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Colour and organic removal of biologically treated coffee curing wastewater by electrochemical oxidation method
Abstract
The treatment of biologically treated wastewater of coffee-curing industry by the electrochemical oxidation using steel anode was investigated. Bench-scale experiments were conducted for activated sludge process on raw wastewater and the treated effluents were further treated by electrochemical oxidation method for its colour and organic content removal. The efficiency of the process was determined in terms of removal percentage of COD, BOD and colour during the course of reaction. Several operating parameters like time, pH and current density were examined to ascertain their effects on the treatment efficiency. Steel anode was found to be effective for the COD and colour removal with anode efficiency of 0.118 kgCOD x h(-1) x A(-1) x m(-2) and energy consumption 20.61 kWh x kg(-1) of COD at pH 9. The decrease in pH from 9 to 3 found to increase the anode efficiency from 0.118 kgCOD x h(-1) x A(-1) x m(-2) to 0.144 kWh x kg(-1) of COD while decrease the energy consumption from 20.61 kWh x kg(-1) of COD to 12.86 kWh x kg(-1) of COD. The pH of 5 was considered an ideal from the present treatment process as it avoids the addition of chemicals for neutralization of treated effluents and also economical with respect to energy consumption. An empirical relation developed for relationship between applied current density and COD removal efficiency showed strong predictive capability with coefficient of determination of 96.5%.
... Any industrial scheme used to produce instant coffee generates wastewater with dark brown color and high organic load that presents a considerable level of contamination [3]. Its composition includes a mixture of complex substances such as polysaccharides, proteins, melanoidins, tannins (in low concentrations), alkaloids (as caffeine or trigonelline), and chlorogenic acids. ...
... However, an electrolyte with greater coagulation power is produced when the Fe 2+ ion change to Fe 3+ due in principle to its size (10-30 µm for Fe 3+ compared to 0.05-1 µm for Al 3+ ) and its high capacity for formation of insoluble hydroxides. Another aspect to take into account is that iron electrodes can add a pale color to treated water over time, due to the combination of Fe 3+ with hydroxyl group to form Fe(OH) 3 . ...
... This was probably due to the fact that most of the dissolved iron was converted to the ferric form (Fe 3+ ) whose coagulant power is greater than that of Al 3+ . Ferric ions stand out for being the precursors of hydrolyzed species that ultimately lead to the formation of insoluble compounds such as Fe(OH) 3 or FeOOH with high contaminant adsorption capacity. The highest %D COD was achieved with iron-iron or iron-graphite anode-cathode pairs. ...
In this study, an industrial wastewater from instant coffee production was treated by electrocoagulation (EC). The effect of various EC operating parameters, such as electrode type, current density, support electrolyte concentration and stirring velocity, were investigated to determine the optimal operating EC conditions. The scope of electrocoagulation (EC) was assessed, in environmental and economic terms, for the treatment of industrial wastewater originated from the production of instant coffee. The evaluation included the effect of EC operating factors (electrode type, current density, supporting electrolyte concentration and stirring velocity) on Color removal, COD and TOC degradation, toxicity, molecular weight distribution, as well as the total operating cost. The following optimal operating conditions were established through a series of preliminary experiments, a Box-Behnken design of experiments, Response Surface Methodology application, and multi-objective optimization analysis: the pair of Fe (anode)-stainless steel (cathode) electrodes, supporting electrolyte = 1.78 g of NaCl/L; current density = 150 A/m²; electrode gap = 3 mm; stirring velocity = 350 RPM; and pH0 = 4.7 (that of raw industrial effluent). Finally, the kinetic study allowed defining the electrolysis operation time of ca. 180 min required to comply with the maximum permissible discharge limits for the production of instant coffee the discharge of soluble coffee effluents, in terms of COD concentration, established by current Colombian legislation. The EC reached ca. 97% decolorization, as well as 72% and 65% of COD and TOC removal degradation, respectively, with total operating costs of 6.26 USD/m³. This yielded an oxidized (COS = 2.87), biocompatible (BOD5/COD = 0.437) and non-toxic effluent, free of contaminants with molecular weight > 30 kDa. The EC appeared as an effective alternative for the treatment of industrial wastewater from the production of instant coffee within the framework of different Sustainable Development Goals (number 6 (Clean water and sanitation), number 7 (Clean and affordable energy), number 9 (Industry, innovation and infrastructure) and 13 (Climate action)).
... Hydroxyl radicals can be also formed by electrolysis when liquid water becomes the agent for oxidizing or reducing a chemical substance. It is known [9] that the electrochemical oxidation by steel anode is effective for degrading organics into aqueous solutions. ...
... The non-stoichiometric states of liquid water: Fermi levels, F(8) and F(9) , are the confines of thermodynamic water stability defined by the half-reactions (8) and (9); the full blue lines denote occupied-by-electrons levels, 3 H O and OH , as hydroxide ions, OH -, and hydroxonium radicals, H3O; dotted blue lines denote the vacant ones for hydroxonium ions, H3O + , and hydroxyls, OH The population of energy levels, 3 H O and OH , by electrons and holes for these nonstoichimetric states is defined by data: [H3O + ] = [OHleft) and OH is mostly occupied by electrons as hydroxide ions since this Fermi level, F(9) , is essentially above OH . The variable Fermi level, F , in the band gap of liquid water is determined rigorously by the ratio of the species concentrations: [H3O + ]/[H3O] and [OH]/[OH -], as portions of vacant (H3O + , OH) and occupied-by-electrons (H3O, OH -) energy levels, 3 H O and OH , fixed in the band gap of liquid water. ...
... - F(8) = 0.219 eV and OH - F(9) = -0.302 eV for the two nonstoichiometric states, F(8) and F(9) , of liquid water as confines of its thermodynamic stability. From the well known requirement of F(8) - F(9) = 1.23 eV[19] (seefig. ...
A concept for electric converting a saline wastewater into basic solution (pH > 7) with a positive RedOx potential (alkaline anolyte) is considered. Such the medium can be obtained in situ at flowing wastewater via a special electrochemical cell with strongly polarized cathode (generating hydroxide anions) and quasi-equilibrium anode which intensively discharges hydroxide ions to hydroxyl radicals into the wastewater. The radicals will oxidize anions of strong acid and convert them into weak-acid micro precipitates in the flowing basic solution. These renewable nano-sorbents will uninterruptedly co-precipitate radioactive contamination from wastewater and be agglomerated as corrosion by-products in the felt-like
anode. The consideration of liquid water as a chemical compound with a wide band gap shows that the anolyte (as a hyper-stoichiometric water, H2O1+|x|) is a simple and effective tool for varying physical and chemical properties of the aqueous solution due to forced changing its RedOx potential as one needs. This potential as Fermi level in the band gap of liquid water is the most convenient parameter for monitoring and managing the electrochemical potential of the aqueous medium. Its hyper-stoichiometric state is realized when Fermi level is shifted to the top of a valence band. This electro-oxidized state as the alkaline anolyte is
characterized by an acceptor level, OH/OH^(–), partially occupied by electrons. Then, the hydroxyl radical (OH) as the strongest oxidizer will oxidize intensively the metal anode and renew its surface for great removal of radio-nuclides from the wastewater due to their large specific area of renewable surface of hydroxide absorber on the felt-like anode.
... Hydroxyl radicals can be also formed by electrolysis when liquid water becomes the agent for oxidizing or reducing a chemical substance. It is known [9] that the electrochemical oxidation by steel anode is effective for degrading organics into aqueous solutions. ...
... The non-stoichiometric states of liquid water: Fermi levels, F(8) and F(9) , are the confines of thermodynamic water stability defined by the half-reactions (8) and (9); the full blue lines denote occupied-by-electrons levels, The population of energy levels, left) and OH is mostly occupied by electrons as hydroxide ions since this Fermi level, F(9) , is essentially above OH .The variable Fermi level, F , in the band gap of liquid water is determined rigorously by the ratio of the species concentrations: [H 3 O + ]/[H 3 O] and [OH]/[OH -], as portions of vacant (H 3 O + , OH) and occupied-by-electrons (H 3 O, OH -) energy levels, 3 H O and OH , fixed in the band gap of liquid water. These proportions are given by Fermi-Dirac statistics which can be simplified to Maxwell-Boltzmann distribution of electrons and holes in the corresponding energy levels ...
A concept for electric converting a saline wastewater into basic solution (pH > 7) with a positive RedOx potential (alkaline anolyte) is considered. Such the medium can be obtained in situ at flowing wastewater via a special electrochemical cell with strongly polarized cathode (generating hydroxide anions) and quasi-equilibrium anode which intensively discharges hydroxide ions to hydroxyl radicals into the wastewater. The radicals will oxidize anions of strong acid and convert them into weak-acid micro precipitates in the flowing basic solution. These renewable nano-sorbents will uninterruptedly co-precipitate radioactive contamination from wastewater and be agglomerated as corrosion by-products in the felt-like anode. The consideration of liquid water as a chemical compound with a wide band gap shows that the anolyte (as a hyper-stoichiometric water, H2O1+|x|) is a simple and effective tool for varying physical and chemical properties of the aqueous solution due to forced changing its RedOx potential as one needs. This potential as Fermi level in the band gap of liquid water is the most convenient parameter for monitoring and managing the electrochemical potential of the aqueous medium. Its hyper-stoichiometric state is realized when Fermi level is shifted to the top of a valence band. This electro-oxidized state as the alkaline anolyte is characterized by an acceptor level, OH/OH^(–), partially occupied by electrons. Then, the hydroxyl radical (OH) as the strongest oxidizer will oxidize intensively the metal anode and renew its surface for great removal of radio-nuclides from the wastewater due to their large specific area of renewable surface of hydroxide absorber on the felt-like anode.
... The main mechanisms in electrochemical process are electrocoagulation, electroflotation and electrooxidation (Sheng and Peng 1994). Bejankiwar et al. (2003) studied about the separation of color and organic compounds from waste of coffee industries by electrochemical methods and showed that steel anodes are very useful in color and COD removing (Bejankiwar et al. 2003). The most important parameters affecting the performance of electrochemical process are: potential differences between anodes and cathodes electrodes, electrolysis time and pH of treated solution (Aleboyeh et al. 2008). ...
... The main mechanisms in electrochemical process are electrocoagulation, electroflotation and electrooxidation (Sheng and Peng 1994). Bejankiwar et al. (2003) studied about the separation of color and organic compounds from waste of coffee industries by electrochemical methods and showed that steel anodes are very useful in color and COD removing (Bejankiwar et al. 2003). The most important parameters affecting the performance of electrochemical process are: potential differences between anodes and cathodes electrodes, electrolysis time and pH of treated solution (Aleboyeh et al. 2008). ...
The industrial waste water is considered as a serious threat to environment. Industries with high pollution load of chemical oxygen demand (COD) and biological oxygen demand such as sugar industries has a major role in environmental pollution. The aim of this study was to investigate the treatment possibility of this wastewater by using the electrochemical method. For this purpose quality parameters such as COD, color, turbidity and total dissolved solids (TDS) were investigated. The decrease of color, turbidity COD and TDS from effluent has been investigated at different voltages (10.8, 16.3 and 27.9 V) and various electrolysis times (10, 25 and 40 min) by using different electrodes (Al, Fe) at 4 cm middle distance. Experimental results demonstrated that the electrochemical process by using electrocoagulation and flocculation mechanisms can decrease color, turbidity and COD to 90.8, 98.9 and 50.5 %, respectively. The electrochemical process increased in pH with no considerable effect on the TDS of the effluent by water reclamation on the cathode side. Results showed that electrochemical process without additives could eliminate greatly various containments of wastewater. Therefore, an appropriate method for treating of wastewater can be designed and implemented.
... Cardenas et al. (2009) used a dimensionally stable anode that is composed of titanium with a film of ruthenium, cobalt oxide and iridium to reduce the level of pollutant after pretreatment with coagulation/chemical flocculation. Bejankiwar et al. (2003) studied the removal of COD and color after biological pretreatment showing that steal anode was effective in removing COD in coffee wastewater. ...
Coffee is globally the second largest most traded commodity after petroleum, and this has facilitated many countries to grow and produce coffee in commercial quantity. The production processes uses large volume of water which comes out as contaminated water. The presence of toxic chemicals like tannins, phenolic and alkaloids inhibits biological degradation. Microbial processes break down the organic substances released into water bodies slowly, using up the oxygen from the water (COD). As demand for oxygen needed to break down organic waste in a wastewater begins to exceed supply, a decrease in oxygen needed to combine with chemicals (COD) slowly creates anaerobic condition. The review looks at few of the current methods (physicochemical and biological) used in coffee wastewater management, their advantages and disadvantages including, high cost implication, complex operation and more time consumption among others; furthermore, the review suggests ion exchange technique as a better alternative based on its capacity to act as both an ion exchanger and absorber.
... Regardless of the source of the vinasse, however, the removal efficiency is impacted to some degree by the negative effect of the organics present, especially polyphenolic compounds [13], on the microorganisms used in the biological treatment of vinasse. Various authors have suggested alternative methods and approaches based on a combination of biological and physicochemical methods that more efficiently purify vinasse and wastewater in general containing natural organic material (NOM) [9,10,12,[14][15][16][17][18][19]. ...
... Para ello es necesario implementar sistemas de tratamiento de los efluentes que sean adecuados para este propósito, que proporcionen una alta eficiencia, bajos costos y adicionalmente traiga ventajas ambientales. Dentro de las tecnologías para el tratamiento de aguas residuales se encuentran los procesos biológicos (Bejankiwar et al., 2003; Nugroho et al., 2010), procesos fisicoquímicos (), y de oxidación avanzada (Rivas et al., 2009). Entre los procesos fisicoquímicos se encuentra la coagulación-floculación, en el que utiliza sustancias químicas como el sulfato de aluminio, cloruro férrico, clohidróxido de polialuminio, policloruro de aluminio entre otros, este proceso es empleado para la remoción de color y la demanda química de oxígeno, las sustancias empleadas como coagulantes alteran el estado físico de los sólidos disueltos y suspendidos con la finalidad de eliminarse mediante el proceso de sedimentación (Zayas et al., 2007; Ahmad et al., 2005; Lee y Lim, 2005). ...
El objetivo de este trabajo fue la remoción de contaminantes de un efluente de aguas residuales municipales, mediante tratamientos fisicoquímicos de coagulación-floculación, sedimentación, filtración, oxidación química y desinfección en un tren de tratamiento en flujo continúo a 1.65 mL/s. Para el proceso de coagulación-floculación se utilizó una dosis de 1mL/L de Al2(SO4)3 0.01 M, los filtros fueron empacados de arena sílice natural y carbón activado proveniente de concha de coco, en el proceso de oxidación química se aplicó una concentración de 3 mg/L de ozono con un tiempo de contacto de 10 a 15 min, la desinfección se realizó mediante radiación ultravioleta a una longitud de onda de 253-260 nm. La remoción obtenida fue del 98% de color, 94% de turbiedad, 93% de DQO, 93% de DBO5, el 84 de SAAMS, el 63% de NH3, el 98% de coliformes totales y fecales.
... Since the late 1970s, electrochemical oxidation has been successfully applied to treatment of textile wastewater (Naumczyk et al., 1996), tannery wastewater (Rao et al. 2001), coke-plant wastewater (Chiang et al., 1995a), coffee curing wastewater (Bejankiwar et al., 2003), and other wastewaters containing cyanides (Lanza and Bertazzoli, 2002) and phenol (Canizares et al. 2002). Also, this process has been used for landfill leachate treatment over the past 10 years. ...
... The coffee industry wastewater needs attention and in regard to its pollutant behavior a cluster of methodologies like chemical flocculation, advanced oxidation processes [11], and electrochemical oxidation method [14] were applied to treat the coffee wastewaters. Recently, dark brown colored model coffee effluent was decolorized by photo-Fenton process [6]. ...
Aqueous coffee and tea infusions were decolorized by adsorption onto activated carbon. The color of the infusions has changed gradually from brown to colorless during the decolorization process. To understand the potentiality of activated carbon, experiments were conducted to determine equilibrium time, optimum dose of adsorbent, intraparticle diffusion, adsorption isotherm, optimum pH, and desorption of color from the coffee and tea infusions. The corresponding results show that around 80–82% of color removal was achieved with 100 mg/L of activated carbon within 2 h. The isothermal equilibrium sorption data fitted well into the Langmuir isotherm. Film diffusion seems to be the rate limiting step for coffee infusions but pore diffusion for tea infusions. The sorption process appears to follow anionic type as the extent of sorption is decreasing with increasing pH. Desorption studies revealed that the sorption interaction was more of chemical nature.
... In recent years, a credible amount of attention is drawn by food industry wastewater and in particular coffee industry effluents; as a result, a significant number of groups have studied the treatment of coffee wastewater for the reduction of COD [14] and color by processes other than biological. Color reduction from coffee wastewaters were studied by technologies like electrochemical oxidation [15], Photo-Fenton process [16], and coagulation/flocculation in conjunction with advanced oxidation processes [17]. Despite of higher efficiency in color reduction, the methods reported so far are cost-intensive, and hence, there is a necessity for cost-effective technologies. ...
The production and consumption of coffee and tea results in the generation of huge quantities of colored wastewaters, and these are accountable for certain problems like color, BOD, toxicity, and odor when discharged into the aquatic environment. In this study, the color from the aqueous infusions of coffee and tea was removed by chemical coagulation, using coagulants like ferrous sulfate, alum, and lime, and the chemical coagulation was also used for the evaluation of both the process efficiency and process parameters, such as pH, dose of coagulant, effect of coagulant type, etc. A coagulant dosage of 1.0 g L−1 was considered as appropriate, since a major amount (70–97%) of color removal was accomplished from different brands of coffee and tea infusions. Higher efficiency of decolorization was obtained from slightly acidic to neutral pH (4.0–6.0). Higher percentage of color removal was achieved from tea infusions compared with coffee infusions. Average color removal efficiencies of individual coagulants for coffee and tea infusions were compared in order to assess the overall efficiency of the coagulant toward the infusions. Ferrous sulfate is used as an effective coagulant for coffee with 74% removal of color, and lime is used for tea infusion with 88% removal of color. The color of the infusions has been reduced from brown and brownish red to relatively clear liquid to an extent that it can be released into the aquatic environment without any detrimental effect.
... In our previous studies, electrochemical technology was successfully applied for treatment of deproteinated whey wastewater (DWW) produced during cheese manufacture [19,20], fruit juice factory wastewater (FJW) [20], and beet sugar factory wastewater [21]. Nevertheless, there are few other studies dealing with electrochemical treatment of food-processing industrial wastewaters such as coke-plant wastewater [22], coffee curing wastewater [23], olive mill wastewater [24], starchy wastewater [25], distillery industry wastewater [26], beer brewery wastewater [27], and vinasse wastewater from beet molasses [28]. In an electrochemical treatment study for the agro-industry wastewaters, the efficiency of the electrocoagulation process in monopolar configuration in terms of COD removal was between 20 and 40% for the fruit beverage wastewater [29]. ...
Reaction kinetics during electrochemical treatment of deproteinated whey wastewater (DWW) and fruit juice factory wastewater (FJW) was investigated in a stirred batch electrochemical reactor under reaction conditions of 100% wastewater concentration and 11.29 V applied voltage at room temperature using cost-effective iron electrodes. Reaction mediums for electrochemical treatment of DWW and FJW were supplemented with 19.87 and 5.95 g L−1 NaCl as supporting electrolyte, respectively. Kinetic investigations denoted that reaction orders (n) of both reactions were 0.6. Specific reaction rate constants (k) at 25°C of electrochemical DWW and FJW treatment reactions were 0.04 and 1.21 mg0.6 L−0.6 min−1. Activation energies (Ea) and Arrhenius constants (A) were calculated as 41.60–9.59 kJ mol−1 and 740.93–61.82 mg0.6 L−06 min−1 for DWW and FJW, respectively. In our study, relatively fast reaction kinetics values were obtained compared to the data previously reported for electrochemical wastewater treatment in the literature. These results support the applicability of electrochemical treatment to the deproteinated whey and fruit juice factory wastewaters as an advanced post-treatment method providing further research.
... 1. Coffee curing waste water Bejankiwar et al. (2003) in Colour and organic removal of biologically treated coffee curing wastewater by electrochemical oxidation method investigated the treatment of biologically treated wastewater of coffee-curing industry by the electrochemical oxidation using steel anode. Bench scale testing was done for several operating parameters like time, pH and current density to ascertain their effects on the treatment efficiency. ...
... Similarly, in Chen et al [80] a novel composite reactor was prepared and studied towards the degradation of organic pollutants. In that study a UV lamp was installed in the reactor to provide energy to excite nano TiO 2 , which served as photocatalyst, leading to the production of hole-electron pairs, and a three-electrode electrolysis system was used to accumulate H 2 O 2 , which played an important role in the degradation process. ...
Environmental pollution has been a major problem worldwide. This makes environmental pollution control an important ingredient to healthy environment. During the last few years, water has become an increasingly important issue in developing nations. Progress in health and education is dependent on access to affordable sanitation and safe water. Children, most especially (girls) educational prospects are similarly constrained. Public health systems are over-burdened by diarrheal diseases- the United Nation says that at anyone time; half the hospital beds in the developing world are occupied by patients suffering from diarrhea and other water related ailments. The poor lack social adaptive capacity, which suggests that development of water sector through soil and water pollution control is most pertinent to poverty alleviation. It is a well known knowledge that in environmental pollution controls through soil and wastewaters treatment, electrochemical treatment processes have been promising techniques.
This chapter presents a review of over 110 articles on designs, models and applications of electrochemical processes from 1973 – 2004 with a particular attention to removal of environmental pollutants such as oil and grease, lead, cadmium, organic compounds etc. It was concluded that electrochemical treatment techniques have a wider range of applications such as direct , indirect with photo or solar cell, bio-electrochemical, electroxidation and many others.
... In recent years, there has been a growing interest in the treatment of industrial effluents by electrochemical methods. Many researchers had investigated the electrochemical oxidation for the treatment of various types of wastewater containing phenol (Maa et al., 2009), pentachlorophenol (Upendra et al., 2008), tannery (Rao et al., 2001), olive mill (Canizares et al., 2006), coffee curing (Bejankiwar et al., 2003), and textile wastewater (Radha et al., 2009), resin (Prabhakaran et al., 2009), pharmaceutical effluent (Abhijit et al., 2005, deproteinated whey wastewater (Guven et al., 2008), distillery spent wash (Krishna Prasad and Srivastava, 2009), dairy manure (Ihara et al., 2006), and organic pollutants (Martinez-Huitle and Ferro, 2006). However, there is no study carried out for the treatment of synthetic sugar effluents by electrochemical oxidation methods. ...
The removal of organic compounds from a simulated sugar industrial effluent was investigated through the electrochemical oxidation technique. Effect of various experimental parameters such as current density, concentration of electrolyte and flow rate in a batch electrochemical reactor was studied on the percentage of COD removal and power consumption. The electrochemical reactor performance was analyzed based on with and without recirculation of the effluent having constant inter-electrodes distance. It was found out that the percentage removal of COD increased with the increase of electrolyte concentration and current density. The maximum percentage removal of COD was achieved at 80.74% at a current density of 5A/dm2 and 5g/L of electrolyte concentration in the batch electrochemical reactor. The recirculation electrochemical reactor system parameters like current density, concentration of COD and flow rate were optimized using response surface methodology, while COD removal percents were maximized and power consumption minimized. It has been observed from the present analysis that the predicted values are in good agreement with the experimental data with a correlation coefficient of 0.9888.
... Regardless of the source of the vinasse, however, the removal efficiency is impacted to some degree by the negative effect of the organics present, especially polyphenolic compounds [13], on the microorganisms used in the biological treatment of vinasse. Various authors have suggested alternative methods and approaches based on a combination of biological and physicochemical methods that more efficiently purify vinasse and wastewater in general containing natural organic material (NOM) [9,10,12,[14][15][16][17][18][19]. ...
We investigated the use of coagulation/flocculation (CF) and electrochemical oxidation (EO) processes to purify vinasse that had already been biologically treated (vinasse BT). The CF process was analyzed as a function of the concentration of the coagulant (FeCl3) and the pH of the vinasse BT. After the CF process, EO was performed by potentiostatic electrolysis with a Ti/RuPb(40%)Ox anode and Ti/PtPd(10%)Ox cathode. The EO process was analyzed as a function of pH of vinasse CF treated and electrolysis time. The efficiencies of the CF and OE treatments on the vinasse BT were quantified in terms of the removal of chemical oxygen demand (COD), color and turbidity. The experimental results showed that the CF process with a coagulant concentration of 20 g/L and a pH of 8.4 removes a significant amount of COD (84%), color and turbidity (∼99%). The subsequent EO step satisfactorily complemented the purification of vinasse BT by CF, yielding removal efficiencies of more than 95% for COD and on the order of 100% for color and turbidity. We suggest that the mineralization via electrochemistry took place by indirect oxidation, mediated by active chlorine derived from FeCl3 added during the CF treatment step.
... Many researchers had investigated the electrochemical oxidation of various types of wastewater containing phenol [23][24][25], cyanides [26], nuclear wastes [27], human wastes [28], cigarette industry wastewater [29], textile wastewater [30] and tannery wastewater [31]. Nevertheless, there are few studies dealing with electrochemical treatment of food-processing industrial wastewaters such as deproteinated whey wastewater [32], coke-plant wastewater [33], coffee curing wastewater [34], olive oil wastewater [35], olive mill wastewater [36][37][38][39][40][41][42], green table olive processing wastewater [43], starchy wastewater [44], distillery industry wastewater [45][46][47], beer brewery wastewater [48] and vinasse wastewater from beet molasses [49]. ...
Electrochemical treatment of simulated beet sugar factory wastewater was studied as an alternative treatment method for the first time in literature. Through the preliminary batch runs, appropriate electrode material was determined as iron due to high removal efficiency of chemical oxygen demand, COD, and turbidity. The effect of operational conditions, applied voltage, electrolyte concentration and waste concentration on COD removal percent and initial COD removal rate were investigated through response surface methodology, RSM. In the set of runs, highest COD removal and COD initial removal rate were realized as 86.36% and 43.65 mg/L min, respectively, after 8 h at the applied voltage of 12 V, 100% waste concentration with 50 g/L NaCl. Treatment conditions were optimized by RSM where applied voltage was kept in the range, electrolyte concentration was minimized, waste concentration, COD removal percent and COD initial removal rate were maximized at 25 °C. Optimum conditions at 25 °C were estimated as 12 V applied voltage, 100% waste concentration and 33.05 g/L electrolyte concentration to achieve 79.66% and 33.69 mg/L min for COD removal and COD initial removal rate, respectively. Kinetic investigations denoted that reaction order of electrochemical treatment reaction was 1.2 with the activation energy of 5.17 kJ/mol. These results support the applicability of electrochemical treatment to the beet sugar factory wastewater as an alternative advanced wastewater treatment method with further research.
... Thus, these methods, particularly electrooxidation, can be used for degrading or reducing the concentration of toxic pollutants in wastewater. The technique has been widely applied for the treatment of textile wastewater (Naumczyk et al., 1996a), tannery wastewater (Rao et al., 2001), coke plant wastewater (Chiang et al., 1995a), coffee curing wastewater (Bejankiwar et al., 2003), and other wastewaters containing cyanides (Lanza and Bertazzoli, 2002) and phenol (Canizares et al., 2002 ). The method was also applied for treatment of landfill leachate (Deng and Englehardt, 2007). ...
The electrooxidation of high strength leachate from an industrial solid waste landfill site was carried out in a three-dimensional carbon bed electrode reactor (TDR). This paper discusses the kinetics and mechanism of electrooxidation on the basis of time course variation of COD, TOC and TKN (total Kjeldahl nitrogen) from the raw leachate. The batch experiments were run at different applied currents (1-3 A) for a period of 6h. A two-stage pseudo-first order reaction kinetics model was developed based on the initial rapid removal of pollutants (Phase I) followed by slow oxidation kinetics (Phase II). About 60-64% COD was removed within 1h with a rate constant 5.83 x 10(-3) min(-1) in Phase I, which was near 5-7 times greater than that of Phase II (0.81-1.03 x 10(-3)min(-1)). The mineralization efficiency was found to be significant in the range 0.83-0.84. The apparent faradic efficiency and specific energy consumption for COD removal were also estimated. The mechanism of electrooxidation was discussed with the help of adsorption, kinetic and SEM results.
... Compared to other technologies, electrochemical method is economical, efficient, and its space requirement is usually much lower (Chen, 2004). Successful applications of electrochemical technology to various wastewater, have been reported world wide (Min et al., 2004;Rao et al., 2001;Szpyrkowicz et al., 2005), such as dyeing wastewater (Wang et al., 2006;Shen et al., 2001;Lin and Chen, 1997;Xiong et al., 2001), the wastewater containing nitrobenzene compounds (Xu et al., 2006), pnonylphenol (Kuramitza et al., 2002), or cyanide (Lanza and Berlazzoil, 2002), landfill leachate (Thaveemaitree et al., 2003), phenolic wastewater (Korbahti and Tanyolac, 2003), coffee curing wastewater (Bejankiwar et al., 2003), and tannery wastewater. To increase reactor efficiency and decrease side reactions, many new electrode materials and reactors were developed recently (Subbiah et al., 2003;Polcaro et al., 2004;Zanta et al., 2003;Zollinger et al., 2004;Rodriguez and Martinez, 2005;Xiong et al., 2002). ...
A novel electrochemical setup for wastewater treatment-rotating electrochemical disc process (RECDP) was developed in this article. The anode and cathode are distributed alternatively and evenly on a flat round disc, which was designed to improve mass transfer of organics from bulk solution to electrode surface, while at the same time increasing oxygen transfer from air to the liquid to benefit the organics oxidization. The color removal of dye Reactive Brilliant Orange X-GN (RBO) was experimentally investigated using the setup. The results show that the RECDP could efficiently remove the color by 99.5% after 60-min electrolysis. The influence of factors such as the disc rotating speed, current intensity, pH, and treating time was also explored, and the de-colorization mechanism was studied with electron paramagnetic resonance (EPR), UV-Vis, and IR. It has been confirmed that the free radicals oxidization leads to the dye de-coloration.
... Since the late 1970s, electrochemical oxidation has been successfully applied to the treatment of textile wastewater (Naumczyk et al., 1996), tannery wastewater (Rao et al., 2001), coke-plant wastewater (Chiang et al., 1995a), coffee curing wastewater (Bejankiwar et al., 2003), and other wastewaters containing cyanides (Lanza and Bertazzoli, 2002) and phenol (Canizares et al., 2002). This process has been used for landfill leachate treatment over the past 10 years. ...
This paper aims at providing an overview of electrochemical oxidation processes used for treatment of landfill leachate. The typical characteristics of landfill leachate are briefly reviewed, and the reactor designs used for electro-oxidation of leachate are summarized. Electrochemical oxidation can significantly reduce concentrations of organic contaminants, ammonia, and color in leachate. Pretreatment methods, anode materials, pH, current density, chloride concentration, and other additional electrolytes can considerably influence performance. Although high energy consumption and potential chlorinated organics formation may limit its application, electrochemical oxidation is a promising and powerful technology for treatment of landfill leachate.
... The method is safe, fast and effective and does not generate any pollution. Bejankiwar et al. (2003) studies the removal of color and organic compounds from biologically treated coffee curing wastewater by an electrochemical oxidation method. They showed that the steel anode was effective for the COD and color removal with anode efficiency of 0.118 kg COD/(h·A·m 2 ). ...
The removal of the natural organic matter present in coffee processing wastewater through chemical coagulation-flocculation and advanced oxidation processes (AOP) had been studied. The effectiveness of the removal of natural organic matter using commercial flocculants and UV/H2O2, UV/O3 and UV/H2O2/O3 processes was determined under acidic conditions. For each of these processes, different operational conditions were explored to optimize the treatment efficiency of the coffee wastewater. Coffee wastewater is characterized by a high chemical oxygen demand (COD) and low total suspended solids. The outcomes of coffee wastewater treatment using coagulation-flocculation and photodegradation processes were assessed in terms of reduction of COD, color, and turbidity. It was found that a reduction in COD of 67% could be realized when the coffee wastewater was treated by chemical coagulation-flocculation with lime and coagulant T-1. When coffee wastewater was treated by coagulation-flocculation in combination with UV/H2O2, a COD reduction of 86% was achieved, although only after prolonged UV irradiation. Of the three advanced oxidation processes considered, UV/H2O2, UV/O3 and UV/H2O2/O3, we found that the treatment with UV/H2O2/O3 was the most effective, with an efficiency of color, turbidity and further COD removal of 87%, when applied to the flocculated coffee wastewater.
... Nevertheless, there is less research dealing with electrochemical treatment of food-processing industrial wastewater. Electrochemical oxidation was applied to the treatment of cokeplant wastewater [33], coffee curing wastewater [34], olive oil wastewater [35], olive mill wastewater [36][37][38][39][40][41][42], green table olive processing wastewater [43], starchy wastewater [44], distillery industry wastewater [45][46][47], beer brewery wastewater [48] and vinasse from beet molasses [49]. ...
Electrochemical treatment of deproteinated whey wastewater produced during cheese manufacture was studied as an alternative treatment method for the first time in literature. Through the preliminary batch runs, appropriate electrode material was determined as iron due to high removal efficiency of chemical oxygen demand (COD), and turbidity. The electrochemical treatment conditions were optimized through response surface methodology (RSM), where applied voltage was kept in the range, electrolyte concentration was minimized, waste concentration and COD removal percent were maximized at 25 degrees C. Optimum conditions at 25 degrees C were estimated through RSM as 11.29 V applied voltage, 100% waste concentration (containing 40 g/L lactose) and 19.87 g/L electrolyte concentration to achieve 29.27% COD removal. However, highest COD removal through the set of runs was found as 53.32% within 8h. These results reveal the applicability of electrochemical treatment to the deproteinated whey wastewater as an alternative advanced wastewater treatment method.
Research for better combustion technologies, and renewable and clean energy sources is driven by environmental
contamination as well as the current energy crisis. Many low-temperature combustion (LTC) technologies have been
proposed to increase engine combustion efficiency and lower emissions. To regulate the ignition and combustion
process, the reactivity control compression ignition (RCCI) combustion mode had preferred to reduce smoke and
oxide of nitrogen emissions, but it didn't get the best solution yet. The intake system is modified to use port injection
in RCCI operations for controlling emissions, in-cylinder charge reactivity, and combustion phasing. The
experimental investigation of a triple-fuel RCCI engine running on port-injected blends of gasoline and ethanol while
diesel fuel is injected directly. The results of G25E75-RCCI engine operation modes have a maximum cylinder
pressure of 88 bars at 3000 rpm and a minimum of 58 bars at 2600 rpm on baseline fuel represented D100G0E0. The
maximum Heat Release Rate (HRR) of the engine is 62 J/deg at the engine speed of 3000 rpm when operating with
the G25E75-RCCI engine and a minimum at G50E50-RCCI with an HRR of 10 J/deg. The engine operating with
G25E75 fuel had a minimum of NOx, smoke, and CO2, which were maximum at the engine running with the baseline
experiment. The brake power of the engine is maximum at maximum speed (3000 rpm), and the brake torque is
maximum at about 2400 and 2500 rpm with the engine running on a G50E50-RCCI engine. The triple-fuel RCCI
engine performs better in terms of thermal efficiency, brake power, brake torque, and minimum NOx emission at
middle and higher engine speeds at 80% engine load, but stalls at lower engine speeds below 2200 rpm.
he optimization of operational parameters is crucial to maximizing biogas yield and quality. The impact of food waste (FW)/coffee husk (CH) ratios (100:0, 60:40, 50:50, 40:60, and 0:100) and initial pH values (5, 6, 6.5, and 7.5) on biogas yield and the biodegradability of the FW and CH co-digestion was studied under mesophilic conditions. First-order kinetic, modified Gompertz, and modified logistic models were also applied to fitting experimental results, to explain the kinetics of the co-digestion process. The findings showed that adding FW and increasing initial pH levels could greatly upgrade CH biogas production and biodegradability. The highest biogas yield was 540.78 ml/gVS and synergy of 1.46, with the highest biodegradability (BDfpc) and biodegradation degree (ηBD) of 85.64 and 56.80%, respectively, for FW/CH ratio of 60:40 and pH 7, 164% raised compared to that 204.71 ml/gVS of the CH alone. A modified logistic model outperformed others with the best fitness. The synergistic effect evaluation disclosed that the synergy of the joint treatment of feedstocks might be the reason for the upgraded biogas yields. This study demonstrated the feasibility and attractiveness of co-digestion of FW and CH, affording a sound basis for cost- effective renewable energy recovery.
Wet coffee pulping process generates organic pollutant rich wastewater, and causes serious threat to the local water bodies. Hence, the efficiency of Ricinus communis L. seed protein to remove colour, total dissolved solids (TDS) and chemical oxygen demand (COD) from the coffee cherry pulping wastewater (CCPWW) was studied. Treatment with 0.5 g optimum dosage of the seed protein reduced 80 % colour, 75 % total dissolved solids and 80 % chemical oxygen demand from the wastewater, along with a change in the pH from 3.7 to 5.2. Characterisation of the seed protein using sodium dodecyl sulphate polyacrylamide gel electrophoresis and matrix assisted laser desorption ionization – time of flight assay confirmed a ricin glycoprotein band at 28 kDa. This ricin B chain lectin protein with 262 amino acid residues caused the coagulation activity in the wastewater, due to its cationic nature, sugar binding sites and hydrogen bonding forces between molecules. Fourier transformed infrared characterization of the seeds showed the presence of amide groups involved in pollutant removal. A positive linear correlation ‘r’ 0.9 proved the degree of association between the removal of total dissolved solids and chemical oxygen demand from CCPWW. Hence, the study suggested that the pollutants from wastewater could be removed using Ricinus communis L. seed lectin protein, as an alternative eco-friendly coagulant agent replacing synthetic coagulant chemicals.
This study examined a sequential Electro-Coagulation-Anodic Oxidation (EC-AO) process, using low-cost electrodes (EC: iron/stainless steel and AO: graphite/stainless steel), as an alternative for the treatment of soluble coffee industrial effluent (a complex mixture of organic macromolecules). Process operational parameters were optimized using experimental design, ANOVA, the response surface methodology, and a constrained nonlinear optimization algorithm. Experimental results allow discussing the role of graphite electrode, the mineralization via hydroxyl radicals and chlorine species (mainly as HClO and ClO⁻ as defined from pH conditions and equilibrium calculations). EC-AO treatment allows achieving ca. 97% decolorization, as well as 72% and 65% of COD and TOC removal, respectively, with total operation costs of 10.81 USD/m³. The Molecular Weight Distribution (MWD) analysis showed that during the EC step, contaminants with molecular weight > 30 kDa were effectively decomposed. In contrast, AO was quite efficient in the mineralization of contaminants with MW in the range of 5 to 10 kDa. A kinetic analysis of EC-AO allowed defining the operation time of ca. 160 min required to meet permissible discharge limits for soluble coffee effluents, established by Colombian legislation; and obtaining COD and TOC degradation rate laws for upcoming studies on process conceptual design. Finally, the EC-AO process yielded an oxidized (AOS = 0.687), biocompatible (BOD5/COD = 0.41) not toxic effluent.
Coffee processing wastewater is one of the major agro-processing wastes that put high pollution pressure in coffee growing and exporting countries affecting water, soil, and human health. The processing industries apply no or low efficient technologies for management due to a lack of economic and technological feasibility. The purpose of this review was to assess ever practiced and studied management options of coffee processing wastewater and design feasible alternatives suitable for coffee-producing and agrarian regions. Treatment/management efficiencies of the advanced oxidation process, coagulation-flocculation, adsorption, wetland system, anaerobic digestion and fertigation along with their limitations were considered in this review. Most importantly, this work demonstrates fertigation as the first choice of coffee effluent management for agrarian coffee-producing countries due to low cost, additional nutrient value and ease of technological application.
In this paper, we present color, solids and organic matter removal from Electrochemical coagulation (ECC) followed by Sequential batch reactor (SBR) of coffee wastewater. Sacrificial electrode (Aluminium) dissolutions controlled by the cell voltage was found as key factor. Electrocoagulation is used as a pretreatment which is then followed by sequential batch reactor. Electrochemical coagulation is conducted in wide range of voltages from 5 to 40 volts to find optimum voltage for a time period of 60 minutes. Samples were collected at a time interval of 15 minutes each and were analyzed. Efficiency obtained were ~97 % for removal of color, ~60 % of solids and ~64 % for removal of organic matter in electrochemical coagulation. After electrochemical coagulation wastewater is passed to sequential batch reactor for further treatment. Sequential batch reactor is a biological treatment process, where wastewater was treated in a batch by adding cow dung slurry as seeding innoculum. Whole process is divided into five phases with total time period of eight hours. Overall efficiency obtained after both the processes was ~93 % in the removal of color, ~62 % removal in solids and ~84 % in removal of organic matter
In this paper, we present color, solids and organic matter removal from Electrochemical coagulation (ECC) followed by Sequential batch reactor (SBR) of coffee wastewater. Sacrificial electrode (Aluminium) dissolutions controlled by the cell voltage was found as key factor. Electrocoagulation is used as a pretreatment which is then followed by sequential batch reactor. Electrochemical coagulation is conducted in wide range of voltages from 5 to 40 volts to find optimum voltage for a time period of 60 minutes. Samples were collected at a time interval of 15 minutes each and were analyzed. Efficiency obtained were ~97 % for removal of color, ~60 % of solids and ~64 % for removal of organic matter in electrochemical coagulation. After electrochemical coagulation wastewater is passed to sequential batch reactor for further treatment. Sequential batch reactor is a biological treatment process, where wastewater was treated in a batch by adding cow dung slurry as seeding innoculum. Whole process is divided into five phases with total time period of eight hours. Overall efficiency obtained after both the processes was ~93 % in the removal of color, ~62 % removal in solids and ~84 % in removal of organic matter
In this paper, we present color, solids and organic matter removal from Electrochemical coagulation (ECC) followed by Sequential batch reactor (SBR) of coffee wastewater. Sacrificial electrode (Aluminium) dissolutions controlled by the cell voltage was found as key factor. Electrocoagulation is used as a pretreatment which is then followed by sequential batch reactor. Electrochemical coagulation is conducted in wide range of voltages from 5 to 40 volts to find optimum voltage for a time period of 60 minutes. Samples were collected at a time interval of 15 minutes each and were analyzed. Efficiency obtained were ~97% for removal of color, ~60% of solids and ~64% for removal of organic matter in electrochemical coagulation. After electrochemical coagulation wastewater is passed to sequential batch reactor for further treatment. Sequential batch reactor is a biological treatment process, where wastewater was treated in a batch by adding cow dung slurry as seeding innoculum. Whole process is divided into five phases with total time period of eight hours. Overall efficiency obtained after both the processes was ~93% in the removal of color, ~62% removal in solids and ~84% in removal of organic matter.
The coffee agro-industry generates a large volume of wastewater that is notable for its high organic strength as well as its color content. Due to the seasonal nature of the harvest (3-4 months per year), this particular industrial waste needs a treatment method that is both reliable and fast (in terms of start-up time). As part of investigating a system capable of treating a coffee wastewater, this research evaluated four electrochemical advanced oxidation processes (EAOPs) using boron-doped diamond (BDD) electrodes. The processes were anodic oxidation (AO), anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), and photoelectro-Fenton (PEF). Experimental conditions were as follows: 40 mA cm-2 current density (all EAOPs), 0.3 mmol Fe2+ L-1 (Fenton systems), 300 mL air min-1 (AO-H2O2, EF, PEF), and 500 μW cm-2 UV irradiation (photo-Fenton systems). The performance of the four EAOP treatment methods (in terms of color and organic carbon removal) was compared against two conventional chemical oxidation methods, namely, Fenton and photo-Fenton. The research indicated that the four EAOPs were better at removing color (89-93 %) and total organic carbon (TOC) (73-84 %) than the respective chemical Fenton (58 and 4.8 %) and photo-Fenton (61 and 7 %) methods. The trend in performance was as follows: AO-H2O2∈>∈AO∈>∈PEF∈≈∈EF. It appeared that the ferrous iron reagent formed a dark-colored complex with some coffee components, diminishing the effect of Fenton reactions. In addition, the dark color of the wastewater limited the effect of light in the UV-Fenton processes. Analysis showed that acceptable levels of Fe2+ (0.3 mmol L-1) and energy (0.082-0.098 kWh g-1 TOC) were required by the EAOPs after 4-h treatment time. In conclusion, the use of electrochemical methods (equipped with BDD electrodes) seems a promising method for the effective treatment of coffee wastewaters.
A fixed bed electrochemical reactor comprising stainless steel cathode/granular activated carbon (GAC) bed//Carbon anode//GAC bed//stainless steel cathode configuration was fabricated and tested for degradation of Reactive Blue 4 aqueous solutions (RB4). On the basis of measured concentrations of residual RB4 dye and total organic carbon (TOC), approximately 80–90% of RB4 dye was found to be degraded at 0.30–0.90 A and 13.4 ± 0.1 V in 6 h under recirculation batch mode of operation (flow rate, 1.8 Lh−1). The dye removal due to adsorption on carbon was ∼9–10% under the same experimental conditions but excluding applied current. The apparent Faradic efficiency and electrical energy consumption were estimated to be 2.8% and 16.0 kWh kg−1 RB4 at the optimum current and voltage (0.6 A, 13.3 V). Further, the adsorption of the dye on GAC bed, cyclic voltammetric response of RB4, SEM and FT-IR characterization of original and spent carbon and ion chromatographic analysis of inorganic intermediates were carried out to elucidate the mechanism of dye degradation. It appears that the dye degradation takes place by ready scission of SO3H groups, and oxidation of mainframe chromophore (anthraquinone group). The chlorotriazine group resists to the electrooxidation and remains as the final reaction product.
Dairy industry wastewater is characterized by high chemical oxygen demand (COD) and other pollution load. In the present study, the treatment of simulated dairy wastewater (SDW) was performed by electrochemical (EC) method using iron electrode. Full factorial central composite design (CCD) with four factors namely current density (J), dosage of sodium chloride (NaCl) (m), electrolysis time (t) and pH, with each factor at five levels, was used to optimize the factors for higher COD removal. Operational parameters J, m, t and pH were varied between 61.73–308.64 A/m2, 0–2 g/l, 10–90 min and 5–11, respectively. Optimum value of J, t and pH were found 270 A/m2, 50 min, and 7.0, respectively, while m was found to be zero. Optimum COD removal efficiency was found to be ≈70%. Physico-chemical analysis of iron electrodes and residues (scum and sludge) has been carried out to understand the EC mechanism as well as to study the disposal aspect of the residues generated during EC treatment. The mechanism of COD removal by EC seems to be a combination of electro-coagulation, electro-floatation and electro-oxidation.
The electrochemical oxidation of distillery effluent was studied in a batch reactor in the presence of supporting electrolyte NaCl using Mixed Metal Oxide (MMO) electrode. The effect of operating parameters such as current density, initial pH, and initial electrolyte concentration on the percentage of Chemical Oxygen Demand (COD) removal, power consumption, and current efficiency were studied. The maximum percentage removal of COD was observed to be 84% at a current density of 3 A/dm2at an electrolyte concentration of 10 g/l with an effluent COD concentration of 1000 ppm and at an initial pH of 6. The operating parameters for the treatment of distillery effluent by electrochemical process were optimized
using response surface methodology by CCD. The quadratic regression models with estimated coefficients were developed for the percentage removal of COD and power consumption. It was
observed that the model predictions matched with experimental values with an R2 value of 0.9504 and 0.9083 for COD removal and power consumption respectively. The extent of color removal
and oxidation of organic compounds were analyzed using UV spectrophotometer and HPLC.
An electrochemical method is proposed for the degradation of an industrial effluent from a chemical industry, containing sulfonate‐ and phenol‐ derivatives.A model solution simulating the composition of the waste was prepared and the degradation kinetics of each component was followed. For this purpose an ion‐interaction HPLC method was developed, able to simultaneously separate phenol‐ and sulfonate‐ derivatives. The method is essentially based on the formation of ion‐pairs in a mobile phase of octylamine o‐phosphate at pH=8.0The degradation process was then applied in the analysis of the waste. Both for the model solution and for the waste, the electrochemical process led to about 80% degradation.
The electro-oxidation of dilute aqueous solutions of aniline was studied on a lead dioxide packed bed anode. The anolyte consisted of 400 ml of 5.5 mM aniline in dilute sulphuric acid. The anolyte was recirculated through a packed bed electrochemical reactor with an anode compartment volume of 5.0, at various flowrates. The concentrations of aniline, benzoquinone, maleic acid and carbon dioxide were measured against time for experiments ranging from 0.5 to 5.0h in duration. The effects of applied current, pH, flowrate and initial aniline concentration on the percentage of aniline oxidized and carbon dioxide produced are discussed. Aniline in the solution oxidized readily, but further oxidation of intermediates to carbon dioxide was more difficult. The percentage of aniline oxidized increased with increasing current density, while it decreased with increasing initial aniline concentration and pH. Current efficiencies ranged from 15 to 40% for complete oxidation of aniline to CO2.
The electro-oxidation of dilute aqueous solutions of aniline was studied on a lead dioxide packed bed anode. The anolyte consisted of 400 ml of 5.5 mM aniline in dilute sulphuric acid. The anolyte was recirculated through a packed bed electrochemical reactor with an anode compartment volume of 5.0, at various flowrates. The concentrations of aniline, benzoquinone, maleic acid and carbon dioxide were measured against time for experiments ranging from 0.5 to 5.0h in duration. The effects of applied current, pH, flowrate and initial aniline concentration on the percentage of aniline oxidized and carbon dioxide produced are discussed. Aniline in the solution oxidized readily, but further oxidation of intermediates to carbon dioxide was more difficult. The percentage of aniline oxidized increased with increasing current density, while it decreased with increasing initial aniline concentration and pH. Current efficiencies ranged from 15 to 40% for complete oxidation of aniline to CO2.
Refractory pollutants, including lignin, tannic acid, chlortetracycline, and EDTA, were destroyed by an electrochemical oxidation method to evaluate the applicability of this method for industrial wastewater pretreatment. Operation parameters, such as supporting electrolyte, current density, and electrolyte concentration, have been investigated for their influences on COD removal efficiencies during electrolysis. In addition, gel permeation chromatography (GPC), Microtox test, and total organic halogen (TOX) analyses were performed to monitor the changes of organic characteristics of these refractory pollutants. Experimental results show that, among sulfate, nitrate, and chloride, chloride was the best supporting electrolyte, and during electrolysis, both COD and color removal efficiencies were improved by increasing current density and chloride concentration. From GPC analysis results, the electrochemical oxidation process readily destroys high-molecular-weight (HMW) organics. Microtox test results also show that the process can reduce the toxicity of these refractory organic compounds. In addition, TOX concentrations were found to increase at the beginning but then decline during the electrolysis. The above results suggest that the electrochemical oxidation process, which has good efficacy for detoxification and destruction of refractory pollutants, is a promising method for wastewater pretreatment.
Treatment of textile wastewaters from several dyeing and finishing mills by an electrochemical method is investigated. The batch experimental results are assessed in terms of color (turbidity) and COD reductions. Several operating variables, such as the wastewater conductivity, pH, power requirement and amount of polyelectrolyte added, are explored to ascertain their respective effects on the treatment efficiency. Optimum operating ranges for each of these operating variables are experimentally determined. The electrochemical method is found to be quite effective and is highly competitive as an alternative chemical method for treating textile wastewater. A continuous experimental apparatus is designed and test runs are performed using the operating conditions obtained in the batch experiments. The preliminary data show similar satisfactory results to those of the batch runs.
Liquid chromatographic analysis is used to identify oak tannin fractions by their phenolies, i.e. gallic and ellagic acids, and acacia tannins by vanillic acid and syringaldehyde. Chestnut tannins also contained gallic acid while their chromatographic profile differed otherwise from the oak pattern. Spruce and fir tannin fractions did not contain identifiable major phenolics and their tannin concentrations were also an order of magnitude less than the above-mentioned woods. Whereas the identified phenolics accounted for only a part of the total tannins, there was a correlation with the general tannin content of the wood expressed as tannic acid equivalents. Thus, the method can probably be used for taxonomic purposes and for a specific detection of hard wood exposure in carpentry shops and in other wood working trades.