iowa city nutrient reduction study...•aww/mww flows of 13/19 mgd were significantly lower than the...
TRANSCRIPT
Iowa City Nutrient Reduction Study
IAWEA 2016 Annual Conference
Jay Brady, P.E.
June 8, 2016
Presentation Overview
• Plant Background
• Process Configurations
• Study Drivers
• Flows and Loadings
• Performance – Nitrogen
• Performance – Phosphorus
• Potential NPDES Permit Limits
• Supplemental Technologies
• Observations
IC South WWTP The culmination of a 40 year vision of
migrating wastewater treatment out of the city
Chuck Meyer, P.E. Chief Civil Engineer Stanley Consultants
Chuck Schmadeke, P.E. Public Works Director City of Iowa City
NORTH WWTP
SOUTH WWTP
Iowa River
South Plant ~ 15 years of conception, planning, and study work Constructed 1990 5 mgd Capacity BOD Removal, Surface Aerators Serves SE Iowa City
NORTH WWTP
SOUTH WWTP
Iowa River
Napolean Park Lift Station
Connector Infrastructure Constructed in 1996-1999 84/96 inch trunk sewers Napolean Park Lift Station
South Plant – 2003
7
2003 MLE Process – Nitrification & Denitrification
North Plant – 2008 Flood
NORTH WWTP
SOUTH WWTP
Iowa River
Napolean Park Lift Station
South Plant Expanded in 2012-14 to 24 mgd and Significant Organic Load Capacity Nutrient Reduction – MLE/A2O Processes $46 million Investment N. Plant Closed and Decommissioned 2015
Design Flows and Loads
S. Plant N & S Plants 2025
Flow (mgd) 10/25/60 18.6, 33.1, 45 24, 43/30, 62
BOD5 (lb/d) 16,554 21,643 32,658
TSS (lb/d) 17,000 22,075 34,385
TKN (lb/d) 2,940 4,665 6,311
Plant Process Configurations - MLE
The BAR Process
13
Bioaugmentation
R = Reaeration or Regeneration
Plant Process Configurations – A2O
Study Drivers
• Iowa Nutrient Reduction Policy (INRP)
• NPDES Permit Requirements:
– Plant Optimization Study
– Evaluation of Possible Upgrade Requirements
– 66% TN Reduction, 75% TP Reduction or
10/1 mg/L effluent values
• Focus: Operational
Adjustments/Optimization for Nutrients
Flows and Loads
0
5
10
15
20
25
30
35
40
45
ADW ADF AWW MWW
Flow, mgd
Flows and Loads
Average Max Month Max Day 0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000CBOD5, lbd
Flows and Loads
Average Max Month Max Day 0
10,000
20,000
30,000
40,000
50,000
60,000
70,000TSS, lbd
Flows and Loads
Average Max Month Max Day 0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000TKN, lbd
Flows and Loads
Average Max Month Max Day 0
200
400
600
800
1,000
1,200
1,400TP, lbd
Flows and Loads
Flows and Loads
Optimization Trial
• North Plant shutdown February 7, 2014
• MLE Mode February – December 23, 2014
• A2O Mode December 23, 2014 – March 31, 2016
MLE Operational Performance - TN
MLE Operational Performance - TP
A2O Operational Performance - TN
A2O Operational Performance - TP
Estimated Nutrient Mass Limits
• Assumes log distribution of data
• 99th percentile TNe, TPe
• Compute mass limits based on Design AWW
Parameter Allowable Average Mass Loading, lb/d
At Max Month design flow, mg/L
At Design ADF, mg/L
TN 2,148 10.6 17.8
TP 319 1.6 2.6
Must operate Nutrient Reduction Systems
Supplementary Technologies
• Increased Internal Mixed Liquor Recycle (IMLR)
• Primary Sludge Fermenter
• Ferric Chloride Addition
Supplementary Technologies - IMLR
• 2012 design re-used some original piping for the
the IMLR resulting in IMLR capacity of 25 mgd or
~2:1 ratio to influent Q for average flows at the
2025 design flow. A IMLR of 3 or 4:1 is ideal for
optimal TN reduction.
• Additional piping and changes to the IMLR
pumping would be required to optimize the
IMLR:Qo Ratio
Supplementary Technologies - Fermenter
• Volatile Fatty Acids (VFAs) aka soluble
biodegradable chemical oxygen demand are
necessary at the right ratios for both TN and TP
reduction.
• Primary clarifier fermenter is one way of producing
and providing a more consistent source of VFAs
for BNR.
• Need for a fermenter would be due to changing
influent wastewater conditions
Supplementary Technologies – FeCl3
• Option to improve MLE TP reduction by addition at
aeration basin discharge or to BFP operation.
• Also could be needed for A2O if wastewater
conditions change
Supplementary Technologies – Costs
Technology 20-Yr PW Cost
IMLR Increase $2,500,000
Fermenter $5,000,000
Ferric System $3,000,000
Observations
BNR Favorable Influent Characteristics
• Higher influent cBOD5 loadings provide more
organic carbon increasing C:TKN and C:TP ratios.
• AWW/MWW flows of 13/19 mgd were significantly
lower than the historical AWW/MWW flows of
18/29 mgd
• Minimum monthly influent temperature of 15oC is 3
degrees warmer than the basis of design favoring
nitrification kinetics and BNR performance.
• Future conditions could reduce the performance of
the nutrient removal systems.
Observations
A2O Mode
• Achieved TN Reduction of 74%
• Achieved TP Reduction of 82%
• Inconsistent Enhanced Biological Phosphorus
Removal (EBPR) aka ‘Bio-P’ observed and as
predicted by planning/design modeling
• Anaerobic selector PO4-P release suggests some
EBPR activity but not substantial
• A2O mode appears capable to meeting reduction
requirements under current wastewater conditions
Observations
MLE Mode
• Achieved TN Reduction of 75%
• Achieved TP Reduction of 72% (slightly below
target)
• Additional MLE operational trialing recommended
with increased IMLR and addition of ferric chloride
to belt filter press sludge feed
Observations
Investment in additional nutrient reduction
technologies is not warranted at this time.
Future investment may be necessary if BNR
performance declines due to changing wastewater
conditions or increased loadings
Acknowledgements
WWTP Staff – Dave Elias (retired), Tim Wilkey, Roger Overton, Al Figueroa, Steve Flake, Laboratory Staff Don Esping and Lloyd Winchell, BC Process Team
Discussion