Figures illustrate a pipe containing biofilm and a scanning
electron micrograph (below) of the surface of a pipe containing
bacteria, isolated from Walkerton during the
investigation in 2000.
Victims of the Walkerton drinking water tragedy
moved a stage closer to closure five days before
Christmas when Stan Koebel, 51, formerly the
town’s utility manager, was sentenced to one year
in prison. While responsible for the water treatment system,
he had lied and falsified records. An outbreak of E. coli
O157:H7 killed seven people and sickened some 2,500 people,
many of them children. His younger brother Frank, 46,
judged less culpable than his older brother, was sentenced
to nine months house arrest.
Both brothers had pleaded guilty on November 30 to
lesser charges of common nuisance which carried a maximum
sentence of two years. Justice Bruce Durno said he
could not solely blame the Koebel brothers for what was
wrongly termed Canada’s worst drinking water disaster.
This particular E. coli was implicated some years ago,
causing both death and disease from hamburgers in a US
restaurant. Indeed, for a while, this particular strain of E.
coli was called pink hamburger disease and was the subject
of a book by Robin Cook called Toxin which I read some
ten years ago. In the hands of this famous author, who is
also a medical doctor, E. coli epidemiology was blended
into a powerful drama while giving new insights into the
lethality of this bacterium which had not then made its
debut as a publicized water threat.
Many people in Walkerton were outraged by what they
felt was a light sentence. The tainted water has resulted in
severe and continuing illness among residents and the economic
costs continue to be high. Businesses failed and jobs
were lost. In addition to the high legal and medical costs,
the widely praised report by Justice O’Connor into the incident
runs into millions of dollars.
It is ironic that simple chlorination procedures, wellhead
maintenance and scheduled water mains scouring and
flushing would almost certainly have prevented this
appalling human and economic tragedy.
An in-depth paper, given by Garry Palmateer to a Toronto
seminar following the Walkerton incident, gave me a new
perspective on water-borne diseases and infrastructure
maintenance. Photos projected on his powerpoint revealed
some shocking views of tuberculated infrastructure.
Garry said that even when the infrastructure was dosed
with chlorine – wiping out many of the bacteria – tuberculation
still allowed E. coli to escape the chlorine in the
various nooks and crannies, to emerge to reproduce again.
Seeing this macabre colour shot of the tuberculated pipe,
I thought it looked somewhat like a Harry Potter version
of downtown city skyscrapers. When Garry uses more scientific
nomenclature to describe the lethality inherent in
tuberculation the reality is even more dramatic.
I quote from his article:
“Bacteria trapped in biofilm can be protected from
direct contact with the external environment. For this reason,
disinfection systems useful for bacteria in the water
phase may not be effective to kill bacteria in biofilm structures.
Studies have shown that pathogenic microorganisms
such as E. coli, Salmonella, Yersinia, Campylobacter and
Cryptosporidium can all be harbored in the biofilm of
water distribution systems (Percival et al., 2000). Several
reports have also shown that E. coli and E. coli O157:H7
can survive and grow in biofilms (Keevil, et al., 1999;
LeChevallier et al., 1988). Many studies show that pathogenic
bacteria introduced into a water distribution system
can survive and grow in biofilms.
“Investigators have shown that chlorine levels traditionally
used in water treatment systems are inadequate to kill coliforms
incorporated into biofilm. For example, E. coli was
found to withstand 2400 times more chlorine when attached
to a surface then when it was a free cell (LeChevallier et al.,
1988). Therefore, the importance of biofilm formation in the
distribution pipes cannot be underestimated.”
Taxpayers often complain that their municipal water
costs are already too high: the fact is that Canadians enjoy
the safest and lowest priced water supplies anywhere on
the planet. I have seen people complaining about paying 75
cents a cubic metre for their drinking water while nursing
the now ubiquitous 200 m/l plastic water bottles.
Since Malthus, economics have been called the dismal
science. The Walkerton tragedy has confirmed its gloomy
relevance.
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