Enhancement Of Se Removal By Chlorella Vulgaris And Reuse Of Se Containing Algal Biomass As Biofuels

The element selenium(Se)is regarded as an essential micronutrient for many organisms,including humans,mammals,microorganism,fish,algae and waterfowls,and there is a narrow window between Se nutritional deficiency and potential toxicity.High Se concentrations in aquatic environment could cause hazardous effects in the state of equilibrium within communities of aquatic ecosystems and local populations.While the inorganic form of selenite(Se(IV))and selenate(Se(VI))are the dominant soluble forms of Se in the aquatic environment,and normally result from industrial and agricultural sources or environment cycles.Chlorella vulgaris has shown astonished ability to remove Se from aquatic environment and the major removal way was volatilization.And this bioremediation approach also has the economic advantage.In order to increase more environmental and economic benefits,we supposed to put flue gas to the algal Se treatment system.And then,using microcosms to explore the possibility of recycling Se containing cells of C.vulgaris for biofuel production,i.e.,fatty acids and hydrogen.These research indicate that significantly Se volatilization and accumulation mass were observed in high CO2 concentration treatments in the presence of selenite.At 24h,the greatest Se removal rate of 95%and 92%was obtained for the algal supplied with selenite and selenate,respectively,under 5%CO2 concentration treatment.And 81%and 79%of the removed Se was translated to organo-volatilization Se which could minimize the Se risk to wildlife.While the disposal of Se containing in algal biomass was still an issue of concern.Firstly,this research suggests algal Se could be released back to water,posing risks to aquatic wildlife.Thus,we further explored the possibility of using C.vulgaris to remove Se and produce lipid and hydrogen simultaneously.Our results show the higher percentage of saturated fatty acids,especially palmitic acid,was found in the S deprived algae exposed to either selenate or selenite,although the highest lipid content(21.9%)was found in the selenite treated algae in full BG11 medium.In addition,compared with the Se free algae,hydrogen production rate was 2.1-and 4.3-fold higher for the selenate and selenite treated algae,respectively.Se removal efficiency achieved by the selenite treated algae through accumulation and volatilization was 2.3-fold higher than the selenate treatment under hypoxic condition with S deprived,which is in contrast to the results obtained under aerobic conditions.