STUDY OF THE WASTE STABILIZATION INDEX ON CLOSED SYSTEM DISPOSALFACILITIES BASED ON FIELD SURVEY DATA 2Takashi Kohinata1 , Kazuei Ishii2 , Ryuji Yanase3, Masataka Hanashima4, Tohru Furuichi5
1 Technical Division, Fukuda Corp.,
2-778, Nishibori-tori, Chuo-ku, Niigata, 951-8061, Japan
2 Graduate School of Engineering, Hokkaido University,
N13, W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan
3 Organization Environmental Preservation Center, Fukuoka University,
2-3-26, Nanakuma, Johnan-ku Fukuoka, 814-0180, Japan
4,5Research Committee for Closed System Disposal Facilities
Chateau Takanawa 401,3-23-14, Takanawa, Minato-ku, Tokyo 108-0074
4Chairman, 5Vice-Chairman

ABSTRACT
We conducted a survey at in-service Closed System Disposal Facilities (hereafter called “CS disposal facilities”)
to evaluate stabilization of waste. In this study, as the stabilization index, we focused on the landfill gas, temperatureof waste layers, waste chemicals (analyzed with elution test) and leachate. This paper reports the results ofinvestigations of two CS disposal facilities and one open type facility that landfill residues from the same
incineration facilities and shredding facilities, meaning that the properties of the landfilled wastes from the threedisposal facilities are nearly identical.
As a result, the following things were proved.
The CS disposal facilities that are capable of supplying sufficient amount of water to their landfilled wastes layer bycontrolling the water sprinkling may promote microbial decomposition of organic substances and scouring of
inorganic salts by the water, possibly contributing to stabilization of the wastes. On the other hand, for the open typedisposal facilities that is not capable of controlling the water supply, water for stabilization of the wastes may beinsufficient or excessive, resulting in making interior of the landfilled waste layer anaerobatic, leading to inhibitionof promotion of the waste decomposition.
Keywords: Closed System Disposal Facilities, Waste Stabilization, Elusion Test, Leachate

INTRODUCTION
CS disposal facilities contribute to promotion ofstabilization of landfilled wastes. However, the methodof controlling the stabilization of wastes is notunderstood well mainly because the components oflandfilled wastes and structure of facility vary amongProceedings of APLAS Sapporo 2008
The 5th Asian-Pacific Landfill Symposium
Sapporo, Hokkaido, Japan, October 22 – 24, 2008individual landfills. As a result, we have conductedinvestigations and researches for evaluating the state ofstabilization of wastes that are landfilled in some CS
disposal facilities that are in operation.
As the indices of the stabilization of wastes, we
focused on the landfill gas, temperature of waste layers,

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
Table 1 Outline of disposal facilities

Facilities
Landfill Type
Beginning of operation
End of Landfilling
Landfill area
Landfill capacity
Landfilled waste

N Municipal Disposal Facility
Closed type

R Municipal Disposal Facility
Closed type

M Municipal Disposal Facility
Open typeDec-02
Dec-02
Nov-02
Jun-09Mar-10Mar-1722
2900m
2,800m
1,000m3
3
34,500m3,825m7,100mIncineration residue, Shredded incombustible waste(wastes are nearly identical)
38m3/day
4m /day×4day/week
Wate sprinkling amount(equivalent to 8.0mm/day rainfall) (equivalent to 4.4mm/day rainfall) (average 3.７mm/day rainfall)
Not operation
Not operation
Not operation
Air supply
waste chemicals (analyzed with elution test) andleachate, and have conducted the investigations andresearches of the factors in six CS disposal facilities.
This paper reports the results of investigations of two
CS disposal facilities out of those six facilities that
landfill residues from the same incineration facilities
and shredding facilities, meaning that the properties ofthe landfilled wastes from the two disposal facilities arenearly identical, comparing the results with those ofsimilar open type disposal facilities.
This paper also reports the results of investigation of
the indices of the stabilization of the landfill gas, waste
chemicals (analyzed with elution test) and leachate.
DISPOSAL FACILITIES SURVEYED
Table 1 shows outline of the two CS disposal facilities(N* final disposal facility and R* final disposal facility)
and open type disposal facilities (M* final disposalfacility). N and R type CS disposal facilities are
sprinkled with water except winter with different
amount of water and frequency.
The annual mean precipitation of this region including
the location of the open type disposal facility over thepast twenty years is 1342 mm or 3.7 mm/ day.

contained in the gas is higher than the one contained in
the atmosphere (approximately 380 ppm), and theconcentration of CH4 contained in the gas is equal to ora little higher than the one contained in the atmosphere(approximately 2 ppm). On the other hand, for M
disposal facility, the concentrations of both CO2 andCH4 contained in the gas are higher than thosecontained in the atmosphere, and also higher than thosecontained in the gases collected from N and R disposal
facilities. For M disposal facility, it is estimated thatthese results were obtained due to significant anerobic
decomposition of the wastes because of higher
percentage of water content in the waste layer of thefacility especially due to melting of snow in the early
spring and higher precipitation immediately before theinvestigation .(See figure 1)
For N disposal facility, ammonia and amines weredetected by a gas detected at the concentrations of 1
ppm and 0.5 ppm respectively in the tube buried in thewaste layer of the facility.
Elution test for landfilled wastes: Landfilledwastes sampled from individual disposal facilities wereTable 2 Composition of landfill gas (LFG)

RESULTS OF THE SURVEY
Landfilled waste
Landfill gas: Table 2 shows the results ofanalysis of the landfill gase (averages of concentrationsof constituents) that was collected using sampling bags
at the gas drainage pipe of each disposal facilities. For
N and R disposal facilities, the concentration of CO2Facilities
Measurement date
Bacground CH4(ppm)
CO2(ppm)
N2(%)
LFG
O2(%)
CH4(ppm)

N Municipal R Municipal M Municipal
Disposal
Disposal
Disposal
Facility
FacilityFacility
09/20/07
09/19/07
09/19/07

1.87
1129
78.1
20.1
2.67

1.94
2067
78.5
20.2
4.59

2.12
4425
77.9
19.9
169

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium

5045
40Rainfall, mm/day

35
30
25
2015
10

12/15/07

11/16/07

10/18/07

09/19/07

08/21/07

07/23/07

06/24/07

05/26/07

04/27/07

03/29/07

02/28/07

01/30/07

001/01/07

5Date, M/D/Y
Figure 1 Rainfall in this region

250

250

200

150

100502005

200

1501002005
2006
2007

502006
2007

000
1020T OC concentration, mg/L

250

250200200Height from bottom, cm

300

R Disposal Facility

Height from bottom, cm

300

Height from bottom, cm

Height from bottom, cm

N Disposal Facility

150

100502005
2006

1501002007
0010002000
Cl- concentration, mg/L2005
2006
2007

50001020
T OC concentration, mg/L01000
2000
Cl- concentration, mg/L

Figure 2 Concentration by elution test on landfilled waste in each depth
subjected to the elution test. Figure 2 shows the resultsof the test (concentration of chemicals contained in theincineration recidue vs measurement depths) obtainedin the points in 2005, 2006 and 2007 that are nearly thesame locations. TOC and CL- are used as indices oforganic elements and inorganic salts respectively.
Although the terms of the investigations were too

short to identify clear tendencies, N disposal facility in2006 showed a tendency that the concentrations of
TOC and Cl- are lower in upper layer. Generally, if nowastes are added on the surface layer, water sprinklingover the surface layer reduces the concentrations of thechemicals contained in the layer. The test results of N
disposal facility in 2006 seem to show this effect ofAPLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium

0T OC concentration, mg/L
51015200

Depth from surface, cm-20-40-60-80

N Disposal
Facility
R Disposal
Facility
M Disposal
Facility-100-120-140-Cl concentration, mg/L
01000

2000

facility. Since the thickness of landfilled wastes varies
among individual disposal facilities, the sample depths
measured from the surface of the landfilled waste layer
were used instead of those measured from the bottom.
M disposal facility shows low concentration especiallyin upper layer, which may have been caused by thesprinkling of much rain water before the investigation.
At the depth deeper than –40cm of these disposal
facilities, N and R disposal facilities show a tendency
that the concentrations of TOC and c Cl- are both lower
as compared with M disposal facility. The lower
concentrations at the deeper depth that is affected lessby the rain immediately before the measurement in Nand R disposal facilities supports that the closed typedisposal facilities stabilize their waste earlier than opentype.
Figure 4 shows temporal changes of mean
concentrations. Although it is hard to say that theresults evaluates the general nature of each facility
because the number of samples is small, both TOC andCl- show a tendency that their concentrations decrease
TOC

16
Concentration, mg/L

water sprinkling. In other than 2006 in N disposal
facility, addition of wastes on the top seems to increase
the concentration in upper layer. N disposal facility in2006 shows lower TOC concentration in upper layer,
which may the result of the progress of aerobic
decomposition caused by the contact of the surfacelayer of the waste with the atmosphere. The inclinationof TOC curve is sharper than that of Cl-, which may
have been caused by reduction of TOC in upper layer
due to both microbial decomposition and watersprinkling.
Figure 3 shows the results of analysis performed in2007 vs depth, comparing with the open type disposal

0

N Disposal Facility
R Disposal Facility

14121086420
2004

-20

2005

2006

2007

2008

-40-Cl
2500

-60
-80
-100-120

N DisposalFacility
R DisposalFacility
M Disposal
Facility-140

Figure 3 Concentration by elution teston landfilled waste in each depth(Comparison of Closed typeand Open type)

Concentration， mg/L

Depth from surface, cm

Examination year

N Disposal Facility
R Disposal Facility

2000
1500
100050002004

2005

2006

2007

2008

Examination year

Figure 4 Change in concentration by elution test on
landfilled waste

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
than R disposal facility advanced the microbial
decomposition of organic substances faster, but, forinorganic salts, the water sprinkling does not affectmuch on both disposal facilities.
Figure 6 shows the results of analysis conducted in2007, comparing them between CS disposal facilities
and open type one. For BOD and COD, M disposal
facility clearly shows higher concentration than N andR disposal facilities, and for electrical conductivity,
concentrations of chlorine ion and calcium, they show
noticeable tendencies that are inverse to BOD andCOD. When evaluating the concentrations except thatof total nitrogen, the organic decomposition possibly
advanced faster in CS disposal facility, which resulted
in reduction of the concentrations in the leachate. On
the other hand, CS disposal facilities had watersprinkling for inorganic salts more, which resulted inas the time elapses, which possibly demonstrates thatthe wastes of these facilities are stabilizing. N disposal
facility that was sprinkled with water more than R
disposal facility shows a tendency that theconcentrations are smaller, which possibly expresses
that the stabilization is advancing.
Leachate
Figure 5 shows the properties of leachate of CS
disposal facilities. N disposal facility shows aremarkable tendency that COD and concentration of
total nitrogen (except BOD) is smaller as comparedwith R disposal facility. On the other hand, forelectrical conductivity, concentrations of chlorine ion
and calcium, no big difference can be seen between
both facilities. These results may express that N
disposal facility that was sprinkled with water more

7,000

50

6,000

N BOD
N COD
N T-N
R BOD
R COD
R T-N

4030

Concentration, mg/LConcentration, mg/L

60

2010N ECN ClN CaR EC
R ClR Ca

5,000
4,000
3,000
2,000
1,000
002005
12006
22005
12007
32006
22007
3

Ｅｘａｍｉｎａｔｉｏｎ ｙｅａｒ

Ｅｘａｍｉｎａｔｉｏｎ ｙｅａｒ

Figure 5 Change in concentration of leachate quality (Closed type)
N:N Disposal Facility, R:R Disposal Facility

807060

M Disposal Facility

50403020

N Disposal Facility

7,000

R Disposal Facility
Concentration, mg/L

Concentration, mg/L

8,000

N Disposal Facility

R Disposal Facility

6,000

M Disposal Facility

5,000
4,000
3,000
2,000
1,000

100

0
BOD

COD

T-N

EC
mS/m

Figure 6 Comparison of leachate quality

Cl-CaAPLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium

140

ＢＯＤ

120

10100

880

660

Aug-05Jul-05

Jun-05

May-05

Apr-05Mar-05

Feb-05Jan-05

Dec-04

Nov-04

Oct-040Sep-04

0Aug-04

20Jul-04

2Jun-04

40May-04

412,000
10,000

140
120

8,000

100

6,000

80
60

4,000

40
2,000

20
Aug-05Jul-05

Jun-05

May-05

Apr-05Mar-05

Feb-05Jan-05

Dec-04

Nov-04

Oct-04

Sep-04Aug-04

Jul-04

Jun-04

May-040
Apr-0403160
Water sprinkling
Cl

Water sprinkling amount, mConcentration, mg/L

Water sprinkling amount, m

123160
Water sprinkling

Apr-04

Concentration, mg/L

14Figure 7 Relationship between water sprinkling amount and properties of the leachate(N Disposal Facility)
increasing the concentration in the leachate in shortperiod.
Figure 7 shows the relationship between monthly
water sprinkling amount and properties of the leachate.
BOD is affected less by the water sprinkling amount,but the concentration of chlorine ion shows a tendency
that it is higher in the months with much water
sprinkling amount. These results, together with theresults of elution test described before, can lead to thefollowing conclusion.
Within the short term, increasing the water
sprinkling amount advances the scouring of inorganic
salts, resulting in raising the concentrations in theleachate. As a result, in the long term, the content of
inorganic salts in the landfilled wastes is reduced, andthe concentrations from the elution test becomes lower.
Since the concentration of chlorine ion in the leachateof M disposal facility is extremely low, it is estimatedthat inorganic salts remains much in the landfilledwastes, resulting in showing high concentrations at-80cm in the elution test.
On the other hand, for the organic substances, properamount of water sprinkling accelerates the microbial
decomposition, resulting in stabilizing the wastes andreducing both the concentrations in the leachate and theconcentrations obtained in the elution test. Since theAPLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
organic components are also subjected to the water
sprinkling, the disposal facilities with much sprinklingwater may increase the concentrations of BOD and
COD in the leachate. But, for N disposal facility,
advance of stabilization of the waste layer may havelowered the concentrations of the BOD and COD
though the amount of water sprinkling is much. For M
disposal facility, the interior of the landfilled waste
layer is prone to anaerobatic, which also possibly leads
to high concentrations of BOD and COD.
CONCLUSION
Although it is not appropriate to bring a clear
conclusion due to lack of the data, it can possibly besaid that the CS disposal facilities that are capable ofsupplying sufficient amount of water to their landfilledwastes layer by controlling the water sprinkling may
promote microbial decomposition of organic
substances and scouring of inorganic salts by the water,
possibly contributing to stabilization of the wastes. On
the other hand, for the open type disposal facilities thatis not capable of controlling the water supply, water forstabilization of the wastes may be insufficient orexcessive, resulting in making interior of the landfilledwaste layer anaerobatic, leading to inhibition ofpromotion of the waste decomposition.
ACKNOWLEDGEMENTS
This paper presents the results of studies of Working ofField Investigation for Waste Stabilization, ResearchGroup of Control in Research Committee for Closed
System Disposal Facilities. We express ourappreciation to the following members for theircooperation and lead, and also to the persons in chargeof individual facilities for offering the place for out
investigations and researches.
Members of Working of Field Investigation for Waste
Stabilization, Research Group of Control in ResearchCommittee for Closed System Disposal Facilities;
R.Yanase/Fukuoka
University,
K.Ishii/Hokkaido
University,
T.Kohinata/Fukuda
Corp.,
K.Shibata/Obayashi Corp., T.Hamada/Ohmoto Gumi

Corp., Y.Hamao/Kobelco-Eco Solutions Co., Ltd.,
H.Itoh/Dai Nippon Const., T.Kaneko/Toyo Giken Co.,Ltd.,
Y.Hamada/Towa
Technology
Corp.,
H.Nakajima/Toda
Corp.,
K.Miyazaki/Nishimatsu
Construction Co., Ltd., S.Shoji/Nippon Koei Co.,
Ltd., A.Matsuura/Fudo Tetra Corp., N.Tajima/Maeda
Corp., J.Imai
REFFERENCES
Kohinata, T., Ishii, K. (2007): Study of the waste
stabilization index on closed
system disposal
facilities based on field survey data, EleventhInternational Waste Management and Landfill
Symposium, Sardinia 2007, CD-ROM(2007)
Kohinata, T., Ishii, K., (2006): Study of the waste
stabilization on closed system disposal facilities
based on survey data, Proceedings of the ForthAsian-Pacific Landfill Symposium in Shanghai 2006,Poster