فهرست مطالب

Environmental Health Science and Engineering - Volume:6 Issue:2, 2009
  • Volume:6 Issue:2, 2009
  • تاریخ انتشار: 1388/02/11
  • تعداد عناوین: 11
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  • R. Rajeswari, S. Kanmani Page 61
    The degradation of pesticide Carbendazim was investigated by combination of TiO2-based photocatalysis and ozonation. A batch annular photoreactor has been used for carrying out the combined process and the influence of TiO2 concentration, ozone dose and pH were investigated. The results showed that the removal rate increased with increase in ozone dosage upto 0.48 g/h and decreased above 1g/L of TiO2. At optimum pH=6, with 1g/L TiO2 and with 0.48g/h ozone dose, 88% COD removal was achieved in 3 hours by the combined photocatalytic ozonation process, where as 54% and 67% COD removal was observed with each photocatalysis and ozonation process, respectively. BOD5/COD ratio was enhanced to 0.38 and TOC removal was 80% in 180 min of combined treatment. Carbendazim was quickly degraded by the combined photocatalytic ozonation process and followed pseudo-first order kinetics. The kinetic study showed that degradation rate constant of Carbendazim with TiO2/UV/O3 to be 1.5 times higher than that & O3 with the same ozone dose and 2.2 times higher than that of TiO2/UV. A mechanism involving the formation of an ozonide radical previous to the generation of hydroxyl radicals is suggested to explain the synergistic effect between ozone and TiO2 under illumination. The laboratory study has also demonstrated that a combination of TiO2-based photocatalysis and ozonation will overcome the disadvantage of the selectivity of ozonation and the lower efficiency of TiO2 photocatalysis.
    Keywords: Pesticide, Photocatalysis, Ozonation, Photocatalytic Ozonation, Synergistic effect, Carbendazim
  • A. Naimabadi, H. Movahedian Attar, A. Shahsavani Page 67
    This study investigates the anaerobic treatability of reactive Red2 in an anaerobic/aerobic sequential process. Laboratory scale anaerobic baffled reactor and fixed activated sludge reactor were operated at different organic loadings and hydraulic retention times. The effects of shock dye concentration on the chemical oxygen demand and color removal efficiencies were investigated in the anaerobic baffled reactor. The effect of hydraulic retention time on the color and chemical oxygen demand removal efficiencies were also investigated in the aerobic reactor. The studies were carried out in continuous mode and the effluent of the anaerobic baffled reactor was used as feed for the fixed activated sludge reactor. Chemical oxygen demand removal efficiency of 54.5% was obtained at HRT =1 day in the anaerobic reactor. The average color removal was 89.5%. Chemical oxygen demand removal efficiency of 69% was obtained at HRT =7 h in the aerobic fixed activated sludge reactor. A slight decrease of the color was also observed in the aerobic reactor. This investigation has shown that successful treatment of a highly colored wastewater is possible in the anaerobic baffled reactor. Also the results showed that, anaerobic biological system has higher efficiency in dye removal than fixed activated sludge system, while aerobic system has higher efficiency in chemical oxygen demand removal comparing with the anaerobic baffled reactor.
    Keywords: Azo (reactive dye), reactive Red2, Anaerobic baffled reactor, Aerobic fixed activated sludge reactor, Sequential process
  • M. &Oumlztürk, G. &Oumlz&oumlzen, O. Minareci, E. Minareci Page 73
    In the present study, some heavy metals (Cd, Cr, Cu, Fe, Ni and Pb) were seasonally determined in water, sediment and some tissues of Cyprinus carpio from Avsar Dam Lake, which is an important water source for irrigation and drinking in Turkey. Heavy metal levels in water, sediment and fish samples were analyzed by inductively coupled plasma spectroscopy (ICP/AES). The obtained results showed that the average values of Fe in water samples were higher than the respective reference values for fresh water. Results for levels in water were compared with national and international water quality guidelines, as well as literature data reported for the lakes. The analysis of heavy metals in sediments indicated that among the six heavy metals tested, Fe was maximally accumulated, followed by Ni, Cu, Cr, Pb and Cd. Heavy metal concentrations were found to decrease in sequence of the Cyprinus carpio samples, in the muscle and stomach-intestine as Fe > Cu > Pb> Ni > Cr > Cd; in the gill, heart and liver as Fe > Cu > Ni > Pb > Cr > Cd and in the air sac as Fe > Cu > Ni > Pb > Cd >Cr. In the fish samples, cadmium, chromium, nickel and lead concentrations exceeded the tolerable values provided by international institutions.
    Keywords: Heavy metal, Cyprinus carpio, sediment, pollution, environment
  • M. Farrokhi, S. Ahmadizad Page 81
    In this study dissolved humic substances and yeast extract were tested in different concentrations for enhancing methyl tert-butyl ether mineralization by isolated microorganisms from a variety of sources. All experiments were conducted at a constant temperature of 25ºC. Vials of 50 mL and 125 mL volume sealed with Teflon-lined Mini-Nert caps was used for microcosm experiments. In all experiments 1% sodium azide were used as control. Samples of bacterial cultures that metabolize methyl tert-butyl ether have been analysed by direct GC analysis using flame ionization detector. Cultures able to metabolize have been found in activated sludge and soils. These microorganisms were
    gram-positive bacterium. An aerobic microbial consortium was enriched in laboratory for four months. Methyl tert-butyl ether has been shown to biodegrade under aerobic and co-metabolic conditions. A microbial consortium isolated from activated sludges was identified as Cocobacillus. The concentration of the initial attached biomass was about 0.11 g/L of dry weight. The maximum mineralization rate and beneficial effects of stimulator substances on aerobic biodegradation of methyl tert-butyl ether occurred with the culture by combined concentrations of 500 mg/L of yeast extract and 20 mg/L of peat humic growth support of microbial consortium within 216 h and in presence of high oxygen levels and well mixing conditions. It was shown that adding, peat humic and yeast extract together, had better stimulatory effect on methyl tert-butyl ether biodegradation. Results clearly showed a stimulatory effect on methyl tert-butyl ether consumption higher than 20%. Consortium was capable of degrading concentrations of ≤1000 mg/L, whereas concentrations of >1000 mg/L, were not degraded.
  • A. J. Jafari, R. Pourkabireh Abasabad 2, A. Salehzadeh Page 89
  • M. Rahiminejad, S. J. Shahtaheri, M. R. Ganjali, A. Rahimi Forushani, F. Golbabaei Page 97
    Amongst organophosphate pesticides, the one most widely used and common environmental contaminant is diazinon; thus methods for its trace analysis in environmental samples must be developed. Use of diazinon imprinted polymers such as sorbents in solid phase extraction, is a prominent and novel application area of molecular imprinted polymers. For diazinon extraction, high performance liquid chromatography analysis was demonstrated in this study. During optimization of the molecular imprinted solid phase extraction procedure for efficient solid phase extraction of diazinon, Plackett-Burman design was conducted. Eight experimental factors with critical influence on molecular imprinted solid phase extraction performance were selected, and 12 different experimental runs based on Plackett-Burman design were carried out. The applicability of diazinon imprinted polymers as the sorbent in solid phase extraction, presented obtained good recoveries of diazinon from LC-grade water. An increase in pH caused an increase in the recovery on molecular imprinted solid phase extraction. From these results, the optimal molecular imprinted solid phase extraction procedure was as follows: solid phase extraction packing with 100 mg diazinon imprinted polymers; conditioning with 5 mL of methanol and 6 mL of LC-grade water; sample loading containing diazinon (pH=10); washing with 1 mL of LC-grade water, 1 mL LC- grade water containing 30% acetonitrile and 0.5 mL of acetonitrile, respectively; eluting with 1 mL of methanol containing 2% acetic acid. The percentage recoveries obtained by the optimized molecular imprinted solid phase extraction were more than 90% with drinking water spiked at different trace levels of diazinon. Generally speaking, the molecular imprinted solid phase extraction procedure and subsequent high performance liquid chromatography analysis can be a relatively fast and proper approach for qualitative and quantitative analysis of diazinon in drinking water.
    Keywords: Non, covalent imprinting approach, Molecularly imprinted solid phase extraction, Experimental design, Plackett, Burman design, Diazinon
  • R. Shokoohi, M. H. Saghi, H. R. Ghafari, M. Hadi Page 107
    This study was conducted to investigate the removal of iron by dried biomass of activated sludge. Dried activated sludge, prepared as a powder, was tested as a sorbent for the removal of iron from aqueous solutions. The effects of various experimental parameters including initial iron concentration, mass of biomass and contact time were examined and optimal experimental conditions were obtained. The equilibrium time for iron adsorption onto biomass was determined as 150 min. The rate of iron removal was directly correlated to biomass amount and contact time. Increasing contact time from 0.5h to 2.5h resulted in 25% improvement in iron removal efficiency. When the weight of the biomass increased from 0.1g to 0.9 g, the iron removal efficiency increased from 62% to 95%. High initial iron concentration had an adverse effect on iron removal efficiency. Increasing initial iron concentration from 2 to 10 (mg/L) caused declining the iron removal efficiency from 70% to 56%. Freundlich, Langmuir, Dubinin-Radushkevich and Temkin isotherm models could describe the adsorption equilibrium of the iron onto the activated sludge. Meanwhile, Freundlich isotherm represented a better correlation compared to other isotherms (R2 > 0.999). Also Elovich kinetic models fits well with experimental data (R2>0.997).
    Keywords: Biosorption, Dried Activated Sludge, Iron, Adsorption
  • H. Movahedyan, H. Khorsandi, R. Salehi, M. Nikaeen Page 115
    Phenol is one of the organic pollutants in various industrial wastewaters especially petrochemical and oil refining. Biological treatment is one of the considerable choices for removing of phenol present in these wastewaters. Identification of effective microbial species is considered as one of the important priorities for production of the biomass in order to achieve desirable kinetic of biological reactions. Basic purpose of this research is identification of phenol-degrading Pseudomonas Putida in activated sludge by polymerase chain reaction (PCR) that has high speed and specificity. In this research, 10 various colonies of phenol-degrading bacteria were isolated from municipal activated sludge and the rate of phenol removal and growth rate of these bacteria were assessed in different concentrations of phenol (200 - 900 mg/L). Confirmation of the largest subunit of multicomponent phenol hydroxylase (LmPH) gene and gene coding the N fragment in Pseudomonas Putida-derived methyl phenol operon (DmpN gene) through PCR were used for general identification of phenol-degrading bacteria and Pseudomonas Putida, respectively. Presence of a 600 bp (base pairs) bond in all of isolated strains indicated that they contain phenol hydroxylase gene. 6 of 10 isolated bacteria were Pseudomonas Putida because they produced a 199 bp PCR product by DmpN primers. According to PCR results in this study, the best phenol-degrading bacteria that can utilize 500 - 600 mg/L phenol completely after 48 hours incubation, belong to Pseudomonas Putida strains. It is clear that use of isolated bacteria can lead to considerable decrease of treatment time as well as promotion of phenol removal rate.
    Keywords: Phenol, Degrading Bacteria, Polymerase Chain Reaction, Wastewater, Pseudomonas Putida, Activated sludge
  • F. H. Chang, C. R. Yang, C. Y. Tsai, W. C. Lin Page 121
    This study characterized the airborne exposure of students to thirty polybrominated diphenyl ether congeners inside and outside a computer classroom in a southern Taiwan college. Arithmetic mean values of total indoor and outdoor polybrominated diphenyl ether concentrations were 125.0 pg/m3 (89.8 to 203.9 pg/m3) and 110.3 pg/m3 (83.5 to 157.0 pg/m3), respectively. Total indoor polybrominated diphenyl ether concentrations were one order of magnitude lower than those detected in homes in Birmingham, United Kingdom and in Ottawa, Canada but were several times higher than those measured in the ambient air in Ottawa, Canada and from the Bohai Sea to the Arctic. The five highest indoor concentrations of polybrominated diphenyl ether congeners were decabromodiphenyl ether (23.0 pg/m3), 4,4''-dibromodiphenyl ether (15.9 pg/m3), 2,2'',3,4,4'',5,5'',6-octabromodiphenyl ether (10.6 pg/m3), 2,4-dibromodiphenyl ether (10.3 pg/m3) and 2,2'',3,4,4'',5'',6-heptabromodiphenyl ether (10.0 pg/m3). Although indoor and outdoor total polybrominated diphenyl ether concentrations did not significantly differ, the indoor concentrations of 2,4-dibromodiphenyl ether, 2,2'',4-tribromodiphenyl ether, 2,4,4''-tribromodiphenyl ether, 2,2'',4,5''-tetrabromodiphenyl ether and 2,3'',4'',6-tetrabromodiphenyl ether were significantly higher than their outdoor concentrations. This study suggests the following measures: 1) to increase the air exchange rate and open classroom doors and windows for several minutes before classes to reduce indoor PBDE concentrations; 2) to reduce polybrominated diphenyl ether emissions from new devices, it''s better to use computer-related products that meet the Restriction of Hazardous Substances Directive adopted by the European Union.
    Keywords: Polybrominated diphenyl ethers, Exposure, Indoor, Computer classroom
  • M. Malakootian, N. Yousefi Page 131
    There are various techniques for removal of water hardness each with its own special advantages and disadvantages. Electrochemical or electrocoagulation method due to its simplicity has gained a great attention and is used for removal of various ions and organic matters. The aim of the present study was to investigate the efficiency of this technique in removal of water hardness under different conditions. This experimental study was performed using a pilot plant. The applied pilot was comprised of a reservoir containing aluminum sheet electrodes. The electrodes were connected as monopolar and a power supply was used for supplying direct electrical current. Drinking water of Kerman (southeast of Iran) was used in the experiments. The efficiency of the system in three different pH, voltages and time intervals were determined. Results showed the efficiency of 95.6% for electrocoagulation technique in hardness removal. pH and electrical potential had direct effect on hardness removal in a way that the highest efficiency rate was obtained in pH=10.1, potential difference of 20 volt and detention time of 60 minutes. Considering the obtained efficiency in the present study, electrocoagulation technique may be suggested as an effective alternative technique in hardness removal.
    Keywords: Electrocoagulation technique, Hardness removal, Aluminum electrode, Electrochemical technique
  • G. H. Mohammadi Page 137
    Traffic noise is a major environmental source of pollution in the whole planet, both in developed and in developing nations. The study being reported here has been carried out on one of the most busy and crowded streets in the downtown area of Kerman, located in south east of Iran, which have heavy traffic during the day. Total of 20 measuring points were selected along the main road and its 6 connecting streets. In this study the A-weighted continuous equivalent sound level values and statistical levels were manually measured at each site separately. The noise equivalent level varied between 66 to 79.5 dBA. The results of the study established the fact that noise levels are more than the acceptable limit of 60 dBA, which is the daytime governmentally prescribed noise limit for residential-commercial areas. This paper also describes the reaction of the environmental noise of the city of Kerman. A total of 250 questionnaires were processed. The results of the interview questionnaire revealed the following items; (I) the main isolated noise source was traffic (50%) and street noise (34%); (II) 70% of the people classified the noise in his/her street as "very high"; (III) 52% and 48% of the respondents answered that noise bother them more in morning and evening, respectively; (IV) 86% and 86.8% of the subjects answered that traffic noise produce physicsl and psychological annoyance to them; (V) the main outcomes of exposure to noise were: irritability (40.8%), insomnia (24%), difficulty in concentrating (16%) and conservation disruption (16%).
    Keywords: Noise pollution, Traffic noise, Noise measurements, Noise annoyance, Community response