Oxidation For Wastewater Treatment Research Articles

Nitrite Oxidation in Wastewater Treatment: Microbial Adaptation and Suppression Challenges.

Microbial nitrite oxidation is the primary pathway that generates nitrate in wastewater treatment systems and can be performed by a variety of microbes: namely, nitrite-oxidizing bacteria (NOB). Since NOB were first isolated 130 years ago, the understanding of the phylogenetical and physiological diversities of NOB has been gradually deepened. In recent endeavors of advanced biological nitrogen removal, NOB have been more considered as a troublesome disruptor, and strategies on NOB suppression often fail in practice after long-term operation due to the growth of specific NOB that are able to adapt to even harsh conditions. In line with a review of the history of currently known NOB genera, a phylogenetic tree is constructed to exhibit a wide range of NOB in different phyla. In addition, the growth behavior and metabolic performance of different NOB strains are summarized. These specific features of various NOB (e.g., high oxygen affinity of Nitrospira, tolerance to chemical inhibitors of Nitrobacter and Candidatus Nitrotoga, and preference to high temperature of Nitrolancea) highlight the differentiation of the NOB ecological niche in biological nitrogen processes and potentially support their adaptation to different suppression strategies (e.g., low dissolved oxygen, chemical treatment, and high temperature). This review implicates the acquired physiological characteristics of NOB to their emergence from a genomic and ecological perspective and emphasizes the importance of understanding physiological characterization and genomic information in future wastewater treatment studies.

Scale-up modelling and life cycle assessment of electrochemical oxidation in wastewater treatment

The need to improve current wastewater treatments to ensure a clean and sustainable water supply is an unquestionable contemporary challenge. It is therefore essential to facilitate knowledge transfer between research institutions and the industry by developing novel technologies to a proof-of-concept stage, demonstrating both treatment efficiency and compliance with environmental criteria. This study has combined process modelling for the design of an electrochemical Advanced Oxidation Process (eAOP) to remove carbamazepine (CBZ) from wastewater with the identification of the environmental impacts associated with its operation. A comprehensive set of scenarios considering several reactor designs and operating conditions provides the assessment framework to identify the influence of different process variables on the environmental profile of the pilot-scale eAOP. The most sustainable treatment corresponds to the operation of a standardised modular reactor in batch mode, especially when the wastewater has a low concentration of scavengers, such as other ions, organics or pollutants. Nevertheless, in all scenarios evaluated, the main environmental hotspot was attributed to the electrical energy consumed by the auxiliary pumps rather than the electrochemical reactor itself. In comparison to other AOPs, our system showed considerably lower impacts in the global warming potential (GWP) category, with a minimum of 7.6 kg CO2 eq per g CBZ removed for the most promising scenario. This demonstrates the implementation potential of eAOPs as well as the importance of data from scaled-up experiments, where optimisation should focus on mitigating the impacts of energy-intensive pieces of equipment.

DNA-based stable isotope probing deciphered the active denitrifying bacteria and triclosan-degrading bacteria participating in granule-based partial denitrification process under triclosan pressure

Granule-based partial denitrification (PD) is a technology that can supply stable nitrite for applying anaerobic ammonia oxidation in wastewater treatment, and triclosan (TCS) is a frequently detected antibacterial agent in wastewater treatment plants, therefore it is possible that TCS could enter into wastewater that is treated using PD technology. However, the active microorganisms responsible for PD and TCS removing in granule-based PD system have not been clearly identified and it is currently not clear how TCS affects the PD process. In this study, the impacts of TCS on PD performance, PD microbial community, antibiotic resistance genes (ARGs), active PD bacteria and TCS-degrading bacteria in a granule-based PD system were investigated. 3 mg/L TCS had adverse influence on PD process, but PD system could recover gradually after inhibiting of 10 days. After a period of domestication, PD granular sludge could achieve 10.66% of TCS degradation efficiency and 43.62% of TCS adsorption efficiency. Microbes might increase their resistance to TCS by increasing the secretion of extracellular polymeric substances, and the secretion of protein might play a more pivotal role than the secretion of polysaccharides in resisting TCS. The short-term shock of TCS might cause the propagation of acrA-03, while the long-term operation of TCS could propagate fabK and intI1. DNA stable isotope probing assay indicated that Thauera was active PD bacteria and TCS-degrading bacteria in the granule-based PD system, and it could contribute to nitrite accumulation and TCS degradation, simultaneously.

Facilely Prepared Cl-Doped Graphene as an Efficient Anode for the Electrochemical Catalytic Degradation of Acetaminophen.

The application of electrochemical catalytic oxidation in wastewater treatment with powerful Cldoped graphene as an anode has been discussed as a novel approach to degrade acetaminophen effectively. The characteristics of Cl-doped graphene that were related to Cl loading content and microscopic morphology were analyzed by using several instruments, and the defects created by Cl doping were identified. Quenching experiments and electron paramagnetic resonance detection were proposed to clarify the mechanism underlying the production of active free radicals by Cldopedgraphene. The degradation results indicated that efficiency increased with the percentage of Cl atoms doped into the graphene. The best degradation efficiency of acetaminophen could reach 98% when Cl-GN-12 was used. In the process of electrocatalytic oxidation, O•-₂, and active chlorine, as the main active species, persistently attacked acetaminophen into open-ring intermediates, such as 4-chlororesorcinol, and finally into CO₂ and H²O.

Catalytic activity comparison of natural ferrous minerals in photo-Fenton oxidation for tertiary treatment of dyeing wastewater.

Natural ferrous minerals are readily available and recyclable catalysts in photo-Fenton-like oxidation for wastewater treatment. In this work, typical ferrous oxide and sulfide minerals including magnetite, chalcopyrite, and pyrrhotite were exploited as catalysts in heterogeneous photo-Fenton oxidation for purification of biological effluent of dyeing wastewater. In a wide initial pH range (3.0~7.5), ferrous mineral-based heterogeneous photo-Fenton-like reactions were proven to be effective on the oxidation of recalcitrant pollutants. COD removals achieved 60.57%, 58.83%, and 57.41% using pyrrhotite, chalcopyrite, and magnetite, respectively, as catalyst under ultraviolet irradiation of 220~275 nm at H2O2 concentration of 9.8 mM. The corresponding COD removals were 51.75% and 34.09% with or without ferrous sulfate additions in UV/H2O2 systems. Minerals exhibited excellent stability and reusability with photo-catalytic activity reduction of less than 10% in the reuse of 5 cycles. Dissolved iron concentrations were determined to be 1.86 mg L-1, 4.62 mg L-1, and 7.53 mg L-1 for magnetite, chalcopyrite, and pyrrhotite, respectively, at pH 3 and decreased to zero in neutral pH environment, which were much lower than those required for homogenous Fenton reaction. It was deduced that oxidation of recalcitrant pollutants was mainly catalyzed by Fe(II) on the mineral surface. The more reactive oxygen species such as hydroxyl radicals were resulted from the reaction of surface Fe (II) with H2O2, H2O2 photolysis, and charge separation of minerals under UV irradiation.

Synthesis of novel erdite nanorods for the activation of peroxymonosulfate during p-nitrophenol wastewater treatment.

Fe-bearing salt and minerals are common reagents used in activating peroxymonosulfate (PMS) for Fenton-like oxidation in wastewater treatment. Fe-bearing reagents are used in mass production, which generate abundant Fe-bearing waste sludge in the absence of a reductant for Fe3+/Fe2+ cycling. Herein, a novel Fe/S-bearing mineral, erdite, was synthesized with a one-step hydrothermal route. The material exerted an Fe/S synergetic effect for p-nitrophenol degradation upon PMS activation and showed a one-dimensional structure similar to that of (FeS2)nn-. It contained short rods with diameters of 100 nm and lengths ranging from 200 to 400 nm. It grew radically to 0.8-2 μm in length upon the addition of MnO2. Ps-0.5, prepared by adding MnO2 in an Mn/Fe molar ratio of 0.5, showed optimal efficiency in removing approximately 99.4% of p-nitrophenol upon PMS activation. Only 3.3% of p-nitrophenol was removed without MnO2. The efficiency of p-nitrophenol removal through Ps-0.5 activation was higher than that through FeSO4, nanoscale zero-valent iron (nZVI), CuFeS2, and MnSO4 activation. The formed erdite rods were spontaneously hydrolyzed to Fe/S-bearing flocs, in which an electron was used by structural S to reduce Fe3+ to Fe2+ upon PMS activation. The reduction resulted in a high p-nitrophenol removal rate. This study provided new insight into the development of an effective PMS activator in wastewater treatment.

Degreasing cotton used as pore-creating agent to prepare hydrophobic and porous carbon cathode for the electro-Fenton system: enhanced H2O2 generation and RhB degradation.

A porous carbon cathode was prepared using graphite, polytetrafluoroethylene (PTFE), and degreasing cotton (DC) through sintering treatment. The carbonization of DC by heat treatment played an ideal role in pore-creating, which weakened the mass transfer resistance of O2, and as a result, the adoption of degreasing cotton significantly improved the performance of H2O2 electro-generation. The optimized cathode was able to generate 567 mg L-1 H2O2 with a current efficiency (CE) of 86.7% by the electrochemical reaction of 60 min in a divided reactor. Furthermore, the degradation of rhodamine B (RhB) was carried out by an electro-Fenton system using the optimal cathode selected. The developed electro-Fenton system exhibited an excellent RhB degradation performance. The RhB solution of 50 mg L-1 was decolorized completely by the treatment of 10 min. Moreover, the degradation of 50~90 mg L-1 RhB solution presented over 90% TOC removal by the treatment of 120 min, indicating the ideal mineralization of organic pollutants. In addition, it was found that •OH was the major oxidizing specie responsible for the organics degradation. Finally, the possible pathway of RhB degradation in the electro-Fenton system was proposed by GC-MS analysis. The adoption of natural fibers for pore-creating provides an innovative and low-cost method to prepare porous cathode, which may promote the application of electro-Fenton oxidation in wastewater treatment.

Degradation of sulfamethazine by persulfate activated with nanosized zero-valent copper in combination with ultrasonic irradiation

Commercial nanosized zero-valent copper (nZVC) was used as persulfate (PS) activator in combination with ultrasonic irradiation (US) for the oxidative degradation of typical antibiotic sulfamethazine (SMZ) in this study. Compared with other processes, the combined nZVC-PS-US process significantly enhanced SMZ removal due to a synergistic interaction between sonolysis and a heterogeneous reaction. Almost complete SMZ removal was achieved within 60 min using a PS dose of 0.5 mM and a nZVC concentration of 64 mg/L at pH 3.06, with US at 0.4 W/mL and 40 kHz. The presence of NO3–, SO42−, HCO3–, Cl− and humic acid demonstrated adverse effects on SMZ degradation. Moreover, the inhibitory effect of different inorganic anions on SMZ degradation followed the sequence of HCO3– > SO42−> NO3– > Cl− > no salt. Electron spin resonance and radical scavenging tests indicate that the primary reactive species was SO4•−, while •OH played a less important role. Cu+ is an active copper species in activating PS. The production of Cu+ and Cu2+ induced by Cu0 and US favored the continuous decomposition of PS as well as the production of SO4•− at the surface of nZVC. Nine intermediates were identified and four oxidation pathways were proposed, the aniline moiety oxidation, SO2 extrusion/smile-type rearrangement and S-N bond cleavage were the major pathways. Practicality and effectiveness of nZVC-PS-US was confirmed when other organic micro-pollutants and SMZ added to raw waters were tested. The findings reported here offer promising implications in developing the utilization of nZVC in advanced oxidation for treatment of wastewater.

Multifunctional Piezoelectric Heterostructure of BaTiO3@Graphene: Decomplexation of Cu-EDTA and Recovery of Cu

About 3.93 billion tons of wastewater containing heavy metal complexes are discharged (e.g., from the electroplating industry) every year in China alone. It is challenging to appropriately treat such wastewaters. Here, a multifunctional composite nanowires BaTiO3@graphene was designed based on Comsol simulations and made into 3D millimeter-sphere in order to facilitate practical application. Results indicate 100% of Cu-EDTA was decomplexed in situ via piezoelectric potential by BaTiO3@graphene. Notably, the addition of graphene sharply increased the surface potential (from 19.8 ± 0.97 to 96.8 ± 1.48 mV) of BaTiO3@graphene by its flexoelectric effect then effectively promoted piezoelectric electrons to be separated and transferred, which favors the piezoelectric catalysis. Moreover, the released Cu(II) from Cu-EDTA decomplexation were recovered simultaneously via the interaction on graphene groups. This method efficiently recovered Cu(II) to avoid the consumption of massive chemical reagents and the generation of secondary hazardous solid waste containing heavy metal ions, compared with the conventional oxidative decomplexation/precipitation strategy for heavy metal complexes removal. Piezoelectric catalysis paves a new possibility for advanced oxidation in wastewater treatment.

Enhanced electro-catalytic generation of hydrogen peroxide and hydroxyl radical for degradation of phenol wastewater using MnO2/Nano-G|Foam-Ni/Pd composite cathode

To improve the electro-catalytic degradation efficiency of the cathode in electrochemical advanced oxidation processes, MnO2 modified Nano-graphite (MnO2/Nano-G) and Pd loaded Foam-Ni (Foam-Ni/Pd) composites were prepared by the chemical redox and electro-deposition methods, respectively, and a two-layer type MnO2/Nano-G|Foam-Ni/Pd composite cathode was prepared with the chitosan as a binder. The composites were characterized by X-ray diffraction, scanning electrons microscopy and X-ray photoelectron spectroscopy. Results showed that the mix-crystal structural MnO2 (α-MnO2 and γ-MnO2) nanorods with length of 80–200 nm and width of 20–50 nm were uniformly loaded on the Nano-G surface, and the three-dimensional Pd° metal trees/crystals were tightly deposited on the Foam-Ni substrate. The as-prepared cathode was applied to the electro-catalytic degradation of phenol wastewater, and the reaction parameters were optimized. Compared with MnO2/Nano-G|Foam-Ni and Nano-G|Foam-Ni cathodes, the degradation efficiency of phenol by MnO2/Nano-G|Foam-Ni/Pd cathode was significantly improved. The removal efficiencies of phenol and total organic carbon (TOC) by MnO2/Nano-G|Foam-Ni/Pd cathode reached 98.7% and 85.3% after 120 min electrolysis under oxygen aeration condition, respectively. The optimal reaction parameters were current density of 39 mA cm−2, electrolyte (Na2SO4) concentration of 0.1 mol L−1, electrode distance of 4 cm and initial pH of 7. By determining the variations of H2O2 and OH content in the cathode chamber, it was found that Pd metal crystals improved the reduction of O2 to H2O2 and MnO2 nanorods accelerated the dissociation of H2O2 to OH, producing more H2O2 and OH to oxidize phenol and eliminate TOC in wastewater. The results in this study provide useful information for the control of refractory organic pollutants with electrochemical advanced oxidation in wastewater treatment.

Porous TiO2 /BDD/CF Ternary Composite Applied on Brilhant Green Dye Electrochemical Oxidation

Introduction The dye contamination in wastewaters is mainly due to the textile sector which generating large volumes of toxic wastewater. In this context, dye oxidation has been studied using different chemical and electrochemical processes. Particularly, electrochemical technique depends on the high performance of electrode material. Boron doped diamond has appeared as singular material for electrochemical oxidation in wastewater treatment, mainly due to its very large potential widow, that allows reaching high anodic potential for hydroxyl radical (OH•) generation [1]. In this context, carbon fiber (CF) is a great interest substrate to grow BDD films because it exhibits high surface area allowing high active site density in a homogeneous porosity distribution. On the other hand, titanium dioxide (TiO2) is one of the most studied semiconducting oxide for different electrochemical applications because it is stable in both alkaline and acid media, besides its high electrochemically surface area [2]. Thus, ternary and binary composites were produced and characterized considering the constituent materials of carbon fibers (CF), boron doped diamond (BDD), and titanium dioxide (TiO2) as electrodes for electrochemical dye oxidation. Experimental CF samples were produced from polyacrylonitrile (PAN) precursor at heat treatment temperature of 1000 ºC and were cut in 25 x 25 mm2 to produce large electrode area. BDD films were grown on CF substrate by hot filament chemical vapor deposition (HFCVD) the following growth parameters: 750 °C, 30 Torr, 8h and gas mixture of 2/198 % CH4/H2. Boron source was obtained by an additional hydrogen line passing through a bubbler with B2O3 dissolved in methanol by controlling the B/C ppm ratio. TiO2 depositions on BDD/CF substrate was obtained by anodic hydrolysis of TiCl3 under potentiostatic mode, at a fixed potential of 0.75 V for 60 min in a 5 mmol.L-1 TiCl3 + 0.1 mol.L-1 KCl (pH = 2) aqueous solution. All the electrochemical experiments were performed in a conventional three-electrode glass cell, using a platinum wire as a counter electrode an Ag/AgCl/KCl (sat) as the reference electrode. Both composite materials were characterized by field emission gun-scanning electron microscopy (FEG-SEM) images, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). CF, TiO2/CF, and TiO2/BDD/CF were used as electrodes for electrooxidation of the Brilliant Green dye at different current densities using 100 mg L-1 of the Brilliant Green dye in K2SO4 0.1 mol L-1 solution for 300 min. Their efficiency was analyzed by UV/VIS Spectrophotometry and by Total Organic Carbon techniques considering the influence of the electrode characteristics in the degradation process. Results The binary and ternary TiO2/CF and TiO2/BDD/CF composites were firstly analyzed by FEG-SEM images taking into account these two sample considering the TiO2 deposits. The FEG-SEM images for TiO2/CF deposited at 30 min showed a thick TiO2 layer covering the fibers, with CF surface scratches or cracks completely filled by TiO2 film. For ternary composite, after 60 min of deposition the rougher film texture is dominant and homogenous covering all diamond grains. This morphology seems to be suitable to keep the contributions of these constituent material properties for TiO2/BDD/CF composite, mainly related to the BDD importance for electrochemical oxidation processes of organic pollutants. Concerning the Brilhant Green Dye electrochemical oxidation, the results showed that all the electrodes were efficient in the solution discolorization. Also, the organic compound mineralization showed a decrease according to TOC measurements of the electrolyzed samples. Considering the synergism between two good anode materials, BDD and TiO2 for organic electrodegradation, both of them binary and ternary composites presented the good performance. However, the ternary electrode, probably associated to its highest electrode surface area, showed the best performance. Conclusion Anodic hydrolysis of TiCl3 under potentiostatic mode was a suitable procedure to produce binary and ternary composites. In addition, both of them showed satisfactory results in electrolysis processes to degrade the Brilhant Green Dye. Acknowledgments This work was supported by FAPESP, Process 2016/13393-9, CAPES, and CNPq Brazilian Agencies.

The laccase-like reactivity of manganese oxide nanomaterials for pollutant conversion: rate analysis and cyclic voltammetry

Nanostructured manganese oxides, e.g. MnO2, have shown laccase-like catalytic activities, and are thus promising for pollutant oxidation in wastewater treatment. We have systematically compared the laccase-like reactivity of manganese oxide nanomaterials of different crystallinity, including α-, β-, γ-, δ-, and ɛ-MnO2, and Mn3O4, with 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 17β-estradiol (E2) as the probing substrates. The reaction rate behaviors were examined with regard to substrate oxidation and oxygen reduction to evaluate the laccase-like catalysis of the materials, among which γ-MnO2 exhibits the best performance. Cyclic voltammetry (CV) was employed to assess the six MnOx nanomaterials, and the results correlate well with their laccase-like catalytic activities. The findings help understand the mechanisms of and the factors controlling the laccase-like reactivity of different manganese oxides nanomaterials, and provide a basis for future design and application of MnOx-based catalysts.

Selective Electrochemical Oxidation of Lactic Acid Using Iridium-Based Catalysts

Catalysts that allow for selective oxidation of organic compounds in solution are useful tools in chemical synthesis, waste remediation, and renewable energy storage schemes. Of these, iridium oxide and iridium-based molecular compounds are frequently employed as catalysts to oxidize substrates ranging from small organic molecules to water. Here, we study the mechanism and evaluate the potential of iridium-based catalysts for small molecule oxidation in wastewater treatment, using lactic acid as a substrate. By investigating the reaction products, kinetic isotope effects, and electrochemical properties of iridium oxide and a molecular analogue on a high surface area antimony-doped tin oxide (ATO) support, we find evidence for a new iridium-catalyzed pathway for lactic acid oxidation. Applying this at concentrations representative of effluent from dairy production processes, we show that iridium oxide can selectively remove small amounts of lactic acid from water by oxidizing it to CO2 with concomitant cat...

Occurrence of Steroid Sex Hormone Progesterone in Influent and Effluent of Oxidation Pond and the River Outlet of Waste Water Treatment Case Study

Background and Objective: This studied about the occurrence of Endocrine Disrupting Compound (EDC) in interest of steroid sex hormone progesterone excretion in the environment, that focusing on water resource in terms of effluent and influent of the waste water treatment into the outlet river and environment. Materials and Methods: A method called dispersive liquid-liquid micro extraction with solidification of floating organic drop followed by High Performance Liquid Chromatography (HPLC) was used for determination of progesterone. The water sample was obtained through grab sample from the influent and effluent of waste water treatment-oxidation pond and the outlet river (Kalansanan river) where the effluent was discharged. Results: Based on the result obtained it is found that there were few detections and occurrences of steroid sex hormone progesterone in the study with detection range from lowest concentration of 4.278±7.411 ng mL–1 and the highest concentration recorded at 16.687±6.233 ng mL–1 and the average concentration of progesterone is at 6.356±3.112 ng mL–1. The highest detection of the progesterone was recorded in the effluent site sampling that indicates that the conventional treatment plant was not able to remove steroid sex hormone progesterone effectively and efficiently. Conclusion: From that point of the study, monitoring on the progesterone presence and status should be done due to the presence of progesterone even in nanogram per milliliter in environment bring and posed a life threat towards the living organism in the environment.

Electrochemical oxidation of the poultry manure anaerobic digested effluents for enhancing pollutants removal by Chlorella vulgaris

ABSTRACTThe mechanisms and pseudo-kinetics of the electrochemical oxidation for wastewater treatment and the synergistic effect of combining algal biological treatment were investigated. NaCl, Na2SO4 and HCl were applied to compare the effect of electrolyte species on nutrients removal. NaCl was proved to be more efficient in removing ammonia (), total phosphorus (TP), total organic carbon (TOC) and inorganic carbon (IC). oxidation by using Ti/Pt–IrO2 electrodes was modelled, which indicates that the removal followed the zero-order kinetic with sufficient Cl− and the first-order kinetic with insufficient Cl−, respectively. The feasibility of combining electrochemical oxidation with microalgae cultivation for wastewater treatment was also determined. A 2 h electrochemical pretreatment reduced 57% , 76% TP, 72% TOC and 77% IC from the digested effluent, which is applied as feedstock for algae cultivation, and resulted in increasing both the biomass production and pollutants removal efficiencies of the algal biological process.

Interaction of tannic acid with ferric iron to assist 2,4,6-trichlorophenol catalytic decomposition and reuse of ferric sludge as a source of iron catalyst in Fenton-based treatment

A comprehensive study of the catalytic behaviour of Fe3+ in the presence of tannic acid during the Fenton-based treatment of chlorophenols-contaminated water was performed. The ability of the iron-containing sludge to catalyse the Fenton-based process was assessed and the mechanistic behaviour of tannic acid in the iron dissolution was evaluated.Tannic acid, a constituent of pulp and paper industry water effluent and natural water, enhanced the 2,4,6-trichlorophenol catalytic decomposition in Fe3+-activated H2O2 oxidation system by reducing of the Fe3+. The Fe3+ reductive mechanism by tannic acid incorporated tannic acid–Fe3+ complex formation and decay through an electron transfer reaction to form Fe2+. An indirect measurement of hydroxyl radical (HO) by the deoxyribose method indicated a considerable increase in HO by Fe3+/H2O2 in the presence of tannic acid. A pseudo-first reaction rate constant of 2,4,6-trichlorophenol degradation by Fe2+/H2O2 was high and close to that of Fe3+/H2O2 with tannic acid. Degradation of tannic acid along with that of 2,4,6-trichlorophenol required optimization of H2O2 and Fe3+ dosages to balance HO formation and scavenging.Acidic reaction media (pH 3.0) and the presence of tannic acid favoured 2,4,6-trichlorophenol degradation by H2O2 oxidation induced by iron dissolved from ferric oxyhydroxide sludge. The reuse of ferric oxyhydroxide sludge as a catalyst source in the Fenton–based process can minimise the production of hazardous solid waste and the overall cost of the treatment.This study highlights the ability of tannic acid-Fe3+ complexes to participate in Fe3+ reductive pathway and, as a result, to allow reuse of non-regenerated ferric oxyhydroxide sludge for activation of H2O2 oxidation in wastewater treatment at acidic pH.

Improvement in iron activation ability of alachlor Fenton-like oxidation by ascorbic acid

The addition of a strong reductant, l-ascorbic acid (AA), to Fe3+/hydrogen peroxide (H2O2) improved alachlor degradation substantially. AA in the form of ascorbate monoanion undergoes a two-step oxidation to yield dehydroascorbic acid through the formation of intermediate semidehydroascorbate and ascorbyl radicals that are responsible for the autocatalytic transformation of Fe3+ to Fe2+. The ability of AA to reduce Fe3+ to Fe2+ and propagate the formation of hydroxyl radicals was confirmed by the indirect measuring of hydroxyl radicals. Hydroxyl radicals production and alachlor degradation by H2O2/AA resulted. Alachlor degradation rate by Fe3+/H2O2/AA was similar to that obtained by Fe2+/H2O2, although a much lower alachlor degradation and mineralization by Fe3+/H2O2 was achieved. The kinetics of alachlor removal by Fe2+/H2O2 and Fe3+/H2O2/AA were characterized by a rapid decay (0–1min) because of a higher formation of hydroxyl radicals and then by a slower decay (1–120min). The determination of a second-order reaction rate constant of hydroxyl radicals with alachlor relied on the competitive reactions of deoxyribose and alachlor with hydroxyl radicals. A rate constant of 6.9×109M−1s−1 (correlation coefficient of 0.997) implies that the reaction rate is close to that of diffusion-controlled reactions in water, and indicates that the hydroxyl radicals play a predominant role during oxidation. Phenylacetamide compounds that were primary by-products of alachlor degradation allowed for the prediction of the general reaction pathway. This study highlights the ability of AA to reduce Fe3+ making a presumption for non-regenerated ferric oxyhydroxide sludge reuse for activation of H2O2 oxidation in wastewater treatment at acidic pH.

Trends in the Intensification of the Fenton Process for Wastewater Treatment: An Overview

The implementation of increasingly stringent regulations for wastewater discharge has enforced research efforts toward either the implementation of novel treatments or the improvement of those presently available. The literature on the use of Fenton oxidation in wastewater treatment has established this method as one of the most effective and suitable process for the abatement of recalcitrant water pollutants. However, despite the many advantages of the conventional Fenton process, there are issues relative to pH modulation, the cost associated to H2O2 and catalyst consumption as well as to sludge disposal that limit a more extended full-scale application. In recent years, several solutions have been developed for the sake of improving Fenton (or Fenton-like) oxidation as a cost-effective technology. This paper presents a thorough review on the different ways of intensifying the Fenton by using radiation, electrochemistry, and/or heterogeneous catalysts, as well as by optimizing the main operating conditions in the conventional homogeneous system. The application of these enhanced technologies to synthetic and real industrial wastewaters is described and discussed.

Probabilistic Analysis of Municipal Solid Waste Landfill Slope

Since 2001, the population at the second biggest city of Thailand, Nakhonratchasima has increased more than 10 %, this lead to generate a substantial volume of solid waste. In this situation creates two distinct problems: (i) a lack of cleanliness around the city; and (ii) solid waste disposal. Approximately 189 tonnes of solid waste are generated each day in the city municipality of Nakhonratchasima. Collected waste is currently disposed to an open landfill located on the citys outskirts. The landfill is located at the former waste water treatment oxidation ponds of a starch factory and has an area of 302,000 m2. In addition to the 180 tones of domestic waste, another 20 tones of industrial waste are land-filled each day. It is known that the main problem of landslide in Municipal Solid Waste (MSW) come from unstable of slope that caused by height [1,2] and rainfall infiltration condition [3,.The MSW and related research of the slpoe stability of MSW are in the early stage in Thailand and has no standards to control its landfills and rereutlization. Thus, the objective of this study is to investigate the probability slope stability analysis of MSW landfill slope by consider with MSW height and rainfall infiltration condition. This study is conducted using laboratory data and Monte Carlo Simulations (MCS) are carried out to obtain reliability index (β) and probability of failure (Pf) for the stability of landfill slope. The result shown the 2 cases, the first case is investigated on slope 1 : 2 (10 m. Height) and the second case is slope 1:2 (15 m. Height). Two case studies will find out the effect on the rainfall infiltration condition increase40% 60% and 80% of unit weight.

On the Limitation of Fenton Oxidation Operational Parameters: A Review

Abstract The literature on the use of Fenton oxidation in wastewater treatment has established the method as one of the most effective and suitable methods for recalcitrant wastewater treatment. It is an advanced oxidation process (AOP) that utilises the highly reactive hydroxyl radical (•OH) to aggressively and non-selectively destroy organic contaminants. The Fenton oxidation possesses environmental and economic benefits coupled with effective mineralisation of most wastewater organics. Broadly, the Fenton oxidation encompasses three types of oxidation routes for the production of •OH: (i) through the use of Fenton reagents alone, termed classical Fenton oxidation (CFO), (ii) assisted by means of UV (photo-Fenton), or (iii) electron beams (electro-Fenton). However, this review is limited to CFO, which involves the catalytic decomposition of hydrogen peroxide (H2O2) by suitable transition metals to generate •OH. Despite the many advantages of the CFO process, there are issues related to operational parameters and the final treated wastewater, the most notable being pH modulation, the presence of the catalyst and the cost of the oxidant (H2O2). Furthermore, sludge generation constitutes an apparent drawback to the utilisation of this technology. This paper attempts to review the highlighted limitations and presents researches and advances reported in the literature addressing these issues.