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:

raymond.brennan@nuigalway.ie; 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.