Nick Landes, Ph.D., P.E.

Finding the right balance:

April 13, 2017

Influent Anoxic AerobicClarifier

Effluent

Solids

RAS

WAS

Secondary clarification enables activated sludge treatment

This Works

This Doesn’t Work

✓

Some Clarification

(1) Separationof Water from Bacteria

(2) Thickening& Return of Bacteria

(3) Storage of Bacteria (only as a last resort)

EFFLUENT

BACTERIA

Factors Impacting Clarifier Performance

• Clarifier Surface Area

• Clarifier Hydraulics

• Flow (Influent, RAS, WAS)

• Mixed Liquor

• Sludge Settling

• Influent quality

• Selector zones

• Operating DO

Not practical to change

Practical to change , not simple

Practical to change on a day

to day basis

Influent Anoxic AerobicClarifier

Effluent

Solids

RAS

WAS

Operating a clarifier has nothing to do with the physical clarifier

Quality Control Performance

State Point Analysis can help understand operational adjustments

• Clarifier Surface Area

• Clarifier Hydraulics

• Flow (Influent, RAS, WAS)

• Mixed Liquor

• Sludge Settling

• Influent quality

• Selector zones

• Operating DO

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, g/L

State Point Analysis (SPA)

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, g/L

Snapshot of your clarifier’s performance

Overflow Line (Inf. Flow)

Solids Flux

(Settleability)

Underflow Line (Inf. Flow,

Recycle Rate, MLSS)

State Point

MLSS Conc. RAS Conc.

Solids Loading

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, g/L

Stay Under the Solid’s Flux Umbrella

Overflow Line (Inf. Flow)

Solids Flux

(Settleability)

Underflow Line (Inf. Flow,

Recycle Rate, MLSS)

State Point

Good performance indicated when:

1. State Point is below Solids Flux

2. Underflow Line is below descending

limb of Solids Flux

Problem 1: Wet Weather Flows

Adjustment 1

•Decrease MLSS to clarifier

•Operate step-feed or

contact stabilization0

10

20

30

40

50

0 5,000 10,000 15,000

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, mg/LAdjustment 2

•Bring offline clarifiers

online

0

10

20

30

40

50

0 5,000 10,000 15,000

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, mg/L

0

10

20

30

40

50

0 5,000 10,000 15,000

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, mg/L

Problem 2: Rising Sludge

Adjustment

•Increase RAS Rate

0

5

10

15

20

25

30

35

40

45

50

0 5,000 10,000 15,000

Solid

s Fl

ux,

lbs

/ sf

-d

MLSS, mg/L

Problem 3: Filamentous Sludge

Adjustment

• Dose Chlorine in RAS

• 2 to 8 lbs Cl2 / d /

1000lb MLSS

SPA Spreadsheet

Developed in Excel

Usable on any device that supports MS Excel

Downloadable Through Dropbox

Procedure for Using Spreadsheet

(0) Physical data

(1) Model Input

(2) Metrics Output

(3/4) SPA Graph and Guidance

(5) Guidance for Impact of SRT change

Measurements

Evaluate Impact of Adjustments

Walk Through

Steps 0 through 2Scan QR Code or Click on

Link for Spreadsheet

Walk Through

Step 3Scan QR Code or Click on

Link for Spreadsheet

Walk Through

Step 4Scan QR Code or Click on

Link for Spreadsheet

Walk Through

Make AdjustmentsScan QR Code or Click on

Link for Spreadsheet

Walk Through

Step 4 Compares

Before/After

Scan QR Code or Click on

Link for Spreadsheet

QUESTIONS?Nick Landes, Ph.D., P.E. │ nick.landes@freese.com │ (817) 735-7571

Influent Aerobic Effluent

WAS

RAS Pump

WAS Pump

Scan QR Code or Click

on Link for Spreadsheet