Initial pH Of Wastewater Research Articles

High-Efficiency Degradation Sugar Wastewater by Co-TiO2 Nanotube Arrays

This work presents a novel approach for preparing TiO2 nanotube arrays loaded with highly dispersed Co nanoparticles through an ultrasound aided photochemical route. The Co content doped on the arrays was controlled by changing the concentration of Co(NO3)2 and the ultrasound time. The Co doped TiO2 nanotube arrays were characterized by SEM, XRD, EDS and UV–Vis spectrum. The photocatalytic activities of TiO2 nanotube arrays electrode were studied. The results showed that Co doping significantly enhanced the photocatalytic degradation rate of TiO2 nanotube arrays under UV-light irradiation. The main factors affected photocatalytic degradation of sugar wastewater such as the illumination time, pH, different concentrations of H2O2 and wastewater with undoped TiO2 nanotube arrays were compared. The results showed that the longer the exposure time, the higher the initial pH of wastewater is more favorable for the Co-TiO2 nanotube arrays, The concentration of H2O2 is 60mmol/L, and compared to undoped TiO2 nanotube arrays Co doped TiO2 nanotube arrays have better photocatalytic properties.

Solar Photocatalytic Degradation of Azo Dye in AqueousTiO2Suspension Assisted by Fresnel Lens

Solar TiO2photocatalytic process assisted by a Fresnel lens was investigated for treating an azo dye wastewater of Acid Orange 10 (AO10). Response surface methodology (RSM) was employed to assess the effect of critical process parameters (including initial pH of wastewater, concentration of TiO2, and reaction time) on treatment performance in terms of COD and TOC degradation efficiency. Optimized reaction conditions based on the analysis of RSM were established under an initial pH of 6.0, a concentration of TiO2of 1 g/L, and a reaction time of 2 h for reaching a 90% COD and TOC degradation of AO10 wastewater. With the assistance of Fresnel lens, the TOC degradation rate of AO10 wastewater increased significantly from 0.606 h−1and 0.289 h−1to 1.477 h−1and 0.866 h−1in summer (June) season (UV280–400 nm nm: 39.9–44.8 W/m2) and winter (December) season (UV280–400 nm nm: 23.9–26.9 W/m2), respectively. This could be mainly due to the concentrating effect of Fresnel lens for solar energy, resulting in an increase of 2~2.5 times of solar light intensity and a raising heat irradiation in terms of 10~15 °C of wastewater temperature. These results revealed that solar energy could be concentrated effectively by using Fresnel lens and showed a significant promoting effect on the TiO2photocatalytic degradation of dye wastewater.

Preparation of a composite coagulant: Polymeric aluminum ferric sulfate (PAFS) for wastewater treatment

A new composite coagulant polymeric aluminum ferric was synthesized and parameters affecting the coagulant performance such as reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios in this study, were examined. In addition, to obtain the optimum synthetic conditions resulting in the maximum turbidity removal efficiency, response surface methodology (RSM) was used to assess their interactive effects on coagulation–flocculation performance. The results showed that reaction temperature (60–80 °C) and time (30–50 min), and OH/Fe (0.1–0.3), P/Fe (0.2–0.3) and Al/Fe (1:9–1:10) molar ratios were favorable to the preparation process. The optimum synthesis conditions were reaction temperature and time, and OH/Fe, P/Fe and Al/Fe molar ratios of 80 °C, 40 min, 0.1, 0.25 and 1:10, respectively. Evaluation of the coagulation–flocculation process showed that COD (chemical oxygen demand) and turbidity removal efficiency of 82.8% and 98.2%, respectively, were achieved at coagulant dosage of 45 mg/L, wastewater initial pH of 8.5, and rapid agitation speed of 250 rpm. In addition, charge neutralization and adsorption/bridging coagulation–flocculation mechanisms played an important role in reducing the surface charge of colloids.

Characterization and coagulation–flocculation behavior of polymeric aluminum ferric sulfate (PAFS)

Recent advance on the application of the composite coagulant in the coagulation–flocculation process has attracted a widespread interest. Previous research has demonstrated that iron-based composite coagulant could enhance the performance of the coagulation–flocculation. In this research, results of an experimental study using polymeric aluminum ferric sulfate (PAFS) as a modified coagulation reagent for treating wastewater was presented. The structure and morphology of PAFS were investigated using some conventional methods, and response surface method (RSM) was employed to optimized the coagulation–flocculation process while the evaluation of treatment efficiency was determined by measuring both the reduction of turbidity and chemical oxygen demand (COD). In addition, parameters affecting coagulation–flocculation behavior such as coagulant dosage, wastewater initial pH, were also examined. The results showed the structure of PAFS as a non-stoichiometric basic iron sulfate salt taking the shape of a compact network and exhibited better coagulation–flocculation performance when the species distribution of (Fe–Al) a, (Fe–Al) b and (Fe–Al) c in PAFS were 37.4%, 3.79% and 59.08%, respectively. Compared with PFS, PAFS showed a superior flocculation performance with the maximum COD removal efficiency of 83.6% and the lowest residual turbidity of 0.96 NTU at the coagulant dosage of 45 mg/L. In the coagulation–flocculation process, the adsorption-bridging and charge neutralization mechanisms played an important role in colloidal destabilization and aggregation.

Study on Treatment of Acid Scarlet GR Wastewater by Coupling System of K<sub>2</sub>FeO<sub>4</sub> –PAFC

Using Ferrate (K2FeO4) and polymer flocculant PAFC (PAFC) Collaborative approach, deal with the Acid Scarlet GR Wastewater. Study the effect of Ferrate dosage, PAFC dosage, Ferrate dosing time, Wastewater initial pH Value. Results show that Ferrate pre-oxidation can significantly improve the Coagulation for the removal of Acid Scarlet GR. when the initial concentration of Acid Scarlet GR is 25mg/L, Ferrate dosage is 90mg,PAFC dosage is 13mL,the removal of Acid Scarlet GR is 95.67%.pH on Ferrate removal of Acid Scarlet GR wastewater has little effect. When pH value is 4-8, the removal rate can reach more than 92%.When pH value is 5.6,the removal rate is the highest.

Treatment of Distillery Wastewater by the Nano‐Scale Zero‐Valent Iron and the Supported Nano‐Scale Zero‐Valent Iron

The treatment of wastewater from the distillery industry was carried out by using nano-scale- and supported nano-scale zero-valent iron at a laboratory scale and ambient temperature. Effects of dilution, pH, mixing rate, zero-valent iron dosage, and amount of support for the zero-valent iron were investigated. All parameters had a significant effect on the removal efficiency of all investigated pollutants. Increasing the number of dilutions and the nano-scale zero-valent iron dosage led to the increase of removal efficiency of pollutants. Higher removal efficiency was achieved in an acidic initial pH of wastewater. The reduction of all pollutants was limited by the kinetics of the pollutant destruction/reduction by nano-scale zero-valent iron particles at a mixing rate greater than 170 rpm. At optimum condition, greater than 95, 94, and 64% of color, chemical oxygen demand, and biochemical oxygen demand were removed, respectively, within 6 hours. Additionally, the presence of a support had a significant effect on pollutant removal.

Optimization of the fenton oxidation of wastewater generated by rape oil soapstock splitting

AbstractThe study was designed to assess the effective elimination of total phosphorus (TP) and chemical oxygen demand (COD) from pretreated wastewater generated by the splitting of rape oil soapstock rich in phospholipids. The wastewater indicated a high‐TP content (108 mg/L) and COD 1488 mg/L. The optimization tests were carried out using a five‐level, four‐variable central composite rotatable design, and the tested variables included initial H2O2 concentration (X1), Fe2+/H2O2 molar ratio (X2), initial temperature (X3), and wastewater pH (X4). TP and COD mathematical models of changes were developed as a function of tested variables based on the test results. Statistical analysis of the resultant models permits the conclusion that all tested variables substantially influence the effective removal of COD, whereas the initial pH of wastewater has no considerable impact on the effective elimination of TP. The optimal conditions of the Fenton process were achieved for X1 = 4.5 g/L, X2 = 0.1, X3 = 30°C, and X4 = 9. It is possible to reduce TP to 1.05 mg/L and COD to 132.1 mg/L under such conditions. © 2010 American Institute of Chemical Engineers Environ Prog, 2010

Investigations of coagulation–flocculation process by performance optimization, model prediction and fractal structure of flocs

In this paper, results of an experimental study of polymeric phosphate-aluminum chloride (PPAC) as a modified coagulation reagent used to treat wastewater and fractal characteristics of flocs in a sewage treatment process were presented. Operating variables such as P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed, which could influence the coagulation behavior of PPAC were experimentally tested. The evaluation of treatment efficiency was determined by measuring both the reduction of chemical oxygen demand (COD) and residual turbidity. It showed that the optimum removal efficiency was achieved when the P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed were 1.2, 9.0, 0.36g/L and 100rpm respectively. Under optimum conditions, the removal efficiency was 73.5% and 99.5% for COD and turbidity. In addition, radial basis function (RBF) neural network established in this paper was used to predict the flocculation efficiency. The results revealed a promising operational forecasting capability. Furthermore, an inverted optical microscope was used to investigate the fractal structure of flocs formed during coagulation–flocculation. The results showed that under optimum conditions, with the increase of fractal dimension of the flocs, the COD removal efficiency increased while the flocs became denser with large cutter size.

Application of the electrocoagulation technique for treating heavy metals containing wastewater from the pickling process of a billet plant

This work was carried out to study the removal of various heavy metals, including Cu, Cr, Pb and Zn, from billet industry wastewater by the electrocoagulation process in both batch and continuous experiments at a laboratory scale and ambient temperature (30 °C). In the batch experiment, the effect of various parameters including the current density, initial wastewater pH and electrolysis time, on the metal removal efficiency was examined. Optimal metal ion depletion was attained with a current density of 98 A/m2, an initial wastewater pH of 5 and a 30 min electrolysis time. Under these conditions, greater than 99% of Cu, Cr and Zn was removed, whilst the outlet wastewater contained Cu, Cr, Pb and Zn at less than 0.02, 0.01, 0.07 and 0.05 mg/l, respectively. For the continuous process, the results indicated that the treatment system reached its steady state condition within 120 min, and the optimum condition for the continuous treatment was found at an initial wastewater pH of 3 and flow rate of 55 ml/min. At this condition, a complete removal of Cu and Pb and greater than 99% removal of Cr and Zn were achieved.

Simultaneous removal of organic and inorganic pollutants in tannery wastewater using electrocoagulation technique

Tannery wastewater can cause severe environmental problems related to its high chemical oxygen demand, high biochemical oxygen demand, high total suspended solids, high oil and grease contents together with the elevated chromium concentration and objectionable color. The one-step electrocoagulation process was carried out to simulta- neously remove chromium and various pollutants from tannery wastewater at ambient temperature in the laboratory scale. Low-cost commercial iron plates were employed in this study as anodes and cathode materials. Effects of various parameters were investigated including types of electrode configuration, initial pH of wastewater (7-9), current density (15.7-24.6 Am −2 ) and circulating flow rate of wastewater (0-3.67 lmin −1 ). The optimum condition was found by applying the mono-polar electrode in a parallel connection at the current density of 22.4 Am −2 , flow rate of wastewater of 3.67 lmin −1 and 20 min electrolysis time. The initial pH of wastewater ranging from 7-9 provided the similar removal effi- ciency. At optimum condition, more than 95% of chromium and pollutants except TKN and TDS were eliminated from the wastewater and the properties of the treated wastewater met the standard and permitted to discharge into the en- vironment. The required energy consumption at optimum condition was less than 0.13 kWhm −3 wastewater. In addition, the COD reduction was fit very well with the first-order kinetics model.

Agricultural residue anion exchanger for removal of dyestuff from wastewater using full factorial design

In this study, Remazol Black B dyestuff removal from wastewater by ion exchange was investigated with in a batch system and 2 3 full factorial design was applied. Anion exchanger resin was prepared from agricultural residue (straw) after reaction with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (EDM method). The effect of individual variables and their interactional effects for dyestuff sorption were determined. From the statistical analysis, the most important parameter which is efficient in dyestuff removal can be obtained to be initial concentration of wastewater, which is followed by initial concentration–initial pH of wastewater. The interaction between initial pH and temperature was the least important factor for dyestuff removal from wastewater. A series of isotherm studies were undertaken, and the data evaluated for compliance with the Langmuir and Freundlich isotherm models.

Some properties on the application of Candida utilis TISTR No. 5001 into sequencing batch reactor (SBR) System

The use of C. utilis TISTR No. 5001 as a substitute for bacterial sludge in the SBR system was examined in this study. To stimulate and maintain Candida utilis TISTR No. 5001 as the dominant strain in the SBR system, the initial pH of wastewater had to be controlled in the acidic range (5-6). The laboratory scale SBR system (10-L reactor volume) with C. utilis TISTR No. 5001 (Y-SBR system) operating at 1 cycle/day, ambient temperature (25-29oC), impeller speed of 60 rpm, dissolved oxygen of 2.0-2.5 mg/l and replacement volume of 2.50 L/d, showed the highest COD, BOD5 and total nitrogen (TN) removal efficiencies of 97.2±1.6, 97.6±1.6 and 53.1±0.6%, respectively, with synthetic waste water, SWW (pH5), under an organic loading of 0.45 kg BOD5/m3-d. The effluent NO3 - and effluent NO2 - of the system were only 0.42±0.06 mg/l and 0.05±0.007 mg/l, respectively. The sludge age (SRT) and sludge volume index (SVI) of the system were 19±2.3 days and 72±8.2 ml/g, respectively. The SBR system with a mixed culture of C. utilis TISTR No. 5001 and bacterial sludge (Y-SBS-SBR system) showed high organic removal efficiencies of higher than 95% with both acidic-SWW and alkaline-SWW. Furthermore, it showed the highest total nitrogen (TN) removal efficiency with SWW (pH 5). The TN removal efficiency with SWW (pH 8) under the lowest organic loading of 0.13 kg BOD5/m3-d was only 22.1±10.2%, while it increased to 35.4±1.0% for SWW (pH 5).

Application of electrooxidation process for treating concentrated wastewater from distillery industry with a voluminous electrode

Experiments in a laboratory scale were carried out to reduce color and chemical oxygen demand (COD) in distillery wastewater by using electrooxidation processes. A cylindrical electrochemical reactor constructed in an axial configuration with 0.2 m diameter and 0.35 m height was employed in this study. Two materials including graphite particles and titanium sponge were used as the voluminous anodes. A cathode made from Ti/RuO 2 was placed 0.04–0.05 m above the upper level of anode particles. Effect of parameters including initial pH of wastewater (1–5), time of dilution, current intensity (1–10 A), type of additive (H 2O 2 and NaCl), and additive concentration were investigated. The results indicated that the anode made from titanium sponge showed a higher potential to treat wastewater than the another one. The treatment in acidic condition ( pH = 1 ) provided the maximum oxidation of organic pollutants in wastewater. The presence of additives can promote the reduction of COD and color in wastewater approximately 89.62% and 92.24%, respectively. The maximum current efficiency was reached at the first 30 min and decreased slightly as electrolysis time proceeded due to the formation of passivation on the electrode surface. The energy consumption was obtained in the range of 2.82–4.83 kWh/kgCOD or 24.08–28.07 kWh/m 3 wastewater depending upon the concentration of additive. The kinetics of COD reduction was the pseudo first-order reaction with a fast rate constant of 6.78 min −1.

An inoculum for the aerobic treatment of wastewaters with high concentrations of fats and oils

Biodegradation of fats and oils in wastewaters has a potential role in wastewater management and water pollution control. Several enzymes and microorganisms are being exploited to carry out these processes. In the course of our work to design a system for treating wastewater with high concentrations of fats and oils, we developed an inoculum with high fat- and oil-degrading activities. The inoculum (designated as the JAT inoculum) was a mixed-culture of 15 bacterial isolates from various fatty wastewater samples, all isolates with a well-demonstrated ability to degrade fats and oils. Many of them could also quickly liquefy 12% gelatin and some could hydrolyse starch. The inoculum was effective in wastewaters with pH ranging from 4.5 to 9.5, but an optimum initial wastewater pH was in the alkaline range. The observed optimum treatment temperature when using the inoculum was 20–25°C, but activities occurred within the range of 8 to 42°C. Characteristics of the isolates suggested that there were no pathogenic species present. Biodegradative tests with the inoculum on samples of eight different fats and oils showed that several fats and oils could be degraded by the organisms in the culture. The inoculum is potentially useful for treating wastewaters containing fats and oils from both plant and animal origins.

Lumped kinetic model for catalytic wet oxidation of organic compounds in industrial wastewater

AbstractA simplified reaction pathway was proposed to describe the kinetic behavior of catalytic wet oxidation of organic mixture. The oxidation reactions were divided and lumped into two groups: (1) the deep or complete oxidation reactions with formation of CO2 and H2O; (2) the partial oxidation reactions with formation of all intermediates in aqueous solution of the industrial wastewater. The concentrations of all reactants in wastewater and those of the intermediates formed during the reaction are also represented by a lumped concentration of total organic carbon (TOC). To test the model, catalytic oxidation of organic pollutants in an effluent from a softwood Kraft pulp mill was investigated in a slurry reactor using a Pd‐Pt/Al2O3 catalyst. Sodium hydroxide was used to adjust the initial pH of wastewater to 7.3 to avoid the problem of metal leaching and excessive corrosion. The lumped kinetic model developed in this study describes well both our experimental data and those reported in literature. The lumped kinetic model proposed in this study can be used for both catalytic and noncatalytic wet oxidation processes.

Treatment of high-strength industrial wastewater by wet air oxidation—A case study

Treatment of high concentration chemical wastewater obtained from a petrochemical company by wet air oxidation (WAO) is studied. Experiments were conducted to investigate the effects of the mixer speed, operating pressure, initial pH of wastewater and temperature on the pollutant (chemical oxygen demand or COD) removal. Both air and oxygen were tested to determine their respective effect on the COD removal. Results showed that over 50% of COD removal can be easily realized in an hour of WAO treatment. Also considered in the present study was the catalytic WAO treatment of the high concentration wastewater. Copper sulfate (CuSO 4), cobalt oxide (Co 2O 3) and zinc oxide (ZnO) were employed as the catalysts. The COD removal efficiency of the catalytic WAO process was found to vary significantly with the catalyst utilized with CuSO 4 being the most effective.

Treatment of desizing wastewater by wet air oxidation

Treatment of desizing wastewater, a typical high strength industrial wastewater, by wet air oxidation (WAO) is investigated. The desizing wastewater sample was obtained from a large textile dyeing and finishing plant. Experiments were conducted to examine the effects of the initial pH of wastewater, operating pressure, gas flow rate and temperature on the pollutant (chemical oxygen demand or COD) removal. Both air and pure oxygen were tested to determine their respective effect on the COD removal. It was found that over 60% COD removal efficiency can be easily realized in an hour of WAO treatment of the wastewater. Also observed in the present investigation was that the WAO process was able to considerably elevate the biodegradibility of the treated desizing wastewater and thus rendering it suitable for subsequent activated sludge treatment.