Research About Using Eutrophic Wastewater Culture Energy Micro Algae Botryococcus Bra Unii

At present, the problems about global energy shortage and environmental pollution have prompted thedevelopment and utilization of renewable and clean new energy. On the other hand, the water pollution isalso very prominent, water nutrition load dramatically increased and accumulated, making the watereutrophication process speed up quickly, deteriorating water quality, losing its function. Botryococcusbraunii contains lipids, hydrocarbons and other energy materials. Botryococcus braunii can use thenutrition elements in water, and reduce the nutrient load of water. Eutrophic wastewater of fishpondsfiltered twice was for the culture mediums. Using single-factor experiments and orthogonal tests to explorethe effects of environmental factors and nutritional elements on the growth and capacity of Botryococcusbraunii in wastewater, which provided basis for optimizing the culture conditions and obtaining highproductivity of Botryococcus braunii,(1) Effects of light intensity and pH value of wastewater on the growth and productivity ofBotryococcus braunii.Using wastewater as the culture mediums, the temperature was at25℃, light dark ratio was12h:12h.Five gradients of light intensity were2000lux,4000lux,6000lux,8000lux, and10000lux. The resultsshowed that: when the light intensity was10000lux, biomass achieved the maximum, and the average was0.7331g/L; when the light intensity was4000lux, total lipids achieved the maximum, and the average was20.20%; when the light intensity was6000lux, total hydrocarbons achieved the maximum, and the averagewas28.90%.Using wastewater as the culture mediums, the temperature was at25℃, light dark ratio was12h:12h,light intensity was5000lux. Five pH gradients were:5.5,6.5,7.5,8.5and9.5. The results showed that:Botryococcus braunii toleranced wide range of the pH value. When the wastewater pH value was6.5-8.5,Botryococcus braunii grew well and obtained high lipids content and high hydrocarbons content. When thewastewater pH value was7.5, biomass, total lipids, and total hydrocarbons all reached the maximum, theaverage were0.6118g/L,19.84%,31.31%.(2) Effects of different carbon source at different concentrations that in wastewater on the growth andproductivity of Botryococcus braunii. Using NaHCO3as inorganic carbon source, five gradients of carbon concentration were2mg/L,5mg/L,10mg/L,15mg/L and20mg/L. The results showed that: when the exogenous inorganic carbonconcentration in wastewater was5-10mg/L, biomass and total lipids content were the highest, the averagewere and; when the exogenous inorganic carbon concentration in wastewater was15mg/L, totalhydrocarbons content was the highest, the average was.Using glucose as carbon source, five gradients of glucose concentration were5mg/L,12.5mg/L,25mg/L,37.5mg/L and50mg/L. The results showed that: when the glucose concentration in wastewaterwas50mg/L, biomass was the highest, the average was0.6921g/L; when the glucose concentration inwastewater was37.5mg/L, total lipids achieved the maximum, the average was23.8%; when the glucoseconcentration in wastewater was25mg/L, total hydrocarbons achieved the maximum, the average was28.65%.Compared with the highest data which only add inorganic carbon source, biomass and total lipidscontent increased by0.0921g/L, and5.38%, total hydrocarbon content decreased by5.9%. Therefore,glucose can significantly promoted the growth and lipid accumulation of Botryococcus braunii, but bad forhydrocarbon accumulation.(3) Effects of different nitrogen source at different concentrations that in wastewater on the growthand productivity of Botryococcus braunii.Using KNO3as nitrogen source, five gradients of nitrogen concentration were2mg/L,5mg/L,10mg/L,15mg/L and20mg/L.The results showed that: when the nitrogen concentration in wastewater was15mg/L,biomass achieved the maximum, the average was; when the nitrogen concentration in wastewater was2mg/L, total lipids achieved the maximum, the average was; when the nitrogen concentration in wastewaterwas20mg/L, total hydrocarbons achieved the maximum, the average was.Using urea as nitrogen source, five gradients of urea concentration were were4mg/L,10mg/L,21mg/L,32mg/L and42mg/L. The results showed that: when the urea concentration in wastewater was32mg/L biomass achieved maximum, the average was0.4856g/L; when the urea concentration inwastewater was21mg/L,total lipids and total hydrocarbon achieved the maximum, the average were18.68%and24.03%. Comparing with the highest data that only added KNO3in wastewater, the biomass,total lipids and total hydrocarbons decreased by0.1024g/L,8.96%and11.07%. So, nitrate nitrogen sourceis more suitable than urea for the growth, total lipid, and total hydrocarbon accumulation of Botryococcus braunii.(4) Effects of different phosphorus concentrations in wastewater on the growth and productivity ofBotryococcus braunii.Using KH2PO4as the phosphorus source, five gradients of phosphorus concentrations were0.2mg/L,0.5mg/L,1.0mg/L,1.5mg/L and2.0mg/L. The results showed that: when the phosphorus concentration inwastewater was2mg/L, biomass achieved maximum, the average was; when the phosphorus concentrationin wastewater was1.5mg/L, total liplids content and total hydrocarbons content achieved maximum, theaverage, were.(5) On the basis of single factor experiments designed an orthogonal experiment of three factors andtwo leves which investigated exogenous inorganic concentrations of carbon, concentration of total nitrogen,concentration of total phosphorus in wastewater on the productivity of Botryococcus braunii. The resultsshowed that: the best exogenous inorganic carbon concentration was; the best total nitrogen concentrationwas; the best total phosphorus concentration was.