Assessment of electrocoagulation for the treatment of petroleum refinery wastewater

Batch electrocoagulation experiments were carried out to evaluate the removal of sulfate and COD from petroleum refinery wastewater using three types of electrodes: aluminum, stainless steel, and iron. The effects of current density, electrode arrangement, electrolysis time, initial pH, and temperature were investigated for two wastewater samples with different concentrations of COD and sulfate. The experimental results indicated that the utilization of aluminum, as anode and cathode, was by far the most efficient arrangement in the reduction of both the contaminants. The treatment process was found to be largely affected by the current density and the initial composition of the wastewater. Although electrocoagulation was found to be most effective at 25°C and a pH of 8, the influence of these two parameters on the removal rate was not significant. The results demonstrated the technical feasibility of electrocoagulation as a possible and reliable technique for the pretreatment of heavily contaminated petroleum refinery wastewater.     

Electrocoagulation of palm oil mill effluent as wastewater treatment and hydrogen production using electrode aluminum

Palm oil mill effluent (POME) is highly polluting wastewater generated from the palm oil milling process. Palm oil mill effluent was used as an electrolyte without any additive or pretreatment to perform electrocoagulation (EC) using electricity (direct current) ranging from 2 to 4 volts in the presence of aluminum electrodes with a reactor volume of 20 L. The production of hydrogen gas, removal of chemical oxygen demand (COD), and turbidity as a result of electrocoagulation of POME were determined. The results show that EC can reduce the COD and turbidity of POME by 57 and 62%, respectively, in addition to the 42% hydrogen production. Hydrogen production was also helpful to remove the lighter suspended solids toward the surface. The production of Al(OH)XHO at the aluminum electrode (anode) was responsible for the flocculation-coagulation process of suspended solids followed by sedimentation under gravity. The production of hydrogen gas from POME during EC was also compared with hydrogen gas production by electrolysis of tap water at pH 4 and tap water without pH adjustment under the same conditions. The main advantage of this study is to produce hydrogen gas while treating POME with EC to reduce COD and turbidity effectively.     

The removal of lignin and phenol from paper mill effluents by electrocoagulation

This study aims to investigate the treatment of paper mill effluents using electrocoagulation. Removal of lignin, phenol, chemical oxygen demand (COD) and biological oxygen demand (BOD) from paper mill effluents was investigated at various current intensities by using different electrodes (Al and Fe) and at various electrolysis times (1.0, 2.5, 5.0 and 7.5min). It was observed that the experiments carried out at 12V, an electrolysis time of 2min and a current intensity of 77.13mA were sufficient for the removal of these pollutants with each electrode. The removal capacities of the process using an Al electrode were 80% of lignin, 98% of phenol, 70% of BOD, and 75% of COD after 7.5min. Using an Fe electrode the removal capacities were 92%, 93%, 80% and 55%, respectively. In addition, it was found that removal of lignin, phenol, BOD and COD increased with increasing current intensity. In the experiments carried out at different current intensities, higher removal can be explained through a decrease in intra-resistance of solution and consequently an increase at the transfer speed of organic species to electrodes. It was also found that Al electrode performs higher efficiency than Fe electrode except for COD removal. However, the time required for removal of BOD was more than that of COD. The results suggest that electrocoagulation could be considered as an effective alternative to paper mill effluents treatment.     

Treatment of Agro‐Based Industry Wastewater by the Electro‐Oxidation Method: Comparative Results From Iron and Aluminum Metal Plate

Among the various technologies available to treat wastewater from sugar production, electro‐oxidation, or electrocoagulation, is considered one of the best. Moreover, it is a cost‐effective method. Although it is considered an advanced form of chemical coagulation, it does not require the addition of chemical coagulants, as the coagulant is generated through the dissolution of the sacrificial anodes that are connected to the electric current in the treatment chamber. This article examines how an electro‐oxidation system can be established and explores the variables that affect the process.     

Electrocoagulation of vegetable oil refinery wastewater using aluminum electrodes

Electrocoagulation with aluminum electrodes was used to treat the vegetable oil refinery wastewater (VORW) in a batch reactor. The effects of operating parameters such as pH, current density, PAC (poly aluminum chloride) dosage and Na(2)SO(4) dosage on the removal of organics and COD removal efficiency have been investigated. It has been shown that the removal efficiency of COD increased with the increasing applied current density and increasing PAC and Na(2)SO(4) dosage and the most effective removal capacity was achieved at the pH 7. The results indicate that electrocoagulation is very efficient and able to achieve 98.9% COD removal in 90 min at 35 mAcm(-2) with a specific electrical energy consumption of 42 kWh(kgCOD(removed))(-1). The effluent was very clear and its quality exceeded the direct discharge standard.     

Optimization of Fenton's oxidation of chemical laboratory wastewaters using the response surface methodology

Establishing a treatment process for practical and economic disposal of laboratory wastewaters has become an urgent environmental concern of the Department of Chemical Engineering of the Universidade Estadual de Maringá (State University of Maringá), Brazil. Fenton and related reactions are potentially useful oxidation processes for destroying toxic organic compounds in water. In these reactions, hydrogen peroxide is combined with ferrous or ferric iron in the presence or absence of light to generate hydroxyl radicals (.OH). The feasibility of Fenton's reagent to treat waste chemicals from an academic research laboratory was investigated in this study. A response surface methodology was applied to optimize the Fenton oxidation process conditions using chemical oxygen demand (COD) removal as the target parameter to optimize, and the reagent concentrations, as related to the initial concentration of organic matter in the effluent, and pH as the control factors to be optimized. Maximal COD removal (92.3%) was achieved when wastewater samples were treated at pH 4 in the presence of hydrogen peroxide and iron in the ratios [COD]:[H2O2]=1:9 and [H2O2]:[Fe2+]=4.5:1. Under these conditions, it was possible to obtain simultaneously maximal COD removal and minimal chemical sludge after treatment, which is a residue that needs further processing.     

A comparative study on cost analysis,efficiency, and process mechanism of effluent treatment plants in Bangladesh

Investigations were conducted into the treatment of effluents produced during manufacturing processes at both a chemicals production facility and a paint manufacturing facility. A comparison of costs of wastewater treatment at both facilities was also performed. The untreated effluents from both facilities were high in biological oxygen demand (BOD), chemical oxygen demand (COD), and total dissolved solids (TDS). In addition, the effluents from the two facilities deviated significantly in dissolved oxygen (DO) content and pH levels. However, both facilities ultimately released treated wastewater with allowable amounts or levels of BOD, COD, TDS, DO, and pH as permitted by the Department of the Environment, Ministry of Environment and Forests, Bangladesh (DOE). The effluent treatment plants (ETP) at both facilities contained combinations of chemical and biological treatment processes. The treatment processes used at the chemicals production facility and at the paint manufacturing facility were continuous and semi‐batch processes, respectively. The biological treatment section of the ETP at the chemicals production facility has both anaerobic and aerobic units, while the paint manufacturing facility has only an aerobic unit. Annual installation and operation costs of the ETP at the chemicals production facility was Bangladeshi Taka (Tk) 1,300,000 ($16,667 US dollars) and Tk 800,000 ($10,257), respectively. The annual installation and operation costs of the ETP at the paint manufacturing facility were Tk 3,050,000 ($39,103) and Tk 6,200,000 ($79,488), respectively.     

Preliminary evaluation of the electrochemical and chemical coagulation processes in the post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor

The main objective of this paper was to perform a preliminary comparative study between chemical and electrochemical coagulation processes, both followed by flocculation and sedimentation of an effluent from an upflow anaerobic sludge blanket (UASB) reactor treating simulated wastewater from an unbleached Kraft pulp mill. The electrochemical treatment removed up to 67% (with aluminum electrodes) and 82% (with stainless-steel electrodes) of the remaining chemical oxygen demand (COD) and 84% (stainless steel) and 98% (aluminum) of the color in the wastewater. These efficiencies were achieved with an energy consumption ranging from 14 to 20 Wh l(-1). The coagulation-flocculation treatment with ferric chloride and aluminum sulfate removed up to 87% and 90% of COD and 94% and 98% of color, respectively. The addition of a high molecular weight cationic polymer enhanced both COD and color removal efficiencies. The two post-treatment processes proved to be technically feasible; however the economical feasibility could not be assessed since the experiments were performed with small reactors that could distort scale factors.     

废旧铝、铁片粉煤灰复合混凝剂的制备及在废水处理中的应用

我国粉煤灰和铝、铁片固体废物产量日益增多,危害越来越严重。在高温加热、搅拌条件下,用强酸浸渍粉煤灰和易拉罐碎片,使粉煤灰和废旧铝、铁片资源化,制得废旧铝、铁片粉煤灰复合混凝剂,并用所制得的废旧铝、铁片粉煤灰复合混凝剂处理屠宰废水。在一定条件下,经混凝试验处理后的屠宰废水pH值在7左右,COD去除率为92．0％,SS去除率为98．7％,浊度去除率为98．4％,色度去除率为96．6％。结果表明,粉煤灰和废旧铝、铁片资源化和在废水处理中的应用具有可行性。     

Temperature and feed strategy effects on sulfate and organic matter removal in an AnSBB

The objective of this work was to analyze the interaction effects between temperature, feed strategy and COD/[SO(4)(2-)] levels, maintaining the same ratio, on sulfate and organic matter removal efficiency from a synthetic wastewater. This work is thus a continuation of Archilha et al. (2010) who studied the effect of feed strategy at 30 °C using different COD/[SO(4)(2-)] ratios and levels. A 3.7-L anaerobic sequencing batch reactor with recirculation of the liquid phase and which contained immobilized biomass on polyurethane foam (AnSBBR) was used to treat 2.0 L synthetic wastewater in 8 h cycles. The temperatures of 15, 22.5 and 30 °C with two feed strategies were assessed: (a) batch and (b) batch followed by fed-batch. In strategy (a) the reactor was fed in 10 min with 2 L wastewater containing sulfate and carbon sources. In strategy (b) 1.2 L wastewater (containing only the sulfate source) was fed during the first 10 min of the cycle and the remaining 0.8 L (containing only the carbon source) in 240 min. Based on COD/[SO(4)(2-)] = 1 and on the organic matter (0.5 and 1.5 gCOD/L) and sulfate (0.5 and 1.5 gSO(4)(2-)/L) concentrations, the sulfate and organic matter loading rates applied were 1.5 and 4.5 g/L.d, i.e., same COD/[SO(4)(2-)] ratio (=1) but different levels (1.5/1.5 and 4.5/4.5 gCOD/gSO(4)(2-)). When reactor feed was 1.5 gCOD/L.d and 1.5 gSO(4)(2-)/L.d, gradual feeding (strategy b) showed to favor sulfate and organic matter removal in the investigated temperature range, indicating improved utilization of the electron donor for sulfate reduction. Sulfate removal efficiencies were 87.9; 86.3 and 84.4%, and organic matter removal efficiencies 95.2; 86.5 and 80.8% at operation temperatures of 30; 22.5 and 15 °C, respectively. On the other hand, when feeding was 4.5 gCOD/L.d and 4.5 gSO(4)(2-)/L.d, gradual feeding did not favor sulfate removal, indicating that gradual feeding of the electron donor did not improve sulfate reduction.     

粉煤灰处理印染废水的现状及分析

本文综述了粉煤友在印染废水中的应用。粉煤灰作为吸附剂可直接处理印染废水，处理效率较低，改性后粉煤灰可提高吸附性；利用粉煤灰的混凝作用对COD的去除率一般为50％-60％，色度去除率为80％左右；当粉煤灰与铁屑产生电化学作用时，用于印染废水预处理是行之有效的；作为印染废水助凝助沉剂，结合其他工艺，可使印染废水中COD和色度去除率分别达到90％和95％以上，并列举了粉煤灰处理印染废水成功的实例。但仍应加强理论研究，解决工程与设备问题是今后的工作方向。     

三维电极电解硝基苯废水处理实验研究

以涂膜活性炭-活性炭为填充粒子,对三维电极电解硝基苯废水进行了研究。通过实验探讨了投盐量、槽电压、主电极间距、反应时间及初始浓度对电解硝基苯废水的影响。结果表明,三维电极在电极间距为9mm、槽电压为20V、硫酸钠投加量为1.5g/L、pH值为6、电解时间为90min的条件下,硝基苯去除率可达90%以上。在三维电极电解作用下,硝基苯转化为可生化和低毒的苯胺,苯胺在三维电极电解作用下还可以得到进一步的降解。     

铁屑微电解法处理光致抗蚀剂废水的初步研究

初步研究了铁屑微电解法处理先致抗蚀剂废水；对废水pH值、曝气、铁屑和活性炭的用量等作了单因素影响试验。正交试验结果表明：当铁屑投加量50．0g／L，活性碳投加量5．0g／L，废水pH值2．0，反应时间60min时，CODCr去除率达42％。     

UV/Fenton法处理高浓度香料废水的试验研究

研究了UV/Fenton法处理高浓度废水的新技术以及有关影响因素。试验:pH在2－4，COD／H2O2＝1：1.5,Fe^2 浓度为1.7g／L的条件下，反应时间90min，COD去除率可达99.6%。     

Remediation of biodiesel wastewater by chemical- and electro-coagulation: a comparative study

The remediation of biodiesel wastewater was carried out using chemical and electrochemical techniques. Initially the fatty acid methyl esters (FAME or biodiesel) and free fatty acids (FFA) were chemically removed from the wastewater using three types of mineral acids, H(2)SO(4), HNO(3) and HCl, at different pH values within the range of 1.0-8.0. Optimally, approximately 24.3 ml/l of FAME/FFA were removed from the wastewater when using H(2)SO(4) to set a final pH of 2.5 for 7 min. All pollutant levels were markedly reduced during this step. That is, approximately 38.94%, 76.32% and 99.36% of COD, BOD5 and oil & grease were respectively removed. The acidic aqueous phase left after the removal of the FAME/FFA phase was then treated by chemical- and electro-coagulation processes. The results demonstrated that both investigated treatment processes were effective for treating wastewater from a biodiesel production plant. The chemical coagulation provided a lower operating cost (1.11 USD/m(3)) compared with the electro-coagulation process (1.78 USD/m(3)). However, the latter process provided a better quality of wastewater compared with the former process, with the exception of the BOD levels.     

WATER RECLAMATION BY PHYSICOCHEMICAL TREATMENT OF WASTEWATER1

ABSTRACT. Treatment of a high strength acidic industrial chemical waste, which had a COD of about 3000 mg/1 and a pH of 3, was attempted by activated carbon adsorption to evaluate the feasibility of yielding effluents of reusable qualities. The experimental methods which were employed in this investigation included batch and column studies. The former was used to evaluate the rate and equilibrium of carbon adsorption while the latter was used to determine treatment efficiencies and performance characteristics. Parallel operations of fixed-bed and expanded-bed adsorbers were contrasted in the column study. Results of this investication indicate that activated carbon was very efficient in removing the COD of the chemical waste. Initial pH adjustments for the wastewater to 7.0 or 11.4 did not increase the COD removal efficiency. Turbidity and nitrogen (total Kjeldahl- and ammonia-N) were removed to some extents by the carbon bed adsorbers while phosphorus (total-and ortho-P) was totally unaffected by the carbon treatment.     

PERFORMANCE VARIATIONS OF COD AND NITROGEN REMOVAL BY VEGETATED SUBMERGED BED WETLANDS1

ABSTRACT: Vegetated submerged bed wetlands can supplement treatment of onsite wastewater systems. This study evaluated vegetation, media, and seasonal impacts on system performance in six meso scale rock plant filters with and without narrow leaf cattails (Typha augustifolia). Daily chemical oxygen demand (COD) reductions in planted cells averaged 85 percent and weekly total nitrogen (TN) reductions averaged 50 percent. Planted cells had 17 percent greater COD reduction and 76 percent greater TN reduction than unplanted cells, both significant differences. Media type affected COD reduction, particularly in unplanted cells. COD treatment in planted cells was highest for fine crushed limestone (87±13 percent) and least variable for coarse river gravel (85±11 percent). No significant difference in TN reduction was observed for different media types (48 to 51 percent range). Seasonal influences on treatment included a significant decrease during late fall and early spring and a significant increase with temperature. After a step increase in organic loading, treatment efficiency decreased sharply but returned to prior levels after an adaptation period of about one month. Planted cells not only exhibited higher treatment efficiency but also had a retarded organic matter breakthrough, appearing after three to seven times the period for a bromide tracer. This supports a hypothesis that retardation of contaminant movement through the treatment cells results in enhanced removal. These results support the use of rock plant filters, but demonstrate the need to account for performance variations in system design. (KEY TERMS: constructed wetlands; seasonal effects; subsurface flow; Typha augustifolia; onsite wastewater treatment; water quality.)     

Use of artificial neural network black-box modeling for the prediction of wastewater treatment plants performance

A reliable model for any wastewater treatment plant is essential in order to provide a tool for predicting its performance and to form a basis for controlling the operation of the process. This would minimize the operation costs and assess the stability of environmental balance. This process is complex and attains a high degree of nonlinearity due to the presence of bio-organic constituents that are difficult to model using mechanistic approaches. Predicting the plant operational parameters using conventional experimental techniques is also a time consuming step and is an obstacle in the way of efficient control of such processes. In this work, an artificial neural network (ANN) black-box modeling approach was used to acquire the knowledge base of a real wastewater plant and then used as a process model. The study signifies that the ANNs are capable of capturing the plant operation characteristics with a good degree of accuracy. A computer model is developed that incorporates the trained ANN plant model. The developed program is implemented and validated using plant-scale data obtained from a local wastewater treatment plant, namely the Doha West wastewater treatment plant (WWTP). It is used as a valuable performance assessment tool for plant operators and decision makers. The ANN model provided accurate predictions of the effluent stream, in terms of biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) when using COD as an input in the crude supply stream. It can be said that the ANN predictions based on three crude supply inputs together, namely BOD, COD and TSS, resulted in better ANN predictions when using only one crude supply input. Graphical user interface representation of the ANN for the Doha West WWTP data is performed and presented.     

臭氧氧化法处理印染废水

本实验通过印染废水处理装置的建立,研究了臭氧处理印染废水的消耗量与废水ＣＯＤ值变化、废水色度去除率的关系,,以及不同ｐＨ值的印染废水和臭氧处理时间的关系。实验结果表明：经过处理后废水的ＣＯＤ却除率为３３９％,色度去除率为９９９％。     

硫酸盐废水厌氧处理中限制因子的探讨

归纳分析了两种硫酸盐废水的厌氧处理相关的研究数据和结果，着重阐述了碳硫比值、硫酸盐负荷率、pH等因子对系统的影响。