The impact of material design on the photocatalytic removal efficiency and toxicity of two textile dyes.

This study deals with the toxicity of the treated solutions of two types of dyes, namely, the anthraquinonic Reactive Bleu 19 dye (RB19) and the bi-azoic Direct Red 227 dye (DR227), which are treated in single and binary mixture systems. The target molecules were removed by the photocatalysis process using ZnO as a catalyst, which was calcined at two temperatures 250 and 420 °C (ZnO250 and ZnO420) prepared in the lab by the one-step calcination method. XRD, TEM, EDX, XPS, FT-IR, BET, RAMAN, and EPR analyses were carried out to characterize the catalyst material. While the phytotoxicity was being conducted using watercress seeds, the cytotoxicity took place using a cell line (raw) and an intestinal cell (caco-2). The XRD analysis showed the partial calcination of ZnO250 and the presence of anhydrous zinc acetate along with the ZnO nanoparticles (NPs). This result was not observed for ZnO420. Despite the complete discoloration (100%) of all the final solutions, ZnO250 exhibited a high cytotoxicity and phytotoxicity against the RB19 dye after the photocatalytic treatment; however, it was not the case of ZnO420 which was selected as an eco-friendly photocatalyst for the degradation of organic dyes based on the results of removal efficiency, cytotoxicity, and phytotoxicity.

A novel system coupling an electro-Fenton process and an advanced biological process to remove a pharmaceutical compound, metronidazole.

The objective of this study was to improve the mineralization of metronidazole, a recalcitrant antibiotic by the development of a new combined process coupling electro-Fenton and a biological process. For biotreatment, various strategies were considered bioaugmentation, bioacclimatation and biostimulation alone or combined. So, the novelty of this strategy is to combine advanced oxidation process with advanced biological process. The conventional biotreatment with activated sludge after 120 h of culture, led to 58.1% mineralization, whereas the pure isolated strains, from activated sludge culture in the presence of metronidazole by-products, identified as Pseudomonas putida (strain A) and Achromobacter sp. (strain B), led to 37.2% and 40.1% respectively. After original acclimation of the isolated strains to electrolysis by-products, the mineralization levels reached 75.6% and 72.9% for strains A and B respectively after 120 h of culture. The results showed that the mineralization of metronidazole by-products was the most important in the case of the combination of autochthonous bioaugmentation and biostimulation, with 96.1% after 120 h of treatment. By coupling the two processes, the global treatment reached therefore a mineralization yield of 97% with a reduction in processing time of 16 days compared to previous conventional biological treatment.

A New Approach to Produce Succinic Acid Through a Co-Culture System.

Microorganisms can produce a wide range of bio-based chemicals that can be used in various industrial applications as molecules of interest. In the present work, an analysis of the power production by pure culture, co-culture, and sequential culture was performed. In this study, both the mono-culture and the co-culture strategies of Actinobacillus succinogenes with Saccharomyces cerevisiae as carbon sources to produce succinic acid using glucose and fructose were examined. The cultures were performed in batch mode and a great attention was paid to the co-culture system to improve the biosynthetic pathway between A. succinogenes and S. cerevisiae by combining these two strains in a single fermentation process. Under microaerobic and anaerobic conditions, the process was characterized in terms of sugars concentration, cell density, metabolites, yield (mol-C products/ mol-C sugars), the temperature conditions for productivity, and pH. The results showed that the process could consume glucose and fructose and could adapt to different concentrations of the two sugars more quickly than by a single organism and the best results were obtained in a sequential co-culture recording 0.27 mol L-1 of succinic acid concentration and a volumetric productivity of 0.3 g L-1 h-1. Under the investigated operating conditions, the combination of these two strains in a single reactor produced a significant amount of succinic acid (0.70 mol-C SA/mol-C substrates). A simultaneous and sequential co-culture strategy can be a powerful new approach in the field of bio-based chemical production.

Photocatalytic Performance of CuxO/TiO2 Deposited by HiPIMS on Polyester under Visible Light LEDs: Oxidants, Ions Effect, and Reactive Oxygen Species Investigation.

In the present study, we propose a new photocatalytic interface prepared by high-power impulse magnetron sputtering (HiPIMS), and investigated for the degradation of Reactive Green 12 (RG12) as target contaminant under visible light light-emitting diodes (LEDs) illumination. The CuxO/TiO2 nanoparticulate photocatalyst was sequentially sputtered on polyester (PES). The photocatalyst formulation was optimized by investigating the effect of different parameters such as the sputtering time of CuxO, the applied current, and the deposition mode (direct current magnetron sputtering, DCMS or HiPIMS). The results showed that the fastest RG12 degradation was obtained on CuxO/TiO2 sample prepared at 40 A in HiPIMS mode. The better discoloration efficiency of 53.4% within 360 min was found in 4 mg/L of RG12 initial concentration and 0.05% Cuwt/PESwt as determined by X-ray fluorescence. All the prepared samples contained a TiO2 under-layer with 0.02% Tiwt/PESwt. By transmission electron microscopy (TEM), both layers were seen uniformly distributed on the PES fibers. The effect of the surface area to volume (dye volume) ratio (SA/V) on the photocatalytic efficiency was also investigated for the discoloration of 4 mg/L RG12. The effect of the presence of different chemicals (scavengers, oxidant or mineral pollution or salts) in the photocatalytic medium was studied. The optimization of the amount of added hydrogen peroxide (H2O2) and potassium persulfate (K2S2O8) was also investigated in detail. Both, H2O2 and K2S2O8 drastically affected the discoloration efficiency up to 7 and 6 times in reaction rate constants, respectively. Nevertheless, the presence of Cu (metallic nanoparticles) and NaCl salt inhibited the reaction rate of RG12 discoloration by about 4 and 2 times, respectively. Moreover, the systematic study of reactive oxygen species' (ROS) contribution was also explored with the help of iso-propanol, methanol, and potassium dichromate as •OH radicals, holes (h⁺), and superoxide ion-scavengers, respectively. Scavenging results showed that O2- played a primary role in RG12 removal; however, •OH radicals' and photo-generated holes' (h⁺) contributions were minimal. The CuxO/TiO2 photocatalyst was found to have a good reusability and stability up to 21 cycles. Ions' release was quantified by means of inductively coupled plasma mass spectrometry (ICP-MS) showing low Cu-ions' release.

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.

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.

Identification of strain isolated from dates (Phœnix dactylifera L.) for enhancing very high gravity ethanol production.

Ethanol production from by-products of dates in very high gravity was conducted in batch fermentation using two yeasts, Saccharomyces cerevisiae and Zygosaccharomyces rouxii, as well as a native strain: an osmophilic strain of bacteria which was isolated for the first time from the juice of dates (Phoenix dactylifera L.). The phylogenetic analysis based on the 16S ribosomal RNA and gyrB sequence and physiological analysis indicated that the strain identified belongs to the genus of Bacillus, B. amyloliquefaciens. The ethanol yields produced from the syrup of dates (175 g L-1 and 360 g L-1 of total sugar) were 40.6% and 29.5%, respectively. By comparing the ethanol production by the isolated bacteria to that obtained using Z. rouxii and S. cerevisiae, it can be concluded that B. amyloliquefaciens was suitable for ethanol production from the syrup of dates and can consume the three types of sugar (glucose, fructose, and sucrose). Using Z. rouxii, fructose was preferentially consumed, while glucose was consumed only after fructose depletion. From this, B. amyloliquefaciens was promising for the bioethanol industry. In addition, this latter showed a good tolerance for high sugar concentration (36%), allowing ethanol production in batch fermentation at pH 5.0 and 28 °C in date syrup medium. Promising ethanol yield produced to sugar consumed were observed for the two osmotolerant microorganisms, Z. rouxii and B. amyloliquefaciens, nearly 32-33%, which were further improved when they were cocultivated, leading to an ethanol to glucose yield of 42-43%.

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.

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.

Electro-Fenton pretreatment for the improvement of tylosin biodegradability.

The feasibility of an electro-Fenton process to treat tylosin (TYL), a non-biodegradable antibiotic, was examined in a discontinuous electrochemical cell with divided cathodic and anodic compartments. Only 15 min electrolysis was needed for total tylosin degradation using a carbon felt cathode and a platinum anode; while 6 h electrolysis was needed to achieve high oxidation and mineralization yields, 96 and 88 % respectively. Biodegradability improvement was shown since BOD5/COD increased from 0 initially to 0.6 after 6 h electrolysis (for 100 mg L(-1) initial TYL). With the aim of combining electro-Fenton with a biological treatment, an oxidation time in the range 2 to 4 h has been however considered. Results of AOS (average oxidation state) and COD/TOC suggested that the pretreatment could be stopped after 2 h rather than 4 h; while in the same time, the increase of biodegradability between 2 and 4 h suggested that this latter duration seemed more appropriate. In order to conclude, biological cultures have been therefore carried out for various electrolysis times. TYL solutions electrolyzed during 2 and 4 h were then treated with activated sludge during 25 days, showing 57 and 67% total organic carbon (TOC) removal, respectively, namely 77 and 88% overall TOC removal if both processes were considered. Activated sludge cultures appeared, therefore, in agreement with the assessment made from the analysis of physico-chemical parameters (AOS and COD/TOC), since the gain in terms of mineralization expected from increasing electrolysis duration appeared too low to balance the additional energy consumption.

Treatment process and toxicities assessment of wastewater issued from anaerobic digestion of household wastes.

Modern society grapples with large amounts of household waste. The anaerobic digestion of this waste offers a promising source for energy-rich biogas production but generates high toxic effluents that require treatment before reuse or disposal into the environment. This study aimed to investigate three techniques, namely coagulation/flocculation, electro-coagulation, and activated sludge, in terms of efficiency in the treatment of these effluents. It also aimed to assess their toxicity effects on the germination and growth of durum wheat Triticum aestivum L. seeds before and after 6 days of treatment. Activated sludge was most efficient in reducing chemical oxygen demand, turbidity, and conductivity (95.7 %, 15.8 %, and 37.5 %, respectively). The effluent treated with this technique induced a marked delay in germination (low mean time of germination) and a significant reduction in the percentages of seed germination and root and leaf growths. It was also noted to strongly induce lipid peroxidation in roots and leaves, which presumably explained the germination/growth inhibition of the wheat seeds. The effluent also induced marked lipid peroxidation effects and strongly inhibited the activities of butyrylcholinesterase in mice bone marrows. The effluent shows a high ability to inhibit the growth of three microalgae; these endpoints are useful tools to biomonitor the physico-chemical quality of this wastewater. Overall, while no significant alterations were observed in terms of animal and vegetable toxicities when the effluent was treated by coagulation/flocculation, activated sludge treatment proved efficient in reducing the toxicities induced by the untreated effluents. The results indicate that the application of this technique is promising with regards to attaining efficient, eco-friendly, and cost-effective strategies for the management and treatment of household waste.

Biodegradation by bioaugmentation of dairy wastewater by fungal consortium on a bioreactor lab-scale and on a pilot-scale.

A fungal consortium including Aspergillus niger, Mucor hiemalis and Galactomyces geotrichum was tested for the treatment of dairy wastewater. The bio-augmentation method was tested at lab-scale (4 L), at pilot scale (110 L) and at an industrial scale in Wastewater Treatment Plants (WWTP). The positive impact of fungal addition was confirmed when fungi was beforehand accelerated by pre-culture on whey (5 g/L lactose) or on the dairy effluent. Indeed, chemical oxygen demand (COD) removal yields increased from 55% to 75% for model medium, diluted milk. While after inoculation of an industrial biological tank from a dairy factory with the fungal consortium accelerated by pre-cultivation in a 1000 L pilot plant, the outlet COD values decreased from values above the standard one (100 mg/L) to values in the range of 50-70 mg/L. In addition, there was a clear impact of fungal addition on the 'hard' or non-biodegradable COD owing to the significant reduction of the increase of the COD on BOD5 ratio between the inlet and the outlet of the biological tank of WWTP. It was in the range of 451%-1111% before adding fungal consortium, and in the range of 257%-153% after bio-augmentation with fungi. An inoculated bioreactor with fungal consortium was developed at lab-scale and demonstrated successfully at pilot scale in