Screenings and grit production from Portuguese WWTP

E. S. Varela1, M. T. Santos2, A. M. Barreiros2

1 -Área Departamental de Engenharia Civil, 2 -Área Departamental de Engenharia Química

ISEL - Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa,

WWTP

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Beirolas WWPT

Minimizeenvironmental impact

by-products are generated• Screenings• Grit • Sludge’s

Screenings and grit

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Beirolas WWPT

Wastes under the European List of Waste

Commission Decision 2000/532/EC and Commission Decision 2014/955/EU

Screenings 19 08 01

Grit 19 08 02

Sludge 19 08 05

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Screenings and grit

Screen equipment

Grit removal

GritScreenings

Preliminary treatment

Final Disposal

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Screenings

Grit Landfill

What we do with these waste?

But it is necessary to pay for landfilling!

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Screenings

Grit

Directive nº 2008/98/CE

Waste management hierarchy

What is recommended by the good

environmental practices?

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Screenings

Grit

There are already some

solution!

• Screenings - biological treatment by composting or anaerobic digestion

• Grit - valorised through their use in construction

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Screenings

Grit

To implement an adequate treatment it is important to know the

quantity and qualityThe best way to predict the amount of waste is taking into account the historical WWPT data.

Some facts!

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58

79

0

10

20

30

40

50

60

70

80

90

100

2002 2006 2007 2008 2009 2011 2012

% P

opol

atio

n se

rved

Year

Collected WWT

Portugal A significant growth in municipal WWT

Some facts!

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There are a significant number of WWPT -2,536 WWPTwith different dimensions and configurations

The available data is sparse and spread over many sources

There are 283 ME

e.g. SIMTEJO - WWTP ranges from 80 to 140,000 m3d-1

Methodology

• Financial statements and other legal reports of Portuguese ME

• Specific surveys sent to 20 ME• Served population• Wastewater flow treated • Screenings and grit productions

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≈ 86% population served by WWTP

PortugalScreenings and grit

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0

1

2

3

4

5

6

7

0

100

200

300

400

500

2009 2010 2011 2012 2013

Popu

latio

n (m

illio

n in

hab.

)

Flow

(m

illio

n m

3 .yea

r -1)

Year

Flow Population

Águas de Santo André, Águas de Trás-os-Montes e Alto Douro, Águas de Zêzere e Côa, Águas do Algarve, Águas do Noroeste, Águas do Oeste, Águas do Sado, SANEST, SIMARSUL, SIMDOURO, SIMRIA, SIMTEJO, SMAS Caldas da Rainha.

13 answers - but only 8 of MEPopulation served by WWT - 62%.

2013Population - 5,832,830 Flow - 439,555,000 m3

Screenings and grit

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2013Screening - 5,659 ton Grit - 7,869 ton

2013Population - 5,832,830 Flow - 439,555,000 m3

0123456789

10

2009 2010 2011 2012 2013

Qua

ntity

(tho

usan

d to

n)

Year

screenings grit

Per capita values

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0

50

100

150

200

250

0

1

2

3

4

5

6

7

2009 2010 2011 2012 2013

Was

tew

ater

per

cap

ita v

alue

s

(L.in

hab-1

.d-1

)

Was

tes p

er c

apita

val

ues

(g

.inha

b-1.d

-1)

Year

Grit Screenings WW (grit) WW (screenings)

Screenings and grit

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Portugal, 2013Productions may be estimated

The screenings - 8,495 ton The screenings and grit - 12,256 ton

The amount of screenings and grit depend:• WWTP number, • Treatment technologies, • Lifestyle,• The sewer systems

Per capita value

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Grit Screening

0,0

2,0

4,0

6,0

8,0

10,0

12,0

14,0

16,0

ME 1 ME 2 ME 3 ME 4 ME 5 ME 6 ME 7

Grit

per

cap

ita v

alue

s (g

.inha

b-1.d

-1)

2009 2010 2011

0,0

1,0

2,0

3,0

4,0

5,0

ME 1 ME 2 ME 3 ME 4 ME 5 ME 6 ME 7Sc

reen

ings

per

cap

ita v

alue

s(g

.inha

b-1.d

-1)

2009 2010 2011

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Waste produce in 2013

• per capita values of each MEScreenings - 5,189 - 11,987 ton Grit - 7,353 - 26,734 ton

• per capita values of an average of 13 MEScreenings - 8,495 ton Grit - 12,256 ton

Screenings and grit

SIMTEJO

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Alcântara WWTP

Chelas WWTP

Beirolas WWPT

SIMTEJO

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Alcântara Beirolas ChelasProject Population (ep)

756,000 213,500 211,000

Population (2012) (ep)

531,146 177,207 139,349

Project flow (m3.d-1)

140,000 54,500 52,500

Flow (m3) (2013) 53,708,041 16,971,070 14,177,553Screenings removal

remove solids > 6 mm remove solids > 6 mm remove solids > 6 mm

Grit removal Aerated grit and grease removal

Aerated grit and grease removal

Aerated grit and grease removal

Final disposal Landfilling Landfilling Landfilling

SIMTEJOScreenings and grit

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0

1

1

2

2

3

2007 2008 2009 2010 2011 2012 2013

Qua

ntity

(tho

usan

d to

n)Year

Screenings Grit

0

200

400

600

800

1.000

0102030405060708090

2007 2008 2009 2010 2011 2012 2013Po

pula

tion

(tho

usan

d in

hab)

Flow

(mill

ion

m3 .y

ear-1

)

Year

Flow Population

SIMTEJOScreenings and grit

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0

2

4

6

8

10

12

14

2007 2008 2009 2010 2011 2012 2013G

ritpe

r cap

itava

lues

(g-in

hab-1

.d-1

)Year

Alcântara Beirolas Chelas

0

1

2

3

4

5

6

2007 2008 2009 2010 2011 2012 2013

Scre

enin

gs p

er c

apita

val

ues

(g-in

ha-1

.d-1

)

Year

Alcântara Beirolas Chelas

Wastes removal equipment was identical but

Different per capita wastes productions

Screenings Grit

Precipitation in Lisbon

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0

500

1000

1500

2000

050

100150200250300350400

2007 2008 2009 2010 2011 2012 2013

Prec

ipita

tion

(mm

)

WW

per

cap

ita

(L.d

-1.in

ab--1

)

Year

Alcântara Beirolas Chelas Precipitation

0

20

40

60

80

100

120

0123456789

Prec

ipita

tion

(mm

)

Flow

( th

ousa

nd m

3 .mon

th-1

)

Month

Flow Precipitation

2010

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0

20

40

60

80

100

120

050

100150200250300350400

Jan Fev Mar Abr May Jun Jul Aug Set Out Nov Dez

Prec

ipita

tion

(mm

)

Grit

(ton

)

Month

Alcântara Beirolas Chelas Precipitation

0

20

40

60

80

100

120

0

10

20

30

40

50

60

Jan Fev Mar Abr May Jun Jul Aug Set Out Nov Dez

Prec

ipita

tion

(mm

)

Scre

enin

gs (t

on)

Month

Alcântara Beirolas Chelas Precipitation

Precipitation in Lisbon

Screening and grit disposal

• Data collected from the surveys demonstrate that most of the wastes are sent to landfill.

• The estimated cost of landfilling (2013) were: • screenings ≈ 272,000 €• grit ≈ 392,000 €

• It can mean an immediate saving of about 0.2% in WWT costs by cubic meter

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Screening and grit disposal

The screenings and grit valorisation has manyenvironmental and economic advantages:• Reduction the associated costs with screening and

grit final disposal;• Reducing the amount of waste sent to

landfill, complying with legal guidelines;• Reducing the amount of extracted

aggregates, promotes the sustainable use ofresources;

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Conclusion

Estimate values of wastes production from WWPT was difficult to predict

Production in Portugal:5,189 - 11,987 ton to screenings 7,353 - 26,734 ton to grit

The current final disposal of screenings and grit in Portugal is landfills. it is possible to value and reuse screenings and grit is necessary to invest in training and environmental

awareness campaigns

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Acknowledgements

We thank to the several wastewater entities in providing thescreenings and grit productions data.

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And

Would like to thank all of you for your kindly attention – thank you