BACKGROUND: A series of kinetic experiments for a sulfate reducing process was carried out in a batch laboratory reactor that allowed simplification of a model initially proposed for this system enabling establishment of the kinetic parameters. RESULTS: It was found that an incomplete oxidation of lactate is the most significant bio-reaction occurring in the reactor; this fact led to model simplifications that allowed determination of the kinetic parameters. Sulfide and pH inhibition can be described using one inhibition term within the model equation, given the fact that sulfide inhibition is not present in the system. Kinetic parameters were obtained, yielding a maximum specific rate (mu(max)/Y) of 2.17 +/- 0.08 mg sulfate mg(-1) VSS min(-1). A zero-order kinetics with respect to sulfate and a Monod affinity constant of 142.7 +/- 64.9 mg L-1 for the lactate were found. CONCLUSIONS: The final model for the process can be described by a single Monod term involving the lactate. This model resulted from the lack of sulfide inhibition in the system and the predominance of the partial lactate oxidation to acetate reaction over the complete lactate and acetate oxidation. (C) 2010 Society of Chemical Industry