Screen Of High-Lipid Microalgae Strains With Culturing By Municipal Wastewater And Optimize Culture Condition

Water shortage and energy crisis are two major problems which the humanity are facing. On the one hand the massive sewage has not been effectively processed and dispersed into the rivers directly which cause the pollution, on the other hand, as a substitute for fossil fuel, the clean energy biology diesel oil cannot be produced continually because of the lack of material. But high-fat microalgae can grow in the wastewater containing nitrogen , phosphorus and other nutrients, which can not only remove the pollutant in sewage, but also can change the sewage into resources, which will relieve the problem of energy shortage .The thesis researches the choosing of the high-fat microalgae growing in the city sewage and the optimization of culture conditions, which will be a good application and has practical significance.In this paper, chlorella pyrenoidosa is optimized by Screening Experiment in five high-fat species microalgaes. Using some experiment methods to investigate various environmental factors influence on the biomass of algae and the amount of fat in synthetic sewages, including of ammonia, urea, nirate, phosphorus, Fe³⁺, Mg²⁺, illumination intensity, photopdriodicity, pH and CO₂. Also using actual wastewater as medium to culture the microalgae to verify the previous results and analysis the growth of microalgae and the removal of pollutants.The concultion of the thesis are shown as following:1) The filtered Chlorella pyrenoidosa can grow fast and contains the highest fat in five kinds of algae in synthetic sewages and actual wastewater, which can meet the requirements of the producing of biodiesel.2) High concentration of ammonia and urea have a certain extent on the inhibition of algae growth, ammonia as a nitrogen source is favorable to algal cells fat synthesis. Different concentrations of phosphorus have different influence the algal growth, but has no significant effect on fat mass. CO₂ concentration of 2% is best for algae growth and fat synthesis.3) In 1000lux-12000lux range, the higher light intensity makes higher biomass of algal cells, and lower fat content, the maximum amount of algal biomass and fat is 0.84g / L and 0.16g / L in 12000lx and 4000lx.With illumination time increased, the impact of biomass and fat are at first increased and then decreased. Time of 19h in the light for maximum algal biomass, is 0.93g / L, at 9h and 14h to achieve maximum fat content is 0.25g / L.4) The biomass of microalgae in high concentration of iron is better than low iron medium. Magnesium ions can promote the growth of chlorella pyrenoidosa, when the concentration of magnesium ions is 0.5mM total lipid is the largest, 0.25g / L.5) The growth of algae species between the pH range 4-9, after three days of training with different initial pH values are 6.9-7.4,under different initial pH, amount of fat is lower.6)Optimum condition of chlorella pyrenoidosa with multi-factor for oil accumulation is illumination time is 23h, ammonia concentration is 125mg/L, the concentration of Fe³⁺ is 0mM, light intensity is 9000lx, the concentration of phosphorus is 14mg/L, the concentration of Mg²⁺ is 0.18mM, the concentration of CO₂ 1.3%, the fat yield up to 0.28g/L.