The small size of nanoparticles is both an advantage and a problem. Their high surface-area-to-volume ratio enables novel medical, industrial, and commercial applications. However, their small size also allows them to evade conventional filtration during water treatment, posing health risks to humans, plants, and aquatic life. Our project aims to remove nanoparticles using two approaches: 1) bind citrate-capped nanoparticles with the membrane protein proteorhodopsin and 2) trap nanoparticles using E. coli biofilm produced by overexpressing two regulators -- OmpR234 and CsgD. We envision integrating our trapping system in both rural and urban wastewater treatment plants to efficiently capture all nanoparticles before treated water is released into the environment.