Investigating water safety in multi-purpose buildings used as an elementary school and plumbing remediation effectiveness

Abstract

Three buildings that were repurposed for use as an elementary school were shutdown for three months in response to the pandemic. Building cold and hot water quality was monitored before reopening to detect and resolve chemical and microbiological problems. The authors collected first draw pre-flush and post-flush water samples. First draw water samples did not contain detectable disinfectant residual, but nickel and lead sometimes exceeded the health-based action limits for cold water (max. 144 μg Ni/L, 3.4 μg Pb/L). Stagnant cold water at a bathroom sink (188 MPN/100 mL) and drinking water fountain (141.6 MPN/100 mL), in the same building, exceeded theL.pneumophilathresholds advised by the World Health Organization (WHO) (10 CFU/mL) and American Industrial Hygiene Association (AIHA) (100 CFU/mL). Fixture flushing was conducted to remove cold and hot stagnant water and noL.pneumophilawas detected immediately after flushing. Two weeks after no subsequent building water use, chemical and microbiological contaminant levels were found to be similar to levels prior to flushing with one exception. The maximumL.pneumophilalevel (kitchen sink, hot water: 61.1 MPN/100 mL) was found in a different building than the prior maximum detections. No repeat positive locations forL.pneumophilawere found during the second visit, but new fixtures were positive the organism. When this study was conducted no evidence-based guidelines for plumbing recommissioning were available. A single plumbing flush reduced heavy metal andL.pneumophilalevels below WHO and AIHA thresholds in all three buildings. Additional work is needed to examine the role of building size, type and plumbing design on fixture water quality in shutdown buildings.