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Comparison of COD removal from pharmaceutical wastewater by electrocoagulation, photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes
Abstract
This work makes a comparison between electrocoagulation (EC), photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes to investigate the removal of chemical oxygen demand (COD) from pharmaceutical wastewater. The effects of operational parameters such as initial pH, current density, applied voltage, amount of hydrogen peroxide and electrolysis time on COD removal efficiency were investigated and the optimum operating range for each of these operating variables was experimentally determined. In electrocoagulation process, the optimum values of pH and voltage were determined to be 7 and 40 V, respectively. Desired pH and hydrogen peroxide concentration in the Fenton-based processes were found to be 3 and 300 mg/L, respectively. The amounts of COD, pH, electrical conductivity, temperature and total dissolved solids (TDS) were on-line monitored. Results indicated that under the optimum operating range for each process, the COD removal efficiency was in order of peroxi-electrocoagulation > peroxi-photoelectrocoagulation > photoelectrocoagulation>electrocoagulation. Finally, a kinetic study was carried out using the linear pseudo-second-order model and results showed that the pseudo-second-order equation provided the best correlation for the COD removal rate.
... Apart from that, AOPs were applied for the treatment of strong organic pollutants in the PhWW [13][14][15][16][17][18]. In addition, AOPs are also considered an appropriate technology for the treatment of PhWW based on their oxidants [15,[18][19][20][21]. ...
... In recent years, many treatment technologies were studied for the decontamination of PhWW such as ozonation [11,20,36,[54][55][56][57], photocatalysis [24,25,36,41,54,55,57,58], O 3 /H 2 O 2 [11,14,20], UV/H 2 O 2 [59], electrocoagulation [21,23,60], adsorption [22], photo- Fig. 17. Mechanism of hybrid treatment process. ...
... Mechanism of hybrid treatment process. electrocoagulation and peroxi-electrocoagulation [21], Fenton and photo-Fenton [55,57,61], membrane technology [28,29,31,32,[35][36][37], biological treatment [2,5,6,36,[61][62][63], Electroflocculation [26,27], catalytic ozonation [7,26,27,64], electrochemical oxidation [10,18,57] and hybrid treatment [26,27,37,57,58]. Although, these treatment technologies have benefits and certain limitations. ...
The removal of veterinary antibiotics in pharmaceutical wastewaters become more challenging with modern-day technologies due to their persistent nature. In a sequence, the release of veterinary antibiotics containing wastewater such as Enrofloxacin (EFC) and Tylosin Tartrate (TT) in water bodies has increased the chance for bacteria to attain the antibiotic resistance genes and also moved to others via horizontal gene movement. As a result, the microbes become more resistant even to conventional antibiotics due to the growth of antibiotic resistance genes in microbes. Consequently, conventional treatment technologies just partially remove the pharmaceuticals from the wastewater and are not fully effective because they are not premeditated to remove antibiotics drugs. This alarming situation seriously threatens human well-being and aquatic life. Therefore, it is indeed important to develop an economical advanced oxidation treatment method for the efficacious treatment of pharmaceutical wastewater (PhWW). In the current study, a novel approach was adopted by implying Electroflocculation (EF), Catalytic ozonation (CO) in combination with novel catalyst Ni-Co-Zeolite 5A° followed by Ceramic membrane filtration (CMF). For the first time, in the current investigation, the studied hybrid process (EF + CO–CMF) using Zeolite 5A° coated with double metal salts of Nickel and Cobalt was applied as a catalyst in ozonation (O3) for the treatment of PhWW. Moreover, the removal of COD, BOD5, and turbidity was also studied and compared with national and international effluent quantity discharge standards. The obtained results exhibited that the combined EF + CO process has achieved removal efficiencies of 33 %, 93 %, 78 %, 45 %, and 60 % for EFC, TT, COD, BOD5, and turbidity respectively. Furthermore, the integration of CMF after EF + CO has enhanced the removal of pollutants up to the mark. It was revealed that the novel combined treatment method EF + Ni-Co Zeolite 5A°/O3–CMF has removed the EFC, TT, COD, BOD5, and turbidity of 97 %, 98 %, 90 %, 86 %, and 93 % respectively at optimum conditions (pH = 7.1 ± 0.2; treatment time = 30 min; EF voltage = 10 V; catalyst dose = 10 g/L; O3 = 1.1 mg/min). Additionally, it was observed that biodegradability (BOD5/COD ratios) enhanced from 0.48 to 0.60, and become easily biodegradable for further treatment. Henceforth, EF + Ni-Co Zeolite 5A°/O3–CMF treated wastewater has also complied with the Punjab Environmental Quality Standards (PEQS). Therefore, this novel hybrid treatment process may efficaciously apply at an industrial scale for the treatment of veterinary antibiotics containing PhWW.
... Apart from that, AOPs were applied for the treatment of strong organic pollutants in the PhWW [13][14][15][16][17][18]. In addition, AOPs are also considered an appropriate technology for the treatment of PhWW based on their oxidants [15,[18][19][20][21]. ...
... In recent years, many treatment technologies were studied for the decontamination of PhWW such as ozonation [11,20,36,[54][55][56][57], photocatalysis [24,25,36,41,54,55,57,58], O 3 /H 2 O 2 [11,14,20], UV/H 2 O 2 [59], electrocoagulation [21,23,60], adsorption [22], photo- Fig. 17. Mechanism of hybrid treatment process. ...
... Mechanism of hybrid treatment process. electrocoagulation and peroxi-electrocoagulation [21], Fenton and photo-Fenton [55,57,61], membrane technology [28,29,31,32,[35][36][37], biological treatment [2,5,6,36,[61][62][63], Electroflocculation [26,27], catalytic ozonation [7,26,27,64], electrochemical oxidation [10,18,57] and hybrid treatment [26,27,37,57,58]. Although, these treatment technologies have benefits and certain limitations. ...
... Current density has a collective effect on the EC process efficiency (Islam, 2019;Linares-Hern andez et al., 2009) and optimum current density is required for effective treatment performance. Although a higher current density is required for a higher amount of metal coagulant generation for contaminant removal (Bayar et al., 2011;Farhadi et al., 2012), unnecessarily high current values may negatively affect the EC efficiency in addition to higher energy consumption (Farhadi et al., 2012; Hakizimana et al., 2017). Also, Zaied et al. (2020) recommended that there is an optimum treatment time after which an increase in reaction time causes a slight increase in removal efficiency and higher energy consumption. ...
... Current density has a collective effect on the EC process efficiency (Islam, 2019;Linares-Hern andez et al., 2009) and optimum current density is required for effective treatment performance. Although a higher current density is required for a higher amount of metal coagulant generation for contaminant removal (Bayar et al., 2011;Farhadi et al., 2012), unnecessarily high current values may negatively affect the EC efficiency in addition to higher energy consumption (Farhadi et al., 2012; Hakizimana et al., 2017). Also, Zaied et al. (2020) recommended that there is an optimum treatment time after which an increase in reaction time causes a slight increase in removal efficiency and higher energy consumption. ...
... Besides, COD removal decreased after 24 min due to the increased concentration of Fe 2þ in the solution. This might be due to the overdosage of Fe 2þ that reversed the surface charge of particles, reducing the treatment efficiency (Farhadi et al., 2012;Hakizimana et al., 2017). For the degradation of MO by Advanced Fenton Process using zero valent metallic iron, Devi et al. (2009) reported that the excess concentration of Fe 2þ form hydroxide compound raising the pH of the solution, which further leads to precipitation, reducing the degradation rate. ...
The wastewater generated from textile industries is highly colored and contains dyes including azo dyes, which are toxic to human and water-living organisms. The treatment of these azo dyes using conventional treatment techniques is challenging due to their recalcitrant properties. In the current study, the effect of additional Fe²⁺ on electrocoagulation (EC) using Fe electrodes has been studied for the removal of methyl orange (MO) azo dye. pH between 4-5 was found to be optimum for EC and treatment efficiency decreased with increasing dye concentrations. With the addition of Fe²⁺ salt, dye removal for a certain concentration was increased with the increase of current density and Fe²⁺ up to a certain limit and after that, the removal efficiency decreased. The COD, color and dye removals were 88.5%, 93.1% and 100%, respectively, for EC of 200 mg.L⁻¹ dye solution using only 0.20 mmol.L⁻¹ Fe²⁺ for 0.40 mA.cm⁻² current density, whereas for EC, the respective removal efficiencies were 76.7%, 63.4% and 82.4% for 32 min. The respective operating cost for EC was $768 kg⁻¹ removed dye ($0.342 m⁻³), whereas, for EC with additional Fe²⁺ salt, it was $350 kg⁻¹ removed dye ($0.189 m⁻³). The kinetic results revealed that the first-order kinetic model was fitted best for EC, whereas the second-order kinetic model was best fitted for Fe²⁺ added EC. For real textile wastewater, 57.6% COD removal was obtained for 0.15 mmol.L⁻¹ Fe²⁺ added EC compared to 27.8% COD removal for EC for 32 min. Based on the study we can conclude that Fe²⁺ assisted EC can be used for effective treatment of textile wastewater containing toxic compounds like azo dyes.
... Current density has a collective effect on the EC process efficiency (Islam, 2019;Linares-Hern andez et al., 2009) and optimum current density is required for effective treatment performance. Although a higher current density is required for a higher amount of metal coagulant generation for contaminant removal (Bayar et al., 2011;Farhadi et al., 2012), unnecessarily high current values may negatively affect the EC efficiency in addition to higher energy consumption (Farhadi et al., 2012; Hakizimana et al., 2017). Also, Zaied et al. (2020) recommended that there is an optimum treatment time after which an increase in reaction time causes a slight increase in removal efficiency and higher energy consumption. ...
... Current density has a collective effect on the EC process efficiency (Islam, 2019;Linares-Hern andez et al., 2009) and optimum current density is required for effective treatment performance. Although a higher current density is required for a higher amount of metal coagulant generation for contaminant removal (Bayar et al., 2011;Farhadi et al., 2012), unnecessarily high current values may negatively affect the EC efficiency in addition to higher energy consumption (Farhadi et al., 2012; Hakizimana et al., 2017). Also, Zaied et al. (2020) recommended that there is an optimum treatment time after which an increase in reaction time causes a slight increase in removal efficiency and higher energy consumption. ...
... Besides, COD removal decreased after 24 min due to the increased concentration of Fe 2þ in the solution. This might be due to the overdosage of Fe 2þ that reversed the surface charge of particles, reducing the treatment efficiency (Farhadi et al., 2012;Hakizimana et al., 2017). For the degradation of MO by Advanced Fenton Process using zero valent metallic iron, Devi et al. (2009) reported that the excess concentration of Fe 2þ form hydroxide compound raising the pH of the solution, which further leads to precipitation, reducing the degradation rate. ...
... There have been numerous studies concerning the remediation of wastewater by the application of UV/H 2 O 2 -assisted electrochemical processes. The integrated peroxy-photoelectrochemical treatment has been applied to textile wastewater (GilPavas et al., 2019), tannery wastewater (Borba et al., 2018), organic compounds (Malakootian et al., 2019), distillery effluent , pesticides (Yahiaoui et al., 2011), and pharmaceutical wastewater (Farhadi et al., 2012;Olvera-Vargas et al., 2015). In an integrated process, • OH can be obtained in many ways. ...
... Borba et al. (2018) aimed to investigate optimal conditions of photoperoxi-electrocoagulation process (PPEC) and reported an optimum result at a pH 4, CD 34.2 mA/cm 2, and H 2 O 2 concentration of 6 g/L. These results seem to corroborate with previous studies; however, it was reported that a lower dosage of H 2 O 2 should be sufficient and even beneficial since a higher concentration could lead to the consumption of • OH by peroxide molecules Farhadi et al., 2012). The operating cost was found to be above US$ 1.50/m 3 but could go up to around US$ 6/m 3 , with power and H 2 O 2 supply contributing the most (GilPavas et al., 2019; Borba et al., 2018;Aziz et al., 2016). ...
In recent times, emerging contaminants (ECs) like pharmaceuticals and personal care products (PPCPs) in water and wastewater have become a major concern in the environment. Electrochemical treatment technologies proved to be more efficient to degrade or remove PPCPs present in the wastewater. Electrochemical treatment technologies have been the subject of intense research for the past few years. Attention has been given to electro-oxidation and electro-coagulation by industries and researchers, indicating their potential to remediate PPCPs and mineralization of organic and inorganic contaminants present in wastewater. However, difficulties arise in the successful operation of scaled-up systems. Hence, researchers have identified the need to integrate electrochemical technology with other treatment technologies, particularly advanced oxidation processes (AOPs). Integration of technologies addresses the limitation of indiviual technologies. The major drawbacks like formation of undesired or toxic intermediates, s, energy expenses, and process efficacy influenced by the type of wastewater etc., can be reduced in the combined processes. The review discusses the integration of electrochemical technology with various AOPs, like photo-Fenton, ozonation, UV/H2O2, O3/UV/H2O2, etc., as an efficient way to generate powerful radicals and augment the degradation of organic and inorganic pollutants. The processes are targeted for PPCPs such as ibuprofen, paracetamol, polyparaben and carbamezapine. The discussion concerns itself with the various advantages/disadvantages, reaction mechanisms, factors involved, and cost estimation of the individual and integrated technologies. The synergistic effect of the integrated technology is discussed in detail and remarks concerning the prospects subject to the investigation are also stated.
... Electrochemical oxidation, or electrooxidation (EO), can generate OH radicals with electrical energy able to oxidise several organic compounds and be used for their removal [10]. Electrochemical oxidation has proven effective in contaminant removal [11]. Asokan and Krishnan [12] reported ethanol reduction content by electrochemical oxidation using 0.5 mol/dm 3 in an acid solution with 0.5 mol/dm 3 sulphuric acid. ...
... Another work involving distillery wastewater is reported by Johnson and Kumar [11], reaching up to 5600 COD mg/L.h in 4.0-pH, triplicating the removal than the obtained in this study. ...
Tequila production occurs in Mexico's designated area of origin, principally in the Jalisco State. Its residues are a challenge in treatment and tracking due to a lack of technology, non-economic treatments available, low environmental consciousness and incipient control from authorities. In 2021, average production was close to 1.5 million tequila litres per day with an estimated residue yield of 10-12 litres of stillage (tequila vinasses) per tequila litre produced, including volatile fractions. This research aims to reduce organic matter by electrooxidation (EO) from 5 distillation volatile residual effluents (two-stage still distillation) from three tequila distilleries, first and second-stage heads and heads and tails and second-stage non-evaporated fraction. Round 3 mm titanium (grade-1) electrodes (one anode and one cathode) were used, with fixed voltage to a value of 30 VDC at 0, 3, 6, 9 and 12 hours with 75 experiments. Gas chromatography was used to analyze methanol, ethanol, acetaldehyde, ethyl acetate, n-propanol, sec-butanol, iso-butanol, n-butanol, iso-amyl, n-amyl, and ethyl lactate content. Treatment shows positive results, reducing organic matter content in all effluents in a Chemical Oxygen Demand COD range of 580-1880 mg/L.h, particularly useful in the second-stage non-evaporated fraction for water recovery.
... Organic compounds in this study were used as a carbon source by the microorganisms, effecting heterotrophic denitrification. Moreover, part of the organic compounds in electrochemical systems can be removed by adsorption of dissolved organic compounds on the surface of hydroxy floccules, and by direct oxidation of organic matter on the anode surface [28][29][30]. ...
... Organic compounds in this study were used as a carbon source by the microorganisms, effecting heterotrophic denitrification. Moreover, part of the organic compounds in electrochemical systems can be removed by adsorption of dissolved organic compounds on the surface of hydroxy floccules, and by direct oxidation of organic matter on the anode surface [28][29][30]. Tong et al. [10] and Rodziewicz et al. [19] showed that the growth of organic compound concentration with increasing current density in the bioreactor is a consequence of the decreasing activity of heterotrophic bacteria. Kwon et al. [21] treated effluent from hydroponic cultivation in an SBR reactor with methanol as an external carbon source, and showed that phosphorus, nitrogen and COD removal efficiency of 99.8%, 89.5% and 100%, respectively, can be achieved with a carbon dose of 2.86 g O2 COD/g NO3 − . ...
This study examined the effect of bio-electrochemical treatment processes on nitrogen and phosphorus removal, but it also evaluated the impact of the treatment processes on the concentration of other nutrients present in hydroponic effluent. A bio-electrochemical reactor (BER) was used in the experiment to treat effluent from the hydroponic cultivation of tomatoes. It was stated that the nitrogen removal efficiency decreased with increasing current density. The study showed that an electric current density of 0.63 A/m2 ensured the lowest effluent nitrate concentration. The nitrogen removal efficiency ranged from 41.6%-R1 (density of 0.63 A/m2) to 8.9%-R4 (density of 5 A/m2). Electric current density higher than 1.25 A/m2 resulted in lower total nitrogen removal efficiency. The total phosphorus removal efficiency increased with increasing electric current density. The phosphorus removal efficiency was the lowest—95.1%—in the R1 reactor, whereas it was the highest in R4—99.1%. The concentration of the other elements in the effluent was determined. The content of molybdenum, boron, sulphates, and potassium did not meet the acceptable norms for discharging hydroponic effluent into the environment. The study showed that bio-electrochemical processes taking place in BER caused secondary contamination of hydroponic wastewater with molybdenum ions.
... Electrochemical oxidation, or electrooxidation (EO), can generate OH radicals with electrical energy able to oxidise several organic compounds and be used for their removal [10]. Electrochemical oxidation has proven effective in contaminant removal [11]. Asokan and Krishnan [12] reported ethanol reduction content by electrochemical oxidation using 0.5 mol/dm 3 in an acid solution with 0.5 mol/dm 3 sulphuric acid. ...
... Another work involving distillery wastewater is reported by Johnson and Kumar [11], reaching up to 5600 COD mg/L.h in 4.0-pH, triplicating the removal than the obtained in this study. ...
... Due to rapid industrialization, enormous amounts of polluted water are generated each year by various industries such as petroleum and oil [4][5][6], textile [7][8][9], pulp and paper [10,11], leather [12], pharmaceutical [13], paint, distillery [14,15], tannery [16,17], fertilizer [18,19], sugar [20], land ll leachate [21,22], hospital [22,23], municipal [22] and domestic [24,25], and agricultural wastewater [26]. e aforementioned industrial pollutants contain a variety of complex pollutants like nitrogen, phosphorous, sulphur, and food scraps, including refractory or hazardous organic molecules like fulvic acid, humic acids, phenolic compounds, soap, oil, pathogens, and other harmful substances [27,28]. ...
... e research findings indicated that the overall sodium dodecyl sulphate removal efficiency was 81.60% with a 1.63 kWh (kgSDS) −1 energy International Journal of Chemical Engineering consumption. Farhadi et al. [13] compared the removal of COD from pharmaceutical wastewater using electrocoagulation, photo-electrocoagulation, peroxi-electrocoagulation, and peroxi-photo-electrocoagulation. ey observed the COD removal efficiency for the treatment of pharmaceutical wastewater as follows: peroxi-electrocoagulation > peroxi-photo-electrocoagulation > photoelectrocoagulation > electrocoagulation process. ...
Nowadays, increased human activity, industrialization, and urbanization result in the production of enormous quantities of wastewater. Generally, physicochemical and biological methods are employed to treat industrial effluent and wastewater and have demonstrated high efficacy in removing pollutants. However, some industrial effluent and wastewater contain contaminants that are extremely difficult to remove using standard physicochemical and biological processes. Previously, electrochemical and hybrid advanced oxidation processes (AOP) were considered a viable and promising alternative for achieving an adequate effluent treatment strategy in such instances. These processes rely on the production of hydroxyl radicals, which are highly reactive oxidants that efficiently break down contaminants found in wastewater and industrial effluent. This review focuses on the removal of contaminants from industrial effluents and wastewater through the integration of electrochemical and advanced oxidation techniques. These processes include electrooxidation, electrocoagulation/electroflocculation, electroflotation, photo-Fenton, ozone-photo-Fenton, sono-photo-Fenton, photo-electro-Fenton, ozone/electrocoagulation, sono-electrocoagulation, and peroxi/photo/electrocoagulation. The data acquired from over 150 published articles, most of which were laboratory experiments, demonstrated that the hybrid process is more effective in removing contaminants from industrial effluent and wastewater than standalone processes.
... 15 Chemical coagulation can bring high removal efficiency and a high quantity of wastewater but relatively high processing costs. 16 Fenton-like techniques generate a substantial amount of sludge and are thus impractical for completely degrading dye molecules. Almost all types of dyes may be separated from wastewater using the membrane process. ...
... 17 While biological treatment could be cost-competitive, it is less effective to deal with refractory organic wastes. 16 As a result, finding an effective and environmentally acceptable treatment technique with high removal efficiency and low cost is essential for completely removing dye molecules from industrial wastewater. ...
A continuous indirect electro-oxidation (EO) process was developed using graphite electrode to investigate the treatability of reactive turquoise blue RTB21 dye wastewater under specific operating conditions of initial pH, current density, hydraulic retention time (HRT), and electrolyte (NaCl) concentration. The experiments were performed in accordance with the central composite design (CCD), and the findings were used to create a model utilizing artificial neural networks (ANNs). According to the predicted findings of the ANN model, the MSE values for colour and COD removal efficiencies were estimated to be 0.748 and 0.870, respectively, while the R2 values were 0.9999 and 0.9998, respectively. The Multi-objective optimization using genetic algorithm (MOGA) over the ANN model maximizes the multiple responses: colour and COD removal efficiency (%). The MOGA generates a non-dominated Pareto front, which provides an insight into the process's optimum operating conditions.
... Pharmaceutical wastewater treatment is obstinate to treat due to its intense color, pungent odor, high COD and BOD, and low biodegradeability [67] . Several conventional treatment methods like activated sludge, trickling filter method, coagulation-flocculation, advance oxidation etc. were employed but they were unable to treat such wastewater completely [68] . ...
... Several conventional treatment methods like activated sludge, trickling filter method, coagulation-flocculation, advance oxidation etc. were employed but they were unable to treat such wastewater completely [68] . Commonly physiochemical and biological methods are preferred for pharmaceutical wastewater treatment but biological treatment considered as a key strategy in this regard [67] . Recently, microalgal systems have widely been adopted for this purpose and their detailed mechanism has been disussed by various reserachers [69] . ...
Exponential growth in the industrial sector causes the accumulation of toxic wastewater in the ecosystem. The unsafe disposal of such wastewater not only adversely affects the freshwater resources but also pose negative impact on the environment and human health due to the presence of heavy metals, organic/inorganic pollutants, and high amount of nitrogen, phosphorus, and sulfur in it. It demands for the effective wastewater treatment that depends on the effluent quality, industrial process, chemical/energy requirement, economic viability, operational flexibitily, and residual utilization. However, conventional treatment methods are unable to meet all the requriements which demands for the eco-friendly and economical alternatives. Currently, paradigm shift from wastewater treatment and dispoal of, to its utilization in circular biorefinery context is underway. In this context, microalgae-based industrial wastewater is vital option due its pollutant accumulation ability, environmental sustainablity, biorefinery potential, and zero-waste process chain development. This review highlights the characteristics of different industrial effluents and overviews the axenic and binary algal-treatment systems. Economical and technological barriers are the major hindrance in the implementation of algal-based treatment methods; for which biomass valorization has been briefly discussed. This review highlights the need of developing closed-loop integrated processes for wastewater treatment and reuse in sustainable manner. Further research in the development of such schemes specially at large-scale level must be the focus of future studies.
... However, the wastewater generated during drug and formulation development processes produces menacing consequences on ecological and human health if disposed of untreated into the environment. Pharmaceutical wastewater has severe color, pungent smell, high chemical oxygen demand (COD), and low biochemical oxygen demand (BOD) (Farhadi et al. 2012). The wastewater contains substances like buffers, soluble organics, suspended solids, chelators, antibiotics, heavy metals (lead, mercury, fluoride, arsenic, cadmium, chromium). ...
... Though the traditional physicochemical treatment methods are highly efficient, their high operation and installation costs, and incapability to degrade complex compounds divert the attention of environmentalists toward the development of newer, more powerful, sustainable, and cost-effective technologies for wastewater treatment and conservation of freshwater resources Singh et al. 2016). Biological methods are found better for pharmaceutical industry wastewater treatment over conventional techniques despite being less effective in eliminating stubborn carbon-based pollutants (Farhadi et al. 2012). However, neither physicochemical nor biological treatment methods are suggested as the most suitable procedures for high-strength and complicated pharmaceutical contaminants (Crouse et al. 2012). ...
Biochar-based nanomaterials have shown unbelievable prospective in managing various environmental contaminations and display immense enhancement in functional groups, surface active sites, pore size properties, catalytic degradation properties, etc. Their applications gaining increase interest due to the simplicity of preparation methods and their enhanced physicochemical properties. Therefore, the development of such nanomaterials has targeted in various research objectives including water/wastewater treatment, soil remediation, agriculture, and pollution. Sorption, catalysis, redox reaction and other structural and functional properties of biochar showed the alteration or removal of contaminations from the environment and are considered as incredible efficient ways in handling various challenging environmental issues. Considering the quick expansion of biochar-based nanomaterials. This chapter will serve the helpful information to summarize the various applications of this magical material in environmental cleanup, along with wastewater treatment, soil remediation, and agriculture advancement. In addition, synthesizing such efficient nanoparticles will provide a novel approach against various environmental concern and promise vast applications of nanotechnology.KeywordsBiocharNanomaterialWastewater treatmentSoil remediationAgriculture advancement
... The conventional activated sludge and trickling filter methods have also been employed in the removal of pharmaceutical compounds from wastewater, though it is not as successful [13]. Moreover, the biological methods are a cost-effective process but they are not as effective in stubborn carbon-based pharmaceutical wastewaters [3,14]. However, the use of specialized reactor systems such as anaerobic membrane bioreactor would be the acceptable approach for the removal of organic matter. ...
... Based on the growth performance at the pilot level study, they scale up the process up to HRAP (300,000 L) to ensure the scalability approach. Their investigation reported high biomass production of 0.98 ± 0.03 g/L and pollutant removal efficiencies were NH 4 + (~100%), 14 were removed from the aqueous phase above 50%, and 07 were removed ~90% of their initial concentrations. Moreover, 6 days of HRAP treatment successfully removed 69% of the studied pharmaceutical ingredients (25 of 36 studied). ...
Wastewater contains a munificent range of hazardous pollutants such as pharmaceuticals, and xenobiotics. Among them, ~79 types of different pharmaceuticals, and xenobiotics have been reported to exist in wastewater and were not effectively removed through the conventional wastewater treatment system. Recently, with increasing socioeconomic aspects and environmental awareness, societies are more alert and are trying to search for possible solutions to treat these polluted wastewaters. Thus, microalgae-based treatment systems are a promising way to remediate pharmaceuticals or xenobiotics wastewater partially (8–70%). However, some of the antibiotics at low concentrations (7.5 ng/L–500 μg/L) especially sulfa groups, oxytetracycline, erythromycin, pharmaceutical drugs, and growth hormones are toxic to the algal cells. Advancements in the microalgal treatment systems and optimization of growth conditions have increased the removal efficiency up to 85–99%. However, it depends on concentrations and types of microalga species. Thus, the review highlights the potential use of microalgae for pharmaceutical contaminants removal from wastewater and their mechanism. Moreover, the role of enzymes, the interaction of microalgal EPS, and the toxicity of pharmaceutical contaminants in microalgae are critically discussed. The current review briefly deliberates various factors affecting the growth of microalgae in the wastewater treatment process. Additionally, it critically discusses the different microalgae-based advancements in the treatment of pharmaceutical wastewater such as consortia and immobilization. In addition, it has disparagingly summarized the recent pilot-level study and reflected upon the published data highlighting the utilization of pharmaceutical and xenobiotic treated algal biomass into biofuels. Moreover, the challenges and conceptual integrated approach of the microalgae-based treatment process to maintain environmental sustainability has been elaborated in terms of circular bioeconomy.
... − 1 ). At higher current density, the rate of anodic metal dissolution increases that brings a greater amount of metal hydroxide flocs for pollutant removal (Bayar et al., 2011;Can and Bayramoglu, 2010;Farhadi et al., 2012). Also, at high current density, electro-flotation dominates over precipitation, while at low current density, precipitation or sedimentation dominates over flotation. ...
... pH is one of the most important parameters affecting the conductivity of the solution, contaminant distribution, zeta potential of charged particles, ionic characteristic of the organic molecules, electrode dissolution, and concentration of gas bubbles (Garcia-Segura et al., 2017;Shamaei et al., 2018;Thirugnanasambandham et al., 2016). It also governs the formation of hydrolyzed metal species and hence determines the coagulation mechanism (Farhadi et al., 2012;Garcia-Segura et al., 2017;Katal and Pahlavanzadeh, 2011). During EC, the pH of the solution changes to the neutral range (around 6-8) depending on the electrode material and initial pH (Al Aji et al., 2012;Can and Bayramoglu, 2010;Elabbas et al., 2016). ...
Over the last few decades, water pollution has become a major concern considering the adverse impact on environment and human health. Several methods and strategies have been investigated to the treatment of wastewater. Because of the introduction of more stringent pollution regulations and for sustainable development, recently EC has been shown as an emerging and alternative process to treat different types of wastewaters. This study represents a comprehensive review of reaction mechanisms for pollutants removal along with the operating parameters that need to be addressed for optimum application. The study demonstrated that the process has been applied effectively for the treatment of different types of industrial wastewaters as well as municipal and potable waters. In the case of treating highly contaminated wastewater, EC process is effective when it is used in combination with biological and/or other processes, and this combined treatment system can be considered as a potential treatment technology for recycling and reuse of effluents from diverse sources. This review also represents technological aspects of conversion of electrocoagulated sludge to valuable resources, H2 recovery, and the application of solar energy as an alternative source of electrical energy to apply the EC process more sustainably. Finally, this review highlighted some limitations with recommendations for promising research options that can make this technology more feasible for industrial applications.
... However, these methods are not efficient to remove micropollutants. Electrochemical technologies have reached a promising stage of development and they also can be used effectively to remove these compounds [6]. ...
... Advanced electrochemical oxidation processes (AEOPs) have emerged in recent decades as they have several advantages over other methods, such as high efficiency in mineralization of refractory organic compounds, ease of use as only simple equipment is required, few or no additional chemical reactants are needed, no wastewater is generated, safety as they can be carried out at room temperature and pressure, and can also be carried out using renewable energy sources (Brillas and Martínez-Huitle 2015;Moreira et al. 2017;Brito et al. 2021). Among AEOPs, anodic oxidation processes and electrocoagulation are the most popular processes (Zaied et al. 2020;Shen et al. 2022;Xie et al. 2022;Yasasve et al. 2022;Luo et al. 2022;Farhadi et al. 2012;Brillas and Martínez-Huitle 2015;Cai et al. 2018;Cano et al. 2012;Myburgh et al. 2019;Yang and Tang 2018;Martínez-Huitle and Panizza 2018). ...
... Xing et al. 2018). COD removal could be due to the otation of suspended solids, characterized by low density(Farhadi et al. 2012). Generally, the pH value controls the charge density and stabilizes suspended solids (López-Maldonado et al. 2014). ...
Vegetable oil refineries produce a large amount of wastewater, creating several environmental problems that threaten aquatic life. These wastewaters present significant challenges for treatment techniques due to their high and complex pollution characteristics. This study presents the application of flotation processes in acid medium or basic medium of vegetable oil refinery wastewater to reduce turbidity, oil, grease, chemical oxygen demand (COD), and phosphorus total, polyphenols, nitrates, phenolic compounds measured at 254 nm and color. Application of acid flotation reduced turbidity (96.9%), COD (79%), nitrate (97.8%), total phosphorus (99.8%), polyphenol (86.6%), absorbance at 254 nm (90.8%), oil and grease (98.5%) and color (96.6%). However, the application of basic flotation showed a reduction in turbidity (25.7%), COD (37.5%), nitrates (91.6%), total phosphorus (88%), polyphenols (66.3%), absorbance at 254 nm (64.7%), oil and grease (68.8%) and color (73.9%). Therefore, this flotation process in an acidic or basic medium can be considered among the most effective processes for reducing wastewater pollution from vegetable oil refineries.
... According to Faraday's Law, current density is directly proportional to the coagulant dosage. Therefore, the dissolution rate of iron electrode increases with current density and consequently more ferrous hydroxyl radicals are produced [58]. The heat production, unwanted reactions, excess oxygen evaluation, and cell voltage all increase with increasing current density; cell voltage is directly proportional to power consumption [59]. ...
Electrocoagulation with ozone and photo is a hybrid electrochemical and AOP techniques used to treat wastewater and industrial effluent. In the present study, the effects of combining O3, UV, and EC processes on color removal as well as the related COD removal and EEC from the treatment of DIW were assessed. The results showed that, compared to other hybrid processes like O3/EC, UV/EC, UV/O3, and single processes of EC, O3, and UV, the combined process of O3/UV/EC is significantly more effective for treating DIW in terms of COD removal (98.99%) and complete color removal with a required EEC of 9.7 kWhr m-3. Number of process variables, including reaction time (1 to 5 hr), O3 (0.8 to 4 g L-1), UV (8 to 32 W), current density (0.08 to 0.23 A dm-2), pH (1 to 11), COD (1000 to 6000 mg L-1), inter-electrode distance (0.75 to 3.75 cm), and combination of electrodes were studied to analyze how they affected. The optimum operating circumstances underwent testing and shown outstanding effectiveness in eliminating the COD and determination of EEC from DIW. Overall, it was clear from the results that combined treatment approaches could be more effective in removing the pollutant successfully from DIW.
... Módenes et al. 162 , on the other hand, treated tannery wastewater through a batch mode incorporation of solar photo Fenton assisted EC and reached significant enhancement in the reduction of COD and also sludge generation. In a work conducted by Farhadi et al. 163 EC, photoelectrocoagulation, peroxi-coagulation and peroxi-photoelectrocoagulation processes were compared in terms of treating a pharmaceutical wastewater. ...
I am thrilled to announce the publication of my paper titled:"The efficacious of AOP-based processes in concert with electrocoagulation in abatement of CECs from water/wastewater" in Nature journal. Through these years while working on electrocoagulation and industrial wastewater treatment, I have always felt the lack of a comprehensive review on electrocoagulation, especially with the focus on hybrid processes and also for the removal of new contaminants. Our goal was to cover this gap in this review paper. I hope you find it fruitful:
https://lnkd.in/g7ygkPZW/s41545-023-00239-9
... Blending of the various technologies can result in lower capital and operational expenditures. Combining electrochemical and Fenton seeks to accelerate organic degradation beyond what a single process might do under similar circumstances (Sajjad and Behnoush, 2012). Based on the reaction rate constant, the electrochemical Fenton technology had a synergetic effect of 1.7. ...
The aerated electrochemical Fenton procedure was investigated as a viable treatment approach for electrolytic degradation and decolourization of sanitary landfill leachate. The optimization effects of initial pH, applied voltage, H2O2 concentration and combination of iron electrodes on detoxification were demonstrated by COD and colour removal from stabilized leachate, respectively. The study illustrates that, under the optimum experimental parameters voltage of 4.5 V, electrolysis time of 90 min, H2O2 dosage of 5 g/L, pH 3, 99% of chemical oxygen demand (COD) and 100% colour are removed from stabilized leachate, and the biodegradability ratio of the five-day biochemical oxygen demand (BOD5) to COD increases from 0.1 to 0.72. In addition, the pure catalytic metallic iron anode and cathode electrode used in the electrochemical Fenton process was first electro-oxidized to Fe2+ for use during the Fenton reaction, then with Fe3+ that was reverted back to Fe2+ under the applied electrochemical-magnetic field, resulting in the iron dissolution and regeneration circuit (Fe2+/Fe3+/Fe2+). Additionally, Fe2+/Fe3+ served as bridges for agglomerates to coalesce into big, closely packed particles for better filterability and sedimentation action. As a preparatory step for the biochemical treatment, this technology has been effectively used to treat stabilized landfill leachate containing toxic refractory recalcitrant organics on a large scale. Additionally, by estimating the scientific experiment with a regression model approach for the outcomes, RSM software was employed in order to standardize the ECF treatment process, significantly reducing the number of test cases and trials.
... Therefore, the higher the value of the electric voltage used, the decrease in COD concentration after going through the electrocoagulation process will be even greater. In addition, the electric voltage applied to the electrocoagulation process determines the amount of coagulant dose and the formation of bubbles which greatly affect the agitation of wastewater and mass transfer at the electrodes (Farhadi et al., 2012). Wahyulis et al., (2014) have conducted research using a plate column electric reactor to degrade chromium waste in water using a voltage of 8 volts and obtained the best removal percentage of 98.82%. ...
Palm oil mills produce palm oil mill effluent (POME) which contains various dissolved organic compounds in the form of short fibers, hemicellulose, and their derivatives, protein, free fatty acids, a mixture of minerals and organic pigments such as anthocyanins, carotene, polyphenols, lignin and tannins. Organic compounds in this waste will cause problems such as increasing the value of TSS, TDS, and COD which can be a crucial environment for processing liquid waste in palm oil mills. One possible method to reduce the content of TSS, TDS, and COD is the electrocoagulation method. This study aims to determine the effect of variable flowrate, voltage, and distance between plates in the electrocoagulation process with a plate column electric reactor, and determine the optimum conditions for flowrate, voltage, and distance between plates. Optimum conditions are obtained at fflowrate3 L/min, 28 V voltage, 2 cm distance between plates with percent removal of TSS, TDS, and COD, respectively 49.30%; 49.40%; 60.30%.
... TDS concentration was reduced from 755 to 474 ppm and 490 to 460 ppm by each process after 90 min of treatments. Electric and light energy has been considered as the main inputs for the process [68]. EC method has been used to remove organics and divalent cations, which induces scaling. ...
Total dissolved solids (TDS) due to both geogenic and anthropogenic contaminations, is one of the preliminary as well as essential parameters among others to describe water quality. It includes organic and inorganic components, heavy metals, salts, other dissolved substances, and others due to indiscriminate disposal of untreated domestic and industrial effluents, urban and/or agricultural runoff which exists in the form of micro or nano level in nature. Higher TDS levels in water severely impact health and the environment. For instance, it causes gastrointestinal, cardiovascular, genotoxic, respiratory, skin, and hepatic effects in humans. High TDS level (> 500 ppm) results in excessive scaling in household appliances (e.g., pipes, heaters, and boilers) thereby reducing their efficiency. Therefore, the removal of TDS from various water matrices is taking paramount importance to minimize its impact on health and the environment. Various TDS removal technologies based on the membrane, ion, and temperature gradient are employed to treat water. In this review paper, several TDS removal technologies for instance reverse osmosis, nanofiltration, distillation, ultrafiltration, forward osmosis, precipitation, desalination, ion exchange, electrochemical techniques, electrodialysis, electrolysis, electrocoagulation, and adsorption are discussed in detail.
... Electrocoagulation was environmentally friendly for organic wastewater treatment. Without chemical addition, the sludge generated is more stable than chemical coagulation and sometimes can be floating by gas formed during the process 8,9 . Our previous research has been conducted to treat mocaf wastewater used electrocoagulation 3 . ...
Mocaf (modified cassava flour) is flour made from cassava through a microbial fermentation process. Mocaf wastewater has high pollutants, so it needs to be processed before being discharged into the environment. This study aims to treat wastewater of mocaf using a hybrid method: electrocoagulation combined with adsorption. The electrocoagulation process used solar cell electric current. The electrode used aluminium with a distance of 3 cm. The time process of electrocoagulation is 30 minutes. The adsorption process used activated carbon commercials. The concentration of the adsorbent is 3, 5, and 10 g/L. The time process of adsorption is 9 hours with sampling times of 1, 3, 6, and 9 hours. The analysis carried are COD, TDS, TSS, pH. The hybrid method of electrocoagulation and adsorption using activated carbon commercial adsorbent had an efficiency of COD removal up to 47,27% (3863 mg/L), optimum pH of wastewater mocaf 8,295; TDS 846 mg/L; TSS 500 mg/L on concentration adsorbent ten g/L and 6 hours adsorption time. The hybrid method of electrocoagulation and adsorption could reduce pollutants in mocaf wastewater and the result under the quality standard of pH, TDS, and TSS.
... Colloids may be entrapped in a flock or they may become enmeshed by its "sticky" surface as flocks settle. The removal of colloids from solution through this way is called sweep coagulation [150]. ...
Electrocoagulation is one of the promising processes to treat a variety of wastewater including electroplating wastewater, distillery effluent, pulp, and paper mill effluent, etc. This method is well applicable to treat wastewater of chemical oxygen demand range in 1,000–20,000 mg/dm3. In addition, the electrocoagulation process is very effective in the removal of metal or heavy metal from the wastewater depending on the nature of the metal and its concentration. However, a number of technologies such as coagulation, adsorption, precipitation, and membrane separation are also avail-able to treat such type wastewater but in the last few decade, electrocoagulation method gains more popularity due to its versatility and environmental compatibility. The present article gives a critical and concise review of electroplating effluent towards heavy metals removal from electroplating effluent. Additionally, the role of electrocoagulation on the removal of various pollutants from different industrial wastewater including mining, textile, pulp, paper mill, distillery, chemical, paint, petroleum, and tannery are also summarized. The concept of electrocoagulation and its operating parameters are also explained in detail.
... Electrocoagulation techniques for treating PWW have become popular as a result of improvements in which alternative sources of energy are harnessed to power the processes. The COD elimination efficiency of normal electrocoagulation and its hybrid counterparts shows that peroxi-electrocoagulation have the highest removal efficiency followed by peroxi-photoelectro-coagulation, photoelectrocoagulation and then electrocoagulation (Farhadi et al., 2012). ...
Pharmaceutical industries are imminent for the survival of any contemporary society as their products are valuable for the populace's health and wellness. However, the wastes of these industries have become a nuisance with severe implications on human health and ecosystem, especially in many developing countries where they are discharged indiscriminately into the environment , either untreated or poorly treated. Pharmaceutical Manufacturing Waste (PMW) effluents have been reported to possess a high BOD and COD, as well as recoverable APIs of various classes of pharmaceuticals. Moreover, antibiotic residues in these effluents are implicated in the progression and spread of antibiotic resistance in the aquatic and agroecosystem. Globally, the diverse activities of various pharmaceutical industries, owing to their diverse products, have resulted in difficulty in developing universal management and treatment protocols. Consequently, regulatory bodies/institutions find it challenging to monitor waste disposal practices of these industries adequately, primarily owing to their non-disclosure policies of intellectual properties. Hence, to a large extent, the onus for a sustainable society regarding PMWs lies in the decision and policies of these industries. Therefore, this review aims to foster informed policy-making decisions regarding waste management practices of pharmaceutical industries.
... This decline in the degradation rate can be attributed to the dominance of Fe(OH) 3 and other Fe 3+ species in the solution. The as-generated species will cause a rapid decomposition of hydrogen peroxide (H 2 O 2 → H 2 O + ½ O 2 ), which reduces the oxidation capacity of the EF process (Farhadi et al., 2012). In addition, the precipitation of Fe(OH) 3 from Fe 3+ ions may prevent Fe 3+ /H 2 O 2 reaction, thus hindering the regeneration of ferrous ions (Fard and Barkdoll, 2018). ...
This work focuses on the degradation of the hazardous azo dye Naphthol Blue Black (NBB) utilizing an innovative approach combining electro-Fenton (EF), ultra-violet (UV), and ultra-sound (US) processes while varying the operating parameters (concentration of iron and dye, pH, current intensity). Under the optimum experimental conditions, an excellent degradation efficiency of the NBB dye is achieved after 60 min, i.e., 98, 95, and 65% for EF, UV, and US processes, respectively. The addition of persulfate significantly improves the efficiency and accelerates the kinetics of the NBB degradation. Combining all processes assisted with persulfate achieved 99% NBB degradation within a very short contact time of 2 min and 98% reduction in COD after 55 min. The as-obtained outstanding performance associated with the synergistic effects of EF/US/UV alongside the addition of persulfate can be adopted to degrade other hazardous substances.
... In the electrocoagulation process, electricity is used to produce hydroxide ions and metal ions to remove contaminants from the solution. This process has been reported as a successful treatment method for a wide range of pollutants such as dyes (Song et al., 2007), biodiesel wastewater (Chavalparit and Ongwandee, 2009), pharmaceutical wastewater (Farhadi et al., 2012), oil tanning effluent (Maha Lakshmi and Sivashanmugam, 2013), industrial wastewater (García-García et al., 2015), pretreated coke wastewater (Ozyonar and Karagozoglu, 2015), and also polluted groundwater (You and Han, 2016). Electrocoagulation has attracted the attention of many researchers due to its numerous benefits, including reduced sludge volumes compared to conventional coagulation and flocculation processes, no need for coagulants, ease of operation, faster retention times and low operating costs (Huda et al., 2017). ...
In the electrocoagulation process, passivation or corrosion of the electrodes is one of the biggest challenges that cause a drop in treatment effectiveness. In this study, the effect of polarity switching was investigated, for the first time, in an attempt to enhance electrocoagulation treatment's ability to remove chemical oxygen demand (COD) and color from pretreated landfill leachate. Moreover, the ratio of the anode to cathode surface area and rotating electrode were examined in light of experimental results. The effect of different parameters, including the stirring speed, initial leachate pH, electrical current density, anode to cathode surface area ratio, and polarity switching time on system efficiency, was evaluated using the one-factor-at-a-time (OFAT) classical method. According to the results, polarity switching resulted in an almost 18% increase in COD removal, 14% increase in color removal, 13% decrease in electrical energy consumption (EEC), 51% decrease in the specific sludge production (TSS/COD), and improved electrode performance compared to non-polarity switching mode. The findings of this research showed the highest COD and color removal efficiencies, which were 34% and 67%, respectively, in a 120 min period, a stirring speed of 135 rpm, the initial leachate pH of 9, the current density of 14.4 mA/cm², the anode/cathode surface ratio of 0.35, and the polarity switching time of 300 s.
... This phenomenon is caused by electrode passivation, in which an oxidised layer forms on the anode's surface, increasing the anode's polarisation resistance and limiting the release of both coagulant species and bubbles, lowering treatment removal efficiency after increasing the voltage beyond 4 V. In an electrocoagulation procedure, Sajjad Farhadi et al [25] discovered that the optimum pH and voltage were 7 and 40 V, respectively, with COD elimination of 43.22% during a 60-minute treatment interval. ...
The aim of the present work was to provide a viable and active way to remove COD and colour from landfill leachate treated by adopting combined process of electrocoagulation and solar photo Fenton process. Coagulating agents such as metal hydroxides are created by the electrolysis process through self-sacrificial electrodes. Aluminum and iron dissolves at the anode and hydrogen gas is generated at the cathode when aluminium and iron electrodes are utilised. The contaminants interact with the coagulating agent to generate enormous organic flocs. The leachate was obtained from a landfill in Madurai and then it was characterized in terms of its major predominant pollutants. In this study, the electrocoagulation process was used in conjunction with the solar photo Fenton process to treat the leachate under ideal conditions of pH=7, NaCl=2g/L, voltage=4V, Al & Fe electrodes and inter electrode distance=3cm with a COD and colour removal effectiveness of 75% and 76%, respectively. Furthermore, the effluent from the electrocoagulation process was treated using a solar photo Fenton process at pH = 3, H2O2=10g/L and Fe2+=1g/L with COD and colour reduction effectiveness of 90% and 91%, respectively. In this combination of treatment systems, leachate biodegradability increased from 0.35 to 0.73, favoring the biological oxidation process in conventional treatment plants. This research demonstrates that employing this paired electrocoagulation–solar photo Fenton to treat landfill leachate can achieve consistent treatment effects with high removal efficiencies, and that it is an acceptable treatment technique for landfill leachate.
... (fiG. 3) produces wastewater with a high chemical oxygen demand (up to 28,640 mg l -1 ) and comparatively low biochemical oxygen demand and low inorganic contaminants 122,123 . Using biochar as an adsorbent for organic pollutants can be part of the solution for pharmaceutical wastewater treatment 124 . ...
Biochar, a carbon-rich material made from the partial combustion of biomass wastes, is an emerging material of interest as it can remediate pollutants and serve as a negative carbon emission technology. In this Review, we discuss the application of biochar in municipal wastewater treatment, industrial wastewater decontamination and stormwater management in the context of sustainable development. By customizing the biomass feedstock type and pyrolysis conditions, biochar can be engineered to have distinct surface physicochemical properties to make it more efficient at targeting priority contaminants in industrial wastewater treatment via adsorption, precipitation, surface redox reactions and catalytic degradation processes. Biochar enhances flocculation, dewatering, adsorption and oxidation processes during municipal wastewater treatment, which in turn aids sludge management, odour mitigation and nutrient recovery. The addition of biochar to sustainable drainage systems decreases potential stormwater impact by improving the structure, erosion resistance, water retention capacity and hydraulic conductivity of soils as well as removing pollutants. The feasibility of scaling up engineered biochar production with versatile, application-oriented functionalities must be investigated in collaboration with multidisciplinary stakeholders to maximize the environmental, societal and economic benefits.
... In the electrocoagulation process, electricity is used to produce hydroxide ions and metal ions to remove contaminants from the solution. This process has been reported as a successful treatment method for a wide range of pollutants such as dyes (Song et al., 2007), biodiesel wastewater (Chavalparit and Ongwandee, 2009), pharmaceutical wastewater (Farhadi et al., 2012), oil tanning effluent (Maha Lakshmi and Sivashanmugam, 2013), industrial wastewater (García-García et al., 2015), pretreated coke wastewater (Ozyonar and Karagozoglu, 2015), and also polluted groundwater (You and Han, 2016). Electrocoagulation has attracted the attention of many researchers due to its numerous benefits, including reduced sludge volumes compared to conventional coagulation and flocculation processes, no need for coagulants, ease of operation, faster retention times and low operating costs (Huda et al., 2017). ...
... Overall, the addition of H 2 O 2 to the EC process resulted in the complete decolourization of distillery effluents along with a total COD reduction of 86% and energy consumption of 1.1 kW h/m 3 . Farhadi et al., 2012 evaluated the performance of peroxi-EC process for the removal of high concentrations of COD from pharmaceutical effluent [103]. In the EC process, 4 Fe electrodes were used having an inter-electrode distance of 2.5 cm between them and is connected to a DC power source. ...
Electrocoagulation (EC) is an established wastewater treatment method that has been widely explored for a broad range of wastewater pollutants due to its ease of operation, versatility, eco-friendly nature and low footprint. EC as a pretreatment process can significantly reduce the total energy usage, while also improving the quality of treated water. This review paper provides an in-depth assessment of the various operational parameters and electrode materials used during the electrocoagulation treatment of wastewater. The recent advancements in EC reactor designs and optimization studies have been reviewed. The effectiveness of combining the EC process with other water treatment techniques viz. membranes, oxidation, chemical and adsorption processes have also been validated in this review paper. Different combinations of EC process with microfiltration (EC-MF), ultrafiltration (EC-UF), nanofiltration (EC-NF), reverse osmosis (EC-RO), ozonation (EC-O3), peroxi-electrocoagulation (EC-H2O2) and electro-oxidation (EC-EO), have been elaborately discussed and summarized. The results are critically analyzed, and modifications have been suggested to improve the performance efficiency. Moreover, case studies regarding the application of the EC process from three different wastewater sources have been demonstrated. The economic aspects of the EC process and recommendation for its betterment is also made. Taken together, this review paper effectively illustrates the progress and current achievements in both standalone and hybrid EC process towards wastewater pollutant treatment, which can present new insights on improving the wastewater treatment scenario with promising environmental applications. The critical analysis and suggestions provided in this review paper will greatly enhance the scientific knowledge of the readers.
... However, based on the literature, there are many methods applied to remove this type of target pollutants from water. Part of them, traditional methods, such as coagulation, filtration, adsorption, however, results showed that these conventional techniques are insufficient, unable to reach degradation of organic substances and present several limitations for wastewater treatment [15][16][17][18][19][20][21]. ...
Gamma irradiation degradation of the extensively used muscle relaxant in the world methocarbamol (MET) was studied. MET aqueous solutions were irradiated by gamma rays emitted by a Cobalt 60 source at doses of 1-4 kGy.Our findings demonstrated that gamma irradiation degraded more than 98.5% of MET. Absorption spectra analysis revealed that when increased irradiation dose the absorption bands declined with complete disappearance at 4 kGy dose. Additionally, the most radiolytic degradation rate was recorded at neutral pH, marked by Total Organic Carbon (TOC) removal rate of 98% reflecting the total mineralization of MET at 4 kGy. In-depth spectrophotometric analyses advocated a pseudo-first-order type of MET degradation kinetics. The obtained apparent rate constant value was kapp, MET = (0.02167 ± 0.0006) min-1. Gas chromatography-mass spectrometry (GC-MS) allowed the detection of 3-(o-Methoxyphenoxy)-1,2 propanediol,2-Methoxyphenol, 1,2,3 propanetriol, 1,2-dihydroxybenzene and 1,2,4 benzentriol identified as by-products generated during radiolytic degradation. Finally, an outline of the degradation mechanism was suggested according to the obtained by-products.
... 9) BDD (⋅OH) + R → BDD + mCO 2 + nH 2 O Until today, electrochemical treatment methods have been used in the treatment of industrial wastewater containing many pollutants and high organic content such as brewery (Dizge et al. 2018;Wysocka and Masalski, 2018), bilge (Akarsu et al. 2016), inorganics and heavy metals (Deniz et al. 2018;Deveci et al. 2019), laundry (Dimoglo et al. 2019;Akarsu et al. 2020), olive oil (Ntaikou et al. 2020), pharmaceutical (Farhadi et al. 2012), textile (Núñez et al. 2019). ...
The significant increase in the turnip sector has brought a wastewater problem that needs to be managed. In this study, turnip juice wastewater treatment was studied using the electrocoagulation/electroflotation and electrooxidation processes. Independent process parameters such as electrode type (aluminum–aluminum, iron–iron, boron-doped diamond–platinum and graphite–platinum), current density (25–100 A/m2) and retention time (15–180 min) were investigated for the optimization of treatment conditions. Removal efficiencies of chemical oxygen demand and total phenol were studied. It was determined that the optimum removal efficiencies in both electrocoagulation/electroflotation and electrooxidation processes were the same under the conditions of 100 A/m2 current density, pH 5.4, and 45 min reaction time. Here, 100% removal efficiencies were achieved for both chemical oxygen demand and total phenol. The operating cost of the electrocoagulation/electroflotation process was calculated as 1.58 $/m3, while it was determined as 0.61 $/m3 for electrooxidation for the optimum removal parameters. It is seen in laboratory scale test results that electrocoagulation/electroflotation and electrooxidation processes are applicable/feasible for the treatment of turnip juice wastewater.
... Until today, EC has been successfully applied to treat brewery (Dizge et al., 2018;Wysocka & Masalski, 2018), bilge (Akarsu et al., 2016), inorganics and heavy metals (Deniz & Akarsu, 2018;Deveci et al., 2019), laundry (Akarsu & Deniz, 2020;Dimoglo et al., 2019), olive oil (Ntaikou et al., 2020), pharmaceutical (Farhadi et al., 2012), textile (Núñez et al., 2019), and herbicide . On the other hand, the activated sludge process is the most common treatment technology used in the treatment of many industrial wastewaters, including oilfield wastewater due to the high efficiency, cost-effectiveness, and environment-friendliness (Azizi et al., 2021;Chavan & Mukherji, 2008;Tong et al., 2013). ...
The present work aims to study chemical oxygen demand (COD), oil‐grease, and color removal from vegetable oil wastewater by combined electrocoagulation and activated sludge processes. For this purpose, the sample was pretreated using electrocoagulation by various optimization parameters such as electrode type (Al–Al and Fe–Fe), current density (100–400 A/m ² ), pH (2–8), and electrolysis time (15–180 min). The results showed that 89.3% of COD, 100% of oil‐grease, and 66.2% of color were removed by electrocoagulation under the conditions of 300‐A/m ² current density, pH 2, and 180‐min reaction time with Al–Al electrode pairs. Then, the effluent of electrocoagulation was treated by an activated sludge process. The results depicted that the activated sludge process was also effective for vegetable oil wastewater treatment and it enhanced 98.9% COD and 79.2% color removal efficiency. The effluent of the combined process was very clear, and its quality exceeded the direct discharge standard of the water pollution control regulation. The laboratory‐scale test results indicate that the combined electrocoagulation and activated sludge process is feasible for the treatment of vegetable oil wastewater.
Practitioner points
Vegetable oil wastewater was treated by combination of electrocoagulation and activated sludge processes.
The combined electrocoagulation and activated sludge processes supplied 99.9% COD, 100% oil‐grease, and 93.0% color removal efficiency.
The laboratory‐scale test results indicate that the combined EC‐SBR processes were feasible for the treatment of vegetable oil wastewater.
... Electrocoagulation (EC) is a process in which metal-ion coagulants are directly added to the feed water by in situ electrochemical dissolution of an anode. EC is a promising approach that has been widely used as pretreatment in the industrial wastewater (Farhadi et al. 2012;Lianos et al. 2014;Shenvi et al. 2015). It has many potential advantages such as (i) portability, (ii) reduced use of chemicals, (iii) decreased energy consumption and increased treatment capacity, and (iv) suitability for use in predesigned packaged plants (Moussa et al. 2017). ...
Low pressure reverse osmosis (LPRO) has been increasingly used in advanced treatment of pulp and paper wastewater (PPWW) for the purpose of water reuse. However, membrane fouling is a major problem encountered by full-scale RO systems due to the organic and inorganic contents of the feedwater. Electrocoagulation (EC) as an effective treatment for foulants removal can be applied in pre-filtration. Therefore, the LPRO membrane fouling mechanism and the membrane fouling control performance by EC treatment were investigated in this study. EC pretreatment could reduce the membrane fouling and improve the membrane flux by 31%, by effectively removing and/or decomposing the organic pollutants in PPWW. Fluorescent spectrometry analyses of the feedwater and the permeate revealed that humic acid-like and fulvic acid-like organics in PPWW were the major foulants for the LPRO membranes. Fourier transformation infrared spectrometry results confirmed that the organic foulants contained benzoic rings and carboxylic groups, which were typical for organic substances. EC effectively removed organic pollutants containing functional groups such as carboxylic acid COH out-of-plane bending, olefin (trans), and NH3⁺ symmetrical angle-changing. Moreover, the extended Derjaguin-Landau-Verwey-Overbeek model suggested that the membrane filtered 30-min EC-treated PPWW had the strong repulsion force to foulants due to the higher cohesion energy (12.1 mJ/m²) and the lower critical load, which theoretically explained the reason of EC pretreatment on membrane fouling control.
... When comparing the results with other studies, it is found that they are similar or superior, in some cases, to those reported by: Elazzouzi, et al. [29], for urban wastewater electrocoagulation/flocculation treatment (COD: 85%, BOD: 84%; TSS: 94%; and PO4: 99%); Farhadi, et al. [30], for COD removal from pharmaceutical wastewater by electrocoagulation processes (< 35%); Wang, et al. [31], for COD removal from domestic wastewater by electrocoagulation (62%); Hutnan, et al. [32], for COD removal from urban wastewater by electrocoagulation (COD: 50-80%); Chen, et al. [33], for COD removal from wastewater (restaurants) by electrocoagulation (COD: 95-99%); Pouet and Grasmic, [34] for COD removal from urban wastewater by electrocoagulation (COD: 70-80%); Fajardo, et al. [35], for synthetic wastewater treatment by electrocoagulation (phenols: 84.2%; COD: 40.3%) and for olive oil effluent wastewater treatment (phenols: 72.3%; COD: 20.9%); Bazrafshan, et al. [36], for phenol removal from aqueous solutions by the electrocoagulation process using iron (94.7%) and aluminum (98.0%) electrodes; Irdemez, et al. [37], for phosphates removal from wastewater by electrocoagulation using aluminum electrodes (99-100%); Kuokkanen, et al. [38], for phosphates removal from synthetic wastewater by electrocoagulation (96%); and Franco, et al. [39], for phosphates removal from wastewater by electrocoagulation (99%). ...
The technical feasibility of the continuous flow electrocoagulation process for hospital wastewater treatment was evaluated. The wastewater physicochemical characterization was performed according to the chemical oxygen demand (COD), biochemical oxygen
demand (BOD), total suspended solids (TSS), naproxen, phenol and phosphates parameters. An experimental Box-Behnken design and statistical response surface methodology (RSM) were used to evaluate the simple and combined effects of the independent parameters (pH, potential, retention time), and to optimize
electrocoagulation process conditions, considering the COD response variable. The removal percentage was: COD (75.5%), BOD (59.2%) phenols (80.7%), phosphates (85.3%), TSS (75.6%) and naproxen (55.7%), under optimal electrocoagulation conditions at pH (7.92), potential (40 V) and retention time (15 min). The electrocoagulation process proved to be an efficient and technically viable alternative for
hospital wastewater treatment.
Production of certain pharmaceuticals generates wastewater with a high ammonia load, posing economic and environmental burdens. Recovering ammonia as a nitrogen fertilizer can alleviate these burdens and is vital from a circular economy perspective. For this purpose, this study, jointly performed by a research university and a large pharma company, evaluated the use of Hollow fiber membrane contactors (HFMC). The experiments were conducted using real pharmaceutical wastewater in two separate laboratories at two process scales (bench and pilot) and two operating modes (batch and continuous). The study evaluated the effect of feed concentration, flow rates, and process configuration and described the results using a single-parameter (mass transfer coefficient K) mathematical model. We then used the model to design scaled-up batch and continuous processes, based on which we performed a detailed economic assessment. A robust and consistent ammonia removal and recovery were obtained for all the experimental conditions tested. The model adequately described the empirical results, and K was similar across all the experiments in this study, which were conducted in practically relevant conditions. Both batch and continuous process designs were found feasible, increasing process flexibility. The economic evaluation revealed that acid and base consumption, rather than the initial investment, is the most significant expense. The cost of membranes, although relatively high, had little contribution to the overall expenses. Revenues from selling the recovered nitrogen as ammonium-sulfate fertilizer reduces the evaluated net cost of the novel treatment to a minimum of $3.76 per kgN - a potential cost savings of up to 29% relative to the current treatment ($5.28). Therefore, applying HFMC to recover nitrogen from pharmaceutical wastewater is promising from both economic and environmental viewpoints.
The high-efficiency and environmentally-friendly electro-oxidation (EO) would lose its competitive edge because of the production of oxychloride by-products (ClOx-), which has not yet drawn significant attention in academic and engineering communities. In this study, the negative effects of the electrogenerated ClOx- were compared among four commonly used anode materials (BDD, Ti4O7, PbO2 and Ru-IrO2) in terms of ClOx- interference on the evaluation of electrochemical COD removal performance and biotoxicity. Apparently, the COD removal performance of various EO systems were highly enhanced with increasing current density in the presence of Cl-, e.g., the amounts of COD removed by various EO systems from the phenol solution with an initial COD content of 280 mg L-1 at 40 mA cm-2 within 120 min decreased in the order: Ti4O7 of 265 mg L-1 > BDD of 257 mg L-1 > PbO2 of 202 mg L-1 > Ru-IrO2 of 118 mg L-1, which was different from the case with the absence of Cl- (BDD of 200 mg L-1 > Ti4O7 of 112 mg L-1 > PbO2 of 108 mg L-1 > Ru-IrO2 of 80 mg L-1) and the results after removing ClOx- by anoxic sulfite-based method (BDD of 205 mg L-1 > Ti4O7 of 160 mg L-1 > PbO2 of 153 mg L-1 > Ru-IrO2 of 99 mg L-1). These results can be ascribed to the ClOx- interference on COD evaluation, the extent of which decreased in the order: ClO3- > ClO- (where ClO4- cannot impact COD test). The highest overrated electrochemical COD removal performance of Ti4O7 may be associated with its relatively high production of ClO3- and the low mineralization extent. The chlorella inhibition ratio of ClOx- decreased in the order: ClO- > ClO3- >> ClO4-, which accounted for the biotoxicity increasement of the treated water (PbO2 68%, Ti4O7 56%, BDD 53%, Ru-IrO2 25%). Generally, the inevitable problems of overrated electrochemical COD removal performance and biotoxicity increasement induced by ClOx- should deserve significant attention and effective countermeasures should be also developed when employing EO process for wastewater treatment.
Suatu industri asam fosfat menghasilkan air limbah dari berbagai proses. Diantaranya air limbah dari kegiatan blowdown, pencucian dan kondensat. Air limbah tersebut akan diolah pada unit Waste Water Treatment (WWT) dengan metode chemical coagulation floculation. Penggunaan bahan kimia yang tinggi serta perlengkapan mekanik dalam chemical preparation memiliki operating cost yang cukup besar. Oleh sebab itu, diperlukan suatu metode yang dapat menjawab masalah tersebut. Metode tersebut adalah elektrokoagulasi. Dalam penelitian ini akan digunakan reaktor uji elektrokoagulasi yang memiliki kapasitas volume limbah cair sebesar 13,5 liter dengan waktu kontak selama 30 menit. Jenis plat elektroda yang digunakan adalah aluminium dan besi, nilai tegangan 10 V, 20 V, 30 V, dan 40 V dan jarak plat adalah 0,5 cm dan 1 cm. Hasil dari penelitian ini efisiensi removal COD, TSS, dan Fluoride terbesar adalah 87,24%, 83,3%, dan 93,4% dengan menggunakan tegangan 40 Volt pada plat elektroda aluminium yang berjarak 0,5 cm dengan rasio benefit costnya sebesar 1,039. Kata kunci: Chemical Oxygen Demand (COD), Elektrokoagulasi, Fluoride, Total Suspended Solid (TSS).
The color and Chemical Oxygen Demand (COD) reduction in distillery industrial effluent (DIW) was investigated
utilizing photo (UV), sono (US), electrocoagulation (EC), UV + US, UV + EC, US + EC, and US + UV + EC
technologies. The empirical study demonstrated that the UV + US + EC process removed almost 100% of colour
and 95.63% of COD from DIW while consuming around 6.97 kWh m− 3 of electrical energy at the current density
of 0.175 A dm− 2
, COD of 3600 mg L− 1
, UV power of 32 W, US power of 100 W, electrode pairings of Fe/Fe,
inter-electrode distance of 0.75 cm, pH of 7, and reaction time of 4 h, respectively. The values found were much
greater than those produced using UV, US, EC, UV + US, UV + EC, and US + EC methods. The influence of
various control variables such as treatment time (1–5 h), current density (0.075–2.0 A dm− 2
), COD (1800–6000
mg L− 1
), inter-electrode distance (0.75–3.0 cm), electrode pairings (Fe/Fe, Fe/Al, Al/Fe, Al/Al), UV (8–32 W),
and US (20–100 W) on the color and COD reduction were investigated to determine the optimum operating
conditions. It was observed that, an increase in treatment time, current density, UV and US power, decrease in
the COD, and inter-electrode distance with Fe/Fe electrode combination improved the COD removal efficiency.
The UV and US + EC processes’ synergy index was investigated and reported. The results showed that, the US +
UV + EC treatment combination was effective in treating industrial effluent and wastewater.
The present work aims to fill a scientific gap regarding the treatment of wastewater from the enzymatic pretreatment of biodiesel production (WEPBP), as well as the identification of organic contaminants present in this complex matrix. Different treatment strategies were proposed for the removal of total organic carbon (TOC) and chemical oxygen demand (COD) from WEPBP. The interesting combination of O3/H2O2/UV-Vis and electrocoagulation (EC) process was studied in two setups, with the EC process applied prior to O3/H2O2/UV-Vis and vice versa. Further, the innovative hybrid system based on the photo-Fered-Fenton process with O3 addition (PEF-Fere-O3) was preliminarily studied for WEPBP treatment. The hybrid system provided the best results for the WEPBP treatment when the reactor was operated at pH of 4.5, 65 mg O3 L-1 and 10000 mg H2O2 L-1, UV-Vis was used as the irradiation source, and the current intensity of 3.0 A. Removals of 45% of TOC and 68.7% of COD were reached within 45 min. Oleic acid, linoleic acid, and Diisooctyl phthalate (DIOP) were the main organic contaminants identified in the WEPBP as determined by Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Acute toxicity assays with the bio indicator Artemia salina were carried out in untreated and treated WEPBP samples, indicating that the PEF-Fere-O3 treatment decreased the amount of contaminants present in the WEPBP as well as reduced the toxicity levels and increased biodegradability index, suggesting its great potential for the treatment of complex industrial wastewaters.
Disposal of untreated pharmaceutical waste into water bodies is a growing threat to the aquatic ecosystem and humans as well. Among various physicochemical, advanced oxidation, and bioremediation processes adopted, bioremediation emerges as the most environmentally friendly and economically viable alternative to manage this serious environmental concern. The main focus of the chapter is on nanobiotechnology that utilizes nanoscale materials for removing toxic compounds from wastewater. The nanomaterials have a size even smaller than one billionth of a meter and possess unique properties including high absorption potential, huge surface area, eco-friendly fabrication, and strong affinity toward organic and inorganic compounds. The use of novel nanomaterials for the sustainable treatment of pharmaceutical wastewater is a favorite option for environmental engineers these days. Different nanomaterials used for the treatment of pharmaceutical containing aqueous medium and wastewaters like electrospun lignin nanofibers, polyaniline/ZrO2 nanocomposite, Cu-TiO2 single-walled carbon nanotubes, curcumin-loaded nanostructured lipid carrier, Fe3O4/Au nanocomposite, Fe3O4-chitosan nano-adsorbent, TiO2/ONLH nanocomposites, ZnO nanoparticles, ZnO/sepiolite heterostructured nanomaterials, Ni-Al layered double hydroxide nanoparticles, tungsten/carbon nanotube heterojunction nanocomposite, organic-inorganic hybrid TiO2 doped with molybdenum, MnOx/ nano-graphite/2-ethylanthraquinone/activated carbon cathode, graphene-based nanomaterials, and multi-wall carbon nanotubes/titanium oxide (MWCNT/TiO2) nanocomposite have been discussed in the literature. Classification of the nanomaterials has been also highlighted. The chapter attempts to provide all the useful information on novel nanotechnology employed for pharmaceutical wastewater management.
Increasing discharge of saline wastewater (SWW) from different industries and environmental risks associated with it has compelled researchers to search for efficient treatment methods and safe disposal techniques. Unfortunately, several industries such as agro-food, oil & gas, tannery, and pulp & paper require brine solution units to obtain a finished product that further elevates the salinity of discharged wastewater to a magnitude of 1-3% by weight of NaCl. Among the conventional treatment procedures, electrochemical technologies proved to be more efficient, robust and cost-effective. Electrocoagulation (EC), an electrochemical based technology that produces in situ coagulant which ultimately assist in pollutant removal. It is even more suitable for the treatment of saline water as salinity increases conductivity which further enhances the EC process efficiency. However, the elevated anodic dissolution may increase the cost which can be reduced by using scrap metals as sacrificial electrodes out of iron and aluminum. The mechanism of salt removal from SWW using EC is similar to other pollutant removal mechanisms as salt species being coagulated by the metal hydroxides and are further removed as sludge. However, optimization of process parameters in EC is essential to maintain a balance between anodic passivation and higher metal dissolution so as to make the process efficient. This review paper highlights the theory of the EC technology, process parameters, potential application and recent developments of EC for the treatment of various types of SWW as well as economical assessment associated with this technology. Most of the recent research concerning EC for SWW treatment has been concentrated on the pollutant-specific evaluation without paying special attention to the process optimization, process modelling and commercial usage. This review further outlines the challenges with the recommendations for encouraging research options that can potentially enhance the EC performance, lower the operational costs and expand its range of applications for SWW treatment.
The electrochem. behavior of PbO2 and synthetic B-doped diamond thin film electrodes (BDDs) was studied in acid media contg. 4-chlorophenol (4-CP) by bulk electrolysis under different exptl. conditions. To quantify the electrochem. activity of a given electrode, for the electrochem. oxidn. of org. compds. (4-CP), the current efficiency of the anodic oxidn. was normalized taking into consideration mass-transport limitations. The normalized current efficiency (j) was defined as the ratio between the current efficiency of the investigated anode to the current efficiency of an ideal anode which has a very fast oxidn. rate, resulting in a complete combustion of orgs. to CO2. The results showed that even if the complete combustion of 4-CP was achieved at both PbO2 and BDD anodes, the latter give higher j. The difference in reactivity of the electrogenerated hydroxyl radicals on the anode surface, is proposed to explain the high j values obtained using B-doped diamond anodes. [on SciFinder (R)]
BACKGROUND: The present study describes an electrocoagulation process for treating laundry waste-water using aluminum plates. The effect of various parameters such pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated.
RESULTS: Experimental results showed that by increasing HRT, treatment efficiency increases but beyond 45 min changes are negligible. Among the results for chemical oxygen demand (COD), phosphorus, detergent, colour and turbidity, the lowest decrease was found for phosphorus. The larger the HRT, the greater the electrical current needed to achieve constant voltage and temperature in the system. The pH of the influent is a very significant variable which affects the treatment of laundry waste-water considerably, the optimal range being 6.0–8.0. In addition, it was found that the pH increases from 8.3 to more than 10 over the first hour of treatment after which the pH remains relatively constant. Finally, kinetic analysis indicates that the adsorption system obeys a second-order kinetic model.
CONCLUSION: The aluminum hydroxide generated in the cell decreases the concentration of pollutants in laundry waste-water to a permissible level. It is concluded that, compared with other treatment processes, electrocoagulation is more effective in treating laundry waste-water under appropriate conditions. Copyright
Electrocoagulation (EC) process using aluminum electrodes is proposed for removing fluoride from treated industrial wastewater originated from steel industry. Effects of different operating conditions such as temperature, pH, voltage, hydraulic retention time (HRT) and number of aluminum plates between anode and cathode plates on removal efficiency are investigated. Experimental results showed that by increasing HRT, removal efficiency increases but after 5 min changes are negligible. Therefore, the total HRT required is only 5 min. The more HRT, the more electrical current is needed in order to achieve to constant voltage and temperature in system. In addition, it is found that pH value decreases from 6.91 to 4.6 during first 10 min but it increases up to 9.5 during 50 min. After treatment, the fluoride concentration was reduced from initial 4.0-6.0 mg/L to lower than 0.5 mg/L. The pH of the influent is found as a very important variable which affects fluoride removal significantly. The optimal range for the influent is 6.0-7.0 at which not only effective defluoridation can be achieved, but also no pH readjustment is needed after treatment. Moreover, increasing number of aluminum plates between anode and cathode plates in bipolar system does not significantly affect fluoride removal. Finally, the kinetic analysis is done for the system which indicates that the adsorption system obeys the second-order kinetic model.
Over the past few years, pharmaceuticals are considered as an emerging environmental problem due to their continuous input and persistence to the aquatic ecosystem even at low concentrations. Advanced oxidation processes (AOPs) are technologies based on the intermediacy of hydroxyl and other radicals to oxidize recalcitrant, toxic and non-biodegradable compounds to various by-products and eventually to inert end-products. The environmental applications of AOPs are numerous, including water and wastewater treatment (i.e. removal of organic and inorganic pollutants and pathogens), air pollution abatement and soil remediation. AOPs are applied for the abatement of pollution caused by the presence of residual pharmaceuticals in waters for the last decade. In this light, this paper reviews and assesses the effectiveness of various AOPs for pharmaceutical removal from aqueous systems.
The objective of this work was to investigate the oxidation of p-hydroxybenzoic acid by the Fenton's reagent. Batch experiments were carried out to investigate the influence of the most important process variables: hydrogen peroxide and ferrous salt concentrations, pH, and temperature. The optimal results obtained indicate that p-hydroxybenzoic acid can be effectively degraded using Fenton's oxidation within 10-min reaction time by using a molar ratio H2O2: p-hydroxybenzoic acid of 4:1 and H2O2:Fe2+ of 15:1, at 30 degrees C and pH=3.0. The behavior of ORP and pH along the reaction time for different values of R (molar ratio H2O2: p-hydroxybenzoic acid) was also discussed. A pseudo-first order model was applied to describe the oxidation kinetics of p-hydroxybenzoic acid by Fenton's reagent.
Degradation of MTBE, a common fuel oxygenate, was investigated using anodic Fenton treatment (AFT) and by comparison with classic Fenton treatment (CFT). The AFT system provided an ideal pH environment (2.5-3.5) for the Fenton reaction and utilized gradual delivery of ferrous iron and hydrogen peroxide, which was more efficient than batch CFT to degrade MTBE and its breakdown products. The optimized ratio of ferrous iron to hydrogen peroxide for AFT was determined to be 1:5 (in mmol). Depending on the initial concentration, MTBE was completely degraded by the optimized AFT in 4-8 min. The breakdown products found during the treatment of MTBE were acetone, t-butyl formate, t-butanol, methyl acetate, acetic acid, and formic acid, which were all completely degraded by the optimized AFT in 32 min. Based on the experimental results and other work reported in the literature, degradation mechanisms of MTBE and its breakdown products in AFT and CFT were proposed. Generally, reactions are initiated by H-abstraction by *OH, generating carbon-centered radicals which undergo various reactions including alpha/beta-scission within the radical, combination with oxygen, oxidation by ferric ion, and reduction by ferrous ion before generating the final oxidation products. Radical combination with oxygen (and the reactions thereafter) and radical oxidation by ferric ion are believed to be the most important pathways in the overall fate of the generated radicals, while radical reduction by ferrous ion is the least important. By elucidating the reaction kinetics and mechanisms of MTBE degradation in the anodic Fenton system, this study offers a potential remediation technique for treating MTBE-contaminated wastewater.
The degradation of azo dye C.I. Acid Red 14 (AR14) was investigated using cast iron in the absence and presence of low frequency ultrasound (59 kHz). The effects of pH, amount of cast iron ([Fe](0)) and initial concentration of AR14 ([dye](0)) on the degradation of AR14 by cast iron combined with low frequency ultrasound had been assessed. The degradation followed the first-order kinetics model. The first-order rate constant of AR14 degradation by cast iron was 7.50 x 10(-2) min(-1) while that by US-cast iron was 2.58 x 10(-1) min(-1). A 3.4-fold increase in the reaction rate was observed in the presence of ultrasound compared with that of absence of ultrasound. This kinetic effect is quantitatively accounted for a simple kinetic model based on the reaction of Fe(II) from cast iron in aqueous solution with sonochemically produced H(2)O(2) (Fenton's reaction). This latter effect illustrates a simple way of achieving a substantial improvement in the efficiency of sonochemical degradation reactions. It was found that for azo dye AR14, the rate of color decay was the first order with respect to the visible absorption of the dye. The destruction of the naphthalene rings in azo dyes was slower than that of color. A significant mineralization of AR14 was observed.
A combination of the classical Fenton reaction (Fe(II)+H2O2) with UV light, the photoassisted Fenton reaction, has been investigated for the treatment of landfill leachate. The investigation has been carried out with an experimental set-up to establish the optimal treatment conditions. The degradation rate of organic pollutants is strongly promoted by the photoassisted Fenton reaction. The degradation rate depends on the amount of H2O2 and Fe(II) added, pH value, and radiation intensity. At a specific energy input of 80 kW m−3 the oxidation rate was increased to six times the rate without radiation (0 kW m−3). At the higher radiation intensity of 160 kW m−3 the degradation rate was about two times faster than at that of 80 kW m−3. Due to the regeneration of the consumed Fe(II) ions through the irradiation, the amount of ferrous salt to be added can be remarkably reduced. The optimum conditions were obtained with 1.0 x 10−3 mol 1−1 Fe(II) added, a pH value of 3, and a molar ratio of COD :H2O2=1:1. At aCOD volume loading ofless than 0.6 kg m−3 h−1, a COD degradation of more than 70% could be obtained with an energy input of 80 kW m−3.
A new bipolar electrocoagulation and electroflotation process was developed to treat laundry wastewater. In this new process, electrocoagulation and electroflotation were carried out simultaneously in a single reactor. The operating parameters such as initial pH, hydraulic residence time (HRT) and current density were investigated. The unique design of the reactor made it possible for the effective removal of turbidity, COD, phosphate and surfactant (MBAS) in a wide pH range (5–9) at a short HRT (5–10 min). The pilot scale tests (1.5 m3/h) were carried out successfully in three different places suggested that the bipolar electrocoagulation–electroflotation process was feasible for the treatment of laundry wastewater.
Oxidation of the nitroaromatic explosives namely, 2,4,6-trinitrophenol (PA), ammonium picrate (AP), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) by Fenton's reagent has been investigated in this study. The initial concentrations of nitroaromatics were in the range of 1.0×10−5 to 3.0×10−4M. For the Fenton oxidation of the four nitroaromatics, the structural characteristic is the major factor affecting the decomposition rate rather than the interference effect coming from the oxidation intermediates. Oxidation rate of the explosives in the Fenton process were in the following sequence: DNT>PA>AP>TNT. The results were in good agreement with kinetic model, assuming the pseudo-steady-state hypothesis of hydroxyl radical formed by the Fenton reaction. Thus, a half-life prediction model was proposed and compared with the half-lives calculated from pseudo-first-order equation to prove the interference effect resulted from the oxidation intermediates.
The effect of temperature was studied on the efficiency of soluble COD removal and bacterial community development during the aerobic biological treatment of a pharmaceutical wastewater. Using wastewater and bacterial inoculum obtained from the full-scale facility treating this wastewater, batch laboratory cultures were operated at 5°C intervals from 30°C to 70°C. Following four culture transfers to allow for bacterial acclimation, residual soluble COD levels were measured and bacterial community fingerprints were obtained by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments. Soluble COD removal efficiency declined as temperature increased from 30°C (62%) to 60°C (38%). Biological treatment of this wastewater failed to occur at temperatures higher than 60°C. Gradual shifts in bacterial community structure were detected as temperature increased, including a concomitant reduction in the number of different bacterial populations. The impact of temperature on a two-stage biological treatment process was also compared. Better soluble COD removal was achieved when both reactors were operated at 30°C compared to a system where the two stages were consecutively operated at 55°C and 30°C. These results indicate that operation of aerobic biological wastewater treatment reactors at elevated temperatures can have adverse effects on process performance.
The chemical process industries (CPI) must treat wastewaters containing a wide variety of contaminants, ranging from toxic organics like phenol, benzene, other aromatics, formaldehyde, and amines, to inorganics such as sulfite, sulfide, mercaptans, and cyanide, to heavy metals such as hexavalent chrome. These wastewaters also have a wide range of concentrations and combinations of contaminants. The streams must be treated as inexpensively as possible and in a safe manner, preferably by processes that are easy to operate on-site and that require a minimum of labor and technical know-how. And, of course, the ultimate goal of this treatment is that the treated water meet all federal, state, and local discharge regulations. One available wastewater treatment technology that few engineers seem to be familiar with is the Fenton reactor. In this advanced oxidation process, toxic wastewater is reacted with inexpensive ferrous sulfate catalyst and hydrogen peroxide in a simple, nonpressurized (typically batch) reactor to yield (if reacted to completion) carbon dioxide and water. This article offers guidance on the use of this process by first explaining the mechanisms of Fenton`s chemistry and then outlining how to apply it to industrial wastewater treatment.
In this work, the electrocoagulation process using aluminum and iron electrodes has been used to treat synthetic wastewaters polluted with three different types of pollutant models: kaolin suspensions, dye solutions, and oil-in-water emulsions. It was obtained that both electrodes can achieve high efficiencies (above 80%) in the treatment of the three wastes. However, there are strong differences in the electrochemical coagulation or breakup mechanism that can be explained in terms of the speciation of the dissolved metals and especially in terms of the significant concentrations of monomeric and polymeric ionic species that appear in the treatment with aluminum electrodes. In every case, sweep coagulation explains the coagulation of kaolin suspension with both aluminum and iron electrodes. However, in the case of aluminum, the neutralization charge mechanism should also be considered for low reagent doses. The coagulation of EBT (Eriochrome Black T) solutions and the breakup of O/W emulsions (oil-in-water emulsions) have been explained by the binding of the pollutants to metal hydroxide precipitates. This binding is promoted for aluminum electrodes because of the adsorption of cationic reagent species on the surface of the aluminum hydroxide.
The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. This paper deals with the batch removal of the reactive textile dye Remazol Red RB 133 from an aqueous medium by the electrocoagulation method using aluminum electrodes. The effects of wastewater conductivity, initial pH, current density, stirring rate, dye concentration, and treatment time on the decolorization efficiency and energy consumption have been investigated. Aluminum hydroxypolymeric species formed during an earlier stage of the operation efficiently remove dye molecules by precipitation, and in a subsequent stage, Al(OH)3 flocs trap colloidal precipitates and make solid−liquid separation easier during the flotation stage. These stages of electrocoagulation must be optimized to design an economically feasible electrocoagulation process.
The degradation pathways exhibited by three phenyl-urea herbicides: isoproturon (ISO), chlortoluron (CHLT) and chloroxuron (CHLOX), during photocatalytic (on supported TiO2 under intense solar radiation) and electro-Fenton (EF) treatment were investigated by HPLC coupled to electrospray ionization single and tandem mass spectrometry (HPLC–ESI-MS and MS/MS). In particular, the dependence of degradation efficiency on the initial concentration ratio between substrate and Fe(III) ion was assessed for the EF treatment and a 1:1 ratio was found to be optimal. A comparison between photocatalytic and EF degradation, in terms of structures, number and evolution on a similar time scale (up to 5 h) of by-products, was then performed. Similar reactivities were found in the two cases, hydroxylation (single and multiple, with H, alkyl groups or Cl substitution, depending on the herbicide) and demethylation on the dimethylamino moiety (eventually followed by hydroxylation) being the most relevant processes in by-products generation. The scale of EF degradation efficiency for the three herbicides was almost identical to the photocatalytic one (ISO > CHLT ≈ CHLOX), yet electro-Fenton proved to be a more efficient process, generally leading to a faster further degradation of by-products.
The electrochemical oxidation of 2,4-dinitrophenol (2,4-DNP) aqueous wastes has been studied using both, bulk electrolysis and voltammetric techniques. To carry out the bulk electrolysis, a bench-scale plant with a single compartment electrochemical flow cell was used. Boron-doped diamond (BDD) materials were used as the anode and stainless steel (AISI 304) as the cathode. According to the obtained results, a simple mechanistic model has been proposed. The oxidation of 2,4-DNP leads to the appearance of phenol and quinonic compounds and to the release of the nitro groups from the aromatic ring, in a first step. In a second step, these organics are transformed into carboxylic acids (mainly maleic and oxalic acid). The process ends with the formation of carbon dioxide (CO2). The effects of the waste characteristics (composition and pH) and of the operation parameters of the process (temperature and current density) have also been studied in this work. The complete removal of the organic compounds contained in the waste has been obtained in all essays.
The electrochemical degradation of saturated solutions of herbicides 4-chloro-2-methylphenoxyacetic acid, 2-(4-chlorophenoxy)-2-methylpropionic acid and 2-(4-chloro-2-methylphenoxy)propionic acid in 1 M HClO4 on a boron-doped diamond (BDD) thin film anode has been studied by chronoamperometry, cyclic voltammetry and bulk electrolysis. At low anodic potentials polymeric products are formed causing the fouling and deactivation of BDD. This is reactivated at high potentials when water decomposes producing hydroxyl radical as strong oxidant of organics. Electrolyses in a batch recirculation system at constant current density ≥8 mA cm−2 yielded overall decontamination of all saturated solution. The effect of current density and herbicide concentration on the degradation rate of each compound, the specific charge required for its total mineralization and instantaneous current efficiency have been investigated. Experimental results have been compared with those predicted by a theoretical model based on a fast anodic oxidation of initial herbicides, showing that at 30 mA cm−2 their degradation processes are completely controlled by mass transfer. Kinetic analysis of the change of herbicide concentration with time during electrolysis, determined by high-performance liquid chromatography, revealed that all compounds follow a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids have been identified using this technique and a general pathway for the electrochemical incineration of all herbicides on BDD is proposed.
A combined electrocoagulation and electroflotation process was designed to reduce Cr6+ to Cr3+ first and then to remove the total Cr from wastewater to a value below 0.5 mg/L. Acidic condition was employed in the reduction of Cr6+ and neutral conditions were found to be beneficial for the coagulation of the precipitates of Cr(OH)3 and Fe(OH)3. The formation of Fe(OH)3 was ensured by sparging compressed air in the coagulation unit through a draft tube. The air not only oxidizes Fe2+ produced electrically, but also helps to mix the water for a better coagulation of the particles. The two-stage electroflotation arrangement can separate the solids from the wastewater to a value of less than 3 mg/L with total Cr less than 0.5 mg/L. The residence time required is about 1.2 h. The optimal conditions for the treatment are: charge loading about 2.5 Faradays/m3 water, pH value in the coagulation unit is 5–8. The power consumption is less than 1 kW h/m3 water at the conductivity of 1.5 mS/cm. When aluminum ions are either added or produced in situ in the coagulation unit, the treated wastewater can be discharged without any filtration.
A novel Electro-Fenton (EF–Fere) method, applied H2O2 and electrogenerated ferrous ion, was investigated for treating the hexamine-containing wastewater. The performance of Fe2+ generation in the electrolytic system was first evaluated, including the factors of the cathode material, initial pH, initial ferric concentration (Fei), and current density. When initial pH exceeded 2.5, the current efficiency dramatically decreased, which was due to the formation of Fe(OH)3. Between 3000 and 10,000 mg/l of Fei, the initial current efficiency of Fe2+ generation was almost constant (85–87%), which dropped sharply to 39% at 1000 mg/l. In EF–Fere experiments, the COD removal efficiency attained above 94% after 5 h of reaction. The relationship between the temperature, dissolved oxygen, and COD was discussed. The changes in hexamine and its oxidation intermediates (methanol, formaldahyde, formate, ammonium and nitrate) during the reaction were also investigated. Three additional experiments using H2O2/Fe2+, H2O2/Fe3+, and direct electrolysis were also conducted to treat the hexamine-containing wastewater for comparison. The results showed that the EF–Fere method was the most efficient.
The electrochemical oxidation of Anthraquinone dye (Alizarin Red S) has been studied on boron-doped diamond (BDD) electrodes on acid medium by cyclic voltammetry and bulk electrolysis. Galvanostatic electrolyses cause complex oxidation reactions that lead to the incineration of Alizarin Red S. The analyses of the chemical oxygen demand (COD) and the total organic carbon (TOC) during the galvanostatic electrolyses at BDD anodes confirm that the electro-oxidation of Alizarin Red S leads to CO2. The complete removal of organic compounds contained in the waste has been obtained at low and high current densities.
Aluminium and iron salts are widely used as coagulants in water and wastewater treatment and in some other applications. They are effective in removing a broad range of impurities from water, including colloidal particles and dissolved organic substances. Their mode of action is generally explained in terms of two distinct mechanisms: charge neutralisation of negatively charged colloids by cationic hydrolysis products and incorporation of impurities in an amorphous hydroxide precipitate (‘sweep flocculation’). The relative importance of these mechanisms depends on factors such as pH and coagulant dosage. Alternative coagulants, based on prehydrolysed forms of aluminium and iron, are more effective than the traditional additives in many cases, but their mode of action is not completely understood, especially with regard to the role of charge neutralisation and hydroxide precipitation. Some basic features of metal hydrolysis and precipitate formation are briefly reviewed and the action of hydrolysing coagulants is then discussed, with examples from the older literature and from some recent studies on model systems. Dynamic monitoring of floc formation and breakage can give useful insights into the underlying mechanisms. Although the results can be reasonably well explained in terms of established ideas, a detailed understanding of the ‘sweep flocculation’ mechanism is not yet available. There are also still some uncertainties regarding the action of pre-hydrolysed coagulants.
This paper reviews the development, design and applications of electrochemical technologies in water and wastewater treatment. Particular focus was given to electrodeposition, electrocoagulation (EC), electroflotation (EF) and electrooxidation. Over 300 related publications were reviewed with 221 cited or analyzed. Electrodeposition is effective in recover heavy metals from wastewater streams. It is considered as an established technology with possible further development in the improvement of space-time yield. EC has been in use for water production or wastewater treatment. It is finding more applications using either aluminum, iron or the hybrid Al/Fe electrodes. The separation of the flocculated sludge from the treated water can be accomplished by using EF. The EF technology is effective in removing colloidal particles, oil & grease, as well as organic pollutants. It is proven to perform better than either dissolved air flotation, sedimentation, impeller flotation (IF). The newly developed stable and active electrodes for oxygen evolution would definitely boost the adoption of this technology. Electrooxidation is finding its application in wastewater treatment in combination with other technologies. It is effective in degrading the refractory pollutants on the surface of a few electrodes. Titanium-based boron-doped diamond film electrodes (Ti/BDD) show high activity and give reasonable stability. Its industrial application calls for the production of Ti/BDD anode in large size at reasonable cost and durability.
The present study is to investigate the treatment of sodium dodecyl sulfate (SDS) surfactant wastewater by the peroxi-electrocoagulation process. The electrochemical oxidation of aqueous surfactant solution has been studied by batch electrolysis experiments. Experiments were conducted to examine the effects of pH, amount of hydrogen peroxide, current density, electrolysis time and time after the peroxi-electrocoagulation, conductivity and surfactant concentration on the surfactant removal. The experimental results showed that SDS in aqueous phase was effectively removed by the peroxi-electrocoagulation method. The batch experimental results revealed that the overall SDS removal efficiency reached 81.6% for initial concentration 60 mg L−1. The optimum current density, optimum pH and electrolysis time were 0.5 mA cm−2, 5 and 10 min, respectively. Mean energy consumption was 1.63 kWh (kgSDS)−1. Results show that the pseudo-second-order equation provides the best correlation for the removal rate of SDS.
The characteristics of restaurant wastewater were investigated. High oil and grease contents were detected. Electrocoagulation was used to treat this type of wastewater. Different electrode materials and operational conditions were examined. Aluminum was preferred to iron. Charge loading was found to be the only variable that affected the treatment efficiency significantly. The optimum charge loading and current density were 1.67–9.95 F/m3 wastewater and 30–80 A/m2 depending on the wastewater tested. The removal efficiency of oil and grease exceeded 94% for all wastewaters tested. The experimental results also show that the electrocoagulation can neutralize wastewater pH. Several mechanisms associated with pH variation are proposed.
The goal of coagulation of fine disperse latex particles of suspensions by dosing with iron ions is to enhance suspension clarification, promote sedimentation and improve their filterability. Two kinds of iron dosing were studied; by directly adding iron chloride or iron sulphate to suspensions or by electrolytic decomposition of iron electrodes (electrocoagulation process, EC). The chemical and electrical processes were examined by varying the pH value and the iron ions concentration in order to determine the optimal operating conditions. To minimise the energy consumption in EC, the suspension conductivity and the current density were varied. This paper shows that flocs in EC-treated suspensions had a higher density and tended to be larger than flocs formed in suspensions dosed with iron chloride or iron sulphate. The kinetics of settling and filtration of EC-treated suspensions were accelerated, demonstrating the interest of EC as an alternative to chemical conditioning.
This study makes a comparison between UV/Nano-TiO(2), Fenton, Fenton-like, electro-Fenton (EF) and electrocoagulation (EC) treatment methods to investigate the removal of C.I. Acid Blue 9 (AB9), which was chosen as the model organic contaminant. Results indicated that the decolorization efficiency was in order of Fenton>EC>UV/Nano-TiO(2)>Fenton-like>EF. Desired concentrations of Fe(2+) and H(2)O(2) for the abatement of AB9 in the Fenton-based processes were found to be 10(-4)M and 2 x 10(-3) M, respectively. In the case of UV/Nano-TiO(2) process, we have studied the influence of the basic photocatalytic parameters such as the irradiation time, pH of the solution and amount of TiO(2) nanoparticles on the photocatalytic decolorization efficiency of AB9. Accordingly, it could be stated that the complete removal of color, after selecting desired operational parameters could be achieved in a relatively short time, about 25 min. Our results also revealed that the most effective decomposition of AB9 was observed with 150 mg/l of TiO(2) nanoparticles in acidic condition. The effect of operational parameters including current density, initial pH and time of electrolysis were studied in electrocoagulation process. The results indicated that for a solution of 20 mg/l AB9, almost 98% color were removed, when the pH was about 6, the time of electrolysis was 8 min and the current density was approximately 25 A/m(2) in electrocoagulation process.
Electrocoagulation is an electrochemical wastewater treatment technology that is currently experiencing both increased popularity and considerable technical improvements. There has been relatively little effort to better understand the fundamental mechanisms of the processes, particularly those that could provide design parameters to optimize the performances of this relatively simple and inexpensive technique. In a research programme to delineate the mechanisms of the fundamental processes involved in, the authors have realized that the technology has been insufficiently reviewed with emphasis on the fundamentals and their relationship to the performance of this technology. This paper presents an in-depth discussion and consideration of the factors that need to be addressed for optimum performance of this technology. Recent improvements of this technique and the theoretical model studies are also reviewed.
Electro-Fenton denitrification of a model wastewater was studied using platinized titanium electrodes in a batch electrochemical reactor. The model wastewater was prepared from components based on the real aquaculture effluent with nitrate concentrations varying from 200 to 800 mg L(-1). The technical as well as scientific feasibility of the method was assessed by the relationship between the most significant process variables such as various Fenton's reagent to hydrogen peroxide ratios (1:5; 1:20 and 1:50) and current densities (0.17 mA cm(-2), 0.34 mA cm(-2) and 0.69 mA cm(-2)) and their response on denitrification efficiency in terms of nitrate degradation using central composite Box-Behnken experimental design was determined. The goodness of the model was checked by the coefficient of determination R(2) (0.9775), the corresponding analysis of variance P>F and a parity plot. The ANOVA results indicated that the proposed model was significant and therefore can be used to optimize denitrification of a model wastewater. The optimum reaction conditions were found to be 1:20 Fenton's reagent/hydrogen peroxide ratio, 400 mg L(-1) initial nitrate concentration and 0.34 mA cm(-2) current density. Treatment costs in terms of electricity expenditure at 0.17, 0.34 and 0.69 mA cm(-2) was 7.6, 16 and 41.8 euro, respectively, per kilogram of nitrates and 1, 2 and 4 euro, respectively, per cubic meter of wastewater.
A study was conducted to demonstrate the advantages of electro-Fenton process and related electrochemical technologies based on Fenton's reaction chemistry. The electrochemical technology had gained significance due to its ability to prevent pollution problems. Its main advantage was its environmental compatibility, as the electron was the clean reagent. The technology also offered advantages, such as versatility, high energy efficiency, amenability of automation, and safety. It was revealed that the electrochemical technologies had the ability to decontaminate wastewaters containing a large variety of organic pollutants in a wide range of experimental conditions. All these technologies were suitable for destroying the initial pollutant and mineralize the solutions treated.
Attempts were made in this study to examine the combined polyferric sulfate (PFS) coagulation, Fenton and sedimentation process for treatment of non-degradable antibiotic fermentation wastewater. The experimental results indicated that 66.6% of color and 72.4% of chemical oxygen demand (COD) were removed under the optimum conditions of PFS dosage 200mg/L and pH 4.0. In addition, optimal parameters of Fenton process were determined to be 150 mg/L of H(2)O(2) dosage, 120 mg/L of FeSO(4) and 1h of reaction time. When Fenton treated effluent was controlled at pH 7.0, the pollutants could be further removed by sedimentation process. The overall color, COD and suspended solids (SS) removal reached 97.3%, 96.9% and 86.7% under selected conditions, respectively. Thus this study might offer an effective way for wastewater treatment of antibiotics manufacturer and pharmaceutical industry.
The electrochemical removal of a synthetic solution containing 120mgL(-1) of alizarin red has been studied by electro-Fenton process using a gas-diffusion cathode to produce in situ hydrogen peroxide by oxygen reduction. The effect of operating conditions such as Fe(2+) concentration, applied current, solution pH and temperature on the efficacy of the process was investigated. It is shown that alizarin red and its products may be effectively degraded by the OH radicals produced by the reaction between the Fe(2+) ions and the electrogenerated H(2)O(2). After 4h of electrolysis COD removal was only 45% when no ferrous ions were added to the solutions, while the presence of ferrous ion greatly improved COD removal up to more than 90%. In particular 1.0mM was the optimal concentration of ferrous ions and the single step or the stepwise addition of Fe(2+) ions enables the same COD removal. The oxidation rate increased with increasing of current density and temperature and with decreasing of pH. The UV-vis analysis indicated that the discoloration of the solution occurs simultaneous with the destruction of aromatic rings and alizarin red is oxidised firstly to colourless intermediates (mainly phthalic acid, small carbonyl species) and then to carbon dioxide.