lauren@kelman.ca

TERTIARY TREATMENT TECHNOLOGIES & PRACTICES
Optimizing Tertiary Treatment at the
Lindsay Water Pollution Control Plant
BY PAULA STEEL, P. ENG., ASSOCIATED ENGINEERING AND KYLE MURRAY, MASC., ASSOCIATED ENGINEERING
DAVID KERR, P. GEO., MANAGER OF ENVIRONMENTAL SERVICES, CITY OF KAWARTHA LAKES AND
JEFF JANISZEWSKI, OPERATOR AT LINDSAY WPCP, CITY OF KAWARTHA LAKES
Background
The Lindsay Water Pollution Control
Plant (WPCP) services the community
of Lindsay, which is part of the City
of Kawartha Lakes. The WPCP was
originally constructed in 1962-1964
as a facultative lagoon. The plant
has undergone a series of upgrades
throughout the years with the most
recent occurring in 1998. In its current
configuration, the Lindsay WPCP is
an extended aeration process with
tertiary treatment and UV disinfection
with a rated capacity of 21,500 m 3 /d.
Chemical precipitation using alum is
practiced in the secondary clarifiers,
with ballasted high-rate flocculation
used for tertiary treatment.
During the most recent upgrades,
The Ministry of the Environment and
Climate Change (MOECC) identified
that the effluent receiver, the Scugog
River, was considered a Policy 2
receiver in regards to phosphorus.
A receiver is considered to be Policy 2
if it exceeds the Provincial Water
Quality Objective for Total Phosphorus
(TP) (0.03 mg/L for streams).
To minimize further increases in
the concentration of TP within the
Scugog River, the MOECC applied
stringent effluent limits to the
FIGURE 1
Actiflo TM units at the Lindsay WPCP
amended Certificate of Approval (C of A).
The effluent objective and limit for total
phosphorus (TP) was set at 0.15 and
0.2 mg/L, respectively. This required the
implementation of tertiary treatment,
as secondary treatment with chemical
precipitation can typically only meet an
effluent TP concentration of 0.5 mg/L
(MOE Design Guidelines for Sewage
Works, 2008).
The Actiflo TM process provided by
Veolia Water Technologies was selected
as the preferred tertiary treatment
solution during the 1998 upgrades.
This was the first implementation of this
process for tertiary treatment in Ontario.
The Lindsay WPCP utilizes two units
operated in parallel; each is designed
for a maximum hydraulic capacity of
15,050 m 3 /d. Figure 1 presents a photo
of the units at the Lindsay WPCP.
This process is a high-rate
clarification process that uses ballasted
flocculation to achieve high levels
of solids and TP removal in a small
footprint. The units employed at the
Lindsay WPCP have a combined
footprint which is approximately half
of what would have been required for
deep bed media filtration and one third
of what would have been required for
shallow bed media filtration.
The Actiflo TM treatment process utilizes
four stages:
1. Coagulation – A coagulant is added
to the secondary effluent upstream of
the flocculation/clarification unit to
encourage agglomeration of suspended
solids, improving settling. At the
Lindsay WPCP, coagulant is added at
a collection chamber just outside of
the tertiary treatment building.
2. Injection – Both microsand and
a flocculent (polyelectrolyte)
are added to secondary effluent
and mechanically mixed within
the injection tank. The injected
microsand ballasts the flocs formed
as a result of the coagulation stage.
3. Maturation – Flocs are gently mixed
using a mechanical mixer during an
approximately four-minute hydraulic
retention time to encourage the
further agglomeration of solids and
the development of flocs.
4. Counter Current Lamella
Clarification - Lamellar plates
inclined at 60° angles increase the
efficiency of settling, allowing flocs
to precipitate to the bottom where
they are subsequently collected by
a sludge hopper and pumped to
hydrocyclones located above the
injection tank. The microsand is then
separated from the sludge and reused
through the process. The hydraulic
retention time in the clarification step
is approximately two minutes.
Figure 2 illustrates the configuration of
the process.
Historical performance
The TP removal achieved at the Lindsay
WPCP since the treatment units have
been installed has been excellent.
Figure 3a presents the average annual
effluent TP concentrations between 2001
and 2013 with comparisons made to
both the C of A imposed objectives and
limits. Figure 3b presents the average
52 INFLUENTS Fall 2015
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