*Article* **New Functionalized Macroparticles for Environmentally Sustainable Biofilm Control in Water Systems**

**Ana C. Barros 1,\*, Ana Pereira <sup>1</sup> , Luis F. Melo <sup>1</sup> and Juliana P. S. Sousa <sup>2</sup>**


**Abstract:** Reverse osmosis (RO) depends on biocidal agents to control the operating costs associated to biofouling, although this implies the discharge of undesired chemicals into the aquatic environment. Therefore, a system providing pre-treated water free of biocides arises as an interesting solution to minimize the discharge of chemicals while enhancing RO filtration performance by inactivating bacteria that could form biofilms on the membrane system. This work proposes a pretreatment approach based on the immobilization of an industrially used antimicrobial agent (benzalkonium chloride—BAC) into millimetric aluminum oxide particles with prior surface activation with DA—dopamine. The antimicrobial efficacy of the functionalized particles was assessed against *Escherichia coli* planktonic cells through culturability and cell membrane integrity analysis. The results showed total inactivation of bacterial cells within five min for the highest particle concentration and 100% of cell membrane damage after 15 min for all concentrations. When reusing the same particles, a higher contact time was needed to reach the total inactivation, possibly due to partial blocking of immobilized biocide by dead bacteria adhering to the particles and to the residual leaching of biocide. The overall results support the use of Al2O<sup>3</sup> -DA-BAC particles as antimicrobial agents for sustainable biocidal applications in continuous water treatment systems.

**Keywords:** biocidal particles; functionalization; benzalkonium chloride; *Escherichia coli*; antimicrobial activity
