Biorecalcitrant Pollutants Research Articles

Bio-recalcitrant pollutants removal from wastewater with combination of the Fenton treatment and biological oxidation

The implementation of the Fenton treatment as an intermediate step in combined technological scheme for the removal of bio-recalcitrant organic pollutants from industrial effluents is proposed in this study. The treatment schemes for the purification of three heavily polluted wastewaters originated from a municipal non-hazardous waste landfill, industrial hazardous waste landfill and plywood manufacturing factory were developed. Accordingly, the wastewaters were subjected to aerobic biological treatment (BIO) combined with the Fenton process with the final aim of establishing universally applicable treatment scheme.The study demonstrated that the Fenton oxidation can be successfully included in the high-strength wastewater treatment scheme as an intermediate treatment step for the removal of bio-recalcitrant organics fraction. The elaborated BIO-Fenton-BIO approach was found to be cost-effective for the total organic load reduction and for the selected specific pollutants removal from the studied high-strength wastewaters. Consequently, it could be considered suitable for broader practical implementation.

Enhancing degradation and mineralization of tetracycline using intimately coupled photocatalysis and biodegradation (ICPB)

Intimately coupled photocatalysis and biodegradation (ICPB) has been studied for treating bio-recalcitrant pollutants. The key principle of ICPB is that photocatalysis occurs on a porous carrier’s outer surface, and biofilms are present in the interior, where they are protected from inhibition. Little is known regarding the ability of ICPB to degrade antibiotics, and a primary issue is whether or not the bacteria in the carriers’ interior can acclimate to biodegrade the products from photocatalysis of antibiotics. This study evaluated the removal and mineralization of tetracycline hydrochloride (TCH) using visible-light-induced ICPB (called VPCB) with Ag-doped TiO2 as the photocatalyst. The biofilms inside the VPCB carriers could mineralize the photocatalytic products, which led to more than 20% enhanced removal of chemical oxygen demand (COD). By biodegrading the products of TCH photocatalysis, the biofilms lowered the competition for free radicals between TCH and its photocatalysis products; thus, VPCB accelerated TCH removal by ∼11% in the first 2h of operation, compared with photocatalysis alone. The biofilms in the VPCB carriers evolved to being enriched in Methylibium, Runella, Comamonas, and Pseudomonas, which are known for biodegrading aromatics and being resistant to TCH. In conclusion, VPCB enhanced degradation and mineralization of TCH.

Synthesis of bi-metallic oxides nanotubes for fast removal of dye using adsorption and sonocatalysis process

In this study, ultrasound-assisted synthesis of bi-metallic oxides nanotubes (ZnO–TiO2 NTs) using sol–gel method followed by hydrothermal method is reported. Essentially, an attempt was made to investigate the simultaneous adsorption and sonocatalysis process for fast removal of dye using ZnO–TiO2 NTs. The results of characterization revealed that ZnO–TiO2 NTs were hollow nanotubular structure in shape with tube diameter of ∼10nm and open ended. It has large specific surface area of 336.9m2/g as compared to ZnO (30.5m2/g) and TiO2 (12.3m2/g). The band-gap energy of NTs is 2.95eV which is much lower than the pure ZnO (3.18eV) and TiO2 nanoparticles (3.15eV). Activity of ZnO–TiO2 NTs was assessed using decolorization process as model reaction system involving adsorption and sonocatalysis processes. The results were also compared with their counterparts, viz. ZnO and TiO2. Experimental results revealed that large specific surface area and surface charges on ZnO–TiO2 NTs promote the adsorption efficiency, while the high pore volume helps dye molecules to diffuse rapidly during the sonocatalysis process. Approximately, 97% of decolorization was achieved within 10min of treatment with sonocatalysis process. These experimental results presented in this paper could form a useful tool for further research in degradation of other bio-recalcitrant pollutants using ZnO–TiO2 NTs.

Electrocatalytic reduction of metronidazole using titanocene/Nafion®-modified graphite felt electrode

The main objective of this study was to examine the feasibility of an electrocatalytic reduction on titanocene/Nafion®-modified graphite felt electrode, as pretreatment, before a biological treatment, for the degradation of metronidazole, a nitro biorecalcitrant pollutant. A titanium complex, know as an effective catalyst in the reduction of nitro groups, was immobilized on the electrode surface by encapsulation into a Nafion® film. The different operating conditions used to prepare the modified electrode, i. e. the initial concentrations of catalyst and Nafion® and the sonication time, were optimized and the modification of the electrode was highlighted by cyclic voltammetry and electronic scanning microscopy coupled with energy dispersive spectroscopy analysis. The results show a good stability and reproducibility of the modified electrode. Flow heterogeneous catalytic reduction of metronidazole was then carried out with the titanocene/Nafion®-modified graphite felt as working electrode. The HPLC analysis underlined the total reduction of metronidazole after 1hour and the evolution of the biological oxygen demand to chemical oxygen demand ratio showed a significant increase of biodegradability from 0.06 before pretreatment to 0.35±0.05 after electrolysis on the modified graphite felt electrode. The comparison of both homogeneous and heterogeneous reactions underlined the interest of the immobilization process that led to a higher stability of the catalyst, giving rise to a higher turnover number and an improvement of biodegradability. The stability of the modified electrode was investigated after electrolysis by cyclic voltammetry and successive electrolyses.

Mechanistic analysis of sono-photolysis degradation of carmoisine

The hybrid advanced oxidation process (AOP) of sono-photolysis, in which sonication and photolysis (UV-C/H2O2) are applied simultaneously, is known to give effective degradation of several bio-recalcitrant pollutants. This study has attempted to identify the links and interactions between the mechanisms of individual AOPs of sonolysis and photolysis, when applied simultaneously. Experimental results have been analyzed concurrently with the simulations of cavitation bubble dynamics. It is revealed that oxidizing (OH) radicals generated through photolysis contribute mostly to degradation reactions. Due to highly sporadic nature of transient cavitation, the contribution of sonolysis to degradation is rather subordinate as compared to photolysis. Nonetheless, faster degradation and higher mineralization in sono-photolysis, as compared to photolysis alone, essentially points at supportive role of ultrasound in the hybrid AOP. Addition of electrolytes (or salt) to the reaction mixture during sono-photolysis treatment causes effective partitioning of the pollutant molecules in the interfacial region of transient cavitation bubble, which results in further enhancement of degradation kinetics and mineralization. Although the present study has employed Carmoisine as model pollutant, the mechanistic principles identified in this study, and their manifestations in terms of degradation/mineralization of pollutants are applicable to any other bio-recalcitrant pollutant.

Intensification of Wastewater Treatment using Sono-hybrid Processes: An Overview of Mechanistic Synergism

Sono-hybrid advanced oxidation processes (AOPs) have recently attracted significant attention of researchers for degradation of bio-recalcitrant pollutants. Most widely studied sono-hybrid processes are: sonocatalysis, sono-Fenton and sono-photocatalysis. However, exact synergy between these AOPs and the underlying physical mechanism remains largely unexplored. This paper has addressed this fundamental issue. With approach of coupling experimental results to simulation of cavitation bubble dynamics, an attempt is made to identify synergistic links between individual mechanisms of AOPs. It is revealed that in all sono-hybrid AOPs, physical effect of ultrasound and cavitation (generation of micro-turbulence) contributes more than chemical effect (radical production). In sonocatalysis, the catalyst merely acts as adsorbent, while sono-photocatalysis shock waves produced by transient cavitation bubble have an adverse effect of desorption of pollutant molecules from catalyst surface. The phenomena of radical conservation and scavenging of radicals also play an important role. Externally added H2O2 (as Fenton reagent) scavenges oxidising radicals produced by cavitation, while dissolved oxygen as well as externally added Fe2+ (as Fenton reagent) help either generation of additional oxidising radicals (such as O• and HO2•) or regeneration of •OH radicals through Fenton reaction induced by in-situ produced H2O2 through combination of •OH radicals.

Effect of Fenton oxidation on biodegradability, biotoxicity and dissolved organic matter distribution of concentrated landfill leachate derived from a membrane process

The treatment of concentrated landfill leachate from membrane process is a troublesome issue due to high concentrations of biorecalcitrant pollutants. In this study, the effect of Fenton process on dissolved organic matter (DOM) distribution (i.e. humic acid (HA), fulvic acid (FA) and hydrophilic fraction (HyI)), chemical forms of toxic organic compounds and metals, and their biotoxicity were investigated. In the concentrated leachate, toluene, ethylbenzene and chlorobenzene predominated in the HyI fraction, while phthalate esters (PAEs) were mainly absorbed on the HA and FA fractions. PAEs were more readily removed from the HA and FA fractions than that from the HyI fraction in the Fenton process. The complexing abilities of DOM varied with types of metal in the concentrated leachate. The biotoxicities of the DOM fractions to luminescent bacteria (Photobacterium phosphoreum T3 mutation) were HA>FA>HyI. The biotoxicities of the hydrophobic organic contaminants to luminescent bacteria were not obvious in the concentrated leachate due to their low concentrations. Metals might be the main contributor to the biotoxicity to luminous bacteria in the concentrated leachate. These results indicated that Fenton process could influence the pollutants distribution in DOM and their biotoxicities through the breakdown of HA and FA in the concentrated leachate.

Combined chemical oxidation and biological processes for herbicide degradation

AbstractBACKGROUNDFenton and photo‐Fenton processes were explored as photochemical pre‐treatments to improve the biodegradability of wastewater containing atrazine, a commercial pesticide. The effects of H2O2, Fe3+ and irradiation level on the degradation processes were studied and the optimal conditions determined.RESULTSFenton and photo‐Fenton oxidation systems were able to remove 85 and 100% of atrazine, respectively, in a 120 min period. These processes produced a biocompatible solution, removing 100% of the initial biorecalcitrant compound; however, cyanuric acid remained in the effluent after the chemical oxidation treatment due to the stability of the N‐heterocyclic ring of this acid. Nevertheless, it was found that the cyanuric acid remaining from the photo‐oxidative process can be removed by means of an anaerobic treatment.CONCLUSIONSThe results obtained in this work indicate that a coupled photo‐Fenton–biological treatment system is a feasible method to achieve the complete mineralization of biorecalcitrant pollutants such as atrazine. © 2015 Society of Chemical Industry

Efficient Degradation of a Biorecalcitrant Pollutant from Wastewater Using a Fluidized Catalyst-Bed Reactor

This study investigated the treatment of an azo dye, as a biorecalcitrant model, from industrial wastewater by using Cu/Mg/Al-chitosan in a fluidized catalyst-bed reactor. A number of variables were used to study the impact they had on the oxidation process involving azo dye. The maximum degradation of the azo dye was achieved at 7 g Cu/Mg/Al-chitosan. The chloride and sulfate ions had a synergistic effect on azo dye removal. The oxidation of the azo dye under the selected conditions was of pseudo-first-order. Textile wastewater could effectively be treated using a low concentration of about 7 g of Cu/Mg/Al-chitosan in a short hydraulic retention time of 10 min. The use of Cu/Mg/Al-chitosan demonstrated a promising method to eliminate the azo dye from the wastewater.

Treatment of biorecalcitrant α-methylphenylglycine aqueous solutions with a solar photo-Fenton-aerobic biological coupling: Biodegradability and environmental impact assessment

The photo-Fenton process under solar irradiation (SPF) was coupled to an aerobic activated sludge biological treatment carried out in a sequencing batch reactor (SBR). The effectiveness of the coupling for the treatment of aqueous solutions polluted with non-biodegradable α-methyl-phenylglycine (α-MPG) was evaluated. Respirometry was chosen as alternative to other conventional tests (BOD5/COD, Zahn-Wellens, Microtox®) for the quantification of both biodegradability and toxic/inhibitory effect of the polluted water along the SPF time, the final goal being the determination of the suitable reaction time for chemical–biological coupling. The nitrification of the aqueous solution during the biological treatment, a process that might take place at the same time than the oxidation of organic matter and endogenous respiration, was evaluated along the different SBR cycles. Finally, a comparative life cycle assessment (LCA) of SPF and an integrated chemical–biological coupling (SPF–SBR) was carried out in order to identify the best alternative, from an environmental point of view, for the treatment of biorecalcitrant pollutants. The determination of the main impact factors of the biological treatment was also carried out. The results of the bench-scale study indicate that both the SPF and SPF–SBR treatments are environmentally friendly and effective alternative strategies for the treatment of water loaded with non-biodegradable compounds.

Photocatalytic degradation of indole in UV/TiO2: optimization and modelling using the response surface methodology (RSM)

The aim of our research is to apply experimental design methodology to the optimization of photocatalytic degradation of indole present in wastewater. Heterogeneous photocatalysis for the oxidation of organic biorecalcitrant pollutants in water is an environmental promising method. We used the response surface methodology (RSM) for the modelization and optimization of the photodegradation of indole in the presence of titanium dioxide. The effect of indole concentration, UV intensity and stirring speed on the yield of indole degradation was determined. According to the mathematic optimization of the process, the optimum point when 100% of degradation is achieved is given by the following values: UV intensity = 250 W/m2, stirring speed = 536.36 tr/min and initial indole concentration = 10.10 mg/l.

New helio-photocatalytic–photovoltaic hybrid system for simultaneous water decontamination and solar energy conversion

Test results for a designed and installed hybrid photocatalytic–photovoltaic system (HPPS) are presented in this paper. The HPPS consists of one device with dual functions: The photocatalytic system uses UV radiation to promote degradation of organic pollutants, and beside it absorbs the IR radiation. The photovoltaic (PV) system converts the visible radiation into electricity, which can either be used directly by the recirculation pump or stored in a battery for other purposes. The suggested design aims to achieve an autonomous, environmentally friendly method for the treatment of biorecalcitrant pollutants. Two prototypes were erected: HPPS P , using Plexiglas and HPPS G using commercial glass. Both were tested outdoors to determine their impact on photovoltaic power production. Test results showed that PV power diminished to 14% and 22% for HPPS G and HPPS P respectively, compared to a PV panel alone.

An innovative coupled solar-biological system at field pilot scale for the treatment of biorecalcitrant pollutants

An overview of recent works (1998–2002) coupling Advanced Oxidation Process (AOP) and Biological systems for wastewater treatment confirms the beneficial effects of such two-steps treatment at lab scale. In this paper, an innovative coupled solar-biological system at field pilot scale was designed, builds, and experimental results are presented. The strategy to develop this system implicates the choice of the most appropriate solar collector and the most efficient AOP, the optimization of this AOP, the choice of the biological oxidation system, the monitoring of the chemical and biological characteristics of photo-treated solutions and the evaluation of the performances of the coupled solar-biological flow system. The coupled system is conformed by a Compound Parabolic Solar Collector (CPC) and a Fixed Bed Reactor (FBR). The photo-Fenton system was the most appropriate AOP for the degradation of a model biorecalcitrant compound, 5-amino-6-methyl-2-benzimidazolone (AMBI). Surface Response Methodology was used to optimize the Fe 3+ and H 2O 2 concentration. The coupled reactor, operates in semicontinuous mode, has shown to reach a whole mineralization performance between 80 and 90% in the range of initial dissolved organic carbon (DOC) concentration of 300–500 mg C l −1. These results indicate that coupling solar-biological processes at pilot scale is a plausible effective approach for the treatment of real industrial wastewaters.

Recent developments in the coupling of photoassisted and aerobic biological processes for the treatment of biorecalcitrant compounds

A general strategy to develop combined photochemical and biological system for biorecalcitrant wastewater treatment is proposed. For the development of this strategy, the following points were taken into account: the biodegradability of initial solutions, the operation mode of the coupled reactor, the chemical and biological characteristics of the phototreated solutions, the evaluation of different photoassisted advanced oxidation processes, the optimal conditions of both photochemical and biological processes, and the efficiency of the coupled reactor. The strategy to couple photochemical and biological processes is illustrated by case studies of four different biorecalcitrant pollutants. Three kinds of combined systems were developed using either photo-Fenton, Fe 3+/UV, or TiO 2 supported on glass rings for the photocatalytic pretreatment and in all cases immobilized biomass for the biological step. The advantages of the each coupled system are discussed and beneficial effects of such two-step treatments were found. However this strategy is not a universal solution. Chemical, biological, and kinetic studies must be always carried out to ensure that the photochemical pretreatment increase the biocompatibility of the treated wastewater. Some field experiments using solar reactor indicated that a coupled photochemical–biological treatment system at pilot scale is a possible way to achieve the complete mineralization of the biorecalcitrant pollutants.

Degradation of a biorecalcitrant dye precursor present in industrial wastewaters by a new integrated iron(III) photoassisted–biological treatment

This study focuses on the mineralization of 5-amino-6-methyl-2-benzimidazolone (AMBI), an important precursor in the industrial production of dyes, through an integrated Fe(III) photoassisted–biological system without addition of other electron acceptor than O2. The iron photoassisted process produces a biocompatible solution, removing 100% of the initial biorecalcitrant compound and 40% of the Dissolved Organic Carbon (DOC), and then the complete mineralization was achieved in the biological treatment. The transformation of AMBI photoinduced by only Fe(III) is mainly attributed to three simultaneous process: direct photolysis of the [Fe3+–AMBI] complex, the attack of the complex by OH radicals generated by the photolysis of Fe(OH)2+, and by the attack of supplementary OH radicals generated by the Fenton and photo-Fenton like reactions, which are induced by the H2O2 that have been formed “in situ”. The following topics are also studied in this paper: (a) the UV-Vis spectroscopic characterization of Fe(III), AMBI, and its mixture in aqueous solution, (b) the involvement of OH radicals and oxygen in the photodegradation of AMBI, (c) the comparison between O2 and H2O2 as electron acceptors in the iron photoassisted pretreatment, and their performances as a pretreatment step in the coupled photochemical biological reactor. Some field experiments under direct solar radiation were carried out using a compound parabolic collector (CPC) erected at the Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland. The obtained results indicate that a coupled solar–biological treatment system at pilot scale is a possible way to achieve the complete mineralization of biorecalcitrant pollutants.