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: raymond.brennan@nuigalway.ie

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: raymond.brennan@nuigalway.ie

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)