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

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.

Presentation Overview• Background

• Landfill leachate management practices, volumes and concentrations in Ireland.

• Impact of landfill leachate loading on municipal WWTP performance.

• Conclusions and Recommendations.

Background

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0

50

100

150

200

Num

ber o

f ope

n la

ndfil

ls

in th

e R

epub

lic o

f Ire

land

1994Commencement

of ICP/IPPC licence

1997Commencement of waste licencing

2001Landfill Directive (1999/31/EC) implemented

2010Target for 75% reduction in BMW compared to 1995 base level

Landfill Directive (1999/31/EC) implementation schedule

Urban Waste Water Treatment Regulations

1994Implementation of

Urban Waste Water Treatment Regulations

(S.I. No. 419/1994)

2001(S.I. No. 254/2001)

2007(S.I. No.

254/2001)

PresentIncreasingly stringent emission

limit values targeting WWTPs in sensitive catchments

1985

1986

1987

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1997

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1999

2000

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2003

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2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

0100200300400500600700800

Composting and digestionIncineration / energy recoveryMaterial recyclingDeposit onto or into land

Year

Mun

icip

al w

aste

(kg

per c

aptia

)

Landfilling

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?

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

Presentation Overview• Background

• Landfill leachate volumes, concentrations and trends in Ireland.

• Impact of landfill leachate loading on municipal WWTP performance.

• Conclusions and Recommendations.

Landfill leachate volumes, concentrations and trends in

Ireland.

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.

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

Mon

thly

vol

ume

leac

hate

co

llect

ed/a

nnua

l vol

ume

colle

cted

Results: leachate compositionP

aram

eter

(mg

L-1)

You

ng

Inte

rmed

iate

Old

You

ng

Inte

rmed

iate

Old

You

ng

Inte

rmed

iate

Old

You

ng

Inte

rmed

iate

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

Leachate generation rates and trends in MSW landfills examined

0 5 10 15 20 250.0

0.5

1.0

1.5

2.0

2.5

3.0

3.51994 (in)

1997 (yb)2001 (y)

2002 (y)

2003 (y)2005 (y)

2008 (y)

Time (years after opening)

m3 l

each

ate

prod

uced

for t

onne

of

was

te la

ndfil

led

• 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

Time (years after opening)

0 5 10 15 20 250

2000

4000

6000

8000

10000

12000

1994 (in)

2005 (y)

2008 (y)

2001 (y)

2003 (y)

2005 (yd)

y: young leachate, in: intermediate age leachate;b: waste baled before landfilling

NH

4-N

(mg

L-1)

Leachate loading rates at WWTPsP

erce

ntag

e (%

)

Per

cent

age

(%)

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

Per

cent

age

(%)

Per

cent

age

of t

otal

vo

lum

e/m

ass

load

ing

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!

Presentation Overview• Background

• Landfill leachate volumes, concentrations and trends in Ireland.

• Impact of landfill leachate loading on municipal WWTP performance.

• Conclusions and Recommendations.

Impact of landfill leachate loading on municipal WWTP

performance.

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

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 SewerLeachate 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

Landfill leachate compositionLeachate 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-16840-6870 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.

Study site 1Influent monitoring head of works

Leachate storage tank 120 m3 capacityLeachate 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.

WWTP 1: Effluent concentrationsDr

ip No

Shoc

k

Drip No

Shoc

kDr

ip No

Shoc

k

Drip No

Shoc

k

BOD COD TICf TOCf

0

10

20

30

40

50

60

70

80

Effl

uent

con

cent

ratio

ns m

g L-1

Carbon Nitrogen

Drip No

Shoc

k

Drip No

Shoc

k

Drip No

Shoc

k

Drip No

Shoc

k

TNf NH4-N NO3-N NO2-N

0

5

10

15

20

25

30

35

40

45

Note: Different scale for carbon and nitrogen concentrations

BOD5 NH4-N NO3-N NO2-N

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).

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.

WWTP 2: Effluent concentrations

High Low High Low High Low High LowBOD COD TICf TOCf

0

20

40

60

80

100

120

Effl

uent

con

cent

ratio

ns m

g L-1

High Low High Low High Low High LowTNf NH4-N NO3-N NO2-N

0

10

20

30

40

50

60

NitrogenCarbon

Note: Different scale for carbon and nitrogen concentrations

BOD5 NH4-N NO3-N NO2-N

Regime Volume BOD(kg day-1)

COD(kg day-1)

TN (kg day-1)

NH4-N (kg day-1)

Unitsm3 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).

WWTP leachate loadings expressed as a percentage of WWTP load

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

0

10

20

30

40

50

60

70

80

90

100Volumetric

BOD

COD

TN

NH4-N

Leachate loading regime (leachate discharge time (hours))

Per

cent

age

of to

tal W

WTP

load

(%

)

BOD5

NH4-N

Presentation Overview• Background

• Landfill leachate volumes, concentrations and trends in Ireland.

• Impact of landfill leachate loading on municipal WWTP performance.

• Conclusions and Recommendations.

Conclusions and Recommendations.

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.

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.

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.

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.