Apparatus for conditioning an aqueous liquid, including: at least one device (7;7';31) for increasing a level of CO 2 in the liquid; a membrane filtration device (16;16';34); and a processing section (21;21';44), downstream of the at least one device (7;7';31) for increasing the level of CO 2 in the liquid, the processing section (21;21';44) including at least one liquid treatment device (23;23';46) for dissolving at least one mineral contributing to carbonate hardness into at least some of the liquid passing through the section, wherein the processing section (21;21';44) includes a sub-section (25;25';49) accommodating the at least one mineral to be dissolved, defines a flow path bypassing the sub-section (25;25';49) and includes a mixing location (27;27';48) for blending at an adjustable ratio a fraction of liquid led through the sub-section (25;25';49) with a further fraction of liquid led along the flow path bypassing the sub-section (25;25';49), the fraction and the further fraction being fractions of the liquid of which the level of CO 2 has been increased prior to separating it into fractions, characterised in that the membrane filtration device (16;16';34) is interposed between the at least one device (7;7';31) for increasing a level of CO 2 in the liquid and the processing section, and in that the at least one device (7;7';31) for increasing a level of CO 2 in the liquid is arranged to increase the level to an adjustable value. at least one device (7;7';31) for increasing a level of CO 2 in the liquid; a membrane filtration device (16;16';34); and a processing section (21;21';44), downstream of the at least one device (7;7';31) for increasing the level of CO 2 in the liquid, the processing section (21;21';44) including at least one liquid treatment device (23;23';46) for dissolving at least one mineral contributing to carbonate hardness into at least some of the liquid passing through the section, wherein the processing section (21;21';44) includes a sub-section (25;25';49) accommodating the at least one mineral to be dissolved, defines a flow path bypassing the sub-section (25;25';49) and includes a mixing location (27;27';48) for blending at an adjustable ratio a fraction of liquid led through the sub-section (25;25';49) with a further fraction of liquid led along the flow path bypassing the sub-section (25;25';49), the fraction and the further fraction being fractions of the liquid of which the level of CO 2 has been increased prior to separating it into fractions, characterised in that the membrane filtration device (16;16';34) is interposed between the at least one device (7;7';31) for increasing a level of CO 2 in the liquid and the processing section, and in that the at least one device (7;7';31) for increasing a level of CO 2 in the liquid is arranged to increase the level to an adjustable value. the processing section (21;21';44) including at least one liquid treatment device (23;23';46) for dissolving at least one mineral contributing to carbonate hardness into at least some of the liquid passing through the section, wherein the processing section (21;21';44) includes a sub-section (25;25';49) accommodating the at least one mineral to be dissolved, defines a flow path bypassing the sub-section (25;25';49) and includes a mixing location (27;27';48) for blending at an adjustable ratio a fraction of liquid led through the sub-section (25;25';49) with a further fraction of liquid led along the flow path bypassing the sub-section (25;25';49), the fraction and the further fraction being fractions of the liquid of which the level of CO 2 has been increased prior to separating it into fractions, characterised in that the membrane filtration device (16;16';34) is interposed between the at least one device (7;7';31) for increasing a level of CO 2 in the liquid and the processing section, and in that the at least one device (7;7';31) for increasing a level of CO 2 in the liquid is arranged to increase the level to an adjustable value.