From July to September 1998, Sydney, Australia, experienced
a drinking water crisis after high concentrations of Cryptosporidium
and Giardia were detected in the city's water
supply and distribution systems. Three boil-water advisories were
issued, the Sydney Water Inquiry was formed to investigate the
incident's origin, and outside laboratories, experts, and auditors
were called in to assess the original analytical procedures and
results. This study reviewed the information submitted to the
inquiry and found evidence to confirm that the contamination did
occur and explain its causes.
The results of the Cryptosporidium and Giardia microbiological
analyses are in agreement with the body of limnological evidence
collected from across the supply system. This finding suggests
that the potable supply was contaminated when flood-waterborne
Cryptosporidium and Giardia short-circuited the storage reservoir
and entered the treatment plant in a series of pulses that also
produced rapid fluctuations in water chemistry. Limnological data
from the reservoir showed how the barrier was circumvented. A
simple mass balance model demonstrated that cysts and oocysts
also crossed the filtration barrier periodically.
Prior to the 1998 water crisis, the Sydney Water Corporation
had assumed that the barriers provided by a storage reservoir with
three years' average retention time and a modern filtration plant
would eliminate the risk of microbial contamination to its supply.
The water crisis highlighted some of the unforeseen contamination
risks to surface water supplies and emphasized the benefits
of maintaining multiple barriers against contaminant transport
through the system. Includes 28 references, tables, figures.
| Edition : | Vol. 95 - No. 5 |
| File Size : | 1
file
, 680 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 15 |
| Published : | 05/01/2003 |
