Prevention of filaments with aluminium or

ozone at Klagshamn WWTP?

Marika Wennberg*, Ulf Nyberg* and Karin Jönsson***VA SYD **Lund University

ProblemFilamentous microorganisms

SolutionAluminium or ozone?

Control of sludge age?

Aluminium Ozone

0 10 20 30 40 50 60 70 800

40

80

120

160

200

240 Experimental line Control line

DS

VI (

ml/g

)

Days of ozone addition0 10 20 30 40 50 60 70 80 90 100

0

40

80

120

160

200

240 06 07 08 09

DS

VI (

ml/g

)

Days of aluminium addition

Dimensioned p.e.

90 000

Actual p.e.

70 000

Actual flow

800 m3/h

Discharge limits

BOD7 10 mg/l*

Tot-P 0.3 mg/l*

Tot-N 12 mg/l**

*monthly average**annual average

Klagshamn WWTP

Effects of filaments

Aluminium treatment

Chemical: PAX-15 (polyaluminium chloride)

Dose: 1.2 g Al/m3

Simple technical equipment

Treatment performed 2006-2009

1-3 months

Focus on DSVI (ml/g)

Four periods of Al-treatment – four different outcomes

0 10 20 30 40 50 60 70 80 90 1000

40

80

120

160

200

240 06 07 08 09

DS

VI (

ml/g

)

Days of aluminium addition

Ozone treatmentFull-scale test, performed in one of the two lines

2.5-months treatment

Dose: 550 g O3/h 0.006 g O3/g MLSS

Process parameters

MLSS-concentration: 3 g/L

Sludge age: 20 days at start-up

Water temperature: 14°C at start-up

Process layout

Ozone makes a difference

0 10 20 30 40 50 60 70 800

40

80

120

160

200

240 Experimental line Control line

DS

VI (

ml/g

)

Days of ozone addition

No ozone Ozone

No ozone Ozone

Improved settling properties

0 10 20 30 40 50 60 70 80

0,0

0,5

1,0

1,5

2,0

2,5

Slu

dge

leve

l (m

)

Days of ozone addition

Experimental line Control line

Effects on nitrification

Lower nitrification rate (mg NH4-N/gVSS,d) in experimental line during lab tests

Higher concentrations of NH4-N in secondary effluent in experimental line

Control of sludge age

2009-03-10 2009-04-18 2009-05-27 2009-07-05 2009-08-13 2009-09-210

40

80

120

160

200

240

280

DSVI Measured sludge age Theoretical sludge age

DS

VI (

ml/g

)

0

10

20

30

40

50

Slu

dg

e a

ge

(d)

Estimated costs

Operating cost

Investment cost

Total cost

Ozone 48 000 250 000 298 000

Aluminium 32 000 5 000 37 000

Removal of floating sludge

300 000

(SEK/year)

Dosing of Aluminium was and was not…

Ozonation was…

Controlling aerobic sludge age was not…

…an option to prevent filamentous growth at Klagshamn WWTP.

What did we learn?

Acknowledgements

Kemira

Air Liquide

Operational and laboratory staff at Klagshamn WWTP