Research On The Technology Of Flocculating Choorella

After flocculating chlorella with sulfate as flocculant,the residual metal ions in the waste liquor will pollute the ecological environment if discharged directly into the natural water body or under the surface without some degree of treatment.In the flocculation process of microalgae,the kind and amount of flocculant will affect the recycling of supernatant.The supernatant obtained by filtration was used for the re-culture of chlorella vulgaris,which not only saved a lot of culture medium,but also protected the environment to a certain extent,reached the requirement of sustainable development and realized the maximization of economic benefits.However,a certain amount of flocculants will remain in the residual clear liquid after the microalgae is flocculated by inorganic salts,and the use of these supernatants in the cultivation of microalgae will increase the risk of flocculation and aggregation,and affect the efficiency and stability of the cultivation of microalgae,therefore,it is urgent to study the relationship between the residual amount of flocculant and the culture efficiency and stability of microalgae in the process of subsequent microalgae cultivation,the study laid a theoretical foundation for the large-scale reuse of the flocculated microalgae.Firstly,ferric sulfate and aluminum sulfate were selected as flocculants,and the supernatant needed for the experiment was obtained by filtration under the optimum flocculating condition.A single-factor test was then performed to determine the horizontal range of the selected factors.The optimum supernatant addition ratio of chlorella was 10%-30%,light intensity was 4000-8000Lux,aeration rate was 1.5-2.5L/min.The optimum range of factors was determined by single-factor experiment,and the optimum culture parameters of chlorella were obtained by selecting three-factor and five-level quadratic orthogonal rotating center combination design,and the regression model was established by Design-Expert software,the optimal culture conditions of chlorella were obtained when supernatant was reused.The interaction of factors and its effect on the corresponding indexes were analyzed by response surface methodology.The optimal growth conditions of chlorella pyrenoidosa,the response value of OD₆₈₀and the concentration of ions in the solution were determined.Taking into account the factors such as the Operability of the experimental process and the economic cost,it was determined that the optimal culture process of Chlorella OD₆₈₀after flocculation with ferric sulfate was as follows:The addition ratio of clear liquid was 24%,the light intensity was 6700Lux,and the aeration rate was 2L/min,the OD value was 1.661,the Fe³⁺concentration was 0.02g/L,the growth condition of Chlorella was the best,and the Fe³⁺concentration in the culture medium was the lowest.After flocculation with aluminum sulfate,the optimal culture conditions of Chlorella OD₆₈₀were as follows:The addition ratio of clear liquid was 26%,the light intensity was 6700Lux,the aeration rate was 2L/min,the OD value was 1.22,the Al³⁺concentration was 0.049 g/L,the growth condition of Chlorella was the best,the concentration of Al³⁺in culture medium was the lowest.