Heterogeneous Fenton oxidation of Direct Black G in dye effluent using functional kaolin-supported nanoscale zero iron

This study investigated kaolin-supported nanoscale zero-valent iron (nZVI/K) as a heterogeneous Fenton-like catalyst for the adsorption and oxidation of an azo dye, Direct Black G (DBG). New findings suggest that kaolin as a support material not only reduced the aggregation of nanoscale zero-valent iron (nZVI) but also improved the adsorption of DBG. It consequently improved Fenton oxidation by increasing the local concentration of DBG in the vicinity of nZVI. This was confirmed by scanning electron microscopy and X-ray diffraction for the surface morphology of nZVI/K before and after the Fenton-like reaction. Furthermore, nZVI/K proved to be a catalyst for the heterogeneous Fenton-like oxidation of the DBG process in the neutral pH range. More than 87.22 % of DBG was degraded, and 54.60 % of total organic carbon was removed in the optimal conditions: 0.6 g/L dosage of nZVI/K, 33 mM H₂O₂, 100 mg/L initial DBG concentration, temperature of 303 K and pH of 7.06. Finally, it was demonstrated that nZVI/K removed DBG from dye wastewater through the processes of adsorption and oxidation.     

Environmentally friendly system for the degradation of multipesticide residues in aqueous media by the Fenton’s reaction

A Fenton oxidation system employing zero-valent iron (whose source was swarf, a residue of metallurgical industries, in powder form) and hydrogen peroxide for the treatment of an aqueous solution with six pesticides was developed, and the effect of the iron metal content, pH, and hydrogen peroxide concentration was evaluated. The characterization of the aqueous solution resulted in: pH 5.6, 105 mg L^?1 of dissolved organic carbon, and 44.6 NTU turbidity. In addition, the characterization of the swarf by FAAS and ICP-MS showed 98.43?±?7.40 % of zero-valent iron. The removal was strongly affected by the content of iron metal, pH, and hydrogen peroxide concentration. The best degradation conditions were 2.0 g swarf, pH 2.0, and 5 mmol L^?1 H₂O₂. At the end of the treatment, the pesticide degradation ranged from 60 to 100 %, leading to 55 % mineralization. Besides, all hydrogen peroxide was consumed and the determination of total dissolved iron resulted in 2 mg L^?1. Thus, the advantages of this system are rapid degradation (up to 20 min), high-degradation rates, simple handling, and low cost.

Long-Term Effects on Soil of the Disposal of Olive Mill Waste Waters (OMW)

Disposal of untreated olive mill waste waters (OMW) is a serious environmental problem in many Mediterranean countries. The aim of this work was to assess whether changes in soil properties have occurred due to direct disposal of raw OMW on soil and in evaporation ponds, and to investigate the potential fate and transport of pollutants after olive oil production had ceased. The results clearly showed that uncontrolled OMW disposal is a significant source of pollution to surface soil and waters. Disposal of OMW on soil greatly increased electrical conductivity (EC), available phosphorous (P), exchangeable potassium (K) and magnesium (Mg), organic matter, polyphenols, total and inorganic nitrogen (N), and available micronutrients mainly in surface soil layers. The presence of a high content of clay and carbonates in soil act as barriers and prevent downward transport of pollutants. Residual levels of total carbon (C), polyphenols, total and inorganic N, exchangeable K⁺, available P, iron (Fe), and copper (Cu) were also elevated even 8 years after mill closure. The long term disposal of OMW highlights the need to establish soil quality standards for soil parameters in order to identify soils affected by the disposal of OMW.     

Treatment of coking wastewater by an advanced Fenton oxidation process using iron powder and hydrogen peroxide

In this study the treatment of coking wastewater was investigated by an advanced Fenton oxidation process using iron powder and hydrogen peroxide. Particular attention was paid to the effect of initial pH, dosage of H₂O₂ and to improvement in biodegradation. The results showed that higher COD and total phenol removal rates were achieved with a decrease in initial pH and an increase in H₂O₂ dosage. At an initial pH of less than 6.5 and H₂O₂ concentration of 0.3 M, COD removal reached 44-50% and approximately 95% of total phenol removal was achieved at a reaction time of 1 h. The oxygen uptake rate of the effluent measured at a reaction time of 1 h increased by approximately 65% compared to that of the raw coking wastewater. This indicated that biodegradation of the coking wastewater was significantly improved. Several organic compounds, including bifuran, quinoline, resorcinol and benzofuranol were removed completely as determined by GC-MS analysis. The advanced Fenton oxidation process is an effective pretreatment method for the removal of organic pollutants from coking wastewater. This process increases biodegradation, and may be combined with a classical biological process to achieve effluent of high quality.     

焦化废水泡沫分离液的Fenton催化氧化预处理

以焦化废水处理过程产生的泡沫分离液为研究对象，对其进行Fenton催化氧化处理实验，考察H₂O₂用量、Fe²⁺浓度、pH和反应时间4个因素对处理效果的影响，并结合GC/MS方法比较处理前后泡沫分离液中有机物的种类及其生物降解性的变化。结果表明，采用［H₂O₂］=100 mmol/L、［Fe²⁺］=100 mg/L、pH=3、反应时间为30 min的Fenton催化氧化反应条件，可以使分离液的COD去除率达到68%以上；经Fenton处理后，分离液的B/C值由0.12提高至0.38，生物降解性明显改善；通过GC/MS的分析，基本明确分离液中含有的有机物主要为酚、胺、腈、酯类有机物及喹啉、吡啶等杂环化合物，大多数属于难降解且生物毒性较强的有机物。针对这些复杂组分共存的泡沫分离液，利用Fenton试剂较强的氧化能力能够将其含有的有毒/难降解有机物转化为低毒或无毒的小分子有机物，为其后续的生物处理创造良好的条件。     

类Fenton氧化—好氧移动床生物膜法处理抗生素发酵废水

采用类Fenton氧化-好氧移动床生物膜(MBBR)法处理难降解抗生素发酵废水,探讨了H2O2和草酸投加量对类Fenton氧化工艺以及HRT和曝气量对好氧MBBR反应器的影响.实验结果表明,当类Fenton氧化工艺的最佳操作参数为反应溶液H2O2和草酸初始质量浓度分别为150、45 mg/L、30 W/154 nm紫外灯照射1 h、pH为3.0,在曝气搅拌条件下,COD平均去除率为80.9%.当类Fenton氧化工艺出水pH在7.0时,废水中的污染物还可以进一步被混凝去除.好氧MBBR反应器的最佳工艺参数为HRT 12 h、曝气量0.10 m3/h以及填料填充比(体积比)30%,最终废水COD平均去除率为99.1%,达到<污水综合排放标准>(GB 8978-1996)三级标准要求.     

硝基苯类废水的全混态零价铁-芬顿组合预处理工艺优化与工程验证

针对企业硝基氯苯装置产生的高毒性、难降解的硝基苯类废水,开发出全混态零价铁-芬顿组合预处理工艺,并分别优化了零价铁还原和芬顿氧化的工艺条件。结果表明,pH为2.0、零价铁投加量为220 mg/L时,废水中硝基苯类物质的去除率可达98.5%以上。出水pH约为3.0,继续投加3000 mg/L的H₂O₂,Fe²⁺投加比按C(Fe²⁺,mg/L):C(H₂O₂,mg/L)=1:10,1 h内COD去除率可达90%以上,且B/C由0.08提高到0.45。可见该组合预处理工艺可大幅削减废水毒性、改善可生化性,且直接运行成本仅为26.28元/吨,具有良好的环境和经济效益。     

Response surface modeling for optimization heterocatalytic Fenton oxidation of persistence organic pollution in high total dissolved solid containing wastewater

The rice-husk-based mesoporous activated carbon (MAC) used in this study was precarbonized and activated using phosphoric acid. N₂ adsorption/desorption isotherm, X-ray powder diffraction, electron spin resonance, X-ray photoelectron spectroscopy and scanning electron microscopy, transmission electron microscopy, ²⁹Si-NMR spectroscopy, and diffuse reflectance spectroscopy were used to characterize the MAC. The tannery wastewater carrying high total dissolved solids (TDS) discharged from leather industry lacks biodegradability despite the presence of dissolved protein. This paper demonstrates the application of free electron-rich MAC as heterogeneous catalyst along with Fenton reagent for the oxidation of persistence organic compounds in high TDS wastewater. The heterogeneous Fenton oxidation of the pretreated wastewater at optimum pH (3.5), H₂O₂ (4 mmol/L), FeSO₄?7H₂O (0.2 mmol/L), and time (4 h) removed chemical oxygen demand, biochemical oxygen demand, total organic carbon and dissolved protein by 86, 91, 83, and 90 %, respectively.     

Enhanced reduction of phenol content and toxicity in olive mill wastewaters by a newly isolated strain of Coriolopsis gallica

The search for novel microorganisms able to degrade olive mill wastewaters (OMW) and withstand the toxic effects of the initially high phenolic concentrations is of great scientific and industrial interest. In this work, the possibility of reducing the phenolic content of OMW using new isolates of fungal strains (Coriolopsis gallica, Bjerkandera adusta, Trametes versicolor, Trichoderma citrinoviride, Phanerochaete chrysosporium, Gloeophyllum trabeum, Trametes trogii, and Fusarium solani) was investigated. In vitro, all fungal isolates tested caused an outstanding decolorization of OMW. However, C. gallica gave the highest decolorization and dephenolization rates at 30 % v/v OMW dilution in water. Fungal growth in OMW medium was affected by several parameters including phenolic compound concentration, nitrogen source, and inoculum size. The optimal OMW medium for the removal of phenolics and color was with the OMW concentration (in percent)/[(NH₄)₂SO₄]/inoculum ratio of 30:6:3. Under these conditions, 90 and 85 % of the initial phenolic compounds and color were removed, respectively. High-pressure liquid chromatography analysis of extracts from treated and untreated OMW showed a clear and substantial reduction in phenolic compound concentrations. Phytotoxicity, assessed using radish (Raphanus sativus) seeds, indicated an increase in germination index of 23–92 % when a 30 % OMW concentration was treated with C. gallica in different dilutions (1/2, 1/4, and 1/8).

Land spreading of olive mill wastewater: effects on soil microbial activity and potential phytotoxicity

Extremely high organic load and the toxic nature of olive mill wastewater (OMW) prevent their direct discharge into domestic wastewater treatment systems. In addition to the various treatment schemes designed for such wastewater, controlled land spreading of untreated OMW has been suggested as an alternative mean of disposal. A field study was conducted between October 2004 and September 2005 to assess possible effects of OMW on soil microbial activity and potential phytotoxicity. The experiment was carried out in an organic orchard located on a Vertisol-type soil (Jezre'el Valley, Israel) and included two application levels of OMW (36 and 72m(3)ha(-1)). Total microbial counts, and to less extent the hydrolytic activity and soil respiration were increased following the high OMW application level. A bench-scale lab experiment showed that the rate of OMW mineralization was mainly dependent on the general status of soil activity and was not related to previous acclimatization of the soil microflora to OMW. Soil phytotoxicity (% germination and root elongation) was assessed in soil extracts of samples collected before and after each OMW application, using germinating cress (Lepidium sativum L.) seeds. We found direct short-term effect of OMW application on soil phytotoxicity. However, the soil was partly or completely recovered between successive applications. No further phytotoxicity was observed in treated soils as compared with control soil, 3 months after OMW application. Such short-term phytotoxicity was not in correlation with measured EC and total polyphenols in the soil extracts. Overall, the results of this study further support a safe controlled OMW spreading on lands that are not associated with sensitive aquifers.     

Synthetic olive mill wastewater treatment by Fenton’s process in batch and continuous reactors operation

Degradation of total phenol (TPh) and organic matter, (expressed as total organic carbon TOC), of a simulated olive mill wastewater was evaluated by the Fenton oxidation process under batch and continuous mode conditions. A mixture of six phenolic acids usually found in these agro-industrial wastewaters was used for this purpose. The study focused on the optimization of key operational parameters of the Fenton process in a batch reactor, namely Fe²⁺ dosage, hydrogen peroxide concentration, pH, and reaction temperature. On the assessment of the process efficiency, > 99% of TPh and > 56% of TOC removal were attained when [Fe²⁺] = 100 ppm, [H₂O₂] = 2.0 g/L, T = 30 °C, and initial pH = 5.0, after 300 min of reaction. Under those operational conditions, experiments on a continuous stirred-tank reactor (CSTR) were performed for different space-time values (τ). TOC and TPh removals of 47.5 and 96.9%, respectively, were reached at steady-state (for τ = 120 min). High removal of COD (> 75%) and BOD₅ (> 70%) was achieved for both batch and CSTR optimum conditions; analysis of the BOD₅/COD ratio also revealed an increase in the effluent’s biodegradability. Despite the high removal of lumped parameters, the treated effluent did not met the Portuguese legal limits for direct discharge of wastewaters into water bodies, which indicates that coupled chemical-biological process may be the best solution for real olive mill wastewater treatment.     

Enhanced degradation of ortho-nitrochlorobenzene by the combined system of zero-valent iron reduction and persulfate oxidation in soils

ortho-Nitrochlorobenzene (o-NCB) in soil poses significant health risks to human because of its persistence and high toxicity. The removal of o-NCB by both zero-valent iron (ZVI) and chemical oxidation (persulfate) was investigated by batch experiments. The o-NCB removal rate increases significantly from 15.1 to 97.3 % with an increase of iron dosage from 0.1 to 1.0 mmol g^?1. The o-NCB removal rate increases with the decrease of the initial solution pH, and a removal efficiency of 90.3 % is obtained at an initial pH value of 6.8 in this combined system. It is found that temperature and soil moisture could also increase the o-NCB removal rate. The o-NCB degradation rate increases from 83.9 to 96.2 % and from 41.5 to 82.4 % with an increase of temperature (15 to 35 °C) and soil moisture (0.25 to 1.50 mL g^?1), respectively. Compared to the persulfate oxidation system and ZVI system, the persulfate–iron system shows high o-NCB removal capacity. o-NCB removal rates of 41.5 and 62.4 % are obtained in both the persulfate oxidation system and the ZVI system, while the removal rate of o-NCB is 90.3 % in the persulfate–iron system.     

Dephenolization and detoxification of olive-mill wastewater (OMW) by purified biotic and abiotic oxidative catalysts

The capability of two oxidative catalysts, a laccase from Rhus vernicifera and birnessite, a manganese oxide, in the dephenolization and detoxification of two olive-mill wastewater (OMW) samples, C1 and C2, differing for complexity and composition, was evaluated. OMW phenolic extracts (EC1 and EC2) and mono-substrate solutions of phenols mostly present in OMW samples were also tested. Birnessite was more effective than laccase in removing the phenolic content from mono-substrate solutions (more than 70% of each initial phenolic concentration) and of either OMW samples or EC1 and EC2 extracts. For instance, 60% of the total phenolic content of EC1 was removed after 48-h treatment with 5 mg mL(-1) birnessite and the efficiency was lower as greater was the complexity of the OMW sample (only 17% removal from EC2 over the same time span). Phytotoxicity tests with Lepidium sativum and Lycopersicon esculentum seeds and antibacterial toxicity tests with Bacillus megaterium were performed on crude OMW samples and their extract and exhausted fractions before and after the catalytic treatment. Results demonstrated that (a) monomeric phenols were certainly but not exclusively responsible of OMW phytotoxicity, whereas their removal led to a quite complete elimination of the toxicity toward bacterial growth; (b) other components not removable by the oxidative catalysts very likely contribute to OMW phytotoxicity; and (c) the choice of the vegetal species to use in toxicity tests might be crucial for correct and easily interpretable results. Overall the results provided useful information on the possible use of oxidative catalysts for the efficient treatment of complex aqueous wastes such as those deriving from olive industry.     

Membrane filtration of olive mill wastewater and exploitation of its fractions.

Olive mill wastewater (OMW) produced from small units scattered in rural areas of Southern Europe is a major source of pollution of surface and subsurface water. In the present work, a treatment scheme based on physical separation methods is presented. The investigation was carried out using a pilot-plant unit equipped with ultrafiltration, nanofiltration, and reverse osmosis membranes. Approximately 80% of the total volume of wastewater treated by the membrane units was sufficiently cleaned to meet the standards for irrigation water. The concentrated fractions collected in the treatment concentrates were characterized by high organic load and high content of phenolic compounds. The concentrates were tested in hydroponic systems to examine their toxicity towards undesired herbs. The calculations of the cost of the overall process showed that fixed and operational costs could be recovered from the exploitation of OMW byproducts as water for irrigation and/or as bioherbicides.     

Dose and frequency dependent effects of olive mill wastewater treatment on the chemical and microbial properties of soil

Olive mill wastewater (OMW) is a problematic by-product of olive oil production. While its high organic load and polyphenol concentrations are associated with troublesome environmental effects, its rich mineral and organic matter contents represent valuable nutrients. This study aimed to investigate the valorization of this waste biomass as a potential soil conditioner and fertilizer in agriculture. OMW was assayed at three doses 50, 100, and 200 m³ ha⁻¹ year⁻¹) over three successive years in olive fields. The effects of the effluent on the physico-chemical and microbial properties of soil-layers were assessed. The findings revealed that the pH of the soil decreased but electrical conductivity and organic matter, total nitrogen, sodium, and potassium soil contents increased in proportion with OMW concentration and frequency of application. While no variations were observed in phosphorus content, slow increases were recorded in calcium and magnesium soil contents. Compared to their control soil counterparts, aerobic bacteria and fungi increased in proportion with OMW spreading rates. The models expressing the correlation between progress parameters and OMW doses were fitted into a second degree polynomial model. Principal component analysis showed a strong correlation between soil mineral elements and microorganisms. These parameters were not related to phosphorus and pH.     

Advanced oxidation processes for the treatment of olive-oil mills wastewater

In this work, the treatment of an actual industrial waste with three advanced oxidation processes (AOP) has been studied: conductive-diamond electrooxidation (CDEO), ozonation and Fenton oxidation. The wastewater comes from olive-oil mills (OMW) and contains a COD of nearly 3000 mg dm(-3). CDEO allowed achieving the complete mineralization of the waste with high current efficiencies. Likewise, both ozonation and Fenton oxidation were able to treat the wastes, but they obtained very different results in terms of efficiency and mineralization. The accumulation of oxidation-refractory compounds as final products excludes the use of ozonation and Fenton oxidation as a sole treatment technology. This confirms that besides the hydroxyl-radical mediated oxidation, CDEO combines other important oxidation processes such as the direct electro-oxidation on the diamond surface and the oxidation mediated by other electrochemically formed compounds generated on this electrode.     

Nanoscale zero-valent iron/AC as heterogeneous Fenton catalysts in three-dimensional electrode system

In the present work, nanoscale zero-valent iron/activated carbon (NZVI/AC) was investigated as heterogeneous Fenton catalyst in three-dimensional (3D) electrode system for methyl orange (MO) degradation. Some important operating parameters such as cathodic potential, pH, and O₂ flow rate were investigated, exhibiting good decolorization. The mineralization of MO was significantly improved by 20–35 % compared to two-dimensional (2D) AC system at the optimum conditions. Although the TOC removal of AC was higher than NZVI/AC due to its good adsorption capacity initially, heterogeneous Fenton catalysis played a more and more important roles in the following test. After eight runs, NZVI/AC still exhibited excellent catalytic properties with low iron leaching. Further, a relatively comprehensive mechanism of NZVI/AC as particle electrodes in 3D system was proposed.     

Treatment of a wastewater from a pesticide manufacture by combined coagulation and Fenton oxidation

The treatment of a non-biodegradable agrochemical wastewater has been studied by coupling of preliminary coagulation—flocculation step and further Fenton oxidation. High percentages of chemical oxygen demand (COD) removal (up to 58 %) were achieved in a first step using polyferric chloride as coagulant. This reduced significantly the amount of H₂O₂ required in the further Fenton oxidation. Using the stoichiometric amount relative to COD around 80 % of the remaining organic load was mineralized. The combined treatment allowed achieving the regional discharge limits of ecotoxicity at a cost substantially lower than the solution used so far where these wastewaters are managed as hazardous wastes.     

Applicability of Fenton and H2O2/UV reactions in the treatment of tannery wastewaters

In this paper we evaluated the H2O2/UV and the Fenton's oxidation processes for the treatment of tannery wastewater under different experimental conditions. Efficiencies were judged by the amounts of organic substances degraded or eliminated under these treatment techniques. Daphnia magna and Vibrio fischeri were used to monitor toxicity. Organic compounds contained in the untreated and treated tannery wastewater were determined and identified using substance specific techniques. Gas chromatography-mass spectrometry (GC-MS) in positive electron impact (EI(+)) mode was applied to determine volatile organics. Atmospheric pressure ionization (API) mass (MS) and tandem mass spectrometry (MS-MS) coupled with flow injection analysis (FIA) or liquid chromatography (LC) were used to detect or identify polar organic pollutants. The experimental results indicated that both oxidation processes--H2O2/UV at pH 3 and Fenton at pH 3.5--are able to reduce TOC content by mineralisation of the organic compounds.     

Sequential treatment of olive oil mill wastewater with adsorption and biological and photo-Fenton oxidation

Olive oil mill wastewater (OMWW), a recalcitrant pollutant, has features including high phenolic content and dark color; thereby, several chemical or physical treatments or biological processes were not able to remediate it. In this study, the treatment efficiencies of three treatments, including adsorption, biological application, and photo-Fenton oxidation were sequentially evaluated for OMWW. Adsorption, biological treatment, and photo-Fenton caused decreasing phenolic contents of 48.69 %, 59.40 %, and 95 %, respectively. However, after three sequential treatments were performed, higher reduction percentages in phenolic (total 99 %) and organic contents (90 %) were observed. Although the studied fungus has not induced significant color reduction, photo-Fenton oxidation was considered to be an attractive solution, especially for color reduction. Besides, toxicity of OMWW treatment was significantly reduced.