International Journal of Environmental Science and Technology

Numerical simulations of ice accumulation under ice cover along a river bend

1J. Wang; 2*J. Sui; 1P. Chen

In this paper, the k -Ý two-equation turbulence model has been used to simulate ice accumulation under ice cover along a river bend. A 2D depth-averaged numerical model has been developed in a nonorthogonal coordinate system with nonstaggered curvilinear grids. In this model, the contravariant velocity has been treated as an independent variable. To avoid the pressure oscillation in the nonstaggered grids, the momentum interpolation has been introduced to interpolate variables at the interface. The discretization equations have been solved by using pressure correction algorithms. An equation has been developed for describing the deformation of ice jam bottom. The thickness distribution of ice accumulation (ice jam) along the bend has been simulated. The developed model has been applied to the experimental studies under different conditions carried out at the Hefei University of Technology. Results indicate that all simulated thickness of ice accumulation agrees reasonably well with the measured thickness of ice accumulation in laboratory.

Characterization of chikusaku-eki and mokusaku-eki and its inhibitory effect on sapstaining fungal growth in laboratory scale

1N. Velmurugan; 1S. S. Chun; 1S. S. Han; 1 ,2*Y. S. Lee

Chikusaku-eki and Mokusaku-eki are natural resources and acidic liquid by-products of bamboo and broad leaved trees charcoal burner. These products contain more than 200 ingredients, including phenols, poly phenols and acetic acids. These by-products were tested for their fungicidal activity against sapstaining fungi. There are no studies about the antifungal activity of Chikusaku-eki and Mokusaku-eki against wood staining fungi in the literature. According to the recent findings, this is the first report about the antifungal activity of Chikusaku-eki and Mokusaku-eki against wood staining fungi. These extracts were more effective against sapstaining fungi at minimum concentrations (0.10-1.0 %) used in 2 % (malt extract agar) medium. Three Chikusaku-eki (Chikusaku-eki-I, Chikusaku-eki-II and Chikusaku-eki-III) and 2 Mokusaku-eki (Mokusaku-eki-I, Mokusaku-eki-II) extracts were tested against 4 sapstaining fungal samples to evaluate the inhibition range on sapstaining fungal growth. Ophiostoma flexuosum, Ophiostoma tetropii, Ophiostoma polonicum and Ophiostoma ips were the sapstaining fungi used in this study against bamboo and wood extracts. The initial calibration of extracts was done by calculating the specific gravity, tar calculation and total organic content. The chloroform fractions of these extracts were analyzed by gas chromatography-mass spectrometry and both the extracts contained 2,6 dimethoxy phenol, dehydroacetic acid and 2,3,5 trimethoxytoluene. Results revealed that compounds of Chikusaku-eki and Mokusaku-eki markedly inhibited fungal growth at lower concentration. The Chikusaku-eki and Mokusaku-eki have both antifungal, antioxidant properties and a potential to be used as natural preservative in wood industries. Wood slice tests displayed the effective role of both extracts in laboratory level.

Innovative approach to design a new national low speed wind tunnel

1*M. Abbaspour; 2M. N. Shojaee

A new multipurpose wind tunnel with adjustable test section designed in the science and research branch of Islamic Azad University site could be used either as the environmental, subsonic or climatic wind tunnels. For this purpose, a new design approach was adopted in which through the adjustment of the wind tunnel cycle, i.e. the nozzle of test section,it could be utilized as any of the three wind tunnels. A design used for environmental wind tunnels and other contraction which was adjusted by 50 % through changes in the polynomial contraction for other applications. As a result, the best fitted profile for the environmental wind tunnels contraction was selected by contraction best fit program. Consequently, the flow properties and flow separation of contractions were analyzed by the computational fluid dynamics model in a computer software. This method is also suitable for existing low speed wind tunnels with special applications.

Effective environmental management through environmental knowledge management

*1Po-Shin Huang; 2Li-Hsing Shih

Owing to the green revolution, environmental problems have now become some of the most important issues worldwide. Environmental knowledge management, which combines the strengths of environmental management and knowledge management, will become a popular tool for businesses in the near future. In this paper, through interviews of staff at different levels and in different departments of the business, i. e. managers and engineers and using the environmental knowledge circulation process, the authors evaluate the success of environmental knowledge management when applied to China Steel Corporation in Taiwan. From the case study, the authors found that China Steel Corporation has applied the environmental knowledge circulation process for over thirty years. The company continually improves its environmental and financial performance through environmental knowledge creation, environmental knowledge accumulation, environmental knowledge sharing, environmental knowledge utilization and environmental knowledge internalization. Water pollution and air emissions have reduced year on year and total energy consumption has reduced by 20 % from 1979 to 2006. On the other hand, China Steel Corporation also makes a profit and reduces cost through energy sold, by-products and recycling. Continuous improvement in environmental knowledge management has rendered China Steel Corporation in the most profitable steel company in Taiwan and the world's twenty fifth largest steel producing company in 2006.

Chemical oxygen demand fractions of municipal wastewater for modeling of wastewater treatment

*I. Pasztor; P. Thury; J. Pulai

When a new wastewater treatment plant is being designed by computer simulation, detailed data about organic fractions of influent wastewater (measured as chemical oxygen demand) are usually not available, but knowledge of the typical ranges of these fractions is indispensable. The influent chemical oxygen demand fractions can substantially influence the results of simulation-based design such as reactor volumes, solids residence time, effluent quality, oxygen demand, sludge production, etc. This article attempts to give an overview of wastewater organic fractions as modeling parameters and presents new chemical oxygen demand fractionation results from Hungary. According to the data from literature, the ratio of chemical oxygen demand components in raw wastewater is very different and the average composition is as follows: Inert particulate = 17.1 %, slowly biodegradable = 57.9 %, inert soluble = 7.8 % and readily biodegradable = 17.5 %. The Hungarian wastewater samples were analyzed according to STOWA (Dutch foundation for applied water research) protocol and the obtained results were not much different from those of literature ( inert particulate = 23.7 %, slowly biodegradable = 49.8 %, inert soluble = 4.6 % and readily biodegradable = 21.9 %), but some typical characteristics were observed.

Analysis of shake flask experiments results conducted on residues from hydrometallurgical processes

*A. Steel; K. Hawbol; F. Khan

Hydrometallurgical facilities processing sulfide based ores produce waste residues in the form of sludges that contain concentrations of metals, as well as metal sulfides. As a part of the waste characterization and risk assessment process, a statistical design of experiment was used to assess the significant factors and interactions in the residue leaching process. Two shake flask experiments, a 24 factorial design and 23 central composite design were employed to evaluate the effect of mixing time, test pH, solid/liquid ratio and residue type on acidity, alkalinity, sulfate and metal concentration and pH of the resulting filtered leachate. The results indicate that the variable tested mixing time and solid/liquid ratio most strongly affect metal concentration in the filtrate from waste residue samples tested over a moderate test pH range. When tests were conducted over a longer test period and at lower test pH values, test pH and residue type were dominant factors contributing to residue filtrate metal concentration.

Environmental biological model based on optimization of activated sludge process

1*X. X. Zhang; 1D. Y. Zhao; 1Z. X. Wang; 1B. Wu; 1, 2W. X. Li; 1S. P. Cheng

A simplified environmental biological model has been developed based on biodegradation kinetics correlation to regulate and optimize wastewater treatment system of activated sludge process. All parameters included in the model are calibrated in accordance with reference data and experimental results and good agreements are achieved between calculated results and reference data or experimental results. The minimum bioreactor volume is used as objective function in the model and errors between optimal minimum volume of the model and each reported result of three references are found to be no more than 8.63 % after validation. Comparisons between optimal results and experimental data demonstrate that the deviations are negligible. The optimal minimum volume is 9.21 m3 with the error of 6.40 % to the practical bioreactor volume of a pilot treatment system. The environmental biological model has been applied to economically evaluate a former treatment system with native bacterium YZ1 and four operation periods of the pilot system with functional strain Fhhh compared with YZ1, Fhhh possesses higher biodegradation ability in purified terephthalic acid wastewater and a broader economic potential in the field of wastewater treatment.

Sorption isotherms and kinetics of chromium uptake from wastewater using natural sorbent material

1*B. A. Shah; 2A. V. Shah; 1R. R. Singh

Chromium (VI) which exists in many industrial wastewater is considered highly toxic. The aim of the present investigation was to study the reduction of chromium (VI) to chromium (III) and then removing it with the help of weathered basalt andesite products. Reduction of the chromium (VI) to chromium (III) by hydrazinium sulfate was investigated. The influence of hydronium ion concentration, contact time, hydrazinium sulphate dosage and temperature has been tested in batch runs. The process was found to be acid, temperature and concentration dependent. The suitability of weathered basalt andesite products as a potential sorbent was assessed for the removal of chromium (III) following batch mode of operation. The effect of various parameters such as hydronium ion concentration, shaking time, sorbent dose, initial metal ion concentration and temperature on the removal of chromium (III) from aqueous solution was studied. Thermodynamic parameters (DH' DS' and DG') for the sorption process were evaluated. Analysis of sorption obtained results showed that the sorption pattern followed the Freundlich, Langmuir and Dubinin-Kaganer-Radushkevich isotherms. The process follows pseudo second order rate and surface diffusion is identified as the predominating mechanism. The sorption process was shown to be reversible by the recovery of sorbed chromium (III) upon extraction with 0.5 M nitric acid. The sorbent, before and after sorption, was characterized by fourier transform infrared spectrometer, X-ray diffraction, scanning electron microscope, transmision electron microscope and thermo-gravimetric analyse methodes. An increase in crystallanity after sorption of chromium was observed. An industrial effluent was successfully treated with the same sorbent with convincing results.

Distribution of volatile organic compounds around a polluted river

1*D. F. Juang; 2C. S. Yuan; 1S. C. Hsueh; 1L. J. Chiou

The objectives of this study were to investigate the species and the concentration distribution of volatile organic compounds around a heavily polluted river. Air samples were collected seasonally at different locations near the polluted river. Samples were then analyzed by gas chromatography (electron capture detector for chlorinated organic compounds and flame ionization detector for ordinary hydrocarbons). The data was then analyzed by the statistical product and service solutions software. The results showed that total of 26 species of volatile organic compounds were identified. Each individual had its own concentration distribution pattern at different seasons and aliphatic volatile organic compounds displayed much higher concentrations than most benzenoic volatile organic compounds. In aliphatic volatile organic compounds, 1,2-dibromo-3-chloropropane, hexachlorobutadiene and 1,2-dibromoetane had much higher concentrations at the nearby environment of the river and they have been claimed to be carcinogenic to some experimental animals and possibly to human. Therefore, It is in doubt that for a long term, the volatile organic compounds evaporating out of the stream may threat the health of the residents living very close to the river. The concentrations of tetrachloroethene, 1,1,2,2-tetrachloroethane, hexachlorobutadiene, dibromoetane, dichlorobenzene and sec-butylbenzene appeared at the nearby environment of the river had significant correlations (P < 0.05) with those of each other or many other volatile organic compounds.

Production of perovskite catalysts on ceramic monoliths with nanoparticles for dual fuel system automobiles

1*A. Khanfekr; 1K. Arzani; 2A. Nemati; 3M. Hosseini

(Lanthanum, Cerium)(Iron, Manganese, Cobalt, Palladium)(Oxygen)3- Perovskite catalyst was prepared by the citrate route and deposited on ceramic monoliths via dip coating procedure. The catalyst was applied on a car with XU7 motors and the amount of emission was monitored with vehicle emission test systems in Sapco company. The results were compared with the imported catalyst with noble metals such as palladium, platinum and rhodium by Iran Khodro company based on the Euro III standards. The catalysts were characterized by specific surface area measurements, scanning electron microscopy, X-ray diffraction, line scan and map. In the results, obtained in the home made sample, the amount of carbon monoxide, nitrogen oxides and hydrocarbons were lower than imported catalyst with Iran Khodro company with nobel metals. The illustration shows nano particles size on coat. The microstructure evaluation showed that the improved properties can be related to the existence of nano particles on coating.

Oxidation ditch process using curved blade rotor as aerator

1*S. B. Thakre; 1L. B. Bhuyar; 2S. J. Deshmukh

Oxidation ditch process is used to treat the municipal and domestic sewage. The untreated sewage generates fouling smell, harmful bacteria, etc. which is hazardous for public health and degrades the environment by librating noxious gases. This paper examines the use of curved blade aerator for oxidation ditch process. The rotor, which controls the aeration, is the main component of the aeration process. Therefore, the objective of this study is to find out the variations in overall oxygen transfer coefficient and aeration efficiency for different configurations of aerators by varying the parameters like speed of aerator, depth of immersion and blade tip angles so as to yield higher values of overall oxygen transfer coefficient and aeration efficiency. Four aerators of different configuration were developed and fabricated in the laboratory and were tested for above mentioned parameters. A mathematical model is developed for predicting the values of kLa and aeration efficiency which has R2 values of 0.97 and 0.99 for experimentally determined and calculated values. In laboratory studies, the optimum value of overall oxygen transfer coefficient and aeration efficiency were observed to be 10.33/h and 2.269 kg O2/kWh for aerator speed of 48 rpm, 5.5 cm depth of immersion and 47o blade tip angle for curved blade aerator.

Availability of barley straw application on oil spill clean up

1M. Husseien; 2A. A. Amer; 3*A. El-Maghraby; 4N. A.Taha

Oil spills are a global concern due to the environmental and economical impact. Various commercial systems have been developed to control these spills, including the use of fibers as sorbents. However, most sorbents end up in landfills or in cineration after single use. These options either produce another source of pollution or increase the oil recovery cost. Plant biomass is renewable resource that can be converted into useful materials and energy. Barley straw, an agricultural waste, was used as sorbent material. The present study examines the absorption capacity of raw barley straw for different petroleum products and water pick up. The investigate revealed that the capacity of fibers to remove crude oil from sea water was related to the surface properties of the fibers, concentration of the oil, size of the fiber, amount of the fibers, as well as the temperature of the crude oil. Cyclic sorption /desorption studies indicated that a simple squeezing operation was enough to remove most of the oil sorbed and that recycling was feasible.

Anaerobic co-digestion of sewage and brewery sludge for biogas production and land application

1*S. Babel; 2J. Sae-Tang; 2 A. Pecharaply

In Thailand, sewage sludge production from the Bangkok metropolitan area can reach up to 63,000 ton/y by 2010. The Beer-Thai Company, Thailand, produces beer and generates lots of sludge as waste. Sewage sludge and brewery sludge can be used to generate energy which could be saved on the fossil fuels conventionally used as a source of energy. The possibility was explored to mix brewery sludge with sewage sludge at different mixing ratios for anaerobic digestion so that the energy can be generated as biogas and at the same time, digested sewage sludge can be used as fertilizer for agricultural applications. A batch anaerobic reactor under mesophilic condition for a digestion period of 40 days was used in the laboratory. The acrylic reactor was cylindrical with a working weight of 12 kg. The diameter was 23.7 cm and the height was 34.5 cm. Sludge mixtures at different ratios were fed into the reactors and the optimum mixing ratio was determined. Experimental results showed that the sludge mixture at ratio of 25:75 % by weight (sewage:brewery) yielded higher biogas production. A reduction in heavy metals and pathogens was observed at this ratio after the digestion indicating its safe use as fertilizer. Nitrogen content was about 4.95 % which is well above the commercial fertilizers. At optimum mixing ratio of 25:75, the amount of the generated biogas is 1.15x106 m3/y. This large amount of biogas is equivalent to 1.44 million kWh/y of electricity, 561,000 L/y of diesel oil and 936,000 L/y of vehicle gasoline.

Gaseous phase benzene decomposition by non-thermal plasma coupled with nano titania catalyst

1T. Zhu; 1*J. Li; 1Y. Q. Jin; 2Y. H . Liang; 2G. D. Ma

Synergistic effect of atmospheric non-thermal plasma generated by dielectric barrier discharge and nano titania photocatalyst for benzene decomposition was tested. The paper indicated the effect of photocatalyst on removal efficiency of benzene, the compare of photocatalyst characteristic in different high temperatures by heat treatment, analysis of by-products. The results showed that the effect of degradation was visible by added photocatalyst in the plasma reactor. When concentration of benzene was 600 mg/m3 and electric field strength was 10 kV/cm, the removal efficiency of benzene was increased up to 81 % without photocatalyst. At the same condition, the removal efficiency was increased to 15 % higher with photocatalyst. Nano titania crystal was anatase crystal in 450 oC heat treatment which is best for benzene removal. The plasma reactor packed with photocatalyst shows a better selectivity of carbon dioxide than that without photocatalyst. By-products are mostly carbon dioxide, water and a small quantity of carbon monoxide.

Kinetic analysis of enhanced biological phosphorus removal in a hybrid integrated fixed film activated sludge process

*B. Hooshyari; A. Azimi; N. Mehrdadi

Hybrid integrated fixed film activated sludge is a promising process for the enhancement of nitrification, denitrification and phosphorus removal in conventional activated sludge systems that can be used for upgrading biological nutrient removal, particularly when they have space limitations or need modifications that will require large monetary expenses. In this research, successful implementation of hybrid integrated fixed film activated sludge process at temperate zone wastewater treatment facilities has been studied by the placement of fixed film media into aerobic, anaerobic and anoxic zones. The primary objective of this study was to investigate the incorporation of enhanced biological phosphorus removal into hybrid integrated fixed film activated sludge systems and study the interactions between the fixed biomass and the mixed liquor suspended solids with respect to substrate competition and nutrient removal efficiencies. A pilot-scale anaerobic-anoxic-oxic configuration system was used. The system was operated at different mean cell residence times and influent chemical oxygen demand/total phosphorus ratios and with split influent flows. The experimental results confirmed that enhanced biological phosphorus removal could be incorporated successfully into hybrid integrated fixed film activated sludge system, but the redistribution of biomass resulting from the integration of fixed film media and the competition of organic substrate between enhanced biological phosphorus removal and denitrification would affect performances. Also, kinetic analysis of the reactor with regarding to phosphorus removal has been studied with different kinetic models and consequently the modified Stover-Kincannon kinetic model has been chosen for modeling studies and experimental data analysis of the hybrid integrated fixed film activated sludge reactor.

Characterization of stabilized waste: Evaluation of pollution risk

1M. Aina, 1G . Matejka, 2D. Mama, 3*B. Yao, 2M. Moudachirou

This study relates to the characterization of stabilized waste. Various parameters such as granulometric distribution, percentage of mineral and organic matter were estimated to appreciate environmental hazard potential and possibility of metal leaching of the samples of waste from Grange site in France. From the results, it was shown that the granulometric distribution was variable. Therefore, a strong proportion of fines (44.6 %) and medium (45.9 %) was observed due to the age of waste that supports the degradation of a great quantity of organic matter. That was confirmed by the strong mineral matter rate (63.8 %) obtained to determine the organic percentage of matter (36.2 %). The amount of heavy metals such as iron, nickel, copper, zinc, cadmium and lead was also studied. The results obtained were in a good agreement with the ones of the literature. Indeed, it appeared that iron, lead, copper, nickel and zinc are in relative strong proportion while cadmium was not very present. Iron represents 78 % of the metals. From the leaching tests, it was shown that the heavy metals concentration were very weak. Moreover, the deposit of studied waste could be a potential source of organic pollution (COD = 150 Mg C/L on average) in the case of precipitation and flood.