Roughness-controlled cell-surface interactions mediate early biofilm development in drinking water systems

Abstract

Bacterial colonization onto interior pipe walls is ubiquitous in drinking water systems, with the inevitable consequences on water quality safety. However, the mechanisms of how physicochemical properties of pipe materials interfering with cell-surface interactions and subsequent biofilm colonization in drinking water systems have not been fully unveiled. In this study, we investigated initial biofilm colonization onto polyvinyl chloride (PVC), polyethylene (PE) and stainless steel (STS) coupons having various surface roughness during one week incubation in bench reactors. Results display that increased surface roughness encouraged biofilm formation particularly on plastic materials. With the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) modeling analysis, the increment in surface roughness enlarged superficial area and hydrophobicity that reinforced van der Waals force and acid-base bacteria-surface interactions, thereof facilitating biofilm initialization and consequent accumulation. Meanwhile, the PVC and PE coupons attracted around six-fold and four-fold adhesive cells in contrast to the STS ones with the roughness of ∼1.50 µm, respectively. Unlike the STS that induced hydrophilic (repulsive) interactions, plastic materials encouraged hydrophobic (attractive) acid-base interactions and bacterial surface adhesion, accordingly contributing to ensuing colonization. Increasing ionic strength (1–100 mM) further stimulated initial colonization associated with compressed electrical double layer and decreased electrokinetic potential that reduced the energy barriers for bacterial cells. These findings reveal that early biofilm development is a pipe material and roughness-controlled process, which provide new insights into the mechanistic understanding of the ever-growing biofilms in drinking water systems.