Enhancing swine wastewater hydrolysis with thermophilic bacteria and assisted pretreatments.

Slow degradation rate of swine wastewater, which is mainly caused by particulate and refractory organic matters, is the main drawback of anaerobic digestion. Therefore, it is necessary to improve the hydrolysis of swine wastewater. In this study, different pretreatments were used to hydrolyze swine wastewater, including thermophilic bacteria (TB), alkali, acid, ultrasound (UL), and ultrasonic-combined thermophilic bacteria (UL-TB) pretreatment. The hydrolysis effect was investigated by analyzing the changes of pretreated soluble chemical oxygen demand (SCOD), soluble protein, and carbohydrate. The experimental results showed that effect of different pretreatments on swine wastewater hydrolysis had the following order: TB = alkali>UL-TB > UL>acid. Alkali pretreatment was effective for the release of protein from swine wastewater, and TB pretreatment was advantageous for carbohydrate release during hydrolysis. The results could provide valuable information for the disposition of swine wastewater as well as the application of TB-related pretreatments. PRACTITIONER POINTS: TB and alkali pretreatment exhibited the highest hydrolysis ability. The release of carbohydrate by TB was higher than other pretreatments. Ultrasonic assistance generated inhibition on the hydrolysis of TB.