Enhanced short-chain fatty acids production from waste activated sludge by alkaline-associated thermophilic Geobacillus Sp. G1 pretreatment

Thermophilic bacteria treatment, a typical efficient biological pretreatment method for complex organic waste degradation, was applied to hydrolyze waste activated sludge (WAS) to produce value-added products. An obvious enhancement in solubilization and acidification of WAS was obtained under alkaline-associated Geobacillus sp. G1 pretreatment. The maximal soluble carbohydrate and protein concentrations were 341 ± 15 and 1295 ± 45 mg COD/L, respectively, by alkaline-associated Geobacillus sp. G1 pretreatment at 60°C. The corresponding fluoresce in diacetate (FDA) hydrolase activity increased from 90 ± 5 to 206 ± 23 μg FDA/(mL h). The results of excitation emission matrix (EEM) fluorescence spectroscopy showed that WAS hydrolysis was enhanced by organics release through alkaline-associated Geobacillus sp. G1 pretreatment. The highest short-chain fatty acids (SCFAs) production was observed 3529 ± 150 mg COD/L, which was 1.5-fold and 1.4-fold of that only bysole alkaline (2330 ± 100 mg COD/L) or Geobacillus sp. G1 (2556 ± 95 mg COD/L) pretreatments. Expected SCFAs composition mainly consisted of acetic (HAc) and propionic (HPr), accounting for 63.5% of total SCFAs.