Excessive use of fossil fuels has led to a lot of environmental and economic problems. Therefore, using renewable resources as alternative for achieving energy is an interesting subject for both governments and researchers. Industrial wastewaters, due to high organic content, are suitable feedstocks to use as biomass for production of biofuels. The potential of sequence biohydrogen and biomethane production via dark fermentation and anaerobic digestion in 118-ml bottles as batch reactor was investigated. Anaerobic sludge from the north-east sewage treatment plant of Isfahan was used as inoculum for anaerobic digestion while it was shock-heat pretreated at 90 °C for 15 min to use as inoculum for dark fermentative biohydrogen production. In batch flasks, the effect of different concentration of initial COD (1.5, 3, 4, 6, 7, 11 and 15 g COD / L) on biohydrogen production was investigated at 37 °C and initial pH of 5.2. The headspace gas production was measured at specified intervals of 6, 12, 24, 48, 72 and 96 hr. Increasing COD up to 7 g COD per liter caused enhancement of hydrogen production, while it was declined at higher concentrations of initial COD. The best production efficiency of biohydrogen was obtained at an organic concentration of 7 g COD per liter equal to 42.03 ml hydrogen per gram initial COD. The maximum amount of produced biogas in these experiments was obtained at concentration of 4 g COD per liter, at which 140.9 ml methane was obtained in 66.3% methane content. However, the best quality in terms of the composition of methane (69.6% methane in biogas) was obtained at concentration of 3 g COD / L. The main purpose of this study was to produce biohydrogen via dark fermentation in a continuous biofilm fixed bed reactor using industrial wastewater as feedstock. A reactor with 1.5-L working volume was constructed using Kaldness-k3, pre-embedded into the two lattice screens (by height of 19 cm) within the column, as a packed bed for growth of biofilm. The reactor contain a recycle flow in which the effluent stream was recycled (120 ml/min) to the influent feed and create an up flow pattern through the biofilm. The temperature of 37 °C was set in the reactor using water-flow jacket. The reactor was inoculated with heat-shock pretreated anaerobic microbial mixture and operated in batch mode for startup in order to stabilize the appropriate biofilms. The influence of different hydraulic retention times (HRTs) on the performance of the reactor was studied by using different feed flow rates. At the startup period, the HRT was changed from 125 to 35 h and in the operating period HRTs from 22 to 1.5 were used (all the HRT periods are as follows: 125,52,35,22,15,12,10,7.5,4,3 and 1.5 h.). The performance of the reactor was studied by using the hydrogen production efficiency (total biogas production and its hydrogen composition), analysis of volatile fatty acids (VFAs) present in the effluent of the reactor, and COD reduction potential of the system. The gas production rate was enhanced by decreasing the HRT. The highest hydrogen production rate of 19.6 ml hydrogen per min was obtained at HRT of 1.5 h. However, the optimum HRT to produce higher hydrogen composition was obtained at HRT of 12 h with 41.2% hydrogen content. The reduction of COD content of wastewater was observed between 39% to 50% among all studied HRTs. The highest yield of hydrogen production equal to 136.9 ml per COD consumed was obtained at HRT of 7.5 h. The most important volatile fatty acid produced in the fermentation process of continuous hydrogen production was propionic acid (accounting for 70% of the total VFAs). Keywords: biohydrogen, biogas, bioreactor, biofilm, kaldness, dark fermentation, anaerobic digestion