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RISS 인기검색어
- 검색키워드
- 저자 : Oktavia Ratnasari (검색결과 1 건)
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A Study on the Wastewater Treatment System by Advanced Phytoreactors
Oktavia Ratnasari University of Science and Technology 2012 국내석사
The increase of human activities in industrial or agricultural sectors to supply global consumptions causes deterioration in environment. In aquatic environment, water eutrophication is known as notorious for primary environment destruction. In atmospheric environment, anthropogenic global warming is continuously becoming one of the most important problems, despite many efforts have been done. It has been recognized that global warming is caused by CO2 emission mainly from fossil fuels. Various methods in capturing and sequestering CO2 have been intensively researched throughout the world. Phytoremediation is one of promising new technologies in addition to conventional treatment systems. This technology works by utilizing plants to remove contaminants in various media such as water, air, and soil. Through phytoremediation process, it may stimulate biological processes or physico-chemical characteristics of plants to aid the process. It also has been applied for treating numerous contaminants including heavy metals, pesticides, petroleum hydrocarbons, chlorinated solvents, explosives, radioactive substances and landfill leachates. These technologies have been broadly used in various fields because of its advantages in economic aspect, sustainability and operation as well as providing aesthetical value. In water environment, aquatic plants play a major contribution for sustaining nitrogen cycle and returning N2 gas back to the atmosphere through bacteria-mediated reactions of nitrification and denitrification. Several studies have demonstrated the effectiveness of these plants to remove nutrients, especially nitrogen and phosphorus, from polluted water. In the aspect of air pollution, studies have proven that phytoremediation has an important function in removing excessive amount of CO2 in the atmosphere by photosynthesis process of plants in terrestrial and aquatic ecosystems. Photosynthesis can produce plant biomass which can be utilized to produce renewable material for bioenergy. Since 1990s, light-emitting diodes (LEDs) have been developed as advanced light sources for indoor plant cultivation, replacing traditional fluorescent and incandescent lamps. LEDs have a very superior life span compared to conventional lamps and excellent features including energy efficiency, specific wavelength, easily modified light intensity and quality, small size, low thermal output, and high photoconversion efficiency. LEDs have been widely developed in indoor cultivation of various plant species, plant tissue culture, space agriculture, algaculture and plant disease reduction. In the aspect of light spectra, blue LED (400-470 nm) and red LED (630-665 nm) match with the absorption spectra of chlorophylls and carotenoids. As for phytochrome for plant growth, their peak absorbance of 660 nm and 730 nm can also be matched with red LED (630-665 nm) and far-red LED (730 nm). Since the discovery of LED technology, research related to plant growth and photosynthesis has been increased. This study was conducted to investigate nutrient removals from wastewater using effective aquatic plants in various systems incorporated into advanced phytoremediation of wastewater. Three types of phytoreactors were studied for their performances in removing nitrogen, phosphorus and organic contaminants. Nutrient removals were determined by kinetics, removal rates, and removal efficiencies. In the experiments using advanced plant growth acceleration technology, the growth rates of studied plants were also measured and compared to plant’s growth rates under controlled condition. The effects of light wavelengths in ABPs, ASBPs and ASCPs were also analyzed. In addition, the effect of CO2 enrichment in ASCPs was also considered. Lastly, prediction of nutrient removal using kinetic models was presented. Surface area occupied by plants and plant’s weights were employed to evaluate the performance of plants (P.stratiotes, E.crassipes and A.gramineus) to remove TN, TP and COD by batch reactors under normal and accelerated conditions. The removal of TN, TP and COD by plants differed between the treatment of light sources (p < 0.05). Using first order kinetic equation, based on unit area, TN removal rates by batch reactors ranged from 1,760 mg N to 3,720 mg N m-2 d-1, while based on unit weight, removals ranged from 862 mg N to 1,990 mg N kg-1 d-1. Area-based TP removals were between 141 mg P and 508 mg P m-2 d-1, and weight-based removals varied from 101 mg P to 283 mg P kg-1 d-1. For COD, area-based removals ranged from 528 to 1,330 mg COD m-2 d-1, and weight-based resulted in the range of 281 and 703 mg COD kg-1 d-1. Water lettuce (Pistia stratiotes) was selected for experiments with advanced plant growth acceleration (PGA) technology. In advanced sequential batch phytoreactor (ASBP), statistical analysis by ANOVA declared that the difference of area-based and weight-based nutrient removal rates by FL and PGA treatments was significant (p < 0.05 for TN, TP and COD removals. TN and COD removals were best achieved by phytoreactors treated using red light (=630+660 nm), while highest TP removal was reached using blue light (=400+440 nm). Further, in experiments using advanced sequential continuous phytoreactor (ASCP), in which different concentrations of CO2 were employed, p < 0.01 validated that kinetic coefficients for TN and TP removals was significantly different between normal and advanced phytoreactors. COD removal showed a p value of 0.08, suggesting that the application of LED didn’t improve the removal of COD in the system. Plants cultivated under advanced reactors showed superior results of growth rates compared to controls. In batch experiment under red light (=660 nm), P.stratiotes showed growth rate of 1.86 times higher than those grown under FL lamps, while for E.crassipes and A.gramineus, their growth rates were 2.14 times and 2.29 times compared to those grown under FL lamps. In ex
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