Papers by Keyword: Anaerobic Fermentation

Abstract: The anaerobic fermentation characteristic of rice straw pretreated by HCl was studied. The results showed that the test pH values of different pretreatment conditions mainly range from 5.09 to 7.52. The peak value of biogas production was attained of 2% HCl pretreatment on the 20^th day, which is 1 180 mL. The test daily methane content of different pretreatment conditions mainly ranges from 3.2% to 58.1%. However, the cumulative biogas production by using HCl pretreatment of rice straw during anaerobic fermentation is poor.

Abstract: A new-styled continuous stirred tank reactor (CSTR) seeded with activated sludge attached onto granular activated carbon (GAC) was developed for raised hydrogen production using diluted grenadine syrup. Emphasis was placed on the hydrogen producing performance and stability of the reactor. It was found that the temperature of (35 ± 1) °C, hydraulic retention time (HRT) of 4h, influent COD of 6000mg/L, the maximum hydrogen production was up 12.06L/d. In addition, though pH decreased to 3.42, the microbial growth still high and COD removal rate reached 50%, demonstrating that the reactor processed the ability of acid resistance.

Abstract: Great attention has been paid to the increasing amount of municipal sludge generated from wastewater treatment plants due to its potential risks to the surrounding environment. The municipal sludge, which mainly composed of polysaccharides, proteins as well as abundant groups of microorganisms, has been proved to be a promising biological material for hydrogen production by anaerobic fermentation. The tests systematically investigated the effects of initial pH on bio-hydrogen production from alkaline pretreated municipal sludge. The results showed that both hydrogenogen and methanogen were inhibited at the initial pH 2 to 4, which resulted in little hydrogen production. The methanogen inhibition was obvious by the rate of 94-98 % at the initial pH 5. The relatively high hydrogen production appeared at the initial pH 5 during the fermentation using the alkaline pretreated sludge at pH=12.0, and the corresponding pH at the end of fermentation was from 5.0 to 6.0, which was good for hydrogen production from saccharide. The hydrogenogen and methanogen could be promoted and the lag phase for hydrogen production could be shorten at the initial pH 6 to 10, however the corresponding hydrogen production was quite low. It also could be concluded that the alkaline pretreated sludge with initial pH 12.0 gave the highest hydrogen production, and the initial pH 12.0 for the alkaline pretreated sludge could inhibit methanogen growth and meanwhile maintain a high activity of the hydrogenogen.

Abstract: Anaerobic microorganisms involved in VFAs fermentation have inherent requirements for trace metals. It is inferred that excess sludge contains inadequate amounts of bioavailable trace metals for high-rate VFAs fermentation. The unavailability of these trace metals is probably the primary reason of poor yield without any other obvious reason. However, trace metal requirements in VFAs fermentation are not often reported in literature. Therefore, minimum requirements for trace metals including Zn, Co, Cu, Fe and Mn in VFAs fermentation from excess sludge were investigated. Firstly, the effect of each trace metal element on the VFAs production was investigated, respectively. And then, response surface methology was employed to optimize the requirement conditions of these five trace elements. The results showed that these five metal elements had the potential to enhance the production of VFAs, and the improved influences were as follows: Fe > Co > Mn > Cu > Zn. However, the production of VFAs decreased obviously with a further increase of each trace element. The optimal mixed conditions of these five trace elements were found to be 0.0982% Fe, 0.0047% Co, 0.0053% Zn, 0.0038% Cu and 0.0936% Mn. Under the optimal conditions, the concentration of VFAs reached 8410 mg/L, and increased by 2.5 times compare with the control. Finally, the consistent results between the prediction and the experiment indicated that the established polynomial model was feasible, and VFAs production could be described well by this model.

Abstract: A continuous stirred-tank reactor (CSTR) was used to produce biohydrogen gas from organic wastewater. The hydrogen producing reactor was operated under high organic loading rate of 21 kgCOD/m³·d, and molasses wastewater was used as substrate. Hydrogen production rate, pH value, sugar utilizing rate and fermentative products in effluent were investigated in continuous fermentation. When Organic Loading Rate was controlled at 21 kgCOD/m³·d, the average concentrations of acetic acid, ethanol, propionic acid, butyric acid and valeric acid in liquid fermentative products were 833, 748, 482, 484 and 256mg/L respectively. There is not any fermentation product playing dominant role absolutely in hydrogen production fermentation. The pH value in effluent was about 4.7~4.9, the average utilizing rate of sugar reached 92.1%, most of the sugar in molasses wastewater was utilized. The biogas production rate in hydrogen producing fermentation was from 21.2 to 27.1L/d, and the average biogas production rate was about 25.1L/d. The hydrogen content was about 37%.

Abstract: Proteins were the primary organics of excess sludge. Their properties were related to pH, which in turn affected the production of volatile fatty acids (VFAs). Excess sludge was firstly pretreated using the thermo-alkaline method, and the centrifuged supernatant was then taken as the substrate to investigate the effect of pH on the accumulation of VFAs from proteinaceous waste. The heating method was used to treat the inoculums in order to inhibit the generation of bio-methane during the whole anaerobic fermentation. The results showed that pH had an obvious influence on the bioconversion of proteins. Although the conversion ratios were higher than 50% when pH was controlled at 7.0-11.0, the protein biodegradation was sensitive to too low or too high pH values. Soluble proteins were precipitated to become insoluble proteins with the adjustment of pH from alkaline to acid except at pH 3.0. Acetic acid was the main accumulated end-product at most of pH settings, and at pH 10.0, its concentration reached the maximum of 5.7 g·L^-1 which was around 57.8% of total VFAs. At various pHs, it was soluble proteins that were responsible for VFAs production, while the precipitated proteins displayed a poor bio-degradability and disfavored the accumulation of VFAs during a 240 h of anaerobic fermentation.

Abstract: A batch test was carried out to investigate the effect of acid-producing fermentative characteristic of a new complex strains LZF-12 with high lignocellulose-degradation ability, which straw was the only carbon source in acidogenic phase. Simultaneity, the biogas-producing performance was also researched by shifting the liquid end products from acidongenic phase to methane phase, which fermentative substrate was the mixture of cow dung and kitchen waste. The results indicated that major fermentation products of acidogenic phase was acetic acid accounted for 70% of total volatile acid, which would be in favor of microorganisms growth of methanogenic phase. In two-phase anaerobic fermentation system, the straw degradation rate of composite strains LZF-12 reached the maximum at 72 hour, among which the degradation rate of cellulose, hemicellulose and lignin reached 55%, 67% and 13% respectively. The methane percentage of biogas-producing phase was more than 50% and 134.7mL/g VS of methane production rate was obtained.

Abstract: The basal fermentation time and hydraulic retention time were systemically investigated about anaerobic fermentation production hydrogen process by continuous flow which is based on activated sludge for a basic strain and simulating sucrose wastewater for a substrate in a continuous stirred tank reactor. The highest hydrogen production rate was got at the fermentation time of 15h for and 6h for hydraulic retention time. The optimum run acidity (pH = 4.5 5.0) was kept through their own system circulation to hold the system state of high-speed and continuous hydrogen production. The results can really laid the groundwork for the anaerobic fermentation production hydrogen process by continuous flow from contained sugar wastewater from the laboratory research towards industrialization.

Abstract: As lignocellulosic biomass, the cornstalk should be pretreated before anaerobic fermentation for hydrogen production. In this study, HCl, NaOH and enzyme were employed for cornstalk pretreatment and the products were used for anaerobic biohydrogen production. Hydrogen yield and hydrogen production rate were investigated to optimize cornstalk pretreatment method. In addition, the economic effect and energy consumption were also considered to evaluate the pretreatment methods. The optimum cornstalk pretreatment method was soaking in 2% NaOH at 50°C for 48h with a hydrogen yield of 55.0 ml/g-TS and a hydrogen production rate of 6.5 ml/h/g-VS in anaerobic hydrogen production.

Abstract: Anaerobic fermentation experiment was carried out with manure wastewater to produce biogas by using six parallel glass digesters system. Basic process conditions were chosen reference to previous studies. Based on the theory of methane fermentation, a prediction model was deduced, which can be used to forecast methane production according to a few of process parameters. In the experiment, two pivotal parameters involved in model were calculated, the sludge yield coefficient (Y_H) is 2.829×10^-2 and the sludge digestion coefficient (K_d) is 0.0215. The certain parameters, such as the oxygen equivalent (λ), the difference of COD between influent and effluent (D), the volume of fermentation broth (V), Y_H and K_d were substituted into prediction model, and then got the methanogenesis dynamics model in the process of methane fermentation by manure wastewater.