فهرست مطالب

Environmental Health Science and Engineering - Volume:6 Issue:4, 2009
  • Volume:6 Issue:4, 2009
  • تاریخ انتشار: 1388/08/11
  • تعداد عناوین: 11
  • H. Hajiabadi, M. R. Alavi Moghaddam, S. H. Hashemi Page 217
    The main aim of this study was to investigate the effect of sludge retention time on performance of aerobic synthetic Batch Reactor for treating a high load milk synthetic wastewater. For this purpose, four lab-scale sequencing batch reactors were operated under aerobic conditions with the same conditions at different sludge retention times (SRTs), feeding by high load milk synthetic wastewater. Operating volume, influent flow rate and influent organic loading rate for all reactors were adjusted to 5.5 L, 3.5 L/d and 1400 gCOD/m3d, respectively. The average effluent COD for reactor 1 to 4 with SRT of 5, 10, 15 and 20 d were 108, 97, 91 and 84 mg/L, respectively. COD removal was 94.99, 95.43, 95.86 and 96.16 percent respectively and slightly changed with SRT. However, the overall trend of COD removal vs. SRT showed an increasing rate with the correlation factor (R2) of 0.99. Reactor 2 with SRT of 10 d(SVI) had the maximum effluent TSSave (34mg/L) and turbidityave (5.89 mg/L) and the minimum sludge volume index (41mL/g). All reactors had SVIave of lower than 75 mL/g and effluent turbidityave less than 6 NTU which was lower than Iranian national discharge standards (<50 NTU). SRT had directly influenced the biomass concentration, as the MLSSave of reactor 1 to 4 were found to be 1824, 2694, 3210 and 3864 mg/L respectively. Best performance (minimum effluent COD, TSS and turbidity) was occurred in reactor 4 with SRT of 20 d.
    Keywords: Aerobic Sequencing batch reactor, High load wastewater, Sludge retention time, Organic loading rate
  • S. Nasseri, M. Dehghani, S. Amin, K. Naddafi, Z. Zamanian Page 223
    Atrazine, a herbicide widely used in corn production, is frequently detected as pesticide in water resources. In this research, four agricultural fields with a long history of atrazine application in Shiraz and its vicinity in Fars province of Iran, have been studied to determine the fate of atrazine through the passage of time. These four farms were cultivated under a crop rotation (corn-wheat) during the past 10 years. Samples were collected from four soil profiles of 0-10, 10-20, 20-40, and 40-60 cm soil depth at different times. The time intervals for soil sampling started before atrazine application and continued until no atrazine was detected. According to the general linear model, there was no significant difference between atrazine residual concentrations and the soil moisture and depth (p≥0.05). But, significant difference between atrazine residual concentrations and the sampling regions was observed (p<0.001). Based on the data, atrazine leaching and dissipation rate in different soil profiles in the four sampling regions were high and significant. Therefore, there is a high risk of atrazine pollution in groundwater resources of the region.
    Keywords: Atrazine, Soil, Shiraz, Dissipation rate, Pesticide fate
  • A. H. Mahvi, A. Maleki, R. Rezaee, M. Safari Page 233
    Humic substances mainly humic acids constitute the major fraction of natural organic matter in water supplies. They play an important role in the formation of harmful disinfection by products. Degradation of humic acids by means of ultraviolet radiation and ultrasonic irradiation processes was investigated in a laboratory-scale batch photoreactor equipped with an 300 W immersed-type medium-pressure mercury vapour lamp and sonoreactor with low frequency (42 kHz) plate type transducer at 170 W of acoustic power with emphasis on the effect of various parameters on degradation efficiency. Experiments were performed at humic acids initial concentrations varying between 2.5-10 mg/L. Oxidation of humic substances has been followed over time by measuring total organic carbon and UV absorbance in 254 nm and 436 nm. Initial results indicated a strong capacity of photolysis for degradation of humic substances. The results also showed that ultrasonic alone cannot be an efficient method for degradation of humic substances in comparison with UV process. The maximum degradation efficiency of humic substances after 90 min of irradiation, however, was only 5.7% and reached a maximum value of 9.5% after 300 min of irradiation. It was found that total organic carbon can be removed effectively by photolysis. It was also found that lower concentrations of humic substances favor the humic substances degradation. Also, the experimental results indicated that the kinetics of ultrasono-oxidation and photo-oxidation processes fit well by pseudo-first order kinetics.
    Keywords: Humic acids, Ultraviolet radiation, Ultrasonic irradiation
  • Z. Yousefi, H. Ziaei hezarjaribi, A. A. Enayati, R. A. Mohammadpoor Page 241
    There is a direct relation between the prevalence of some parasitic diseases and the presence of those etiologic agents in water. The purpose of this research was to determine the contamination rate of wells drinking water to parasites in Mazandaran province in the north of Iran. 989 water samples were randomly taken based on the population of towns and number of health centers from 12 cities of Mazandaran province and transferred to the laboratory in sterile containers. Water samples were then filtered and analyzed according to the World Health Organization guidelines. Direct method and Gram staining procedure were used to identify the parasites. If cryptosporidium was seen, floatation (sheather''s sugar) and modified Ziehl-Neelsen staining method were performed. Parasites count was undertaken using McMaster counting slide (0.3 mL). 197 out of 989 water samples were contaminated with different parasites. From 197 contaminated samples, 20 different types of parasites were separated of which 53 (26.9%) were pathogenic, 100 (50.8%) non pathogenic, and 44 non-infective stages of parasites. Distance between wells and sources of contamination, type of water distribution systems, city and chlorination status had significantly statistical relationship with contamination prevalence (p<0.001). According to the results and considering the direct correlation between safe water and human health, proper implementation of providing hygienic drinking water should be enforced.
    Keywords: Parasites, Drinking water, Wells, Contamination, Human health, Mazandaran
  • B. Bina, M. H. Mehdinejad, M. Nikaeen, H. Movahedian Attar Page 247
    During the last decade, there has been a concern about the relation between aluminum residuals in treated water and Alzheimer disease, and more interest has been considered on the development of natural coagulants such as chitosan. Chitosan, a natural linear biopolyaminosaccharide, is obtained by alkaline deacetylation of chitin. The present study was aimed to investigate the effects of alum as coagulant in conjunction with chitosan as coagulant aid on the removal of turbidity, hardness and Escherichia coli from water. A conventional jar test apparatus was employed for the tests. The optimum pH was observed between 7 to 7.5 for all turbidities. The optimum doses of alum and chitosan when used in conjunction, were 10mg/L and 1mg/L, 5mg/L and 0.5mg/L, and 5mg/L and 0.5mg/L in low, medium and high turbidities, respectively. Turbidity removal efficiency was resulted between %74.3 to %98.2 by alum in conjunction with chitosan. Residual Al in treated water was less than 0.2 mg/L, meeting the international guidelines. The results showed that turbidity decrease provided also a primary Escherichia coli reduction of 2-4 log units within the first 1 to 2 hr of treatment. Hardness removal efficiency decreased when the total hardness increased from 102 to 476mg/L as CaCO3. At low initial turbidity, chitosan showed marginally better performance on hardness, especially at the ranges of 100 to 210 mg/L as CaCO3. In conclusion, coagulant aid showed a useful method for coagulation process. By using natural coagulants, considerable savings in chemicals and sludge handling cost may be achieved.
    Keywords: Chitosan, Coagulant aid, Hardness removal, Escherichia. coli removal, Water treatment
    A. Akhavan Sepahei, V. Rashetnia Page 253
    Tellurium compounds can be found in high concentrations in land and water near sites of waste discharge of industrial manufacturing processes and anodic sludge of copper mine. Potassium tellurite (K2TeO3) is toxic to many microorganisms at concentrations >1mg/mL. In this research, some species of facultative anaerobic bacteria (Bacillus sp.) were isolated from Sarcheshme copper mine(Kerman, Iran) which demonstrated high-level-resistance to tellurite and accumulation of metallic tellurium crystals. High-level-resistance was observed for Bacilli and cocci grown with certain organic carbon sources, implying that tellurite reduction is not essential to confer tellurite resistance. Level of adsorption was determined by inductively coupled plasma and spectrophotometer (Diethyldithiocarbamate method). The level of tellurite concentration in the bacteria cell and the formation of tellurium nanocrystals were illuminated by transmission electron microscope and scanning electron microscope. The Te(0) crystals occur internally and each microorganism forms a distinctly different structure (for example Bacillus selenitreducens make tellurium nano rod). In this study it was found that microorganism can grow 3.in 1500mg/L-2000mg/L and higher tellurite concentrations. The use of microorganisms to generate Te nanomaterials may be an alternative for bench-scale syntheses. Additionally, they may also generate products with unique properties unattainable by conventional physical/chemical methods. This study is important because native bacteria from Sarcheshme (Kerman, Iran) that may show high-level-resistance to tellurite, were isolated.
    Keywords: Tellurium, ICP, Nanorod, Transmission electron microscope, Scanning electron microscope, High, level, resistance, Tellurite
    M. Farajzadeh, M. Darand Page 261
    The quantification of the relationship between daily mortality and air temperature, as a fundamental policy is essential to enhance the accuracy of the warning system of decrease and increase of temperature. The objective of this study was to investigate the relationship between temperature and death rate in Tehran during the period (2002-2005) by combining statistical and geographic information system methods. The Results of this study indicate that there is a strong and meaningful correlation between air temperature and death rate especially between monthly averages ones. The highest rate of mortality has occurred in the cold months of the year (December, January and February). and as the temperature decrease, the death rate increase. The increase in death rate caused by cardiovascular, respiratory and stroke diseases in the cold months of the year, bears proof to this matter. Among 22 zones of Tehran, zones 9, 6 and 12 have got the highest number of death occurrence. The correlation between daily death rate and daily temperature averages was V-shaped. Results of this study confirm some previous findings such as those in Moscow, United States, Hong Kong, Madrid, Athens and Shanghai. Temperature minimum mortality for Tehran was calculated as 28.5°C. The obtained results also indicate that the higher was the temperature difference from the Temperature minimum mortality, the more the death rate increased. Finally, the optimum policies for the mitigation of mortality in Tehran are presented.
    Keywords: Death rate, Disease, Temperature minimum mortality, Climate, Geographic Information System, Tehran
    M. R. Monazzam, P. Nassiri Page 271
    This paper presents the results of an investigation on the acoustic performance of tilted profile parallel barriers with quadratic residue diffuser (QRD) tops and faces. A 2D boundary element method (BEM) is used to predict the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface and faces of all tilted profile parallel barrier models introduced here is found to improve the efficiency of barriers compared with rigid equivalent parallel barrier at the examined receiver positions. Applying a QRD with frequency design of 400 Hz on 5 degrees tilted parallel barrier improves the overall performance of its equivalent rigid barrier by 1.8 dB(A). Increase in the treated surfaces with reactive elements shifts the effective performance toward lower frequencies. It is found that by tilting the barriers from 0 to 10 degrees in parallel set up, the degradation effects in parallel barriers is reduced but the absorption effect of fibrous materials and also diffusivity of the quadratic residue diffuser is reduced significantly. In this case all the designed barriers have better performance with 10 degrees tilting in parallel set up. The most economic traffic noise parallel barrier which produces significantly high performance, is achieved by covering the top surface of the barrier closed to the receiver by just a QRD with frequency design of 400 Hz and tilting angle of 10 degrees. The average A-weighted insertion loss in this barrier is predicted to be 16.3 dB (A).
    Keywords: Tilted parallel noise barrier, Diffusion, Boundary element method
    M. R. Samarghandi, M. Hadi, S. Moayedi, F. Barjasteh Askari Page 285
    The adsorption of a mono azo dye methyl-orange (MeO) onto granular pinecone derived activated carbon (GPAC), from aqueous solutions, was studied in a batch system. Seven two-parameter isotherm models Langmuir, Freundlich, Dubinin-Radushkevic, Temkin, Halsey, Jovanovic and Hurkins-Jura were used to fit the experimental data. The results revealed that the adsorption isotherm models fitted the data in the order of Jovanovic (X2=1.374) > Langmuir > Dubinin-Radushkevic > Temkin > Freundlich > Halsey > Hurkins-Jura isotherms. Adsorption isotherms modeling showed that the interaction of dye with activated carbon surface is localized monolayer adsorption. A comparison of kinetic models was evaluated for the pseudo-second order, Elovich and Lagergren kinetic models. Lagergren first order model was found to agree well with the experimental data (X2=9.231). In order to determine the best-fit isotherm and kinetic models, two error analysis methods of Residual Mean Square Error and Chi-square statistic (X2) were used to evaluate the data.
    Keywords: Adsorption isotherms, Methyl orange, Kinetic models, Activated carbonan
    R. Rostami, K. Naddafi, A. Aghamohamadi, H. Najafi saleh, M. Fazlzadeh davil Page 295
    Different food products such as corn, wheat and peanut have shown high potential to be contaminated in suitable environmental conditions, such as temperature and humidity. Some fungi can produce toxins, like Aflatoxin, and some of them are carcinogen. The purpose of this research was to study fungal contamination in peanuts being sold in the BAZAR of the city of Zanjan. 20 samples of 50g roasted and salted peanuts and 16 samples of 50g unsalted peanuts (pure) were collected from Zanjan BAZAR. Ambient conditions such as light intensity, temperature and air flow of the BAZAR and also the relative humidity of peanuts were measured. Samples were analyzed for fungal colony and were identified using slide culture technique. Results showed that Mold fungi were dominant among the colonies as. Aspergillus flavus (39.1%), Penicillium (9.2%), Rhizopus (7.2%), Mucor (2.5%), Alternaria (1.03%) and Nigrospora (0.5%). Temperature and the samples relative humidity were higher than the standard range. The results indicated a significant relation between relative humidity, light intensity, temperature and peanuts'' type (pure or salted) with level of fungal contamination. Also, roasting and processing reduced the relative humidity of peanuts and the level of contamination. Hence roasting, salting and provision of appropriate ambient conditions can be useful to peanut storage.
    Keywords: Peanut, Fungi, Mold, Zanjan, Ambient conditions
    Page 301
    The reaction of disinfectants with natural organic materials (NOM) existing in water lead to the formation of Disinfection By-Products. Potentially hazardous and carcinogenic characteristics of THMs recognized. Thus removal of THMs or THMs precursor is necessary for human health the aim of this study was to research of efficiency of domestic reverse osmosis (RO) in removal of trihalomethanes (THMs) from drinking water. In this study was used pilot scale of RO system with Polyamide membrane as Spiral-Wound, Tape wrapping module. Feed solution was made by using of pure chloroform. The samples containing chloroform were analyzed using a gas chromatograph, which equipped with a flame ionization detector. By increasing the flow, the removal rate of chloroform decrease and with declining removal of EC, the removal of chloroform was declined too. In this research, at worst condition, the efficiency of the pilot scale reverse osmosis reached to 80 % removal of chloroform.
    Keywords: Polyamide membrane, Reverse osmosis, Trihalomethanes, Precursor, Gas chromatograph