Assessment of the individual and mixture toxicity of cadmium,copper and oxytetracycline,on the embryo-larval development of the sea urchin <Emphasis Type="Italic">Paracentrotus lividus</Emphasis>

Multiple pollutions by trace metals and pharmaceuticals have become one of the most important problems in marine coastal areas because of its excessive toxicity on organisms living in this area. This study aimed to assess the individual and mixture toxicity of Cu, Cd, and oxytetracycline frequently existing in the contaminated marine areas and the embryo-larval development of the sea urchin Paracentrotus lividus. The individual contamination of the spermatozoid for 1 h with the increasing concentrations of Cd, Cu, and OTC decreases the fertility rate and increases larvae anomalies in the order Cu > Cd > OTC. Moreover, the normal larva frequency and the length of spicules were more sensitive than the fertilization rate and normal gastrula frequency endpoints. The mixture toxicity assessed by multiple experimental designs showed clearly that concentrations of Cd, Cu, and OTC superior to 338 μg/L, 0.56 μg/L, and 0.83 mg/L, respectively, cause significant larva malformations.     

Decolorization and detoxification of two textile industry effluents by the laccase/1-hydroxybenzotriazole system

The aim of this work was to determine the optimal conditions for the decolorization and the detoxification of two effluents from a textile industry—effluent A (the reactive dye bath Bezactive) and effluent B (the direct dye bath Tubantin)—using a laccase mediator system. Response surface methodology (RSM) was applied to optimize textile effluents decolorization. A Box–Behnken design using RSM with the four variables pH, effluent concentration, 1-hydroxybenzotriazole (HBT) concentration, and enzyme (laccase) concentration was used to determine correlations between the effects of these variables on the decolorization of the two effluents. The optimum conditions for pH and concentrations of HBT, effluent and laccase were 5, 1 mM, 50 % and 0.6 U/ml, respectively, for maximum decolorization of effluent A (68 %). For effluent B, optima were 4, 1 mM, 75 %, and 0.6 U/ml, respectively, for maximum decolorization of approximately 88 %. Both effluents were treated at 30 °C for 20 h. A quadratic model was obtained for each decolorization through this design. The experimental and predicted values were in good agreement and both models were highly significant. In addition, the toxicity of the two effluents was determined before and after laccase treatment using Saccharomyces cerevisiae, Bacillus cereus, and germination of tomato seeds.     

Remazol Brilliant Blue R decolourization by the laccase from Trametes trogii

The decolourization of the recalcitrant dye RBBR by the culture filtrate of Trametes trogii and its isolated laccase was investigated. Both filtrates from Cu-induced cultures as well as purified laccase decolourized the dye RBBR. The purified laccase decolourized the dye down to 97% of 100 mg l(-1) initial concentration of RBBR when only 0.2U ml(-1) of laccase was used in the reaction mixture. The effects of different physicochemical parameters were tested and optimal decolourization rates occurred at pH 5 and at a temperature of 50 degrees C. Decolourization of RBBR occurred in the presence of metal ions which could be found in textile industry effluents. Of all the metal ions tested, FeCl2 was the most inhibiting for the decolourization. HBT was shown to have no effect on the decolourization of RBBR at low concentration, while at a concentration of 5 mM it slightly inhibited decolourization. The presence of aromatic compounds was found to be inhibiting for the decolourization at a concentration of 10 mM, but not at 0.1 mM, while at 1 mM only ortho-diphenols were inhibiting. Probing the effect of methanol it was found that higher concentrations caused a decrease in the decolourization rate of RBBR. The effect of laccase inhibitors on the decolourization of RBBR was tested with L-cysteine, SDS and EDTA. It was demonstrated that L-cysteine was the most inhibiting substrate for the decolourization while SDS was only inhibiting at 10 mM concentration and ETDA was not inhibiting at all tested concentrations.     

Xenobiotics removal by adsorption in the context of tertiary treatment: a mini review

Many xenobiotics, including several pharmaceuticals and pesticides, are poorly treated in domestic wastewater treatment plants. Adsorption processes, such as with activated carbons, could be a solution to curb their discharge into the aquatic environment. As adsorbent-like activated carbon is known to be expensive, identifying promising alternative adsorbent materials is a key challenge for efficient yet affordable xenobiotic removal from wastewaters. As part of the effort to address this challenge, we surveyed the literature on pharmaceutical and pesticide xenobiotics and built a database compiling data from 38 scientific publications covering 65 xenobiotics and 58 materials. Special focus was given to the relevance and comparability of the data to the characteristics of the adsorbent materials used and to the operating conditions of the batch tests inventoried. This paper gives an in-depth overview of the adsorption capacities of various adsorbents. The little data on alternative adsorbent materials, especially for the adsorption of pharmaceuticals, makes it difficult to single out any one activated carbon alternative capable of adsorbing pesticides and pharmaceuticals at the tertiary stage of treatment. There is a pressing need for further lab-scale experiments to investigate the tertiary treatment of discharged effluents. We conclude with recommendations on how future data should best be used and interpreted.     

Evaluation of micro- and nano-carbon-based adsorbents for the removal of phenol from aqueous solutions

This work reports on the adsorption efficiency of two classes of adsorbents: nano-adsorbents including carbon nanotubes (CNTs) and carbon nanofibers (CNFs); and micro-adsorbents including activated carbon (AC) and fly ash (FA). The materials were characterized by thermogravimetric analysis, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area, zeta potential, field emission scanning electron microscopy, and UV spectroscopy. The adsorption experimental conditions such as pH of the solution, agitation speed, contact time, initial concentration of phenol, and adsorbent dosage were optimized for their influence on the phenol. The removal efficiency of the studied adsorbents has the following order: AC > CNTs > FA > CNFs. The capacity obtained from Langmuir isotherm was found to be 1.348, 1.098, 1.007, and 0.842 mg/g of AC, CNTs, FA, and CNFs, respectively, at 2 hours of contact time, pH 7, an adsorbent dosage of 50 mg, and a speed of 150 rpm. The higher adsorption of phenol on AC can be attributed to its high surface area and its dispersion in water. The optimum values of these variables for maximum removal of phenol were also determined. The experimental data were fitted well to Langmuir than Freundlich isotherm models.     

Radioactive Contamination Control by Atmospheric Dispersion Assessment of Airborne Indicator Contaminants: Numerical Model Validation

In this work, a numerical model is proposed to estimate air concentration of released airborne radioactive contaminants ¹³¹I and ¹³⁷Cs. A Gaussian dispersion model is used to assess the atmospheric dispersion of radioactive contaminants released continuously from a nuclear power plant as a result of an accident. The model uses various input parameters such as source height, release rate, stability class, wind speed, and wind direction. The validation of the model was carried out by comparing its predicted values with published experimental data. The model was extensively tested by simulating several accidental situations. The main conclusion drawn from these tests is that for large downwind distances from the release point, the contaminant concentrations predicted by the model diverge drastically from measured data, while for short distances, the predicted values generally agree quite well with experimental data. The obtained activity concentrations range from 1.57?×?10² to 6.43?×?10³ Bq/m³ for ¹³¹I and from 3.18?×?10^?2 to 9.72?×?10² Bq/m³ for ¹³⁷Cs. The estimated standard deviation coefficients values range of 7.2 to 6847.7 m, and the maximum absolute error predicted by the model for these parameters was less than 5%.     

Effects of 5-year application of municipal solid waste compost on the distribution and mobility of heavy metals in a Tunisian calcareous soil

It is obvious that the application of solid waste compost improves the soil fertility. These wastes, however, may also have some negative effects on the agricultural environment due to their metal content. This research aimed at evaluating the influence of Tunisian municipal solid waste compost and farmyard manure on some chemical properties and the distribution of heavy metals in a calcareous Tunisian soil (clayey–loamy soil). A field plot experiment, without vegetation, was installed since 1999 at the experimental farm of the Agronomic National Institute of Tunis (INAT) in the region of Mornag (20 km south of Tunis, Tunisia). During 5 years, the field received yearly the following treatments: 0, 40, 80 and 120 t/ha of municipal solid waste compost and 0, 40 and 120 t/ha of manure. The fractionation of heavy metals in the soil was evaluated after 5 years using a sequential extraction procedure. The application of the two amendments was found to increase the content of organic matter, the total nitrogen content and the electrical conductivity, whereas it slightly decreased the soil pH. The addition of manure did not have a significant effect on the accumulation of heavy metals in the soil, whereas compost application increased the total concentration of heavy metals in the soil. The distribution of heavy metals between the different fractions in untreated and treated soils showed the residual fraction to be dominant, followed by the fraction bound to Fe and Mn oxides. The amount of Cu bound to the organic fraction increased with the application rate, which is probably caused by the formation of organic complexes. For the other metals, the increase of the association with organic matter is very limited. The application of compost moreover increases the amount of Zn associated with Fe and Mn oxides. The “Mobility Factor (MF)” was quite low and did not change after the 5-year application of the two organic amendments. It always remained lower than 10%, although for Cd it amounted to 17%.     

Photodegradation of chlorinated pesticides dispersed on sand

The photochemical behaviour of several chlorinated pesticides, namely 4-chloro-2-methylphenoxyacetic acid (MCPA), dichlorophen (DCPH), flamprop-methyl (FPM) and vinclozolin (VCZ) is studied on various kinds of sand: Fontainebleau sand (almost pure silica), Touggourt sand (coloured sand from Sahara) and Jijel sand (dark marine sand). The photodegradation of MCPA is more rapid on Fontainebleau sand than on the two others, because the former is almost colourless pure silica and the others adsorb on the internal surface of the reactor. The degradation rate decreases in the order MCPA, DCPH, FPM, VCZ. The main products identified are 4-chloro-2-methylphenol with MCPA and reduction product with DCPH.     

Implication of organic acids in the long-distance transport and the accumulation of lead in Sesuvium portulacastrum and Brassica juncea

The implication of organic acids in Pb translocation was studied in two species varying in shoot lead accumulation, Sesuvium portulacastrum and Brassica juncea. Citric, fumaric, malic and α-cetoglutaric acids were separated and determined by HPLC technique in shoots, roots and xylem saps of the both species grown in nutrient solutions added with 200 and 400 μM of Pb(II). The lead content of the xylem saps was determined by ICP–MS. Results showed that S. portulacastrum is more tolerant to Pb than B. juncea. Lead concentration in xylem sap of the S. portulacastrum was significantly greater than in that of B. juncea. For both species, a positive correlation was established between lead and citrate concentrations in xylem sap. However minor relationship was observed for fumaric, malic and α-cetoglutaric acids. In the shoots lead treatment also induced a significant increase in citric acid concentration. Both observations suggest the implication of citric acid in lead translocation and shoot accumulation in S. portulacastrum and B. juncea. The relatively high accumulation of citric acid in xylem sap and shoot of S. portulacastrum could explain its high potential to translocate and accumulate this metal in shoot suggesting their possible use to remediate Pb polluted soils.     

Combined biological processing and microfiltration in the treatment of unhairing wastewater

Introduction  

The unhairing step, a part of the beamhouse process, is particularly polluting, generating an alkaline wastewater with high concentrations of organic and inorganic matter. The aim of this study was to evaluate the treatment of this industrial wastewater using a combination of biological and microfiltration processes.