| Summary: | 碩士 === 東海大學 === 化學工程與材料工程學系 === 105 === With the improvement of human quality of life, environmental problems at the same time become the focus of global attention. Green house gas emission and heavy metals pollution has become a global issue of concern due to their higher toxicities. Especially, Cr(VI) is introduced in the environment mainly as a consequence of its industrial use and it has been causing serious environmental pollution due to its carcinogenicity.
In this study, the possible use of Chlorella vulgaris biomass as an alternative biosorbent for Cr (VI) removal was investigated. Therefore, the use of C. vulgaris has the ability to adsorb heavy metals in wastewater, and to explore the effect of microalgae adsorbing heavy metal Cr(VI). The results showed that microalgae can removal of Cr (VI). And then extend the discussion of microalgae how to remove heavy metals Cr (VI). It was found that glutathione (GSH) in C. vulgaris could decrease the heavy metal Cr(VI) into Cr(Ⅲ) in the process of heavy metal removal in microalgae, and the greater the concentration of glutathione (GSH), the greater the reduction of heavy metals Cr (VI). But the reaction sequence is microalgae reduction enzyme exhausted, the antioxidant glutathione will be the reaction. It is confirmed that Cr (VI) is not only adsorbed by algae, but also a small part of Cr (VI) is reduced to Cr(Ⅲ) by reduction enzyme and antioxidant during the removal of heavy metal Cr (VI) by microalgae.
Additionally In Taiwan, many domestic sewage and production wastewater are often discharged into rivers, untreated, high levels of nutrition, phosphorus, organic matter and other waste water directly pollute the river, causing the river ecology to be affected and damaged, The river suffered from severe pollutions has gradually become muddy and foul, and then lots of mosquitos and insects have bred in it. Therefore, use of Chlorella has the ability to metabolize organic matter and other high nutrient capacity and it's culture cycle is short and stable, to explore the use of batch and continuous reaction to culture C.vulgaris and remove chemical wastewater (COD). According to the comprehensive experimental results, 50% of glucose carbon source's R. glutinis fermentation wastewater is the most suitable microalgae growth environment. The chemical oxygen demand can be reduced about 10000 mg/L day by batch. In the continuous culture study, the 5-days hydraulic retention time is most suitable for microalgae growth and cell accumulation, culture for 10 days can reduce wastewater chemical oxygen demand 7000 mg/L in 10 days .The next discussion is best condition of scale up 5 times of culture's reaction volume and changes the reaction form. In the batch culture, the chemical oxygen demand in the 50% wastewater can be reduced to 10000 mg /L of COD in 10 days, and the chemical oxygen demand in the wastewater can be reduced by about 14000 mg/L in the HRT 5 days. It is found that the scale up reaction volume and change the reaction form can increase the degree of removing chemical oxygen demand in the wastewater, and the best reaction conditions for the reduction of chemical oxygen demand in the continuous reaction were obtained. The whole systom can maintain algal concentration of about 2.0 g/L, with good chemical oxygen demand removal effect.
Furthermore, in this sustainable cultivation system of aerobic yeast -Rhodotorula glutinis and photosynthetic microalgae -Chlorella vulgaris, a yeast and a microalgae were grown in two separate reactors connected by their gas transportation. The aerobic yeast provides CO2 for the growth of microalgae via photosynthesis process as both carrying out the production of lipids, and efficient CO2 fixation by Chlorella vulgaris. Moreover the aerobic yeast R. glutinis provides 0.142 kg CO2 / Day．g Biomass and C. vulgaris can utilize 1.08 kg CO2/ Day．g Biomass. Microalgae can utilize CO2 of emission gas from the yeast fermenter efficiently up to 35.6 %. It was demonstrated that this sustainable cultivation system of the yeast Rhodotorula glutinis and the autotrophic growth of the microalgae Chlorella vulgaris was successful in the reduction of CO2 emission.
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