Control of Nitrification at Willmar, MN. John T. O’Connor Bart Murphy Tom O’Connor.

transcript

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

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

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

Sequential Household Tap Sampling at Bart Murphy Residence

Copper

Sequential Sample, 250 ml Aliquot

Chloramine

Dissolved Oxygen

Bacterial Cells

0 1 2 3 4 5 6

Chloramine Consumed, mg Cl/l

1.3 mg Cu/l Copper Action Level

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

0 60 120 180

milligrams / liter

Time after Ozonation, minutes

Ammonium Ion

Ozone and Ammonium Ion Persistence

0 5 10 15 20 25 30

Chlorine Applied, mg Cl/l

Combined ChlorineResidual (Chloramine)

"Free"Chlorine, HOCl

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 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

AeratorEffluent

#1:BART

Influent

#1:BART

Effluent

#2:Chloramine

Influent

#2:Chloramine

Effluent

CombinedPlant Effluent

Clearwell

Free Chlorine

Total Chlorine

AeratorEffluent

#1: BARTInfluent

#1: BARTEffluent

#2: ChloramineInfluent

#2: ChloramineEffluent

CombinedPlant Effluent

ClearwellSouthwest

Fe, mg/l

Mn++, mg/l

H2S, mg/l

Color, Pt-Co

Temp. °C

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

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 BB

Ñ ÑÑ

É É É É

Ç Ç Ç

Å Å ÅÅ

Å ÅÅ Å

ââ â

Ö Ö ÖÖ

Ö ÖÖ Ö7

Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov0

Monitoring Stations

Willmar Distribution System Ammonium Ion after BART

Average SWP Influent

B B B B BB B

B B B BDec Jan Feb Mar Apr May June July Aug Sept Oct Nov

Range of Ammonium Ion Concentrations after BART

Average Southwest Plant Influent

Average Northeast Plant Influent

Average of 12 Distribution

SystemSampling Sites

B BB B

Average Ammonium Ion Concentration after BART

Average SWP Influent

Average NEP Influent

Average of 12 Distribution System Sampling Sites

SWP BART Effluent

JH H H H H

ÑÑ Ñ Ñ

ÑÉÉ

ÉÉ É

Ç Ç Ç Ç ÇÅÅ

M MM M

ââ â â

ÖÖ Ö Ö

Dec Jan Feb Mar Apr0

Sampling Station

Distribution System Nitrite Ion - Willmar, MN

B B B B

HH H H H H

H HH H

F F FF F F

Ñ ÑÑ Ñ

ÉÉ É

Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç Ç ÇÅÅ

ÅÅ Å ÅM

M MM M

MM M M M M M

ââ â â â â

â ââ â â

Ö Ö Ö Ö Ö Ö Ö Ö Ö Ö

Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov

Monitoring Stations

Distribution System Nitrite Ion after BART, Dec. '96 - Nov. '97

USEPA MCL: 1 mg N / l

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

Range of Nitrite Ion Concentrations after BART - Willmar, MN

USEPA MCL

B B B BB B B B

Average of Nitrite Ion Concentrations after BART

USEPA MCL

Ñ ÑÑ

Ñ ÑÉ

É ÉÉ

Ç ÇÇ

Å ÅÅ

ÖÖ Ö

Dec Jan Feb Mar Apr0

Sampling Station

Distribution System Nitrate Ion - Willmar, MN

J JH H

H HH H

H HH H H H

FF F F F F

Ñ ÑÑ

ÑÑ Ñ Ñ

É ÉÉ

ÉÇ Ç

ÇÇ Ç

ÇÇ Ç Ç

Å ÅÅ

Å ÅM

M M M M M M M

â â ââ â â

ÖÖ Ö

Ö Ö Ö

Monitoring Stations

Distribution System Nitrate Ion after BART, Dec. '96 - Nov. '97

BB B B

B B B BB

B B B B B

Range of Nitrate Ion Concentration after BART - Willmar, MN

BB B B

Average Nitrate Ion Concentration after BART

Ç Ç Ç

Å Å Å Å

Monitoring Stations

Distribution System Chloramine after BART

Target: Minimum Chloramine = 0.5 mg Cl/l

B B B B

Range of Chloramine Concentrations after BART

Chloramine Application at SWP reduced from 2.8 to 1.8 mg Cl/l

Average Chloramine Concentrations after BART

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

Control of Nitrification at Willmar, MN. John T. O’Connor Bart Murphy Tom O’Connor.

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