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Austin’s Full-Scale Step-BNR Demonstration - WEATs Full-Scale Step-BNR... · • Biological...

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Austin’s Full-Scale Step-BNR Demonstration Rajendra P. Bhattarai, P.E., DEE Austin Water Utility, City of Austin 625 East 10 th Street, Suite 300 Austin, Texas 78701 Phone: 512-972-0075, Fax: 512-974-3504 [email protected] San Antonio, Texas July 24, 2015 Summer Seminar Emerging Issues in the Water/Wastewater Industry
Transcript

Austin’s Full-Scale Step-BNR Demonstration

Rajendra P. Bhattarai, P.E., DEE Austin Water Utility, City of Austin

625 East 10th Street, Suite 300 Austin, Texas 78701

Phone: 512-972-0075, Fax: 512-974-3504 [email protected]

San Antonio, Texas

July 24, 2015

Summer Seminar Emerging Issues in the Water/Wastewater Industry

Presentation Outline

• Background • Step-Feed • Biological Nutrient Removal (BNR)

System Used • Operating Characteristics • Results • Lessons Learned

Background • Austin’s wastewater treatment plants

discharge to the Colorado River • Waterbody of exceptional quality • Nutrient removal required in future • Need for demonstration of N & P removal

• Goal: TP < 1mg/L; TN < 10 mg/L • Full-Scale Step-Feed BNR operated at

South Austin Regional (SAR) WWTP for two years: January 1996 - December 1997

Activated Sludge

Influent

RAS

WAS

Aerobic Effluent

Influent

RAS

WAS

Aerobic Effluent

10 MGD MLSS = 3,000 mg/l

For 25% increase in treatment capacity 12.5 MGD MLSS = 3,750 mg/l

High MLSS can overload secondary clarifier

Activated Sludge

Step-Feed Primary Effluent

4,900 MLSS

3,800 MLSS

3,300 MLSS

3,000 MLSS

Aerobic Average MLSS = 3,750 mg/l

RAS WAS

Final Clarifier

40% 30% 20% 10%

Advantages of Step-Feed

• Operational Flexibility • Higher MLSS results in higher capacity

without increasing solids loading to secondary clarifiers

• Maximize use of existing facilities • Better handling of peak flows • Robust and stable operation

Q

Anaerobic Aerobic

Q

WAS RAS

Anoxic

Nitrate Recycle, 1-2Q Anoxic Recycle, 1-2Q

A staged reactor configuration is provided by using at least two complete-mix cells in series for each zone of the biological reactor.

Virginia Initiative Plant (VIP) Process

(NRCY) (ARCY)

Step-Feed Primary Effluent

4,900 MLSS

3,800 MLSS

3,300 MLSS

3,000 MLSS

Aerobic

RAS WAS

Final Clarifier

40% 30% 20% 10%

BNR demonstration system at SAR used the “Step-Feed BNR Process” --

combination of VIP and Step-Feed

PE ARCY PE ARCY

ANR ANX AER ANR ANX AER AER

RAS NRCY

SOUTH AUSTIN REGIONAL WASTEWATER TREATMENT PLANT

LIFT

STATIONS GRIT

BASINS

INFL

UE

NT

BA

R

SC

RE

EN

S

PRIMARY CLARIFIERS

FLOW EQUALIZATION

DIVERSION BOX

ACTIVATED SLUDGE

AERATION BASINS

SECONDARY CLARIFIERS CHLORINATION

SCREENINGS AND GRIT TO

LANDFILL EFFLUENT FILTERS

DECHLORINATION

DISCHARGE TO THE COLORADO RIVER

EFF

LUE

NT

RETURN ACTIVATED SLUDGE

WASTE ACTIVATED SLUDGE SLUDGE BLENDING

GRAVITY THICKENER

SLUDGE PUMPS

TO HORNSBY BEND BIOSOLIDS MANAGEMENT PLANT

FILTER BACKWASH

SUPERNATANT REUSE PUMPS

TO GOLF COURSE

IRRIGATION

PR

IMA

RY

SLU

DG

E

South Austin Regional Wastewater Treatment Plant

Train A Train B

BNR

Control

Activated Primary for VFA Generation

Raw Primary Effluent Wastewater containing VFAs

Return Primary Sludge (Elutriates Sludge)

Waste Primary Sludge (To Thickening)

Original Aeration Basin Flow Path

Effluent Channel

Influent Channel

RAS

Cha

nnel

(RAS and PE mix)

Primary Effluent

Flow Diversion Box

Aeration Basin Step-BNR Modified Flow Path

Effluent Channel

Influent Channel R

AS

Cha

nnel

Primary Effluent

Normal Input of Secondary Influent

Flow Diversion Box

AER

AER Pass 4

AER Pass 3

AER Pass 2

AER Pass 1

AER ANR

ANX

ANR

ANX

ANR

ANX

ANR

ANX

ANR ANR

ANX ANX

ANR ANR

ANX ANX AER AER

48” Bypass

Indicates Internal Recycle

RAS (Alt)

Baffles added to Existing Aeration Basins to form Anaerobic, Anoxic and Aerobic Zones Volume, million gallons Step- BNR Control Total 2.6 2.6 Anaerobic 0.4 0 Anoxic 0.4 0 Aerobic 1.8 2.6

Baffles for Anaerobic, Anoxic and Aerobic Zones

Aeration Basin on the “Control” side Activated Sludge No persistent foam Only air bubbles

BNR Basins: Aerobic Zone in the foreground; Anoxic and Anaerobic Zones in the background. Comparatively more foam and scum than “control”

BNR Basins: Anaerobic Zone in the foreground; Anoxic and Aerobic Zones in the background

Close-up view of the Anaerobic Zone

Wastewater Temperature: 19o- 30o C

16

18

20

22

24

26

28

30

32

Influ

ent T

empe

ratu

re,

o C

1 7 6 5 4 3 2

Operating Periods:

1-M

ar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

Test flows were 6 to 20 MGD

0

2

4

6

8

10

12

14

16

18

20

Prim

ary

Efflu

ent F

low

, MG

D

BNR

CONTROL

Operating Periods:

1 7 6 5 4 3 2

1-M

ar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

Jan-

96

Mar

-96

Jun-

96

Sep-

96

Dec

-96

Mar

-97

Jun-

97

Sep-

97

Dec

-97

Period 7

Period 6

Period 5

Period 4

Period 3

Period 2

Period 1

Startup

Flow and Temperature Defined Operating Periods

Steady 8 MGD; ~22o C

Steady 8 MGD; ~27o C

(Construction Outage)

9-20 MGD; ~22o C

12 MGD; ~28o C

10-13 MGD; ~27o C

Improved APC, Steady 6 MGD; ~22o C

0

10

20

30

40

50

60

70

80

Net

TSC

OD

Pro

duce

d, m

g/L

1 7 6 5 4 3 2

Activated Primary Clarifier worked well at times

1-M

ar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

MCRT lower than in Control

0

5

10

15

20

25 Ae

robi

c M

CR

T, d

ays

CONTROL

BNR

1 2 3 4 5 6 7

1-M

ar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

SVI for BNR was higher

0

20

40

60

80

100

120

140

160

180 1-

Mar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

Slud

ge V

olum

e In

dex

(SVI

), m

L/g

BNR

Control

Excessive Foaming

1 2 3 4 5 6 7

Excessive Foaming in BNR Basins due to Nocardia Growth and poor hydraulics

Both systems nitrified well Ef

fluen

t NH

3 -N

, mg/

L

BNR

CONTROL

Trend lines are seven day moving averages

1 7 6 5 4 3 2

10.00

1.00

0.10

0.01

1-M

ar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

0

5

10

15

20

25

30

35

Efflu

ent N

O 3 -

N, m

g/L

BNR

CONTROL

1 7 6 5 4 3 2

Nitrogen removal was good 1-

Mar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

BNR Ortho-P Profile 3/13/96 to 4/8/96

PASS-1 PASS-2 PASS-3 PASS-4

2

4

6

8

10

12

PRI1

B

ANR

1W

ANR

1E

ANX1

E

ANX1

W

AER

1S

ANR

2W

ANR

2E

ANX2

E

ANX2

W

AER

2N

ANR

3W

ANR

3E

ANX3

E

ANX3

W

AER

3S

AER

4S

ZONES

Ort

ho-P

, mg

/ L

P removal was variable

0

1

2

3

4

5

6

7

Efflu

ent O

rtho

- P, m

g/L

BNR CONTROL

1 7 6 5 4 3 2 1-

Mar

12-A

pr

24-M

ay

5-Ju

l

16-A

ug

27-S

ep

8-N

ov

20-D

ec

31-J

an

14-M

ar

25-A

pr

6-Ju

n

18-J

ul

29-A

ug

10-O

ct

21-N

ov

2-Ja

n

Lessons Learned

• BNR systems not that different from other treatment systems

• But they do require some understanding and familiarity

• BNR systems need more operational attention than conventional activated sludge

Lessons Learned (continued)

• Volatile Fatty Acids crucial for BNR - especially for phosphorus removal

• VFA production depends on Activated Primary Clarifier operation

• BNR systems more prone to foaming than conventional activated sludge

• Foaming can be controlled using polymers, water sprays and chlorine

Lessons Learned (continued)

• Allow sufficient hydraulic head between different zones for easy removal of scum and foam

• Provide free-flow path at water surface through all zones to secondary clarifiers for scum removal

• Good hydraulics for flow split critical for Step-feed

Lessons Learned (continued)

• Nitrogen removal depends on F/M in anoxic zones

• Phosphorus removal depends on F/M in anaerobic zones (especially VFAs)

• Phosphorus removal is directly proportional to the amount of phosphorus released in the anaerobic zones

Questions, Comments?

South Austin Regional Wastewater Treatment Plant

Train A Train C

Train B

Control BNR


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