ADSORPTION IN MULTICOMPONENT SOLUTION BY ACTIVATED CARBON

It was found that the total adsorptive capacity of activated carbon was enhanced by using a multicomponent solution with glucose, peptone and phenylphosphonic acid. A maximum use of the carbon adsorptive capacity is possible if the carbon is used for tertiary treatment followed by treating a stronger waste.     

Distribution characteristics of polychlorinated biphenyls in crucian carp (Carassius auratus) from major rivers in Korea

Polychlorinated biphenyls (PCBs) levels in crucian carp were determined at 20 locations along four major river systems, several small-scale rivers and a wetland in Korea. Twenty-eight congeners, ranging from tri- to hepta-CBs were detected. A gas chromatograph with a mass selective detector was used to quantify the individual PCB congeners. The objectives of this study were to investigate the levels of contamination of PCBs in freshwater fish and to observe the pattern of their distribution. The sampling locations were chosen among 31 sampling sites that are currently used as environmental residue checkpoints by the Korean Ministry of Environment. Concentrations of individual congeners ranged from not detectable (n.d.) to 0.75 ng g(-1) on a wet weight basis. The total concentrations of PCBs at each site ranged from n.d. to 5.41 ng g(-1) of wet weight. The most heavily contaminated site was the Nakdong estuary located near the Shinpyung-Janglim factory district. The PCB 153 and 138 were the principal congeners and penta- and hexa-chlorinated biphenyls comprised the main congener groups.     

Source identification and trends in concentrations of gaseous and fine particulate principal species in Seoul, South Korea

Ambient measurements were made using two sets of annular denuder system during the four seasons (April 2001 to February 2002) and were then compared with the results during the period of 1996-1997 to estimate the trends and seasonal variations in concentrations of gaseous and fine particulate matter (PM2.5) principal species. Annual averages of gaseous HNO3 and NH3 increased by 11% and 6%, respectively, compared with those of the previous study, whereas HONO and SO2 decreased by 11% and 136%, respectively. The PM2.5 concentration decreased by -17%, 35% for SO4(2-), and 29% for NH4+, whereas NO3- increased by 21%. Organic carbon (OC) and elemental carbon (EC) were 12.8 and 5.98 microg/m(-3), accounting for -26 and 12% of PM2.5 concentration, respectively. The species studied accounted for 84% of PM2.5 concentration, ranging from 76% in winter to 97% in summer. Potential source contribution function (PSCF) analysis was used to identify possible source areas affecting air pollution levels at a receptor site in Seoul. High possible source areas in concentrations of PM2.5, NO3-, SO4(2-), NH4+, and K+ were coastal cities of Liaoning province (possibly emissions from oil-fired boilers on ocean liners and fishing vessels and industrial emissions), inland areas of Heibei/Shandong provinces (the highest density areas of agricultural production and population) in China, and typical port cities (Mokpo, Yeosu, and Busan) of South Korea. In the PSCF map for OC, high possible source areas were also coastal cities of Liaoning province and inland areas of Heibei/Shandong provinces in China. In contrast, high possible source areas of EC were highlighted in the south of the Yellow Sea, indicating possible emissions from oil-fired boilers on large ships between South Korea and Southeast Asia. In summary, the PSCF results may suggest that air pollution levels in Seoul are affected considerably by long-range transport from external areas, such as the coastal zone in China and other cities in South Korea, as well as Seoul itself.     

A simple approach to modeling microbial biomass in the rhizosphere

Microorganisms make an important contribution to the degradation of contaminants in bioremediation as well as in phytoremediation. An accurate estimation of microbial concentrations in the soil would be valuable in predicting contaminant dissipation during various bioremediation processes. A simple modeling approach to quantify the microbial biomass in the rhizosphere was developed in this study. Experiments were conducted using field column lysimeters planted with Eastern gamagrass. The microbial biomass concentrations from the rhizosphere soil, bulk soil, and unplanted soil were monitored for six months using an incubation–fumigation method. The proposed model was applied to the field microbial biomass data and good correlation between simulated and experimental data was achieved. The results indicate that plants increase microbial concentrations in the soil by providing root exudates as growth substrates for microorganisms. Since plant roots are initially small and do not produce large quantities of exudates when first seeded, the addition of exogenous substrates may be needed to increase initial microbial concentrations at the start of phytoremediation projects.     

Biohydrogen production in continuous-flow reactor using mixed microbial culture.

The goal of the proposed project was to develop an anaerobic fermentation process that converts negative-value organic wastes into hydrogen-rich gas in a continuous-flow reactor under different operating conditions, such as hydraulic retention time (HRT), heat treatment, pH, and substrates. A series of batch tests were also conducted in parallel to the continuous study to evaluate the hydrogen conversion efficiency of two different organic substrates, namely sucrose and starch. A heat shock (at 90 degrees C for 15 minutes) was applied to the sludge in an external heating chamber known as a sludge activation chamber, as a method to impose a selection pressure to eliminate non-spore-forming, hydrogen-consuming bacteria and to activate spore germination. The experimental results showed that the heat activation of biomass enhanced hydrogen production by selecting for hydrogen-producing, spore-forming bacteria. The batch feeding at a shorter HRT of 20 hours (or higher organic loading rate) favored hydrogen production, whereas, at a longer HRT of 30 hours, methane was detected in the gas phase. The major organic acids of hydrogen fermentation were acetate, butyrate, and propionate. Up to 23.1% of influent chemical oxygen demand was consumed in biomass synthesis. Batch tests showed that the hydrogen-production potential of starch was lower than sucrose, and better conversion efficiency from starch was obtained at a lower pH of 4.5. However, addition of sucrose to starch improved the overall hydrogen-production potential and hydrogen-production rate. This study showed that sustainable biohydrogen production from carbohydrate-rich substrates is possible through heat activation of settled sludge.     

Pattern recognition of the movement tracks of medaka (Oryzias latipes) in response to sub-lethal treatments of an insecticide by using artificial neural networks

Specimens of medaka (Oryzias latipes) were observed continuously through an automatic image recognition system before and after treatments of an anti-cholinesterase insecticide, diazinon (0.1 mg/l), for 4 days in semi-natural conditions (2 days before treatment and 2 days after treatment). The "smooth" pattern was typically shown as a normal movement behavior, while the "shaking" pattern was frequently observed after treatments of diazinon. These smooth and shaking patterns were selected for training with an artificial neural network. Parameters characterizing the movement tracks, such as speed, degree of backward movements, stop duration, turning rate, meander, and maximum distance movements in the y-axis of 1-min duration, were given as input (six nodes) to a multi-layer perceptron with the back propagation algorithm. Binary information for the smooth and shaking patterns was separately given as the matching output (one node), while eight nodes were assigned to a single hidden layer. As new input data were given to the trained network, it was possible to recognize the smooth and shaking patterns of the new input data. Average recognition rates of the smooth pattern decreased significantly while those for the shaking pattern increased to a higher degree after treatments of diazinon. The trained network was able to reveal the difference in the shaking pattern in different light phases before treatments of diazinon. This study demonstrated that artificial neural networks could be useful for detecting the presence of toxic chemicals in the environment by serving as in-situ behavioral monitoring tools.     

Decolorizing of lignin wastewater using the photochemical UV/TiO2 process

Studies on applying the photochemical UV/TiO2 oxidation process to treat the lignin-containing wastewater for dissolved organic carbon (DOC), color and reducing A254 (the absorption at the wavelength of 254 nm) have been carried out. The data obtained in this study demonstrate that the UV/TiO2 process is effective in oxidizing the lignin thus reducing the color and DOC of the wastewater treated. The combined UV/TiO2 treatment can achieve better removal of DOC and color than the UV treatment alone. Color removal, based on American Dye Manufacture Index (ADMI) measurement, is greater than 99% if the pH is maintained at 3.0 with the addition of 1 g l(-1) TiO2. When 10 g l(-1) TiO2 is applied, the oxidation reduction potential (ORP) value is reached to result in an 88% removal of both DOC and color. A model was developed based on the variation of ORP during the photochemical reaction to simulate the decoloring process. The proposed model can be used to predict the color removal efficiency of the UV/TiO2 process.     

Ammonia inhibition on thermophilic anaerobic digestion

This study evaluated both chronic and acute toxicity of ammonia in thermophilic anaerobic digestion of synthetic wastewater over a range of acclimation concentrations. The inhibition effects of ammonia, in terms of total ammonia nitrogen (TAN), under various pH values and acclimation conditions on thermophilic aceticlastic methanogens were investigated. Completely mixed thermophilic anaerobic reactors operated at a chemical oxygen demand (COD) loading rate of 4 g/lday and a solid retention time (SRT) of 7 days were subjected to TAN concentrations of 0.40, 1.20, 3.05, 4.92, and 5.77 g/l. The reactor operations presented a case of chronic inhibition and it was observed that TAN concentrations of 4.92 and 5.77 g/l caused a drop in methane production by as much as 39% and 64%, respectively with respect to control. Batch anaerobic toxicity assays (ATA) were also performed to evaluate the acute toxicity effects of TAN and pH on methanogenesis at thermophilic condition. Modeling based on the results of ATA indicated that aceticlastic methanogens acclimated to high concentrations of TAN were less sensitive to increase in TAN and could tolerate wider pH ranges. TAN concentration causing 100% inhibition occurred in the range of 8-13 g/l, depending on acclimation condition and system pH.     

Combustion characteristics of spent catalyst and paper sludge in an internally circulating fluidized-bed combustor

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermo-gravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.