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Internationally, there are on-going cases of groundwater and/or lo-
cal environment pollution as a result of poor landfill leachate man-
agement. In Ireland 95% of municipal solid waste (MSW) landfill
leachate (approximately 1.1 million cubic meters produced annual-
ly) is sent to municipal waste water treatment plants (MWWTPs) for
final treatment. In recent years the Water Framework Directive has
placed increasingly stringent water quality emission limits on
MWWTPs resulting in increased costs associated with wastewater
treatment. The establishment of Irish Water Ltd has increased pres-
sure on all stakeholders to develop sustainable and cost effec-
tive leachate treatment practices. Landfills can generate leachate
for over 30 years after waste ceases being deposited in the landfill
and leachate management is set to be a problem in Ireland for many
years to come.
In order to address this problem the project team are first charac-
terizing the leachates and surveying landfill and MWWTP managers.
Following this onsite trials are being conducted at MWWTPs to de-
velop guidelines.
Introduction
Treatment of landfill leachate by municipal
wastewater treatment plants.
Contact: [email protected]
01/February/2015
Issue 1
Funding agency: EPA STRIVE Fellow-
ship (No. 2013-W-FS-13).
Project duration: Dec. 2013—Dec.
2015
Website: http://www.nuigalway.ie/leachate/
Twitter: https://twitter.com/LeachateNUIG
1. Waste deposited in active cell.
2. Temporary Geohess liner which signifi-
cantly reduces leachate generation while
the landfill is settling.
3. Final capping which comprises imper-meable LLDPE liner with subsoil and top-soil placed over.
(Photos 1,2 and 3 courtesy Westmeath CoCo)
Project aims
As there is a need for research which provides the scientific, engi-
neering, regulatory and policy stakeholders with clear evidence-
based guidance on leachate management options, this project aims
to develop guidelines for treatment of landfill leachate by:
1. Characterization of landfill leachate from open and closed
sites.
2. Monitor the impacts of landfill leachate acceptance on
MWWTP performance.
3. Evaluate the cost effectiveness on-site treatment versus off-
site treatment of landfill leachate.
Project team
Raymond Brennan (Project Manager), Eoghan Clifford, Mark Healy,
Liam Morrissey, Steve Hynes and Daniel Norton.
Landfilling sequence of events:
Results
Contact: [email protected]
Leachate characterization study
Findings to date
Leachate samples were collected monthly from six landfill sites.
Closed and operational sites were selected to capture the range of
leachate concentrations which occur in Ireland. Samples are ana-
lyzed for a range of wastewater strength parameters including am-
monium, biochemical oxygen demand (BOD5) and chemical oxygen
demand (COD). In addition samplers were analyzed for known nitri-
fication inhibition compounds such as free-cyanide, total-arsenic, -
copper, -lead, -nickel, and -zinc.
Landfill leachate strength can vary considerably depending on site hydrology, landfill lining, landfill capping, age of landfill and material deposited at the landfill.
In practice drip-feed systems have been widely used at MWWTPs to minimize the impacts of landfill leachate on MWWTP performance. Future work will examine this more closely.
There is wide variation in the strength of leachate in Ireland. The average ammonium, cyanide and zinc concentrations were above levels which have been shown to inhibit nitrification in activated sludge systems. In addition maximum arsenic, copper and lead con-centrations were above nitrification inhibition levels.
4. Landfill collection sump - leachate is
pumped from base of landfill to surface
lagoon.
6. Automated samplers used to collect
samples at the head of aeration tanks.
7. Leachate is typically drip-fed into the
aeration tank at the WWTP.
5. Landfill leachate samples analysed as
part of the leachate characterisation
study.
Parameter Units Average Standard
Deviation
Min. Max. Nitrification
inhibiting con-
centration*
Ammonium mg/l 597 725 38 3,150 480
BOD5 mg/L 173 203 16 618
COD mg/L 1,550 1,610 110 7,450
BOD5/COD none 0.20 0.36 0.03 0.99
Cyanide µg/L 144 195 6 1,070 100-5,000
Arsenic µg/L 90 109 2 402 100
Copper mg/L 0.21 0.46 0.003 2.423 1
Lead µg/L 39 176 0.3 1,050 100-5,000
Nickel µg/L 124 146 0.5 661 1000-2,500
Zinc µg/L 325 1,279 10 7,640 300-5,000
*Concentration above which parameter has been shown to inhibit nitrification (Environmental Pro-
tection Agency, 1997; Henze, 2002)