Conventional wastewater treatment systems generally require multiple steps and complex procedures to remove aqueous pollutants and oil contaminants from polluted water. Herein, we fabricate an underwater superoleophobic membrane by cross-linking konjac glucomannan on pristine fabrics, demonstrating that the concept of oil–water separation and the principle of aqueous pollutant removal can be integrated. Such biopolymer-modified fabric not only separates oil–water mixtures with high efficiency (up to 99.9%), but also exhibits the intriguing characteristic of removing water-soluble pollutants (including polyaromatic dyes and heavy metal ions). As a proof of concept, the synthetic wastewater purified with biopolymer membranes was used to cultivate and irrigate pinto beans, causing no observable deleterious effect on seed germination and growth. These results further confirm the biocompatibility and effectiveness of biopolymer membranes, offering an encouraging solution to challenges including wastewater trea...