Investigating the role of physicochemical surface properties of polymeric pipe materials and a nanogel-based coating on microbial adhesion in unchlorinated drinking water

Past research focused on the effect that different polymeric pipe materials have on biofilm formation in drinking water distribution systems (DWDS), to determine the best one to deliver safe drinking water to customers. However, results are often contradictory. Here, we studied the influence of five polymeric pipe materials and a surface modification with the anti-adhesive poly(N-isopropylmethacrylamide)-based nanogel coating on early-stage biofilms formation in unchlorinated drinking water in simulated DWDS conditions. Coupons made from two high-density polyethylene (HDPE-1 and HDPE-2), two unplasticized polyvinyl chloride (PVC-1 and PVC-2), and a molecularly oriented polyvinyl chloride (PVCO) were characterized in terms of surface topography, roughness, chemistry, and hydrophilicity. Biofilms were grown from real drinking water on the selected materials in a flow-chamber setup simulating DWDS conditions, with and without nutrient supplementation. Biofilm growth for 72 h with nutrient addition led to the same extensive biofilm formation on all surfaces. Without nutrients supplementation, 35-days experiments showed significant biofilm development on HDPE-1 only, despite comparable surface properties and chemistry to HDPE-2, and smoother and more homogeneous topography than PVCs. Application of the nanogel coating on HDPE-1 resulted in an average reduction of 87 % in biofilm development regardless under which condition. Microbial community analysis of biofilms by means of 16S rRNA gene sequencing showed a common core microbiome on all included materials in both nutrient-rich and oligotrophic conditions, with a high variability even within duplicates of the same material. Presented findings in combination with multiple studies available in the literature suggest that no conclusion can be made of whether PVC or PE is ultimately better in preventing biofilm formation in DWDS, because it is mainly due to the manufacturer. The suggested application of a surface modification with the anti-adhesive nanogel coating could uniform materials behaviour, acting as a localized biofilm control strategy for DWDS sections (hotspots) especially prone to biofilm development.