NEWEA 2015 Annual Conference Session 16 Meeting North Attleborough, MA s 0.1 mg/l Phosphorus Limit with Bio-P and Cloth Media Filters January 27, 2015 Sue Guswa, P.E., Tighe & Bond Merrill Hastings, Town of North Attleborough
New NPDES Permit Requirements in 2007 Nitrogen Removal Total Nitrogen (TN) = 8 mg/l May-Oct Ammonia = 1 mg/l May-Oct Total Phosphorus Removal 0.1 mg/l Apr-Oct 1.0 mg/l Nov-Mar Future TN Limit? = 3-5 mg/l Ten Mile River flows to Narragansett Bay
Pre-Construction AO PROCESS North PUMPING PRIMARY CLARIFIERS SECONDARY CLARIFIERS DUAL MEDIA FILTERS/ DISINFECTION HEADWORKS ROTARY DRUM THICKENERS
WWTF Overview Pre-Construction Phosphorus Limits 1 mg/l (pre-2007) 0.4 mg/l seasonal (interim)» 2008 alum dosed split to primary and secondary clarifiers» 40-50 PPMV (gpd alum/mgd) A/O Process was used in combination with chemical addition for P removal 4.61 MGD Permit Flow Current flows near capacity Significant I/I Original Filters were a capacity bottleneck during high flow events
Selected Technologies for Nutrient Upgrades 5-Stage Bardenpho Biological phosphorus removal Biological nitrogen removal Tertiary Cloth Filters Selected after pilot testing Kruger Cloth Media Disc Filters 10 micron pore size Coagulation and flocculation» Polymer» Coagulant
Construction Overview $23 Million Upgrade Project for TN and TP 0% SRF Loan Construction Substantially Complete in October 2013
Post-Construction NEW 5-STAGE BARDENPHO North PUMPING SECONDARY CLARIFIERS NEW CLOTH FILTERS/ DISINFECTION PRIMARY CLARIFIERS HEADWORKS ROTARY DRUM THICKENERS NEW TERTIARY BUILDING WITH COAG/FLOC
Biological Nutrient Removal: Design Basis New Tanks Anaerobic Anoxic Aerobic Existing Tanks
New Biological Process Tanks
New Biological Process Tanks
New Chemical/Blower Building
Biological Nutrient Removal: Operational Flexibility Anaerobic Anoxic Aerobic Existing Tanks Offline To Operate as A 2 O Process to Meet Current Nitrogen Limits of 8 mg/l
Biological Nutrient Removal: Operational Flexibility Mixers in Last Aerobic Pass for Dissolved Oxygen Control Anaerobic Anoxic Aerobic
Biological Nutrient Removal: Operational Flexibility Anaerobic Anoxic Aerobic Ability to add Micro-C in Multiple Locations Ability to move insitu analyzers
Biological Nutrient Removal: Operational Flexibility Anaerobic Anoxic Aerobic Center Channel for Wet Weather Step Feed of Primary Effluent
New Tertiary Chemical System and Tanks
Filter Building Renovation
Cloth Filter Installation
Cloth Filter Installation
New Cloth Filters after Startup
Chemical Phosphorus Removal: Operational Flexibility Potential Addition Locations Primary clarifiers (unused) Secondary clarifiers Tertiary filters Choice of Chemicals Alum Ferric chloride Polymer Sodium hydroxide
Operating Philosophy Keep the bugs happy Keep a blanket in primary clarifiers VFAs Use as little chemical as possible No chemical addition to tertiary system Alum added to secondary clarifiers» Dose = 20-25 PPMV(gpd solution/mgd) typical during dry weather Micro C added to anaerobic zone» Dose = varied this year 7-14 gpd solution/mgd
Current Operations MLSS 4,000 mg/l Aerobic SRT 10-12 days RAS 50-60% Influent Flow Constant RAS return Need blankets for sludge wasting Mixed Liquor Recycle 3x Influent Flow F/M 0.1
2014 Performance Total Phosphorus Grease in Influent
What Caused the Phosphorus to Increase in August? Turned off Supplemental Carbon Grease in Influent
Anaerobic Zone Phosphorus Release
Conclusions A combination of EBPR, coagulant addition, and tertiary treatment with cloth filters can meet the limit of 0.1 mg/l TP at the WWTF EBPR is saving money on chemicals Optimization is an on-going project with focus on: Carbon management Coagulant management Wet weather management Project Success = close involvement of WWTF staff from beginning of the project
Discussion Sue Guswa seguswa@tighebond.com Merrill Hastings mhastings@nattleboro.com