Continuous Production of Volatile Fatty Acids (VFAs) from Swine Manure: Determination of Process Conditions, VFAs Composition Distribution and Fermentation Broth Availability Analysis

Abstract

For pollution control and waste utilization, a promising future direction is to obtain high-value carbon sources from organic waste. In this experiment, swine manure was efficiently converted into high concentration volatile fatty acids through continuous hydrolysis-acidification bioreactors. This study determined the process conditions, the composition distribution of volatile fatty acids and the availability of fermentation broth. The results showed that the reactor with a hydraulic retention time of 1.5 days had the optimal production performance of volatile fatty acids. The highest hydrolysis degree (62.2%) and acidification degree (42.5%) were realized in this reactor at the influent soluble chemical oxygen demand of 5460 mg/L. Furthermore, when the influent soluble chemical oxygen demand was 7660 mg/L, volatile fatty acids of 6065 mg-COD/L could be produced stably, and the proportion of volatile fatty acids in soluble chemical oxygen demand was the largest (75%). Additionally, the fermentation broth rich in volatile fatty acids could be applied to deep nitrogen and phosphorus removal. This work provides a productive approach to resource recovery from swine manure.