Degradation of 2, 4, 6-trinitotoluene in aqueous solution by ozonation and multi-stage ozonation biological treatment

The objective of this study was to explore the extent of 2,4,6-trinitrotoluene synthetic solution and red water mineralization by comparing conventional direct ozonation and multi-stage ozonation-biological treatment process. The alkaline hydrolysis was used for remediation 2, 4, 6-trinitrotoluene and red water at pH = 10.9. Nevertheless, the hydroxyl radicals would be generated by ozone decomposition with ozone dose of 0.177 g/L. The samples were subjected to chemical oxygen demand and total organic carbon analysis to monitor pollutants removal. The rate of 2, 4, 6-trinitrotoluene and red water pollutants degradation were quantified using high performance liquid chromatography. 2, 4, 6-trinitrotoluene synthetic solution resulted 55.5 % chemical oxygen demand removal by 3 h direct ozonation. Following direct ozonation the biological treatment twenty four hours chemical oxygen demand reached 98.9 % and 98.7 % removal using humic acid and river water 1 % ( v/v) inoculation singly and respectively. Conventional direct ozonation showed non significant change in total organic carbon degradation. While on using multi-stage ozone-biological treatment process where humic acid and/or river water were used as inoculums singly and respectively, total organic carbon fulfilled 73 % and 98.3 % removal. The process was one hour direct ozonation and followed by three days multi-stage ozone-biological treatment. In multi-stage ozone-biological treatment process, ozonation was effective to decompose total organic carbon and to produce biodegradable dissolved organic carbon easily removed by ozone oxidation up to 98.3 % in 2,4,6-trinitrotoluene synthetic solution. Pollutants removal achieved 99 % in authentic red water effluent using river inoculation 1 % (v/v) in 5 days. Nuclear Magnetic Resonance and Fourier Transformation Infra Red methods were performed to confirm types of pollutants content in red water.     

Removal of Congo red from textile wastewater by ozonation

Congo red, which has a complex molecular structure with various diazo aromatic groups, is widely used in textile industry as an anionic dye. The purpose of this study was to investigate the degradation of Congo red in laboratory solution which had the chemical properties of the rinse waters of textile manufacturing dye-houses and the samples with Congo red alone wastewater by ozonation and to optimize the reaction parameters such as pH and time which influence the efficiencies of total organic carbon, total kjeldahl nitrogen and chemical oxygen demand removal. Ozonation of Congo red dye were carried out in a semi-batch reactor with constant ozone flow rate and concentration of 23 mL/sec and 13.6 mg/L, respectively. Decolorization was complete within a few minutes of ozonation possibly due to the cleavage of chromophore groups. It was observed that its structural destruction occurs predominantly at higher pHs. The reduction of chemical oxygen demand and destruction of the dye was more than 60 % and 42 %, respectively. Total kjeldahl nitrogen removal was accompanied by slight changes in nitrogen oxides. It can be deduced from the experimental results that: (a) the mineralization is very weak; (b) the reaction follows the indirect mechanism; i.e., the interaction of hydroxyl radicals with the dye and (c) the nitrification is rather predominant. Biological oxygen demand is declined in simulated alkalic and neutral samples respectively. At 13.6 mg O₃/L, the biological oxygen demand levels were significantly enhanced. This might be attributable to the enhancement of its biodegradation at alkaline pHs.     

Treatment of vegetable oil mill effluent using crab shell chitosan as adsorbent

In this study, a naturally available crab shell chitosan of low molecular weight (20?kDa) has been used as adsorbent to evaluate the pollution load in vegetable oil mill effluent. A series of batch experiment was conducted by varying chitosan dosage (100?C400?mg), pH (2?C9), stirring time (15?C90)?min and agitation speed (25?C150?rpm) to study their effects on adsorption and flocculation processes. The parameters considered for adsorption study are chemical oxygen demand, total suspended solids, electrical conductivity and turbidity. The maximum reduction in chemical oxygen demand, total suspended solids, electrical conductivity and turbidity is 74, 70, 56 and 92?% , respectively. The observed experimental result showed that crab shell chitosan could able to reduce significantly the chemical oxygen demand, turbidity, electrical conductivity and suspended matter. The optimum conditions were estimated as 400?mg/l chitosan, pH 4 and 45?min of mixing time with mixing speed of 50?rpm. Chitosan showed very good pollution removal efficiency and can be used for the effective treatment of vegetable oil mill effluent.     

Effect of leachate loading rate and incubation period on the treatment efficiency by T. versicolor immobilized on foam cubes

This study focuses on treatment of landfill leachate in column experiments by immobilized Trametes versicolor on polyurethane foam, collected from Nonthaburi landfill site, Thailand. In this study, glucose was used as a co-substrate. The effect of biomass growth on color removal was observed by immobilizing fungi on polyurethane foam. The same immobilized fungi were used for four cycles of 5 days each to find the reuse of fungi. Leachate was diluted to see the effect of organic loading on color removal. At optimum pH of 4 and in 20 days with 3 g/L of glucose, the fungi could decolorize 78 % and 63 % for 5-times dilution and concentrated leachate, respectively, using immobilized fungi after 4 days initial growth. Fungi could also reduce biological oxygen demand and chemical oxygen demand of 52 % and 42 % (with initial biological oxygen demand and chemical oxygen demand of 48,900 and 96,512 mg/L), respectively, with glucose 3 g/L in concentrate leachate and with 4 days initial immobilization of fungi on polyurethane foam. About 1–6% higher color removal was observed on day 20 with 15 days fungi immobilization initially as compared to 4 days immobilization. Higher removal efficiency was observed for the same leachate after dilution due to reduction in organic loading. Addition of co-substrate enhances significantly removal of color, biological oxygen demand and chemical oxygen demand. Chemical oxygen demand removal reached to 0.6 mg/mg of biomass with the co-substrate. Therefore, white rot fungi can be considered as potentially useful microorganisms in landfill leachate treatment.     

天然水镁石及其煅烧产物对臭氧化降解水中苯酚的效果研究

为有效去除工业废水中的苯酚,本文结合臭氧化技术,引入天然碱性矿物水镁石及其煅烧产物氧化镁作为催化剂,进行了催化臭氧化处理水中苯酚的研究。结果表明,加入的两种碱性矿物对臭氧化降解苯酚都有显著的催化效果。同时,碱性矿物的加入明显的改变了臭氧化过程中水体的pH值,从而对促进苯酚的降解起到了主导作用;除此之外,吸附实验及改变催化剂加入量的实验表明,碱性矿物表面对羧酸的吸附作用在一定程度上也导致苯酚降解效率的提高。本文工作为臭氧化降解水中苯酚提供了一种简便实用的处理方法,同时为天然水镁石矿物找到了新的应用领域。     

A coupled ozonation–electrooxidation treatment for removal of bisphenol A,nonylphenol and triclosan from wastewater sludge

Organic emerging micropollutants are persistent during the biological process used in treatment plants and have the tendency to accumulate in the sludge. Since a common method of final sludge disposal is the land application, there are potential risks associated with the presence of contaminants within the sludge. In this work, the removal efficiency of endocrine-disrupting chemicals, namely bisphenol A, nonylphenol and triclosan from sludge was investigated using ozonation and electrooxidation using boron-doped diamond electrodes. Both procedures were studied to determine the optimal conditions (pH, current density and ozone flow) for removing these chemicals in an hour. With the obtained conditions, a coupled system ozonation–electrooxidation was used with the goal to have better pollutant elimination. Results indicate that these compounds could be effectively removed by the coupled system; the diminutions were Bisphenol A 86%, nonylphenol 68% and triclosan 67%. Also improvements in the quality of aqueous phase were obtained, and for instance, the chemical oxygen demand, color and turbidity, were abated in 62, 61 and 66%, respectively. Moreover, an additional advantage of the coupled system is the absence of any secondary pollution.     

臭氧化含苯酚污水投加水镁石沉淀出草酸镁的实验研究

本文通过两组不同水镁石-苯酚投料比的实验,研究固体沉淀物与水质变化的关系。实验显示,水镁石解离出的Mg²⁺与苯酚降解的中间产物能形成难溶盐,并发生沉淀分离,促进含苯酚废水臭氧化降解的效率。当苯酚的初始浓度为47 g/L,初始碳镁原子比(C/Mg)为30时,经3小时充分臭氧化曝气后,投加的水镁石全部耗尽。XRD、TG/DSC结果显示新形成的沉淀物为草酸镁。反应终点的pH值在4以下,TOC去除率为40%。当体系的初始C/Mg(原子比)为1,苯酚的初始浓度为1.5 g/L时,同样的臭氧化曝气过程体系残留的沉淀物仍是水镁石。反应终点的pH值在10左右,TOC去除率为92.8%。研究证明,苯酚臭氧化过程也是体系酸化的过程,至少在高C/Mg比条件下新生的质子能与水镁石解离出的羟基中和,水镁石解离出的Mg²⁺可与草酸根结合沉淀出草酸镁。     

Ecological characteristics of Vrishabhavathy River in Bangalore (India)

River Vrishabhavathy, a tributary of Cauvery River was studied for 12 physico-chemical parameters at four sites over a distance of 50 km for a period of 2 years (1999–2001) at monthly intervals. Water was faintly alkaline, with pH showing negative correlation with temperature. The dissolved oxygen content increased downstream with negative correlation to biological oxygen demand (BOD), chemical oxygen demand (COD) and turbidity. Bicarbonate alkalinity was very low compared with carbonate alkalinity. Carbonate alkalinity, total hardness, total dissolved solids, total suspended solids, electrical conductivity, BOD and COD decreased downstream, with an upward trend in the middle reaches due to the introduction of raw sewage. The seasonal and yearly trends are also discussed. The river is a sewer collector undergoing self-purification.     

Preservation of thermophilic mixed culture for anaerobic palm oil mill effluent treatment by convective drying methods

The generation of huge amount of liquid waste known as palm oil mill effluent is a major problem in oil palm industry. Meanwhile, anaerobic biodegradation of such organic effluent at thermophilic condition is a promising treatment technology due to its high efficiency. However, storage and transportation of thermophilic mixed culture sludge are challenging due to constant biogas generation and heating requirement. Hence, drying of thermophilic sludge was conducted to obtain dormant thermophiles and thus enables easier handling. In this study, thermophilic sludge was dried using heat pump at 22 and 32 °C as well as hot air oven at 40, 50, 60, and 70 °C. Subsequently, quality of dried sludge was examined based on most probable number enumeration, chemical oxygen demand, and methane yield. Average drying rate was found to increase from 3.21 to 17.84 g H₂O/m² min as drying temperatures increases while average moisture diffusivity values ranges from 5.07 × 10^?9 to 4.34 × 10^?8 m²/s. Oven drying of thermophilic mixed culture resulted in highest chemical oxygen demand removal and lowest log reduction of anaerobes at 53.41% and 2.16, respectively, while heat pump drying resulted in the highest methane yield and lowest log reduction of methanogens at 53.4 ml CH₄/g COD and 2.09, respectively. To conclude, heat pump at 22 °C was most suitable drying technique for thermophilic mixed culture as the original methane-producing capability was largely retained after drying, at a slightly lower yet still comparable chemical oxygen demand removal when palm oil mill effluent was treated with the rehydrated culture.     

Influence of operating parameters on treatment of egg processing effluent by electrocoagulation process

The treatment of egg processing effluent was investigated in a batch electrocoagulation reactor using aluminum as sacrificial electrodes. The influence of operating parameters such as electrode distance, stirring speed, electrolyte concentration, pH, current density and electrolysis time on percentage turbidity, chemical oxygen demand and biochemical oxygen demand removal were analyzed. From the experimental results, 3-cm electrode distance, 150 rpm, 1.5 g/l sodium chloride, pH of 6, 20 mA/cm² current density, and 30-min electrolysis time were found to be optimum for maximum removal of turbidity, chemical oxygen demand and biochemical oxygen demand. The removal of turbidity, chemical oxygen demand and biochemical oxygen demand under the optimum condition was found to be 96, 89 and 84 %, respectively. The energy consumption was varied from 7.91 to 27.16 kWh/m³, and operating cost was varied from 1.36 to 4.25 US $/m³ depending on the operating conditions. Response surface methodology has been employed to evaluate the individual and interactive effects of four independent parameters such as electrolyte concentration (0.5–2.5 g/l), initial pH (4–8), current density (10–30 mA/cm²) and electrolysis time (10–50 min) on turbidity, chemical oxygen demand and biochemical oxygen demand removal. The results have been analyzed using Pareto analysis of variance to predict the responses. Based on the analysis, second-order polynomial mathematical models were developed and found to be good fit with the experimental data.     

Effect of sludge pretreatment on the performance of anaerobic/ anoxic/ oxic membrane bioreactor treating domestic wastewater

In the present study, two bench-scale anaerobic/ anoxic/ oxic submerged membrane bioreactors were used to study the effect of thermochemical sludge disintegration system on the excess sludge production. Among the two membrane bioreactors, one was named experimental membrane bioreactor and another one was named as control membrane bioreactor, where a part of the mixed liquor was treated with thermo chemical and was returned back to membrane bioreactor. Thermo chemical digestion of sludge was carried out at fixed pH (11) and temperature (75 °C) for 24 % chemical oxygen demand solution. The other one was named control membrane bioreactor and was used as control. The reactors were operated at three different mixed liquor suspended solids range starting from 7500 mg/L to 15000 mg/L. Both of membrane bioreactors were operated at a flux of 17 LMH over a period of 240 days. The designed flux was increased stepwise over a period of one week. During the 240 days of reactor operation, both of membrane bioreactors maintained relatively constant transmembrane pressure. The sludge digestion had no impact on chemical oxygen demand removal efficiency of the reactor. The results based on the study indicated that the proposed process configuration has potential to reduce the excess sludge production as well as it didn’t deteriorate the treated water quality.     

Treatment of poultry slaughterhouse wastewater in upflow anaerobic filter under low upflow velocity

The wastewater discharged by poultry slaughterhouse industries are characterized mainly by high biochemical oxygen demand, high suspended solids and complex mixture of fats, proteins and fibers requiring systematic treatment prior to disposal. In this study, the performance of an upflow anaerobic filter reactor for treating Indian poultry slaughterhouse wastewater under low upflow velocity of 1.38 m/day at mesophilic temperature (29-35 °C) was investigated. The reactor was inoculated with anaerobic non-granular sludge from an anaerobic reactor treating the poultry slaughterhouse wastewater. The reactor took 147 days for complete start-up with removal efficiencies of total chemical oxygen demand and soluble chemical oxygen demand of 70 and 79 % respectively. The maximum total chemical oxygen demand removal efficiency of 78 % was achieved at an organic loading rate of 10.05 kg/m³/day and at an hydraulic retention time of 12 h. The average methane content varied between 46 and 56 % and methane yield at maximum removal efficiency was 0.24 m³ CH₄/kg COD_removed·day. Sludge granules of 1–2 mm were observed in between the packing media. Scanning electron microscope analysis revealed that sludge granules are composed of clumps of Methanosarcina clustered with less intertwined Methanosaeta fibre of granules. The lower velocity used in this study has achieved better performance of the reactor by creating active microbial formation with stable pH upto an organic loading rate of 14.3 kg/m³/day. This has proved that the poultry slaughterhouse wastewater can be treated using anaerobic filter reactor under low upflow velocity.     

Effect of Fenton process on treatment of simulated textile wastewater: optimization using response surface methodology

A large portion of water is consumed during various textile operations thereby discharging wastewaters with pollutants of huge environmental concern. The treatment of such wastewaters has promising impact in the field of environmental engineering. In this work, Fenton oxidation treatment was engaged to treat simulated textile wastewater. Box–Behnken design and response surface methodology were employed to optimize the efficiency of Fenton process. Iron dose, peroxide dose and pH were considered as input variables while the responses were taken as chemical oxygen demand and color removal. A total of 17 experiments were conducted and analyzed using second-order quadratic model. The quadratic models generated for chemical oxygen demand and color removal efficiencies were validated using analysis of variances, and it was found that the experimental data fitted the second-order model quite effectively. Analysis of variances demonstrated high values of coefficient of determination (R ²) for chemical oxygen demand and color removal efficiencies with values of 0.9904 and 0.9963 showing high conformation of predicted values to the experimental ones. Perturbation plots suggested that the iron dosage produced the maximum effect on both chemical oxygen demand and color removal efficiencies. The optimum parameters were determined as Fe²⁺ dose—550 mg/L, H₂O₂ dose—5538 mg/L, pH—3.3 with corresponding chemical oxygen demand and color removal efficiencies of 73.86 and 81.35%. Fenton process was found efficient in treatment of simulated textile wastewater, and optimization using response surface methodology was found satisfactory as well as relevant. From the present study, it can also be concluded that if this method is used as pretreatment integrated with biological treatment, it can lead to eco-friendly solution for treatment of textile wastewaters.     

氧化铁矿物催化分解苯酚的动力学速率及其产物特征

本文研究了针铁矿、纤铁矿、赤铁矿和磁铁矿在过氧化氢参与下催化分解苯酚的动力学速率与溶液pH值的关系,并用紫外吸收谱测定了反应产物的谱学特征。结果表明,纤铁矿反应体系催化分解苯酚的速率常数(k)最大,其余依次为磁铁矿、针铁矿和赤铁矿。在纤铁矿反应体系中又以pH=3.8时反应速率常数最大。除赤铁矿反应体系外,当溶液pH=3~4时苯酚被完全分解,并有50%~65%的有机碳(TOC)被矿化。在pH=3.25的赤铁矿反应体系中,苯酚大多仅被转化为多酚,小部分苯环被打开形成己烯酸。当溶液pH=4~5时,苯酚一般仅被转化为多酚类化合物,但TOC基本不变。当溶液pH>5时,苯酚没有发生明显的转化和矿化现象。     

Enhanced bioremoval of refractory compounds from dyeing wastewater using optimized sequential anaerobic/aerobic process

The upflow anaerobic sludge blanket process followed by the biological aerated filter process was employed to improve the removal of color and recalcitrant compounds from real dyeing wastewater. The highest removal efficiency for color was observed in the anaerobic process, at 8-h hydraulic retention time, seeded with the sludge granule. In the subsequent aerobic process packed with the microbe-immobilized polyethylene glycol media, the removal efficiency for chemical oxygen demand increased significantly to 75 %, regardless of the empty bed contact time. The average influent non-biodegradable soluble chemical oxygen demand was 517 mg/L, and the average concentration in effluent from the anaerobic reactor was 363 mg/L, suggesting the removal of some recalcitrant matters together with the degradable ones. The average non-biodegradable soluble chemical oxygen demand in effluent from the aerobic reactor was 87, 93, and 118 mg/L, with the removal efficiency of 76, 74, and 67 %, at 24-, 12-, and 8-h empty bed contact time, respectively. The combined anaerobic sludge blanket and aerobic cell-entrapped process was effective to remove the refractory compounds from real dyeing wastewater as well as in reducing organic loading to meet the effluent discharge limits. This integrated process is considered an effective and economical treatment technology for dyeing wastewater.     

Fe/Ag催化臭氧氧化降解苯酚的研究

为研究双金属催化剂去除有机污染物的效果,采用自制Fe/Ag催化剂对模拟苯酚废水进行了臭氧催化氧化处理。通过扫描电子显微镜(SEM)、比表面积分析仪(BET)和X射线衍射(XRD)对催化剂进行表征,并考察了催化剂类型、催化剂投加量和溶液初始pH值对降解效果的影响规律。结果表明:与Fe相比,Fe/Ag比表面积减少了22.8%,在Fe/Ag/O₃与含苯酚废水的反应体系中,反应遵循臭氧直接作用和活性自由基(·OH、·O₂、H₂O₂)共同作用的机理;Fe/Ag在反应过程中体现出良好的协同作用;300 mg/L的苯酚模拟废水在pH=6.3、Fe/Ag投加量为1.00 g的最优反应条件下经60 min反应,苯酚与化学需氧量(COD)去除率比单独臭氧氧化分别提高了18.4%和29.4%。     

MnO2-UV联用光化学降解苯酚废水的初步研究

探讨了人工合成的高价锰氧化物与紫外光(UV)联用时降解苯酚废水的特性。结果表明,氧化锰矿物在无UV时对苯酚的降解能力差异大,1 g/L的氧化锰4 h对200 mg/L苯酚废水的降解率和COD去除率分别为:锰钾矿97.51%、酸性水钠锰矿89.07%、碱性水钠锰矿11.36%、钙锰矿9.67%;锰钾矿87.79%、酸性水钠锰矿53.11%、碱性水钠锰矿6.42%、钙锰矿1.43%。UV光照下,氧化锰矿物对苯酚的降解率有不同程度的提高,且表现出显著的表面光催化性质,增加了苯酚的深度降解,COD去除率显著提高。UV下氧化锰4 h对苯酚的降解率分别为:锰钾矿99.48%、酸性水钠锰矿91.86%、碱性水钠锰矿40.15%、钙锰矿35.95%);COD的去除率分别为:锰钾矿98.11%、酸性水钠锰矿68.45%、钙锰矿27.57%、碱性水钠锰矿24.27%。MnO2-UV联用时降解苯酚可能包括两种主要作用机制:氧化锰矿物的直接化学氧化降解和UV下MnO2的表面光催化降解。     

Microbial fuel cell operation using nitrate as terminal electron acceptor for simultaneous organic and nutrient removal

A double-chambered biocathode microbial fuel cell with carbon felt employed as electrodes was developed for wastewater treatment and bioelectricity generation simultaneously. The system was operated in fed-batch mode for over eight batches. The effect of circuit connections on organic and nitrate reduction was investigated. The maximum power density recorded was 21.97 mW/m² at current density of 88.57 mA/m². The Coulombic efficiency and internal resistance of the system were 5% and 100 Ω. Up to 89.9 ± 5.9% of chemical oxygen demand reduction efficiency achieved with an influent of 1123 ± 28 mg/L. There was no significant difference in the chemical oxygen demand reduction when system operated in either open or closed circuit. This study clearly showed that higher nitrate reduction efficiency obtained in closed circuit (74.7 ± 7.0%) due to bio-electrochemical denitrification compared to only 41.7% in the open circuit. The result also successfully demonstrated nitrate as terminal electron acceptor for the cathodic nitrate reduction.     

Treatment of polluted river water by a gravel contact oxidation system constructed under riverbed

The objective of this study was to evaluate the treatment efficiency of a gravel contact oxidation treatment system which was newly constructed under the riverbed of Nan-men Stream located at the Shin Chu City of Taiwan. The influent and effluent water samples were taken periodically for the analyses of pH, temperature, dissolved oxygen, total suspended solids, five-day biological oxygen demand, NH₄ ⁺-N. The results showed that the average removal rates of five-day biological oxygen demand, total suspended solids and NH₄ ⁺-N were 33.6% (between ?6.7% and 82.1%), 56.3% (between ?83.0% and 93.4%) and 10.7% (between ?13.0% and 83.3%), respectively. The calculated mean first order reaction rate constant for five-day biological oxygen demand was 4.58/day with a standard deviation of 4.07/day and for NH₄ ⁺-N was 2.15/day with a standard deviation of 5.68/day. Therefore, it could be said that this gravel-contact-oxidation system could effectively remove biological oxygen demand, total suspended solids, and NH₄ ⁺-N in river water at a relatively short hydraulic retention time, although its pollutant treatment efficiency was not quite stable. However, to reach better or more stable treatment efficiency, aeration might sometimes be necessary to increase the dissolved oxygen in influent river water. And, longer hydraulic retention time of the system might also be required to increase NH₄ ⁺-N removal efficiency.     

Systematic assessment of electrocoagulation for the treatment of marble processing wastewater

In this study, the treatability of marble processing wastewater by electrocoagulation using aluminum and iron electrodes was investigated. The sample used was from the marble-processing plant in Sivas and its turbidity, suspended solids, chemical oxygen demand and total solids concentrations were about 1,914?NTU, 2,904, 150 and 4,750?mg/L, respectively. The effects of various operating parameters such as initial pH, current density and electrolysis time on turbidity, suspended solids, chemical oxygen demand and total solids removal efficiencies were investigated. The settling characteristics of waste sludge produced and energy and electrode consumption were also determined. The optimum values of initial pH, current density and electrolysis time in electrocoagulation studies carried out using aluminum electrode were found to be 7.8, 30?A/m² and 5?min, respectively. Under these conditions, the removal efficiencies obtained for turbidity, suspended solids, chemical oxygen demand and total solids were 98.5, 99.2, 55.2 and 92.4?%, respectively. Corresponding energy and electrode consumptions were 0.143?kWh/kg SS and 0.010?kg Al/kg SS. For iron electrode, the optimum parameter values were found to be 7.8 pH, 20?A/m² and 5?min, respectively. Under these conditions, removal efficiencies for turbidity, suspended solids, chemical oxygen demand and total solids were determined as 94.3, 99.1, 54.2, and 96.1?%, respectively. Energy and electrode consumptions were 0.0571?kWh/kg SS and 0.0206?kg Fe/kg SS, respectively. Settling characteristics of sludge produced during experiments carried out using both aluminum and iron electrodes were fairly good. The results showed that electrocoagulation method can be used efficiently for the treatment of marble processing wastewater under proper operating conditions.