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. 2019 Apr 13;24(8):1466.
doi: 10.3390/molecules24081466.

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

Long Lin  1 , Ehssan Hosseini Koupaie  2 , Armineh Azizi  3 , Amir Abbas Bazyar Lakeh  4 , Bipro R Dhar  5 , Hisham Hafez  6   7 , Elsayed Elbeshbishy  8
Affiliations

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

Long Lin et al. Molecules. .

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.

Keywords: acidogenic fermentation; hydrothermal treatment; microbial community analysis; particulate organics solubilization; source separated organics; volatile fatty acids.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
(a) The concentrations of suspended solids and (b) suspended solid reduction efficiency in raw, treated, and fermented SSO. (TSS: Total Suspended Solids, VSS: Volatile Suspended Solids)
Figure 2
Figure 2
Concentrations of (a) TCOD and SCOD, (b) total and soluble carbohydrates, and (c) total and soluble protein in raw, treated, and fermented SSO. (TCOD: Total Chemical Oxygen Demand, SCOD: Soluble Chemical Oxygen Demand, SSO: Source Separated Organics)
Figure 2
Figure 2
Concentrations of (a) TCOD and SCOD, (b) total and soluble carbohydrates, and (c) total and soluble protein in raw, treated, and fermented SSO. (TCOD: Total Chemical Oxygen Demand, SCOD: Soluble Chemical Oxygen Demand, SSO: Source Separated Organics)
Figure 3
Figure 3
(a) The concentration of VFA, (b) distribution of SCOD component in raw, treated, and fermented SSO samples, and (c) composition of VFA in fermented SSO samples. (SCOD: Soluble Chemical Oxygen Demand, VFA: Volatile Fatty Acids, SSO: Source Separated Organics)
Figure 4
Figure 4
Relative abundance of bacterial composition at (a) phylum level and (b) genus level in fermentation process in system-1 and system-2. Note: those genera accounted for <1% of the total bacterial population were grouped into “others”. Those unidentified genera were represented by the lowest taxonomic level assigned, such as family (f_) or order (o_) level.
Figure 5
Figure 5
Schematic diagram showing the experimental set-up.
See this image and copyright information in PMC

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