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 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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