Effect of COD/SO(4)(2-) ratio and sulfide on thermophilic (55 degrees C) sulfate reduction during the acidification of sucrose at pH 6.
This study investigated the effect of the COD/SO(4)(2-) ratio (4 and 1) and the sulfide concentration on the performance of thermophilic (55 degrees C) acidifying (pH 6) upflow anaerobic sludge bed reactors fed with sucrose at an organic loading rate of 4.5 g COD l(reactor)(-1)day(-1). Sulfate reduction efficiencies amounted to 65% and 25-35% for the COD/SO(4)(2-) ratios of 4 and 1, respectively. Acidification was complete at all the tested conditions and the electron flow was similar at the two COD/SO(4)(2-) ratios applied. The stepwise decrease of the sulfide concentrations in the reactors with a COD/SO(4)(2-) ratio of 1 by N(2) stripping caused an immediate stepwise increase in the sulfate reduction efficiencies, indicating a reversible inhibition by sulfide. The degree of reversibility was, however, affected by the growth conditions of the sludge. Acidifying sludge pre-grown at pH 6, at a COD/SO(4)(2-) ratio of 9 and exposed for 150 days to 115 mg l(-1) sulfide, showed a slower recovery from the sulfide inhibition than a freshly harvested sludge from a full scale treatment plant (pH 7 and COD/SO(4)(2-)=9.5) exposed for a 70 days to 200 mg l(-1) sulfide. In the latter case, the decrease of the sulfide concentration from 200 to 45 mg l(-1) (35 mg l(-1) undissociated sulfide) by N(2) stripping caused an immediate increase of the sulfate reduction efficiency from 35% to 96%.
Lopes
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Sub-department of Environmental Technology, Wageningen University Biotechnion-Bomenweg 2, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
Wang
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Capela
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Lens
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D000693:Anaerobiosis; D019149:Bioreactors; D006862:Hydrogen Sulfide / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D012722:Sewage / Q000737:chemistry*; D013395:Sucrose / Q000737:chemistry / Q000378:metabolism*; D013431:Sulfates / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
D012722:Sewage; D013431:Sulfates; D013395:Sucrose; D009584:Nitrogen; D010100:Oxygen; D006862:Hydrogen Sulfide