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sunxuefei(金币+20, 翻译EPI+1): 2011-01-16 15:01:24
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During Chlorella reproduction, due to the gradual depletion of nutrients and the gradual accumulation of harmful metabolites, a high rate, unlimited reproduction can not be maintained. After a certain period of time, reproduction rate of Chlorella starts decreasing when dead Chlorella increases, resulting in reduced growth rate, which tends to stagnate. After the stationary phase, Chlorella reproduction rate becomes slower and slower. The increasing death finally outnumbers the live ones. Remarkable changes in the form of Chlorella take place, which include emergence of recession-type or cell autolysis, and stagnation of physiological, metabolic activity. Therefore, treating waste water by the first batch of Chlorella fails to achieve set objectives, but a second generation of Chlorella cultivation is required. After a certain period of time in the wastewater, Chlorella pyrenoidosa grows into the stationary phase and decline phase, when algal cells demand little nutrients from the wastewater, resulting in a low removal rate of COD, protein content and salt content. After centrifugal separation, COD still locates somewhere between 60 and 980, which does not meet emission standards. Given there is still a small amount of nutrients in wastewater, this study investigates a second generation cultivation of unaltered algae species in the first-level wastewater by aeration. |
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