[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 present study was first carried out to investigate the adsorption potential of metal sludge (a waste product of electroplating industry) in removing vanadium from water. The adsorption capacity of metal sludge for vanadium was found 24.8 mg/g at 25 °C. The adsorption was studied as a function of contact time (0.5–10 h), concentration (1.5 × 10−4–9.5 × 10−4 M) and temperature (25 and 45 °C) by batch method. The adsorption has been found to be endothermic and data conform to Langmuir model. The analysis of kinetic data indicates that present adsorption system is a pseudo-first-order process and intraparticle diffusion controlled. After adsorption studies, the metal-laden sludge adsorbent was immobilized into the cement for its ultimate disposal. Physical properties such as initial and final setting time, compressive strength of cement stabilized wastes were tested to see the effect of metal-laden sludge in cement. The results of present study clearly reveal that metal sludge can be fruitfully employed in treating industrial effluents containing vanadium and further safely dispose of by immobilizing it into cement. The proposed technology provides a two-fold advantage of wastewater treatment and solid waste management.