فهرست مطالب

Environmental Health Science and Engineering - Volume:5 Issue:4, 2008
  • Volume:5 Issue:4, 2008
  • تاریخ انتشار: 1387/06/11
  • تعداد عناوین: 11
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  • A. K. Singh, T. K. Banerjee Page 217
    The bottom dwelling air-breathing catfish, Clarias batrachus (Linn.) also respires via its skin (an accessory water-breathing organ). Prolonged (90 days) exposure to disodium arsenate heptahydrate has caused massive damage (e.g. wear and tear of various cellular components including club cells, hypertrophy and hyperplasia of the goblet mucous cells, altered staining and the slimy secretion) to the epidermis of its skin. The present study investigated the recovery in architecture of the damaged epidermis following return of the 90 days disodium arsenate heptahydrate exposed fish to clean water. The significant regeneration of its different cellular components (epithelial cells, Club cells, Mucous cells) took place after 24 h of withdrawal when sloughing; wear and tear and other damages of the epidermis of the skin got substantially reduced. The histopathological alterations which still continued included squeezing out of contents of the Club cells that formed a thin layer on the body surface. Regeneration of the Club cells continued throughout the epidermis even though the newly formed Club cells still showed massive sign of degeneration. Altered staining behaviour and hyperactivity of the Mucous cells continues even after prolonged withdrawal of the stress of the arsenic salt. Similarly the glycoproteins of the slime secreted by the mucous cells retained their sulphate moieties. This indicates that disodium arsenate heptahydrate induces certain permanent non-reversible damages including altered mucogenic activity in the epidermis of the skin of C. batrachus.
    Keywords: Clarias batrachus, disodium arsenate heptahydrate, histopathology, recovery, skin epidermis, toxicity
  • H. Movahedyan, A. Assadi, M. M. Amin Page 225
    Chlorinated phenols in many industrial effluents are usually difficult to be removed by conventional biological treatment processes. Performance of the aerobic sequencing batch reactor treating 4-chlorophenol containing wastewater at different loadings rates from 0.0075 to 1.2 g4CP/L.d was evaluated. The sequencing batch reactor was operated with fill, react, settle and decant phases in the order of 10:370:90:10 min, respectively, for a cycle time of 8 h at 10 days solid retention time and 16 h hydraulic retention time in the stable period. The effects of 4-chlorophenol loadings on the 4-chlorophenol and chemical oxygen demand removal percents, yield coefficient (Y), biomass variation and sludge volume index were investigated. High chemical oxygen demand removal efficiencies (95±3.5%) and approximately complete 4-chlorophenol removal (>99%) were observed even in the absence of growth substrate. The degradation of 4-chlorophenol led to formation of 5-chloro-2-hydroxymuconic semialdehyde, which was more oxidized, indicating complete disappearance of 4-chlorophenol via meta-cleavage pathway. A compact sludge with excellent settleability (sludge volume index=47±6.1 mL/g) developed during entire acclimation period. High removal efficiencies with sequencing batch reactor may be due to enforced short term unsteady state conditions coupled with periodic exposure of the microorganisms to defined process conditions which facilitate the required metabolic pathways for treating xenobiotics containing wastewater.
    Keywords: Sequencing batch reactor, 4, chlorophenol, biodegradation, organic loading, mixed culture, xenobiotic
  • R. Nabizadeh, N. Samadi, Z. Sadeghpour, M. Beikzadeh Page 235
    In this research the application of Nanosil containing hydrogen peroxide and silver was studied in disinfecting swimming pool water and it''s Environment. The effect of the disinfectant on Candida albicans (ATCC No. 10231), Aspergillus niger (ATCCNo. 16404), Pseudomonas aeruginosa (ATCC No. 9027), Serratia marcescens (PTCC No. 1111), Klebsiella pneumoniae (ATCC No. 10031) and Staphylococcus aureus (ATCC No. 29737) ) was evaluated. The main objective of this experiment was to determine the effective dose of Nanosil which could be used for disinfecting the environment of swimming pools and other surface area. Then, the effectiveness of Nanosil was studied in two private and one public swimming pools. Heterotrophic plate count, thermotolerant coliforms, Pseudomonas aeruginosa and Staphylococcus aureus were monitored as the target microorganisms in disinfection practice According to the result of this study, it is recommended to apply the Nanosil with the concentration of ≥3% (30000 mg/L) for contact time of 30 min or more for practical disinfection in swimming pools environment. The application of Nanosil in real conditions of two private and one public swimming pools indicated that the acceptable microbial quality is also achievable if the disinfectant residual concentration would be as high as 20 mg/L in swimming pool water.
    Keywords: Disinfection, swimming pool, hydrogen peroxide, silver
  • M. Delnavaz, B. Ayati, H. Ganjidoust Page 243
    Three moving bed biofilm reactors were used to treat synthesized wastewater of aromatic amine compounds including aniline, para-diaminobenzene and para-aminophenol that are found in many industrial wastewaters. The reactors with cylindrical shape had an internal diameter and an effective depth of 10 and 60 cm, respectively. The reactors were filled with light expanded clay aggregate as carriers and operated in an aerobic batch and continuous conditions. Evaluation of the reactors'' efficiency was done at different retention time of 8, 24, 48 and 72 h with an influent COD from 100 to 3500 mg/L (filling ratio of 50%). The maximum obtained removal efficiencies were 90% (influent COD=2000 mg/L), 87% (influent COD=1000 mg/L) and 75% (influent COD=750 mg/L) for aniline, para-diaminobenzene and para-aminophenol, respectively. In the study of decrease in filling ratio from 50 to 30 percent, 6% decrease for both para-diaminobenzene and para-aminophenol and 7% increase for aniline degradation were obtained. The removal efficiency was decreased to about 10% after 15 days of continuous loading for each of the above three substrates. In the shock loading test, initially the COD removal rate was decreased in all reactors, but after about 10 days, it has been approached to the previous values. Finally, biodegradability of aromatic amines has been proved by nuclear magnetic resonance system.
    Keywords: Light expanded clay aggregate, biodegradation, moving bed, biofilm, nuclear magnetic resonance
  • M. R. Shakibaie, A. Khosravan, A. Frahmand, S. Zare Page 251
    In this research, using mutation in the metal resistant bacteria, the bioremediation of the copper and zinc from copper factory effluents was investigated. Wastewater effluents from flocculation and rolling mill sections of a factory in the city of Kerman were collected and used for further experiments. 20 strains of Pseudomonas spp. were isolated from soil and effluents surrounding factory and identified by microbiological methods. Minimum inhibitory concentrations for copper (Cu) and zinc (Zn) were determined by agar dilution method. Those strains that exhibited highest minimum inhibitory concentrations values to the metals (5mM) were subjected to 400-3200 mg/L concentrations of the three mutagenic agents, acriflavine, acridine orange and ethidium bromide. After determination of subinhibitory concentrations, the minimum inhibitory concentrations values for copper and zinc metal ions were again determined, which showed more than 10 fold increase in minimum inhibitory concentrations value (10 mM for Cu and 20 mM for Zn) with P≤0.05. The atomic absorption spectroscopy of dried biomass obtained from resistant strains after exposure to mutagenic agents revealed that strains 13 accumulate the highest amount of intracellular copper (0.35% Cu/mg dried biomass) and strain 10 showed highest accumulation of zinc (0.3% Zn/mg dried biomass) respectively with P≤0.05. From above results it was concluded that the treatment of industrial waste containing heavy metals by artificially mutated bacteria may be appropriate solution for effluent disposal problems.
    Keywords: Pollution, bioremediation, copper and zinc waste effluents, pseudomonas
  • A. Naghizadeh, A. H. Mahvi, F. Vaezi, K. Naddafi Page 257
    The membrane bioreactor technology has been proven to be a single step process in efficient treatment ofwastewater, either directly or after pretreatment by reverse osmosis. In this study, a pilot scale experimentwas studied to treat a synthetic municipal wastewater sample. The aerobic reactor with a submergedmembrane used in this work was continuously aerated for organic matter oxidation, nitrification andphosphorous uptake as well as for fouling control. The mixed liquor was recycled from the aerated zone
    to the anoxic zone for denitrification. The membrane had a nominal pore size of 0.1 μm and a filtrationarea of 4.0 m2. The performance of submerged membrane bioreactor was examined in order to determinethe removal efficiency of organic compounds and nitrogen in different solid retention times (10, 20, 30,and 40 days) under a continuous inflow of the synthetic municipal wastewater. Results indicated that thesubmerged membrane bioreactor could efficiently remove the pollutants. Average removal rates of
    chemical oxygen demand, total Kejeldahl nitrogen removal, total nitrogen and phosphorous reached to ashigh as 99.3%, 98.1%, 85.5%, and 52%, respectively. Furthermore, concentrations of nitrate and nitrite inthe last stage were well reduced and reached to 5.3 and 0.047 mg/L, respectively.
    Keywords: Membrane bioreactor, wastewater treatment, solid retention time
  • EFFECTS OF CLIMATE CHANGE PROCESS ON COMFORT CLIMATE IN SHIRAZ STATION
    A. Shakoor, Gh. R. Roshan, F. Khoshakhlagh, Z. Hejazizadeh Page 269
    Dwelling in cities and city development together with quick increase of population and development of industrial activities with unplanned consumption of fossil fuel have intensively increased pollutions with consequences which will cause different diseases in short period, will lead to some climatic oscillations and its environmental effects such as the change of desirable periods in view of comfort climate in long period. The objective point of view of this research was to study the climate in Shiraz and its effect on comfort conditions for human physiology. In this research, using 55-year climatic data (1952-2006), the relative humidity and temperature through the application Guni comfort climatic model, the desirable months for the comfort of human physiology have been determined in the five 11-year periods and the linear process of these changes have been estimated for the next 11 years. The results of this research show that the temperature trend in Shiraz station is increasing and most months have heating process in a way that it is expected that in the coming future, the cold months will have more favoring conditions for physiological comfort of residents and correspondingly in the warm months, heating tension will have remarkable increase.
    Keywords: Climate change, comfort climate, bioclimatic diagram, Shiraz
  • A. R. Asgari, F. Vaezi, S. Nasseri, O. D&oumlrdelmann, A. H. Mahvi, E. Dehghani Fard Page 277
    Removal of chromium can be accomplished by various methods but none of them is cost-effective in meeting drinking water standards. For this study, granular ferric hydroxide was used as adsorbent for removal of hexavalent chromium. Besides, the effects of changing contact time, pH and concentrations of competitive anions were determined for different amounts of granular ferric hydroxide. It was found that granular ferric hydroxide has a high capacity for adsorption of hexavalent chromium from water at pH≤ 7 and in 90 min contact time. Maximum adsorption capacity was determined to be 0. 788 mg Crë granular ferric hydroxide. Although relatively good adsorption of sulfate and chloride had been specified in this study, the interfering effects of these two anions had not been detected in concentrations of 200 and 400 mg/L. The absorbability of hexavalent chromium by granular ferric hydroxide could be expressed by Freundlich isotherm with R2>0. 968. However, the disadvantage was that the iron concentration in water was increased by the granular ferric hydroxide. Nevertheless, granular ferric hydroxide is a promising adsorbent for chromium removal, even in the presence of other interfering compounds, because granular ferric hydroxide treatment can easily be accomplished and removal of excess iron is a simple practice for conventional water treatment plants. Thus, this method could be regarded as a safe and convenient solution to the problem of chromium-polluted water resources.
    Keywords: Adsorption, hexavalent chromium, drinking water treatment, granular ferric hydroxide
  • A. R. Koohpaei, S. J. Shahtaheri, M. R. Ganjali, A. Rahimi Forushani Page 283
    Solid phase extraction is one of the major applications of molecularly imprinted polymers fields for clean-up of environmental and biological samples namely molecularly imprinted solid-phase extraction. In this study, solid phase extraction using the imprinted polymer has been optimized with the experimental design approach for a triazine herbicide, named atrazine with regard to the critical factors which influence the molecular imprinted solid phase extraction efficiency such as sample pH, concentration, flow-rate, volume, elution solvent, washing solvent and sorbent mass. Optimization methods that involve changing one factor at a time can be laborious. A novel approach for the optimization of imprinted solid-phase extraction using chemometrics is described. The factors were evaluated statistically and also validated with spiked water samples and showed a good reproducibility over six consecutive days as well as six within-day experiments. Also, in order to the evaluate efficiency of the optimized molecularly imprinted solid-phase extraction protocols, enrichment capacity, reusability and cross-reactivity of cartridges have been also evaluated. Finally, selective molecularly imprinted solid-phase extraction of atrazine was successfully demonstrated with a recovery above 90% for spiked drinking water samples. It was concluded that the chemometrics is frequently employed for analytical method optimization and based on the obtained results, it is believed that the central composite design could prove beneficial for aiding the molecularly imprinted polymer and molecularly imprinted solid-phase extraction development.
    Keywords: Imprinted solid, phase extraction, chemometrics, herbicides, atrazine
  • S. Nasseri, T. Sadeghi, F. Vaezi, K. Naddafi Page 297
    Recent advances in wastewater treatment have resulted in production of well-treated effluents which are suitable for use in more different sectors. In fact, these reclaimed wastewaters would be regarded as new water resources in many regions. In this research, the area studied was the city of Ardebil in northwest of Iran. At present, the effluent of Ardebil wastewater treatment plant is discharged into Qaresoo River. In this study, different aspects of Ardebil wastewater reuse have been investigated. Sampling of the effluent was performed in winter 2006 and summer 2007; and parameters indicating the suitability of wastewater discharge and/or reuse were considered in accordance to the recommendations of Iran Department of Environment. All the analyses were accomplished according to the latest edition of standard methods. Results clearly showed that apart from the problem of total and fecal coliforms which were above the standard values( 1000 MPN and 400 MPN per 100 mL) the reuse of the treated effluent in agricultural irrigation could be carried out without restriction. But, regarding the discharge of this effluent into surface waters and injection wells, it would be necessary to upgrade treatment processes for further reduction of a few parameters such as nitrate, ammonium and phosphate.
    Keywords: Wastewater treatment, water reuse, agricultural irrigation, Ardebil
  • A. Rezaee, Gh. H. Pourtaghi, A. Khavanin, R. Sarraf Mamoory, M. T. Ghaneian, H. Godini Page 305
    Volatile organic compounds are considered as a group of major environmental pollutants and toluene is recognized as one of the representatives. In this research, the photocatalytic activity for toluene removal was studied over TiO2 nanoparticles embeded on activated carbon. Laboratory-scale experiments were conducted in a fixed-bed reactor equipped with 4 w and 8 w UV lamps (peak wavelength at 365 nm) to determine the oxidation rates of toluene. The photocatalyst was extensively characterized by means of X- ray diffraction and scan electronmicroscopy. Experiments were conducted under general laboratory temperature (25ºC±2) while the irradiation was provided by the UV lamps. The dependence of the reaction rate on light intensity as well as the deactivation of the catalyst were determined. The results indicated that the rate of the photocatalytic process increased with increasing the intensity of UV irradiation. Using the UV-A lamps, the decomposition rate of toluene was 98%. The stabilized photocatalyst presented remarkable stability (no deactivation and excellent repeatability). The catalyst could be regenerated by UV irradiation in the absence of gas phase. The control experiments confirmed that the photocatalytic effects of toluene onto the TiO2/activated carbon catalysts in the dark conditions were negligible. Reproducibility tests proved that the photocatalytic activity of the photocatalyst remains intact even after several experiments of new added toluene quantities. The study demonstrated that the TiO2/activated carbon catalyst may be a practical and promising way to degrade the toluene under ultraviolet irradiation.
    Keywords: Toluene, TiO2 nanoparticles, activated carbon, photocatalytic, coating