Research On The Culture And Harvesting Technology Of Microalgae Based On Organic Carbon

Energy shortage and environmental deterioration are two global problems for human beings to face,which has already have a certain impact on human beimg's daily lives.Seeking new and renewable energy and improving the environment quality are imminent.Microalgae are regarded as an ideal raw material for some renewable energy and has broad prospects for application.It can fix and absorb the carbon dioxide in the atmosphere efficiently and utilize wastewater for its growth.During this process,microalgae can accumulate biomass in cells and produce a series of high added value products.At the same time,lipid acid achieved can satisfy the demand for raw material to produce biodiesel which is considered as a new alternative energy sources of oil to ease the growing tension in the energy supply.However,the implementation for microalgae in large-scale is still facing lots of difficulties such as the operating complexity and high costs in both cultivation and harvesting,low recovery rate,low biomass productivity and low space utilization rate.These factors hindered the large scale commercialization of the microalgae thus optimization of cultivation and harvesting technology is a vital part in promoting the industrial development of microalgae while a breakthrough in this technology is an indispensable subject in amplifying the utility of microalgae in energy substitution and pollution control.This paper is aimed to optimize the cultivation and harvesting of microalgae and the effect of culture conditions and reactor system on the flocculation and attached cultivation were explored.The specific contents of the paper are shown as follows:(1)This paper presented an energy efficient harvesting strategy by adding carbon source to promote flocculation.The extracellular polymeric substance secreted by microalgae can cause flocculation between algal cells.EPS often divide into two major fractions:soluble EPS which are often dissolved in solution and bound EPS which usually is bound tightly and stably with the cell surface.Usually the bound EPS plays a pivotal role in flocculation.The maximum SSC of 2.1%was achieved with 71%in BRR under 250?mol m-2 s-1 light intensity,3 days mixing and 0.1 g/L glycine dose.On the other hand,the cost can be greatly cut down by using the suspended culture efficiently through medium recycling.(2)A culture-harvesting strategy of Botryococcus braunii was proposed in this part.The optimal organic carbon source was firstly selected by adding four kinds of different organic carbon sources,namely glucose,acetate,glycerin and glycine,into the medium respectively.Then a further study was conducted to explore the effect of culture periods,glycine dose,mixing time on EPS production,biomass recovery rate(BRR)and suspended solid concentration(SSC).The experiment results show that different composition in the EPS had varied effect on flocculation.The maximum SSC of 7.06%with BRR of 70.6%was achieved under 16days cultivation,5days mixing and 0.5 g/L dosage of glycine.(3)A drum type rotating algal biofilm reactor(RABR)was designed for attached cultivation and the design was further optimized.Cotton cloth performed best in cell adsorption thus was proved to be the best supporting material with a maximum adhesion biomass productivity of 7.4g/m2/day and adhesion rate of 34.7%.The optimized disk type RABR with a light dilution rate of 16.4 can achieve a higher maximum adhesion rate of 84.6%and a higher maximum adhesion biomass productivity of 27.5 g/m2/day using cotton cloth as supporting material and 1g/L glycine as carbon source.