Innovative anti-biofouling reverse osmosis (RO) and nanofiltration (NF) membranes were developed. Membranes were produced via grafting of a bioactive, non-biocidal 2-aminoimidazole (2-AI) to the polyamide active layer of commercial RO/NF membranes, by coupling 2-AI to free carboxylate groups in active layers using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). 2-AI was grafted in the 0.44-1.08M range, which is several orders of magnitude higher than required for biofilm inhibition (IC50 = 162-420 mu M). Results showed that, compared to control (unmodified) membranes, 2-AI-modified membranes inhibited the growth of Pseudomonas aeruginosa biofilms by 61-96% (p = 0.01-0.12), and that the measured changes in surface charge, hydrophobicity, and roughness due to 2-AI grafting were not the main contributors to biofilm inhibition. Some loss of 2-AI from water filtration and membrane cleaning was observed, but 2-AI concentrations remained orders of magnitude higher than required for biofilm inhibition. Short-term performance results showed that compared to commercial control membranes, 2-AI-grafting resulted in statistically insignificant changes in salt rejection, and decreases in initial water permeability < 25%, being statistically insignificant for two out of the four membrane types tested. Overall, results support that 2-AI grafting to polyamide RO/NF membranes via activation of carboxylate groups with EDC is a promising approach to enhance current RO/NF water purification membranes.