The Study Of Lipid Accumulation And Cultivation Of Microalgae Using Wasterwater And Flue Gas

Microalgae own the advantage of fast growing speed and high energy conversionefficiency. Carbon and water are the main factors that restrict the production ofmicroalgae biodiesel. Some algae can remove carbon, nitrogen, phosphorus waste inmunicipal wastewater and simmilate CO2, NOxin flue gas. Combining lipidaccumulation with treatment of wastewater and flue gas can generate greatenvironmental and economic benefits. In this study, artificial wastewater and municipalwastewater were used, the growth characteristics, lipid accumulation of Chlorellasorokiniana and the ability to remove environmental pollutants in differentenvironmental conditions were investigated in both artificial wastewater and municipalwastewater. Effects of nitric oxide salts (sodium nitrite and sodium nitrate), sulfur oxidesalts (sodium sulphite and sodium sulfate)on the growth and lipid accumulation ofChlorella sorokiniana and other two microalgae strain (Chlorella sp and Scenedesmusobliquus) which screened by our previous research work were studied. The ability ofwaste water treatment and lipid accumulation of Chlorella sp and Scenedesmus obliquushave been also studied previously.The effects of sodium nitrite, sodium nitrate, sodiumbisulfite, sodium sulfate on the growth and lipid accumulation of three microalgae werestudied. The growth characteristics, lipid content and carbon absorption wereinvestigated under different CO2concentrations. Combined treatment system ofwastewater and flue gas was established. Growth characteristics and lipid content ofthree microalgae and the ability to remove environmental pollutants under this systemwere examined.Different illumination period and initial pH, different amount of algae and glucose,and artificial wastewater were used to analysis the impact on growth and lipid content ofChlorella sorokiniana. The results showed that culture conditions significantly affectedthe growth and fat accumulation of Chlorella sorokiniana,18hours of illumination time,initial pH7.5,20%algae and5g/L glucose addition,were optimal conditions forbiomass accumulation,24hours of illumination time, initial pH7.5,15%algae and1g/Lglucose addition were optimal conditions for lipid accumulation. Culture conditionssignificantly impacted the removal of environmental pollutants. Initial pH significantlyimpacted the removal of COD, TP, illumination time had the minimal impact for COD,TP removal, environmental conditions significantly effected the removal of TN, pH hadthe maximum influence on the removal of environmental pollutants. Unsterilizedmunicipal wastewater was more suitable for the growth of Chlorella sorokiniana, fatcontent and the ability to remove environmental pollutants are higher than the sterilewastewater.Three microalgae were able to tolerate high concentration of NaNO2, microalgae firstly use nitrate when nitrate and nitrite exist simultaneously, Chlorella sorokinianaowned the highest fat content when the addition of NaNO2is10mmol/L, Chlorellasp.and Scenedesmus obliquus possessed the highest fat content when the addition ofNaNO2is15mmol/L. When NaNO2as the sole nitrogen source, NaNO2addition hadno significant effect on the growth of Chlorella sorokiniana, But inhibited the growth ofChlorella sp. and Scenedesmus obliquus, Three microalgae were all can use nitrite, butthe growth characteristics were poorer than control group. Increasing the content ofnitrate promoted the fat accumulation of Chlorella sorokiniana, Chlorella sp. had thehighest fat content when adding1.6mmol/LNaNO2, for Scenedesmus obliquus，controlgroup had the highest fat content. High NaNO3inhibited the growth of three microalgae.Low concentration of NaHSO3can promote the growth of three microalgae, Chlorellasorokiniana and Chlorella sp. had considerable tolerance for NaHSO3, Scenedesmusobliquus had slightly higher tolerance for NaHSO3, NaHSO3addition can promote lipidaccumulation of Chlorella sorokiniana, concentration of2mmol/L NaHSO3Chlorellasp.had the highest lipid content. Scenedesmus obliquus had the highest lipid contentwhen NaHSO3concentration is3mmol/L.Addition of Na2SO4had no significant effecton the growth of Chlorella sp. and Scenedesmus obliquus, But had an impact on thegrowth of Chlorella sorokiniana, addition of Na2SO4promoted the fat accumulation ofthree microalgae.Three microalgae can tolerate high concentration of CO2, and the amount of CO2absorbed by three microalgae nearly5percent, CO2can promote fat accumulation ofthree microalgae, and higher the concentration the promotion was more obvious.Wastewater and flue gas joint system was established according to the absorption ofCO2of three microalgae, three microalgae grow well in this system, and immediatelyenter logarithmic growth phase after vaccination，however, the growth period becomeshorter and pH decreased sharply, lipid content was significantly low under thiscombined system.