After collection, beach water samples are brought to the EPD’s laboratory for analysis. The process is a relatively simple and reliable one. A portion of each sample is measured for pH, salinity and turbidity, while another portion is prepared for growing a culture of E. coli bacteria. To do this, the water sample is passed through a membrane to trap bacteria, and the membrane with its bacteria is then incubated for 18 to 24 hours. After this time, E. coli bacteria show up as green colonies on the membrane. The number of green colonies is then counted and their density calculated. Clearly, the lower the number for any given sample, the better the quality of the water.
The process of testing and analysing the water samples is relatively speedy at about one and a half days, which means the EPD can let the public know about health hazards or other water quality changes very fast.
[Image of analysing a water sample at the EPD laboratory]
[Image of E. coli colonies after incubation]
[Image of laboratory analysis of beach water samples]