sardinia 2015: impact of municipal solid waste landfill leachate loading on the performance of two...
TRANSCRIPT
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.
