Sulfate and dissolved sulfide variation under low COD/Sulfate ratio in Up-flow Anaerobic Sludge Blanket (UASB) treating domestic wastewater Ambiente ABSTRACT In this study, the dynamics of sulfate reduction and dissolved sulfide generation (S 2-, HS -, H 2 S aq ) in liquid phase was evaluated in an UASB reactor treating domestic wastewater with low COD/Sulfate content. The evaluation in the UASB reactor was performed at three sludge heights (0.25, 1.25, 2.25 taps) and effluent of the reactor.

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... lfate reduction was verified in the reactor, with an average reduction of 24 % throughout the experiment period. However, the dissolved sulfide concentration in the reactor was not higher than 5.0 mg S diss /L. The kinetic model of first order showed good fit to describe the sulfate reduction under different COD/sulfate ratio, with K 1 app between 2.94x10 -5 s -1 and 1.17x10 -5 s -1 with correlation coefficients for data over 91%. The maximum rate to sulfate reduction was 18.0 mg SO 4 2-/L.h -1 and small variation in COD/sulfate ratio promotes a significant change both in sulfate and sulfide concentrations.