cnr istituto di ricerca sulle acque via f. de blasio, 5

Degradation of polybrominated diphenyl ethers

in sewage sludge by ozonation and solubilisation

of degradation products in the water phase

Giuseppe Mascolo CNR – Istituto di Ricerca Sulle Acque

Via F. de Blasio, 5 - 70132 Bari, Italy

Presentation outline

• Focusing the problem;

• Potential side-benefits of sludge ozonation;

- Process performance through gross-parameters monitoring

- removal of PolyBrominated Diphenyl Ethers (PBDEs);

- Organic bromine distribution between liquid and solid phase;

- by-products formation/degradation and toxicity;

• Results obtained treating real sewage sludge (primary and

mixed digested) by ozone:

• Conclusions.

FOCUSING THE PROBLEM

• Management of sludge produced in the wastewater treatment

plants represents a global environmental and economic issue:

– The volume of the sludge extracted from primary and secondary

settling tanks is about 2% of the volume of treated wastewater;

– Sludge treatment and disposal entails very high capital and

operating costs, which can account for as high as 50 % of the

total costs of wastewater treatment plant;

• Presently, an outlet for sludge disposal is its use in agriculture as

a fertilizer.

• According to 86/278 Directive, sludge has to be used taking

primarily into account the nutrient needs for plant growth, and that

the quality of the soil and the surface- and ground-waters is not

impaired.

Organic pollutants in sludge: how is it possible to limit their presence?

• Brominated flame retardants enter sewage treatment plants and are

mainly partitioned onto sludge due to their hydrophobic properties.

They are then accumulated on sludge causing pollution of the sites

where sludge is ultimately disposed of.

• During operation of wastewater treatment plants sorption of

hydrophobic organics onto sludge flocs occurs.

Primary

settler influent Aeration basin secondary

settler

organics

adsorption

effluent

0.1

1

10

100

1000

10000

BDE-47

BDE-100

BDE-99

BDE-154

BDE-153

BDE-183

BDE-196

BDE-196

BDE-203

BDE-205

BDE-209

co

ncen

trati

on

in

th

e s

lud

ge (

ug

/kg

)

BDE congener

number of bromine atoms

BDE-47 4

BDE-99 5

BDE-100 5

BDE-153 6

BDE-154 6

BDE-183 7

BDE-196 8

BDE-197 8

BDE-203 8

BDE-205 8

BDE-209 10

Organic pollutants in sludge: PolyBrominated Diphenyl Ethers (PBDEs)

Primary

settler influent Aeration basin secondary

settler

Places where ozonation

can be employed

returned sludge

Digestion

tank

excess sludge

Application of ozonation for sludge reduction

centrifugation reuse in agriculture

effluent

Experiments on ozonation of sewage sludge to degrade

brominated flame retardants on primary and mixed-digested

sludge.

Identification of degradation products and degradation pathway.

Main goals of the performed investigation

sludge

O3

O3 O3

degradation products

TSS, mg/L

VSS, mg/L

VSS/TSS COD, mg/L

TN, mg/L

N-NH4, mg/L

N-NO2, mg/L

N-NO3, mg/L

P tot, mg/L

IC, mg/L

DOC, mg/L

influent (total)

254 ± 37

221 ± 29

0.87 ± 0.03

408 ± 48

52 ± 7

45.2 ± 4.5

7.5 ± 2.0

influent (sol.)

116 ± 42

45.8 ± 8.1

39.8 ± 3.7

0.03 ± 0.01

0.14 ± 0.08

5.3 ± 2.1

87.4 ± 6.4

34.2 ± 10

effluent (total)

120 ± 31

109 ± 24

0.91 ± 0.06

309 ± 47

44.1 ± 4.3

38.1 ± 7.0

5.5 ± 2.1

effluent (sol.)

127 ± 55

35.7 ± 5.0

32.8 ± 7.2

0.03 ± 0.01

0.20 ± 0.06

3.6 ± 0.9

84.5 ± 9.9

39.6 ± 14

Bari-west wastewater treatment plant

250,000 PE

Average flow rate = 0.6 m3/s, pH = 7.5-7.9

Composition of influent/effluent wastewater (primary step)

ozone dose gozone/gTSS

TSS g/L

VSS g/L

VSS/TSS COD g/L

TN mg/L

N-NH4 mg/L

N-NO2 mg/L

N-NO3 mg/L

P tot. mg/L

IC mg/L

TOC mg/L

total (liquid + solid phase)

0 24.3 16.9 0.695 28.6 589 560 316

0.014 23.2 16.6 0.716 24.6 593 532 298

0.038 21.2 14.5 0.684 26.4 587 532 297

0.061 19.8 13.6 0.687 26.6 579 539 317

0.105 19.6 13.1 0.668 26.5 593 574 311

liquid phase

0 0.44 462 323 3.03 0.45 4.6 543 176

0.014 1.5 498 343 2.77 0.94 5.5 358 539

0.038 2.6 521 385 1.28 3.25 12.2 356 1045

0.061 3.8 584 385 1.86 14.4 13.7 335 1395

0.105 4.5 601 399 1.75 24.4 20.7 290 1886

Ozonation of mixed-digested sludge: gross parameters

ozone dose gozone/gTSS

TSS g/L

VSS g/L

VSS/TSS COD g/L

TN mg/L

N-NH4 mg/L

N-NO2 mg/L

N-NO3 mg/L

P tot. mg/L

IC mg/L

TOC mg/L

total (liquid + solid phase)

0 30.3 23.7 0.78 55 1240 280 390

0.014 29.3 22.4 0.76 51 1230 283 345

0.038 27.1 20.6 0.76 48.6 1130 297 326

0.061 26.9 19.8 0.73 48 1186 313 319

0.105 22.1 16.0 0.73 38.8 1210 294 374

liquid phase

0 1.5 171 98 <dl <dl 24.2 132 468

0.014 4.4 296 133 <dl 1.1 25.5 77 1404

0.038 5.8 563 168 1 2 25.9 69 1985

0.061 6.6 695 201 2 28 35.4 27.4 2361

0.105 7.9 802 224 1 59 46.5 26.2 3038

Ozonation of primary sludge: gross parameters

Mixed Digest Sludge:Concentration Trend of PBDEs vs Ozone Dose

Ozone dose (gozone/gTSS)

0.00 0.02 0.04 0.06 0.08 0.10 0.12

Resi

dua

l [B

DE

-209

] (

g/g

)

0

500

1000

1500 BDE_209


0.00 0.02 0.04 0.06 0.08 0.10

Ozo

ne

ou

tle

t g

as (

mg

/L)

0

5

10

15

20

25

Off-gas ozone concentration profile during

ozonation of mixed digested sludge.


0.00 0.02 0.04 0.06 0.08 0.10

Ozo

ne

ou

tle

t g

as (

mg

/L)

0

5

10

15

20

25

Primary Sludge:Concentration Trend of PBDEs vs Ozone Dose


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Resid

ual [B

DE

-209] (

g/k

g)

0

500

1000

1500 BDE_209

mixed digested

sludge

Ozonation of primary and mixed digested sludge: BDE-209 decay and off-gas ozone concentration

primary sludge

Mixed Digest Sludge:Concentration Trend of PBDEs vs Ozone Dose


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Resid

ua

l co

nce

ntr

atio

n (

g/g

)

0

2

4

6

8

10

12

14

BDE_47

BDE_99

BDE_197

BDE_196

BDE_203


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Resid

ual concentr

ation (

g/g

)

0.0

0.5

1.0

1.5

2.0

2.5

BDE_100

BDE_154

BDE_153

BDE_183

BDE_205

Ozonation of primary and mixed digested sludge: PBDEs decay/formation


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Re

sid

ua

l co

nce

ntr

atio

n (

g/k

g)

0

5

10

15

20

25BDE_47

BDE_99

BDE_197

BDE_196

BDE_203


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Resid

ua

l co

nce

ntr

atio

n (

g/k

g)

0

1

2

3

4

5

BDE_100

BDE_154

BDE_153

BDE_183

BDE_205

mixed digested

sludge

primary sludge

some debromination occurs in the early stage of the

ozonation. Then degradation prevails.


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Re

sid

ua

l o

rga

nic

ha

log

en

s (

mm

ol/kg

)

0.00

0.02

0.15

0.20 Br of PBDEs

EOX


0.00 0.02 0.04 0.06 0.08 0.10 0.12

Resid

ual org

anic

halo

ge

ns (

mm

ol/kg)

0.00

0.01

0.15

0.20 Br of PBDEs

EOX

Ozonation of primary and mixed digested sludge: organic bromine and total organic halogens decay

mixed digested

sludge primary sludge

During ozonation a large fraction of organic

bromine is transferred to the water phase.

Ozonation of primary and mixed digested sludge: Degradation of total organic halogens in both liquid and solid phase

mixed digested

sludge

primary sludge

Ozonation of primary and mixed-digested sludge: identification of degradation products

Ozonation of primary and mixed-digested sludge: identification of degradation products

TIC of -Prec (79.00): Exp 1, from Sample 1 (SPE_R_1 neg) of SPE_R_1 neg.wiff (Turbo Spray) offset by 0.50 min

Max. 1.4e6 cps.

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0Time, min

0.0

1.0e5

2.0e5

3.0e5

4.0e5

5.0e5

6.0e5

7.0e5

8.0e5

9.0e5

1.0e6

1.1e6

1.2e6

1.3e6

1.4e6

Inte

ns

ity

, c

ps

1.22

10.865.31

9.61

4.261.82 6.976.668.472.39 9.26

15.783.21 11.24 11.86 17.41 18.0316.6212.800.7713.475.15 8.19 19.0314.9410.41

7.343.94

HPLC/ICP-MS

HPLC/MS

CH2COOHBr

+ other low molecular weght compounds

Ozonation of primary and mixed-digested sludge: degradation products identification and degradation pathway

Ozonation of primary and mixed-digested sludge: toxicity of treated samples

Conclusions • Ozonation was effective in degrading brominated flame

retardant in both primary and mixed digested sludge;

• BDE-209 (the deca-brominated congener present at the

highest concentration in sewage sludge) showed a linear

degradation rate vs ozone dose;

• A fraction of transformed halogenated organics are

transferred to the aqueous phase (for mixed digested sludge

up to 41% at 0.105 gozone/gTSS);

• Ozonation leads to formation of polar organics that have a

good water solubility and, therefore, get partitioned

between the aqueous and the solid phase

Acknowledgment

This study is part of the EU ROUTES project “Novel

processing routes for effective sewage sludge

management” (Contract No 265156, FP7 2007-

2013) which has been financially supported by the

EU Commission within the THEME [ENV.2010.3.1.1-

2] Innovative system solutions for municipal sludge

treatment and management.

IRSA working team:

G. Mininni, V. Locaputo, R. Ciannarella

Elisabeth Richter, Anja Coors

ECT Oekotoxikologie GmbH, Flörsheim/Main, Germany

cnr istituto di ricerca sulle acque via f. de blasio, 5

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