Fenton Treatment Research Articles

Integration of advanced oxidation processes and activated sludge for the treatment of high refractory industrial wastewater

AbstractBACKGROUNDThe aim of this research was centered on the development of a suitable strategy for the treatment of a wastewater from the production of automotive coating pipes.RESULTSCoagulation and Fenton treatments were ineffective and did not achieve the desired objectives, however, ozone based processes were shown to be an interesting technology. Several parameters affecting ozonation, such as pH, the addition of hydrogen peroxide as co‐oxidant and the contact time, were optimized. It was concluded that the best efficiency was attained with ozone (2 g h−1) using a multi‐stage pH procedure. After 1200 min reaction, this system achieved 98% chemical oxygen demand (COD) removal and the final effluent presented a BOD5/COD improvement from 0.11 to 0.30.CONCLUSIONThis study proposes an effective method to treat this specific wastewater. Fenton oxidation enabled an increase in effluent biodegradability, however, not sufficient to enable a posterior biological treatment. Using ozonation, the operating conditions can be adapted to provide an effluent able to be discharged into the hydro resources (COD < 150 mgO2 L−1), or to be sent to the municipal sewage plant (COD < 1000 mgO2 L−1) where it will be further refined in a biological system. © 2015 Society of Chemical Industry

AuPd/Fe3O4-based three-dimensional electrochemical system for efficiently catalytic degradation of 1-butyl-3-methylimidazolium hexafluorophosphate

Ionic liquids (ILs) have been reported to be toxic and harmful to aquatic and terrestrial organisms, thus it is imperative to remove the residual ILs in various effluents. In this work, a three-dimensional (3D) electrocatalytic system with synthesized AuPd/Fe3O4 nanoparticles (NPs) as particle electrodes (PEs) was established for the degradation of typical 1-butyl-3-methylimidazolium ([BMIM]) based ILs. The as-synthesized AuPd/Fe3O4 possessed preferable electrochemical properties for in situ supplement of H2O2 and renewable Fe species. This 3D electrocatalytic system exhibited excellent performance with 100% removal rate of BMIM in 90min under 120mA, pH 3, and 1g/L dosage of AuPd/Fe3O4 NPs. Kinetics study revealed that the degradation rule of BMIM well followed the anodic Fenton treatment (AFT) model, in which the variation of the degradation rate was positively correlated with that of dissolved Fe2+, while significantly differed from the evolution of H2O2. Particularly, the appearance of the H2O2 inflection point suggested the optimal effectiveness of AuPd/Fe3O4-based 3D electrocatalysis. During this electrocatalytic process, the active HO was produced over the AuPd/Fe3O4 PEs, thereby initiated the highly efficient degradation of BMIM into 1-butyl-3-methyl-2,4,5-trioxoimidazolidine, 1-butyl-3-methylurea and N-butyl-formamide as main intermediates. The electrocatalytic stability of the AuPd/Fe3O4 PEs over seven times further indicated the potential applicability for organic wastewater treatment.

Study on treating old landfill leachate by Ultrasound–Fenton oxidation combined with MAP chemical precipitation

In this study, the “Ultrasound/Fenton oxidation – MAP chemical precipitation” method was used to remove chemical oxygen demand (COD) and ammonia nitrogen from the old landfill leachate which was collected from one sanitary landfill in Wuhan. Firstly, Ultrasound treatment and Fenton oxidation treatment were separately used to treat the old landfill leachate, and under their optimum reaction conditions, the COD concentration was degraded from 842 to 697 mg L−1 and from 842 to 133 mg L−1, respectively. Then, Ultrasound/Fenton oxidation treatment was used to treat the same old landfill leachate. Compared with the single Fenton treatment, Ultrasound/Fenton oxidation treatment could raise the COD removal efficiency from 84.05 to 90.88% with the same H2O2 consumption. After the Ultrasound/Fenton oxidation treatment, Na2HPO4·12H2O and MgSO4·7H2O were used as precipitation reagents to remove ammonia nitrogen from the old landfill leachate, and the ammonia nitrogen concentration degraded from 910 to 11 mg L−1. The experiment results indicated that “Ultrasound/Fenton oxidation – MAP chemical precipitation” method was an effective and economic method to treat old landfill leachate.

Experimental Design of Fenton Process for the Oxidation and Mineralization of Monocrotophos

In this study, the Fenton treatment of Monocrotophos (MCP) was evaluated in terms of oxidation and mineralization efficiency using response surface methodology (RSM). The effects of MCP, Fe2+, H2O2 concentrations and reaction time, and the interactions between these factors on (i) the oxidation efficiency of MCP and (ii) the mineralization of MCP were studied. Hence, the objective of this study was to optimize MCP oxidation and mineralization by the Fenton process (FP) using RSM. The obtained optimum conditions for MCP oxidation and mineralization using FP were 0.022:0.03:0.15 MCP/Fe2+/H2O2 and a reaction time of 65 min. MCP was mineralized easily through the Fenton reaction. The MCP oxidation efficiency was 90% and the mineralization efficiency was 66%. The initial MCP concentration was the most significant variable affecting both the oxidation and mineralization efficiency of MCP. Addition of Fe2+ had a more significant effect on the MCP oxidation compared to the MCP mineralization.

Effect of the ultrasound-Fenton oxidation process with the addition of a chelating agent on the removal of petroleum-based contaminants from soil.

The effects of ultrasonic irradiation, the chelating agent modified Fenton reaction, and a combination of ultrasound and the Fenton method in removing petroleum contaminants from a soil were studied. The results showed that the contaminant removal rate of the Fenton treatment combined with an oxalic acid chelating agent was 55.6 % higher than that without a chelating agent. The average removal rate of the contaminants using the ultrasound–Fenton treatment was 59.0 % higher than that without ultrasonic treatment. A combination of ultrasound and an Fe2+/Fe3+-oxalate complex–modified Fenton reagent resulted in significantly higher removal rates of n-alkanes (CnH2n+2, n < 28), isoprenoid hydrocarbons, aromatic hydrocarbons, and saturated polycyclic terpenes compared with the ultrasound treatment alone or the Fenton method. The Fenton reaction and the ultrasound–Fenton treatment can unselectively remove multiple components of residual hydrocarbons and a number of benzene rings in polycyclic aromatic hydrocarbons. The chemistry of the heterocyclic compounds and the position and number of substituents can affect the degradation process.

Chlorpyrifos: pollution and remediation

The widespread use of pesticides in modern agriculture is of increasing concern due to environmental contamination and subsequent biodiversity loss. Chlorpyrifos is a toxic organophosphate pesticide. Repeated applications of chlorpyrifos modify the soil microbial community structure and pose potential health risks to the other nontargets. Chlorpyrifos has been reported as the second most commonly detected pesticide in food and water. Extensive use of chlorpyrifos in agriculture and persistence in the environment have raised public concern and demand for safe technologies to overcome the pollution and toxicity problems. Here, we review pollution and toxicity issues associated with chlorpyrifos use and discuss strategies to solve pesticide contamination. Chlorpyrifos, previously shown to be resistant to enhanced degradation, has now been proved to undergo enhanced microbe-mediated decay. Here, special emphasis is given to degradation methods such as ozonation, Fenton treatment, photodegradation, and advanced oxidation processes along with microbial degradation. Finally, we focus on degradation process at enzyme and molecular levels which will enable us to elucidate the exact degradative pathway involved in biodegradation.

Product distribution and sulfur behavior in sewage sludge pyrolysis: Synergistic effect of Fenton peroxidation and CaO conditioning

Iron- and calcium-based compounds play an important role in the devolatilization stage of solid fuels thermal disposal. This study aims to investigate the synergistic effects of Fenton’s reagent (Fe2+/H2O2) and conditioner CaO on product distribution and sulfur transformation in this process. Four samples were pyrolyzed by using a special drop-tube/fixed-bed furnace at 873–1273K with a high heating rate. Specific compositions of solid residue, tar and gas were also identified to further clarify the related mechanisms. According to the results, after Fenton peroxidation, both side chain and main chain of organic compounds were prone to crack, forming more gas and less tar with similar composition. When the oxidized sludge was further treated by CaO, altered carbon species evolution left additional COH, CO, C(O, N), OCO in char. Moreover, synergy between the two conditioners was likely to provide Fe2O3, CaO and H2O, further increasing the H2-rich gas yields. Besides, the observation also demonstrates that Fenton treatment favored the char-S production not only through catalyzing the cyclization reactions but also from producing relatively stable sulfonic acid-S/sulfone-S. When temperature increased, the peroxidation hindered H2S, CS2 and CH3SH releasing, while the decomposition of FeSO4 and Fe2(SO4)3 aggravated SO2 polluting. However, it is exciting that sulfur fixation rate eventually reached over 97.0%, since the residual Fe- and Ca-containing compounds cooperatively captured liberated sulfur. Thus reusing conditioners, which originally targeted for improving sludge dewaterability, is a promising strategy for achieving efficient thermal conversion of sewage sludge with low sulfur pollution.

Hazardous waste landfill leachate treatment by combined chemical and biological techniques

The efficacies of coagulation, ozonation, Fenton treatment, activated sludge process, Fenton treatment–activated sludge process (CHEM-BIO) and activated sludge process–Fenton treatment (BIO-CHEM) to treat hazardous waste landfill leachate were investigated and compared. The results of the biodegradability test revealed a high content of readily biodegradable organic matter in semicoke landfill leachate, and thus, aerobic biological oxidation was found to be a more reasonable and cost-effective technique for leachate treatment than direct chemical processes (ozonation, Fenton treatment). However, in terms of treatment efficacy, both chemical and biological processes resulted in a high residual organic load, indicating an insufficient leachate quality improvement. The treatment performance of the combined schemes (BIO-CHEM and CHEM-BIO) proved more effective and ensured the removal efficacy percentage met that required by EU legislation as well as the specific target discharge limits of the measured parameters. Accounting for the treatment cost-effectiveness, BIO-CHEM proved to be a more feasible option and could be suggested as the most efficient and practicable technological scheme for hazardous waste landfill leachate treatment.

Niobium substituted magnetite as a strong heterogeneous Fenton catalyst for wastewater treatment

In this study, a series of Nb substituted magnetites; Fe3−xNbxO4 (x=0.0, 0.022, 0.049, 0.099, and 0.19) were prepared and characterized by XRD, BET surface area, TEM, VSM, XPS, and chemical experiments. The magnetite inverse spinel structure and magnetic property were maintained in all the synthetized samples. A significant decrease in crystal size (≈two times) and increase in specific surface area (≈three times) were observed with increased Nb content, resulting in higher adsorption capacity of the samples. In addition, the reactivity of the synthetized samples was examined through degradation of methylene blue solution using Fenton-like reaction. It was found that the incorporation of niobium significantly improved the degradation of methylene blue of which total MB removal was achieved within 180min at higher molar ratios of Nb (x=0.19). This could be attributed to the generated oxygen vacancies on the surface of catalysts, the contribution of the introduced Nb cations in Fenton oxidation cycle for regeneration of Fe2+ cations, and increase in adsorption capacity of the samples due to larger surface area. The MB degradation through Fe2.79Nb0.19O4/H2O2 system was well described by the pseudo-first-order equation in kinetics. All samples showed good stability under the studied pH conditions. The amount of niobium leached was not detectable in neutral and basic solutions and the samples could be reused in oxidation process for several times without a significant decrease in their catalytic efficiency. The results proved that incorporation of niobium into magnetite significantly improved the characteristics and effectiveness of the heterogeneous catalyst for Fenton treatment of recalcitrant effluents.

Evaluation of Mutagenic and Genotoxic Activity in Vinasses Subjected to Different Treatments

The mutagenic and genotoxic activity of vinasses collected from a fuel alcohol plant, located in the municipality of Frontino, Northwestern Colombia, were evaluated. Two samples obtained from an 82-L capacity hybrid reactor (UASB-anaerobic filter (AF)-UASB) were studied under laboratory conditions after being treated with biological oxidation, the first, and the second with Fenton reaction consecutively. Mutagenicity was evaluated in vitro by the Ames test using strains TA98 and TA100 with and without S9 metabolic activation. The genotoxic analysis was conducted using the Allium cepa roots assay where chromosomal aberrations were used as clastogenic or aneugenic response markers, and micronuclei as mutagenic response. The Ames test results showed a strain-dependent positive linear association with the vinasse sample concentration before treatment (dose–response effect). Unlike TA100, strain TA98 showed a mutagenic effect in both the presence and absence of metabolic enzymes. After the biological oxidation treatment, vinasse mutagenicity significantly decreased. Finally, after Fenton treatment, the sample did not induce any mutagenic event. Genotoxic activity was observed in all three samples, but there was a higher frequency in the vinasse sample before treatment. Concerning the frequency of micronuclei, no clear association was observed with either the concentration or the type of sample.

Mineralization of bisphenol A by photo-Fenton-like process using a waste iron oxide catalyst in a three-phase fluidized bed reactor

A waste iron oxide (labelled as BT4), which was a by-product of the fluidized-bed Fenton treatment of the bio-treated tannery wastewater, was utilized as the catalyst for the mineralization of bisphenol A (BPA) by a heterogeneous photo-Fenton process in a three-phase fluidized bed reactor. The main constituent of BT4 was identified as α-FeOOH, while BT4 exhibited higher catalytic activity than pure α-FeOOH. The effects of catalyst loading, H2O2 concentration and initial pH on the mineralization of BPA were elucidated. With 2 g/L catalyst loading, 0.74 mmol/L H2O2 and initial pH 3, 90% TOC of 0.05 mmol/L BPA was removed after 180 min reaction. The result of the catalyst reuse experiment indicated that BT4 showed a good stability.

Application of the Ulva pertusa bioassay for a toxicity identification evaluation and reduction of effluent from a wastewater treatment plant

A toxicity identification evaluation (TIE) based on Ulva pertusa spore release was conducted in 3 phases for the identification of the major toxicants in effluent from a wastewater treatment plant (WTP) and the receiving water in an adjacent stream. The toxicity of the final effluent (FE), as compared with raw wastewater, and primary and secondary effluent, showed a greater change over 12-monthly sampling events and appeared to have impacts on the toxicity of the downstream water with a significant correlation (r2 = 0.89, p < 0.01). In Phase I, toxicity characterization indicated that cations were likely to be the responsible toxicants for the FE. In Phase II, cations such as Cu, Ni, and Zn were found in the FE at higher concentrations than the EC50 concentrations determined for the standard corresponding metals. When the concentrations of each metal in the FE samples were plotted against the respective toxicity units, only zinc showed a statistically significant correlation with toxicity (r2 = 0.86, p < 0.01). In Phase III, using spiking and mass balance approaches, it was confirmed that Zn was the major toxicant in the effluent from the WTP. Following a change in the Fenton reagent used, to one with a lower Zn content, the toxicity of the FE greatly decreased in subsequent months. The TIE developed here enabled the toxicity of FEs of the WTP to be tracked and for Zn, originating from a reagent used for Fenton treatment, to be successfully identified as the key toxicant. The TIE method based on U. pertusa demonstrated utility as a low cost and simple tool to identify the risk factors for industrial effluents and provided information on regulatory control and management.

A rapid Fenton treatment technique for sewage sludge dewatering

The study aimed to develop a rapid and practical Fenton treatment technique for sludge dewatering. The results indicated that the Fenton reaction time could be shortened to 5min under suitable conditions. In addition, an orthogonal experimental design method was used to optimize the rapid Fenton treatment process. The optimal conditions were as followings, pH 3, Fe2+ of 50mg/gDS (dry solids), H2O2 of 30mg/gDS and lime of 50mg/gDS, at which the specific resistance to filtration (SRF) reduction efficiency of 96% was achieved. The dosage of Fe2+ was demonstrated to be the most significant factor affecting sludge dewaterability. Furthermore, the lowest extracellular polymeric substances (EPS) concentration in the sludge supernatant was measured under the optimal conditions, suggesting that Fenton’s reagent acted both as an oxidant and as an effective coagulant for the sludge fragments. The morphology of the sludge cake exhibited a relatively regular and spongy block-like structure, which could maintain high permeability during high-pressure filtration. With the novel filter press achieved the squeezing pressure up to 40MPa, the water content of sludge cake could be reduced to 55.1±0.6%. Additionally, the economic assessment shows that the rapid Fenton treatment combined with high-pressure filtration can be a suitable technique for sewage sludge dewatering.

Biomimetic Fenton-catalyzed lignin depolymerization to high-value aromatics and dicarboxylic acids.

By mimicking natural lignin degradation systems, the Fenton catalyst (Fe(3+), H2O2) can effectively facilitate lignin depolymerization in supercritical ethanol (7 MPa, 250 °C) to give organic oils that consist of mono- and oligomeric aromatics, phenols, dicarboxylic acids, and their derivatives in yields up to (66.0±8.5) %. The thermal properties, functional groups, and surface chemistry of lignin before and after Fenton treatment were examined by thermogravimetric analysis, pyrolysis-gas chromatography-mass spectrometry, (31)P NMR spectroscopy, and X-ray photoelectron spectroscopy. The results suggest that the Fenton catalyst facilitates lignin depolymerization through cleavage of β-ether bonds between lignin residues. The formation of a lignin-iron chelating complex effectively depresses lignin recondensation; thus minimizing charcoal formation and enhancing the yield of liquid products.

Insights into the respective role of acidification and oxidation for enhancing anaerobic digested sludge dewatering performance with Fenton process

Digested sludges generally exhibit poorer dewaterability than activated sludges. This study investigated the effects of acidification and oxidation on EPS properties and dewaterability of anaerobic digested sludge in Fenton treatment in order to unravel the underlying mechanism of sludge conditioning. The results indicated that sludge dewatering property was improved after acidification treatment. Meanwhile, fluorescence analysis revealed that the protein-like substances were effectively removed from sludge bulk after acidification treatment. Acidification and Fenton oxidation showed a significant synergetic effect in enhancing sludge dewatering process. Solubilization and decomposition of bound EPS occurred synchronously during Fenton conditioning. Oxidation process is very likely to play a more important role in sludge conditioning than Fenton coagulation. According to pilot test, Fenton treatment performed much better in cake moisture content reduction than chemical conditioning with traditional inorganic coagulants. Additionally, full-scale application of Fenton conditioning will not have detrimental effects on performance of wastewater treatment system.

Combination of ultrasound and Fenton treatment for improving the hydrolysis and acidification of waste activated sludge

US/Fenton had a synergetic effect on improving the hydrolysis and subsequent acidification of WAS.

Organic additives enhance Fenton treatment of nitrobenzene at near-neutral pH.

Nitrobenzene (NB) is considered a toxic and potential carcinogen. Continuous contamination has resulted in an urgent need for remediation. Fenton reagent provides an advanced oxidation process that is capable of remediating recalcitrant nitroaromatic compounds, such as NB. However, one drawback of Fenton chemistry is that the reaction requires acidic pH to prevent precipitation of iron. Our studies have investigated Fenton conversion of NB at near-neutral pH with several organic additives: β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HPCD), carboxymethyl-β-cyclodextrin (CMCD), and polyethylene glycol (molecular weight (MW) = 200, 400, and 600) for developing a process for treating NB-contaminated waters. The main factors influencing NB conversion, such as iron concentration, hydroxyl radicals (·OH) scavengers, and kinds or concentration of organic additives, were examined. Meanwhile, the reactive mechanisms and kinetics were investigated for Fenton conversion of NB. The results show that organic additives for Fenton process should be a good alternative for the advanced treatment of NB at near-neutral pH.

Synthesis and characterization of modified activated sludge for biological oxidation with isolation studies and performance evaluation

The present work reports the preparation of modified activated sludge (MAS) with isolation studies and performance evaluation for the removal of aromatic pollutants. On the basis of biochemical and physiological characteristics study, about 389 bacterial isolates (combination of gram-negative and gram-positive) were identified in the sludge. Performance evaluation studies for treatment of wastewater containing aromatic pollutants using modified activated sludge revealed that a maximum of 67% reduction in the pollutant loading was obtained for only biological process which significantly increased to 98% for the combined process of Fenton treatment and biological oxidation. Improved biodegradability was also observed with BOD5/COD value of about 0.30–0.35 with pretreatment time of 40min for effluent containing benzene, toluene, naphthalene and xylene and 60min for effluent containing ethylbenzene and p-nitrophenol. Comparison of the performance of MAS with the more commonly used prepared activated sludge and the activated sludge process revealed superior degradation effectiveness and growth characteristics. Kinetic studies also revealed that maximum substrate reduction with enhanced microbial growth of bacterial strain was obtained for MAS. Overall the present work has clearly highlighted the novelty of using a modified activated sludge based on the mixed culture of microorganisms and the better efficacy of the combined treatment scheme based on Fenton’s oxidation and biological oxidation using MAS.

Application of non-thermal plasma reactor and Fenton reaction for degradation of ibuprofen

Pharmaceutical compounds have been detected frequently in surface and ground water. Advanced Oxidation Processes (AOPs) were reported as very efficient for removal of various organic compounds. Nevertheless, due to incomplete degradation, toxic intermediates can induce more severe effects than the parent compound. Therefore, toxicity studies are necessary for the evaluation of possible uses of AOPs.In this study the effectiveness and capacity for environmental application of three different AOPs were estimated. They were applied and evaluated for removal of ibuprofen from water solutions. Therefore, two treatments were performed in a non-thermal plasma reactor with dielectric barrier discharge with and without a homogenous catalyst (Fe2+). The third treatment was the Fenton reaction.The degradation rate of ibuprofen was measured by HPLC-DAD and the main degradation products were identified using LC–MS TOF. Twelve degradation products were identified, and there were differences according to the various treatments applied. Toxicity effects were determined with two bioassays: Vibrio fischeri and Artemia salina. The efficiency of AOPs was demonstrated for all treatments, where after 15min degradation percentage was over 80% accompanied by opening of the aromatic ring. In the treatment with homogenous catalyst degradation reached 99%. V. fischeri toxicity test has shown greater sensitivity to ibuprofen solution after the Fenton treatment in comparison to A. salina.

Combined processes for wastewater purification: treatment of a typical landfill leachate with a combination of chemical and biological oxidation processes

BACKGROUND Among anthropogenic wastewaters, landfill leachate is known to contain numerous persistent organic pollutants, heavy metals, noxious microorganisms, etc., which makes the establishment of an efficient treatment procedure for leachate a matter of great importance. In this work, municipal waste landfill leachate was subjected to various types of chemical (CHEM) and biological (BIO) treatment with the final aim of establishing an optimal treatment scheme combining of individual physico-chemical and biological processes. RESULTS Three different treatment strategies (CHEM-BIO, BIO-CHEM and BIO-CHEM-BIO) were compared based on biodegradability and removal efficiencies achieved. Due to high initial biodegradability of raw leachate, the most efficient combined process was aerobic biological pre-treatment followed by Fenton treatment and subsequently biological post-treatment. The efficiency of combined treatment processes was investigated at laboratory scale, with over 90% COD and BOD7 removal. Finally, in order to evaluate the economic efficiency of the processes, consumption of Fenton's reagent was compared for CHEM-BIO and BIO-CHEM setups, with the latter achieving three times lower reagent consumption, at the same time providing similar treatment efficiency. CONCLUSIONS A readily-applicable efficient and economically feasible technological solution is provided for the treatment of typical municipal landfill leachate. © 2014 Society of Chemical Industry