جستجوی مقالات مرتبط با کلیدواژه « nitrogen » در نشریات گروه « پزشکی »

Unsuitable management of municipal solid waste (MSW) is one of the main factors in environmental degradation, particularly in developing countries. This study aimed to analyze the quantitative and qualitative properties of MSW for energy recovery in the city of Mahabad, located in the West Azerbaijan Province, Iran.

Sampling from MSW was taken during the four seasons in 2014. Quality and quantity analyses included chemical composition, moisture percentage, dry weight, ash percentage, and heat value, which were performed in the lab as per the American Society for Testing and Materials Method D 5231-92. The experience modeling was used to extract chemical composition and heat value.

The results showed that MSW was composed of 75% food waste, 12% ash, and 61% moisture. In the MSW organic fraction (C28.7H43.6O15.3N1S0,065), carbon/nitrogen and heat values were found at 28.7 and 2.1 × 104 Kj Kg-1, respectively. Also, in the MSW biodegradable organic fraction (C23.7H37.7O14.69N1S0.069), heat value and produced methane were calculated to be 10077 Kj Kg-1 and 207 liters (148 g), respectively. Any carbon dioxide added to the atmosphere will hang around for a long time, between 200 and 200 ton day-1, which contributes to trapping heat and warming the atmosphere.

This study shows energy recovery from MSW is a good option, due to the high heat value. However, it is not an eco-friendly method as it will produce more greenhouse and poison gases and needs control systems.

This study aimed to determine the biological activity test of the alcoholic extract of the leaves of Catharanthus roseus.

Catharanthus roseus was used in the implementation of the experiment and it included three factors: the first factor is watering the plants with three concentrations of sodium chloride salt (0, 50, and 100mmol) of sodium chloride, the second factor is three concentrations of nitrogen (urea) (0, 100 and 200mg.L-1) and the third factor three concentrations of selenium (Na2SeO4; 0,25 and 50mg.L-1), then tested the biological activity of plant leaf extracts from all treatments against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria through Measure the diameters of the areas of inhibition of bacterial growth.

The results of the laboratory experiment showed that the extract of the leaves of triple combination plants (100mmol NaCl+200mg.L-1 N+50mg.L-1 Se) achieved the largest inhibition area for the growth of E. coli reaching 27.50mm compared to the control, which is 4.20mm, and plant leaf extract in the combination (100mmol NaCl+100mg.L-1 N+50mg.L-1 Se) recorded the largest inhibition area in S. aureus reached 50.27mm compared to the control which recorded 9.10mm.

The plant leaf extract had an important role in inhibiting the growth of the bacteria studied, and the highest inhibition was observed in the interaction between the three factors salt, nitrogen, and selenium.

Buriganga is considered as one of the most important river in the country. But, its water quality has changed dramatically, which is responsible for creating unfavorable conditions for aquatic life. The main aim of this study was to investigate the removal capacity of pollutants mainly nitrogen present in the Buriganga river as the most polluted rivers in Bangladesh, by floating constructed wetland.

This study was conducted under constant and variable shock loadings in two phases, namely ‘Phase I’ and ‘Phase II’ during 11 and 10 weeks, respectively, in which about 180 L of raw water was dosed into the tank containing a floating mat, and pollutant concentrations in the river water influent from the system were tested over a period of 21 weeks.

Floating treatment wetland (FTW) could sustain and remove about 31.25% and 19.23% of ammonia in the 9th and 10th weeks of Phase I, respectively, and 40.63% and 56.12% in the 17th and 18th weeks of Phase II, respectively. At first, ammonia was converted to ammonium, then, to nitrite, and finally, to nitrate. As the rhizosphere was denser and the biofilm was thicker in this study, so nitrogen removal efficiency during the application of shock loading in the 17th and 18th weeks of Phase II was considerable. The removal percentage of nitrite was 76.12 and 80%, respectively. In regular dosing of raw water in the 11th and 19th weeks in Phase I and Phase II, respectively, the total nitrate removal efficiencies from influent were 31.91 and 43.33%, respectively.

As water resources are limited, so improvement of water quality of the polluted Buriganga river would act as an important source of reusable water.

Dunaliella salina a green unicellular chlorophycean microalga, is famous as a robust carotenoid, fatty acids and also biomass producer. Biomass, lipid and β-carotene levels in D. salina increases during nutrient deprivation conditions. In this study the effects of nitrogen and sulfur starvation, on β-carotene, lipid and biomass production and composition in a naturally isolated D. salina strain was studied. Johnson culture medium was exploited for subculturing and growth of the studied strain. Direct cell counting method and also dry cell weight measurement were used for monitoring the cell growth. β-carotene production was measured using spectrophotometry method. The experiments were performed in 22 days with two different growth stages composed of 8 days of nutrient rich and 14 days of nitrogen and sulfur deprived media. The studied microalgal strain showed a higher biomass production and cell growth rate in comparison with the starvation condition. Moreover, a significant increase of cellular β-carotene and lipid contents was observed under nitrogen and sulfur limitation. The studied microalgal strain contained some important fatty acid with food, feed and biodiesel potentials. The obtained results suggested the applicability of macroelements deprivation strategy to elevate the carotenoids and lipid accumulation in D. salina with the minimum biomass reduction.

 The ability of extracellular polymeric substances (EPS) production was observed in many species of heterotrophic microorganisms through the biological wastewater treatment systems. 

 The batch experiments at different carbon/nitrogen and solid retention time (SRT) were carried out to investigate the effects of initial nitrogen concentration and SRT on EPS production and chemical oxygen demand (COD) removal efficiency. The artificial neural network (ANN) was developed to modeling of obtained data. 

 The results showed that: (i) with increasing SRT, the COD removal improves; (ii) initially, the amount of carbohydrate increases as SRT increases; however, with further increase of SRT, it declines; (iii) the protein/carbohydrate ratio improves as SRT decreases; (iv) the carbohydrate and protein concentration of soluble EPS increased with increasing initial nitrogen concentration from 0 to 10 mg/L; and (v) further increase of initial nitrogen concentration lead to depletion of carbohydrate production. 

 The highest yield (Y) value was calculated at low sludge age and deficient initial nitrogen concentration, which may be due to the application of EPS production mechanism. The ANN model moderately predicted effluent COD concentration, carbohydrate, and protein production.