Water filtering apparatus, in particular apparatus using nanofiltration and apparatus using reverse osmosis; foam fractionation apparatus for enriching chemicals, toxic substances, contaminants, forever chemicals, compounds falling under the stockholm convention, fluorinated organic compounds, per- and polyfluorinated organic compounds, per- and polyfluoro alkyl substances, mixed per-/poly-fluoro-/halo-substances, pharmaceuticals, antibiotics, pesticides, flame-retardants, poly-chloro-dibenzo...