Reasearch On The Cultivation Of Producing-oil Microalgae In Sludge Anaerobic Fermentation

Microalgae containing oil,as the third generation of biomass energy of alternatives to fossil fuels,its growth stage requires a large amount of source of carbon,nitrogen and phosphorus.The high cost of production on cultivation stage also limits the mass production of microalgae.Although the research on using wastewater to cultivate microalgae has gradually got the attention of the academic circles,but using the excess sludge anaerobic fermentation liquor from sewage plant to cultivate microalgae is little studied.This paper researches the feasibility of the cultivation of chlorella by fermentation liquor,through exploring several effective ways of pretreatment,releasing fully nutrient substances such as nitrogen and phosphorus and organics in sludge.Biomass in the microalgal,accumulation of oil content and the removal of pollutants also have important meaning.In this paper,the impacts of several key factors such as temperature,initial pH,light cycle on the chlorella's biomass and oil accumulation in fermentation liquor have been researched.In the same time,this paper explores in detail the changes on capacity of pollutants removal,in order to achieve the dual purpose of chlorella cultivation and removal of pollutants,realizing the resource utilization of excess sludge when minimizing the pressure from the by-product on the environment.(1)Through the comparison of several pretreatment methods conducive to promote the sludge disintegration and sludge anaerobic fermentation,exploring the reasonable mode,releasing the nitrogen,phosphorus and organic matter which are rich in sludge to the maximize and to research the best acidogenesis effect.In this experiment,alkali ultrasonic anaerobic fermentation made the pollutants in sludge release to the maximize and the acid production effect is best.The surplus sludge disposed by alkali ultrasonic pretreatment reached the optimum amount of dissolved nutrients on the fifth day of anaerobic fermentation,and acid production effect became the best.(2)Diluting the fermentation liquor into different multiples,excluding restriction of high COD and ammonia nitrogen on chlorella culture in the fermentation liquid,so the nutrients are utilized by chlorella to maximize.The microalgal biomass accumulation of polyculture mode is explored to be well.Chlorella has the characteristic of maintaining high pollutant removal capacity under heterotrophic mode.The experimental results showed that when fermentation liquor is diluted to 5 times of before and under mixotrophic condition,microalgal biomass reached the highest,and the utilization of organic matter,nitrogen and phosphorus became the best,realizing successfully the implementation of the cultivation of Chlorella that produces oil in sludge anaerobic fermentation liquor.(3)The paper studied the influence of multiple environmental factors on chlorella's removal of pollutants in the fermentation liquor.It found in the experiment of the effect of initial pH that the removal capacity of SCOD reached the maximum when initial pH=10,while Chlorella's removal rate of ammonia and TP reached the highest when pH=6,respectively,the rate is 94.70% and 91%.The experiment of the influence of light cycle shows that the removal rate of SCOD,ammonia nitrogen and TP is the maximum when the light cycle is 24:0,respectively,the rate is 82.37%,96.09% and 92.58%.And the experiment of the influence of temperature shows that chlorella's removal capacity on pollutants in the sludge anaerobic fermentation liquor reached the highest when T=25?.The removal rate of SCOD,ammonia nitrogen and TP is respectively 80.56%,94.12%,92.10%.(4)In order to obtain the chlorella biomass energy further,the experiment also studied the environmental factors' influence on chlorella biomass and lipid accumulation.The experimental results showed that,compared with other single factor experiment,in the three kinds of environmental condition of initial pH=6,light cycle is 12:12,the culture temperature is 25?,the biomass accumulation of Chlorella in the fermentation liquor reached the highest,the biomass can reach above 0.42g/L.When the initial pH=8,light cycle is 18:6,T=35?,algae's oil rate was the highest.While when the light cycle is 12:12,initial pH=6,T=25?,the relative total amount of grease in the culture system is the highest,the value is respectively 0.1068g/L,0.1075 g/L,0.1078g/L.