Startup And Operation Of New Hybrid Anaerobic Baffled Biological Hydrogen Production Reactor

The exploitation and application of clean energy is the trend of the times, because energy shortage and environmental pollution problem are increasingly serious with the development of the society. The hydrogen energy has been widely aroused people’s attention as one of the desired clean energy. Water is the only product of hydrogen combustion, and there are renewable, high calorific value, transported of hydrogen energy. The organic wastewater could be used as a substrate for anaerobic fermentation bio-hydrogen production that wastewater treatment and clean energy production are running at the same time.A study of biological hydrogen production was performed in a hybird anaerobic baffle reactor (HABR). Brown granulated sugar as substrate and mixed culture of aerobic sludge as inoculation sludge, the start up and operation of biological hydrogen production HABR reactor and the way of ethanol type fermentation forming were discussed. The result shows that the integration of mixed culture and biofilm HABR as a new type for ethanol fermentation biological hydrogen production system is feasible. Under the operational conditions of temperature of35℃, hydraulic retention time (HRT) of12h, initial startup OLR of2.5kg/m3·d, in the way of improving OLR (4.5kg/m3·d) by stages, ethanol fermentation type is formed among5compartments within the20d after domestication and run for15d stably that means the HABR bio-hydrogen production started up successly. And hydrogen production capacity of each compartment is different obviously, because wastewater of each compartment is different equivalent to the inoculants of each compartment startup under different conditions (OLR, pH, etc.). So each compartment shows different hydrogen production although ethanol type fermentation system formed. The result of operation under OLR at6.5kg/m3·d and8.5kg/m3·d shows that the optimum operating efficiency including average COD removal rate of43.34%, average hydrogen production ability of14.91L/d, the average energy of3340.62KJ/d occurred at OLR at6.5kg/m3·d. Linear regression result shows that H2production rate (y) and ethanol production rate (x) was proportionately correlated and can be expressed as y (H2)=0.31x (ethanol)-0.1335(R2=0.9235) under the condition of different OLR. In addition, the higher OLR and lower pH value is a limiting factor for the reactor when OLR is about8.5kg/m3·d and in order to keep sustainable running adding adaptive salt to neutralize excessive organic acid is considered.Hydraulic retention time (HRT) is important for HABR hydrogen production system, because mixing device structure is not set, the agitation of wastewater and microbes depend on the impact of the rising wastewater and sludge sedimentation entirely. The five HRTs were examined, ranging from36,24,16,12, to8h. The result shows that hydrogen production rate increased with HRT reduced from36h to12h and reduced when HRT is8h, so the best operative HRT was12h and then average hydrogen production rate was13.86mmol/h-L and average energy production quantity was11.11k kJ/h-L from ethanol-type fermentation in the pH range of4.22～4.47. During the whole operation process, ethanol and acetic acid are main predominant metabolites and the ratio of ethanol and acetic acid from the first to fifth compartment were1.90,1.94,1.80,1.77,1.91and the higher the better. Linear regression showed that hydrogen production rate and ethanol production rate were proportionately correlated at all HRTs which could be expressed as y (H2)=1.2883x (ethanol)+7.1739(R2=0.8566)In addition, the continuous flow stirred tank reactor (CSTR) was the most used in the study of biological hydrogen production. The operation effect of HABR and CSTR hydrogen production system were compared discussed. For the part of startup, the time of CSTR reactor was shorter than HABR due to the different structure and volume and CSTR system took30d for startup successly and running stably and HABR needed43d. So, it is said that the type of reactor isn’t the decisive factor for forming of fermentation type but could influence the formed process of fermentation type. The two types of reactor operation effect under different COD (4000,6000,8000mg/L) were discussed, the result shows that the hydrogen production efficiency, energy production efficiency and COD removal rate of HABR are increased with the increase of COD, and reached17.54mmol/h-L,45.13kJ/h-L,42.87%respectively at COD=8000mg/L. The optimum of hydrogen production efficiency, energy production efficiency and COD removal rate arrived13.26mmol/h-L,33.00kJ/h-L,26.47%respectively at COD=6000mg/L of CSTR. Under the condition of low organic loading hydrogen content of CSTR hydrogen production system was higher, and under the condition of high organic load HABR hydrogen production system become advantage.