Harnessing of biohydrogen from wastewater treatment using mixed fermentative consortia: Process evaluation towards optimization

Utilizing wastewater as a potential source for renewable energy generation through biological routes has instigated considerable interest recently due to its sustainable nature. An attempt was made in this communication to review and summarize the work carried out in our laboratory on dark fermentation process of biohydrogen (H-2) production utilizing wastewater as primary substrate under acidogenic mixed microenvironment towards optimization of dynamic process. Process was evaluated based on the nature and composition of wastewater, substrate loading rates, reactor configuration, operation mode, pH microenvironment and pretreatment procedures adopted for mixed anaerobic culture to selectively enrich acidogenic H-2 producing consortia. The fermentative conversion of the substrate to H-2 is possible by a series of complex biochemical reactions manifested by selective bacterial groups. In spite of striking advantages, the main challenge of fermentative H-2 production is that, relatively low energy from the organic source was obtained in the form of H-2. Further utilization of unutilized carbon sources present in wastewater for additional H-2 production will sustain the practical applicability of the process. In this direction, enhancing H-2 production by adapting various strategies, viz., self-immobilization of mixed consortia (onto mesoporous material and activated carbon), integration with terminal methanogenic and photo-biological processes and bioaugmentation with selectively enriched acidogenic consortia were discussed. Application of acidogenic microenvironment for in situ production of bioelectricity through wastewater treatment employing microbial fuel cell (MFC) was also presented. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.