WC128 JanFeb2023 - Magazine - Page 15
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Gore Park in Hamilton, Ont.
The Woodward Avenue Drinking Water Treatment
Plant in Hamilton, Ont.
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3 The City's lead sampling program that confirmed
that more than 10 per cent of the lead samples
taken from residential plumbing systems with water
service lines exceeded 10 micrograms of lead per
litre (μg/L).
4 Lead service lines on public properties, like the
one pictured, are in the process of being identified
and removed.
Corrosion control using orthophosphate
In November 2018, the City began adding a phosphate-based
inhibitor in the Woodward Avenue Drinking Water Sub System
(DWSS) where lead sampling results exceeded the MAC. An
essential nutrient that is an approved safe additive to drinking
water, orthophosphate creates a protective barrier inside pipes
which reduces the release of metals, such as lead and copper from
household plumbing. The estimated average requirement of phosphorus for adults is 580 mg per day, and the City’s addition of
orthophosphate amounts to an increase of no more than 1 mg/L.
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Sampling and monitoring plan
To monitor the effectiveness of the program, the City of Hamilton completed a pre-implementation baseline sampling and then
a post-implementation sampling to monitor the effectiveness of
the lead control.
Three lead pipe loops were also installed in the Woodward
Avenue DWSS to monitor the effectiveness of the corrosion control. Monthly samples showed an overall decreasing trend, with
lead values at all three locations below 5 µg/L.
Winters says, “We expect the lead levels will continue to
decrease as the scale thickens and strengthens from continued
exposure to orthophosphate. The CCP results have been very
effective in a short period of time. It’s an important program as
it helps protect residents who can’t afford to replace the private-owned portion of their lead pipe and those properties that
don’t have lead supply pipes but still have leaded-brass fixtures
and lead solder in their internal plumbing.”
Secondary impacts stemming from the addition of orthophosphate were also observed in the distribution system. Although
pre-filter orthophosphate dosing has contributed significantly
toward reducing treated water aluminum levels, precipitation
of orthophosphate with aluminum was observed within the
distribution system. This impact was controlled through flushing
and did not contribute to aesthetic impairment noticeable to
customers.
WATER C AN ADA • JANUARY/ FEBRUARY 2023
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