Challenges of Studying Water Storage Tanks in Distribution Systems: a field- and pilot-scale approach to understand the ecosystem
Gomez-Alvarez, V. Challenges of Studying Water Storage Tanks in Distribution Systems: a field- and pilot-scale approach to understand the ecosystem. Presented at Water Quality Technology Conference (WQTC), Cincinnati, OH, November 13 - 17, 2022.
Finished water storage facilities are tanks, reservoirs, or other facilities used to store water that will undergo no further treatment to reduce microbial pathogens except residual disinfections. Their purpose is to meet peak demand, provide emergency storage (including for fire protection) and maintain distribution system pressure. Public health data has implicated finished water storage tanks in waterborne disease outbreaks (e.g. Legionnaires and Salmonellosis) across the USA. Storage tanks are vulnerable to contamination from animals, air, influent water and storage structure materials (i.e., leached chemicals). In addition, excess water retention time may cause depletion of disinfectant which creates an environment favorable to microbial contamination and enhanced disinfection by-product (DPB) formation. Sediment accumulation and biofilm formation enhance the growth and accumulation of pathogens, cause nitrification, physical blockage of valves and pipes, and release of particles into DWDS. Very little information is available about the microbial occurrence in storage tanks. It is important to understand the biotic and abiotic characteristics of these systems which amplify the potential public health risk relative to the DWDS. The purpose of this research is to determine how and why these opportunistic waterborne pathogens can persist within storage tank systems and how to implement effective water management plans to mitigate exposure risks to pathogens.
Finished water storage facilities are tanks or reservoirs used to store water that will undergo no further treatment to reduce microbial pathogens except residual disinfections. Storage tanks are vulnerable to contamination, and excess water retention time may cause depletion of disinfectant residual which creates an environment favorable for microbial contamination. Very little information is available about the microbial occurrence in storage tanks. Development of next-generation sequencing technology has made the analysis of the storage tank microbiome possible and opens new perspectives in the microbial ecology of these ecosystems. The current research evaluated the storage tank microbiome in a field-based sampling approach and a pilot-scale experiment. A metagenome approach was utilized to characterize the microbial communities and metabolic functional profile of bulk water and sediment cores, of which two sections were examined (top and bottom). Adaptive traits that allow microbes to persist and respond to environmental changes, virulence and antimicrobial-associated genes are encoded at a genetic level. The microbial community is highly diverse with evidence of spatial and temporal structuring influenced by environmental conditions. Sediment accumulation causes water quality degradation with rapid disinfectant decay, including enhanced biological growth by protecting against disinfectant, and nitrification. Metagenomic data allowed the reconstruction of biogeochemical pathways (e.g., nitrogen, sulfur, and iron) and several draft metagenome-assembled genomes. These genomes (i.e., microbial species) harbored a diverse assemblage of virulence- and antimicrobial-associated genes. It is important to understand the biotic and abiotic characteristics of these systems which amplify the potential public health risk relative to the distribution system.