Biological Aerated Filtration (BAF) at the Denver Water Recycling Plant

2006 Water Reuse Workshop

Golden, CO

Russell Plakke, Denver Water

OverviewOverview

Define the project quality goals for the Define the project quality goals for the BAF and PlantBAF and Plant

ConstructionConstruction

Ammonia removal mechanisms utilized, a Ammonia removal mechanisms utilized, a comparisoncomparison

Chemical costs of operationChemical costs of operation

Operational issues/benefitsOperational issues/benefits

Results and performance testsResults and performance tests

Project Definition – Plant QualityProject Definition – Plant Quality

Ammonia goal: non-detectableAmmonia goal: non-detectable

Total Coliform: 2.2/100 mlTotal Coliform: 2.2/100 mlE. ColiE. Coli: 126/100 ml: 126/100 ml

Turbidity: < 1.5 NTUTurbidity: < 1.5 NTUTitle 22 < 2 NTU; Colorado < 3 NTUTitle 22 < 2 NTU; Colorado < 3 NTU

Phosphorus: < 0.6 mg/lPhosphorus: < 0.6 mg/l

BAF Effluent Water BAF Effluent Water Quality RequirementsQuality Requirements

Parameter Effluent Requirement

NH3-N (30-Day Average)

NH3-N (Daily Average)

1.0 mg/ l

2.0 mg/ l

BOD None

TSS None

Reuse Treatment Process

Service Water

Xcel

Mainline

Metro Secondary Clarifier

Pump Station

Burlington Ditch

Rapid Mix Flocculation

SedimentationFiltersContact BasinStorage

Tank

Biological Aerated Filters

Cl2 NH3

NaOH

NaOH, NH3

Sodium Bisulfite

Coagulant Polymer

Polymer Cl2

Cl2

NaOH (NH3)

Cl2NH3

NaOH Cl2 Polymer

BAF ImplementationBAF Implementation

Proposed ammonia removal facility at Proposed ammonia removal facility at WWTP deleted – determined WWTP deleted – determined unnecessary to meet discharge regsunnecessary to meet discharge regs

Fast track schedule necessary Fast track schedule necessary

$10 million change$10 million change

Kruger Biostyr ProcessKruger Biostyr ProcessKruger Biostyr ProcessKruger Biostyr Process

BAF Cell Number SelectionBAF Cell Number Selection

Loading Max. Allowable Loading

Required Number of

Cells

Ammonia Phase I Buildout

2,486 lb/d

3,726 lb/d

Hydraulic Phase I Buildout

Note: 1. Filter cell area is fixed at 703.8 sf/cell and media depth is 9.84 feet 2. Maximum allowable hydraulic loading is with one cell out of service. Maximum allowable ammonia loading is with all cells in service.

~ 60 ~ 60 lb/d/kcflb/d/kcf

6 cells6 cells

9 cells9 cells

~ 5gpm/sf~ 5gpm/sf7 cells7 cells

10 cells10 cells

30 mgd30 mgd

45 mgd45 mgd

On-Line Instrument Comparison

0

5

10

15

20

25

300 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102

108

114

120

126

132

138

144

150

156

162

Time (Hours)

NH

3 m

g/l a

s N

1

Lab

Chem Scan

Ammonia Reduction MechanismsAmmonia Reduction MechanismsUtilizedUtilized

BreakpointBreakpoint

Biological NitrificationBiological Nitrification

CombinationCombination

Breakpoint

Service Water

Xcel

Mainline

Metro Secondary Clarifier

Pump Station

Burlington Ditch

Rapid Mix Flocculation

SedimentationFiltersContact BasinStorage

TankCl2 NH3

NaOH

Coagulant Polymer

Polymer Cl2

Cl2

NaOH (NH3)

Cl2NH3

NaOH Cl2 Polymer

Operational IssuesOperational IssuesBreakpointBreakpoint

Flow limitingFlow limiting CostCost Corrosion caused by off gassingCorrosion caused by off gassing Maintaining effluent chlorine residual Maintaining effluent chlorine residual

Chemical Cost - BreakpointChemical Cost - Breakpoint

Chlorine:Chlorine:– Typical chlorine dose = 119 mg/lTypical chlorine dose = 119 mg/l

– Daily chlorine usage = 6,000 ppdDaily chlorine usage = 6,000 ppd

– Annual chlorine cost = $610,000Annual chlorine cost = $610,000

Caustic:Caustic:– Typical caustic dose = 223 mg/lTypical caustic dose = 223 mg/l

– Daily caustic usage = 11,000 ppdDaily caustic usage = 11,000 ppd

– Annual caustic cost = $870,000Annual caustic cost = $870,000

Chemical Cost With BAFChemical Cost With BAF

Chlorine:Chlorine:– Typical chlorine dose = 6 mg/lTypical chlorine dose = 6 mg/l– Annual chlorine cost = $31,000Annual chlorine cost = $31,000

Caustic:Caustic:– Typical caustic dose = 22 mg/lTypical caustic dose = 22 mg/l– Annual caustic cost = $90,000Annual caustic cost = $90,000

SavingsSavings– Projected annual savings = Projected annual savings = $1,359,000$1,359,000

BAF Seeding

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Days)

NH3 m

g/l a

s N)

BAF Influent

BAF Effluent

Operational Benefits of Operational Benefits of BAFsBAFs

Significantly reduced chemical dose Significantly reduced chemical dose requirements: requirements: – Primary ammonia removal mechanism was Primary ammonia removal mechanism was

changed from breakpoint chlorination to BAFschanged from breakpoint chlorination to BAFs

BAF aeration improved source water BAF aeration improved source water treatablitytreatablity

Excellent ammonia removalExcellent ammonia removal

Effluent QualityEffluent Quality

Breakpoint

Bio (BAF)

Sodium (mg/l)

180 120

Chloride (mg/l)

158 85

Conductivity 1180 929

Nitrate (mg/l as

N)

6.63 14.0

NH3 (Inf) (mg/l as

N)

12.6 9.7

Ammonia removal

0.0

5.0

10.0

15.0

20.0

25.0

6/14 6/15 6/16 6/17 6/18 6/19 6/20 6/21 6/22 6/23 6/24 6/25 6/26 6/27

Time

NH3

mg/

l as

N)

Source Water

Filter Influent - BAF Effuent

Treatability

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

1 2 3 4 5

Time (Days)

NTU

Settled water w/o BAF

Settled water w/ BAF

Filter Effluent w/o BAF

Filter Effluent w/ BAF

Cold Weather Performance TestCold Weather Performance TestInfluent Effluent Reduction

CBOD (mg/l) 13 5 62%

TSS (mg/l) 12 5 58%

Ammonia (mg/l) 15.8 0.15 99%

Nitrite (mg/l) 0.327 0.017 95%

Alkalinity (mg/l) 158 66 58%

pH (SU) 6.60 6.65

Ammonia Swing Load Test

0

1500

3000

1 7 13 19 25 31 37 43

Time (Hours)

NH

3 L

oad

-

Lb

s o

f N

H3-N

/Day

0

0.5

1

1.5

2

BA

F E

fflu

ent

mg

/L N

H3-

N

Ammonia Load (Lbs/Day)

BAF Effluent Ammonia (mg/L)

Peak Ammonia Load Test

0

1500

3000

4500

1 7 13 19 25 31 37

Time (Hours)

NH

3 L

oad

- L

bs

of N

H3-N

/Day

0

0.5

1

1.5

2

2.5

3

3.5

BA

F E

fflu

ent

mg

/L N

H3-

N

Ammonia Load (Lbs/Day) BAF Effluent Ammonia (mg/L)

Designed Peak load for winter conditions: 2600 LBS/Day