High Effective Culture And Characterization Of Microalgae And Its Application Performance Evaluation

Microalgae have the characteristics of fast growth,widespread and adaptable.Moreover,the harvested microalgal cells have extensive commercial application prospect in many fields.Under the situation of increasingly water scarcity and water eutrophication,using eutrophication wastewater to culture microalgae not only could realize the purification of wastewater,but also reduced the cost of microalgae culture.In this study,microalgae was applied to treat the artificial wastewater.The biomass productivity,nitrogen and phosphorus removal rate were used as indicators to evaluate the performance of wastewater treatment.The relevant research results will provide reference for large-scale wastewater treatment by microalgae.The conditions for microalgal cell growth and N/P removal from artifical wastewater were investigated.The results show that sodium bicarbonate and magnesium sulfate are the most critical nutrients.The nitrogen and phosphorus removal rate of Desmodesmus sp.F51 were higher than that of Chlorella sorokiniana FACHB-275 under the same culture conditions.Both cell growth rate and N/P removal rate increased when sodium bicarbonate concentration was increased to 0.275 g/L,while further increases in sodium bicarbonate concentration did not lead to better results.The magnesium sulfate concentration in the range of 0.045 to 0.075 g/L could enhance the cell growth of strain F51.Inhibition of cell growth occurred with the concentrations of ammonia and phosphorus above 30 mg/L and 10 mg/L,respectively.When adding 0-5 g/L salt,as well as operating at 26? and pH 7,the performance of cell growth and wastewater treatment could be effectively improved.The effect of different cultivation strategies on microalgal cell growth and N/P removal from artifical wastewater was investigated under indoor conditions with 36 L cylindrical photobioreactor.The results show that the best cell growth and N/P removal occurred when aeration ratio and inoculum size were 0.08 VVM and 12 mg/L,respectively,under batch cultivation.Semi-batch operations with 75%replacement of culture broth resulted in the highest biomass productivity(2.3 mg/L/d),nitrogen removal rate(97.7%)and phosphorus removal rate(91.7%).The highest biomass productivity,nitrogen and phosphorus removal rate were 1.97 mg/L/d,97.4%and 76.0%,respectively,when the continuous culture was operated with a HRT of 80 h.Moreover,it was found that Desmodesmus sp.F51 was able to adapt outdoor changeable conditions,and the removal of phosphorus showed a fluctuate declining trend under outdoor conditions.The effect of different heavy metals(including copper,cadmium and lead)on microalgal cell growth and N/P removal from artifical wastewater was investigated.The results show that cell growth inhibition occurred when the concentrations of copper and cadmium reached 1.5 mg/L and 0.3 mg/L,respectively.Moreover,the 60 h-EC50 values of copper and cadmium were found to be 8.9 mg/L and 33.8 mg/L,respectively,which should be avoided during the microalgae-based wastewater treatment.The cell growth rate of strain F51 increased with an increase in the lead concentration,and the highest specific growth rate was obtained when the concentration of lead was 27 mg/L,along with the N and P removal rate of 97.2%and 96.2%,respectively.Desmodesmus sp.F51 showed an excellent absorbency to the heavy metals in artifical wastewater with high adsorption rate above 90%.The results of Fourier Transform Infrared Spectrometer study indicated that hydroxyl,carbonyl and acylamino groups were the main binding sites for cadmium and lead biosorption,while hydroxyl group was mainly responsible for biosorption of copper.