INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY (IJEST)
Year:2012 | Volume:9 | Issue:4|Papers Count:20

Levels of barium, cadmium, chromium, copper, mercury and vanadium were determined by plasma emission spectroscopy in sediments and oysters (Crassostrea virginica) in the Palizada, Chumpan and Candelaria rivers, which flow into the Te´rminos Lagoon, state of Campeche, Mexico. The relation between the condition index of the oyster and the detected elements were determined as well.Significant relations were observed between copper (r= -0.825, p\0.05) and chromium (r=-0.787, p\0.05), which indicates the oysters’ affectation by ingesting both elements; concurrently, the results confirm that oysters present high tolerance to heavy metals. The average concentration of cadmium (2.05mg/g), chromium (1.82 mg/g) and copper (115.55mg/g) in rainy-season climate exceeded the limits for marine mollusks regarding different health standards. It was found that the rainy season, the sediment characteristics and organic matter content have a great influence on the transport and availability of heavy metals.

the present study attempts to use the methanol–silver nanofluid filled heat pipe heat exchanger and compares the effectiveness as well as the energy saving with pure methanol. A heat pipe heat exchanger has been tested in a test rig under steady-state conditions. The lengths of both the evaporator and the condenser sections of the heat exchanger were 700 mm, and its central adiabatic section had a length of 160 mm. The heat exchanger had 36 plate finned copper thermosyphons arranged in three rows. The inlet air temperature across the evaporator section was varied in the range of 33-43oC while the inlet air temperature to the condenser section was nearly constant to be 13oC. First, pure methanol was used as the working fluid with a fill ratio of 50 % of the evaporator section length, and then dilute dispersion of silver nanoparticles in methanol was employed as the working fluid. The nanofluid used in the present study is 20 nm diameter silver nanoparticles. The experiments were performed to compare the heat pipe heat exchanger effectiveness and energy saving, using nanofluid and pure methanol. The inlet air relative humidity across the evaporator section was varied between 35 and 80 %. The sensible effectiveness of the heat pipe heat exchanger obtained from experiments varied about 5-22 % for pure methanol and 9-32 % for methanol-silver nanofluid. Based on these experimental results, using methanol-silver nanofluid leads to energy saving around 8.8-31.5 % for cooling and 18-100 % for reheating the supply air stream in an air conditioning system.

Non-point source (NPS) pollution has been increasingly recognized as a major contributor to the declining quality of aquatic environment in recent years. Because of the data shortage, the non-point source loads estimation in the large-scale watershed is always difficult in most developing countries. In this study, small-scale watershed extended method (SWEM) was introduced with a case study in the middle part of Three Gorges Reservoir Region (TGRR). Small-scale watershed extended method is the method which uses physical-based models in some small typical catchments of the targeted large watershed, and then the parameters obtained from those small catchments are extended to the surrounding area until the non-point source pollution loads in the entire watershed or region are obtained. The selected small catchments should have sufficient data. Here, the middle part of the Three Gorges Reservoir Region, about 12, 500 km2, was chosen as the targeted region for the case study. In this region, considering the data availability, Xiaojiang River was screened as a typical watershed and was simulated with Soil and Water Assessment Tool model through accurate parameter calibration and validation. And then the parameter group obtained in Xiaojiang River Watershed was extended to the entire study area to quantify the total non-point source pollution loads. After which, the spatio-temporal characteristics of the non-point source pollution in the middle part of the Three Gorges Reservoir Region were analyzed, as well as the pollution from each tributary and different under layer surface conditions. The small-scale watershed extended method provides a practical approach for non-point source pollution loads estimation in the large-scale watershed or region.

This study aims to evaluate the effect of chlorpyrifos on several metabolic and stress related parameters of Vigna radiata L. Twenty-days-old plants were exposed to several concentrations of chlorpyrifos, ranging from 0 - 1.5 mM through foliar spray in the field condition. Analyses were done at pre flowering (Day 5), flowering (Day 10) and post flowering (Day 20) stages after the treatment. Lipid peroxidation rate, proline, dehydroascorbate, oxidized and total glutathione were all ascended. Chlorpyrifos enhanced lipid peroxidation rate and proline content with 1.5 mM at day 20 whereas dehydroascorbate, oxidized and total glutathione were increased in 1.5 mM at day 10. However, dose dependence significantly declined in content of ascorbate and reduced glutathione levels were observed at all growth stages. Among the enzymatic antioxidants, activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase enhanced significantly in all the concentrations at day 10. Maximum catalase activity was observed at day 10 in control and it declined thereafter. The above results clearly depicted the provoked state of oxidative stress under chlorpyrifos exposure in Vigna radiata L. and therefore can be used to evaluate the degree of insecticide contamination to plant which may be serving as biomarker in Vigna radiata L.

Open-pit mining method has severe environmental impacts which should be prevented, monitored, controlled, and reduced by mined-land reclamation process. After mine closure, a permanent post-mining land use should be implemented as an appropriate choice for using different sections of mined land. The most appropriate alternative of post-mining land use for each section of mined land is presented as the optimum post-mining land use. Pit area among different sections of mined land has more significant effects on the environment and also on defining the optimum post-mining land use for other sections of mined land. Though there are several alternatives and criteria for defining the optimum post-mining land use, the multi-attribute decision-making methods can be efficient techniques in this regard. The nature of the effective parameters used for defining the optimum post-mining land use is the same as Fuzzy numbers including incremental changes without definite limits. Thus, application of the Fuzzy multi-attribute decision-making modeling can produce more reliable results than that of other techniques. As well, pair-wise comparisons and judgments through Fuzzy numbers have proper consistency with the nature of the effective parameters; therefore, a model is developed to attain the optimum post-mining land use for pit area through Fuzzy analytical hierarchy processing. As a case study, the model was implemented in Sungun copper mine in the Northwest of Iran. Forestry–lumber production was defined as the optimum post-mining land use containing the greatest relative importance coefficient 3.019 for the pit area in this mine.

In this paper, the sorption of uranium onto nanoporous silica adsorbent in the presence of nitrate, sulfate, chloride, fluoride and phosphate was studied. The effect of contact time between the nanoporous sorbent and aqueous solution, pH and initial concentration of uranium was also investigated. Uranium sorption onto nanoporous silica adsorbent is a very fast process as sorption rate increases with pH increment. Optimum pH for uranium sorption was 4–8. Experimental sorption isotherm is successfully described by Langmuir and Freundlich models. The results obtained by batch experiments showed that the presence of high concentration of nitrate, sulfate, chloride and phosphate anions alone had no interference with uranium recovery. However, the presence of fluoride ions (>250 mg/L) decreases uranium sorption by about 55 %. The results also showed that the presence of phosphate ions (about 300 mg/L) in solution could remove fluoride interference completely. Finally, the efficiency of the nanoporous silica adsorbent for uranium recovery from wastewater of the uranium conversion facility was investigated.

In this study, the treatability of marble processing wastewater by electrocoagulation using aluminum and iron electrodes was investigated. The sample used was from the marble-processing plant in Sivas and its turbidity, suspended solids, chemical oxygen demand and total solids concentrations were about 1,914 NTU, 2,904, 150 and 4,750 mg/L, respectively. The effects of various operating parameters such as initial pH, current density and electrolysis time on turbidity, suspended solids, chemical oxygen demand and total solids removal efficiencies were investigated. The settling characteristics of waste sludge produced and energy and electrode consumption were also determined. The optimum values of initial pH, current density and electrolysis time in electrocoagulation studies carried out using aluminum electrode were found to be 7.8, 30 A/m2 and 5 min, respectively. Under these conditions, the removal efficiencies obtained for turbidity, suspended solids, chemical oxygen demand and total solids were 98.5, 99.2, 55.2 and 92.4 %, respectively. Corresponding energy and electrode consumptions were 0.143 kWh/kg SS and 0.010 kg Al/kg SS. For iron electrode, the optimum parameter values were found to be 7.8 pH, 20 A/m2 and 5 min, respectively. Under these conditions, removal efficiencies for turbidity, suspended solids, chemical oxygen demand and total solids were determined as 94.3, 99.1, 54.2, and 96.1 %, respectively. Energy and electrode consumptions were 0.0571 kWh/kg SS and 0.0206 kg Fe/kg SS, respectively. Settling characteristics of sludge produced during experiments carried out using both aluminum and iron electrodes were fairly good. The results showed that electrocoagulation method can be used efficiently for the treatment of marble processing wastewater under proper operating conditions.

Water samples were collected for 23 different stations along a cross section profile of an estuary extending over to adjacent sea. The collected water samples were filtered and analyzed for major–minor ions and strontium isotope using the standard procedure to understand the geochemical behaviors of major and minor elements. The normalized values indicated that all riverine elements were entering to adjacent coastal sea with some significant variations at the estuary. The seawater dilution and regression lines explain about the overall patterns for seven elements. Removal processes were detected on calcium, magnesium, strontium and sulfate in the estuarine region. No significant mineral precipitation observed to release magnesium with respect to calcium. Minor variations of strontium and sulfate ions could be attributed to the presence of organic matter in the study area. Comparing seven elements with total suspended matters revealed that the total suspended matters played crucial role in either adsorption or absorption of all the elements in estuary before it reaches to coastal sea. Mixing patterns of strontium isotope showed minimal non-conservative with an evidence of active geochemical process in the estuary.

he optimum period for ciliated protozoa colonizing of an artificial substrate, the polyurethane foams have been assessed in a tropical aquatic ecosystem, the Ekozoa stream of the Mfoundi River Basin in Yaounde (Cameroon). 5 days were calculated as the highest period for the biological indicators of pollution to optimally colonize the artificial substrate. This time interval is the same for all the sampling stations assessed from upstream to downstream and the various microhabitats along the water course. The statistical method applied is that of the completely randomized blocks. The colonization of the substrate increases from the first day to the fifth day, before decreasing to the tenth day. The statistical analysis of variance between the maximum day and the other sampling period was significant at 5 % while the calculation of the value between different points of the same station was not significant. The average number of ciliated protozoan ranges from 20 to 23, from upstream to downstream.

This study aimed to investigate the removal of 24 semivolatile organic compounds in Yangtze River (China) source water treated by six biofilters using different backwashing methods. Health risks induced by the pollutants in the influent and effluent water were also assessed based on the chemical detections. Comparatively, the biofilter backwashed with both air (15 m/h, 3 min) and water (8 m/h, 5 min) was most efficient in removing semivolatile organic compounds and reducing health risk. PCR-denatured gradient gel electrophoresis showed that backwashing alterations posed considerable influences on microbial community structure in the six biofilters. About 72.4 % of di-n-butyl phthalate and 81.8 % of bis (2-ethylhexyl) phthalate (two main semivolatile organic compounds in the river water) were removed under the optimal backwashing conditions. However, in the effluent of each biofilter, non-carcinogenetic risks of 2, 6-dinitrotoluene and bis [2-ethylhexyl] phthalate and carcinogenetic risks of dibenz [a,h] anthracene and benzo [a] pyrene did not reach safety levels, revealing that these pollutants in the source water deserve more public health concerns. This study might serve as a basis for biofiltration process optimization and also as a benchmark for the authorities to reduce the health risk induced by exposure to the hazardous pollutants.

The effects of different heavy metals (copper and mercury), cationic surfactants cetylpyridinium chloride, anionic surfactant sodium dodecyl benzene sulfonate and the chemistry of the solution (pH value) on the adsorption of three selected phenolic compounds (2, 4-Dichlorophenol, 2, 4-Dinitro-phenol and 2, 4-Dimethyphenol) on sediment were studied. Results indicated that in the sediment-water system with phenolic compounds: (1) all of the data could be simulated by Freundlich equation; (2) the experiments studying pH effects showed that the adsorption capacity of 2, 4-Dichlorophenol and 2, 4-Dimethyphenol were quite potentia Hydrogenii dependent and increased with decrease in potentia Hydrogenii, while 2, 4-Dinitrophenol followed the different trend; (3) As the concentration increased from 0 to 0.2 mM for Cu2+, the Freundlich capacity coefficient constant varied from 62.84 to 325.1 for 2, 4-Dichlorophenol, from 13.1 to 82.179 for 2, 4-Dinitrophenol and from 29.433 to 7.976 for 2, 4-Dimethyphenol, respectively. The Freundlich capacity coefficient constant of 2, 4-Dichlorophenol, 2, 4-Dinitrophenol and 2, 4-Dimethyphenol varied from 62.84 and 421.43, 13.1 and 138.1, 29.433 and 1.381, respectively, with concentration of Hg2+ increased from 0 to 0.04 mM, respectively; (4) the adsorption of 2, 4-Dichlorophenol and 2, 4-Dimethyphenol were accentuated by cetylpyridinium chloride but suppressed by sodium dodecyl benzene sulfonate, whereas the adsorption of 2, 4-Dinitrophenol on sediment was enhanced by both cationic and anionic surfactants, effects that are consistent with electrostatic and hydrophobic interactions among ionic surfactants, phenolic compounds and sediment. The results are believed to provide a useful insight into describing the transport and fate of phenolic compounds in natural environments.

This paper presents the removal study of hazardous hexavalent chromium from liquid waste streams using divinylbenzene copolymer resin Amberlite IRA 96. Important sorption parameters such as contact time, pH, resin dosage and initial metal concentration were studied at 30°C. The kinetic study was conducted using pseudo first and pseudo second order kinetics at 30°C. The sorption process was found to be pH dependent. Maximum removal was obtained at pH 2 under optimized conditions. The sorption process was rapid and 99% of the removal was achieved in first 30 min. The equilibrium data were fitted to both Langmuir and Freundlich models. The better regression coefficient (R2) in Freundlich model suggests the multilayer sorption process. The value of Gibbs free energy for sorption process was found to be (-12.394 kJmol-1). The negative value indicated the spontaneity of the sorption process. SEM and EDX studies were conducted to find the role of surface morphology during sorption process. The FTIR study was conducted to identify the functional groups responsible for interaction between the resin and chromium. Desorption and Regeneration studies also carried out.

Several media have been used in treatment plants, however, their efficiency for turbidity removal, which is determined by qualitative indices, has been considered. Current qualitative indices such as turbidity and escaping particle number could not completely measure the efficiency of the filtration system; therefore defining new qualitative indices is essential. In this study, the efficiency of two different dual media filters in turbidity removal was compared in different operating condition using qualitative indices. The pilot consisted of a filter column (1-m depth) in which the filter-1 was consisted of a layer of anthracite (450-mm depth) and a layer of silica sand (350-mm depth); and filter-2 had the same media characteristics except for the first layer that was light expanded clay aggregates (LECA). Turbidities of 10, 20, and 30 NTU, coagulant concentrations of 4, 8, and 12 ppm and filtration rates of 10, 15, and 20 m/h were considered as variables. Results showed that the media of filter-2 is a suitable substitute for the media of filter-1 (P value < 0.05). Turbidity removal efficiencies in different condition were 79.97 ± 1.79 to 91.37 ± 1.23% for the filter-2 and 75.12 ± 2.75 to 86.82 ± 1.3% for the filter-1. The LECA layer efficiency in turbidity removal was independent of filtration rates and due to its low head loss; LECA can be used as a proper medium. Results also showed that the particle index was a suitable index as a substitute for turbidity and escaping particle number as indices.

Nitrogenous disinfection by-products have increasingly become a public health concern in the drinking water industry because they have been found to be more geno- and cytotoxic than most of the currently regulated disinfection by-products. Dichloroacetamide, a nitrogenous disinfection by-product which is formed during chlorination in water treatment, has increasingly received attention due to its elevated genotoxicity and cytotoxicity relative to the currently regulated disinfection by-products. In this study, a power function model with parameters of dissolved organic nitrogen, dissolved organic carbon, bromide, soluble microbial products, and aromatic proteins was developed to successfully predict dichloroacetamide formation potential. The inclusion of soluble microbial product and aromatic protein into the model significantly improved the prediction, suggesting that soluble microbial product and aromatic protein play a significant role in the formation of dichloroacetamide. Additionally, the performance of the predictive model appeared to be somewhat affected by the characteristics of raw water used to develop the model.

The existence of polycyclic aromatic hydrocarbons in the various environments has aroused great environmental concerns due to their potential hazards to human health. The presence of polycyclic aromatic hydrocarbons in aquifer is particularly sensitive where groundwater is used as a source of potable water. Anaerobic biodegradation of polycyclic aromatic hydrocarbons is an attractive option for remediation of contaminated aquifer sediment. Bacterial and archaeal community structures of phenanthrene-degrading aquifer sediment under methanogenic condition were investigated using clone library analysis in combination with microcosm study. The bacterial members were all affiliated with g-Proteobacteria. Phylum Euryarchaeota was the predominant archaeal group, represented by genera Methanosarcina, Methanobacterium and Thermogymnomonas. Both bacteria (genera Citrobacter and Pseudomonas) and archaea (genus Methanosarcina) might have links to phenanthrene degradation process. This work might provide some new insights into developing strategies for the isolation of the putative polycyclic aromatic hydrocarbons degraders under methanogenic condition and bioremediating polycyclic aromatic hydrocarbons in leachate-contaminated aquifer sediment.

In this study, a naturally available crab shell chitosan of low molecular weight (20 kDa) has been used as adsorbent to evaluate the pollution load in vegetable oil mill effluent. A series of batch experiment was conducted by varying chitosan dosage (100-400 mg), pH (2-9), stirring time (15-90) min and agitation speed (25-150 rpm) to study their effects on adsorption and flocculation processes. The parameters considered for adsorption study are chemical oxygen demand, total suspended solids, electrical conductivity and turbidity. The maximum reduction in chemical oxygen demand, total suspended solids, electrical conductivity and turbidity is 74, 70, 56 and 92 %, respectively. The observed experimental result showed that crab shell chitosan could able to reduce significantly the chemical oxygen demand, turbidity, electrical conductivity and suspended matter. The optimum conditions were estimated as 400 mg/l chitosan, pH 4 and 45 min of mixing time with mixing speed of 50 rpm. Chitosan showed very good pollution removal efficiency and can be used for the effective treatment of vegetable oil mill effluent.

Research on recycling waste printed circuit boards is at the forefront of preventing environmental pollution and finding ways to recycle resources. A wet process for reclaiming metals from printed circuit boards applying a tapered diameter separation bed is described, and the separation mechanism of the device is proposed. The motion of a particle in the tapered diameter fluid flow field and particle separation within this field were studied. As the material passes through the fluid field, along with the water, differences in particle density, granularity, and shape cause particles to follow at different trajectories. A tapered diameter separation bed was used to process 1-0.074 mm-sized crushed material from discarded printed circuit boards. The separation efficiency of 91.77 % and the recovery rate of 95.79 % for recovered metal were achieved with a discharge water flow rate of 4.5m3/h, a material feed rate of 300 g/min, and an obliquity of 30o. For -0.074 mm printed circuit boards, the metal recovery is 93.42 % and the separation efficiency is 77.63 % when the water discharge is 2 m3/h, the obliquity is 35o, and the material feed rate is 450 g/min. The superfine products in a size range of -0.074 mm can be recovered effectively under suitable operating condition using the tapered diameter separation bed. It indicates that the lower separation limit of the tapered diameter separation bed can be close to zero. The technique will prevent environmental pollution from waste printed circuit boards and allow efficient recovery.

This study presents energy efficiency measures in fans as an important energy consumption facility in the industry and common usages by identifying the sources of energy loss and applying methods to reduce those losses, which are one of the critical issues in protecting the environment and in global warming. The carbon footprint can be lowered by reducing the energy consumption of a fan over its life cycle. The main sources of energy loss in fans such as noise, vibration, lubrication, temperature of the bearings, installation type, damper and filter, especially pulley and belt system compared to electrical variable speed drive, are theoretically and experimentally discussed. The laboratory results show that the mechanical variable speed drive is one of the critical sources of energy loss in centrifugal fans. The results also show that by changing the drive with an electrical variable speed drive, the energy usage can be substantially optimized. For instance, using an electrical variable speed drive has reduced the energy loss up to 38.5 % with regard to the speed and according to the different flow rates. Moreover, based on the results derived from the equations and figures, it can be concluded that a considerable amount of energy per year, as well as the related cost can be saved and this shall be noted particularly in industrial applications.

Due to differences in rainfall regimes and management practices, tropical urban catchments are expected to behave differently from temperate catchments in terms of pollutant sources and their transport mechanism. Storm Water Management Model (SWMM) was applied to simulate runoff quantity (peakflow and runoff depth) and quality (total suspended solids and total phosphorous) in residential, commercial and industrial catchments. For each catchment, the model was calibrated using 8-10 storm events and validated using seven new events. The model performance was evaluated based on the relative error, normalized objective function, Nash–Sutcliffe coefficient and 1:1 plots between the simulated and observed values. The calibration and validation results showed good agreement between simulated and measured data. Application of Storm Water Management Model for predicting runoff quantity has been improved by taking into account catchment’s antecedent moisture condition. The impervious depression storages obtained for dry and wet conditions were 0.8 and 0.2 mm, respectively. The locally derived build-up and wash-off parameters were used for modelling runoff quality.

Three microbial consortia were isolated from three polluted soils located at an oil refinery and acclimated to grow on diesel fuel as the sole carbon source. Batch experiments were then conducted with the three consortia to study the kinetics of diesel biodegradation. The effects of temperature (25, 30 and 35oC) and diesel concentration (0.5, 1 and 3 %) on the biodegradation of diesel were analysed. Several species were identified in the acclimated microbial consortia, and some of them appeared in more than one consortium. Thermal inhibition was observed at 35oC. In the rest of experiments, over 80 % of the substrate was degraded after 40 h of treatment. These results proved the good feasibility of using the polluted sites as sources of mixed consortia for hydrocarbon degradation. However, diesel degradation efficiencies and rates were very similar, suggesting that the acclimation process produced mixed consortia with very similar characteristics; in this context, origin of the soil sample was not a decisive factor. A simple Monod-type kinetic model was used to simulate the biodegradation process, and accurate results were obtained. The m max values were between 0.17 and 0.34 h-1. The results of this study revealed that the consortia can function at high concentrations of hydrocarbons without any sign of growth inhibition, which is important for the design of bioreactors for wastewater treatment with high concentrations of fuel.