British Columbia’s mountainous
landscape presents unique
challenges to the distribution
and supply of drinking water.
The City of Coquitlam, located just
east of Vancouver in British
Columbia’s lower mainland, covers
land that includes lowlands along the
Fraser River and extends up the local
mountains to areas such as the
Westwood Plateau.
Coquitlam had been receiving
domestic water from the Greater
Vancouver Regional District (GVRD)
for years. The water was received with
0.7 to 0.8 ppm chlorine residual which
was typically sufficient for distribution
to most of the low lying areas. In the
case of the Westwood Plateau, a residential
development stretching up the
local mountainside, the water required
pumping up through a series of five
reservoirs that served the local residents.
On occasion, this uphill journey
resulted in the loss of the chlorine
residual and the potential for growth of
microbial contaminants.
The City required a means of rechlorinating
the water at two points in
the system. Through evaluation of
many options, the choices were narrowed
down to three alternatives: two
on-site chlorine generation systems
and the PPG Accutab Calcium
Hypochlorite system.
The City evaluated the three alternatives
and the PPG Accutab system
was chosen based on the following:
Life cycle costing based on 10 to 20
years showed no difference between
the systems but the Accutab system
had a much lower capital cost;
Ease of handling the pails of chlorine
tablets;
The system was the only system that
would fit into the existing space;
The fact that the system is NSF
Standard 61 approved for drinking
water applications.
The system in Coquitlam has been
running for some three years and has
allowed the operations staff to achieve
their main goals.
The latest Accutab system incorporates
a patented, non-flooded chlorinator
at the heart of the system. The
tablets are delivered in easy-to-handle
25 kg pails of 3-1/2” Calcium
Hypochlorite tablets. The tablets contain
nominal 68% available chlorine by
weight. Erosion rates are determined
by the flow rate of the water through
the chlorinator which, in turn, determines
the chlorine delivery rate. This
system produces a consistent, low concentration
solution (approximately 100
- 700 ppm of chlorine) which is then
metered back into the distribution system.
The consistency of the solution
concentration makes the delivery more
repeatable and easy to control.
As insurance against calcium scale,
a scale inhibitor is contained in the
tablets that sequesters up to 750 ppm
of hardness. This scale inhibiting
insures that the system remains reasonably
scale-free, requiring cleaning
only once or twice per year in most
applications. Successful installations
exist throughout the US in areas such
as Arizona where water hardness is a
significant issue.
Accutab systems have been
installed or are being commissioned by
Langley, Whistler, Elkford, and
Burnaby.
Contact Greg Vissers, Vissers Sales
Corp., e-mail: greg@vissers.on.ca.
See our home page on how to order your subscription. We regret we can
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