Enhanced syntrophic propionate degradation and methane production by granular activated carbon in AnSBR

Yiyang Fan,Jianzheng Li,Han Yan,Qiyi Chen,A Caggiano

doi:10.1051/e3sconf/202129303026

Yiyang Fan, Jianzheng Li + Show 3 more

Open Access

https://doi.org/10.1051/e3sconf/202129303026

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Abstract

Syntrophic degradation of propionate has been regarded as a limiting factor for methane formation in anaerobic digestion (AD) processes, due to its easier production but harder degradation than other volatile fatty acids. In the present study, 20 g/L granular activated carbon (GAC) was introduced into an anaerobic sequence batch reactor (AnSBR) and the enhancement of propionate degradation and methane production was evaluated with another AnSBR without GAC as a control. Inoculated with the same excess activated sludge, both AnSBRs were synchronously started up at 35 °C with the fed propionate increased gradually from the initial 340 mg/L to the final 1700 mg/L. The results showed that the introduction of GAC made the AnSBR get steady state 6 days earlier. With the fed propionate of about 1700 mg/L in the steady state, the average specific methane production and biomass was enhanced from 0.20 to 0.25 L/L·d, and 7.72 to7.96 g/L, respectively, by the introduced GAC. The results suggested that the GAC had functioned in stimulating microbial growth and enhancing direct interspecies electron transfer between hydrogen-producing acetogens and methanogens, which had resulted in the enhanced propionate degradation and methane production.

Highlights

It is known that propionate fermentation in anaerobic digestion (AD) processes is easier occurred with more energy production than other acidogenesis such as the fermentation of butyrate, acetate and ethanol as illustrated as Eq (1) to Eq (4), respectively [1]
The results indicated that the inoculated sludge in the anaerobic sequence batch reactor (AnSBR) without granular activated carbon (GAC) had been acclimatized since the 6th day
The results showed that a steady stage for specific methane production had been obtained in the AnSBR loaded with GAC since the 21st day

Summary

Introduction

It is known that propionate fermentation in anaerobic digestion (AD) processes is easier occurred with more energy production than other acidogenesis such as the fermentation of butyrate, acetate and ethanol as illustrated as Eq (1) to Eq (4), respectively [1]. C6H12O6 + 2H2 → 2CH3CH2COOH + 2H2O. △G0'= -254.0 kJ/mol (2) C6H12O6 + 2H2O → 2CH3COOH + 4H2 + 2CO2. Direct interspecies electron transfer (DIET) is presented as an alternative way to enhance the electrons transfer between acetogens and methanogens [6]. Conductive carbon materials, such as activated carbon, biochar, carbon cloth and carbon filter etc, have been introduced to enhance the methane production of AD [710]. As a common AD process, anaerobic sequence batch reactor (AnSBR) has been widely practiced in engineering, but little information about the effect of conductive carbon materials on the syntrophic degradation of propionate in AnSBR could be collected up to now

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