The Research Of Nitrogen And Phosphate Removal Ability By Immobilized Chlorella Sp. In Municipal Sewage

Chlorella sp. isolated from the sewage entrapped in alginate and chitosan beads was usedfor the treatment of municipal sewage. Some factors had been considered about nitrogen andphosphate removal efficiency and changes in the process of algae growth in this paper, suchas cell loading, immobilization, starvation. The results showed that, in a certain range of cellloading, nitrogen and phosphorus removal efficiency increased with the increase of cellloading. Chlorophyll a contents demonstrated that immobilized method did not affect thegrowth of cells. Nitrogen and phosphorus removal efficiency and chlorophyll a content ofalgal cells were higher than immobilized by alginate sodium. However, the phosphorusremoval efficiency was not obvious. After immobilized by chitosan, the nitrogen andphosphorus removal efficiency of5million algae cells per beads was the optimal, which was93.6%and97.5%respectively5days later. Cell proliferation was not effected by starvationduring48hours, but it can significantly enhance the nitrogen and phosphorus removalefficiency within3days. A net increase of nitrogen and phosphorus removal efficiency was12.3%and7.5%respectively.Chlorella sp. was immobilized as alginate beads to treat sewage wastewater. They wereplaced into air-lift photo-bioreactor for sewage treatment. The removal rate ofammonia-nitrogen and orthophosphate in the wastewater were detected after Chlorella sp.beads were put into the reactor in different cell density; the effects of density and starvationtime on removal rate of ammonia-nitrogen and orthophosphate were studied; at the same timethe chlorophyll a content of Chlorella sp., cell density in beads were discussed. The resultsshowed that: after48hours of starvation, the algae beads of4million cells per bead, NH4+-Nremoval rate reached99%in8hours. The removal rate of PO43--P was100%in4hours.Chlorophyll a contents increased in the process of wastewater treatment. The increase ofchlorophyll a content implied survival ability of algae during the treatment.Using immobilized screens, with100%relative humidity and air starvation and darkdecontamination circle mode, ammonia-nitrogen and orthophosphate removal efficiency weredetected in different algal cell densities and ratio of nitrogen to phosphorus. Results showedthat the algal screens in N/P (10) had higher removal efficiency. Ammonia-nitrogen removalrate can reached90%after8hours and the removal rate of orthophosphate was100%. Aftertwo starvation circulation processing, Ammonia-nitrogen removal efficiency increased approximately8%, and orthophosphate removal rate reduced. After treatment, chlorophyll acontents increased obviously.