Iranian Journal of Environmental Health Science and Engineering
Volume:8 Issue: 1, Winter 2011

In the present study the landfill leachate obtained from Tabriz Landfill site was first treated in a suspended growth activated sludge bioreactor which then was turned to a moving-bed biofilm bioreactor under thermophilic conditions (50ºC). The average Soluble Chemical Oxygen Demand (SCOD) removal ranged from 70% to 62% as Organic Loading Rate (OLR) increased from 0.454 to 4.678 kgCOD/(m3.d). Hydraulic Retention Time (HRT) values were set to 12, 14, 16.8, and 21 h. The recycle ratio of biomass ranged from 1 to 1.5. The total biomass concentration was in the range of 2600-3100 mg/L of which 60-65 percent was in the form of biofilm. It was COD removal efficiency was 5% to 10% higher in moving-bed biofilm operation compared to suspended growth one at the same OLR and HRT. Respirometry experiments revealed that readily biodegradable organic compounds accounted for 5.7% and 5.2% of substrate under thermophilic and mesophilic conditions, respectively. The maximum resulting oxygen uptake rates were 0.21 mgO2/(L.min) and 0.16 mgO2/(L.min) under thermophilic and mesophilic conditions, respectively.

The discharge of dye-bearing wastewater from textile industries into natural streams and rivers poses several problems. Some dyes are toxic to aquatic life, may damage aesthetic nature of the environment and are difficult to be treated by conventional methods. The present work investigated the photodecolorization of reactive dyes by solar nanophotocatalysis. Nano-TiO2 was prepared using a sol-gel method and their surface state was analyzed by X-ray diffractometer. Procion Reactive Red (H-E7B) and Procion Reactive Yellow (H-E6G) were used as model compounds. The effects of operational variables such as catalyst type and dose, pH, contact time, H2O2, anions (C1-, SO42- and CO32-), solar light intensity and catalyst reuse were investigated. The complete color removal was achieved at optimum conditions of catalyst dose of 160mg/L, pH=5.5 and contact time = 95 min for dye sample H-E7B and catalyst dose of 500 mg/L, pH=7.4 and contact time = 150 min for dye sample H-E6G, respectively. At optimum conditions, COD reduced from 120 mg/L to 23 mg/L and from 108 mg/L to 17 mg/L for the two types of dye, respectively. Kinetic analyses indicated that photocatalytic decolorization rate a followed a first-order model.

Biokinetic coefficients and efficiency for three activated sludge processes including conventional, extended aeration, and contact stabilization were determined in pilot-scale for six months in Isfahan south municipal wastewater treatment plant. These systems were operated under two different MLSS concentrations in aeration tank. For each MLSS, five periods were considered in base of flow rate and sludge retention time (SRT). The samples from the influent wastewater, reactor and effluent were collected periodically and experimented by the Standard Methods. The data were analyzed by the Excel and SPSS softwares. The investigation showed that the yield coefficient (Y), decay coefficient (kd), maximum specific growth rate and saturation constant (Ks) for conventional activated sludge process were in the range of 0. 48-0. 8 mgVSS/mg sCOD, 0. 0189-0. 026 1/day, 0. 95-0. 98 1/day and 52-71 mg sCOD/L, extended aeration: 0. 6174-1. 2512 mgVSS/mg sCOD0. 0198-0. 0309، 1/day 1. 96-3. 17، 1/day and 311. 7-508 mg sCOD/L and for contact stabilization: 0. 6322-0. 713 mgVSS/mg sCOD1 0. 0172-0. 0387، /d0. 23- 1 0. 42/d and13. 8-50. 8 mg sCOD/L, respectively. In the conventional and contact stabilization processes values of the coefficients were within the range of those reported in the literature. However, in the extended aeration process, values of Ks and Y in MLSS of 5000mg/L were out of ranges. The sensitivity analysis of changes in the biokinetic coefficients showed direct relationship of kd and Ks with the concentration of the effluent substrate. Whereas μmax is inversely related to concentration of the effluent substrate. In addition, regardless of the type of substrate and MLSS concentration, the effluent substrate concentration is more sensitive to μmax than kd and Ks. The results also showed a COD removal efficiency ranging for conventional process between 83 and 92. 5%, for extended aeration process between 88 and 93. 8%, and for contact stabilization process 77 and 92%. The effluent COD was simulated using the biokinetic coefficients determined during the study.

In this study, photocatalytic degradation of methylene blue was examined using different concentrations of TiO2 nano-particles (diameters less than 21 nm) and ultraviolet (UV-C) radiation in a tubular reactor. Different concentrations of catalyst (0.3-1.2 g/L), different pH conditions (3, 7 and 9) and dye concentration (15, 30 and 60 mg/L) as well as sample rotation level (125 mL/min) were studied. The sample passed 1-7 times through the quartz reactor exposed to UV-C ray (constant intensity = 2.8 mW/cm2) (every rotation time was 8 min). Results of this research showed clearly that methylene blue is significantly degradable by TiO2 and UV-C radiation. Increasing dye concentration resulted in decreased efficiency and thus, as more samples passed through quarts tube, removal efficiency increased. Methylene blue with concentration of 15 mg/L and after 7 rotations in the reactor (56 min) was removed with the efficiency of 98%. Subsequent to dye removal, 47% of initial COD decreased simultaneously.

Human health is closely related with the quality of drinking water. Various chemical pollutants in the drinking water can cause great risk to human health. Shizuishan city is an important coal-based industrial city where residents mainly rely on groundwater. In order to protect the safety of water supply, based on the sample survey, health risk assessment model recommended by the Unites States Environmental Protection Agency was adopted to assess the health risks of groundwater in the region. During the study, total 25 groundwater samples were colleted from drinking water supply wells and many parameters such as Cr6+, fluoride, arsenide, volatile phenol and cyanide were examined according to standard procedures recommended by Chinese Ministry of Water Resources. Evaluation results showed that the greatest risk value due to non-carcinogenic pollutants was caused by fluoride, while the greatest health risk due to chemical carcinogenic pollutants was primarily caused by Cr6+, the second was arsenide. The health risk due to chemical carcinogens was 3 magnitudes larger than that caused by non-carcinogenic pollutants, which indicated that chemical carcinogens were the primary pollutants in the drinking groundwater. The total health risk level was within the acceptable level proposed by Unites States Environmental Protection Agency, but exceeded the acceptable level recommended by International Commission on Radiologic Protection which meant that the groundwater needs pretreatment before consumption.

In this article the heavy metal concentrations in atmospheric wet precipitation and its relationship with the particles (PM10) in the air of the city of Zanjan are reported. Two hundreds samples of rain water and snow were collected with 45 particle samples collected monthly. Heavy metals in wet and dry samples were determined by atomic absorption spectrophotometery. The use of enrichment factors and correlation coefficients allowed us to predict the major sources of these metals. The ranges of concentration of Pb, Zn, Cr and Cd in rain water (μg/L) were 5.8-22.2, 29.26-70, 1.4-4 and 0.25-1.2, respectively. The results showed that the concentrations of Pb, Zn, Cr and Cd in wet precipitation and PM10 in samples collected in southern parts of the city where the traffic load and industrial activities are very high (zone 4), were 22.2, 70, 1.2 and 4(μg/L) and 840, 16233, 32 and 54.8 (ng/m3), respectively. These values were higher than those measured in the other parts of the city. Most of the calculated enrichment factors higher than 10 were attributed to the traffic and industrial activities. The enrichment factor and correlation coefficient values showed that the heavy metals in the air of Zanjan originate from similar sources. The concentration of particulate matter in 30 air samples of total 45 samples were found to be higher than 50μg/m3. The average concentrations of Pb and Cd in the city center and near the industrial complexes were higher than World Health Organization standards.

Centella asiatica is a herbaceous plant and known as pegaga in Malaysia. It was commonly used as a healing agent and constituent to improve mental ability because contains polyphenols and triterpenes. Malathion is an insecticide that helped to increase value and yields of Centella. asiatica by control the damage caused by crop pests. Study was done in MARDI Serdang to measure malathion residue in Centella. asiatica with different treatment methods using GC-MS. Six plots were randomly selected and samples were taken a day before, a day, three days and five days after the application of malathion. The samples were divided into treated (soaked in tap water and salted water), and untreated groups. The sample was extracted through the liquid-liquid extraction and underwent a clean-up process by a silica gel. The residues were found in; three samples treated with salt water (A1= 19.78 μg/kg, C1 = 8.53 μg/kg and E1= 0.99 μg/kg), one sample treated with tap water (E1=0.44 μg/kg) and two unwashed samples (E1=0.0053 mg/kg and F1=0.0077 mg/kg). Therefore the safest way to consume is by soaked with tap water compared with soaked in salt water and unwashed. However the malathion residue found were below the Maximum Residue Limits set up by US EPA.

Uranium(II) biosorption from aqueous solution by Cystoseira indica biomass was studied in a packed bed column. The uptake capacity of uranium was investigated by natural and different pretreated biomasses. Results showed 0.1 M CaCl2 solution at pHs 4, used as pretreatment, increased the uptake capacity more than 30% (371.39 mg/g). Cations concentration measurement in the effluent solution, Fourier Transform Infrared spectroscopy and X-ray Fluorescence analyses on biosorbents proved that ion exchange is the main biosorption mechanism. The elution efficiency for uranium desorption was determined for various chemical agents in a batch system. Among these eluants, 0.1 M HCl exhibited elution efficiency greater than 78%. Also, biomass regeneration by 0.1 M HCl was studied in a continuous system. The obtained results confirmed that reusability of this biomass is conceivable. Thus, Cystoseira indica can be used in the packed bed column as a potential biosorbent for treatment of uranium polluted aqueous solutions.

Chemical fingerprinting is an aspect of environmental forensic investigation which involves chemical analysis of contaminants and associated chemicals to provide source specific information. Polynuclear Aromatic Hydrocarbons (PAHs) in the environment have 3 categories of sources namely petrogenic, pyrogenic and biogenic sources. Petrogenic PAHs are generated from geochemical alterations of organic mater. Pyrogenic PAHs originate when organic matter is incompletely combusted. Biogenic PAHs originate as a result of oxidation of microbial or plant derived compounds in older and deeper sediments. PAHs fingerprinting involves the determination of a number of quantitative diagnostic ratios of source specific marker PAH compounds. These quantitative diagnostic ratios may be used to distinguish petrogenic PAHs including phenanthrene/anthracene; benz(a)anthracene/chrysene; flouranthene/pyrene; phenanthrene/(phenanthrene+anthracene) and indeno(1,2,3-cd) pyrene/indeno (1,2,3-cd) pyrene + benzo (ghi) perylene from other sources. In this research over 40 environmental samples from the Niger Delta region were subjected to chemical fingerprinting employing some of the quantitative diagnostic ratios above with the aim of ascertaining the precise nature and source the contaminants. It was found that the PAHs contamination in the Niger Delta is not only emanating from petrogenic sources but other sources contribute significantly.

The purpose of this laboratory scale experimental research was to investigate the application of integrated microwave irradiation and granular activated carbon adsorption for removing volatile organic compounds (VOCs) from emissions released from industrial processes and considered major pollutants of the environment. A stream containing 300 ppm toluene was supplied and passed through the granular activated carbon (GAC). The saturated adsorbent was placed in a quartz glass reactor and treated by microwave (MW) irradiation at heating frequency of 2450 MHz at different power levels. Adsorption capacity was evaluated through breakthrough curves and the residue analyzed by gas chromatography. Breakthrough results showed that the high relative humidity of the inlet gaseous stream could lead to decreased GAC adsorption capacity. We found that GAC could absorb microwave irradiation and dissipate heating energy increasing its temperature up to 600°C in a short time mainly depending on the microwave power level. Our experimental results indicated that most of the toluene vapor passed over GAC was decomposed under 900 watt microwave irradiation after around 10 minutes. The addition of water vapor in the inlet stream slightly decreased pollutant removal rate over the GAC while the overall oxidation removal remain the same compared to stream with low content of water vapor. Adsorption isotherms showed that GAC surface area and porosity values increased slightly under microwave irradiation. We concluded that simultaneous application of GAC and microwave irradiation may be an effective approach for removing VOCs from gaseous stream.

Bisphenol A and bisphenol F are chemical substances widely used in industry as monomers in the production of epoxy resins and polycarbonates, and as antioxidants in PVC. Epoxy resins are used as inner surface coating of food and beverage cans. The contamination of can's content by bisphenol A and bisphenol F may pose a serious threat to human because of their estrogenic activity. In this study, the concentration of bisphenol A and bisphenol F in 48 cans of different kinds of foods (corn, tomato paste, stew and tuna fish) were determined by gas chromatography-mass spectrometry after solvent extraction with acetonitrile and preconcentration by headspace-solid-phase microextraction (HS-SPME). Quantitative analysis was carried out based on spiked calibration samples and analyses were performed for each sample in triplicate. Bisphenol F was not detected in any of the canned foods with detection limits of 0.10 μg/kg.There were significant differences among the mean concentrations of bisphenol A in all kinds of canned foods. The mean concentrations of bisphenol A increased significantly all samples after heating in (ANOVA p<0.05 and Kruskal-Wallis test p<0.05); also tuna fish samples were found to be probably the most polluted groups in this study.