Archives of Hygiene Sciences
Volume:2 Issue: 3, Summer 2013

Background & Aims of the Study: The pollution of water resources due to the disposal of heavy metals has been an increasing worldwide concern for the last few decades. The removal of pollutants from water and wastewater is a problem that has grown with rapid industrialization. The discharge of toxic metals into watercourses is a serious pollution problem, which may affect the quality of water supply. By confirming the toxic effects of these metals, various methods have been implemented to remove pollutants from aqueous solutions. The aim of this study was determining the removal efficiency of natural adsorbents for removing heavy metals from aquatic solutions. In this review study, 39 experiments from 23 published papers on the mentioned topic between 2000 and 2011 were selected and the effective parameters on removal efficiency were studied and concluded. The average removal efficiency was 88.14%. In more than 65% of studies the removal efficiency was above 90%. In more than 96% of experiments, by increasing the adsorbent dose, the removal of heavy metals increased. Average optimum pH for maximum adsorption of heavy metal ions was 5.47, and the removal efficiency at acidic pH was allocated 76.92%. Twenty four experiments have examined the effect of contact time on the removal efficiency, which with increasing time to reach equilibrium time, the removal efficiency increased. In 16 studies, primary concentration was investigated, which by increasing concentrations of heavy metals, removal efficiency decreased. 58.97% of data were compatible with Langmuir isotherm. According to the results, sawdust can be used as a low cost, natural and abundant availability adsorbent for removal of heavy metal ions from aqueous solution.

Background & Aims of the Study: Increasing hazardous industrial wastes and lack of necessary regulations for management of them have led to serious problems in some parts of Iran. The aim of this study was to evaluate the situation of collection, transportation, recycling, and disposal of hazardous industrial wastes in the Khazra Industrial Park of Kerman, Iran. This study was a descriptive cross-sectional study that was done using questionnaires and local visits during year 2009. In this questionnaire, some information about the industrial wastes, production, storage on site, collection, transformation, sorting, recycling, and disposal were recorded. In the Khazra Industrial Park, 71,600 kg/day of different industrial waste is produced. The biggest proportion of waste includes metals, and construction and demolition waste which are about 16,500 tons a year. The smallest proportion is non-iron metal waste, which is produced at a rate of 8 tons per year. 88.7 percent of the active industries at the Khazra Industrial Park produce solid industrial waste. Most of the industrial units do not use a united and coordinated system for storing waste and have no specific place for temporary storage inside the industrial park. The majority of industrial waste collection, which is about 59.8%, is done by private contractors. The industrial units transfer their waste separately, and just 9 industrial units recycle their waste. Disposal of these wastes is mainly done by selling to trading agencies. Each day, 3 tons of hazardous industrial waste is produced in this park. The highest production belongs to the oil factory (Keyhan Motor). According to the results, the Khazra Industrial Park needs a unified system for storing, transporting and collecting the sorted waste, and it also needs to have a transportation station with basic facilities. The wastes of most industrial units at the Khazra Industrial Park have the potential for recycling and re-usage in other industries. The best, most economic, and most environment-friendly waste management activity of the Khazra Industrial Park is prevention of production, increase in the potential of recycling, and reuse of material with emphasis on sorting at the production site, increase of mechanical sorting, and decrease in production of disposable waste.

Background & Aims of the Study: The use of urban wastewater in agriculture is receiving renewed attention with the increasing scarcity of freshwater resources in many arid and semiarid areas, despite its associated health and environmental risks. Long term wastewater usage for irrigation results in accumulation of heavy metal in soils and plants. So, due to the environmental and health risks associated with wastewater irrigation, this study was carried out to investigate heavy metals in the Wastewater Treatment Plant effluent in Isfahan. A duplicate sample of treated wastewater was taken from Isfahan''s North wastewater treatment plant (WWTP) in winter season. Then, examination was accomplished according to Standard Methods for the Examination of Water and Wastewater. Results compared with Iran standard for wastewater reuse in irrigation. In this study, there was no cadmium (Cd) and chromium (Cr) in the effluent, and the mean concentration of lead (Pb), nickel (Ni), zinc (Zn) and copper (Cu) content was 0.008 and 0.004, 0.028 and 0.018 mg/L, respectively. The Iranian standard content of Cd, Cr, Pb, Ni, Zn, and Cu for irrigation are 0.05, 1, 1, 2, 2 and 0.2 mg/L. The results of this study indicate that the mean contents of Cd, Cr, Pb, Ni, Zn, and Cu in the effluent of Isfahan North WWTP was in safe range for use in agricultural irrigation. All of them were lower than the allowable limit suggested by the standard of Iran.

Background & Aims of the Study: In order to design membrane bioreactors (MBR) properly, it is essential to comprehend the behavior of microorganisms in such wastewater treatment processes. In this study, a lab-scale MBR process was operated to determine the biokinetic coefficients of the MBR system under different MLSS concentrations of 6800, 7000, 7400, and 7800 mg/l and organic loading rates of 0.5 kg COD/m3/day. The results of this study showed that the yield of microorganisms (Y), the endogenous decay coefficient (kd), the maximum specific growth rate (μmax) and the saturation constant (Ks) were in the range of 0.67 g VSS/g COD, 0.56 d−1, 1.86 d−1 and 6.65 mg COD/l, respectively. The kinetic coefficients in this study can be used to improve the operation and design the MBR system in full scale.

Background & Aims of the Study: Organic dyes with a complex structure are often toxic, carcinogenic, mutagenic, non-biodegradation and stable in the environment and if released to the environment without treatment can endanger the environment and human health. The aim of this study was to evaluate the performance of H2O2 and H2O2/Fe0 Iron in removal of dye Acid Red 18 from aqueous solutions. This study was conducted at the laboratory scale. In this study, the removal efficiency of Acid Red 18 from a synthetic solution by H2O2 and H2O2/Fe0 was investigated. As well as Effect of solution pH, dye concentration, Concentration of Nanoscale Zero-Valent Iron, H2O2 and contact time in decolorization efficiency was investigated. Results show that in pH=3, Contact time of 80 minutes, dye concentration of 50 mg/l and Concentration of Nanoscale Zero-Valent Iron of 2 g/l and H2O2 concentration equal to 200 mmol/l, the removal efficiency was about 98%. According to the results of experiments, H2O2/Fe0 has high efficiency in removal of Acid Red 18 from aqueous solution.