Short-chain fatty acids resource recovery potential from algal sludge via anaerobic fermentation under various pH...

The harvesting of algal sludge from eutrophic lakes, including the large quantity of organic matters, has the potential to be used as valuable products through the process of resource recovery. This study investigates the fatty acid production potential from algal sludge via anaerobic fermentation under different pH values. The results indicated that the recovery of short-chain fatty acids (SCFAs) was the highest (3269.25 ± 32.89 mg·COD/L) at pH 11 after 7 days of fermentation. The SCFAs concentration at pH value 11 was 6.24, 1.27, 4.90, and 0.53 times higher compared with that at pH value 3, 5, 7, and 9, respectively. The SCFAs production was continually increased from day 1 to day 7 at pH value 7, 9, and 11. Much fewer middle- and long-chain fatty acids were produced compared with SCFAs. Gross. fatty acid production was the highest at pH 11. The concentrations of soluble protein and polysaccharide were the highest at pH 11, implying that the disruption of algal cells could have a high value at pH 11. The polysaccharide concentration was the lowest at pH 7. The fluorescence excitation-emission matrix profile implied that the disruption of algal cells was the greatest at pH 11. Methane production was greatest at pH 7 and 9. Overall, the results of this study revealed that a pH of 11 was optimal for the recovery of SCFAs from algal sludge due to the higher cell disruption, suitable ORP condition for SCFAs production and inhibition of methanogens.