weftec presentation
TRANSCRIPT
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Marshalltown Wastewater Treatment Plant Phosphorus Removal Upgrade
Iowa State University
Steven Dickey
Dan Fleege
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Overview
• Marshalltown overview
• Problem statement and proposal
• Biowin modeling results
• Recommendation
• Questions
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Marshalltown, Iowa
Des Moines
Marshalltown
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Marshalltown Water Pollution Control Plant
• Began service in 1940
• Currently serves 26,000 people
• Plant divided into 2 processes– Mechanical plant to treat municipal waste
– Sequencing Batch Reactor to treat hog waste
• Effluent combined before UV disinfection
• Methane capture from stabilization basins
• Sludge land applied after stabilization
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Population Projection
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Mechanical Plant 1
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Mechanical Plant 2
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Mechanical Plant 3
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Sequencing Batch Reactor Plant
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Aging Infrastructure
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Problem Selection and Goals
1.0 mg/L effluent limit for total phosphorus
• Minimize construction by utilizing existing process equipment and configuration where possible
• Meet simulated permit limits for phosphorus
• Biowin v3 Model similar or better effluent
• Flexibility for plant operator
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SBR Plant Proposal
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SBR Plant
• Need– 1.6 MGD wastewater from a local hog processing plant
– Hog waste caused “foaming” in biological reactors
– High Organic Nitrogen Content: 200 mg/L
• Two Sequencing Batch Reactors– Operational in 1992– 2 MGD capacity
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Current SBR Configuration
Total Cycle Time: 360 min (6 hr)
Current 15 – 25% P removal
Stage 1Anaerobi
c120 min
Influent
Stage 2Aerobic120 min
Stage 3Settle60 min
Stage 4Decant60 min
Effluent
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SBR During Aeration
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SBR During Settle/Decant
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SBR During Settle/Decant
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SBR with BPR Process
• Anaerobic HRT: 1.5 ‐ 3 hr
• Aerobic HRT: 2 ‐ 4 hr
• Anoxic HRT: 1 ‐ 3 hr
• HRT range: 6.5 ‐ 12 hr
Table 8‐25 Metcalf & Eddy Wastewater Engineering
System Properties
• SRT range: 20 ‐ 40 days
• Settle/decant: 2 hr
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Proposed SBR Process
Cycle time: 540 min = 9 hr
HRT range: 6.5 – 12 hr
Stage 2Aerobic180 min
Stage 3Settle60 min
Effluent
Stage 3Anoxic 110 min
Stage 4Aerobic10 min
Stage 1Anaerobic 120 min
Influent Alum Addition
Stage 4Decant60 min
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Expected Performance
SBR
Flow (MGD)
VSS (mg/L)
TSS(mg/L)
BOD(mg/L)
TKN(mg/L)
NH3‐N(mg/L)
Total P(mg/L)
Influent 1.66 308 367 372 200 160 34
• Process cannot be simulated in Biowin
• BOD:P ratio 18:1
• Compare to Metcalf and Eddy ratios
• Expect 40 ‐ 60% P Removal
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Process Comparison
Existing SBR Process• 2 MGD capacity
• Note: 1.6 MGD average annual flow
• 5 Stages
• No anoxic phase
• Total cycle time: 6 hr
• No flow diversion to Mechanical Plant
• 10 – 25% P removal
Proposed SBR Process• 1.33 MGD capacity
• 33% flow diversion to Mechanical Plant
• 7 Stages
• Anoxic phase
• Plant operator flexibility– Max cycle time: 9 hr
– HRT range: 6.5 ‐ 9 hr
• 40 – 60% P removal
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Mechanical Plant Design
• Treats municipal waste
• Conventional activated sludge system divided into 3 separate plants
• 14 MG Equalization basin
• 14 MGD firm capacity for facility
• Modifications in 1965, 1972, 1982, 1987 and 2001
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Plant 1 and Plant 2 Identical
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Biological Process Plan View
• Tank 1‐4: 90ft x 19ft x 12ft (27.4m x 5.8m x 3.7m)
• Tank 5: 42 ft x 84 ft x 13 ft (12.8m x 25.6m x 4m)
• Total available volume: 128,000 ft³
FinalClarifier
Tank 1
Tank 2
Tank 3
Tank 4
Tank 5
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Influent
Influent
Influent
Influent
Plant 1 Flow Diagram
Return Activated Sludge
Influent
Aerobic
Aerobic
AerobicFinal
Clarifier
P
Effluent
Aerobic
Aerobic
Waste Activated Sludge
Flow Splitter
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Flow Distribution
Jetflow Injection Points
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Mechanical Plant 3
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Plant 3
• No modifications
• Still available for periods of high flow
• Available to reduce ammonia‐N levels if necessary
• Alum addition to treat Phosphorus
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BPR Systems Considered
• Anaerobic‐Anoxic‐Oxic (A2/O) • Virginia Initiative Plant (VIP)• University of Cape Town (UCT)• Bardenpho™ (5‐stage)
• Initial evaluation– Compare HRT to available tank volume– Eliminated UCT and Bardenpho ™ processes
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Preliminary VIP and A²/O Comparison
VIPBenefits
• Good nitrogen removal
• Low oxygen requirement
• Higher Phosphorus Removal
Drawbacks• Additional Recycle Line
required
• Higher HRT
A²/OBenefits
• Good nitrogen removal• Low oxygen removal• Lower HRT• Less Reactor volume
required• More process flexibility
Drawbacks• Less phosphorus removal
capability
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BOD:P Ratio Comparison
BPR Process BOD/P ratio
VIP 15‐20
A2/O 20‐25
BPR ProcessMax Month Flow BOD/P
Average Annual Flow BOD/P
Mechanical Influent 56 39
Mechanical with 33% SBR Influent
44 28
Table 8‐24 Metcalf & Eddy Wastewater Engineering
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VIP Process Outline
• Anaerobic HRT: 1 ‐ 2 hr
• Anoxic HRT: 1 ‐ 2 hr
• Aerobic HRT: 4 ‐ 6 hr
• HRT range: 6 ‐ 10 hr
Table 8‐25 Metcalf & Eddy Wastewater Engineering
• SRT range: 5 ‐ 10 days
• RAS: 80 ‐ 100%
• Anoxic recycle: 100 ‐ 200%
• Aerobic recycle: 100 ‐ 300%
System Properties
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VIP Process Plan View
Aerobic
Aerobic
FinalClarifier
Anoxic
Anaerobic
Flow Splitter
Aerobic
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Influent
VIP Flow Diagram
Return Activated Sludge
Aerobic
Aerobic
Aerobic FinalClarifier
P
Effluent
Anoxic
Anaerobic
Waste Activated Sludge
Flow Splitter
PP
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A2/O Process Outline
• Anaerobic HRT: 0.5 ‐ 1.5 hr
• Anoxic HRT: 0.5 ‐ 1 hr
• Aerobic HRT: 4 ‐ 8 hr
• HRT range: 5 ‐ 10.5 hr
Table 8‐25 Metcalf & Eddy Wastewater Engineering
• SRT range: 5 ‐ 25 days
• RAS: 25‐100%
• Internal Recycle: 100‐400%
System Properties
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A2/O Process Plan Layout
Aerobic
Aerobic
FinalClarifier
Anoxic
Anaerobic
Flow Splitter
Aerobic
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A²/O Flow Diagram
Influent
Return Activated Sludge
Aerobic
Aerobic
Aerobic FinalClarifier
P
Effluent
Anoxic
Anaerobic
Waste Activated Sludge
Flow Splitter
P
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BPR Model PerformanceMax Month Influent
Flow (MGD)
VSS (mg/L)
TSS(mg/L)
BOD(mg/L)
TKN(mg/L)
NH3‐N(mg/L)
Total P(mg/L)
Projected Mechanical
10.5 196 249 213 26 11 5.0
Max Month Effluent
VSS(mg/L)
TSS (mg/L)
BOD (mg/L)
COD (mg/L)
TKN (mg/L)
NH3‐N (mg/L)
Total P (mg/L)
VIP 5.1 7.6 3.6 34 2.9 0.93 0.56
A2/O 7.1 11 4.0 37 2.8 0.71 0.75
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BPR Model PerformanceAverage Annual Influent
Flow (MGD)
VSS (mg/L)
TSS(mg/L)
BOD(mg/L)
TKN(mg/L)
NH3‐N(mg/L)
Total P(mg/L)
Projected Mechanical
7.5 162 206 185 35 11 5.0
Average Annual Effluent
VSS(mg/L)
TSS (mg/L)
BOD (mg/L)
COD (mg/L)
TKN (mg/L)
NH3‐N (mg/L)
Total P (mg/L)
VIP 11 14 5.0 25 4.3 2.2 0.86
A2/O 5.3 7.5 3.7 30 3.5 0.87 0.79
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Equipment Requirements
VIP• 4 Additional recycle pumps
• Power: 450 HP
• 6 New Recycle Pipes
• 3000 Siemens DualAir®Diffusers
• 16 Hayward Gordon ST®Mixers
A2/O• 2 Additional recycle pumps
• Power: 400HP
• 2 New Recycle Pipes
• 3000 Siemens DualAir®Diffusers
• 16 Hayward Gordon ST®Mixers
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Chemical Treatment
• Alum addition considered for all plants
• A²/O required no alum addition for any model simulation
• VIP process required alum addition during winter months
• SBR requires a constant chemical addition
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Mechanical Plant: Current Flow
Average Annual FlowBiological Removal Percentage
Alum Dosage
ppd
1.5 2.0
0 399 532
10 359 478
20 319 425
30 279 372
40 239 319
50 199 266
60 159 213
70 120 159
80 80 106
90 40 53
100 0 0
Max Month FlowBiological Removal Percentage
Alum Dosage
ppd
1.5 2.0
0 530 707
10 477 636
20 424 565
30 371 495
40 318 424
50 265 353
60 212 283
70 159 212
80 106 141
90 53 71
100 0 0
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Mechanical Plant: Projected Flow
Average Annual FlowBiological Removal Percentage
Alum Dosage
ppd
1.5 2.0
0 480 640
10 432 576
20 384 512
30 336 448
40 288 384
50 240 320
60 192 256
70 144 192
80 96 128
90 48 64
100 0 0
Max Month FlowBiological Removal Percentage
Alum Dosage
ppd
1.5 2.0
0 626 835
10 563 751
20 501 668
30 438 584
40 376 501
50 313 417
60 250 334
70 188 250
80 125 167
90 63 83
100 0 0
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SBR Plant
Existing ProcessBiological Removal Percentage
Alum Dosage
ppd
1.5 2.0
0 727 970
10 655 873
20 582 776
30 509 679
40 436 582
50 364 485
60 291 388
70 218 291
80 145 194
90 73 97
100 0 0
Proposed ProcessBiological Removal Percentage
Alum Dosage
ppd
1.5 2.0
0 486 648
10 438 584
20 389 519
30 340 454
40 292 389
50 243 324
60 195 259
70 146 195
80 97 130
90 49 65
100 0 0
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Comparative AnalysisQualitative Cost Analysis
Initial Cost Operational
A2/O $$ $
VIP $$$ $$
Chemical $ $$$
Operational Performance
Flexibility Simplicity
A2/O ** **
VIP * *
Chemical *** ***
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Recommendation
Implement A²/O system
• Lowest relative cost
• Most operator flexibility
• Least construction required
• Capable of meeting effluent standard
• Better ammonia‐N removal in winter models
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Design Objective Achieved?
• Minimum construction– SBR system remain physically unaltered– Construction in areas of aging concrete– Only two new recycle pumps needed for the recommended A2/O design
• A2/O meets proposed permit limits• Flexibility for plant operator
– Recycle rates– SRT– SBR phases
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Special Thanks
• Lance Aldrich ‐ Design information
• Eric Evans ‐ Biown
• Kris Evans ‐Mentor
• Fred Beyer– Monthly monitoring reports
– Plant tours
– Design information
• IWPCA
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Questions?