Study On Growth Of Chlorella Vulgaris And Removal Of Nitrogen And Phosphorus In Source-Separated Urine

Source-separation system contributes to the separation, collection and treatmentof urine. Source-separated urine contains high concentration of nitrogen andphosphorus compounds, with pollution and resource characteristics. As a kind ofadaptable microalgae, Chlorella can take up nitrogen and phosphorus in wastewaterto achieve their own growth, and turn contaminants into biological resources andrenewable energy at the same time. Cultivating Chlorella in source-separated urinecan achieve nitrogen and phosphorus removal as well as resource recycling,presenting a good prospect. In this thesis, Chlorella vulgaris was cultivated in themedium of source-separated urine and the characteristics of algal growth and nutrientremoval were studied.The algae could grow well in real source-separated urine, with an ammoniumconcentration of180-360mgN/L. When the algae were cultivated in undilutedsource-separated urine compared with standard nutrient solution, the growth rate wasincreased with no significant changes in lipid content. The algae cells could beapplied to the production of biodiesel.The pH of culture decreased obviously due to the uptake of ammonia by algalcells. The algae could grow fast and continuously only in relatively stable pH range.The growth rates were close when pH was between6.0and8.0. When the pH ofsource-separated urine was higher than8.0, algal cells were strongly inhibited byammonia, while pH lower than6.0lead to acidification and algal death. When aeratedwith5%carbon dioxide, the growth rate and cell concentration were increasedsignificantly. The optimal conditions for algal growth were as follows: the undilutedsource-separated urine be used as culting medium,5%carbon dioxide be aeraed intothe medium, and the pH be controlled to7.0.It was found that the unit cell removal was decrased with the aeration of carbondioxide or the increase of ammonia concentration, while the growth rate wasincreased with the same methods. Factors favorable for algal growth could alsopromote the removal of nitrogen and phosphorus in source-separated urine. In optimal growth conditions, the removal of TN and TP were60.7mgN/L and7.0mgP/Lrespectively.The effects of ammonia and urea on algal growth proved to be conversed. Thealgal growth rate decreased gradually with the increase of ammonia concentration,but increased with the increase of urea concentration. The dilution ofsource-separated urine could reduce ammonia inhibition, but the simultaneousdenutrition caused decrease in algal growth rate and nutrient removal. As it hadhigher urea concentration and lower ammonia concentration, low decomposedsource-separated urine seemed to be suitable medium for algal growth and nutrientremoval.