| As a new biomass energy,microalgae has been received much attention.Microalgae is widely distributed and has strong environmental adaptability,the cultivation area is small,the production cycle is short,and the oil content and protein content of the harvested algae are high,which has great environmental and economic benefits.However,an important problem facing the large-scale cultivation of microalgae is that the cost of raw materials is too high.On the other hand,with the improvement of the word’s population,and the progress of social industry,the situation of water pollution is increasingly severe.A large amount of wastewater that did not meet the standard was discharged into public waters every year,causing a large area of water pollution.Using wastewater to cultivate the microalgae can not only reduce the cultivation cost of microalgae,but also make full use of nutrient salts in wastewater.In this study,three kinds of wastewater were selected for heterotrophic culture of heterotrophic chlorella,and the effects of initial pH,inoculation amount,filling amount,nutrient salt content on the growth and the nutrient accumulation of heterotrophic chlorella were investigated,the utilization of nitrogen and phosphorus in wastewater and the accumulation of protein and grease in algae were also studied.The main contents and results of the study were as follows.1.Heterotrophic chlorella was cultured by using alcohol fermentation wastewater with shaking culture.The results showed that heterotrophic chlorella could grow in the sterilized alcohol fermentation wastewater,and could be improved by adding yeast powder and glucose.The optimal culture conditions affecting the dry weight of the cells were determined by orthogonal experiments as follows,the ratio of yeast powder to glucose was1:25,the initial pH 7.0,the amount of liquid filled 400 mL/L,and the amount of inoculation 25%(v/v).When the amount of inoculation was 20%,the dry weight of the harvested algae could reach 29.6 g/L,in which the intracellular fat content was 34.2%,and the protein content was 15.7%.2.Heterotrophic chlorella was cultured by using urban sewage with shaking culture.The results showed that heterotrophic chlorella could not grow in the sterilized urban sewage,because the carbon source in urban sewage was almost zero,and it was necessary to add a certain amount of carbon and nitrogen for algae to grow.When the organic carbon and the nitrogen source were added,the dry weight of the harvested algae could reach 25.9g/L,well the intracellular fat content was 33.3%,and the protein content was 9.16%.The optimal culture conditions affecting the dry weight of the cells were determined by orthogonal experiments as follows,the initial pH 7.5,the amount of liquid 400 mL/L,and the amount of inoculation 15%(v/v),the ratio of yeast powder to glucose was 1:20.3.Heterotrophic chlorella was cultured by using piggery wastewater with shaking culture.The results showed that there were abundant nitrogen sources for heterotrophic chlorella in piggery wastewater,but the carbon content of which could be directly used was extremely low.When the glucose was added,the dry weight of the harvested algae could reach 24.6 g/L,well the intracellular fat content was 29.4%,and the protein content was 16.5%.The optimal culture conditions affecting the dry weight of the cells were determined by orthogonal experiments as follows,60 g/L of glucose,the amount of liquid400 mL/L,the amount of inoculation 15%(v/v),initial pH 7.0.4.The feasibility of recycling with algae wastewater were investigated by using algae wastewater with shaking culture.The results showed that heterotrophic chlorella could grow well by adding 3 g/L of yeast powder and 60 g/L of glucose to the algae wastewater,and the dry weight could reach 21.5 g/L,indicating that the algae wastewater could be reused in microalgae culture. |
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