Effect of the environmental conditions on energy production in anaerobic processes

• Grant number: 08/00386-8
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: December 01, 2008
• End date: March 31, 2009
• Field of knowledge: Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
• Principal Investigator: Marcelo Zaiat
• Grantee: Marcelo Loureiro Garcia
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 05/51702-9 - Development of combined systems of treatment of residuary waters aimed at removal of pollutants and recovery of energy and of products from the carbon, nitrogen and sulphur cycles, AP.TEM

Abstract

The present work focuses on the study of syntrophic relationships in anaerobic systems. The goal is to link the energetic activity in terms of methane production with the microbial community which is present in the system at a certain environmental condition. One of the steps of anaerobic digestion, the methanogenesis, is extremely important in the anaerobic process. Methanogenesis is the final step of the anaerobic digestion through which the methane production occurs, and it can be the limiting step in many cases. Acetoclastic methanogens (i.e., acetate-consuming methanogens) produce the majority of the formed methane (70%) in typical anaerobic systems. However, acetate can be converted to other metabolites (or products) other than methane by bacteria. Therefore, secondary reactions are present in the anaerobic process depending on the environmental conditions that are found within the system. Even if archaea and bacteria populations are in equilibrium, the maximum methane yield is not reached given the media composition. Competition by acetate, one of the final fermentation process products and direct substrate of acetoclastic methanogenesis, can occur. In contrast, acetate could be utilized for hydrogen and carbon dioxide production, which would then be used by hydrogenotrophic methanogens for methane production. This syntrophic relationship is called mutualism. Even though the routes (pathways) for methane production are different, methane production occurs in both regardless. In this way, syntrophic relationships can directly affect the energetic activity of the anaerobic process. Observations on the microbial structure related to environmnetal conditions and methane production can reveal important evidences in the sense of improving the knowledge, stability and otimization of anaerobic processes.