Bacterial pathogens contaminate urban stormwater runoff, prevent non-potable reuse and threaten public health. The Engineered Infiltration System (EIS) is one of the most popular technologies among Low Impact Developments (LID) used to efficiently treat stormwater, and has shown high efficiencies in removing a broad range of contaminants, including bacterial pathogens. However, the impact of biofouling of EIS on the retention of pathogens is largely unknown. The present study investigates the impact of the biofilms of bacterial species isolated from model EIS sand columns inoculated with stormwater (Chryseobacterium culicis, Chryseobacterium artocarpi, Pseudomonas monteilii) and a model biofilm forming isolate (Pseudomonas aeruginosa) on the retention of E.coli through EIS. The breakthrough curves show that all 4 biofilms dramatically increase the retention rate of E.coli cells. To understand the mechanism of improved retention, the interaction force between the biofilms and Carboxyl-Modified-Latex Beads (CML), a surrogate of E.coli cell, was examined by Atomic Force Microscope (AFM). The obtained AFM data were processed by a self-developed Python program to analyze the interaction force and indentation depth. The force-distance curves present long range (about 1200 to 1750 nm) adhesive force when retracting probe from all storm water isolate biofilms but not the P. aeruginosa biofilm. The long-range adhesive forces are likely produced by the stretching of polymers on biofilm that formed bonds with CML surface during contact. The adhesive force also occurs at minimal indentation positions, which suggests the adhesive properties of extracellular polymeric substances (EPS). Our study demonstrated that the biofouling of EIS can potentially improve the retention efficiency of bacterial pathogens, and advanced the knowledge on the behind retention mechanisms.

Impact of biofilms on the retention of pathogens in engineered infiltration system (EIS)

256th National Meeting (2018)

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