Quantitative Performance Evaluation of Interventions for Pathogens and Chemical Contaminants in Building Water Systems: A Review and Meta-Analysis

Building water systems are associated with variable water age and temperatures, causing water quality concerns. Legionella spp., nontuberculous mycobacteria (NTM), and Pseudomonas spp. are known to inhabit and grow in these systems for which building-level interventions are often required to reduce their concentrations and detections. Other contaminants such as metals and disinfection byproducts (DBPs) are also health concerns. Interventions are typically flushing, temperature manipulation, responsive facility-level interventions (e.g., chemical disinfection and heat shock), or point-of-use devices. A systematic literature review was conducted to summarize interventions targeting pathogen control, and subsequent meta-analysis quantified their respective log reduction values (LRVs). Across the studies (n = 45), Legionella spp. was the primary target (n = 45), and studies varied from laboratory benchtops/pipe racks to hospitals and residential or commercial buildings. Additional measurements and LRVs for heavy metals (e.g., copper, lead, and iron) and DBPs such as trihalomethanes (THMs) were evaluated. The findings pointed to the importance of contextual conditions and incoming water quality in playing a role in both pathogen occurrence and intervention effectiveness. Common interventions such as recommissioning flushing and increased temperature should be further examined for their impacts on pathogens besides Legionella spp. and their contribution to biofilm sloughing and pathogen regrowth. Trade-offs, such as increased metal leaching in parallel with pathogen inactivation, should be examined in context with intervention and building water quality conditions.