NEWEA 2015 Annual Conference Session 16

Transcription

1 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

2 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

3 Pre-Construction AO PROCESS North PUMPING PRIMARY CLARIFIERS SECONDARY CLARIFIERS DUAL MEDIA FILTERS/ DISINFECTION HEADWORKS ROTARY DRUM THICKENERS

4 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» 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

5 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

6 Construction Overview $23 Million Upgrade Project for TN and TP 0% SRF Loan Construction Substantially Complete in October 2013

7 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

8 Biological Nutrient Removal: Design Basis New Tanks Anaerobic Anoxic Aerobic Existing Tanks

9 New Biological Process Tanks

10 New Biological Process Tanks

11 New Chemical/Blower Building

12 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

13 Biological Nutrient Removal: Operational Flexibility Mixers in Last Aerobic Pass for Dissolved Oxygen Control Anaerobic Anoxic Aerobic

14 Biological Nutrient Removal: Operational Flexibility Anaerobic Anoxic Aerobic Ability to add Micro-C in Multiple Locations Ability to move insitu analyzers

15 Biological Nutrient Removal: Operational Flexibility Anaerobic Anoxic Aerobic Center Channel for Wet Weather Step Feed of Primary Effluent

16 New Tertiary Chemical System and Tanks

17 Filter Building Renovation

18 Cloth Filter Installation

19 Cloth Filter Installation

20 New Cloth Filters after Startup

21 Chemical Phosphorus Removal: Operational Flexibility Potential Addition Locations Primary clarifiers (unused) Secondary clarifiers Tertiary filters Choice of Chemicals Alum Ferric chloride Polymer Sodium hydroxide

22 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 = PPMV(gpd solution/mgd) typical during dry weather Micro C added to anaerobic zone» Dose = varied this year 7-14 gpd solution/mgd

23 Current Operations MLSS 4,000 mg/l Aerobic SRT days RAS 50-60% Influent Flow Constant RAS return Need blankets for sludge wasting Mixed Liquor Recycle 3x Influent Flow F/M 0.1

24 2014 Performance Total Phosphorus Grease in Influent

25 What Caused the Phosphorus to Increase in August? Turned off Supplemental Carbon Grease in Influent

26 Anaerobic Zone Phosphorus Release

27 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

28 Discussion Sue Guswa Merrill Hastings