Production Of Volatile Fatty Acids From Algae Of Taihu Lake By Anaerobic Fermentation

In recent years, blue algae bloom every year in large scale because of the eutrophication of Taihu Lake. The bloomed algae have to be harvested to clear the lake water. However, it is a serious environmental problem to solve the havested algae. Considering the rich nutrition component such as protein in the algae, it is a promising method to use the algae as a useful resource to produce high value products by biotehnology. In the present research, algae were conversed into volatile fatty acids (VFAs) by using anaerobic fermentation technology. A series of process parameter were tested and optimized to improve VFAs production from algae. The main results are as follows:(1)Influence of pretreatment on VFAs production by algae from Taihu Lake. The effects of thermal-alkaline pretreatment method on the solubilization of organic matters and VFAs production were investigated. The results showed that thermal-alkaline pretreatment can improve the solubilization of organic matter from algae. After pretreatment the total solids (TS) and volitile solids (VS) content were increased. SCOD was 1.96 times higher than the untreated samples. Meantime, VFAs production by algae can reach up to 5.6 g/L, in which the acetic acid concentration was about 2.9 g/L. The VFAs production of pretreatment samples increased by 47.4% and 55.9% respectively than the untreated samples. The VFAs yield increased by 23.0% and acetic acid yield increased by 34.6%.(2)The influence of pH value on VFAs production from algae. The VFAs production, composition, acetic acid yield, VFAs yield, the degradation rate organic matters and biogas generation were valued. The results showed that the VFAs concentration can reach up to of 6.15 g/L when pH was 9, which was 1 and 3 times of the concentration of pH at 5 and 7; Meanwhile, VFAs yield and the degradation rate were also higher than that of lower pH condition. The acetic acid yield and VFAs yield were 0.274 gVFAs/gVS and 0.144 g acetate/gVS, respectively. The VS degradation rate was 51.91% and the degradation rates of proteins, carbohydrate and lipid can be as high as 53.2%, 30% and 40.6%, respectively. The biogas generation volume was the lowest level when pH at 9, suggesting that the alkaline condition can improve the VFAs production.(3)Influence of substrate concentration on VFAs prodution. The effects of different substrate concentrations on VFAs production, composition and VFAs yield were investigated. The results showed that the VFAs production increased gradually with the elevated substrates concentration. When VS was 6%, the VFAs concertration were 22.7 g/L and the acetic acid reached 12.5 g/L; Moreover, the substrate concentration influenced the VFAs composition from algae. High substrate concentration is in favor of acetic acid accumulation, with the increase of substrate concentration, the percentage of acetic acid increased from 49% (VS=1%) to 58% (VS=6%); When the VS is 4%, the VFAs yield reached to the highest level of 0.345 gVFAs/gVS and acetic acid yield reached 0.198 g acetic acid /gVS.