In the process for the production of acetic acid by carbonylation of methanol and/or a reactive derivative thereof the water concentration in the liquid reaction composition is maintained at a steady-state concentration by at least one process step selected from the group consisting of (i) recovering and disposing of water from at least part of the overhead process stream from the light ends column and (ii) replacing at least a portion of the methanol feed with a component selected from the group consisting of methyl acetate, dimethyl ether, acetic anhydride and mixtures thereof. The recovered aqueous effluent from this and other processes may be purified of carboxylic acid by reactive distillation with at least one C1 to C3 alcohol. <IMAGE>
