فصلنامه سلامت و محیط زیست
سال پنجم شماره 4 (پیاپی 18، زمستان 1391)

Contamination of drinking water sources with nitrate may cause adverse effects on human health. Due to operational and maintenance problems of physicochemical nitrate removal processes, using biological denitrification processes have been performed. The aim of this study is to evaluate nitrate removal efficiency from drinking water using autotrophic denitrifying bacteria immobilized on sulfur impregnated activated carbon in a fluidized bed bioreactor. After impregnating activated carbon by sulfur as a microorganism carriers and enrichment and inoculation of denitrifying bacteria, a laboratory-scale fluidized bed bioreactor was operated. Nitrate removal efficiency, nitrite, turbidity, hardness and TOC in the effluent were examined during the whole experiment under various conditions including constant influent nitrate concentration as 90 mg NO3--N/l corresponding to different HRT ranging from 5.53 to 1.5 hr. We found that the denitrification rates was depended on the hydraulic retention time and the nitrate removal efficiency was up to 98% and nitrite concentration was lower than 1mg/l at optimum HRT=2.4 hr respectively. Moreover, there was no difference in hardness between influent and effluent due to supplying sodium bicarbonate as carbon source for denitrifying bacteria. However pH, TOC, hardness, and turbidity of the effluent met the W.H.O guidelines for drinking water. This study demonstrated that an innovative carrier as sulfur impregnated activated carbon could be used as both the biofilm carrier and energy source for treating nitrate contaminated drinking water in the lab-scale fluidized bed bioreactor.

The poor accessibility of microorganisms to PAHs in soil has limited success in the process of bioremediation as an effective method for removing pollutants from soils. Different physicochemical factors are effective on the rate of biodegradation. The main objective of this study is to assess effects of nutrient and salinity on phenanthrene removal from polluted soils.The soil having no organic and microbial pollution was first artificially polluted with phenanthrene then nutrients and salinity solution in two concentrations were added to it in order to have the proportion of 10% w:v (soil: water). After that a microbial mixture enable to degrade phenanthrene was added to the slurry and was aerated. Finally, the residual concentration of Phenanthrene in the soil was extracted by ultrasonic and was analyzed using GC. We measured the microbial populationusing MPN test. This study was conducted based on the two level full factorial design of experiment. MPN test showed that the trend of microbial growth has experienced a lag growth. The full factorial design indicated that nutrient had the maximum effect on bioremediation; the rate of phenanthrene removal in the maximum nutrients - minimum salinity solution was 75.14%. This study revealed that the more nutrient concentration increases, the more degradation will be happened by microorganisms in the soils. However, salinity in the concentration used had no effect on inhabitation or promoting on the Phenanthrene removal.

Cyanide is a toxic pollutant existing in the various industrial effluents such as iron and steel، coal mining، non-ferrous metals manufacturing and metal plating. Its presence in water resources and wastewater، as serious hazardous substances leads to undesirable effects on both the environment and human. Thus، its concentration control is essential for human health. The main goal of this study was to evaluate Fenton process efficiency in cyanide removal from aqueous solution.

This is an experimental study Conducted at Lab scale in a batch system. We investigated effect of different variables including; pH، mole ratio of Fe2+/ H2O2، contact time، and initial concentration of cyanide. Data were analyzed using Excel software.

We found that cyanide with initial concentrations of 0. 4 mM/L was reduced by 92 %. This removal result was related to oxidizing agent of hydroxyl radicals under optimum conditions including; pH = 4، molar ratio Fe2+/ H2O2= 0. 046 (Fe2+=0. 27 mM/L) after 6o min reaction time. An increase in reaction time was not improved cyanide removal efficiency. Moreover، the Fenton process efficiency in cyanide removal decreased from 92 to 60 %، by increasing the initial cyanide concentration from 0. 4 to 0. 6 mM/L.

It can be concluded that Fenton oxidation Process can be considered as a suitable alternative for cyanide removal to achieve environmental standards.

Synthetic dyes represent one of the largest groups of pollutants in wastewater of dying industries. Discharging these wastewaters into receiving streams not only affects the aesthetic but also reduces photosynthetic activity. Electrochemical advanced oxidation processes such as Electro-Fenton process are low operational and have high mineralization degree of pollutants. In this study, we investigated affective factors in this process to determine the optimum conditions for dye and COD removal from aqueous solutions containing Reactive Blue 19 dye. Synthetic samples containing Reactive Blue 19 dye were prepared by dissolving dye powder in double distilled water. and the the solution prepared was transferred into pilot electrochemical cell having two anode and cathode electrode made of iron and carbon. Electro-Fenton process was began by adding of Fe2+ ions and establishing electrical potential difference. After testing and at specified time intervals, each sample was collected from the pilot cell, and process performance was evaluated through measuring dye concentration and COD. Based on the results obtained, optimum conditions of Electro-Fenton process for dye and COD removal was determined. Accordingly, potential difference of 20 volt for dye concentration up to 100 mg/L and potential difference of 30 volt for dye concentration of more than 200 mg/L, reaction time 60 minutes, 0.5 mg/L of Fe2+ concentration and suitable pH for the maximum dye removal efficiency equaled 4 respectively. Under such conditions, the dye and COD removal was 100 and 95% respectively. Based on the results obtained, it was revealed that Electro-Fenton process has significant ability in not only dye removal but also in COD removal. Accordingly, it was found that the effective parameters in Electro-Fenton process for removal Reactive Blue19 dye are electric potential difference, concentration of iron ions and electrolysis time.

Phenol is one of the most important organic chemicals presenting in water and other environments. It not only brings about hygienic problems but also results in forming 11 toxic priority pollutants in aqueous environments. Hence, the performance of electrocoagulation process using iron and aluminum sacrificial anodes was investigated for removal of phenol.

We used a glass tank in 1.56 L volume (effective volume 1 L) equipped with four iron and aluminum plate electrodes to do experiments (bipolar mode). The tank was filled with synthetic wastewater containing phenol in concentration of 5, 20, 40, and 70 mg/l and to follow the progress of the treatment, each sample was taken at 20 min intervals for up to 80 min. The percent of phenol removal was measured at pH 3, 5, 7, and 9; electrical potential range of 20, 40, and 60 volts; and electrical conductivity of 1000, 1500, 2000, and 3000 µs/cm.

It was found that the most effective removal capacities of phenol (95 and 98 %) could be achieved when the pH was kept 7 and 5 for iron and aluminum electrodes, reaction time 80 min, electrical conductivity 3000 µs/cm, initial concentration of phenol 5 mg/l, and electrical potential in the range of 20-60 V.

The method was found to be highly efficient and relatively fast compared with existing conventional techniques and also it can be concluded that the electrochemical process has the potential to be utilized for the cost-effective removal of phenol from water and wastewater.

Colored wastewaters are known as one of the most important sources of environmental pollutants. Having toxic chemicals and aesthetic problems has made treatment of these wastewaters very crucial. So far a number of methods such as electrochemical treatment, coagulation and flocculation, and adsorption have been used for treatment of textile industries wastewater. Hence, the efficiency of zero-valent iron powder in the presence of UV light and hydrogen peroxide to remove Acid Orange 7 and Reactive Black 5 from the synthetic solutions was investigated. Conducting all experiments in a batch reactor, we examined different parameters including initial concentration of the color (25, 50, 75 mg/L), contact time (30, 60, 120 min), pH (3, 7, 11), the amount of iron powder (0.6, 1.3, 2 g/l), and hydrogen peroxide concentration (10, 15, 20 ml/l). The results showed that dye removal efficiency was increased by increasing contact time, the amount of iron powder and hydrogen peroxide concentration. On the other hand, with the increasing pH and initial concentration of dye, removal efficiency decreased in both AO7and RB5 dyes. We found that the integrated ZVI/UV/H2O2 method has high efficiency in removing azo dyes Acid Orange 7 and Reactive Black 5.

Azolla Filiculoides as a non-living fern was used in a batch system to remove "Basic Blue 3", which is a cationic dye and a carcinogenic agent. We used a batch system by applying certain concentrations of dye contaminant and in the presence of a certain amount of adsorbent under optimum conditions. The main groups presenting in the Azolla cell wall were evaluated by acidification and alkalization of Azolla's media and then potentiometric titration with standard basic and acidic solutions. It was observed that the removal efficiency of dye using non-living Azolla in accordance with the Langmuir isotherms was 82% for the initial dye concentration of 200 mg/lit under reaction conditions consisting of contact time 6 h, pH= 6, temperature 25 ˚C, and dose 5 g/lit. Qmax (maximum uptake capacity) by the activated Azolla at three temperatures 5, 25 and 50 ˚C was 0.732, 0.934, and 1.176 mmol/g respectively. ΔG (Gibbs free energy changes) was obtained for these temperatures as -0.457, -0.762, and -1.185 kJ/mol respectively. Removal of basic blue 3 using Azolla is an economically and effective method.

Antibiotics are potential pollutants that represent an important environmental problem because of their toxic effects on the food chain and aqueous streams. The objective of this research was to study the adsorption of penicillin G on to chestnut shell as an inexpensive adsorbent. This study was performed at laboratory scale and batch system. We studied the influence of process variables such as adsorbent dose, initial PEN G concentration, pH of solution, contact time, and breakthrough curves. In order to find out the possibility of reuse, desorption study was also carried out. The surface characteristics of adsorbent were investigated using Fourier Transform Infra-Red and Scanning electron microscope. Equilibrium study data were modeled using Langmuir, Freundlich, and D-R models. Moreover, kinetic studies were done by three models of pseudo first order, pseudo second order, and intra-particle diffusion.Resuls: The maximum PEN G removal achieved was 92%, at pH 3, adsorbent dose 0.1 g/l and contact time 120 min. The Langmuir equation (R2=0.99) provided the best fit for the experimental data. It was also found that adsorption of PEN G by chestnut shell followed pseudo- second order model (R2= 0.992). According to the results obtained, chestnut shell appears to be a suitable, low cost and efficient adsorbent for removing PEN G from waste streams.