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Background: Fungi are one of the pollutant emissions from the composting plants which change in variety during the composting process. They are predominant in stabilization stage
Methods: This study assessed the thermotolerant airborne fungi based on NIOSH 0800 on 200 ambient samples from four composting processes and outdoor spaces in a composting plant
Results: The concentration of fungi during shredding, separating and screening was higher than 1000 CFU/m[3]. The level of fungi in all stages was higher than outdoor [P<0.001]. The highest concentration was detected in shredding [6749 +/- 1347 CFU/m[3]] [P=0.007], and the lowest concentration was related to screening [113 +/- 32 CFU/m[3]] [P=0.013]. The predominant species was varied during the stages. Yeast and A. niger were predominant species in shredding and separating
Conclusion: The results of this study showed that the concentration of airborne fungi was decreased during composting process. The effect of these aerosols on indoor air was more than that in the outdoor space and workers at this site were exposed to high levels of thermotolerant fungi. Therefore, air-condition, ventilation system and safety operations such as respiratory masks are essential. The results of this study can be used in risk assessment
Assuntos
Aerossóis , Compostagem , Aspergillus , LevedurasRESUMO
Background: Biogas is obtained by anaerobic decomposition of organic wastes buried materials used to produce electricity, heat and biofuels. Biogas is at the second place for power generation after hydropower and in 2000 about 6% of the world power generation was allocated to biogas. Biogas is composed of 40-45 vol% CO[2], 55-65 vol% CH[4], and about 1% non-methaneVOCs, and non-methane volatile organic compounds. Emission rates are used to evaluate the compliance with landfill gas emission regulations by the United States Environmental Protection Agency [USEPA]. BTEX comounds affect the air quality and may be harmful to human health. Benzene, toluene, ethylbenzene and xylene isomers that are generally called BTEX compounds are the most abundant VOCs in biogas
Methods: Sampling of VOCs in biogas vents was operated passively or with Tedlar bags. 20 samples were collected from 40 wells of old and new biogas sites of Shiraz' landfill. Immediately after sampling, the samples were transferred to the laboratory. Analysis of the samples was performed with GC-MS
Results: The results showed that in the collection of the old and new biogas sites, the highest concentration of VOCs was observed in toluene [0.85ppm] followed by benzene [0.81ppm], ethylbenzene [0.13ppm] and xylene [0.08ppm]
Conclusion: The results of the study showed that in all samples, most available compounds in biogas vents were aromatic hydrocarbon compounds. These compounds' constituents originate from household hazardous waste materials deposited in the landfill or from biological/chemical decomposition processes within the landfill
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Background: Heavy metals have destructive and irreversible effects on the human, plants and animals. Some industries in Yazd enter industrial wastewater to municipal wastewater collection system. This can lead to high levels of heavy metals in wastewater and in turn in the wastewater treatment plant effluent
Methods: This study was carried out during four months from December 22, 2009 to May 20, 2010. The experiment was performed on the inflow, outlet of anaerobic pond and first and second facultative ponds of wastewater treatment plant and then transferred to the laboratory and measured by atomic absorption spectroscopy
Results: The results of the experiments showed that the average cadmium concentrations in the inflow, anaerobic pond outlet, and first and second facultative pond outlet were 0.0066, 0.0087, 0.0076, and 0.0083micro g/l, respectively. The average amounts of chromium in the inflow, anaerobic pond outlet, and first and second facultative pond outlet were 0.0076, 0.0065, 0.0043, and 0.0056 micro g/l, respectively. Cadmium concentration in the effluent was higher than standard
Conclusion: The comparison of the obtained data with Iranian standards for wastewater treatment for reuse in irrigation shows that the cadmium concentration exceeded the standard and the chromium concentration was lower than the standard. Therefore, it is not suitable for reuse in the crop farms and aquatic life
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Background: Atrazine is a widely used herbicide. The increasing salinity of many water resources has had a negative effect on atrazine biodegradation. The aim of this study was to isolate atrazine degrading bacteria in semi-salinity media
Methods: Nine selected bacterial species were cultivated on the mineral salt broth culture medium containing atrazine [50, 100, 500 mg/L], NaCl concentration [10 g/L], and 2% [wt/vol] agar. The bacteria with higher growths in the atrazine medium [500 mg/L] were selected. Then, those with higher growths were transferred to the medium with atrazine concentration of 1000 mg/L. The atrazine biodegradation rates by Ochrobactrum oryzae and consortium bacteria [all of the nine bacteria species] were compared by cultivating separately on the mineral salt broth containing atrazine concentration of 30 mg/l, and NaCl concentration of 10 g/L in the incubation time of 10 day and HPLC analysis
Results: The results indicated that Ochrobactrum oryzae had the highest growth compared to the other investigated bacteria [Acinetobacter radioresistens, Paenibacillus lautus, and Bacillus sp] in the mineral salt broth culture medium containing atrazine concentrations [1000 mg/L], NaCl [10 g/L], and 2% [wt/vol] agar. In the Ochrobactrum oryzae and bacterial consortium comparison, atrazine biodegradation rate in the culture medium containing NaCl, by Ochrobactrum oryzae, was higher than bacterial consortium and atrazine biodegradation rate in the culture medium with no NaCl addition, by Ochrobactrum oryzae, was lower than bacterial consortium
Conclusion: Based on the results, Ochrobactrum oryzae was significantly capable of atrazine biodegradation in the semisalinity aqueous environment
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Background: Contamination of water with arsenic has attracted the researchers' attention as a global problem in recent years and has been observed in some parts of Iran. The purpose of this study is to assess the efficiency of welding iron waste in removing arsenic from aqueous solutions
Methods: In this study, the effects of different parameters, such as pH [3-9], initial concentration of arsenic [100-3000 microg/l], contact time [5-90min] and adsorbent dose [2.5-20 g/l], were studied. The final concentrations of arsenic were analyzed by atomic absorption
Results: The results indicated that at pH=3 and fixed dose of 1 g, arsenic removal efficiency of iron waste was 89.73%. By increasing the pH to 7, the removal efficiency increased to 96.44%. Also, an increase in the amount of iron waste from 2.5 to 10g/l, the removal rate increased from about 42.37% to 96.70%. For contact times of 5 and 30 minutes, the removal rate was 9% and 96.62%, respectively. Then, with increasing the contact time to 90 minutes, the removal rate increased to 99.24%. Correlation coefficient of Freundlich and Langmuir isotherms for As[III] was 0.7593 and 0.9979, respectively
Conclusion: The results of the study showed that welding iron waste has a high potential as an effective, fast and cheap method for removal of arsenate and arsenite from aqueous solutions
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Background: Among Alkanes, N-Alkanes with medium chain have been identified as the most important contaminants of the soil. N-hexadecane [C[16]H[34]] with low solubility in water also belongs to this group and has been used by many researchers as a model contaminant. The present study aimed to investigate the effect of the external source of carbon [glucose] as co-substrate on removal of hexadecane from the soil
Methods: In this study, a Slurry Sequencing Batch Reactor [SSBR] was used as a pilot by a bacterial consortium, including bacterium Acinetobacter radioresistens, Bacillus subtilis, and Pseudomonas aeruginosa, in order to remove different concentrations of hexadecane [1,4,7, and 10 percent].Sampling was performed four times during the sedimentation step. Then, the samples were analyzed by GC-FID and the results were analyzed statistically
Results: The results showed that hexadecane removal [%] by the microbial consortium was higher in lower initial concentrations in such a way that the biological removal of hexadecane was respectively 45.95%, 38.55%, 34.39%, and 32.40% in the concentrations of 1%, 4%, 7%, and 10% on the third day. Moreover, adding the external carbon source [glucose] on the first day caused a 16% increase in hexadecane removal, which is 1.4 times more than the amount of hexadecane removal in the conditions without co-metabolism
Conclusion: The results showed that SSBR could be used as an exit-situation effective method for hexadecane removal in low concentrations through considering the effective factors in its function, such as dissolved oxygen, pH, and temperature. Also, adding the secondary carbon source could be effective in hexadecane removal from the soil. Yet, this effect might vary on different days