The Study On The Culture Conditions Of Energy Microalgae Chlorella Vulgaris In The Wastewater

Fossil fuels such as oil reserves was limited,which also brought about the global warming and the changes of ecological system.On the other hand, eutrophication of lakes and river in which frequent outbreaks of algal was without of control were getting more and more serious. Studies had shown that Chlorella contained rich lipid and some hydrocarbon; lipid can be used to produce biodiesel; after extraction of hydrocarbon can be processed into gasoline and diesel .Chlorella can also absorb nitrogen, phosphorus and other nutrients and heavy metal of water in growing process to purify water. The effect of temperature, light intensity, pH value of wastewater and nutritional concentrations of wastewater on the growth,lipid or hydrocarbon accumulation of Chlorella vulgaris were studied in this experiment, which can provided basis for large scale using Chlorella vulgaris to purify water and produce biomass energy. The main conclusions of this thesis were as follows:(1)The medium was original wastewater.The effect of temperature, light intensity and pH value of wastewater on growth and lipid accumulation of Chlorella vulgaris were studied individually.Five gradient of temperature were 15℃, 20℃, 25℃, 30℃and 35℃;Five gradient of light intensity were 1500lux,3000lux,4500lux,6000lux and 8000lux; Five gradient of pH value of wastewater were 3,5,7,9 and 11. The results of one way anova and multiple comparison showed that: The trend of effect of temperature on growth and lipid accumulation of Chlorella vulgaris in wastewater was consistent,it was 25℃>30℃>20℃>35℃>15℃.The trend of effect of light intensity on growth of Chlorella vulgaris in wastewater was 4500lux>6000lux>8000lux>3000lux>1500lux; The trend of effect of light intensity on lipid accumulation Of Chlorella vulgaris in wastewater was 4500lux>3000lux>1500lux>6000lux>8000lux. Chlorella vulgaris grew badly when pH value of wastewater were 3,5 and 11;The biomass and lipid conten of Chlorella vulgaris were the highest when pH value of wastewater was 7,which were slightly lower when pH value of wastewater was 9.(2)Medium was the wastewater into which adding exogenous source.At the first,the influence of different concentrations of inorganic carbon, total nitrogen and total phosphorus of wastewater on biomass, lipid content and hydrocarbon content of Chlorella vulgaris were studied individually. The setting of inorganic carbon concentrations were 2mg/L,6mg/L,12mg/L,18mg/L and 24mg/L; The setting of total nitrogen concentrations were 15mg/L,20mg/L,25mg/L,30mg/L and 35mg/L; The setting of total phosphorus concentrations were 1mg/L,1.5mg/L,2mg/L,2.5mg/L,3mg/L and 3.5mg/L. The results of one way anova and multiple comparison showed that: The biomass and hydrocarbon content of Chlorella vulgaris were the highest at the inorganic carbon concentration of 6 mg/L when the highest lipid content was at the inorganic carbon concentration of 12mg/L. The biomass of Chlorella vulgaris was the highest at the total nitrogen concentration of 25mg/L; the highest lipid content was at the total nitrogen concentration of 15mg/L; the highest hydrocarbon content was at the total nitrogen concentration of 20mg/L. The biomass and hydrocarbon content of Chlorella vulgaris were the highest at the total phosphate concentration of 2mg/L when the highest lipid content was at the total phosphorus concentration of 1.5 mg/L. Secondly we designed two level of three factors of orthogonal test on the basis of single factor experiment. The level selected was shown as below: the inorganic carbon concentrations were—and—, the total nitrogen concentrations were—and—, the total phosphate concentrations were—and—.The result showed that: The growth and energy efficiency of Chlorella vulgaris were the best at the inorganic carbon concentration of—, the total nitrogen concentration of—, the total phosphorus concentration of—in the wastewater(3)The preliminary exploration on the open cultivation of Chlorella vulgaris in wastewater,the controlled trial was designed as shown: Sterilization and sealing,sterilization and open,no sterilization and sealing,no sterilization and open. The result showed that: No sterilization and open started to decline after six days, other treatment group began to fail after twelve days. The trend of growth of Chlorella vulgaris before recession was sterilization and open > no sterilization and open> no sterilization and sealing >sterilization and sealing.