Surfactant rhamnolipid promotes anaerobic codigestion of excess sludge and plant waste

In order to solve the bottleneck of low methane production in anaerobic codigestion of excess sludge (ES) and plant waste (PW), a new strategy of enhancing hydrolysis and acidification by rhamnolipid (RL) was proposed under thermophilic condition. The results showed that the optimal dosage of RL was 50 g/kg total suspended solids, and the maximum yield of methane was 198.5 mL/g volatile suspended solids (VSS), which was 2.3 times of that in the control. RL promoted the dissolution of organic matter in the codigestion process of ES and PW, and the higher the dosage of RL, the higher the concentration of soluble chemical oxygen demand (SCOD) in the fermentation broth. When RL was 100 g/kg, the maximum content of SCOD in fermentation broth was 2,451 mg/L, and the contents of soluble protein and polysaccharide were 593 mg/L and 419 mg/L on 10 d, respectively, which were significantly higher than other groups. In addition, the yield of VFA in RL group was also significantly increased, and acetate and propionate were the main components of VFAs. This research work provides data support for the resource utilization of ES and PW, and expands the application field of RL.