Water quality supply in a Portuguese teaching hospital: monitoring and studies on detection of critical points

Surveillance of drinking water quality is extremely important to human health, assuming greater relevance in hospital environments, especially to those individuals who are immunocompromised. This study is aimed to determine the effect of increasing free chlorine (Cl) concentration in a hospital water network in regard to water quality monitoring and microbial growth control, between 2010 and 2013 in Porto. The average of free Cl concentration in the period under analysis showed some heterogeneity per floor, varying between 0.84 and 1.25 mg/L. In addition, there was a rise in proportion of samples that exceeded WHO guidelines (free Cl ≥ 0.5 mg/L), particularly in the last two years of the same period. With respect to microbial analysis, 22.4% of the samples were positive for Legionella spp., 6.4% for Pseudomonas aeruginosa, 15% and 30.4% for aerobic plate counts at 36 and 22 ºC, respectively. The proportion of positive samples decreased throughout the period under analysis, in particular for Legionella spp. (41.7% in 2010 vs. non-detectable in 2013) and P. aeruginosa (10.8% in 2010 vs. 3.3% in 2013). These results are in accordance with the gradual rise in free Cl concentration (0.78 ± 0.94 mg/L in 2010 vs. 1.16 ± 0.51 mg/L in 2013). In conclusion, a suitable plan for drinking water quality was instituted which resulted in reducing microbiological growth in the waterwork network, improving public health protection. However, the detection of critical points associated with lower levels of free Cl were found on certain floors/points-of-use, requiring the need to improve the monitoring water treatment system and/or implementation of additional technologies.