Biofilm Bacterial Communities in an Aging Chlorinated Drinking Water Distribution Line in Sri Lanka: Exploratory Findings and Research Needs

This study reports the incidental collection and exploratory analysis of a biofilm sample obtained from a water distribution pipeline in the Central Province of Sri Lanka, which had been in continuous service for approximately 50 years. Access to the pipe interior was achieved during a repair operation, providing a rare opportunity to directly sample an aged pipeline under the typical operating conditions of a tropical, developing country. An exploratory research design was adopted to examine the bacterial community composition and was explicitly framed as hypothesis-generating rather than testing predefined hypotheses. Bacterial community composition was analyzed using high-throughput MiSeq sequencing. At the genus level, the community was strongly enriched with Clostridium sensu stricto lineages, notably type 1 (relative abundance of 9.19%), type 12 (8.58%), and type 9 (3.09%). Several other genera, Nitrospira (4.94%), Bacillus (4.60%), Methyloligobacillus (3.75%), Hyphomicrobium (2.14%), and Haliangium (1.82%), occurred at moderate abundances, raising their potential consequences on biological and chemical water quality issues. Given the exploratory nature of the study, these findings represent site-specific biofilm characteristics in an aging drinking water distribution line in Sri Lanka. Although limited to a single biofilm sample, this study provides empirical observations from a rarely accessible environment and identifies knowledge gaps to guide future comprehensive investigations into biofilm dynamics, microbial ecology, and infrastructure management in tropical water distribution systems.