Microbial Electrolysis of Synthetic Acids for Biohydrogen Production: Influence of Biocatalyst Pretreatment and pH with the Function of Applied Potential

M Lenin Babu Pn Sarma

doi:10.4172/1948-5948.s6-003

Abstract

Bioelectrolysis of synthetic acids (acetate, butyrate and propionate) was evaluated in a single chamber Microbial Electrolysis Cell (MEC) to produce biohydrogen (H2). The influence of culture pretreatment (untreated and acid pretreated) and pH (6 and 7) conditions on electrolytic process were studied. MEC was operated at three optimized potentials viz., 0.2, 0.6 and 1.0 V along with control operated without any applied potential. Maximum Hydrogen Production Rate (HPR), Cumulative Hydrogen Production (CHP) and Specific Hydrogen Yield (SHY) were registered at 0.6 V followed by 1.0 and 0.2 V operations under all the experimental conditions studied. Culture pretreatment and pH variation showed influence on the MEC process. Pretreatment (PTr) operation at pH 7 showed good process performance than pH 6. MEC with untreated (UTr) at pH 6 and 7 showed lower performance compared to PTr operations. About 53% removal of synthetic acids was registered during the process which is a good sign for MEC as a wastewater treatment unit. Electrokinetic evaluation through Tafel slope showed that MEC operations with PTr and UTr at pH 6 recorded lower redox slopes and lower polarization resistance (Rp) at 0.2 V and 0.6 V whereas pH 7 recorded lower redox slopes and Rp at 0.6 V and 1.0 V.

Highlights

In recent times, microbial electrolysis is emerging as a promising technology for biohydrogen (H2) production when compared to the conventional dark fermentation process [1,2,3]
Pretreatment is one of the strategies which can be applied to parent inoculum to facilitate the selective enrichment of Acidogenic Bacteria (AB) which are capable of producing H2 as the end-product with simultaneous prevention of hydrogenotrophic methanogens [17]. pH of the system can bring about alterations in several primary physiological parameters of the biocatalyst like change in membrane potential and proton motive force. pH of the system can influence the substrate metabolism and release of metabolic byproducts [5]. pH range of 5.5 to 6 is ideal for effective H2 production due to the suppression of methanogens [16] and H2 evolution
The same trend was noticed with UTr biocatalyst at pH 7 but comparatively less H2 production was observed at 0.6 V (HPR, 2.210 mmol; Cumulative Hydrogen Production (CHP), 7.024 mmol) followed by 1.0 V (HPR, 2.029 mmol/h; CHP, 6.009 mmol) and 0.2 V

Summary

Introduction

Microbial electrolysis is emerging as a promising technology for biohydrogen (H2) production when compared to the conventional dark fermentation process [1,2,3]. Dark-fermentation is a potential process for the production of H2 using wastewater as substrate with simultaneous wastewater treatment [4,5]. Employing mixed culture is a better option for treatment of complex and nonsterile wastewater In this context, biocatalyst plays a significant role in influencing the overall process efficiency especially with wastewatermixed culture microenvironment. In a previous study [6], we employed an integration strategy where effluents from dark fermentation rich in VFA (acetate, butyrate and propionate) are used as substrate in MEC process. In the present study, an attempt was made to evaluate the influence of culture pretreatment and pH of the system on MEC process for H2 production using synthetic acids (acetate, butyrate and propionate) at a loading rate of 3000 mg/l concentration

Methods

Results

Conclusion