Hayet Djelal

Potential of newly isolated wild Streptomyces strains as agents for the biodegradation of a recalcitrant pharmaceutical, carbamazepine

Carbamazepine (CBZ) is a recalcitrant xenobiotic pharmaceutical pollutant highly stable in soil and wastewater during treatment. The biodegradation of CBZ using streptomycetes has been few studied up to now. Sixteen newly filamentous bacteria belong to genus Streptomyces spp. isolated from different Romanian soil samples and three strains from a collection of microorganisms (MIUG) were morphologically characterized, tested based on their resistance against CBZ toxicity and then selected as agents for bioremediation. Five Streptomyces spp. strains coded MIUG 4.88, MIUG 4.89, SNA, LP1 and LP2 showed CBZ tolerance at all of the tested concentrations, i.e. 0.05, 0.2, 1, 5 and 8 mg L−1. Two of these (MIUG 4.89 and SNA strains) were selected based on their resistance to target compound and were then assessed for CBZ biodegradation. The strain Streptomyces MIUG 4.89 showed an interesting efficiency for CBZ removal, with a yield of 35% when it was cultivated in submerged conditions on a minimal medium supplemented with 5 g L−1 glucose. This ability was linked to extracellular laccase production. These results are promising for the use of these filamentous bacteria as bioremediation agents.

Photocatalytic Reactors Dedicated to the Degradation of Hazardous Organic Pollutants: Kinetics, Mechanistic Aspects, and Design – A Review

In recent years, heterogeneous photocatalysis has emerged as a new effective, powerful, clean, and safe decontamination technology for the treatment of organic pollutants and the transformation of hazardous chemicals into different forms. This review focuses on the recent development of various conventional technologies of reactors designated for the photodegradation of hazardous organic pollutants with their limitations. This phenomenon is strongly influenced by reaction conditions such as temperature of reaction, pH, light intensity and wavelength, pollutant concentration, photocatalyst quantity, relative humidity (RH), and other parameters. The catalyst photoactivity depends on the structural characteristics of the semiconductor, its morphology, and its particles size. This paper presents the progression of photocatalytic reactors for synthetic dyes degradation with special consideration to the use of supported photocatalyst and nanostructured titanium supported over volcanic ashes, owing to the major advantage of an easy separation of the catalyst when compared to homogenous system, namely suspended catalyst. In addition, special attention was paid to the literature dealing with the promotion of light efficiency by testing various light sources.

Electrocoagulation and electro-oxidation treatment for the leachate of oil-drilling mud

The pollution caused by discharges of oil drilling is now a source of environmental degradation and raises currently a particular interest. We propose in this work the application of electrocoagulation (EC) and electro-oxidation (EO) treatment for the leachate of these drilling muds. The effect of pH, current density, the electrolysis time, and the amount electrolytic added were studied, and the effectiveness of the processes is evaluated by measuring the chemical oxygen demand (COD). The dissolution is the best way to mobilize pollutants from drilling mud so we conducted leaching before starting the electrochemical treatment. The processes were carried out in batch mode using a stainless steel anode and ruthenium cathode for the EO and aluminum electrodes materials for the EC. The preliminary results clearly demonstrate the compatibility of the two techniques used with the type of pollution studied. In fact, the EC allowed the COD removal of about 95% and a rebate rates above 78% for EO.

Combination of Electro-Coagulation and biological treatment by bioaugmentation for landfill leachate

AbstractThis study examines the use of the coupling of electro-coagulation (EC) and biological treatment of mature landfill leachate from a non-hazardous waste storage characterized by a relatively low Chemical oxygen demand (COD) and a low BOD5/COD with a low biodegradability and a high level of inorganic compound such as . During electro-coagulation treatment, a decrease in the chemical oxygen demand (COD) was shown with an increase in the current density. A toal of 33 and 56% COD removal were respectively obtained with 23 and 95 A m−2. However, nothing was observed concerning the removal of ammonium. Nevertheless, biological treatment with or without addition of activated sludge (AS) has allowed the decrease in ammonium with a yield of 62% after 166 h. However, with the addition of activated sludge, the efficiency of nitrification is increased by 10%. As the bioaugmentation with AS has not improved the removal of organic matters and that the electrochemical treatment is not appropriate for removing NH4...

Reactive oxygen and iron species monitoring to investigate the electro-Fenton performances. Impact of the electrochemical process on the biodegradability of metronidazole and its by-products

In this study, the monitoring of reactive oxygen species and the regeneration of the ferrous ions catalyst were performed during electro-Fenton (EF) process to highlight the influence of operating parameters. The removal of metronidazole (MTZ) was implemented in an electrochemical mono-compartment batch reactor under various ranges of current densities, initial MTZ and ferrous ions concentrations, and pH values. It was found that under 0.07 mA cm-2, 0.1 mM of ferrous ions and pH = 3, the efficiency of 100 mg L-1 MTZ degradation and mineralization were 100% within 20 min and 40% within 135 min of electrolysis, respectively. The highest hydrogen peroxide and hydroxyl radical concentrations, 1.4 mM and 2.28 mM respectively, were obtained at 60 min electrolysis at 0.07 mA cm-2. Improvement of the biodegradability was reached from 60 min of electrolysis with a BOD5/COD ratio above 0.4, which was reinforced by a respirometric study, that supports the feasibility of coupling electro-Fenton and biological treatment for the metronidazole removal.

Cytotoxic effect of chlorpyrifos ethyl and its degradation derivatives by Pseudomonas peli strain isolated from the Oued Hamdoun River (Tunisia)

A bacterium was isolated from the river of Oued Hamdoun (Tunisia), and its phenotypic features, physiological and chemotaxonomic characteristics and phylogenetic analysis of 16S ribosomal RNA sequence revealed it as Pseudomonas peli (P. peli). Chlorpyrifos ethyl (CP) was used as the sole source of carbon and energy by P. peli, and it was cometabolised in the presence of glucose. CP was completely degraded by P. peli after 96 h of shake incubation. High-performance liquid chromatography analysis indicated that the biodegradation kinetics was not affected by the addition of glucose into the culture medium. In the present study, only transient accumulation of one major no-identified product was observed after 48 h of incubation, with no other persistent metabolites detected. Cytotoxicity of CP, before and after biodegradation with P. peli, was evaluated in vitro using the MTT-colorimetric assay against three human cancer cell lines (A549, lung cell carcinoma, HT29, colon adenocarcinoma and MCF7, breast adenocarcinoma). CP reduced viability of all human cell lines in a dose-dependent manner. Its activity was very remarkable against A549 cell line. However, cytotoxicity strongly decreased in CP obtained after incubation with P. peli. Hence, we conclude that when incubated under appropriate conditions, P. peli has a metabolism that completely detoxifies CP.

Impact of an osmotic stress on the intracellular volume of Hansenula anomala

The effect of an osmotic stress resulting from high glucose or NaCl concentrations on the morphology and intracellular volume of Hansenula anomala was examined by scanning electronic microscopy and changes in the intracellular volume accessible to tritiated water, respectively. No noticeable change in the cell morphology was observed, with the cells remaining ellipsoidal. An increase in the contribution of compatible solutes, such as arabitol, glycerol and trehalose, to the cell volume, was not sufficient to counterbalance the decrease in the volume accessible to tritiated water for increasing water stress, leading to a decrease in cell volume. For a given morphology, a decrease in the cell volume allowed the cell to maximize the surface to ratio volume for a better distribution of the external osmotic pressure. It also allowed maximization of the compatible solute concentration (for a given amount of accumulated compounds), leading to an increase in the internal osmotic potential to counterbalance the osmotic potential of the surrounding medium. However, the accumulation of compatible solutes in the cell did not allow any adjustment of the osmotic potential of cells in high-osmolarity medium, especially in the case of NaCl as the osmoticum, thereby confirming the higher stress effect of salt relative to glucose.

Metronidazole removal by means of a combined system coupling an electro-Fenton process and a conventional biological treatment: By-products monitoring and performance enhancement

In order to mineralize Metronidazole (MTZ), a process coupling an electro-Fenton pretreatment and a biological degradation was implemented. A mono-compartment batch reactor containing a carbon-felt cathode and a platinum anode was employed to carry out the electro-Fenton pretreatment of MTZ. A total degradation of MTZ (100 mg L-1) was observed at 0.07 mA.cm-2 after only 20 min of electrolysis. Yet, after 1 and 2 h of electrolysis, the mineralization level remained low (16.2% and 32% respectively), guaranteeing a significant residual organic content for further biological treatment. LCMS/MS was used to determine the intermediates by-products and hence to propose a plausible degradation pathway. An increase from 0 to 0.44 and 0.6 for 1 and 2 h of electrolysis was observed for the BOD5/COD ratio. Thus, from 1 h of electro-Fenton pretreatment, the electrolysis by-products were considered biodegradable. A biological treatment of the electrolysis by-products after 1 and 2 h was then realized. The mineralization yields reached very close values, about 84% for 1 and 2 h of electrolysis after 504 h of biological treatment, namely close to 89% for the overall process, showing the pertinence of the proposed coupled process.

Biohydrogen production by coupling an electrochemical system with a biological treatment

The main objective of this work was to examine the feasibility of biohydrogen production using ammonium solution resulting from nitrate electrochemical reduction. In this coupled process a concentrated nitrate solution of 3g NO₃^-L^-1 was firstly converted to ammonium using a home-made electrochemical flow cell, leading to 97% ammonium selectivity. This solution was then used as a nitrogen source to produce H₂ in a batch system involving heat-treated aerobic activated sludge. Under proved optimal conditions, pH 5.5 and 15g L^-1 initial glucose concentration a hydrogen yield of 0.35 mol H₂/mol glucose was obtained, with total consumption of the produced ammonium. The obtained biogas contains only H₂ and CO₂ and was free of methane, hydrogen sulphide (H₂S) and nitrous oxide (N₂O).