Study On Environmental Optimization Of High-efficiency Cultivation Of Chlorella In Domestic Sewage

Using domestic sewage to cultivate microalgae can not only purify rural domestic sewage and improve the ecological environment,but also obtain abundant energy microalgae,which promotes the industrialization of microalgae en ergy.However,in the northwest of China,due to the limitation of ambient temperature in winter,it is difficult to cultivate microalgae on a large scale outdoors,which limits the popularization and application of large-scale cultivation of microalgae in village sewage.Therefore,in view of the climatic characteristics of the northwest inland region of China,this paper develops a solar energy thermostatic cultivation system for microalgae purification of domestic sewage by utilizing the characteristics that the economic heat collection temperature of solar collector matches the optimum growth temperature of microalgae,and designing a simulator for solar energy thermostatic cultivation of microalgae to purify domestic sewage system.Through experimental study,the coupling relationship between microalgae production and cultivation conditions is analyzed,and the performance and optimal environmental conditions of solar energy thermostatic cultivation of microalgae to purify domestic sewage system are mastered,which can provide theoretical guidance for further purification of rural domestic sewage in Northwest inland areas of China.The main conclusions are as follows:(1)Single factor experimental analysis shows that the environmental factors(initial sewage concentration,environmental temperature,light intensity and light time)had significant effects on the growth of chlorella.The appropriate level of environmental factors can not only weaken the growth stagnation at the early stage of culture,but also increase the growth rate and dry weight of chlorella.The dominant level range of initial sewage concentration is 2-6 times dilution of domestic sewage,and the optimum level is 2 times dilution;the dominant level range of environmental temperature is 25-35?,and the optimum level is 30?;the dominant level range of illumination intensity is 10000-14000 Lux,and the optimum level is 12 000Lux;the dominant level range of illumination time is 16-24 h,and the optimum level is 20 h.It was found that the optimum environmental temperature,light intensity and light time for Chlorella to grow in sewage and chemical medium were different.(2)The results of orthogonal experiments show that different combinations of environmental factors had different effects on the growth of chlorella.Initial sewage concentration and illumination time are important environmental factors affecting the growth of chlorella.Environmental temperature and illumination intensity have a relatively small impact on the culture of chlorella,and the degree of influence is arranged as follows: initial sewage concentration > illumination time > environmental temperature > illumination intensity.The theoretical optimum combination of environmental factors for culturing Chlorella in villag e sewage is to dilute domestic sewage twice,illumination time is 16 h,ambient temperature is 30 ?,illumination intensity is 10000 Lux.It was found that the change of dry weight of Chlorella varied with the growth rate,and the effect of the two changes wa s the same.(3)The comparative experimental analysis shows that the theoretical optimum combination of environmental factors obtained by orthogonal experiment has a stable promoting effect on the culture of Chlorella in village sewage.Compared with the optimal combination of factors obtained by single factor experime nt and the promotion effect under natural environment conditions,the theoretical optimal combination of environmental factors has the highest promotion efficiency and the best effect on the cultivation of Chlorella in village sewage.It is concluded that the optimal culture environment for Chlorella in village sewage is not simply the superposition of the optimal levels of environmental factors,but the interaction and coupling between environmental factors.Therefore,the optimum environmental conditions for culturing Chlorella in village sewage are as follows: diluting domestic sewage twice,setting illumination time to 16 h,ambient temperature to 30 ?,and illumination intensity to 10000 Lux.