Environmental Science & Engineering - www.esemag.com - May 2005
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Satellite treatment technology helps Niagara Falls to meet Ontario's F-5-5 CSO requirement
By Geoff Burn, Derek Blakemore,David Watt and Peter Baker
Ontario’s Niagara Falls is
famous as a tourist destination
to view one of the
“Seven Wonders of the
Modern World” and with the construction
of a world class casino and several
new highrises and first class hotels,
the downtown tourist district is experiencing
rapid growth and revitalization.
Besides tourism, the city also has a
diverse economic base that includes
manufacturing, professional services,
construction, transportation, sport and
recreation, and entertainment.
The downtown development is
being serviced by infrastructure with
some sections installed at the turn of
the 20th century; much of this provides
combined drainage for sanitary wastewater
and stormwater. There is a system
of four pumping stations that collect
the flows from the downtown core
with all the flows converging at the
Central Pump Station, which conveys
wastewater to the local treatment plant.
Combined sewer overflows (CSO)
associated with the Central Pump
Station represent a significant portion
of the city-wide annual volume, with
peak instantaneous flows as high as
8,000 L/s. Historically, raw sewage
overflows occur during moderate-tosignificant
rainfall events, with
approximately 30 overflow events
annually to the Niagara River.
The Niagara River is one of ten
Areas of Concern as designated by the
Great Lakes Water Quality Agreement
between Canada and the United States.
Reduction of CSOs into the Niagara
River has been identified as one of the
projects to improve its water quality.
The Ontario Ministry of the
Environment (MOE), through the
application of Procedure F-5-5, will
require the City of Niagara Falls and
the Regional Municipality of Niagara
to meet the following criteria for combined
sewer systems:
- Capture and treat all dry-weather
flow plus 90% of the wet-weather flow
volume for an average year, during the
7-month wet-weather period commencing
within 15 days of April 1.
- 30% BOD5 removal for the 7-month
wet-weather period.
- 50% Total Suspended Solids (TSS)
removal for the 7-month wet-weather
period.
- TSS concentrations should not
exceed 90 mg/L for more than 50% of
the time for an average year.
The City of Niagara Falls and the
Regional Municipality of Niagara
embarked on a project that will result
in one of the first CSO abatement
facilities in Ontario to meet the Procedure
F-5-5 criteria.
A Municipal Class Environmental
Assessment established that the preferred
solution was to implement a
system-wide CSO control project that
includes a new Central Pump Station
(CPS) and a CSO High Rate Treatment
Facility (HRTF). This will provide
greater than 90% volumetric control of
wet-weather flow so that only flows in
excess of the combined capacity of
CPS and HRTF will bypass the new
pumping and treatment facilities.
The preliminary design phase
included an evaluation component to
select the preferred high rate CSO
treatment process. After reviewing a
comprehensive list of treatment
options, four technologies were evaluated
in detail: Vortex Separation, High
Rate Screening/Filtration, High Rate
Sedimentation, and Retention Treatment
Basins. Conceptual designs were
developed for each alternative in order
to allow comparative evaluation with
respect to effectiveness to achieve the
required MOE F-5-5 treatment levels,
facility sizing or footprint, reliability,
complexity of operations and ability to
be upgraded or expanded.
The comparative evaluation of the five technologies considered is summarized
in Table 1. Based on performance,
coupled with relative costs and
footprint considerations, High Rate
Screening/Filtration, Retention Treatment
Basins and Storage are not suited
to this HRTF Project. The two technologies
that appear most suitable are
Vortex Separation and High Rate
Sedimentation. Both processes are relatively
low in cost and have small footprints.
The former is less complex to
operate but may not meet the 90 mg/L
TSS limit without future enhancements.
The latter is more complex to
operate, but is able to meet the 90
mg/L TSS limit.
When considering these competing
factors, Vortex Separation is the preferred
technology for the following
reasons. First, it is the least complicated
technology and likely to be among
the lowest in overall costs. Secondly, it
is amenable to enhancements with
either chemical addition and/or filtration,
should the need arise.
High-Rate Sedimentation is also
likely to be cost-competitive and will
not require future enhancement.
However, when taking into account the
complexity of its operation, and the
need for chemical deliveries, storage
and feed operations, the technology is
less attractive than Vortex Separation.
Since each vortex technology is
slightly different it was decided that
the vortex equipment should be preselected.
Request for quotation documents
were prepared for the vortex
equipment for the Central HRTF. Two
suppliers were invited to prepare submittals
for this equipment. The submittals
were evaluated on both quality factors
and cost factors. The quality factors
include compliance with the technical
specifications and the quality of
references. Based on an evaluation of
the submittals, John Meunier, Inc.’s
FluidSep® was the preferred vortex
technology for the Central HRTF.
A value engineering team consisting
of industry experts further scrutinized
the recommended treatment
option. Vortex treatment technology
was ultimately recommended and
accepted by the City and the Region
due to the favourable life cycle cost
and ease of operation.
The preliminary design proceeded
based on the use of two 13-metre diameter
vortex units, each to treat a design
flow of 1,000 L/s and a peak flow of
2,000 L/s. A second value engineering
session confirmed the proposed preliminary
design, and led to several
enhancements to the project, which
resulted in additional cost savings.
Currently in the detailed design
stage there are a number of interesting
features that have been incorporated
into the project. Under normal
dry weather conditions the flow will
pass directly through to the Central
Pump Station where the sewage will
be pumped to the Stanley Avenue
Wastewater Treatment Plant. During
a CSO event, as the incoming flow
exceeds the capacity of the CPS then
the excess flow will begin to pass up
through two mechanically cleaned
COPA horizontal storm screens with
6-mm openings. These screens are
each designed for 4,000 L/s and used
for control of floatables in the wet
weather flow prior to entering into
the high rate vortex treatment system.
As long as the COPA screens are
operating there will be no bypassing
of the HRTF. The treated overflow
from the Central HRTF and any
bypass flows will be discharged to
the Niagara River.
While the vortex units have been
designed for a peak flow of 4,000 L/s,
hydraulically the vortex system can
pass 8,000 L/s, but at a reduced treatment
level. The 100 L/s underflow
from each vortex unit is collected in a
separate wet well and submersible grit
pumps transport the slurry to the CPS.
The capacity of the CPS was increased
to account for this underflow.
The detailed design is nearing completion
and there is a plan to call tenders
in the summer of 2005. It is estimated
that construction will be completed
in fall of 2006.
Associated Engineering lead the
preliminary and detailed design of the
Central Pump Station and CSO HRT
facility. Other consultants contributing
to the project include Brown &
Caldwell, XCG Consultants, Acres
International and Questor Veritas.
Geoff Burn, P.Eng., is Manager Civil
Infrastructure Systems Group,
Derek
Blakemore, P.Eng., is Detailed Design
Lead with Associated Engineering,
David Watt, CET, is with the City of
Niagara Falls and
Peter Baker, P. Eng.
is with the Regional Municipality of
Niagara.
Contact: steelp@ae.ca.
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