[show abstract][hide abstract] ABSTRACT: The effect of chemical oxygen demand/sulfate (COD/SO(4)(2-)) ratio on fermentative hydrogen production using enriched mixed microflora has been studied. The chemostat system maintained with a substrate (glucose) concentration of 15 g COD L(-1) exhibited stable H(2) production at inlet sulfate concentrations of 0-20 g L(-1) during 282 days. The tested COD/SO(4)(2-) ratios ranged from 150 to 0.75 (with control) at pH 5.5 with hydraulic retention time (HRT) of 24, 12 and 6h. The hydrogen production at HRT 6h and pH 5.5 was not influenced by decreasing the COD/SO(4)(2-) ratio from 150 to 15 (with control) followed by noticeable increase at COD/SO(4)(2-) ratios of 5 and 3, but it was slightly decreased when the COD/SO(4)(2-) ratio further decreased to 1.5 and 0.75. These results indicate that high sulfate concentrations (up to 20,000 mg L(-1)) would not interfere with hydrogen production under the investigated experimental conditions. Maximum hydrogen production was 2.95, 4.60 and 9.40 L day(-1) with hydrogen yields of 2.0, 1.8 and 1.6 mol H(2) mol(-1) glucose at HRTs of 24, 12 and 6h, respectively. The volatile fatty acid (VFA) fraction produced during the reaction was in the order of butyrate>acetate>ethanol>propionate in all experiments. Fluorescence In Situ Hybridization (FISH) analysis indicated the presence of Clostridium spp., Clostridium butyricum, Clostridium perfringens and Ruminococcus flavefaciens as hydrogen producing bacteria (HPB) and absence of sulfate reducing bacteria (SRB) in our study.
Water Research 05/2009; 43(14):3525-33. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: The inhibition of methane production in the continuous anaerobic degradation process for the treatment of sewage sludge containing
sulfate was investigated. Also, the competition between sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB)
with COD/sulfate ratio was explained in terms of electron flow. The methane production rate was 0.07, 0.13, 0.24, 0.31 and
0.33 l-CH4 g-COD−1 when the initial COD/sulfate ratio was 3.3, 5.0, 6.7, 10 and 20, respectively. The numbers of SRB and MPB were counted after
the continuous reactor reached steady state and the two bacteria showed opposite growth behaviors with COD/sulfate ratio.
The inhibition by sulfate compounds was found to follow the uncompetitive model and inhibition constants were 24.57 and 87.99
−1 for SRB and MPB, respectively. These results can be useful data for the efficient treatment of sewage sludge in a continuous
anaerobic degradation process.
Korean Journal of Chemical Engineering 01/2009; 26(5):1319-1322. · 1.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: The characteristics of hydrogen production by four different hydrogen-producing bacteria (Clostridium beijerinckii, Rhodobacter sphaeroides, anaerobic bacteria isolated from sludge digester and Bacillus megaterium) were investigated quantitatively. The mathematical analysis using Gompertz equation showed that C. beijerinckii was the best hydrogen producer from glucose in terms of hydrogen-production potential and specific hydrogen-production rate. However, the bacteria required relatively long lag time at high-initial glucose concentration. The anaerobic bacteria showing the highest maximum hydrogen-production rate and relatively short lag time have a limit of low-hydrogen-production potential because they are mixed culture and produce some amount of methane gas. C. beijerinckii will be used in the actual system for hydrogen production from carbohydrate but the anaerobic bacteria may be a good choice for the production of hydrogen from wastewater containing innumerable compounds.
Journal of Industrial and Engineering Chemistry. 01/2008; 14(3):333-337.
[show abstract][hide abstract] ABSTRACT: A study on the effects of the COD/sulfate ratio on characteristics of sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB), using waste activated sludge (WAS), were performed in batch anaerobic digestion. The methane production rates of untreated and thermal treated WAS were 0.21–1.23, and 0.64–2.02 mL/day VSS, respectively. In the meantime, the hydrogen sulfide gas production rates of untreated and thermal treated WAS were 0–0.36, and 0–0.21 mL/day VSS, respectively. The methane production rate decreased as about 60% at the 11.6 of COD/sulfate ratio. In the case of high influent CODs, the methane production rate increased while the hydrogen sulfide rate decreased. It is thought that it is necessary to regulate the COD concentration in influent wastewaters in order to decrease the effects of SRB. The concentrations of various components such as sulfate should be properly controlled to reduce the methane production inhibition caused by the SRB in the anaerobic digestion using WAS.
Journal of Industrial and Engineering Chemistry. 01/2008; 14(5):693-697.
[show abstract][hide abstract] ABSTRACT: The possibility and characteristics of hydrogen production from waste activated sludge were investigated using separation membrane acid fermentation reactor (AR) and photosynthetic reactor (PR). The AR used submerged and external separation membranes and it was followed by the PR. The COD removal efficiencies in the AR with submerged and external separation membrane were about 65% and 40%, respectively. More VFA was produced in the AR with external separation membrane than AR with submerged separation membrane. Hydrogen was produced in the PR but not in the AR and hydrogen productions in the PR connected with submerged membrane AR and external membrane AR were about 50.1 and 160.5ml H2/g T-VFA, respectively.
International Journal of Hydrogen Energy - INT J HYDROGEN ENERG. 01/2007; 32(5):525-530.
[show abstract][hide abstract] ABSTRACT: The production and behavior of soluble microbial products (SMP) were investigated by employing a submerged MBR (membrane bio-reactor) process. The two types of bioreactors at different loading rates were conducted to understand the mechanism of bio-fouling and the behavior of SMP in a MBR process. Resultantly, the permeate flux of Run I (low loading rate) was maintained for 35days, while Run II (high loading rate) was maintained for 23 days. The filtration resistance values were similar because they were determined by the accumulated SMP concentration in the bioreactor. The production rate of SMP for Run II was measured as 0.0071 L/day, higher than for Run I (0.0056 L/day). After cleaning the membrane, the permeate flux showed on unstable and gradually decreased high SMP concentration in a short period. It is considered that the rate of accumulation of SMP relates to the biodegradability of utilization-associated products at different loading rate. From this research, we could determine that the volumetric loading rate affected to produce SMP, and SMP effected to not only membrane bio-fouling but also microbial activity.