Comparison of Two Process Schemes Combining Hydrothermal Treatment and Acidogenic Fermentation of Source-Separated Organics

Abstract

This study compares the effects of pre- and post-hydrothermal treatment of source- separated organics (SSO) on solubilization of particulate organics and acidogenic fermentation for volatile fatty acids (VFAs) production. The overall COD solubilization and solids removal efficiencies from both schemes were comparable. However, the pre-hydrolysis of SSO followed by acidogenic fermentation resulted in a relatively higher VFA yield of 433 mg/g VSS, which was 18% higher than that of a process scheme with a post-hydrolysis of dewatered solids from the fermentation process. Regarding the composition of VFA, the dominance of acetate and butyrate was comparable in both process schemes, while propionate concentration considerably increased in the process with pre-hydrolysis of SSO. The microbial community results showed that the relative abundance of Firmicutes increased substantially in the fermentation of pretreated SSO, indicating that there might be different metabolic pathways for production of VFAs in fermentation process operated with pre-treated SSO. The possible reason might be that the abundance of soluble organic matters due to pre-hydrolysis might stimulate the growth of more kinetically efficient fermentative bacteria as indicated by the increase in Firmicutes percentage.

Impact of Hydrothermal Pretreatment Parameters on Mesophilic and Thermophilic Fermentation and Anaerobic Digestion of Municipal Sludge

“…Temperature has been proven to play a crucial role in sludge disintegration during HTP [20,22,[27][28][29]. It was reported that temperatures above 100 • C improve the sludge disintegration drastically, whereas going beyond 200-220 • C produces refractory compounds such as melanoidins [30][31][32].…”

“…BMP tests are usually conducted to understand the methane production potential, the methane production rate, and biodegradability [21][22][23]. In the current study, we have used the same procedure and conditions for the BMP test described previously [24].…”

Biogas and Methane Potential of Pre-Thermally Disintegrated Bio-Waste

“…Regardless of the disintegration method used, the primary effect of the treatment is the liquefaction of the substrate's solid fraction. It is assumed that the fragmentation of sludge or solid waste will increase the availability of organic substances for micro-organisms; i.e., the potential biodegradability [12]. However, the existing literature does not confirm this fact unequivocally.…”