Iranian Journal of Environmental Health Science and Engineering
Volume:7 Issue: 4, Autumn 2010

Bioremediation of metal pollutants from industrial wastewater using metal resistant bacteria is a very important aspect of environmental biotechnology. In this study, three species of Pseudomonas aeruginosa were isolated from active sludge of a food factory in the city of Kerman. The bacterial identity was determined by various biochemical tests. Among them, isolate number one could grow on Muller-Hinton agar medium containing 6mM cadmium ion (Cd2+) and was therefore selected for further study. The isolates were subjected to mutation by two mutagenic agents (Acridine Orange and Acriflavine) using gradient plate and SIC techniques. The Minimum Inhibitory Concentration of Cd2+ for the isolate one after mutation was increased to 7mM. Removal of Cd2+ using mutated and wild type strains of this bacterium was carried out at different time intervals (10-300 minutes). It was observed that within 60 minutes, 94.7% of cadmium was removed in 30mg/L of Cd2+ solution. However, with 60mg/L Cd2+ solution, only 53.58% and 38.68% Cd2+ removed were achieved by mutated and wild type bacteria, respectively. The equilibrium data was fitted by Langmuir isotherm equation and the related parameters for Cd+2 were derived. Based on the data obtained in this study, it can be concluded that biomass of this bacterium can be used for bioremediation of cadmium from industrial waste processing plants with high efficiency.

The main objective of this study was to investigate the effect of cadmium (II) and copper (II) salts concentrations on uptake, tolerance, growth pattern and metallothionein induction as a biomarker by two bacterial strains including Pseudomonas aeruginosa and Pseudomonas putida PTCC 1694. For this purpose, the minimum inhibition concentration, minimum bactericidal concentration, growth and uptake patterns of Pseudomonas aeruginosa and Pseudomonas putida were determined in culture media with 0.09-10mM/L of Cd and Cu salts in pH7±0.2= at 30±2 ºC. Growth rate and amount of metal uptake were determined by spectrophotometer and atomic absorption assay every 24 hours for 14 to 23 days. Biosorption of the heavy metals on the bacterial cell-wall surfaces after preparation were analyzed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). Metallothionein production was evaluated by silver saturation methods. The results showed that the growth was directly inhibited at the concentration of 1.5 mM/L Cd(II) and 9 mM/L Cu(II) for P. aeruginosa and 0.95 mM/L Cd(II) and 7.5 mM/L Cu(II) for P. putida. Results of the growth pattern showed that the log phase for Pseudomonas aeruginosa and Pseudomonas putida lasted 48 and 121 hours, 217 and 121 in presence of cadmium and copper, respectively. The stationary phase was very short and very soon after log phase, the microorganisms went into death phase. The maximum biosorption of metal from cultures of two strains was 36.6% and 28% of cadmium and 80% and 47% of copper of final concentration. The result of elemental analysis with SEM-EDS approved surface adsorption of cadmium and copper. Since the exact number of Ag-binding sites per metallothionein molecules is unknown for Pseudomonas putida, results were expressed as nanomoles of Ag-binding site per gram of wet weight as equal to 0.0033 and 0.0031.

Aquatic macrophytes are known to accumulate various heavy metals in their biomass. This accumulation is often accompanied by physiological changes which can be used in biomonitoring for aquatic pollution. In this study, the impact of copper (Cu) on the growth of the duckweed Lemna minor, followed by its removal, was studied with 0.1-1.0 mg/L of Cu in a quarter Coïc and Lesaint solution at pH=6.1. In order to verify duckweed tolerance to Cu, photosynthesis was measured at the maximal concentration which caused no effect on the plant growth. The results showed that copper inhibited Lemna growth at concentrations ≥ 0.3 mg/L. At 0.2 mg/L, the final biomass was approximately four times greater than the initial biomass. Analysis of metal concentration in water showed that Lemna minor was responsible for the removal of 26% of Cu from the solution. In the presence of Cu, respiration was reduced, while photosynthesis increased considerably. Net photosynthesis approximately increased three times compared to the control. Copper was responsible for 130-290% increase in the photosynthetic activities. These results suggested that Lemna minor could be a good tool for the evaluation of copper pollution in biomonitoring programs.

Sonochemical degradation of different compounds such as chlorinated aliphatic hydrocarbons is one of the recent advanced oxidation processes and it may be effective for removing low concentration organic pollutants from aqueous streams. Trichloroethylene (TCE) is one of these compounds that is mainly used as a degreaser. Important studies about TCE sonolysis have been focused at millimolar levels and natural pH, but in this study the ultrasonic degradation of TCE at different micromolar initial concentrations (30, 300 and 3000 μg/L) and 4 different initial pH with a 35 kHz frequency was investigated. Furthermore, the degradation of TCE by ultrasound with different concentrations of hydrogen peroxide at pH= 7 was also performed. Gas chromatography with FID detector was used for analyses of TCE. Results showed that the degradation of TCE increased with decrease in the initial concentration of TCE from 3000 to 30 μg/L at all initial pH. Initial pH of solution and different concentrations of H2O2 did not affect significantly the TCE destruction.

The aim of this study was to isolate and characterize a high efficiency denitrifier bacterium for reducing nitrate in wastewater. Six denitrifier bacteria with nitrate removal activities were isolated from a petrochemical industry effluent with high salinity and high nitrogen concentrations without treatment. The isolated bacteria were tested for nitrate reomoval activity. One of the bacterium displayed the highest reduction of nitrate. The strain was preliminarily identified using biochemical tests and further identified based on similarity of PCR-16S rRNA using universal primers. Biochemical and molecular experiments showed that the best bacterium with high nitrate removal potential was Pseudomonas stutzeri, a member of the α subclass of the class Proteobacteria. The extent of nitrate removal efficiency was 99% at 200 mg/L NO3 and the nitrite content of the effluent was in the prescribed limit. The experiments showed the ability of Pseudomonas stutzeri to rapidly remove nitrate under anoxic conditions. The strain showed to be potentially good candidate for biodenitrification of high nitrate solutions.

Oil pollution is a worldwide threat to the environment and the remediation of oil-contaminated soils, sediments and water is a major challenge for environmental research. Bioremediation is a useful method for soil remediation, if pollutant concentrations are moderate and non-biological techniques are not economical. The bioremediation consists strategy of actively aerating the soils and adding fertilizer in order to promote oil biodegradation by indigenous microorganisms. The objective of this study was to investigate whether agricultural fertilizers (N, P, K) enhance the microbial degradation of petroleum hydrocarbons in soil. Artificially polluted soil with %1density of crude oil was used and then fertilizers were applied in 3 levels of 0, 1 and 2 ton/ha in 3 replicates. The soils were kept in 30 ºC and 60 percent of field capacity condition for 5 to 10 weeks. To provide the necessary aeration, the soils were tilled twice a week by shovel. Soil sample were analyzed for hydrocarbon-degrading heterophic bacteria count and some soil chemical properties. Residual oil was measured by oil soxhlet extraction method, and gas chromatography. The results showed that the hydrocarbon-degrading and heterotrophic bacteria count in all the treatments increased with time and heterotrophic bacteria population increased from 6×103 cfu/g soil to 1.4×108 cfu/g soil. Also, soil C/N ratio decreased from 6 to 3. The results indicated that the applied fertilizer increased the degradation of the hydrocarbons compared with the control. Gas chromatography results showed that normal paraffin and isopernoid (Phitane and Pristane) decreased in the range of 45 to 60 percent in all treatments. Furthermore, the results showed that the application of fertilizers at 2 ton/ha rate in oil-contaminated soil lead to greater rates of biodegradation after 5 weeks indicating the feasibility of bioremediation.

Acrylonitrile is used as the main raw material for manufacturing acrylonitrile butadiene styrene resin. It is usually found as pollutant in the petrochemical wastewater. In this research an aerated submerged fixed-film reactor was developed to treat a synthetic acrylonitrile butadiene styrene unit wastewater containing acrylonitrile. Laboratory experiments were conducted using a bioreactor with 44.2 L capacity operated at different hydraulic and organic loading rates. Stationary submerged biofilms were attached to net-type media (polypropylene) under diffused aeration. The specific surface area and porosity of media were 324 m2/m3 and 87%, respectively. In the first phase the reactor was operated in hydraulic retention times of 9, 7, 5 and 4 h with soluble chemical oxygen demand of 300 mg/L. Then the experiments were continued with the constant retention time of 4 h and variable chemical oxygen demand concentrations of 350, 400 and 450 mg/L. In stable condition of operation and loading rates of 0.8 to 2.4 kg/m3d the removal efficiencies of reactor for soluble chemical oxygen demand reached to 95 to 99%. At the organic loading rate up to 2.4 kg/m3d the soluble chemical oxygen demand was less than 50 mg/L which was lower than the Iranian national discharge standards (chemical oxygen demand<60 mg/L). The increase of organic and surface loading to 2.7 kg/m3d and 23.16 g/m2d, respectively, caused the system becoming unstable and the soluble chemical oxygen demand removal efficiency decreased to 66%. Finally, the kinetic coefficients of the aerated submerged fixed-film reactor for treating of acrylonitrile were determined using a separate pilot unit. According to the results, it was concluded that the aerated submerged fixed-film reactor can be used as suitable approaches for treating of petrochemical effluents contain acrylonitrile.

Sampling of triethylamine in the cold-box unit in an auto-manufacturing company in Iran has indicated the average concentration of 430 mg/m3 in the emission duct. In this study a biotrickling filter was used for treatment of triethylamine in air stream. Triethylamine removal efficiency (K/L) pattern was evaluated by changing volumetric loading (L), superficial gas velocity (Uo), empty bed gas retention time (EBRT) and recirculation liquid flow rate (VL), while operating at constant temperature of 25 ± 1ºC. For finding the effect of EBRT on the triethylamine removal efficiency, tests were performed at EBRT of 156s, 52s and 31 s and a constant liquid recirculation velocity of 3.466 m3/m2/h. Results showded that for a test period of 65 days, triethylamine removal efficiencies of more than 98% were obtained for EBRT of 156 s and loading rates of less than 48 g/m3/h. With an EBRT of 52s removal efficiencies of > 90% were obtained for loadings of < 57 g/m3/h and maximum removal capacity was 53.4 g/m3/h at volumetric loading of 64 g/m3/h. Also with an EBRT of 31 s the maximum removal capacity was 53.6 g/m3/h at volumetric loading of 68 g/m3/h. Thus in the range of implemented EBRTs the proper absorption of triethylamine from gas to liquid phase took place and the elimination efficiency was shown to be dependent on microorganisms activity rate. The effect of liquid flow rate on the triethylamine removal efficiency was investigated by changing VL in the range of 3.46 to 10.40 m3/m2/h at EBRT=31 s and influent triethylamine concentration of 600 mg/m3. Results showed that the triethylamine removal efficiency was nearly independent of the liquid recirculation rate.

The industrial wastewater produced by urotropine plants is considered as a major environmental polluting factor and hence its treatment is required. In this work, strongly acidic cation exchange resins including C100H (Purolite), Amberlite IR120 and Amberlyst 15W were used for removing of urotropine from wastewater. Optimum conditions for the three resins and regeneration were studied. The required amounts of resins for efficient exchange of urotropine and amount of acid for regenerating process of exhausted resins were determined and the potential of these resins in removing of urotropine and ammonia from the wastewater were compared. It was found that C100H resin has a higher capability in removing of urotropine in comparison with tow other resins. This capability of C100H was 2 and 7 times greater than Amberlite IR120 and Amberlyst 15W, respectively. The comparison of results with other methods indicates that this method reduces urotropine concentration more effectively. The simple and fast conductometric method has been developed for determination of urotropine in wastewater in the presence of formaldehyde and ammonia without any interference.

In this research, the continuously operated laboratory scale Kaldnes (k1) moving bed biofilm reactors (MBBRs) under partial nitrification-denitrification process were used for treatment of synthetic wastewater containing ammonium and glucose. The Anoxic and Aerobic reactors were filled to 40 and 50 %(v/v) to attach and retain biomass with k1 biofilm carriers, respectively. The favorite internal recycle ratio and hydraulic residence time (HRT) to eliminate nitrogen compounds were 300% of inflow rate and 20 hours, respectively. Optimal dissolved oxygen (DO) was 1-1.5 mg/L in the aerobic reactor. No sludge was returned into the system and only an internal recycling was performed from aerobic to anoxic reactor. The results showed that the maximum and average specific nitrification rate (SNR) in the aerobic reactor were 49.4 and 16.6 g NOx-N/KgVSS.day, respectively and the maximum and average specific denitrification rate (SDNR) as 156.8 and 40.1gNOx-N/KgVSS.day in the anoxic reactor, respectively. The results also showed that it is possible to reach a stable partial nitrification with high ratio of NO2-N/NOx-N (80% to 85%) during high load ammonium and low DO concentration (<1.5 mg/L) in the aerobic reactor. During optimum conditions, the average removal efficiency of total nitrogen (TN), ammonia and soluble organic carbon (SCOD) occurred as 98.23%, 99.75% and 99.4%, respectively. This study showed that the partial nitrification/denitrification process in the moving bed biofilm reactors system has an acceptable performance for treatment of wastewater with high load of organic carbon and organic nitrogen compounds.

Noise pollution has a detrimental effect upon the learning and attainments of school children. Poor acoustical condition and high noise levels can cause many problems for the instructors and students. The acoustical indices and conditions of classrooms are important factors in the learning achievement of students. The purpose of this study was to find the relations of noise levels in indoor/outdoor and acoustical conditions of classrooms. Noise measurements and acoustical indices of 244 classrooms in 90 random samples consisting of primary, secondary and high schools in Tehran were considered. It was found that the average equivalent noise levels inside classrooms and corridors, yards and street sides in teaching condition were 72 dB(A), 65.8 dB(A), 64.1 dB(A) and 64.5 dB(A), respectively. Deference between mean indoor LAeq and background noise level in teaching conditions (above 32 dB) indicates that outdoor district noise sources could not significant affect indoor noise levels (P = 0.521). Comparison of means between equivalent noise level in classrooms of boy schools with girl schools showed a significant difference (P=0.0001). For the case of classrooms in primary, secondary and high school this Comparison had a significant deference (P=0.0001). Site selection, improving acoustic quality, controlling opening in doors and windows and educating noise reduction for studied schools were proposed.