STARTUP AND OPERATION OF A BIOLOGICAL
AERATED FILTER (BAF) FOR SIMULTANEOUS BOD
REMOVAL AND NITRIFICATION AT THE LOU ROMANO
WATER RECLAMATION PLANT
WINDSOR ONTARIO CANADA
International Joint Commission
“Water & Wastewater Treatment Best Management Practices Forum”
Monday, March 26, 2012
Wayne State University, Detroit MI
Paul Drca
Manager Environmental Quality
City of Windsor
Presentation Outline
1. Introduction
2. The Lou Romano Water Reclamation Plant (LRWRP)
3. Pilot Plant Studies
4. Selection of Biological Aerated Filter (BAF) for Secondary
Treatment
5. LRWRP MOE Certificate of Approval
6. BAF Startup & Challenges Encountered
7. LRWRP Effluent Quality
8. Conclusions & Questions
Introduction
Prior to 2007, the City of Windsor’s Lou Romano
Water Reclamation Plant, formerly called the West
Windsor Pollution Control Plant, was the largest and
one of the last remaining primary chemical physical
wastewater treatment plants in the Great Lakes
basin. The plant effluent is directly discharged to the
Detroit River, one of 43 areas of concern identified by
the International Joint Commission (IJC) requiring
remedial action with respect to beneficial use
impairments.
Introduction
Realizing the need to upgrade the LRWRP to
secondary treatment, the City performed pilot plant
studies in 1989-91 and 1994-96 to investigate
innovative alternatives to conventional secondary
treatment in an effort to determine the preferred
process for their needs and to minimize wastewater
treatment plant expansion costs
Environment Canada’s Great Lakes Sustainability
Fund (GLSF) provided funding assistance for the pilot
plant studies
The LRWRP - Background
• Construction of the plant began in 1967 and it
commenced operation as a 110,000 m3/d primary
treatment plant in 1970
• In 1974 it was converted to a physical-chemical
treatment plant incorporating phosphorus removal
• Numerous upgrades and expansions of the plant
occurred throughout the 1980s
The LRWRP - Upgrade &
Expansion
• In 2005, the City commenced with an upgrade and
expansion of the LRWRP that included the expansion
of primary treatment rated capacity from 163,700
m3/d to 272,800 m3/d and the construction of a BAF
for secondary treatment with a rated capacity of
218,000 m3/d.
• The plant is designed to handle a peak flow of two
times the rated capacity.
The LRWRP - Upgrade &
Expansion Other Work included:
• New coarse bar screens and conveyors
• New primary sludge pumphouses
• Primary effluent pumping station
• Ultraviolet (UV) disinfection (secondary effluent)
• Sodium hypochlorite (bypass flows) disinfection
facility
• New centrifuge sludge dewatering equipment
The $110,000,000 upgrade and expansion of the
LRWRP is the largest single project ever undertaken
by the City of Windsor
The LRWRP BAF Construction
Construction of Secondary Treatment
Biological Aerated Filters
Pilot Plant Studies
• Pilot testing was completed in two phases
• 1989-91 - Rotating Biological Contactor (RBC),
Trickling Filter/Solids Contactor (TF/SC), Biological
Aerated Filter (BAF) and Modified Activated Sludge
processes were piloted
• 1994-96 - TF/SC and BAF were selected for further
testing as to their suitability for the LRWRP upgrade
• Effluent objectives during the study were 15, 15, 0.5
and 3.0 mg/l BOD, TSS, TP and NH3-N respectively
Biological Aerated
Filter Pilot Plant
Selection of Biological Aerated Filter
(BAF) for Secondary Treatment
• BAF was selected as the solution for the City’s need
to upgrade the LRWRP to secondary treatment due
to its compact footprint and ease of future
expandability on the site.
• The advantages of the BAF are both financial and
environmental, capital costs are approximately 25%
less than conventional alternatives and the BAF
footprint is approximately one third of what a
conventional secondary treatment plant of the same
capacity would occupy.
Biological Aerated Filter Process
LRWRP MOE Certificate of
Approval
Parameter Effluent Limit *
CBOD5 15.0
TSS 15.0
TP 0.5
Un-ionized NH3 0.1
Acute Lethality to Rainbow
Trout & Daphnia Magna
Non acutely lethal
E. Coli 200 organisms/100ml
pH 6.0 – 9.5
*Effluent limits are monthly average concentrations in mg/l
unless otherwise indicated
LRWRP MOE Certificate of
Approval
COA Compounds
Lindane
Chlordane
Aldrin/Dieldrin
Cadmium
Mercury
PCBs
Benzo(a)pyrene
Hexachlorobenzene
COA Compounds –
plant effluent analyzed
quarterly
LRWRP MOE Certificate of
Approval - Compliance
• As of August 2010, the LRWRP has consistently met
C of A limits
• A result of proactive process improvements including
basing BAF cell run time on loading criteria and
primary effluent quality
• No COA compounds other than trace amounts of
mercury and cadmium detected in effluent
• Plant effluent has consistently been non acutely
lethal to Daphnia Magna and Rainbow Trout
• UV system has successfully replaced chlorine for
disinfection
BAF Startup & Challenges Encountered
• 80% BOD removal within 3 weeks of startup
• Steady nitrification by June 2008
Challenges
• Foaming
• Soluble phosphorous deficiency
• TSS compliance
• BAF cell loading
• Media loss
• Primary effluent & backwash supply tank screening
• Backwash cycle time
0
20
40
60
80
100
120
140
160
180
200
BO
D (
mg
/l)
BOD Removal Within 3 Weeks of Startup
INF BOD PRI EFF BOD BAF EFF BOD
Foaming
• Lots of foam covered BAF cells on startup
• Primary effluent dosed with defoamer and cells were
covered with tarps to control foam
• Upon establishment of sufficient biomass, foam
subsided
• Foaming is still an issue at times
• Tarps have been removed, defoamer is still required
at lower doses
Soluble Phosphorous
Deficiency
• Pilot plant testing indicated PE was soluble P
deficient
• Full scale plant was designed with H3PO4
supplementation
• H3PO4 dosed to deliver 1 mgl-1 P to PE to maintain a
concentration of 0.2 - 0.3 P in BAF effluent
• P supplement is expensive – ongoing project with
University of Windsor to optimize P removal in PE to
eliminate or minimize need for P supplement
TSS Compliance
• On startup, LRWRP did not consistently meet TSS
limit of 15 mgl-1 on a daily basis
• Variable TSS loading from PE was found to be a
contributing factor due to dewatering centrate, BAF
backwash solids return to primary clarifiers, and wet
weather flows.
• Since the summer of 2010, BAF cells have been
backwashed based on solids loading instead of fixed
filtration time.
TSS Compliance Solution
• Monthly strong backwashing frequency was doubled
and spread out through the month
• Backwash procedure was revised for efficiency
• Monitoring and maintaining primary clarifier surface
overflow rate (SOR) - target of 20 m/h SOR
• An additional chemical feed line for alum was
extended to the backwash waste discharge pipe (just
prior to primary treatment)
• Cell cycle time is set based on BAF media loading
criteria and primary effluent quality
Data Constants
TSS 1.26 30 day maximum loading in - kg TSS/m3d
TKN 0.59 31 day maximum loading in - kg TKN/m3d
Cell Area 144 m2
Media Depth 3.9 m
Media Volume 561.6 m3
Hours/day 24
Avg. Daily
Flow
(MLD/day)
Avg.# of
Cells in
Filtration
Primary
Effluent
TSS
(mgl-1)
Primary
Effluent
TKN
(mgl-1)
Max
Duration
of TSS
Cycle
(h)
Max
Duration
of TKN
Cycle
(h)
Max
Filtration
Time
(h, min of
TSS/TKN)
Filtration
Time
(h, 3 day
running
avg)
147.0 8.0 39.0 10.0 23.7 43.3 23.7 24
125.0 6.8 39.0 10.0 23.7 43.3 23.7 24
132.7 7.2 37.0 20.0 24.9 21.6 21.6 23
173.6 8.5 60.0 20.0 13.9 19.5 13.9 20
107.5 6.8 60.0 20.0 17.9 25.2 17.9 18
124.5 6.9 60.0 34.0 15.7 13.0 13.0 15
125.0 7.0 10.0 34.0 95.1 13.1 13.1 15
2010 LRWRP BAF TSS
0
20
40
60
80
100
120
01/01/2010 01/04/2010 01/07/2010 01/10/2010 01/01/2011
TS
S (
mg
/L)
BAF Influent
BAF Effluent
• Changed from filtration time to solid loading in the summer of 2010
• Significant improvements in LRWRP effluent quality
Media Loss
• Media loss was excessive during 2008-09
• Geyser type eruptions of media during backwashing
resulted in media being returned with backwash
wastewater
• Media was recovered from the backwash waste tank
• Media loss appears to have subsided since process
improvements implemented as of Aug 2010
• Evaluation of media loss is ongoing
Media loss experienced during backwash
Backwash Cycle Length
• The length of time to complete a cell backwash is a
concern
• This is only an issue when backwashes are queued
up
• Using the BAF configuration to full advantage, it is
possible to start a backwash before an ongoing
backwash is completed through programming
modifications
• These modifications will result in up to a 45 minute
decrease in average backwash time
Primary Effluent & Backwash
Supply Tank Screening
• Nozzles delivering PE and backwash rinse water to
BAF cells require protection from plugging
• 4 channels fitted with fine curved screens filter PE to
the BAF cells
• 4 screens filter BAF effluent prior to storage in the
backwash supply tank
• Weekly power washing of fine curved screens is
required
• Backwash supply tank screens are washed as
required – up to a 3 day interval between service
Primary Effluent Fine Curved
Screens
Backwash Supply Tank
Screens
Future Work
• Media loss quantification
• Media fluidization criteria
• Primary clarifier optimization
• Backwash efficiencies
• Energy management
LRWRP Improvements in
Effluent Quality
LRWRP Effluent
2006 vs 2010
Concentration (mg/l)
Parameter 2006 2010*
TSS 25.7 5.1
TP 0.58 0.41
BOD** 46.8 2.8
TKN 16.2 3.7
NH3 10.6 1.8
NO2-NO3 0.9 5.6
*Based on average daily concentration Aug - Dec 2010
**2006 BOD is TBOD, 2010 BOD is CBOD
LRWRP Improvements in
Effluent Quality
LRWRP Effluent
2006 vs 2010
% Removal Efficiency
Parameter 2006 2010*
TSS 81.7 97.3
TP 84.5 91.3
BOD** 63.1 98.3
TKN 19.4 85.6
NH3 6.5 87.1 *Based on average daily concentration Aug - Dec 2010
**2006 BOD is TBOD, 2010 BOD uses TBOD for influent, CBOD for effluent (as per C of A)
LRWRP Improvements in
Effluent Quality
LRWRP Effluent
2006 vs 2010
Annual Loading (tonnes)
Parameter 2006 2010* Difference
TSS 1479 265 -1214
TP 33 21 -12
BOD** 2691 145 -2545
TKN 930 192 -738
NH3 609 93 -516
NO2- NO3 51 516 465
*Based on average daily concentration Aug - Dec 2010
**2006 BOD is TBOD, 2010 BOD is CBOD
Conclusions
• The BAF process itself is complex, while at the same
time, simple to operate. Plant operators do not have
to concern themselves with conventional activated
sludge process parameters such as sludge return
and wasting rates, sludge bulking, sludge washout,
etc.
• Attention to backwash is critical to performance of
BAF operation
• Changing BAF cell run time from fixed time to solids
loading based time resulting in significant
improvements in LRWRP effluent quality.
Questions
Paul Drca
Manager Environmental Quality
City of Windsor
519-253-7217