Study On Treatment Of Rural Sewage By Chlorella Vulgaris And Its Resource Utilization

With the development of national economy and the improvement of environmental quality,the problem of urban sewage and industrial wastewater treatment has been gradually solved,but the treatment and control of rural sewage needs to be further improved.Rural domestic sewage is rich in nutrients such as carbon,nitrogen,phosphorus and various elements needed for microalgae growth,which can be used as a culture medium for microalgae.Microalgae can purify sewage through its own proliferation and metabolism process and harvest microalgae biomass at the same time,thus realizing the coupling between sewage purification and microalgae productivity and achieving the purpose of wastewater resource utilization.In this paper,on the one hand,Chlorella vulgaris was used as an experimental algae species to study its growth in rural domestic sewage and its purification effect on rural domestic sewage;on the other hand,Chlorella vulgaris cultivated from rural domestic sewage was used as the research object to analyze its nutritional components,and its intracellular active substances were extracted as liquid fertilizer by ultrasonic wave to study the spraying effect of Chlorella vulgaris extract on crops.The experiment of using Chlorella to treat rural domestic sewage shows that:(1)Chlorella vulgaris grows well in rural domestic sewage,and the biomass accumulation speed is fast.In batch culture experiment,the average biomass yield of Chlorella vulgaris reaches 31.8 mg/L;During the culture process,the N/P value increased slowly with time,and remained between 6.89 and 7.69.The quality of rural sewage was suitable for Chlorella cultivation.In the semi-continuous culture experiment,the biomass concentration of Chlorella vulgaris is stable after the system is stabilized,and the highest concentration can reach 93mg/L.Chlorella vulgaris has a certain effect on the removal of pollutants in rural sewage,in which the removal rates of chemical oxygen demand(COD),total nitrogen(TN)and total phosphorus(TP)are 77.08%,33.01% and 38.23%respectively,and the effluent concentrations of COD,TN and TP are 53.6mg/L,28mg/L and 3.7mg/L respectively(2)By measuring the nutritional components of Chlorella vulgaris,it was found that its crude protein content was 32%,crude total sugar content was 23%,crude total fat content was 25%,and the contents of total sugar and total fat were higher than those of Chlorella vulgaris cultivated in other ways.Chlorella vulgaris cultivated in rural sewage could be cultivated as sugar-producing and lipid-producing algae.The TN and TP contents of Chlorella vulgaris were 7.8% and 2.7%,respectively.Spraying Chlorella extract on crops found that:(1)Spraying Chlorella extract diluted 200 times on apples can effectively improve the yield and quality of apples,in which the yield increased by 10.3%;Single fruit has increased by 3%;The ratio of solid to acid increased by 47.1%.The output value per mu increased by 4,862 yuan.Spraying cultured Chlorella extract can endogenously remove pesticide residues from apples.(2)Taking conventional fertilizer as the control group,spraying Chlorella vulgaris extract diluted 200 times on radish showed that the yield,chlorophyll content,quality and economic benefits of radish increased by 36.1%,chlorophyll content increased by 8.1%,single fruit weight increased by 21.4%,soluble total sugar increased by 36.9%,and output value per mu increased by 1243.2 yuan.The lower the basic value of radish indexes,the more obvious the improvement effect of Chlorella extract on radish indexes.