved to be very effective. Color removal reached 100% and COD was reduced by 50%. Treatment with magnesium chloride aided with lime at pH value of 11 removed color completely and reduced the COD value by 40%. However, lime or lime in combination with magnesium chloride produced high amounts of sludge (1.84 kg/m³ for lime & 1.71 kg/m³ for MgCl₂ aided with lime). Also, the pH of the treated effluent was around 11 and needs correction prior to discharge into sewer network. The use of 200 mg/l alum without pH adjustment removed 78.9% of the color. To improve the effectiveness of alum, the cationic polymer namely cytec was used as a coagulant aid. This significantly increased color removal from 78.9 up to 94% and COD reduction was around 44%. Moreover, sludge production was only 0.36 kg/m³. Chemically pre-treated effluent was subjected to SBR process at an HRT of 5.0 h. Residual COD_total, total biochemical oxygen demand (BOD_{5 total}) and total suspended solids (TSS) in the final effluent were 78 ± 7.7; 28 ± 4.2 and 17 ± 4.2 mg/l, corresponding to the removal efficiency of 68.2; 76.3 and 61.4% respectively. Furthermore, almost complete removal of COD_particulate and BOD_5particulate has been achieved.     

Slaughterhouse wastewater treatment by combined anaerobic baffled reactor and UV/H2O2 processes

Combined processes of biological anaerobic baffled reactor (ABR) and UV/H₂O₂ at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater. In this study, the total organic carbon (TOC) loadings of 0.2-1.1 g/(L day) were used. The results revealed that combined processes had a higher efficiency to treat the synthetic slaughterhouse wastewater. Up to 95% TOC removal was obtained for an influent concentration of 973.3 mgTOC/L at the hydraulic retention time (HRT) of 3.8 days in the ABR and 3.6 h in the UV photoreactor. Meanwhile, up to 97.7% and 96.6% removal of chemical oxygen demand (COD) and 5-day carbonaceous biochemical oxygen demand (CBOD₅) were observed in the ABR for the same influent concentration, respectively. Comparatively, for an influent concentration of 157.6 mgTOC/L, the UV/H₂O₂ process alone with the TOC loading of 0.06-1.9 g/(L h) was also studied, in which, up to 64.3%, 83.7%, and 84.3% of TOC, COD, and CBOD₅ removal were observed, respectively, at the HRT of 2.5 h with hydrogen peroxide (H₂O₂) concentration of 529 mg/L. It was found that individual ABR and UV/H₂O₂ processes enhanced the biodegradability of the treated effluent by an increased CBOD₅/COD ratio of 0.4 to 0.6. An optimum H₂O₂ dosage of 3.5 (mgH₂O₂)/(mgTOC_in h) was also found for the UV/H₂O₂ process.     

Biological treatment of saline wastewaters from marine‐products processing factories by a fixed‐bed reactor

Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30 g dm^?3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish‐processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000 mg COD dm^?3 day^?1. Under low OLR (250 mg COD dm^?3 day^?1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000 mg COD dm^?3 day^?1. © 2002 Society of Chemical Industry     

Treatment of the refinery wastewater in a gas–liquid–solid three‐phase flow airlift loop bioreactor

Aerobic treatment of refinery wastewater was carried out in a 200 dm³ gas–liquid–solid three‐phase flow airlift loop bioreactor, in which a biological membrane replaced the activated sludge. The influences of temperature, pH, gas–liquid ratio and hydraulic residence time on the reductions in chemical oxygen demand (COD) and NH₄‐N were investigated and discussed. The optimum operation conditions were obtained as temperature of 25–35 °C, pH value of 7.0–8.0, gas–liquid ratio of 50 and hydraulic residence time of 4 h. The radial and axial positions had little influence on the local profiles of COD and NH₄‐N. Under the optimum operating conditions, the effluent COD and NH₄‐N were less than 100 mg dm^?3 and 15 mg dm^?3 respectively for more than 40 days, satisfying the national primary discharge standard of China (GB 8978‐1996). Copyright © 2005 Society of Chemical Industry     

Ozonolysis Post-Treatment of Anaerobically Digested Distillery Wastewater Effluent

ABSTRACT

In this study, the ozonolysis of real anaerobically digested distillery wastewater (DWW) was carried out. The effect of operating parameters, such as pH, initial concentration, and ozone dosage, on the efficiency of ozone utilization, color removal, and sludge solubilization was studied. The highest ozone utilization of 99% was observed at the highest initial concentration (COD of 3000 mg/L) and lowest ozone flowrate (22.5 mg O₃/L/min), but with a very low color reduction of 20%, after 60 minutes of ozonolysis. To achieve a higher color reduction >80% and at ozone utilization >95%, the DWW had to be diluted twice (COD 1500 mg/L), and the flowrate doubled to 45 mg O₃/L/min. The reduction in color signified the oxidation of the color causing biorecalcitrant aromatic melanoidin compounds. This was confirmed by the 47% reduction in ultraviolet absorbance at 254 nm indicating the breakdown of the complex aromatic compounds into low molecular weight organics. Moreover, increases in average oxidation state from ?0.6 to ?0.2 suggested a decline in aromaticity and formation of easily biodegradable aliphatic compounds. The ozonolysis process was found to follow the first-order reaction kinetic model with the highest rate constant of 0.0326 min^?1 obtained. A reduction in suspended COD by 88% indicated solubilization of the sludge contained in the effluent.