Background Internationally, there are on-going cases of
groundwater and/or local environment pollution as
a result of poor landfill leachate management. In
Ireland, 95% of municipal solid waste (MSW) landfill
leachate (approximately 1.1 million cubic meters
produced annually) 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 has
increased pressure on all stakeholders to develop
sustainable and cost effective 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.
R. Brennan1*, E. Clifford1, L. Morrison2, S. Hynes3, D. Norton3, M. Healy1
1Civil Engineering, National University of Ireland, Galway, Ireland; 2Earth and Ocean Sciences, NUI Galway, Ireland; 3Socio-
Economic Marine Research Unit, J.E. Cairnes School of Business and Economics, NUI Galway, Ireland. *Presenting author. E:
[email protected]; W: http://www.nuigalway.ie/leachate/; T: https://twitter.com/LeachateNUIG
Methodology
• Three activated sludge WWTPs with different
population equivalents, receiving leachate from
different landfill types (lined or unlined) at different
loading regimes (i.e. drip-feed versus shock loading),
were selected and monitored for between 10 and 50
days depending on plant performance.
• Wastewater samples were taken at eight-hour
intervals at the head of the works and effluent
discharge points for the duration of the study.
Influent and effluent flow was also recorded for the
duration of the study. Samples were analysed for
BOD5, COD, total nitrogen, dissolved phosphorus,
nitrate, nitrite, ammonium (NH4-N) and total
suspended solids.
• Grab samples of leachate being accepted at each
WWTP were taken and analysed for NH4-N, BOD5,
COD, cyanide, arsenic, copper, lead, mercury, nickel
and zinc.
Results and Conclusions • Landfill leachate can be treated using conventional
activated sludge WWTPs. However, leachate
acceptance may pose a risk of elevated NH4-N effluent
concentrations. Current best management practice in
Ireland is to ensure that <4% by volume of influent of
leachate enters the plant. The current study supports
these findings. There is also an argument for an NH4-
N-based loading limit to be used. In the case of one
WWTP, leachate NH4-N was equal to 21.8% of the total
load and only represented 0.4% of hydrological load.
Landfill leachate samples analysed as part of the study.
Automated samplers used to collect samples at the head of aeration tanks.
Leachate is typically drip-fed into the aeration tanks such as this one.
Objective This study was conducted to examine the impact of
landfill leachate on WWTP performance at field-scale
in three operating WWTPs.
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