The functional certainty associated with secondary or tertiary process integration towards enhancing the viability of fermentative biohydrogen (H-2) production from wastewater stabilization was investigated with eleven diverse combinations of dark-fermentation (acidogenic, HA), photo-fermentation (H-P for H-2) and methanogenic (for CH4) processes. Based on the specificity of individual process, the biocatalyst and the feeding pH were selected and operated at uniform hydraulic retention time (48 h). Individually, H-P operation showed higher H-2 production (4.10 mmol H-2) and yield (16.02 mol H-2/kg CODR) than of H-A (3.38 mmol H-2, 11.33 mol H-2/kg CODR) which was found contrary to the observed substrate degradation. Two-stage process integration showed marked improvement in both H-2 production and substrate degradation. Integration of H-P with H-A showed maximum H-2 production while H-A with H-P evidenced maximum H-2 yield. Integration of methanogenic process with H-P documented both higher biogas production and yield. Maximum substrate degradation was evidenced with three stage sequential integration of dark-fermentation, methanogenic and photo-fermentation processes. Three-stage integration contributed for higher substrate degradation rather than energy generation, especially with HP as the terminal process. Organic flux, energy efficiency and carbon footprint analyses were used to comprehensively delineate the practical consideration of the integrated processes. (C) 2013 Elsevier Ltd. All rights reserved.