Oil-rich Microalgae Cultivation In Wastewater From The Fermentation Eflfuent In Ribolfavin (B2) Manufacturing And Microalgae Harvest By Membranes

With the rapid development of world economy, biodiesel, as thealternative energy of petroleum diesel, caught the attention. Among manyraw materials of biodiesel, the Alga, due to its advantages of highbiomass, short growth cycle, easy to train, and the high lipid, becomes anideal material for biodiesel, and it has a broad prospect of development.Meanwhile， using waste water to plant oil-rich microalgae, not onlyreduces the cost of microalgae production, but also restores waterpollution, so it becomes the feasible solution to the inadequate supply ofbiodiesel raw materials and the problems of raw material prices.The wastewater from the fermentation effluent in Riboflavin (B2)manufacturing contains varieties of nutrients which can be used formicroalgae cultivation. In this work, the acclimation of ChlorellaPyrenoidosa in diluted wastewater was studied to produce biomass andremove Chemical Oxygen Demand (COD), ammonia and phosphorous.Controlle the culture conditions, to improve the oil content of algae cells；Evaluate the impact of membrane material on the ultrafiltrationperformance of microalgae medium； Deal with the filtration andconcentration of algae from a diluted culture medium using sixcommercial microfiltration membranes and ultrafiltration membranes.The main experimental results are as follows:1、the optimal conditions (the volume ratio of wastewater, lightintensity, culture temperature, CO2concentration in feeding gas) whichcould influence the wastewater treatment efficiency were0.05,5000Lux,28℃，5%，respectively. Under these conditions, the removal efficiency ofCOD reached up to89.2%, while the total nitrogen and total phosphorousdecreased by64.52%and82.20%, respectively. With the secondtreatment, COD content of the wastewater decreased to below100mg/L,which met the need of the industrial sewage discharge standard of grade-1and could be discharged directly or conveyed to next step for further treatment. In addition,1.25g/L of the biomass and38.27%(dry basis,w%) of lipid content were reached. Therefore, microalgae cultivation inthis industrial wastewater with high salinity demonstrated the possibilityof using microalgae to remove nutrients and produce biofuel.2、It was observed that the permeate flux increased with increasingtransmembrane pressure for three different membranes：Polysulphone (PS,MWCO=100,000), Fluoro polymer (PVDF, MWCO=100,000) andRegenerated cellulose acetate (RCA, MWCO=10,000). Moreover,permeate flux increased as the cross-flow velocity increased. The fluoropolymer membrane showed the most significant improvement of fluxwith increase in cross-flow velocity, which may suggest that the foulingmaterials attached more weakly on the membrane surface of thismembrane than on the other membranes. Hydrophilic regeneratedcellulose acetate membrane had a much lower fouling tendency thanhydrophobic polysulphone and fluoro polymer membranes. To maximizeflux recovery for the algae-fouled membranes, NaOH, NaOCl andUltrasil10were applied as cleaning agents. Ultrasil10with concentrationof0.5%was more effective than other agents for membrane cleaning.3、 The effects of the operating conditions, e.g. feed solutiontemperature, transmembrane pressure (TMP), VCF (volumeconcentration factor) and cross-flow velocity on the filtrationperformance were investigated. The results showed that permeate fluxesincreased with the increase in feed solution temperature. The permeatefluxes increased slowly with increasing TMP up to a certain limit, andafter that the fluxes were stable or even decreased. The higher cross-flowvelocity can significantly decrease particle accumulating on the surface ofmembrane, and thus leading to higher permeate flux. AlthoughETNA10PP exhibited much less fouling than other membranes, thepermeate flux of this membrane was not higher than other membranesmost likely due to the fact that this membrane is the tightest membranewith MWCO10,000. The interesting finding of our work is that we do not see clear advantage of microfiltration over ultrafiltration for concentrationof algae.