Biofouling in hospital greywater systems: Implications for public health and antimicrobial resistance

Hospitals generate large volumes of wastewater containing pathogenic microorganisms, pharmaceutical residues, and determinants of antimicrobial resistance determinants, representing an increasing concern for public health and environmental safety. Hydraulic and operational conditions within hospital water infrastructure can promote the formation of microbial biofilms on internal surfaces, facilitating microbial persistence and potential dissemination. Greywater systems, which originate from sinks, showers, laundries and cleaning activities, are particularly susceptible to biofouling due to the continuous input of organic matter, disinfectants, pharmaceuticals, and microorganisms. Although hospital greywater is generally considered less contaminated than blackwater, these systems may still support opportunistic pathogens and antimicrobial-resistant microorganisms within plumbing-associated biofilms. However, despite increasing attention to hospital wastewater, biofilm formation in hospital greywater systems remains insufficiently characterized. Much of the available evidence is extrapolated from hospital plumbing, drinking water systems, and wastewater infrastructure. This review examines current knowledge regarding biofilm formation and biofouling processes in hospital greywater systems, with emphasis on: 1) the microbial composition and structural characteristics of biofilms associated with hospital greywater infrastructures; 2) environmental, chemical, and operational factors that influence biofilm formation and persistence; 3) the potential role of greywater-associated biofilms in microbial persistence and antimicrobial resistance dissemination; and 4) the implications of these processes for public health and environmental management. protection. The review also identifies major knowledge gaps and highlights the need for integrated monitoring, engineering, and management strategies within a One Health framework.