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
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 m 3 /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 m 3 /d to 272,800 m 3 /d and the construction of a BAF for secondary treatment with a rated capacity of 218,000 m 3 /d. The plant is designed to handle a peak flow of two times the rated capacity.
The LRWRP - Upgrade & Other Work included: Expansion 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 NH 3 -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 * CBOD 5 15.0 TSS 15.0 TP 0.5 Un-ionized NH 3 0.1 Acute Lethality to Rainbow Non acutely lethal Trout & Daphnia Magna 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
BOD (mg/l) 200 BOD Removal Within 3 Weeks of Startup BAF Startup & Challenges Encountered 180 80% BOD removal within 3 weeks of startup 160 Steady nitrification by June 2008 140 Challenges 120 100 80 Foaming 60 Soluble phosphorous deficiency 40 TSS compliance 20 0 BAF cell loading Media loss Primary effluent & backwash supply tank screening Backwash cycle time 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 H 3 PO 4 supplementation H 3 PO 4 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.
Solution Data Constants TSS Compliance TSS 1.26 30 day maximum loading in - kg TSS/m3d Monthly strong backwashing frequency was doubled and spread out through the month TKN 0.59 31 day maximum loading in - kg TKN/m3d Cell Area 144 m2 Media Depth 3.9 m Media Volum e 561.6 m 3 Backwash procedure was revised for efficiency Hours/day 24 Max Max Max Monitoring and Primary maintaining Primary Duration primary Duration clarifier Filtration surface overflow Avg.# rate of Effluent Effluent (SOR) - target of of TSS 20 m/h of TKN SOR Time Filtration Time (h, 3 day running avg) Avg. Daily Flow Cells in TSS TKN Cycle Cycle (h, min of (MLD/day) An additional Filtration (mgl chemical -1 ) (mglfeed -1 ) line (h) for alum (h) was TSS/TKN) 147.0 8.0 39.0 10.0 23.7 43.3 23.7 24 125.0 extended 6.8 to the 39.0backwash 10.0 waste 23.7 discharge 43.3 pipe 23.7 (just 24 132.7 prior to 7.2 primary 37.0 treatment) 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 Cell cycle 6.8 time 60.0 is set 20.0 based on 17.9BAF 25.2 media loading 17.9 18 124.5 6.9 60.0 34.0 15.7 13.0 13.0 15 125.0 criteria 7.0 and primary 10.0 effluent 34.0 quality 95.1 13.1 13.1 15
TSS (mg/l) 2010 LRWRP BAF TSS 120 100 BAF Influent BAF Effluent 80 60 40 20 0 01/01/2010 01/04/2010 01/07/2010 01/10/2010 01/01/2011 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