Environmental Science & Engineering - www.esemag.com - May 2003
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New clarifiers for Québec water plant
An expansion at the Charny
Water Treatment Plant in the
city of Lévis, Québec, will
increase capacity from
26,000 m3/d to a design flow of
45,000 m3/d (6.9 mgd to 7.9 mgd)
upon commissioning in May 2003.
USFilter’s John Meunier Products supplied
two Actiflo® ballasted clarification
units and plant automation under a
US$1.07 million contract with Lévis, a
suburb of Québec City. These units
will comprise the first step in treating
raw water from the Chaudière River.
The effluent will be further treated by
three gravity-flow media filters.
The Actiflo units' high treatment
capacity and small footprint enabled
the city to increase total plant treatment
capacity within the same space
previously occupied by two sludge
blanket clarifiers, and without construction
of costly new basins. "The
Chaudière River flows through agricultural
areas and is among the most
polluted rivers in Quebec," said
Christian Scott, senior project engineer
with USFilter’s John Meunier
Products. "That and highly variable
quality caused by rainfalls and spring
snow melts make the river water
extremely difficult to treat. Pilot testing
in winter and summer conditions
has documented that the Actiflo
process was the best available to treat
the variable flows from the river."
The new plant treatment process
must meet a provincial turbidity standard
of 2.3 NTU, but city officials
expect the process to deliver water
consistently below 1 NTU. The project
includes a process guarantee.
The Actiflo process works on the
same principles as conventional water
treatment. Both use coagulant for
destabilization and flocculant-aid
polymer to aggregate suspended materials,
which are then removed by settling.
The primary difference in the
Actiflo process is the addition of
microsand to speed up floc formation
and settling. The microsand aids development
of chemical floc which is
claimed to be far denser and more
durable than floc in a conventional
clarifier. It also acts as ballast to
enhance settling and thus allow shorter
detention times and higher clarifier
overflow rates. That translates to a
smaller system footprint and lower
capital costs.
Besides all mechanical and chemical
and sand feed components of the
Actiflo system, John Meunier Products
provided control and instrumentation
and updated SCADA software for the
entire plant. Upon completion, all
plant processes will be fully automated.
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