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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
Presentation• Project background
• Description of study sites– Landfill leachate– Wastewater treatment plants
• Results of site-trials
• ConclusionsLeachate extraction point
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.
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?
Presentation• Project background
• Description of study sites• Landfill leachate characterisation• Wastewater treatment plants
• Results of site-trials
• Conclusions
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
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 SewerLeachate 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
Landfill leachate compositionLeachate 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-16840-6870 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)
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 nsCadmium 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
Presentation• Project background
• Description of study sites• Landfill leachate• Wastewater treatment plants
• Results of site-trials
• ConclusionsAuto samplers in-situ
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) sudden loading.
Site 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
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.
Drip-feed No leachate Shock loading
Effluent
ammonium (mgN/
L)
Site 1: NH4-N trends
> ELVs < ELVs
Study Site 2
Leachate pumped via rising main from landfill- controlled by leachate levels
Auto sampler monitoring plant performance
Site 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
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
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).
High leachate loading Low leachate loading
Effluent NH4-N
(mg L-1)
9/11
/201
4 18
:30
9/12
/201
4 10
:30
9/13
/201
4 2:
309/
13/2
014
18:3
09/
14/2
014
10:3
09/
15/2
014
2:30
9/15
/201
4 10
:30
9/16
/201
4 2:
309/
16/2
014
18:3
09/
17/2
014
10:3
09/
18/2
014
2:30
9/18
/201
4 18
:30
9/19
/201
4 10
:30
9/20
/201
4 2:
309/
20/2
014
18:3
09/
21/2
014
10:3
09/
22/2
014
2:30
9/22
/201
4 18
:30
9/23
/201
4 10
:30
9/24
/201
4 2:
309/
24/2
014
18:3
09/
25/2
014
10:3
09/
26/2
014
2:30
9/26
/201
4 18
:30
9/27
/201
4 10
:30
9/28
/201
4 2:
309/
28/2
014
18:3
09/
29/2
014
10:3
0
0
2
4
6
8
10
12
Site 2: NH4-N trends
< ELVs
WWTP leachate loadings expressed as a percentage of WWTP effluent
WWTP
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 0.0Shock load (2 hour discharge to aeration tank) 2,400 0.9 34
2 Shock high (2 hour discharge to sewer) 6,450 2.4 36Shock 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.
Presentation• Project background
• Description of study sites• Landfill leachate• Wastewater treatment plants
• Results of site-trials
• Conclusions
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.
Grazie per l’attenzione.
Please feel free to contact me if you have any queries: [email protected]