Using On-line Monitoring as an Effective Tool for Wastewater Treatment Process Optimization

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Using On-line Monitoring as an Effective Tool for
Wastewater Treatment Process Optimization

• Ontario WEA
• Wastewater Instrumentation
• Data Management Seminar
• Milton, ONMay 30, 2013
• Wei Zhang, ASA Analytics, Inc.

www.asaAnalytics.com
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Outline

• Wastewater Water Treatment Process Optimization
  Issues
• Applications in Single Unit BNR process
• Nitrification
• Phosphorus Removal
• Case Histories
• Consideration of on-line process analyzer
  selection

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Why On-line Now?

• Regulations toward TN/TP
• Technology is more mature
• More sophisticated treatment processes
• Direct Benefit Energy Saving, Chemical Saving

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Why Monitor Nutrients?

• If You Want to Control Process Chemistry,
  Measure Process Chemistry

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Challenges for Todays BNR/ENR

• Facing total nitrogen and total phosphorus
  limitation
• To provide a fast-response, flexible and reliable
  system capable of handling highly variable
  influent nutrient loads
• Energy Saving and chemical saving
• To minimize maintenance labor

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Nitrification

• A aerobic biological process to convert ammonia
  nitrogen to nitrate nitrogen, reducing
  nitrification and toxicity caused by ammonia.
• Typical treatment process
• Single Stage Nitrification
• Multi-Stage Nitrification
• Process consumes oxygen and alkalinity (reduce
  pH)

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Single-stage Nitrification

• Influent Ammonia lt 30 mg/l
• On-line monitoring issue pH, alkalinity, NH3,
  NO2, NO3 and DO, etc.

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Two-stage Nitrification

• Influent Ammonia 3050 mg/l
• On-line monitoring issue pH, alkalinity, NH3,
  NO2, NO3 and DO, etc.

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Process Control Indicators

• DO
• 4.6 lbs O2/lb NH3-N removal
• Maintain 12 mg/l in the aeration basin
• Alkalinity
• 7.2 lbs Alkalinity destroyed/lb NH3-N removal
• Maintain 5080 mg/l Alkalinity in the aeration
  basin
• SRT (RAS Ratio and Temperature)
• Nitrogen profile through treatment train
  (increase nitrite as first indication inhibitory
  of Nitrobacter organisms, or incomplete
  nitrification)

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Nitrogen Transformations

• Decline in ammonia concentration
• Increase, then decline in nitrite concentration
• Increase of nitrate to stable maximum
• Only AFTER this is any surplus DO produced

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Ask Question about Nitrification Process

• How much oxygen is enough?
• How much alkalinity is enough?

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Nitrification Energy Saving

• City of Orlando WWTP (WEFTEC Proceeding 1999)
• 12 mgd plant with activated sludge process
• Using ChemScan analyzer generated nitrogen
  profile at each aeration basin
• Set target setpoint/level of ammonia and nitrate
  in each tank
• Motorized air valves and air blowers in each tank
  are modulated to maintain the selected nitrogen
  level.
• When ammonia level is higher than setpoint, air
  valves open to increase nitrification.
  Conversely, nitrate level higher than setpoint,
  air valve reducing air.
• If adjustment of air valve cant maintain desired
  nitrogen level, further blower adjustment kick-in
• ChemScan analyzer is the core part of the process
  control

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Phosphorus Removal

• TP gt 1.0 mg/L
• biological phosphorus removal
• TP lt 1.0 mg/L
• chemical precipitation, or
• combination of chemical biological

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Chemical Phosphorus Removal

• Aluminum
• Al2(SO4)3.(14H2O) 2H2PO4- 4HCO3-
• 2AlPO4 4CO2 3SO42- 18H2O
• Ferric Iron
• FeCl3.(6H2O) 2H2PO4- 2HCO3-
• FePO4 3Cl- 2CO2 8H2O
• Side Reaction
• Fe3 OH- ? Fe(OH)3
• Ferric (or aluminum) hydroxide is formed, loss of
  alkalinity

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Right Amount of Chemicals

• US EPA Nutrient Control Design Manual (2009)
• Alum to P molar ratio
• 1.38 1 for 75 removal
• 1.72 1 for 85 removal
• 2.3 1 for 95 removal
• Iron to P molar ratio
• 1 1 is required with a supplemental amount of
  10 mg/l iron added to satisfy the formation of
  hydroxide.

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Common Practices

• The following methods are often used for
  determination of right amount chemicals
• Jar Testing or Bench Testing
• Historical Trending
• Third Party Laboratory Analysis
• Plants Lab Analysis
• These methods are often labor and time consuming.

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Right Solution

• Online Phosphorus Analyzer
• Real time
• Continuous monitoring
• SCADA-linked for automatic dosing control
• Flexible for feed forward or feed back
  control
• Key Chemical Saving

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Chemical Injection Locations

• Primary Clarification
• Popular location for reducing P loading
• Feed forward control loop
• A precious control is needed to avoid nutrient
  deficiency to biological process
• Might generate more primary sludge to handle
• Monitor locations raw influent and primary
  clarifier effluent
• End of Aeration Basin
• Another popular location for polishing
• Chemical usage are more efficient
• Feed back control loop
• Monitor location secondary clarifier effluent or
  final effluent
• Both locations

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• S. Arant, Donohue Associates, Inc.

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Installations Case Histories

• Kiel, Wisconsin
• 0.9 mgd Activated sludge process
• Phosphorus permit limit 1.0 mg/l
• A cheese factory is the major contribution source
• Online analyzer data feed back to SCADA for
  ferrous sulfate dosing
• 20 chemical expense saving

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Installations Case Histories

• New London, Wisconsin
• 2 mgd Activated sludge process plant
• Phosphorus permit limit 1.0 mg/l
• Online analyzer data feed back to SCADA for
  ferric chloride dosing control
• 900 per month chemical expense saving

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Installations Case Histories

• Sheboygan, Wisconsin
• WWTP servicing population of 50,000
• Current phosphorus limit is 1.0 mg/l
• Future phosphorus limit will be 0.05 mg/l
• Ferric chloride spending 160,000 annual with
  current limits
• First online phosphate analyzer installed in 2010
• Second online phosphate analyzer just installed
• data feed back to SCADA for ferric chloride
  dosing control

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Installations Case Histories

• Hite Creek, Kentucky
• Unpredicted phosphorus load from nearby
  industrial source
• Using Alum solution for phosphorus precipitation
• Plant is able to set up improved alum feed rate
  for different days of the week to match the
  expected P load based, using 4 months data
  collected from online analyzer
• Daily alum dosage reduced from 200 gallon/day to
  100 gallon/day

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Installations Case Histories

• Waupun, WI
• Ferric to Primary only total sludge 5,560
  lbs/d, total ferric 190 gal/d

• S. Arant, Donohue Associates, Inc.

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Installations Case Histories

• Waupun, WI
• Multiple Point total sludge 5,160 lbs/d, total
  ferric 120 gal/d

• S. Arant, Donohue Associates, Inc.

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• S. Arant, Donohue Associates, Inc.

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• S. Arant, Donohue Associates, Inc.

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Using Ortho-phosphate to Control Ferric Feed
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Advanced BNR/ENR Processes

• Treatment plant facing discharge limitation on
  both total N or total P
• Process involve more than one individual BNR
  process

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BNR Process Schematic

• Nitrification/Denitrification with chemical
  phosphorus removal. No supplemental carbon
• Some simultaneous nitrification/denitrification
  (SND)

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Supplemental Carbon Feed Control

• Chemical feed can be 2030 of entire operating
  cost
• Flow pace is still used in many plants
• Manual control based on grab sample is imprecise
  and time consuming
• Manual control can lead to unnecessary chemical
  expense and extra BOD discharge
• Underfeed supplemental carbon incomplete
  denitrification
• Chemical feed control scheme using nutrient
  parameters are installed in many plants

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BNR Process Schematic

• Post denitrification bio-filter
• Chemical feed control scheme using nutrient
  parameter is well developed

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BNR Process Schematic

• Modified Ludzack Ettinger (MLE) with supplemental
  carbon

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BNR Process Schematic

• Bardenpho Process with post denitrification
  filter
• Two on-line nutrient analyzers

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Denitrification Filter Using On-Line Nutrients
Signal in Control Scheme (1)
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Denitrification Filter Using On-Line Nutrients
Signal in Control Scheme (2)
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An On-line Nutrient Monitoring Chart
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Case Study Bonnybrook WWTP Calgary, Alberta
Orthophosphate 4 Month Average Error 3.0
Ammonia 4 Month Average Error 3.0
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Case Study Bonnybrook WWTP Calgary, Alberta
Nitrate 4 Month Average Error 1.7
TSS 4 Month Average Error 3.3
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On-line Analyzer Selection

• Technologies
• Ion specific electrode
• Spectrophotometers
• Arrangement/configuration
• Single parameter vs. multiple parameters
• Single sample location vs. Centralized multiple
  sample lines
• Look at the hidden cost
• Proprietary reagents vs. generic reagents
• some analyzers bundles with service contract

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Summary

• If You Want to Control Process Chemistry, Measure
  Process Chemistry
• Proven technology is available that can provide
  reliable automatic chemical analysis
• Energy saving and Chemical saving
• Multi-parameter multi-sample line analyzer system
  provides online nutrient analysis required for
  BNR monitoring and control

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Contact

• Wei Zhang
• ASA Analytics, Inc.
• Waukesha, Wisconsin
• [phone]
• wei_at_chemscan.com
• Local Contact
• Metcon Sales Engineering, Ltd.
• Concord, ON
• [phone]

www.asaAnalytics.com