1. TERTIARY TREATMENT TECHNOLOGIES & PRACTICES
Ontario’s Growth Plan establishes
a population forecast of 210,000 by
2031 for the City of Barrie. This is a
significant increase from the City’s
current population of approximately
142,000. As a result, the City of
Barrie has implemented a planning
process to account for this population
increase and nutrient loadings increase
to its Wastewater Treatment Facility
(WwTF). The treated effluent is required
to meet effluent discharge limits as
established by the Ministry of the
Environment and Climate Change’s
(MOECC) Environmental Compliance
Approval (ECA) and the more stringent
requirements for Total Phosphorus (TP)
under the 2008 Lake Simcoe Protection
Act (LSPA) and its 2010 Phosphorus
Reduction Strategy (PRS).
The City of Barrie’s WwTF is an
advanced tertiary treatment system with
final discharge to Kempenfelt Bay in
Lake Simcoe. It was last upgraded and
expanded in 2011 to its current capacity
of 76 million litres per day (MLD)
average flow. Unfortunately, this upgrade
(including detailed design and tendering)
was initiated and completed prior to the
enacting of the LSPA and PRS legislation.
Therefore, it was not possible to include
these new requirements in the design.
The planned expansion provided for a TP
design objective of 0.15 mg/L including
a safety factor to ensure compliance with
the previous ECA’s average monthly
concentration limit of 0.18 mg/L, but
the design was not meant to provide
compliance with the 0.10 mg/L annual
concentration limit specified by the PRS.
The WwTF consists of the following
treatment unit operations: screening, grit
removal, primary clarification, activated
sludge process using high purity oxygen,
secondary clarification, tertiary rotating
biological contactors, chemically-assisted
sand filtration and UV disinfection.
This treatment train, operating at its
current levels of approximately 52 MLD,
is capable of achieving its annual TP
concentration of 0.10 mg/L. Through
optimization efforts the WwTF has
been successful in achieving an average
of approximately 0.067 mg/L over the
last 18 months. Nonetheless, the total
loading imposed under the PRS of 2,774
kg-P/year imply that the City needs to,
consistently and progressively, reduce the
TP concentrations as population growth
produces incremental increase in annual
TP loadings.
Some of the non-point sources options
the City may explore in the future
include: implementing new or retrofits
of stormwater management (SWM)
facilities, e.g., the on-going Upper York
Sewage Solutions EA (York Region, 2014);
or the application of agricultural best
management practices, e.g. ,Town of New
Tecumseth’s Tottenham Sewage Treatment
Plant (MOECC, 2014); or TP offset
measures to be legislated under the LSPA,
which are being explored by the Lake
Simcoe Region Conservation Authority
among other participants (Tovilla, 2015).
While achieving more stringent TP
requirements through offsets with non-
point TP alternatives remains a future
option for the City (pending its corre-
sponding planning process and potential
approval by the Province), the City of
Barrie, in 2013, decided to evaluate differ-
ent technologies for low effluent TP at its
WwTF as a point-source type of solution.
A study was conducted to provide recom-
mendation on a preferred technology
solution. The scope of the study was to
complete a technology assessment for efflu-
ent TP using ultra filtration (UF) mem-
branes with a number of configurations
and pilot testing. At the initial assessment
process, the pilot testing results showed
that UF membrane technology could
consistently achieved 0.02 mg/L of TP on
average with tertiary filter effluent. The
subsequent objectives of the study were:
• to identify a design basis for nutrient
removal (TP) strategy development;
• develop a long list of strategies for
nutrient removal;
• screen the long list of strategies and
establish a short list of strategies; and
• evaluate the short-listed strategies and
identify a preferred strategy.
The City of Barrie:
Moving Beyond Tertiary Treatment
Stricter provincial TP effluent limits driving a multi-level treatment approach
to comply with loading requirements.
BY SANDY COULTER, B.SC., STEW PATTERSON, P.ENG., JOHN THOMPSON, P.ENG., AND EDGAR TOVILLA, P.ENG., THE CITY OF BARRIE.
FIGURE 1
The City of Barrie’s wastewater treatment facility (WwTF).
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2. TERTIARY TREATMENT TECHNOLOGIES & PRACTICES
The strategies to evaluate UF membrane
configurations were grouped in two:
• Group 1: Using membrane (in a tertiary
membrane filtration configuration) to
polish a portion of the existing sand
filter effluent or RBC effluent and
blending the membrane effluent with
the remaining sand filter effluent; and
• Group 2: Using membranes (in
a membrane bioreactor process
configuration) to treat a portion of the
flows in parallel to the existing sand
filters, and blend the effluent streams
from the membranes and the sand filter.
Value-added workshops were organized to
evaluate specific treatment configurations.
Some of the participants at these
workshops included: the City of Barrie, the
Ontario Clean Water Agency, AECOM,
CH2M, WSP, GHD and General Electric.
The Group 1 strategies were further
broken down in the following:
• Strategy 1A: Retrofit one sand filter
channel to house tertiary membrane units
• Strategy 1B: Retrofit UV channels to
house tertiary membrane filtration units
• Strategy 1C: New tertiary membrane
filtration facility
• Strategy 1D: Tertiary membrane
filtration located on top of secondary
clarifiers
• Strategy 1E: Tertiary membrane
filtration to treat RBC effluent
The Group 2 strategies were identified as:
• Strategy 2A: Retrofit one UNOX/
secondary clarifier train to membrane
bioreactor (MBR).
• Strategy 2B: Retrofit one UNOX/
secondary clarifier train to MBR with
new membrane tanks
• Strategy 2C: Tertiary membrane
filtration followed by MBR conversion
• Strategy 2D: Tertiary MBR.
Both screening and evaluation criteria
were developed for this process. The
screening criteria primarily concentrated
in having a proven technology, and its
reliability to meet current and future
regulatory requirements. The evaluation
criteria included concepts such as: ability
to provide stable nitrification, project
construction schedule, ease of expansion,
flexibility, reliability, ease of operation,
operational impact during construction,
footprint and impact on site use, impact
to the public, capital cost, O&M costs,
and ultimate cost.
As a result of the screening and
evaluation process, the MBR retrofit
(Strategy 2A) was recommended as the
preferred strategy (CH2M Hill, 2013).
It was concluded that the MBR train can
provide stable and reliable nitrification
including having a minimum green space
construction. Further, the MBR provides
a modular expansion approach to achieve
rated capacities beyond 76 MLD, noting
that it reduces the hydraulic load on the
remaining secondary treatment system
significantly (by approximately 40%).
It was also revealed that the MBR Retrofit
would have a minimum impact on the
plant operation during construction.
Finally, the results also showed the lowest
capital cost, moderate O&M costs and
the lowest ultimate cost to achieve future
planned expansions.
The study results noted that the MBR
retrofit strategy could have a design
objective as low as 0.04 mg/L of TP if
the design looks beyond the currently
approved 76 MLD and up to a 150 MLD
capacity (provided completion of the
planning process in the event of a future
capacity expansion), in order to maintain
the 2,774 kg/year TP loading.
For more information about the
City of Barrie’s WwTF and the projects
discussed in this article, please
contact Sandy Coulter at
sandy.coulter@barrie.ca or Stew
Patterson at stew.patterson@barrie.ca.
References:
CH2M Hill. (2013). Nutrient
Removal Strategy for the Barrie
Wastewater Treatment Facility
(WwTF), City of Barrie.
MOECC - ECA7550-9F8HZA
(2014). New Tecumseth’s
Tottenham STP, Retrieved from:
www.accessenvironment.ene.
gov.on.ca/AEWeb/ae/GoSearch.
action?search=advanced
[10 Jul 2015].
Tovilla, E. (2015) Environmental
Approvals Branch’s considerations
when evaluating water quality
offsets for new or re-rating of
municipal or industrial sewage
treatment plants, WEAO
Influents, Spring 2015, pp. 34-35.
York Region (2014) Upper York
Sewage Solutions - Environmental
Assessment Executive Summary,
Retrieved from: www.uyssolutions.
ca/en/resourcesGeneral/01-
ExecutiveSummary.pdf
[10 Jul 2015].
FIGURE 2
Conceptual process flow diagram for the MBR retrofit strategy.1
Note 1. Elements of this diagram are for illustrative purposes
and may not represent the actual process flow diagram.
Rated Capacity [MLD] TP Loading [kg/year] Compliance Limit [mg/L] Design Objective [mg/L]
76 2,774 0.100 0.080
102 2,774 0.075 0.060
150 2,774 0.050 0.040
TABLE 1 TP annual average concentration required to meet annual loading limit.
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