جستجوی مقالات مرتبط با کلیدواژه « شرایط بهینه » در نشریات گروه « محیط زیست »

This study was designed to determine the effects of temperature, pH and dKH on growth performance indices of Macro (Labidochromis caeruleus). In each aquarium, 3 fishes were entered randomly with the weighted average: 0.31 ± 0.05 gr and were fed, 5% of biomass twice daily. After 2 weeks adapting, In two intervals,1-25 days and 25-40 days, the biometric measurements were done and growth indices were calculated. In the end, weighted average of fishes was 0.75 ± 0.05 gr. In each aquarium, there were specific combinations of temperature, pH and dKH, using response surface method by Design Expert 7.0, and in total 14 combinations of factors each with 3 replications. According to the results, the combinations of temperature 26˚c, pH: 7.5 and 7 dKH had the best effect on fishes. Studying growth patterns showed that the best mathematical model to show the changes of growth indices was the quadratic equation. The interactions between pH × temperature, and dKH, was more effective on weight changes. At the first time interval, the optimum conditions were 26˚c, pH 7.5 and dKH 7.97-8.2, and at the second period, the optimum conditions were a combination of 25.37-25.62˚c, dKH 8.2-8.35 and pH 7.5-8.25. The optimum temperature to have the least FCR, was 27.67˚c, dKH: 7.65-8 and pH: 6.7-8. Besides, none of the linear, quadratic and cubic equations, represents the length growth of Macro fishes. Therefore, the results of this study, determined the optimum conditions of rearing this species according to the three mentioned parameters.

Phenol presence and its derivatives in water and waste water on human health and the environment is one the major concerns. Because of the toxicity of phenol and also because of the presence of even low concentrations in natural resources, water disinfection and oxidation processes can lead to the formation of additional components. This material is one of the most common organic pollutants in water. In this research, adsorption of phenol from wastewater by sawdust was simulated using intelligent techniques. Intelligent techniques including multi-layer Perceptron, radial basis functions network and support vector regression were used. To design the network structure as well as the training and testing of 125 sets of experimental data is used. Performance evaluation criteria and stop network consists of % AARE and, which is used for all three models. All models compared results showed that the support vector regression with 0.5132 and 0.979, respectively, for %AARE and  is the best model. All models are better results than the quadratic polynomial model showed. Models showed good agreement with experimental data. The optimum conditions for the removal of phenol were 127.6 mg/l of initial phenol concentration, 0.84 g/l of adsorbent dose, natural pH value of 3.62 and 146.9 min of contact time, under these conditions the maximum removal efficiency was 91.23%.

In order to isolate and to identify naphthalene degrading bacteria from Nayband Bay sediments and to optimize biodegradation efficiency using the most effective isolated strain, surface sediment samples were collected from Nayband Bay mangrove forests. Obtained samples were then cultured on mineral salts medium (MSM) containing naphthalene as a sole carbon source. At the end of the enrichment, three bacterial strains in the consortium were isolated by spreading the 10-fold serially diluted consortium on nutrient agar plates. Naphthalene biodegradating efficiency of the isolated strains was monitored in two culture media: 1-MSM + naphthalene, 2-MSM + naphthalene + Tween-80. The ability of bacterial isolates to degrade naphthalene was studied by using gas chromatography. Among the isolated strains, SBU3 was found to be more efficient, degrading naphthalene in presence and absence of Tween-80, 60.45% and 39.30% respectively. This strain was identified by 16s rDNA gene sequence and results showed that it has 99% similarity to Marinobacter aquaeolei. The Optimum pH and C/N molar ratio for the biodegradation of naphthalene were studied in presence of 1% tween-80, results show that the pH 7.5 and C/N ratio of 100:10 were the optimum conditions and more than 85% of naphthalene removed within 7 days. Furthermore, the biodegradation kinetics of naphthalene corresponded with the first-order rate model.