Fenton Method Research Articles

Fenton Technology for Wastewater Treatment: Dares and Trends

Fenton reaction remains an efficient technique for decomposing recalcitrant organic contaminants. Nevertheless, traditional Fenton response has many lim-itations like the necessity of acidic pH circumstance, the formation of iron sludge and the need for elevated chemical introductions. Procedures like het-erogeneous Fenton, fluidized-bed Fenton, employment of chelating products and in situ formations of Fenton’s reagent have been examined as likely solu-tions to such drawbacks. Bello et al. [1] presented an excellent discussion of the restrictions of Fenton reaction and the fresh manners for dealing with them and this work focuses on its main findings. The heterogeneous Fenton method stays the most largely examined thanks to the expansion achieved in catalysis. The fluidized-bed Fenton method has the capacity to diminish sludge formation and ameliorate technology efficiency. Chelating chemicals are employed to performing homogeneous Fenton at circumneutral pH, even if the potentially decisive impact of many chelating products remains a source of worry. In situ formation of Fenton’s reagent via bio-electrochemical technique (bio-electro-Fenton) seems to be a likely manner to diminish the price related to Fenton’s reagent. Despite the progress registered in the Fenton technologies, the classical process, and its ameliorated versions, membranes processes remain fundamental for secure wastewater treatment. As sure barriers towards pollution dispersal, processes such as nanofiltration should be coupled to Fen-ton techniques.

Bisphenol A degradation by Fenton Advanced Oxidation Process and operation parameters optimization

Bisphenol A (BPA) is a kind of environmental endocrine disrupting substance, which has been used as an organic chemical as unsaturated polyester resin. The degradation of BPA includes biological methods, physical adsorption and chemical oxidation, all which have their own disadvantages. Owing to its strong oxidization capability and stable treatment performance, Fenton process can degrade organic substances at a high reactive rate and stably effective. In this paper, Fenton oxidation method was optimized to remove BPA in water, during which the intermediate products were analysed to examine its degradation path. The optimal conditions of degradation of BPA by Fenton method were a ratio of C (H2O2)/C (Fe2+) of 10, a pH of 3.5, and the degradation rate increased with the increasing of reaction temperature. It was found that Fenton could break the chemical bond at the junction of BPA and isopropyl group to produce p-diphenol, phenol, isopropyl phenol and other intermediate products.

Dissolution and Degradation of Spent Radioactive Cation Exchange Resin by Fenton Oxidation Combining Microwave

This study introduced a significantly effective approach called the microwave-enhanced Fenton method to degrade spent radioactive cation exchange resin. Compared with the Fenton (99% after 180 min) and photo-Fenton (90% after 198 min) reactions, this unique microwave-enhanced Fenton reaction has the highest degradation rate for spent radioactive cation exchange resin degradation (98.55% after 60 min). Carbon dioxide, sulfate and small molecular compounds were produced in the degradation of cation exchange resin, as determined by XRD and FT-IR. A model for the microwave-enhanced Fenton degradation mechanism of cation exchange resin was constructed. Microwaves were implemented to boost the concentration of hydroxyl radicals in the Fenton reaction so that the cation resin infiltrated and formed a channel to facilitate entrance of hydroxyl groups into the interior of the resin. This paper provides a method for accelerating the treatment of spent radioactive ion exchange resin, which could exert a signifi- cant influence on the degradation pathway for radioactive organic matter.

Application of a modified Fenton method for landfill leachate treatment – a case study

Application of a modified Fenton method for landfill leachate treatment – a case study

Identification and photolytic characteristics of benzoquinone intermediates in photo Fenton system

ABSTRACT The predecessors believed that the rufous intermediates of benzene compounds degradation was quinhydrone. This article corrects this misperception. This paper takes benzene, phenol, chlorobenzene and nitrobenzene as the substrates, and p-benzoquinone as the reference; we studied the degradation law of benzene compounds in Fenton system. During the process of benzene, phenol, chlorobenzene and nitrobenzene degradation by Fenton method, it is found that the use of hydroxyl radical system for visible light would be enhanced as soon as the rufous substances were produced, which indicated that rufous substances have elevated photosensitivity. The analyses via high performance liquid chromatography, mass spectrometry, infrared spectroscopy and UV–visible spectroscopy indicate the common rufous substance is a kind of polymer formed by p-benzoquinone and oxygen. The yield of photoinduced electrons, singlet oxygen and superoxide anion radicals are carried to higher level by the rufous substance. The outstanding photosensitivity of the rufous substance provides a new idea for the treatment of wastewater containing benzene compounds by visible light.

Preparation of bead-type NiOx(OH)y catalyst for hypochlorite conversion and reactive brilliant red K-2BP degradation

In order to develop a low-cost NaClO/NiOx(OH)y process instead of Fenton method for treating refractory wastewater, a convenient bead-type hypochlorite conversion NiOx(OH)y catalyst was prepared by simply impregnating Ni-precursor over alumina and then oxidizing with persulfate (PS) in strong alkali solution. The influence of catalyst preparation conditions on the synthesis of NiOx(OH)y was studied. A series of batch experiments were carried out to verify the effective conversion of NaClO and investigate the influence of different parameters. Orthogonal test showed that Ni2+ concentration had the greatest effect on the catalyst performance, while PS dosage had the least effect. The best combination of catalyst preparation parameters is impregnation of the γ-Al2O3 beads in 1.5 M Ni2+ solution followed by oxidation in a mixture of 5 % PS and 1.94 % NaOH. The best catalyst sample was characterized by XRD, SEM and FTIR. XPS tests showed that the oxygen content in the catalytic layer increased with the Ni2+ solution concentration, and the oxygen content in the catalytic layer with the best performance reached 90.22 %. SBET of the samples is 283−292 m2 g−1; Ni(OH)2 accounted for ∼2/3 of the nickel content and NiOOH accounted for ∼1/3. The catalyst significantly improved COD and color removal rate of reactive brilliant red (RBR) K-2BP with low operation cost. The scavenger furfuryl alcohol proves the important role of atomic oxygen in decolorization of RBR K-2BP by NaClO/NiOx(OH)y system. During the reuse of the catalyst, the catalytic performance did not decline. The prepared catalyst has great potential in wastewater treatment.

Treatment of semi-aerobic aged-refuse biofilter effluent from treating landfill leachate with the Fenton method

Semi-aerobic aged-refuse biofilter (SAARB) can achieve good treatment efficiency for organics and nitrogen ammonia, but the effluent of SAARB from treating landfill leachate (SAARB leachate) has high chemical oxygen demand (COD), compared to the discharge standard (100 mg/L), and high humification degree. In this study, the conventional Fenton method was used in the advanced treatment of SAARB leachate. Fluorescent components in SAARB leachate were identified and tracked with parallel factor (PARAFAC) analysis, and the influencing factors, i.e., Fe2+ dosage, n(H2O2/FeSO4) ratio, initial pH, and reaction time, on the removal of fluorescent components were systematically investigated. UV–Vis spectra show the structural transformation of dissolved organic matter (DOM) in SAARB leachate. Results show that SAARB leachate mainly contains two fluorescent components: fulvic-like substances [C1; excitation (Ex)/emission (Em) (nm), (245)280/405] and humic-like substances [C2; Ex/Em (nm), (260)360/435]. A higher Fe2+ dosage, longer reaction time, and acidic conditions increased the degradation efficiency of organics, but excess H2O2 inhibited the treatment process. Under optimum Fenton parameters (Fe2+ dosage of 5 mmol/L, n(H2O2/FeSO4) ratio of 8, initial pH of 4, and reaction time of 60 min), removal rates of C1 and C2 were 52.97% and 77.81%, respectively. UV–Vis spectra indicate that the Fenton reaction can destroy unsaturated conjugated bonds, decreasing the humification degree, hydrophobicity, molecular weight, and condensation degree. Finally, the biodegradability (represented by BOD5 (biochemical oxygen demand for 5-days)/COD) greatly increased (from 0.05 to 0.36), thus benefiting further biological treatment. The results provide suggestions and guidance for practical applications in landfill leachate treatment.

Degradation of recalcitrant organics in nanofiltration concentrate from biologically pretreated landfill leachate by ultraviolet-Fenton method

In this work, we investigated the feasibility of degrading recalcitrant organics in nanofiltration concentrate from biologically pretreated landfill leachate by ultraviolet (UV)-Fenton method at room temperature and atmospheric pressure. Both lab-scale experiments and pilot-scale studies were conducted to explore its effectiveness. Experimental results showed that the degradation efficiency of UV-Fenton method was superior to UV-H2O2 method and Fenton method. Effects of initial pH, initial temperature, Fe (II) dosage, H2O2 dosage and the dosing mode of H2O2 on the removal of organics were examined. The COD removal efficiency could reach 93% via the continuous dosing of H2O2 under the optimal conditions of initial pH 3, initial temperature 25 ℃, reaction time 3 h, FeSO4·7H2O dosage 7.2 mmol/L and H2O2 dosage 400 mmol/L. The effluent COD concentration was reduced to less than 100 mg/L, which meets the Chinese national discharge standard of typical landfill leachate. Results from pilot-scale studies indicated that UV-Fenton method could provide an efficient treatment of the leachate nanofiltration concentrate with varying COD content. Biodegradability analysis, fluorescence excitation-emission-matrix combined with parallel factor analysis, and gas chromatography-mass spectrometer analysis of the treated water further verified the effectiveness of UV-Fenton method in removing recalcitrant organic pollutants and improving the biochemical properties of the leachate nanofiltration concentrate.

Investigation of Heavy Metal (Lead) Removal from Aqueous Solution by Using Advanced Oxidation Process (Fenton)

Background and Aim: Undoubtedly, controlling the maximum entry of heavy metals into the food is one of the measures which should be taken into account in order to maintain the food consumers' health and achieve the food safety. The sensitivity and importance of this issue are doubled due to the irreparable, acute and chronic complications of heavy metals which are classified according to the effects on the nervous system until the carcinogenesis in the human body. On the other hand, this issue is significantly important since these metals differently enter to crops such as tea, water, and rice and generally the food and beverage that are widely consumed. Therefore, the aim of this study is to remove heavy lead metal from aqueous solution by Fenton method. This study is an experimental study. The samples are synthesized in a collection of laboratories at the Faculty of Health, and the pH parameters, contact time and lead elimination rate and the optimal Fenton ratio are investigated. Results are analyzed using SPSS software and Charts are plotted by excel. The results showed that the best pH for removal of lead 5 and its best concentration is 30 mg/ L, and the optimal Fenton ratio is 1 to 5, as well as the best contact time for removal of lead from aqueous media for 10 minutes. The present study showed that the pH factor, contact time, Fenton concentration and lead in all four were effective in removing lead from aquatic solution.

Enhancing CaO2 fenton-like process by Fe(II)-oxalic acid complexation for organic wastewater treatment

Hydrogen peroxide (H2O2) is used widely as Fenton's reagent for organic wastewater treatment. However, the application range of the optimum Fenton reaction is narrow, needing to adjust pH before and after treatment. Besides, the disproportionation of H2O2 and generated iron precipitation also confine the normal operation of Fenton method. To overcome the drawbacks of the traditional Fenton process, a Fe(II) catalyzed calcium peroxide (CaO2) Fenton-like process assisted by oxalic acid (OA) for aqueous organic pollutants degradation was proposed (Fe2+/OA/CaO2). The methyl orange (MO) as a typical organic pollutant, its removal performances by this Fe2+/OA/CaO2 system were evaluated. In the optimized conditions, 99% of MO was degraded within 15 min, and 38% mineralized after 180 min when the molar ratio of Fe2+: OA: CaO2 was 1: 2: 2 (Fe2+ = 1.5 mM). Radicals detection indicated that hydroxyl radical (HO•) was the main reactive species for the MO elimination. Furthermore, density functional theory calculation was in good agreement with the experimental results, which proved that the Fe2+/OA/CaO2 could improve the circulation between Fe2+ and Fe3+, promoting the oxygen reactive species generation and pollutant removal. The main intermediates were identified and the degradation pathways were proposed based on the results of the mass spectrum analysis, and the attack of HO• was suggested as the main function for the MO decomposition. The matrix effects of water constituents on the performance of Fe2+/OA/CaO2 were investigated, and the results showed that a certain amount of Cl−, NO3−, HCO3−, and HA affected the elimination than SO42−. Finally, the attempt of actual wastewater disposal indicated the synergistic system possessed good potential for future practical application.

Textile wastewater discoloration by Fenton oxidation process

Treating industrial wastewater by advanced oxidation processes, is a recent interest primarily for decolorization of aqueous solutions containing dyes. The application of the Fenton reaction is one of these processes, bleaching liquid discharges after a textile dyeing unit in the city of Marrakech, Morocco, which are non-biodegradable, using oxidation by Fenton's reagent has shown its ability to degrade the dyes in water to carbon dioxide, water, and other harmless products. In this study a serie of pure dyes mineralization experiments used in the dyeing process, such as: the Bezaktiv BLUE-SR, the NOVACRON® Red FN-R, and the NOVACRON®SCALE TFN-6G, and a global liquid discharge containing dyes and chemical additives. Fenton's method is effective at pH = 3, as a result, we had a total discoloration for the three pure colors, and up to 47% to the overall rejection for 60 minutes at room temperature, and 100% when the temperature was increased to 60 °C. The presence of chemical additives disadvantage Fenton oxidation.

SCREENING OF Andrographis Paniculata EXTRACT FOR ANTIOXIDANT AND GENOTOXIC ACTIVITIES

Andrographis paniculata is an important medicinal plant which has been used to treat various ailments. The present study was undertaken to analyze the phytochemical compounds and evaluated the antioxidant and genotoxic potential of Andrographis paniculata leaves and whole plant extracts. Phytochemical compounds analyzed by qualitative and quantitative analysis of methanol extracts of the leaves and whole plant extracts which showed the presence of Alkaloids, Carbohydrate, Resins, Saponins, Flavonoid, Steroids, Glycosides and Tannin. Quantitative analysis were also conducted to determine the amount of Alkaloids, Flavonoids, Saponins and Tannin by HPTLC Finger printing methods in A. paniculata ( A.P.) leaves and whole plant .The Antioxidant activity of A. paniculata Methanolic extract was evaluated by Fenton methods which showed the dose dependent Inhibition of TBARS formation. The Genotoxicity was evaluated by Micronucleus Assay. The dose dependent prevention of bone marrow micronucleus formation by Andrographis paniculata leaves and whole plant extracts was observed. Therefore, Andrographis paniculata leaves and whole plant extract caused antioxidant and genotoxic potential.

Experiment on pretreatment of waste water from bamboo heat treatment by combination of iron-carbon micro-electrolysis and Fenton method

Abstract The chemical oxygen demand (COD) of waste water from bamboo heat treatment is mainly organic macromolecule compound which degraded from hemicellulos, lignin and extractives. COD is toxic to aquatic organism and human body and very difficult to degrade. The paper studied the possibility of pre-treating the bamboo heat treated waste water (BHTWW) by combination of iron-carbon micro electrolysis and Fenton method. Orthogonal experiment was designed with 3 factors: the initial pH value, retention time and H2O2 dosage, and carried out with a dynamic sampling device with 2:1 iron carbon ratio. Results showed that the iron-carbon micro electrolysis and Fenton were proved to be a potential method in pre-treating BHTWW, and the optimum parameter should be pH 3.0, 40 min residence time and 0.5 % H2O2. After pre-treating, the removal rate of COD was 60.29 %, and B/C (biochemical oxygen demand after 5 days (BOD5)/COD increased from 0.037 to 0.32, the biodegradability was significantly improved. During the pretreatment, the nutrients in BHTWW had been oxidized, the double bound, conjugated double bond in guaiac lignin were opened or broken and degraded into more small molecular, nutrients such as TOC (total organic carbon) content, total nitrogen and total sugar content all decreased which all contributed for the increase of B/C. The microstructure of activated carbon appeared broken and collapses after pretreatment which indicated that they were eroded or involved during the micro electrolysis reaction.

Rectorite-supported nano-Fe3O4 composite materials as catalyst for P-chlorophenol degradation: Preparation, characterization, and mechanism

Clay minerals, as abundant natural resources, are among the most suitable supporting materials for nano metal. In this manuscript, new Fe3O4 nanoparticle/rectorite (Fe3O4/rectorite) catalysts are developed via in-situ precipitation oxidation reaction. Various physicochemical characterizations of Fe3O4/rectorite show that Fe3O4 nanoparticles (nano-Fe3O4) with an average particle diameter of approximately 10–20 nm are effectively loaded on the surface of acid leached rectorite (Al-rectorite) and have low coaggregation and improved dispersion. Moreover, the catalytic activity of Fe3O4/rectorite on degradation of P-chlorophenol by heterogeneous Fenton method is studied. Results of degradation experiments show that Fe3O4/rectorite has higher degradation efficiency of P-chlorophenol than bare nano-Fe3O4. Regeneration studies also show that Fe3O4/rectorite maintains 100% of its maximum P-chlorophenol degradation capacity after seven consecutive cycles. Fe3O4/rectorite can be easily separated by magnetic separation, and thus has good stability and reusability. The degradation mechanism of Fe3O4/rectorite is adsorption coupled with a Fenton-like reaction, which accounts for P-chlorophenol degradation of up to 625 mg/g. This work demonstrates a new composite material for the effective remediation of refractory organic compounds from wastewater.

Study on the treatment of organic wastewater from soil thermal desorption by Fenton method

Fenton’s reagent has been widely used as a high-grade oxidation technology in the treatment of refractory, high-concentration, toxic and harmful organic wastewater, and has achieved remarkable results. The organic wastewater generated by thermal desorption of soil has the characteristics of high pollutant content, complex composition and large fluctuation of water quality. Generally, the organic wastewater components produced by thermal desorption of soil mainly include polycyclic aromatic hydrocarbons, polychlorinated biphenyls, chlorobenzene and the like.

Leachate Treatment of TPA Talang Gulo, Jambi City by Fenton method and adsorption

ABSTRAK Lindi adalah cairan yang ditimbulkan oleh sampah akibat masuknya air eksternal yang dapat melarutkan materi-materi terlarut, termasuk materi-materi organik hasil dekomposisi secara biologi. Lindi dari sebuah landfill (TPA) mengandung zat organik dan anorganik dalam konsentrasi yang tinggi. Dengan adanya gaya gravitasi maka lindi yang terbentuk akan bergerak ke dasar landfill (TPA) akan masuk ke dalam tanah dengan membawa bahan cemaran baik material tersuspensi maupun material terlarut yang dapat mencemari air tanah. Salah satu proses pengolahan lindi adalah dengan menggunakan reagen Fenton dan adsorpsi yang termasuk dalam teknologi Advanced Oxidation Processes (AOPs). AOPs didasarkan pada pembentukan spesies yang sangat reaktif seperti radikal hidroksil (OH•) yang efektif untuk menurunkan COD, BOD dan TSS. Penelitian ini bertujuan untuk mengolah lindi menggunakan reagen Fenton dan adsorpsi serta mempelajari rasio molar Reagen Fenton dan waktu pengadukan terhadap penurunan COD, BOD dan TSS. Pada penelitian ini lindi diolah selama 30-120 menit. Kondisi optimum dicapai pada rasio molar 1:200, waktu pengadukan 120 menit, dan adsorpsi menggunakan karbon aktif selama 120 menit dimana penurunan COD, BOD dan TSS maksimum yang dicapai berturut-turut 95%, 95% dan 92% dengan nilai konsentrasi akhir 96 mg/L, 25,5 mg/L% dan 90 mg/L. Kata Kunci: Lindi, Reagen Fenton, AOPs, COD, BOD, TSS ABSTRACT Leachate is a liquid generated by waste due to the entry of external water that can dissolve dissolved materials, including decomposition of organic matter biologically. Leachate from a landfill (TPA) contains organic and inorganic substances in high concentrations. by gravitational force, the leachate formed will move to the bottom of the landfill (TPA) and will enter the soil by carrying contaminated material, both suspended material and dissolved material that can pollute ground water. One of the leachate treatment processes is using Fenton reagent and adsorption. Fenton method included in Advanced Oxidation Processes (AOPs) technology. AOPs are based on the formation of highly reactive species such as hydroxyl radicals (OH•) which are effective for reducing COD and BOD. This study aims to treat leachate by using Fenton reagent and adsorption. The effect of reagent Fenton molar ratio and stirring time on degradation of COD, BOD and TSS were also investigated. In this study leachate was processed for 30-120 minutes. the optimum conditions were achieved at a molar ratio of 1: 200, stirring time of 120 minutes, and adsorption using 120 minutes of activated carbon where the maximum decrease in COD, BOD and TSS achieved was 95%, 95% and 92% with a final concentration of 96 mg/L, 25.5 mg/ L and 90 mg/ L. Keywords : Leachate, Fenton Reagent, AOPs, COD, BOD, TSS

Degradation process and kinetics study of actual urotropine wastewater by Fenton method

Degradation process and kinetics study of actual urotropine wastewater by Fenton method

Water Reuse: Emerging Contaminants Elimination—Progress and Trends

This work concentrates on the review paper published by Ahmed et al. [1] which is dedicated to the elimination of emerging contaminants (ECs) using biological, chemical and hybrid techniques in effluents from wastewater treatment plants (WWTPs). Endocrine disruption chemicals (EDCs) are better reduced by a membrane bioreactor (MBR), activated sludge, and aeration processes between various biological processes. Surfactants, EDCs and personal care products (PCPs) may be well reduced using activated sludge processes. Pesticides and pharmaceuticals manifested convenient reduction performances by biological activated carbon. Microalgae treatment techniques may diminish nearly all sorts of ECs to a certain degree. Additional biological methods were observed less efficient in dealing with ECs. Chemical oxidation techniques (like ozonation/H2O2, UV photolysis/H2O2, and photo-Fenton) may greatly eliminate up to 100% of pesticides, beta-blockers, and pharmaceuticals; at the same time, EDCs may be better reduced via ozonation and UV photocatalysis. Fenton method was observed less efficient in treating any sorts of ECs. A merged setup founded on ozonation pursued by biological activated carbon was manifested hugely efficacious in eliminating pesticides, beta-blockers, and pharmaceuticals. An integrated ozonation-ultrasound device may eliminate until 100% of numerous pharmaceuticals. Next research orientations to boost the elimination of ECs have been suggested.

Performance Evaluation of Fenton Oxidation Treatment Method for the Reuse of Reactive Dyeing Effluent

In this study, a novel wash-off method was investigated wherein the use of Fenton’s reagent was evaluated to get rid of hydrolyzed and unfixed reactive dyes from wash-off liquor and reused in next wash-off process. After dark shade dyeing (5% o.w.f) with C.I. Reactive Blue 72, C.I. Reactive Blue 221, C.I. Reactive Red 141, C.I. Reactive Red 198, C.I. Reactive Orange 84, C.I. Reactive Orange 122, C.I. Reactive Yellow 105 and C.I. Reactive Yellow 138 , fabrics were subjected to both clean water (reference) and treated wash-off liquors (batch) and comparisons were made. Fenton reagent was proved capable to achieve 88-97% color reduction in wash-off liquor at pH 3 by using optimal dose of FeSO4 and H2O2 at room temperature. Then effectiveness of Fenton’s reagent treated wash-off was evaluated in terms of color difference values (ΔL*, ΔC*, Δh* and ΔE*), wash fastness and crocking properties. For color fastness properties the commercially tolerable value of ΔE*≤1 was observed for blue and red dyes and slightly higher value for yellow and orange dyes. Wash fastness and crocking results are almost similar for reference and batch dyed fabrics and their values ranges 4-5 on grey scale. Color strength (K/S) showed negligible difference in values indicating that fabrics absorbed almost same amount of dyestuff for each dye .Fenton method of treatment proved to be an eco-friendly and economically feasible treatment method and treated liquor can be effectively used in next dyeing, without compromising quality parameters.

Biodegradability enhancement of real antibiotic metronidazole wastewater by a modified electrochemical Fenton

This paper proposes a modified electrochemical Fenton method with a pair of iron electrodes, which Fe anode is electrodisolved supplying stoichiometric Fe2+. Then the electrodisolved Fe2+ reacts with H2O2 to generate hydroxyl radical (· OH). The experiment shows that 62.6% of chemical oxygen demand (COD) is removed and the ratio of the five-day biochemical oxygen demand (BOD5) to COD increases from 0.17 to 0.45 under the optimal experimental conditions (current density of 30 mA/cm2, electrolysis time of 15 min, H2O2 dosage of 75 mmol/L, pH 3.00 and stirring time of 2.5 hours). Meanwhile, the high concentration of metronidazole (1000 mg/L) is dramatically decreased (> 95%). In order to explore the mineralization pathway for metronidazole, the intermediate by-products of the modified electrochemical Fenton process are investigated by GC/MS, FTIR and HPLC. Good results are achieved in treatment of the real metronidazole wastewater by the proposed method, BOD5/COD increases from 0.17 to 0.35. This method has been successfully applied to a large scale industrial treatment of real metronidazole wastewater as a pretreatment process for the biochemical treatment.