Patrick Rein Richard Armstrong

1
Patrick ReinRichard Armstrong

• Enhanced Biological Phosphorus Removal
• at the
• Fergus Falls WWTP

2
OVERVIEW

• Background/ Review Theory
• Operations Review
• Some parameters to keep an eye on
• P in MLSS Test
• How do we know if we are getting EBPR?
• How we are doing at Fergus Falls
• Plant configuration
• Results
• Shock load test
• Conclusions

3
Background

• EBPR (enhanced biological phosphorus removal) is
  not new!!!
• Stress Organisms-anaerobic / aerobic in presence
  of a carbon source (BOD).
• Timmerman 1979, Krichten et. al., 1978 Refling et
  al 1977 and others 1974
• Old Patented Processes
• A/O process
• Bardenpho process.

4
EBPR Just Makes Good Sense

• Reduction / Elimination of Chemicals
• Reduced Sludge Production (lower growth)
• Control of Filaments
• Improved SVI
• Reduced Operating Costs

5
EBPR Defined

• When organisms store more phosphorus than their
  normal requirements
• What are normal requirements
• Bugs are 2 phosphorus by weight
• Will remove 20 of P coming out of primary
• This is due to normal growth!!!
• With EBPR
• Bugs can be over 15 phosphorus by weight
• Can remove over 60 removal of P coming out of
  primary

6
Review of EBPR Theory

• The Anaerobic Zone
• Sufficient Biomass
• MCRT gt 10
• No Oxygen or Nitrate
• Store Food
• Food VFAs
• Energy for Storage comes from P Release

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Review of EBPR Theory

• The Aerobic Zone
• Bugs
• Use D.O.
• Consume Stored Food (VFAs)
• Generate Energy for P Uptake
• Cell Growth
• P Uptake (recharge the battery)

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Operations Review

• What operating parameters must I be concerned
  about?

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OPERATIONS REVIEW

• What we have observed that affects EBPR
  performance the most
• Return Flow Rate-Nitrate and DO
• Secondary P release
• Wastewater Characteristics Entering Anaerobic
• BOD/P

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Secondary Release of P

• THESE ARE NOT GOOD RELEASES!!!
• Anaerobic P Release
• P release without uptake of VFAs
• Control time in zone (we have 2 hr HRT)
• Aerobic P Release
• Long HRT could result in P release due to
  endogenous destruction (we have 5 hr HRT)

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The Eff. Primary Clarifier (PC) RatioBOD/P

• You Dont even need EBPR. Still get 20 P
  removal. Eff. P maybe lt1 due to normal growth.
• Now you need EBPR (going beyond normal growth p
  uptake)
• Youll get even better EBPR but will not meet
  limit of 1.0 mg/L

• 100/1 100
• 100/5 20
• 100/10 10

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As Effluent PC Ratio Goes Down

• Anaerobic Zone
• Small change in COD taken up
• Large change in P Release
• In other words, P release per unit of COD
  increases
• (Shock increase in P Load)
• Aerobic Zone
• More food more energy for P uptake
• Phosphorus uptake increase
• P in the MLVSS increases (as high as 18)
• More Anaerobic P Release More Aerobic P
  Uptake

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Eff. PC Ratio Affects Release and Uptake
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What is the Best Method to Measure EBPR ?

• PHOSPHORUS in MLVSS
• Do the bugs contain more than the normal
  requirement of 2-3?

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P in MLVSS Test

• Hach Test N Tube Method 8190
• Run Total P on Mixed Liquor (MLSS-TP)
• Run Effluent Total P (Eff-TP)
• filtered MLSS sample
• typically we just use composite Eff. P value
• represents soluble orthophosphate
• P in Bugs MLSS-TP Eff-TP
• P in MLVSS (P in Bugs) / (MLVSS) X 100

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Bio-P Testing Examples
19
A Comparison
CONFIGURED FOR BIO P ( OAK VALLEY
BODP17/EFF P14--Fergus Falls BODP37/ EFF P
lt1)
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Is the Process Working?

• How do you know if you are getting EBPR?
• If Effluent P lt 1.0 mg/L
• Maybecould be because Influent PC ratio is very
  high
• If Phosphorus in MLSS, RAS or WAS
• 3 to 5 (YOU ARE GETTING EBPR)
• BUT still Eff. P maybe gt 1.0 mg/L
• Due to operations (i.e. high Eff. TSS or
  secondary p releases)

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How can we get Effluent P lt 1.0 mg/L

• For Typical Domestic WW
• Entering the Anaerobic Zone
• BOD5/P of at least 20 (COD/P40) (higher the
  better)
• 20 mg/L COD to remove 1 mg/L Phosphorus
• Remember Domestic WW
• Normally P Limited (4-6 P for bugs)
• Control other Parameters Mentioned Earlier

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Removal at Fergus Falls
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Fergus Falls WWTP

• 2.81 MGD 1988 Extended aeration Plant
• Design
• 2 Aeration Basins 12 hours
• Chemical Phosphorus Removal
• Design Included Operational Options
• (1)Contact Stabilization, (2) Parallel Flow, and
  (3) Plug Flow

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1999 Operation Changes

• Reduced Aeration Volume (1/2)
• Reduced RAS (500 gpm to 240 gpm)
• Turned Air Off in Mix Well
• Tried One Primary Clarifier (abandoned)

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ANAEROBIC
AEROBIC
AEROBIC
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Process Schematic
Q QR
Q QR
Q Influent
Q QR
Q Effluent
Mix Well
QR Recycle
QR
QR
No Air, Mix Zone 1 0.183 MG
Air Zone 2 0.183 MG
Air Zone 3 0.183 MG
Settle/Decant Zone 4 0.596 MG
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Zone Times

• Total HRT 17.2 hrs
• No Air 2.74 hours
• Air 5.49 hours
• Settle 8.94 hours
• Graph Shows Percentages of Total HRT

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RESULTS

• How have we done at Fergus Falls?

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FF Primary Clarifier Effluent

• BOD 133 mg/L
• P 3.6 mg/L (40 Removal)
• BOD/P (entering the anaerobic zone)
• BOD/P 37.0 mg/L
• So it should work!
• Only needs an anaerobic zone

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Operating Conditions

• Anaerobic Zone
• ORP
• IN -25
• Out -240
• BOD/P
• In 37
• COD (soluble)
• In 130 mg/L
• Out 13 mg/L

• Aeration Plug Flow (2) Channels
• DO 2.0 mg/L _at_ end
• MLSS 5,000 or gt
• NO3 lt 6 8 mg/L
• ORP 100

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BOD Variability
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Phosphorus Variability
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P in MLVSS

• 2004 Averages
• Influent P 6.5
• Effluent P 0.6
• P/MLVSS 4.55
• 2003
• P/MLVSS 5.29
• 2002
• P/MLVSS 4.83

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Current Phosphorus Balance--no chemical being
added!
Influent Q 1.5 MGD BOD 221 mg/L BOD 2764
lb/day P 6.0 mg/L P 75 lb/day
Effluent Q 1.5 MGD BOD 3 mg/L P 0.6 mg/L P
8.0 lb/day
BOD 133 mg/L BOD 1,664 lb/day P 4.4 mg/L P
45 lb/day
Primary Clarifier
Secondary Clarifier
Activated Sludge Tank
Primary Sludge Q 8,000 gpd TS 5 P 30 lb/day
RAS
WAS 832 lb/day P 4.55 P 37 lb/day
P/VS 4.55
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Effluent P Results 2002-2004

• We always meet Total Phosphorus limit of lt1.0
  with some chemical addition
• Typically run without any chemical when not
  dewatering (5 months/year)
• P in MLSS say we are getting EBPR even though
  we use chemical

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Shock Load Test 2004

• From Biosolids Dewatering
• Influent P 10 mg/L (was running 6.5 mg/L)
• 35 Increase in four days!!
• Eff. PC ratio went from 37 to 25
• Effluent 1.0 mg/L (was 0.5 mg/L)
• MLVSS/P 7.1 (was running 4.5)

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Shock Load P Balance no chemical being added!
Influent Q 1.6 MGD BOD 250 mg/L BOD 3336
lb/day P 10 mg/L P 133 lb/day
Effluent Q 1.6 MGD BOD 3 mg/L P 1.0 mg/L P
13.0 lb/day
BOD 150 mg/L BOD 2000 lb/day P 6.0 mg/L P
80 lb/day
Primary Clarifier
Secondary Clarifier
Activated Sludge Tank
Primary Sludge Q 10,000 gpd TS 5 P 53
lb/day
RAS
WAS 1000 lb/day P 7.1 P 71 lb/day
P/VS 7.1
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Conclusions

• Enhanced Biological Phosphorus Removal Works!
• Eff. PC can vary and system will adapt quickly
  (shock load test)
• Need to pay attention
• (DO and NO3)
• Side Streams
• Chemical back up if limit is a monthly average
  (If we are getting Eff. P of .7, chemical will
  come on)
• QUESTIONSemail Rein and Associates at
  rein_at_cableone.net or phone [phone]