Microbiological effects of copper and other abiotic factors in drinking water and touch surface environments

Humans spend most of their time indoors. The built environment with its systems (e.g. water system) should be designed and operated in a way that it is microbiologically safe in all stages of operation. Copper is a widely used material within indoor environments and may aid to maintain low bacterial counts in drinking water and touch surface environments depending on the surrounding circumstances e.g. water/air interface, biofilm formation or soiling. Basic knowledge of the composition of drinking water bacteria has been earlier limited only to a small cultivable fraction of bacteria. Next-generation sequencing (NGS) technologies help to reveal entire microbial communities and to date these approaches are also extended to cover studies on drinking water systems. This thesis focuses on the unique microbiological niches of drinking water and touch surface indoor environments utilizing up-to-date technologies and real-life environments with emphasis on environmental factors that shape such microbiota. The role of copper in both water and air interfaces is of special interest. NGS approach was utilised to evaluate the effect of copper pipelines on biofilm or water micro- biota under real-life circumstances (full-scale water system) and under controlled conditions (pilot-scale system). Copper was compared to another commonly used pipeline material, cross-linked polyethylene (PEX). Environmental conditions i.e. the effect of cold and hot water systems with different flow regimes and temperatures (full-scale), and disinfection and magnetic water treatment (pilot-scale) were studied by NGS or traditional analysis methods in which stagnated water represented the worst-case scenario for water quality. The microbiological effects of copper in touch surface environment were studied at different real-life facilities under varying environmental circumstances (e.g. usage profiles, cleaning). This thesis successfully revealed the active and dormant bacterial inhabitants of the drinking water system utilizing 16S ribosomal RNA gene amplicon sequencing and ribosomal RNA as a template. For public health relevance, Legionella spp. were suggested as inactive using the RNA approach. Operational conditions (stagnation, temperature) and increased disinfectant concen- tration were revealed as important environmental factors that shape drinking water bacterial populations. Moreover, the study emphasizes the importance of use of only fresh water for drinking water usage, in accordance with the current recommended practises. Based on this study, copper pipelines showed similar characteristics to PEX pipelines without antibacterial properties in drin- king water systems. At the air interface however, copper showed antibacterial properties with varying real-life circumstances. Thus, its usage as an antibacterial touch surface material can be recommended especially for small frequently touched items that were shown to possess the highest microbial counts.