Marine Aquaculture Wastewater Treatment By Marine Single Cell Algae And Its Oil Production Capacity

Marine aquaculture wastewater can be purified by marine single cell algae and photosynthetic bacteria?PSB?.the eutrophication of receiving water can be resolved by them.Algal oils could be extracted to produce biofuel after wastewater treatment.Meanwhile,algae and PSB cells could be used as animal fertilizer.Thus,this is a kind of biotechnology of reclamation of sewage.The purifying capacity of Dunaliella salina,Platymonas subcordiformis and Chlorella pyrenoidosa cells in marine aquaculture wastewater were studied in this paper.The effects of ammonia concentration on the removal efficiency of pollutants were investigated.The results showed that microalgae had a certain tolerance to ammonia nitrogen,and high concentration of ammonia nitrogen had no negative effects on cell proliferation?chemical oxygen demand?COD??mmonia nitrogen?orthophosphate phosphorus removal rates of microalgae.Three factors and three levels orthogonal experiment were used to detect the COD,ammonia-nitrogen and orthophosphate removal rates in wastewater.The Dunaliella salina,Platymonas subcordiformis and Chlorella pyrenoidosa cells obtained the optimum purification condition,where cell density were 3-5 million cells/gel beads,300 gel beads in150 mL and starvation time ranged from 0-24 hours.COD removal rate were above 75%,Nitrogen and phosphorus removal rate were above 95%after 4 days.The cell proliferation of three marine algae was 48.48%,43.81%and 40.34%,respectively.The cells of Dunaliella salina,Platymonas subcordiformis,Chlorella pyrenoidosa and photosynthetic bacterium were co-immobilized to purify marine aquaculture wastewater.The results showed that the removal rate of COD was significantly increased after 4 days,and the increase of ammonia nitrogen and orthophosphate phosphorus removal efficiency were not significant.After the cells of Dunaliella salina,Platymonas subcordiformis and Chlorella pyrenoidosa respectively were co-immobilized with PSB1,The removal rate of COD was88.46%,90.38%and 93.23%.Compared with the immobilized algae,COD removal efficiency increased 15.38%,22.11%,and 23.08%.Compared with PSB1 alone,the removal efficiency of COD increased 15.38%,17.30%and 21.15%,respectively.Co-immobilized with PSB2,The cells of Dunaliella salina and Platymonas subcordiformis and Chlorella pyrenoidosa respectively obtained COD removal rate 97.12%,92.12%and 93.27%.Compared with microalgae alone,COD removal rate increased 24.04%,28.85%and 22.12%,respectively.Compared with immobilized PSB2 alone,COD removal rate increased 24.04%,24.04%and20.19%,respectively.Algal oils extraction and contents determination of Dunaliella salina,Platymonas subcordiformisand and Chlorella pyrenoidosa cells after marine aquaculture wastewater treatment were studied.The results showed that the oil contents of three kinds of marine microalgae were 22.05%,12.42%and 17.20%after purification of wastewater.The oil contents of three kinds of marine microalgae increased 5.00%,5.87%and 8.96%after starved for 48 h compared with the non-starvation treatment respectively.After addition 0.1 mmol/L Fe³⁺,the oil contents increased 8.49%,6.20%and 11.62%compared with the control respectively.The optimum pH value of the medium for oil production of three kinds of marine microalgae was 8,6 and 9.And the oil contents of three kinds of algae increased9.53%,4.28%and 8.90%,respectively.It has important theoretical research and application significance to purify marine aquaculture wastewater by using cells of Dunaliella salinaand,Platymonas subcordiformis,Chlorella pyrenoidosa and photosynthesis bacterium.