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Control of Nitrification at Willmar, MN
John T. O’ConnorBart Murphy
Tom O’Connor
Willmar Municipal Utilities - Water System
Supt. of Water Bart Murphy - (612) 235-4422
Water Sources Southwest Wells, Northeast WellsTreat. Plants Southwest Plant, Northeast Plant
Treatment Packed Tower Aeration, Permanganate Oxidation of Mn, Pressure Greensand Filtration, Chloramination, Fluoridation
Population 22,000 (1995)Production 3.4 mgd (avg.) 6.9 mgd (peak)
Southwest and Northeast Treatment PlantsSouthwest and Northeast Treatment Plants
Willmar’s Tower Willmar’s Tower AeratorsAerators
Aerated Water pH ≥ 8.0Aerated Water pH ≥ 8.0
Willmar staff haveWillmar staff have
developed a developed a freezingfreezing
techniquetechnique for cleaning for cleaning
plastic media plastic media
in the tower aeratorin the tower aerator
Willmar, MNWillmar, MN pH = 7.5 ;Temperature: 5 - 15 °CSource Water Alk.= 400 - 441 mg CaCO3 equiv. / l
Ca = 150 - 260 mg CaCO3 equiv. / l
Ammonium Ion 3.2 mg N / l (NE) ; 2.5 mg N / l (SW)
Iron Removal 1.67 0.00 mg Fe / lMn Removal 0.109 0.05 mg Mn / l
Lead (1992) < 5 to 43 µg Pb / l Copper (1992) < 0.50 to 7.0 mg Cu / l
Corrosion Control Treatment: Aeration to increase pH from 7.5 to
8.1
Uniform, Smooth, Colored Deposits in Copper Pipe
Optimum Copper Corrosion Control Treatment Optimum Copper Corrosion Control Treatment (OCCT)(OCCT)
pH / alkalinity to decrease solubility of metal carbonates, oxides
calcium to increase calcium carbonate supersaturation,
deposition
polyphosphate to cause formation of phosphate films on mains and plumbing silicate to promote formation of
protective silicate films
Copper Pipe Test Loops
and
Copper Pipe Test Sections
Sampling Copper Pipe Test LoopsSampling Copper Pipe Test Loops
Copper Pipe SectionsCopper Pipe Sections
MgO ColumnsMgO Columns
Copper Pipe Loops
On-Site Studies - an Opportunity for Mutual EducationOn-Site Studies - an Opportunity for Mutual Education
The War Room – Studies were plannedThe War Room – Studies were plannedbased on the previous day’s resultsbased on the previous day’s results
Microscopic Enumeration of Total Bacteria
Tap 3 4 5 8 9 13 25 36 49 Main0
2
4
6
8
10
12
Sequential Household Tap Sampling at Bart Murphy Residence
Copper
NH4+
Sequential Sample, 250 ml Aliquot
Chloramine
Dissolved Oxygen
Bacterial Cells
BB
B
B
B
BB
B
B
B
B
BB
B B
BB
0
1
2
3
0 1 2 3 4 5 6
Chloramine Consumed, mg Cl/l
1.3 mg Cu/l Copper Action Level
B
B
B BB
J
J
JJ
J
0
1
2
3
0 30 60 90
Time of Contact, minutes
B Copper, mg Cu/l
J Chloramine, mg Cl/l
Control StrategyControl Strategy
• • Control nitrifying bacteria in the distribution system.Control nitrifying bacteria in the distribution system.
• • Control formation of nitrite during distribution.Control formation of nitrite during distribution.
• • Control the loss of chloramine in distribution system.Control the loss of chloramine in distribution system.
• • Reduce concentration of chloramine applied as a Reduce concentration of chloramine applied as a
distribution system residual.distribution system residual.
Ozone Generator and Ozonation Pilot Plant Oxygen Cylinder; Ozone generator; Pump, Injector and Contactor Degassing Separator; Ozone Destruct Column (wall-mounted, black)
Two Greensand Filter Columns (black) in Series;
Clear Well (white)
AeratedAerated
Iron Iron OxidesOxides
Well Well Water Water SourceSource
Ozonated Ozonated and Filteredand Filtered Ozonated Ozonated
PermanganatePermanganate
Magnesium Oxide for pH Adjustment;Magnesium Oxide for pH Adjustment;Acceleration of Kinetics of OzonationAcceleration of Kinetics of Ozonation
Oxidation ofAmmonium Ion by ozone is acceleratedBy high pH and alkalinity
The addition of MgO particlesprovides pin-point regions of high pH
B
B
B
B
B
J
J
0
1
2
3
0 60 120 180
milligrams / liter
Time after Ozonation, minutes
Ammonium Ion
Ozone
Ozone and Ammonium Ion Persistence
0
2
4
6
8
10
12
14
0 5 10 15 20 25 30
Chlorine Applied, mg Cl/l
Combined ChlorineResidual (Chloramine)
"Free"Chlorine, HOCl
NH2Cl
N2
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10 12 14 16 18 20 22 24
Chlorine Applied, mg Cl/l
Total Chlorine
Free Chlorine
Chloramines
Ammonia-N
Nitrate-N
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Chlorine Contact Time, Minutes
20 mg Cl/l
23 mg Cl/l
25 mg Cl/l
Breakpoint Breakpoint Ammonium Ammonium Reduction Reduction
Treatment (BART)Treatment (BART)
Chlorine Injectors for Increased Application of Chlorine Gas
2.4
0.02
-
8
0
1.16
1.56
7.6
0
0.76
1.01
7.6
1.92
0.14
3.12
8.02
1.96
0.13
3.18
8.07
0.93
0.17
2.48
8.1
-
0.14
2.44
-
AeratorEffluent
#1:BART
Influent
#1:BART
Effluent
#2:Chloramine
Influent
#2:Chloramine
Effluent
CombinedPlant Effluent
Clearwell
2.4
0.02
-
8
0
1.16
1.56
7.6
0
0.76
1.01
7.6
1.92
0.14
3.12
8.0
1.96
0.13
3.18
8.1
0.93
0.17
2.48
8.1
-
0.14
2.44
-
NH4+
Free Chlorine
Total Chlorine
pH
AeratorEffluent
#1: BARTInfluent
#1: BARTEffluent
#2: ChloramineInfluent
#2: ChloramineEffluent
CombinedPlant Effluent
ClearwellSouthwest
Plant
2.11
0.13
0.001
14
9
7.46
-
-
-
2.11
0.14
0.001
14
10
-
-
-
-
0.006
0.03
0.001
4
10
7.57
0.0
1.50
0.80
0.005
0.08
0.001
3
10
8.03
2.0
-
-
-
-
-
-
-
-
1.0
2.12
0.11
Fe, mg/l
Mn++, mg/l
H2S, mg/l
Color, Pt-Co
Temp. °C
pH
NH4+ , mg N/l
Total Cl, mg Cl/l
Free Cl, mg Cl/l
Influent Aerated #1: BART#2: Chloramine
+ KMnO4#1 + #2: FinishedSouthwest Plant
after BART
18
26
25
3
3
3
10
10
10
11
10
10
27
31
BART-12/7/96
BART-12/8/96
BART-12/9/96
Chloramine-12/7
Chloramine-12/8
Chloramine-12/9
Combined-12/7
Combined-12/8
Combined-12/9
Clearwell-12/7
Clearwell-12/8
Clearwell-12/9
College Sys.-Near
College Sys.-Far
Total THM,µg/l
SouthwestPlant
B
B
B
B B BB
B
B
B
B B
J
JJ
J
J
J
J
J
J
J
JJ
H HH
H H H
H
HH H
H
H
F F
F
F F
F
FF
F
FF
F
Ñ
ÑÑ
Ñ ÑÑ
Ñ Ñ
Ñ
Ñ Ñ
Ñ
É
É
É É É É
É
ÉÉ
ÉÉ
É
ÇÇ
Ç Ç Ç
Ç
Ç Ç
Ç Ç
Ç
Ç
Å
ÅÅ
Å Å ÅÅ
Å
Å ÅÅ Å
M
M
M
M M
M M
M
MM
M
Mâ
â
â
ââ â
ââ
â â
â
â
Ö
ÖÖ
Ö Ö ÖÖ
Ö
Ö ÖÖ Ö7
7
7
7 7
77
7
77
7
7
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
1
2
3
B 1
J 4
H 7
F 9
Ñ 11
É 12
Ç 13
Å 14
M 17
â 18
Ö 24
7 30
Monitoring Stations
Willmar Distribution System Ammonium Ion after BART
Average SWP Influent
B
BB
B B B B BB B
B B
B
B
B
BB B
BB
B B B BDec Jan Feb Mar Apr May June July Aug Sept Oct Nov
0
1
2
3
4
Range of Ammonium Ion Concentrations after BART
Average Southwest Plant Influent
Average Northeast Plant Influent
Average of 12 Distribution
SystemSampling Sites
B BB
B BB
B BB B
BB
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
1
2
3
4
Average Ammonium Ion Concentration after BART
Average SWP Influent
Average NEP Influent
Average of 12 Distribution System Sampling Sites
SWP BART Effluent
B
B
B
B B
J
J
JJ
JH H H H H
F
F
F FF
ÑÑ Ñ Ñ
ÑÉÉ
ÉÉ É
Ç Ç Ç Ç ÇÅÅ
ÅÅ
ÅM
M MM M
â
ââ â â
Ö
ÖÖ Ö Ö
77
7
7 7
Dec Jan Feb Mar Apr0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
B 1
J 4
H 7
F 9
Ñ 11
É 12
Ç 13
Å 14
M 17
â 18
Ö 24
7 30
Sampling Station
Distribution System Nitrite Ion - Willmar, MN
B
B
B
B B B B
B
B B
B B
J
J
JJ
JJ
J
JJ J
JJ
HH H H H H
HH
H HH H
F
F
FF
F F FF F F
F F
ÑÑ
Ñ ÑÑ Ñ
Ñ Ñ
Ñ ÑÑ Ñ
ÉÉ
ÉÉ É
É
ÉÉ
ÉÉ É
É
Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç ÇÅÅ
ÅÅ
Å Å
ÅÅ
ÅÅ Å ÅM
M MM M
MM M M M M M
â
ââ â â â â
â ââ â â
Ö
Ö
Ö Ö Ö Ö Ö Ö Ö Ö Ö Ö
77
7
7 7
77 7
7
77
7
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov
0
0.4
0.8
1.2
1.6
B 1
J 4
H 7
F 9
Ñ 11
É 12
Ç 13
Å 14
M 17
â 18
Ö 24
7 30
Monitoring Stations
Distribution System Nitrite Ion after BART, Dec. '96 - Nov. '97
USEPA MCL: 1 mg N / l
B
B
B BB B
B B
B BB B
B B B B B B B B B B B BDec Jan Feb Mar Apr May June July Aug Sept Oct Nov
0
0.4
0.8
1.2
1.6
Range of Nitrite Ion Concentrations after BART - Willmar, MN
USEPA MCL
B
B
B B B BB B B B
B B
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
0.2
0.4
0.6
0.8
1.0
Average of Nitrite Ion Concentrations after BART
USEPA MCL
B
B
B
BB
J
J
JJ
JH H
H HH
F
F
FF F
Ñ ÑÑ
Ñ ÑÉ
É
É ÉÉ
Ç ÇÇ
Ç Ç
Å ÅÅ
ÅÅ
M
MM
MM
â
ââ
ââ
ÖÖ
ÖÖ Ö
77
7
77
Dec Jan Feb Mar Apr0
0.5
1
1.5
2
2.5
3
3.5
B 1
J 4
H 7
F 9
Ñ 11
É 12
Ç 13
Å 14
M 17
â 18
Ö 24
7 30
Sampling Station
Distribution System Nitrate Ion - Willmar, MN
B
B
B
BB
BB
B
BB B
B
J
J
JJ
J
J
J
J
JJ
J JH H
H HH H
H HH H H H
F
F
FF F F F F
FF
FF
Ñ ÑÑ
Ñ Ñ
ÑÑ
ÑÑ Ñ Ñ
ÑÉ
É
É ÉÉ
ÉÉ
É
É ÉÉ
ÉÇ Ç
ÇÇ Ç
ÇÇ
ÇÇ Ç Ç
Ç
Å ÅÅ
ÅÅ
ÅÅ
Å ÅÅ
Å ÅM
MM
MM
M M M M M M M
â
ââ
ââ
â â ââ â â
âÖ
Ö
ÖÖ Ö
ÖÖ
ÖÖ
Ö Ö Ö
77
7
77
77
77
77
7
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
0.5
1
1.5
2
2.5
3
3.5
B 1
J 4
H 7
F 9
Ñ 11
É 12
Ç 13
Å 14
M 17
â 18
Ö 24
7 30
Monitoring Stations
Distribution System Nitrate Ion after BART, Dec. '96 - Nov. '97
B
B
BB B B
BB
BB B B
BB
B B B BB
B B B B B
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
0.5
1
1.5
2
2.5
3
3.5
Range of Nitrate Ion Concentration after BART - Willmar, MN
B
B
BB B B
BB B B
BB
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
0.4
0.8
1.2
1.6
Average Nitrate Ion Concentration after BART
BB
B
B
B
B
BB
B
B
BB
J
J J
J
J
J
J
JJ
J
J
J
HH
H
H
H
H
H
H HH
H
H
F
FF
F
F
F
F
FF
FF
F
Ñ Ñ
Ñ
ÑÑ
Ñ
ÑÑ
ÑÑ
Ñ
Ñ
É
É
É
É
ÉÉ
É
ÉÉ
É
ÉÉ
Ç
ÇÇ
Ç Ç
Ç
Ç
Ç Ç Ç
Ç Ç
Å
ÅÅ
Å
ÅÅ
ÅÅ
Å Å Å Å
M
M
M
M M
MM
M MM
M
M
â
â
â
â
â
â
ââ
ââ
â
â
Ö
Ö
ÖÖ
ÖÖ
Ö
ÖÖ
Ö
Ö
Ö
77
7
7
7
77
7
7
7 7
7
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
1
2
3
B 1
J 4
H 7
F 9
Ñ 11
É 12
Ç 13
Å 14
M 17
â 18
Ö 24
7 30
Monitoring Stations
Distribution System Chloramine after BART
Target: Minimum Chloramine = 0.5 mg Cl/l
B
BB
BB
B BB
BB
BB
B
BB
B
BB
BB
B B B B
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
0.5
1.0
1.5
2.0
2.5
3.0
Range of Chloramine Concentrations after BART
Target: Minimum Chloramine = 0.5 mg Cl/l
Chloramine Application at SWP reduced from 2.8 to 1.8 mg Cl/l
BB B
B
B
B
BB
BB
B B
Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0
0.5
1
1.5
2
Average Chloramine Concentrations after BART
Target: Minimum Chloramine = 0.5 mg Cl/l
SWP Finished Water Chloramine = 1.8 mg Cl/l
BARTBreakpoint Ammonia Reduction Treatment
• Persistent disinfectant residuals
• Suppression of nitrite ion formation
• Avoidance of excessive trihalomethanes
• Enhanced manganese removal
• Reduction of true natural color = ozone
Back Road to Willmar’s East PlantBack Road to Willmar’s East Plant