Impact of municipal solid waste landfill leachate loading on the performance of two wastewater treatment plants.

1. Impact of municipal solid waste
landfill leachate loading on the
performance of two wastewater
treatment plants.
Project: Dr Raymond Brennan (NUI Galway), Dr Eoghan Clifford and Dr Mark Healy.
Funding: EPA STRIVE Fellowship (No. 2013-W-FS-13).
15th International Waste Management and Landfill Symposium Sardinia 2015

2. Presentation
• Project background
• Description of study sites
– Landfill leachate
– Wastewater treatment plants
• Results of site-trials
• Conclusions
Leachate extraction point

3. Background – Irish context
• The Water Framework Directive has placed increasingly stringent
water quality emission limits on WWTPs, resulting in increased
costs associated with wastewater treatment.
• The establishment of Irish Water (a single utility company
responsible for water and wastewater infrastructure) has increased
pressure on all stakeholders to develop sustainable and cost
effective leachate treatment practices.
• Need for greater understanding of the effect of leachate loading on
WWTP performance.

4. Municipal solid waste leachate
produced at landfill
NoYes
WWTPReceiving water bodies
No Yes
Infiltration
NoYes
99 %
Is leachate collected?
23 % 76 % (4% sent for treatment at private treatment facilities before being
discharged to sewer)
9 % 14 %
.
Fate of MSW leachate in Ireland
Is leachate treated on-site?
Can be leachate be discharged at
the landfill?
Challenges/drivers for change!!!!
Increasingly stringent NH4-N and total
nitrogen effluent concentrations.
Management questions?

5. Presentation
• Project background
• Description of study sites
• Landfill leachate characterisation
• Wastewater treatment plants
• Results of site-trials
• Conclusions

6. Study sites
• Two landfill sites selected
• Two wastewater treatment plants
(WWTPs)
– Study site 1: LL1 % WWTP1
– Study site 2: LL2 % WWTP2
• Leachate loading regimes varied
depending on on-site practices
• “Young’’-landfills (operational or
<5 years closed)
– One operational and one closed

7. Study sites: Wastewater treatment
plants
Study site 1 Study site 2
Design P.E. PE 2,000 25,000
Operating P.E. 5,000 19,000
Leachate entry point Aeration tank Sewer
Leachate pretreatment at WWTP
(before entering works) None None
Annual volume leachate accepted m3/year 7,302 47,744
% 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
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8. Landfill leachate composition
Leachate 1 Leachate 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-1
6840-6870 6855 21 3117-4578 3803 735
Ammonia mg 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
Chloride mg L-1 130-201 163 36 160-371 290 114
Sulphate mg L-1 109-320 210 106 7.2-93 43 45
Suspended solids mg L-1 12-89 44a 40 45-126 79a 42
While leachates originate from young landfills have properties typical of older
leachate (BOD:COD <0.32)

9. Leachate 1 Leachate 2 Sig.
Nitrification
inhibiting
Range Mean St. D. Range Mean St. D.
Arsenic µg L-1 28-35 32 4 11-27 18 8 0.05 40-100
Barium µg L-1 497-1027 830 290 434-674 550 120 0.05
Boron mg L-1 2-3.6 3.05 1 0.86-1.42 1.14 0 ns
Cadmium µg L-1 0.1-0.7 0.5 0 0.1-0.3 0.23 0 ns 1000
Chromium µg L-1 50-113 87 33 33-87 55 28 0.05 1000
Copper mg L-1 0.012-0.157 0.07 0 0.003-0.024 0.02 0 ns 0.1-0.35
Iron µg L-1 2031-5621 3870 1797 2376-3637 3071 640 0.05
Lead µg L-1 3.1-7.8 4.9 3 0.6-6 2 3 ns 500
Mercury µg L-1 0.03-0.18 0.11a 0 0.06-0.07 0.06a 0 0.05 100-250
Nickel µg L-1 22-61 46.7a 22 25-39 32 a 7 0.05 250-500
Sodium mg L-1 367-577 447a 113 243-377 309a 67 0.05
Landfill leachate metals

10. Presentation
• Project background
• Description of study sites
• Landfill leachate
• Wastewater treatment plants
• Results of site-trials
• Conclusions
Auto samplers in-situ

11. Study site 1Influent monitoring
head of works
Leachate storage tank
120 m3 capacity
Leachate 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)
sudden loading.

12. Site 1: Effluent concentrations
0
20
40
60
80
100
120
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
BOD COD TICf TOCf
EffluentconcentrationsmgL-1
Carbon Nitrogen
0
10
20
30
40
50
60
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
Drip
No
Shock
TNf NH4-N NO3-N NO2-N
Note: Different scale for carbon and nitrogen concentrations

13. 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
Site 1: WWTP performance
• No significant in NH4-N effluent concentrations were observed.
• However, NH4-N concentration exceeded 1 mg L-1 emission limit
values (ELV) for the receiving freshwater stream.
• Currently no total nitrogen ELV, therefore not in exceedances.

14. Drip-feed No leachate Shock loading
Effluentammonium(mgN/L)
Site 1: NH4-N trends
> ELVs < ELVs

15. Study Site 2
Leachate pumped via
rising main from landfill
- controlled by leachate levels
Auto sampler monitoring plant
performance

16. Site 2: Effluent concentrations
0
20
40
60
80
100
120
140
160
High Low High Low High Low High Low
BOD COD TICf TOCf
EffluentconcentrationsmgL-1
0
10
20
30
40
50
60
70
High Low High Low High Low High Low
TNf NH4-N NO3-N NO2-N
NitrogenCarbon
Note: Different scale for carbon and nitrogen concentrations

17. 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 %
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
Site 2: WWTP performance
• Leachate acceptance did not effect BOD and COD removals.
• Decreasing leachate loading decreased effluent NH4-N load (did not
exceed 10 mg L-1 ELV during monitoring period).

18. High leachate loading Low leachate loading
EffluentNH4-N(mgL-1)
0
2
4
6
8
10
12 9/11/2014
9/12/2014
9/13/2014
9/14/2014
9/15/2014
9/16/2014
9/17/2014
9/18/2014
9/19/2014
9/20/2014
9/21/2014
9/22/2014
9/23/2014
9/24/2014
9/25/2014
9/26/2014
Site 2: NH4-N trends
< ELVs

19. WWTP leachate loadings expressed
as a percentage of WWTP effluent
W
W
T
P
Reg.
Volume
wastewater
Volume leachate
treated per
day/volume of
wastewater treated
per day
Volume leachate
treated per
day/volume of
wastewater treated
during leachate
discharge period
m3 % %
1 Drip-feed (24 hours) 2,040 0.9 0.9
No leachate 2,470 0.0 0.0
Shock load (2 hour discharge to
aeration tank)
2,400 0.9 34
2
Shock high (2 hour discharge to
sewer)
6,450 2.4 36
Shock low (2 hour discharge to
sewer)
6,210 0.3 17
• Irish EPA recommended value: leachate loading less than 4% of
wastewater influent at any time.
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20. Presentation
• Project background
• Description of study sites
• Landfill leachate
• Wastewater treatment plants
• Results of site-trials
• Conclusions

21. Conclusions
• Hydraulic loading-based acceptance not always
appropriate (in agreement with international literature).
• Increasingly stringent ELVs may represent a threat to the
sustainability of co-treatment in Ireland.
• WWTPs co-treating leachate may need be equipped with
nitrogen removal capacity.

22. Grazie per l’attenzione.

23. Please feel free to contact me if you have any
queries: raymond.brennan@nuigalway.ie