| Summary: | 碩士 === 國立交通大學 === 生物科技系所 === 102 === Microalgae cultured with wastewater are benefit for minimizing the usage of freshwater, reducing the cost of nutrient addition, removing nitrogen and phosphorus from wastewater and producing microalgal biomass. Livestock wastewater derived from manure was treated by solid-liquid separation, anaerobic treatment and aerobic treatment. Recently, microalgal cultivation with wastewater is being a demand of water and nutrients in microalgal cultivation as a feedstock of biodiesel. The aims of this research are to develop the microalgal culture operation to efficiently produce microalgal biomass and oil for biodiesel production by using swine wastewater from a livestock farm.
Growth rates and lipid contents of the microalga Chlorella sp. cultured with different ratios of the wastewater in a batch culture were firstly explored. The biomass productivity of the Chlorella sp. cultured with 100% wastewater was 0.681 g/L/day, which was approximately 1.5-fold higher than the culture with medium. The microalgal lipid content cultured with the 25% wastewater was approximate 30% (w/w). Over 65% of lipid of the Chlorella sp. cultured in wastewater is suitable as resources for biodiesel production. The wastewater bioremediation by the Chlorella sp. cultures was around 50% in removal efficiency of total nitrogen and almost 100% removal efficiency of total phosphorus in the livestock wastewater.
In order to yield the microalgal biomass and lipid of microalgae efficiently and sustainably, the operation of semi-continuous cultures with half microalgal broth replacement was performed. Because of the gradually lower growth efficiency of the Chlorella sp. in semi-continuous cultures after each replacement, optimizing the components and concentration of extra nutrient added in the 100% wastewater was investigated. The maximum biomass productivity and lipid content of Chlorella sp. cultured with 100% wastewater added 10% of extra nutrients (culture medium) in the semi-continuous cultures were 1.18 g/L/day and 20.6%, respectively. The Chlorella sp. cultured in 100% wastewater with 10% extra nutrient addition by the operation of 2-day, 3-day and 4-day replacement and a period of 12-day culture was investigated. The results show that the biomass productivity per day and total biomass production in the 12-day period in 2-day replacement were 1.09 g/L/day and 12.2 g/L, respectively, which were higher than those in the other replacement operations.
In summary, our experimental results mentioned above confirm that the Chlorella sp. cultured in livestock wastewater can produce microalgal biomass and accumulate lipid efficiently. In addition, the semi-continuous culture operation for microalgal culture using 100% livestock wastewater was established to produce microalgal biomass and oil for biodiesel production and wastewater utilization.
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