Post on 15-Jul-2015
transcript
Marshalltown Wastewater Treatment Plant Phosphorus Removal Upgrade
Iowa State University
Steven Dickey
Dan Fleege
Overview
• Marshalltown overview
• Problem statement and proposal
• Biowin modeling results
• Recommendation
• Questions
Marshalltown, Iowa
Des Moines
Marshalltown
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
Population Projection
Mechanical Plant 1
Mechanical Plant 2
Mechanical Plant 3
Sequencing Batch Reactor Plant
Aging Infrastructure
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
SBR Plant Proposal
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
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
SBR During Aeration
SBR During Settle/Decant
SBR During Settle/Decant
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
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
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
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
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
Plant 1 and Plant 2 Identical
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
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
Flow Distribution
Jetflow Injection Points
Mechanical Plant 3
Plant 3
• No modifications
• Still available for periods of high flow
• Available to reduce ammonia‐N levels if necessary
• Alum addition to treat Phosphorus
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
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
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
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
VIP Process Plan View
Aerobic
Aerobic
FinalClarifier
Anoxic
Anaerobic
Flow Splitter
Aerobic
Influent
VIP Flow Diagram
Return Activated Sludge
Aerobic
Aerobic
Aerobic FinalClarifier
P
Effluent
Anoxic
Anaerobic
Waste Activated Sludge
Flow Splitter
PP
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
A2/O Process Plan Layout
Aerobic
Aerobic
FinalClarifier
Anoxic
Anaerobic
Flow Splitter
Aerobic
A²/O Flow Diagram
Influent
Return Activated Sludge
Aerobic
Aerobic
Aerobic FinalClarifier
P
Effluent
Anoxic
Anaerobic
Waste Activated Sludge
Flow Splitter
P
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
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
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
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
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
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
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
Comparative AnalysisQualitative Cost Analysis
Initial Cost Operational
A2/O $$ $
VIP $$$ $$
Chemical $ $$$
Operational Performance
Flexibility Simplicity
A2/O ** **
VIP * *
Chemical *** ***
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
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
Special Thanks
• Lance Aldrich ‐ Design information
• Eric Evans ‐ Biown
• Kris Evans ‐Mentor
• Fred Beyer– Monthly monitoring reports
– Plant tours
– Design information
• IWPCA
Questions?