WEAO2012 Technical Conference
USING ONLINE ANALYZER FOR OPTIMIZING
CHEMICAL PHOSPHORUS REMOVAL PROCESS
IN MUNICIPAL WASTEWATER TREATMENT
Ottawa, Ontario, Canada
April 24, 2012
Wei Zhang, David Roskowic
ASA Analytics, Inc.
wei@chemscan.com
(262) 391-8306
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
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
Statement of the Problem
 TP > 1.0 mg/L
 biological phosphorus removal
 TP < 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
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
Right Amount Chemicals?
 US EPA Nutrient Control Design Manual (2009)

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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.
“Common Practices”
 The following methods are often used for
determination of “right amount” chemicals

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Jar Testing or Bench Testing
Historical Trending
Third Party Laboratory Analysis
Plant’s Lab Analysis
 These methods are often labor and time
consuming.
A Proposed Solution
 Online Phosphorus Analyzer

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Real time
Continuous monitoring
SCADA-linked for automatic dosing control
Flexible for “feed forward” or “feed back”
control
 Key – Chemical Saving
Ortho-P vs. Total-P
 Total Phosphorus


Organic portion
inorganic portion
 Why measure ortho-P in process control

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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
Online Phosphorus Analyzer
 Total Phosphorus Analyzer
 Ortho-Phosphate Analyzer
 Chemical dosing control –

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Ortho-phosphate analyzer
Spectrometry with wet chemistry
Ortho-P reacts with ammonium molybdate to form
vanadomolybdophposphoric acid (yellow color)
Blue Method
AppliedSpectrometry
Associates, Inc.
Installations & Case Histories
 Kiel, Wisconsin
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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
Installations & Case Histories
 New London, Wisconsin
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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
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
AppliedSpectrometry
Associates, Inc.
Installations & Case Histories
 Hite Creek, Kentucky
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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
Installations & Case Histories
 Waupun, Wisconsin

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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.
Installations & Case Histories
 Hagerstown, Maryland
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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
Phosphorus Analyzer Selection
 Check References
 Interference compensation
 Self-cleaning and self-zeroing
 Sample handling
 Maintenance requirement
 Overall cost of ownership
Conclusion
 Meeting tightening discharge limitation
 Quick response to concentration changes
 Chemical cost savings
 Reduce of maintenance burden