WEAO2012 Technical Conference

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WEAO2012 Technical Conference

• USING ONLINE ANALYZER FOR OPTIMIZING CHEMICAL
  PHOSPHORUS REMOVAL PROCESSIN MUNICIPAL
  WASTEWATER TREATMENT
• Ottawa, Ontario, Canada
• April 24, 2012
• Wei Zhang, David Roskowic
• ASA Analytics, Inc.
• wei_at_chemscan.com
• [phone]

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Overview

• Phosphorus is the target nutrient in Great Lake
  region
• 1976 Ontario MOE a six-year study called for
  installation of phosphorus removal facilities
• 1978 The Great Lake Water Quality Agreement (US
  and Canada) put phosphorus removal as primary
  concern of nutrient removal.
• 2010 Lake Simcoe phosphorus removal review report
  (XCG Consultant), evaluated 14 WWTPs discharge to
  the watershed
• Current discharge permit 0.1 0.5 mg/l as TP,
  some are even lower

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Presentation Focus

• Overview of chemical phosphorus removal
  fundamentals from operational cost perspective
• With primary focus on the rule of online analyzer
  nutrient analyzer plays in chemical phosphorus
  removal
• Case histories

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Statement of the Problem

• TP gt 1.0 mg/L
• biological phosphorus removal
• TP lt 1.0 mg/L
• chemical precipitation, or
• combination of chemical biological
• Existing Treatment might not designed for
  phosphorus removal
• Flow pacing or set at a constant flow rate to
  meet the worst-case scenario

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Chemical P Removal Basics

• Aluminum or iron salts are used for phosphorus
  chemical precipitation
• Al2(SO4)3.(14H2O) 2H2PO4- 4HCO3-
• 2AlPO4 4CO2 3SO42- 18H2O
• FeCl3.(6H2O) 2H2PO4- 2HCO3-
• FePO4 3Cl- 2CO2 8H2O

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Right Amount 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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A Proposed 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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Ortho-P vs. Total-P

• Total Phosphorus
• Organic portion
• inorganic portion
• Why measure ortho-P in process control
• Ortho-P is dissolved portion
• Biological process converting P from un-dissolved
  form to dissolved form
• Chemical precipitation removes Ortho-P
• Relationship between ortho-P and Total-P
• Clarifier or filtration performance is important

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Online Phosphorus Analyzer

• Total Phosphorus Analyzer
• Ortho-Phosphate Analyzer
• Chemical dosing control
• Ortho-phosphate analyzer
• Spectrometry with wet chemistry
• Ortho-P reacts with ammonium molybdate to form
  vanadomolybdophposphoric acid (yellow color)
• Blue Method

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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, Wisconsin
• Case study by Steven Arant of Donohue Associates
  (now AECOM)
• Study conclusion
• Comparing single point chemical dosing to
  multiple points chemical dosing, the later save
  chemicals and produces less sludge.

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Installations Case Histories

• Hagerstown, Maryland
• A demo project funded by the State of Maryland
• Discharge limit TN 3.0 mg/l, TP 0.3 mg/l
• To demonstrate the conventional technologies can
  achieve the goal
• Tertiary biological denitrification filter for N
  and chemical P removal
• Full scale installation in 2010 based on the
  result of the successful demo

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Phosphorus Analyzer Selection

• Check References
• Interference compensation
• Self-cleaning and self-zeroing
• Sample handling
• Maintenance requirement
• Overall cost of ownership

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Conclusion

• Meeting tightening discharge limitation
• Quick response to concentration changes
• Chemical cost savings
• Reduce of maintenance burden