Landfill leachate in Ireland: A legacy problem

1. Landfill leachate in Ireland: A
legacy problem
Presented in partnership with Engineers Ireland West Division.
Project team: Raymond Brennan, Eoghan Clifford, Mark Healy, Liam Morrison, Stephen Hynes
and Daniel Norton.
Funding: EPA Research Code (No. 2013-W-FS-13).
Date: 8th February 2016

2. Objectives:
1. Examine landfill leachate management practices in Ireland.
2. To conduct a technical review of leachate volumes,
concentrations and treatability in Ireland.
3. To examine the co-treatment of leachate in municipal
wastewater treatment plants (WWTPs) and attempt to
quantify the maximum hydraulic and mass nitrogen loading
rates above which the performance of a WWTP may be
inhibited.

3. Presentation Overview
• Background
• Landfill leachate management practices, volumes and
concentrations in Ireland.
• Impact of landfill leachate loading on municipal WWTP
performance.
• Conclusions and Recommendations.

4. Background

5. 0
50
100
150
200
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
Numberofopenlandfills
intheRepublicofIreland
1994
Commencement
of ICP/IPPC
licence
1997
Commencemen
t of waste
licencing
2001
Landfill Directive
(1999/31/EC)
implemented
2010
Target for 75% reduction in BMW
compared to 1995 base level
Landfill
Directive
(1999/31/EC)
implementation
schedule
Urban Waste
Water
Treatment
Regulations
1994
Implementation of
Urban Waste Water
Treatment Regulations
(S.I. No. 419/1994)
2001
(S.I. No. 254/2001)
2007
(S.I. No.
254/2001)
Present
Increasingly stringent emission
limit values targeting WWTPs in
sensitive catchments
0
100
200
300
400
500
600
700
800
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
Municipalwaste(kg
percaptia)
Year
Composting and digestion
Incineration / energy recovery
Material recycling
Deposit onto or into landLandfilling

6. Municipal solid waste leachate
produced at landfill
NoYes
WWTPReceiving water bodies
No Yes
Infiltration
NoYes
99 %
Is leachate collected?
23 % 77 % (4% sent for treatment at private treatment facilities before being
discharged to sewer)
9 % 14 %
.
Where does the leachate go?
Is leachate treated on-site?
Can treated leachate be
discharged at the landfill?
Challenges/drivers for change!!!!
• Need to analyse existing treatment
practices for both environmental and
cost reasons.
• 1.4 million m3 of leachate collected
annually.
Management questions?

7. Landfill leachate classification
Young Intermediate Old
Age (years landfill closed) <5 5-10 >10
COD >10,000 4000-10,000 <4000
BOD5:COD ratio >0.3 0.1-0.3 <0.1
Landfill leachate samples collected as part of characterisation study

8. Presentation Overview
• Background
• Landfill leachate volumes, concentrations and trends in
Ireland.
• Impact of landfill leachate loading on municipal WWTP
performance.
• Conclusions and Recommendations.


9. Landfill leachate volumes,
concentrations and trends in
Ireland.

10. Methodology
• Surveyed landfill and WWTP operators.
• Collected data from 48 landfills exporting landfill leachate to
WWTPs for treatment.
• Collected data from 33 WWTPs co-treating landfill leachate.

11. Results: leachate volumes
• Monthly volume leachate exported as a ratio of annual volume of
leachate exported.
• Landfill leachate volumes were observed to vary by a factor of three
between summer (low) and winter (high) vary on average.
Young landfill Old landfills
Monthlyvolumeleachate
collected/annualvolumecollected

12. Results: leachate composition
Parameter(mgL-1
)
Young
Intermediate
Old
Young
Intermediate
Old
Young
Intermediate
Old
Young
Intermediate
Old
COD BOD5 NH4-N Choride
Typical wastewater
strength
COD (mg L-1) BOD5 (mg L-1) NH4-N (mg L-1)
Low 250 110 12
Med 430 190 25
High 800 350 45

13. Leachate generation rates and
trends in MSW landfills examined
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 5 10 15 20 25
1994 (in)
1997 (yb)
2001 (y)
2002 (y)
2003 (y)
2005 (y)
2008 (y)
Time (years after opening)
m3leachateproducedfortonneof
wastelandfilled
• General decrease in the volume of leachate produced per tonne
of waste landfilled in newer landfills.
• This is a result of a combination of increased landfill size and
improved leachate management practice
y: young leachate,
in: intermediate age
leachate;
b: waste baled
before landfilling

14. Time (years after opening)
0
2000
4000
6000
8000
10000
12000
0 5 10 15 20 25
1994 (in)
2005 (y)
2008 (y)
2001 (y)
2003 (y)
2005 (yd)
y: young leachate,
in: intermediate age
leachate;
b: waste baled
before landfilling
NH4-N(mgL-1)

15. Leachate loading rates at WWTPs
Percentage(%)
Leachate volume of
total WWTP effluent
Leachate BOD of
total WWTP influent
BOD
Leachate COD of total
WWTP influent COD
Leachate NH4-N of total
WWTP influent total
nitrogen
Percentage(%)
Leachate volume of
total WWTP effluent
Leachate BOD of
total WWTP influent
BOD
Leachate COD of total
WWTP influent COD
Leachate NH4-N of total
WWTP influent total
nitrogen
Percentage(%)
Leachate volume of
total WWTP effluent
Leachate BOD of
total WWTP influent
BOD
Leachate COD of total
WWTP influent COD
Leachate NH4-N of total
WWTP influent total
nitrogen
Percentageoftotal
volume/massloading
Challenge:
1. Current practice is to ensure
leachate loading < 4% on
volumetric basis.
2. Many WWTPs accept leachate
and determine treatment cost
based on volumetric, BOD and
COD loadings.
3. Need to examine the impact of
leachate loading on WWTP
performance!

16. Presentation Overview
• Background
• Landfill leachate volumes, concentrations and trends in
Ireland.
• Impact of landfill leachate loading on municipal WWTP
performance.
• Conclusions and Recommendations.



17. Impact of landfill leachate loading
on municipal WWTP
performance.

18. Study WWTPs: Loading regime
WWTP identifier WWTP 1 WWTP 2
Operating P.E. 2,000 19,000
Nitrogen removal None None
Leachate entry point Aeration tank Sewer
Leachate pre-treatment None None
Leachate loading regimes
examined (daily leachate
loading m3d-1)
Drip-feed (37 m3d-1) Shock high (166 m3d-1)
No-leachate Shock low (29 m3d-1)
Shock (38 m3d-1)
Discharge time
Drip-feed (24hr);
Shock (2hr)
4 hr

19. Study WWTPs: Loading rates
WWTP 1 WWTP 2
Design P.E. PE 5,000 25,000
Operating P.E. 2,000 20,000
Leachate entry point Aeration tank Sewer
Leachate pretreatment at WWTP
(before entering works) None None
Annual volume leachate accepted m3/year 7,000 50,000
% leachate volume of total effluent
(4% recommended maximum) % 1.17 2.3
% BOD of WWTP BOD loading % 0.58 0.6
% COD of WWTP COD loading % 4.4 0.6
% NH4-N of WWTP Total nitrogen
loading % 33 3.4
 

20. Landfill leachate composition
Leachate 1 (WWTP 1) Leachate 2 (WWTP 2)
Range Mean St. D. Range Mean St. D.
pH pH 6.8-7.8 7.3 1 7.8-8 8 0.12
Conductivity µs cm-1
6840-6870 6855 21 3117-4578 3803 735
Ammonium mg N L-1 245-378 311a 67 120-246 183a 89
Total nitrogen mg L-1 279-429 351a 75 130-380 253a 130
BOD mg L-1 8-20 14 6 100-700 396 300
COD mg L-1 274-420 361a 77 698-2190 1362 759
BOD/COD 0.03-0.05 0.04 0.01 0.14-0.32 0.26 0.1
Alkalinity mg L-1 10-1083 547 759 1306-1918 1554 322
Nitrification inhibiting elements including arsenic, barium, boron, cadmium,
chromium, copper, iron, lead, mercury were not present in concentrations
which would inhibit WWTP processes.

21. Study site 1Influent monitoring
head of works
Leachate storage tank
120 m3 capacity
Leachate continuously drip-fed to
head of aeration tank
Effluent
monitoring
outlet of works
Aeration
tanks
Refrigerated auto samplers used to
take grab samples ever 8 hours
The plant can receive
up to 300 m3 of
leachate a week during
peak flows (winter
months).
There were three
distinct leachate
loading regimes during
the monitoring period:
(1) drip-feed (normal
working conditions),
(2) No-leachate and (3)
shock loading.

22. WWTP 1: Effluent concentrations
0
20
40
60
80
100
120
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
BOD COD TICf TOCf
EffluentconcentrationsmgL-1
Carbon Nitrogen
0
10
20
30
40
50
60
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
TNf NH4-N NO3-N NO2-N
Note: Different scale for carbon and nitrogen concentrations
BOD5 NH4-N NO3-N NO2-N

23. Regime Volume BOD
(kg day-1)
COD
(kg day-1)
TN
(kg day-1)
NH4-N
(kg day-1)
Units m3 Inf Eff % Inf Eff % Inf Eff % Inf Eff %
Drip-feed
2040 545 2 99 862 68 91 36 42 -21 35 2 97
No-
leachate
2470 512 9 97 905 97 88 40 30 17 40 3 96
Shock
load
2400 635 7 99 803 75 90 45 49 -8 45 3 94
WWTP 1: WWTP performance
• No significant increase in NH4-N effluent concentrations were
observed.
• For all cases (including no-leachate) the plant struggled to meet
NH4-N emission limit values for WWTP (1 mg NH4-N L-1).

24. Study Site 2
Leachate pumped via
rising main from landfill
- controlled by leachate levels
Auto sampler monitoring plant
performance
There were two
distinct leachate
loading regimes during
the monitoring period:
(1) shock-high and (2)
shock-low loading.

25. WWTP 2: Effluent concentrations
0
20
40
60
80
100
120
140
160
High Low High Low High Low High Low
BOD COD TICf TOCf
EffluentconcentrationsmgL-1
0
10
20
30
40
50
60
70
High Low High Low High Low High Low
TNf NH4-N NO3-N NO2-N
NitrogenCarbon
Note: Different scale for carbon and nitrogen concentrations
BOD5 NH4-N NO3-N NO2-N

26. Regime Volume BOD
(kg day-1)
COD
(kg day-1)
TN
(kg day-1)
NH4-N
(kg day-1)
Units
m3 Inf Eff % Inf Eff % Inf Eff % Inf Eff %
Shock-high 6450 1926 146 91 3742 394 88 238 174 20 200 30 84
Shock-low 6210 1069 71 94 4082 270 93 217 149 29 191 4 98
WWTP 2: WWTP performance
• Leachate acceptance did not effect BOD and COD removals.
• Increased leachate loading increased effluent NH4-N load (did not
exceed 10 mg L-1 ELV during monitoring period).

27. WWTP leachate loadings expressed as
a percentage of WWTP load
0
10
20
30
40
50
60
70
80
90
100
Drip-feed
(24 hr)
Shock (24
hr)
Shock (1
hr)*
Shock high
(24 hr)
Shock high
(4 hr)*
Shock low
(24 hr)
Shock low
(4 hr)*
WWTP 1 WWTP 2
PercentageoftotalWWTPload(%)
Leachate loading regime (leachate discharge time (hours))
Volumetric
BOD
COD
TN
NH4-N
BOD5
NH4-N

28. Presentation Overview
• Background
• Landfill leachate volumes, concentrations and trends in
Ireland.
• Impact of landfill leachate loading on municipal WWTP
performance.
• Conclusions and Recommendations.




29. Conclusions and
Recommendations.

30. Conclusions
• The implementation of EU Directives has resulted in
significant advances in landfill management and protection of
the environment from the adverse effect of landfilling.
• Increasingly stringent WWTP emission limits represent a
significant challenge to the co-treatment of leachate with
municipal wastewater.
• The seasonal variation in leachate production poses a risk to
effective co-treatment in municipal WWTPs, as periods of
high leachate production coincide with periods of maximum
hydraulic loading in WWTPs.

31. Conclusions (Continued)
• Leachate loading regimes examined were found to be appropriate for
effective treatment landfill leachate in the WWTPs examined.
• Hydraulic loading-based acceptance criteria recommendations are
not appropriate when co-treating young leachate with municipal
wastewater.
• Site-specific inhibition experiments may be necessary to determine
appropriate loading rates.
• Nitrogen loading should be considered when estimating the cost of
leachate treatment.

32. Recommendations
• The current practice of co-treatment of landfill leachate at WWTPs is
appropriate in most circumstances.
• Leachate storage infrastructure at the landfill and WWTPs accepting
leachate should be sufficient to minimise the risk of overloading
WWTPs.
• Ammonium loading based tariffs should be implemented to give
certainty to landfill operators considering the installation of on–site
leachate treatment systems.
• Landfill managers should be encouraged to work together to avoid
duplication of efforts and to optimise resources.

33. Thank you
• Project team: Raymond Brennan, Eoghan Clifford, Mark Healy, Liam Morrison, Stephen
Hynes and Daniel Norton.
• For more information:
– Project website (http://www.nuigalway.ie/leachate/)
– Twitter account (https://twitter.com/LeachateNUIG).
– Project newsletters and previous presentations are available on Slideshare.
• Acknowledgements
– Thanks to the EPA for providing funding for the project.
– Special thanks to all WWTP, landfill, EPA, Irish Water and Local Authority staff for their
time and support throughout this project.