Upgrading Sainte-Julie wastewater facilities in Québec
By Ivy Cormier
Different media types Inset: Reactors
inside the pilot trailer.
The Town of Sainte-Julie,
Québec, is facing rising populations
and more stringent
effluent standards, making an
upgrade to their existing wastewater
treatment facility virtually inevitable.
Currently, the wastewater treatment
plant (WWTP) consists of a series of
four lagoons, with minimal land area
for expansion. While considering technology
that would help maximize the
organic removal of the existing plant,
the Town of Sainte-Julie commissioned
AnoxKaldnes, Inc. to conduct a pilot
study of the Moving Bed® Biofilm
Reactor (MBBR) process at its wastewater
treatment facility. The Town set a
target of less than 29 mg BOD5 /L after
decanting for 30 minutes, which was
met from the effluent of the single stage
MBBR at 26 mg BOD5 /L.
The MBBR operates as a stand-alone
treatment process with no return
activated sludge from a secondary clarifier,
thereby minimizing operator
maintenance and time. The MBBR
process utilizes polyethylene carrier
elements which are suspended and
mixed using custom designed medium
bubble aeration systems or mechanical
mixers, depending on the process application
of organic removal, nitrification,
or denitrification. Because the media is
kept within each basin by custom
designed sieves, the bacteria have a
chance to mature into specialized
“workers” within each separate basin,
consuming whatever food is available,
organics, ammonia, or nitrates. The
media also are constantly sloughing the
sieves, creating a process with no head
loss or need for backwashing.
Due to the increased surface area for
bacterial growth created by the addition
of media, it is possible to multiply treatment
capacity with minimal footprint.
Additional capacity can also be added
by simply adding more media. The K1
type biomedia, used in the pilot study in
Sainte-Julie, provides 500 m2 of surface
area per each m3 of media, allowing for
increased treatment capacity within a
compact area.
The AnoxKaldnes Pilot System that
was used for this study is a 20 foot containerized
trailer built onto a chassis for
easy transport between sites. The pilot
unit comes complete with an influent
chamber with a 6mm punch plate
screen, two 156 US gallon stainless
steel reactors fitted with an aeration
system and specially designed sieves,
and a stainless steel hopper clarifier.
Also included are blowers, pumps, testing
equipment, including online and
manual DO and pH probes, flow
meters, composite samplers, and a
refrigerator. The trailer also includes a
full laboratory set up for on-site testing
of samples. Such equipment includes:
HACH spectrophotometer, COD reactor,
digital balance, vacuum pump, TSS
oven, VSS furnace, and glassware.
The pilot study at Sainte-Julie
WWTP was carried out from October
2004 to February 2005, with both reactors
running in series under aerobic
conditions. Effluent from the first
lagoon of the plant was used as influent
to the pilot trailer, and effluent was discharged
directly to the second lagoon.
The first reactor in the series was filled
to the maximum 67% fill with biomedia,
whereas the second reactor was
filled to 58% with biomedia.
Throughout the study, the average flow
rate was 1.875 US gallons per minute
(7.10 litres per minute), providing a
BOD load of 0.66 kg/day and an NH3-
N load of 0.165 kg/day. The hydraulic
residence time was 1.39 hours in each
reactor, with a total of 2.77 hours for the
complete two-stage system.
The main goal of the pilot study was
to demonstrate the MBBR’s ability to
remove organic matter in a single stage
by reaching an effluent goal of less than
29 mg/L TBOD, after a 30 minute settling
period. This goal was achieved, as
the average concentration of decanted
BOD (DBOD) from the effluent of the
single stage MBBR was 26 mg/L at an
average loading rate of 3.29 g Total
BOD5 (TBOD5)/ m2-day. Effluent from
the two-stage MBBR averaged 20 mg/L
DBOD.
Although the main goal of the study
was to demonstrate increased organic removal, nitrification was achieved in
the second stage of the MBBR. The
WWTP currently does not have effluent
requirements for ammonia, but future
regulations are on the horizon. At an
average loading rate of 0.8 g NH3-N/
m2-day, the MBBR removed an average
of 76% of the load. Even at temperatures
as low as 3.0°C, the average effluent
was 3.9 mg/L, down from an average
influent of 16.2 mg/L.
Temperature, dissolved oxygen, and
pH were constantly monitored throughout
the study both manually and by
online instruments. pH throughout the
MBBR remained stable during the
study, even as influent pH spiked above
the target maximum of 7.5 in January.
Dissolved oxygen was kept above the
target concentration of 3 mg/L in the
first reactor and 6 mg/L in the second.
Temperatures ranged from 17.5°C in
November to 3.0°C in January.
The MBBR is evaluated based on
the organic removal versus the loading
rate for the effective surface area of the
media in the basin. Surface area loading
rate (SALR) is calculated by multiplying
influent organic concentration by
flow to obtain organic load and dividing
that value by the effective biofilm carrier
element surface area provided in the
MBBR.
Through regression analysis conducted
on SALR data and actual
removal rates, a 50% removal of TCOD
at loading rates of up to 12 g/m2-day
and 57% removal of DCOD at loading
rates up to 6 g/m2-day was predicted.
Regression analysis run on SALR and
removal rate data collected for NH3-N
predicted a 50% removal in the second
reactor only. Average actual removal of
NH3-N in the two-stage MBBR was
77%. Since influent soluble BOD5 was,
on average, less than 6 mg/L, total
BOD5 consisted primarily of TSS. The
MBBR reduced overall organics by
increasing flocculation and degrading
sludge, reducing TSS effluent concentration
to 35 mg/L out of the second
stage, down from an influent concentration
of 118 mg/L.
The Moving Bed Biofilm Reactor
process is the product of over a decade
of careful research and development. Its
principle of packing a rich amount of
surface area for biomass growth into a
compact reactor yields a reliable system
with small footprint and price tag. The
flexible technology, proven by numerous
full-scale installations and pilot
studies, is a solution to treatment plants
looking for an upgrade with minimal
new tankage.
Ivy Cormier is the Senior Pilot
Technician for AnoxKaldnes Inc.
E-mail: ivy@anoxkaldnes.com
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