Enrichment of Electrogenic Bacteria from Activated Sludge and Soil Samples in Dual Chamber Microbial Fuel Cells

Abstract

Global energy demand is increasing rapidly with the development of science and technology. High operational cost and high rate of sludge generation in conventional waste water treatment plants demands a new alternate technology that could be operated efficiently at low cost and minimum sludge production. Microbial fuel cell could be alternative solution to this dilemma. Microbial fuel cells (MFCs) is a new approach, which electrochemically convert organic substrate containing chemical energy directly into electric current. The distinct advantage of this technology is to exploit the low-grade organic contents even waste water which otherwise not being used. The microbial power is being utilized in MFC to simultaneously generate electricity and treat waste water. Consequently, the high energy content of waste water is no more a waste, but seen as valuable energy reserve. In the current research study, double chamber microbial fuel cell has been constructed with two different proton conducting material. In one type of MFC agar salt bridge was used while in second type Nafion membrane 115 was used for proton conduction in between the two chambers. Activated sludge and submerged soils (S2, S3) were tested for electrochemical activity. In sucrose fed salt bridged MFC, maximum voltage and power output was 347Ω and 40.136μW, while after enrichment the voltage and power output was dropped to 74.9mV and 1.87μW across 3kΩ. When the same cell was operated with Potassium acetate maximum voltage and power produced were of 28.8mV and 0.27 μW, after enrichment the voltage and power dropped to about 24mV and 0.192 μW. The voltage and power output was increased after enrichment to about 332mV and 3674.3μW in membrane MFC at 50rpm.From the diversity analysis of soil, activated sludge and the biofilm formed on anodic surfaces, it has been analyzed that initial samples (Soil and Activated) contain diverse range of bacterial consortia while after enrichment stage 2 only selective bacterial classes left, α,β,γ- Proteobacteria accounts for approximately more than 90% relative abundance, which have major contribution in current generation. It has been observed that electrochemically active bacteria are better adopted in sucrose fed fuel cell. While membrane cell have greater power output than salt bridge MFC. It has been observed that resistance have a negative effect on current and power production while positive on voltage output