The invention relates to a device for dispensing an aqueous liquid through an interface membrane made partially hydrophilic and partially hydrophobic, made so that when in operation, during each operation of dispensing a metered amount of liquid, the streams of air and liquid flow alternately in a capillary channel (18) downstream from the membrane. Said interface membrane (7) is made of a filtering material which includes biocidal metal cations in the body thereof. Said device comprises a porous insert (8), which is permeable both to liquid and to air, which is arranged upstream from the membrane in the path of the fluids and which is made of a material including sites with negative charges capable of attracting biocidal metal cations from said membrane.
