Biofouling control strategy through denatured extracellular proteins: an empirical evidence from reclaimed water distribution systems

Abstract

Biofouling remains a significant challenge in water treatment fields, leading to a decline in the hydraulic performance, increased operational costs, and potential health risks. Previous biofouling control strategies primarily focused on the removal of particulates and microorganisms, often neglecting the role of extracellular proteins. Using a reclaimed water distribution system as an example, this study proposes a strategy to inhibit biofouling formation by utilizing urea, a reported protein denaturant with fertilizer functionality. Results indicated that urea significantly slowed the accumulation of biofouling, leading to a 16.4-49.4 % decrease in biofouling weight, an 18.6-55.3 % decrease in extracellular protein content, and a 25.9-45.3 % reduction in extracellular polymer substance (EPS) content. Urea mitigated biofouling through two mechanisms: (1) disrupting protein structures, which convert tightly bound EPS to loosely bound EPS, and (2) downregulating biofilm-forming signaling proteins, thereby inhibiting biofouling formation. In the process, proteins, polysaccharides, and microorganisms exhibited clear mutual promotion relationships. Additionally, urea weakened microbial symbiotic interactions by affecting protein signaling molecules, inhibiting microbial growth and polysaccharide metabolism. The research confirms that denaturing extracellular proteins to mitigate biofouling is a feasible and efficient approach. The findings aim to provide valuable insights for the development of sustainable and effective biofouling cleaning strategies