Bio-Hydrogen Ecological Systems And Processes With Brown Sugar For Substrate

Nowadays, the consumption of mineral energy reserves and sustaining environmental pollution has become an important problem to be resolved emergency. As a sustainable and clean energy source with minimal or zero use of hydrocarbons, hydrogen is a promising alternative to fossil fuel which caused more and more people's concern. The production technology and usage of hydrogen must bring significant environmental benefits, social benefits and economic benefits. The biological hydrogen production technology has taken more and more attention gradually by governments and scientists.Different concentrations of different substrates play an important role in hydrogen production efficiency of hydrogen production bacterium in anaerobic fermentation biological hydrogen production technology. The selection of the low cost substrate is the focus of research currently. Among all the usable substrates, sugars can produce hydrogen easily.This paper investigated the effects of different subtracts to fermentation bio-hydrogen production in batch culture, we also studied the set up and control of continuous stirred tank reactor (CSTR) which made brown sugar as subtract in continuous culture and constructed the bio-hydrogen system of artificial ecosystem anaerobic fermentation.The concentrations of monosaccharide were set at 5 g/L and 10 g/L respectively. The results showed that, the different monosaccharide (glucose, fructose, galactose and mannose) had little effects on the hydrogen production yield of Hydrogen Production Bacteria while the different concentration of substrates had grate effects on hydrogen production. The hydrogen production got the maximum of 4072 mL/L when took 10 g/L galactose and the minimum hydrogen production appeared when took 5 g/L fructose as substrate.For disaccharide, the hydrolysis of sucrose are glucose and fructose, which transformed to the middle production of glycolysis and took part in it. The hydrogen production yield (1.2 L/L) of hydrogen production bacteria when took glucose as substrate was less than 1.42 L/L when made sucrose as substrate.We also made 20 g/L brown sugar as substrate to investigate the fermentation biohydrogen production technology of hydrogen production bacteria and the fermentation time was 60 h. The results found that the hydrogen production fluctuated with the fermentation stage.Set up the CSTR with brown sugar which was suitable for biohydrogen production. At the beginning of the system, the COD concentration were set at 5000 mg/L.The biohydrogen production decreased. The hydrogen yield decreased at first and then increased while biomass decreased gradually with the operation. The increasing of liquid fermentation metabolism production in CSTR caused pH value gradually decreased. When the CSTR operated at 25th day, the concentration of acetic acid decreased and the concentration of ethanol increased, the reactor changed into the ethanol fermentation type. The hydrogen production yield increased and the biomass got the maximum which suggested that the ethanol fermentation-type was the best ferment and hydrogen production way. In the middle reaction the COD decreased to 3000 mg/L, total volatile fatty acids (VFAs) reduced when the CSTR operated 32 days, and pH value increased. The concentration of ethanol dropped while the propionic acid became the majority of the VFAs and the reactor turned into propionic acid fermentation type. The biomass and the hydrogen production activity of bacterium declined while hydrogen production declined with the operation. The COD dropped to 1000 mg/L (36 d to 40 d) and then increased to 5000 mg/L (41d to 45d), all parameters were tend to declining of this period. The rising of COD hadn't improved the biological activities and hydrogen production yield.The inoculated sludge used in the reactor was excess sludge taken from a second settling tank in a local wastewater treatment plant. It was indicated that the immobilized system was operated at the conditions of organic loading rate (OLR) of 8-32 kg/m3d, hydraulic retention time (HRT) of 6 h and temperature of (35±1)℃, when the pH value and oxidation-reduction potential (ORP) ranged from-335 and-422 respectively, liquid fermentation products were predominated by ethanol and acetate, with smaller quantities of propionate, butyrate and valerate. Stable ethanol-type fermentation was formed with the sum of ethanol and acetate concentration ratio of 72%to the total liquid products after 11 days operation. The biogas was free of methane throughout the study and the H2 content in biogas was estimated to be 50%. This fluctuation in the hydrogen yield was attributed to the formation of propionate. The rate of chemical oxygen demand (COD) removal reached 17%in the study. This CSTR system showed a promising efficient bioprocess for H2 production from high-strength organic wastewater.The ecological factors (such as pH, ORP) of activated sludge bio-hydrogen ecological system changed can trigger different fermentation type which made brown sugar as the substrate. When pH steady at 5.2-5.5, the end fermentation production were mainly butyrate and acetic acid and the concentration of ethanol and H2 yield were related lower, which performed for typical butyric acid type fermentation. The ecology niche of butyric acid fermented bacterium was suited with environment and became the major bacterium. When pH steady at 3.8-4.2 longer, the ethanol and acetic acid became the majority while hydrogen production yield got stable, fermentation type turned to ethanol type fermentation and lasted a long time, which showed the stability of ethanol fermentation.