B046 Office drinking water

Microbiological drinking water quality in a high-rise office building of Hong Kong

Brief:

Microbiological water quality of the drinking water is highly associated with enteric

diseases. In this study, the water quality for the water supply system of a typical highrise

office building in Hong Kong was examined. A comparison of the bacteria levels

between the high and low water consumption periods was made. Tap water samples (0.1

L) were collected at the water supply system every 4 hours from 08:00 to 20:00 in a

normal working day that had a working day prior and after and a normal working day

that followed a long weekend. The results showed that the bacteria counts ranged from

80 to 1000 CFU L−1. It was found that the bacteria counts at a time after a low water

consumption period were significantly higher. This was probably due to the

multiplication and accumulation of bacteria in the water storage system in low

occupancy hours. Among the bacterial genera identified, 59% were gram-positive

bacteria genera composed of Bacillus (6%), Micrococcus (28%), Staphylococcus (6%)

and others (19%), and 41% were gram-negative bacteria genera including Pseudomonas

(13%), Escherichia coli (1%) and others (27%). A low quantity of the faecal indicating

bacteria, E. coli, was detected with a relative abundance of 0.5-1.4%. Its presence was

probably due to bioaerosols generated from nearby WC flushing. Future investigations

regarding the probable transmission through a water supply system of high-rise office

buildings in sub-tropical climate were recommended.

Further Information:

Chan WY, Wong LT, Mui KW, 2007. Microbiological drinking water quality in a high-rise office building of Hong Kong, The 33rd CIBW062 International Symposium of Water Supply and Drainage for Buildings, 19-21 September, Brno, Czech Republic, Session C4, pp. 149-156.