REVIEW AND INVESTIGATIVE WORK ON CLOSED SYSTEM DISPOSALFACILITIES IN SERVICE FOR AN IMPROVEMENT OF DISPOSALTECHNOLOGIES(Ⅲ)

Shin Matsumoto1, Katsuei Nishiyama2,Kazuei Ishii 3,Masataka Hanashima4,Tohru Furuichi5
1 Japan Engineering Consultants Co., Ltd., Tokyo, Japan
2 CTI Engineering Co., Ltd., Tokyo, Japan
3 Graduate School of Engineering, Hokkaido University
4 Chairman of the Research Committee for Closed System Disposal Facilities, Tokyo, Japan
5 Vice Chairman of the Research Committee for Closed System Disposal Facilities, Tokyo, JapanABSTRACT
The closed system disposal facilities (hereafter referred to as “CS”) means: the landfill system with a roof. The
number of CS in total, including those under construction and design are going to reach 50 as of 2008 in Japan.
Some systems have already been in service for several years and a few of them have completed their service. Our
research group reported in a former paper on the results of an investigation of 35 CS by sending inquiries toconsultants, general contractors and managers who were operating CS. We continued our investigations of other CSs
constructed and/or planned after our former investigations. Our group, as noted before, aims at making investigative
work on existing or planned CS so as to seek valuable information. The information we ask for is not only including
plain information but also information on problems to solve, on designing, constructing and operating technologies
for CS in order to improve the closed type landfill system technology. We hereby report some statistics on thesituation of CS in Japan obtained from the inquiries and some are results and counter measures we considered tosolve problems or to improve CS technologies.
keywords : Landfil,Closed System Disposal Facilities,

INQUIRIES AND DISCOVERY OF PROBLEMS
ON CS
We have already had information from former
inquiries for the existing CS and this time we
executed similar inquiries in addition for other CS
planned or constructed after the previous
investigation and got answers from 46 CS including
former investigation in total. The inquiries are sent torelating consultants and general contractors asking
about the following; design conditions, designconcepts, thoughts on construction works andmaintenance. Major items included in the inquiries
are as follows;

Proceedings of APLAS Sapporo 2008
The 5th Asian-Pacific Landfill Symposium
Sapporo, Hokkaido, Japan, October 22 – 24, 2008

(1) General specifications of the CS(2) Conditions of the installation site(3) Drawings and/or brochures(4) Basic structure of CS(5) Methods of bringing in and depositing of waste(6) Waste stabilization methods(7) Measures to control indoor environmentalconditions(8) Measures to control outside environmentalconditions(9) Methods of proper finishing of dumping, closureand ultimate land use of landfill sites(10) Others

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
In addition to the inquiries, we visited to several
users of CS to listen directly to opinions from them
about situations on the actual operation andmaintenance and to get information on problems orissues of the system so that it can be improved.
We already reported in APLAS 2006 (Hanashima etal., 2006) on problems and tasks that closed system
landfill sites have, which we discovered from theanswers to our inquiries.
We continued the investigation after the inquiries toextend our knowledge on the subjects, especially on
the relationship between the CS and theneighborhood residents, and the situation of leachatefrom CS that have been disused.
STATISTICS ON CS
We analyzed the answers to our inquiries from 46 CS
and got some statistical data to show the present
conditions on CS in Japan. Figures 1 through 7 show
several samples of statistics on CS in Japan thatare classified by various parameters.
The figures do not show the data of the facilities fromwhich no answers were obtained.
Waste composition dumped in CS
Figure 1 depicts the composition of waste dumped inCS and mainly incinerated residue plus
incombustible (52%), but there is also onlyincombustibles CS (30%), only incineration residue(11%), combustibles plus incombustible (7%). The
incinerated residue and incombustibles have atendency to increase the rate.
But there are three CS which deposit combustibles
plus incombustibles. In the case where combustible
incombustibles

11%

incineration residue

5incineration residue+incombustibles

2452%

combustibles+incombustibles

30Figure 1

1430%

7%
51015202530

Waste composition deposited in CS

wastes are dumped, it can be considered to generategases such as CH4, H2S or H2 and very careful
maintenanceandmonitoringforindoor
environmental conditions of CS should be performed.
Dimensions of CS
Figure 2 shows dimensions of CS constructed orplanned. Deposit capacity of CS is showed in figure2(a) and the capacity of most CS are smaller than
50,000m3 (85% in total) and the largest CS has acapacity of 195,000m3 as of today.
Figure 2(b) and figure 2(c) illustrate the capacity ofone (1) block, and the area of each block and thefigure 2(d) shows the number of blocks in CS. For
most of the CS, 87% of all, the capacity of one blockof their site is less than 30,000m3.
For the area of the block, smaller than 1,000m2 theblock has the largest percentage (32%) and 3,000m2
or more is 20%. As for the number of blocks, one (1)block type that will not need to shift covering
structure, has the largest numbers of installation(69%) and the percentage of CS having 4 blocks andmore is 7%.
Anyhow, recently constructed CS or constructed CS
in the future sees a future trend becoming larger indimension and capacity.
Material and structure of the covering system
Material and structure of the covering system areshown in figure 3. Figure 3(a) shows that thepercentages of roofs made of plastic sheets and steel
plates are 15% and 85% respectively. The plastic
sheet structure seems not to be strong against heavy
snowfall, but actually, 3 CS out of a total of 7 thathave plastic sheet structures are installed in the areasthat have a heavy snowfall in the winter. The plastic
sheet structure displayed its durability against thesnowfall.
From the figure 3(b), most CS have a span length ofless than 20m (47%) . The percentage of CS having
40m or more is 9%.

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium(a)Deposit capacity of CS(b)Capacity of 1 deposit block
6100000m3 or larger

2 4%30000m3 or more

50000m3 or lager～smaller than 100000m3

11% 510000m3 or more～less than 30000m3

30%

5000m3 or more～less than 10000m3

27%

less than 5000m3

30%1000m3 or lager～ smaller than 50000m3

1839%

5000m3 or lager～smaller than 1000m3

22%

10

smaller than 5000m3

24%11005101520%

94 or moredeposit 7% 3blocks

2000m2 or lager～smaller than 3000m2

20%

93 deposit
blocks

15% 72 deposite
blocks

9% 428%1332%

smaller than 1000m2
05151015Figures 2

1 deposit
blocks2069%
0101020

3930

Figure 315322040m or more

9% 330m or more～less than 40m

25%

30

4020m or more～less than 30m

19%

8647%

less than 20m
010(b)Roof span length

15%785%

14Dimensions of CS(a)Material of covering systemsteel plate12(d)Number of deposit blocks

3000m2 or lager

1000m2 or lager～smaller than 2000m251420(c)Area of 1 deposit blockplastic
sheet

13%

40500Material and structure of covering system

510151520

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
Storage structure
The statistic data on storage structure of CS are
depicted in figure 4. Figure 4(a) shows most of CS
has a reinforced concrete structure (51%). That isbecause the depth of CS is 5 to 10m in depth asshown in figure 4(b) and in order to get a larger
volume for depositing with a minimum span ofroofing, a higher slope gradient is adopted, so that areinforced concrete structure is advantageous against
a dam or a dam and sheathing structures. The slope
gradient of CS structures is indicated in figure 4(c)and a vertical type has the largest share of 55%.
(a)Storage structure9%

dam structure
dam & sheathingstructurec)

414%

6

reinforced
conctrete

51%
26%

others
0

522

11
10

152025(b)Depth of landfill

15m or more

2 5%

10m or more～less than 15m

22%95.0m or more～less than 10m

63%

3.0m or more～less than 5.0m

26

4 10%051015202530(c)Slope gradient

1:1.0 or
more

10% 4

1:0.1 ormore ～lessthan 1:1.0

32%

14

verticalwall

55%

0Figure 4

510Structure of CS

2215

Structure of waterproofing system
The Joint Order amended in June 1998 specifies thestandard for landfills in Japan. The Joint Order
designates the structure of the sub surface liner
systems as follows;a) The surface of clay layer, that is at least 50cm
thick and has K(permeability coefficient) not
exceeding 10nm/sec, should be covered with alining sheet.
b) The surface of watertight asphalt concrete, that isat least 5cm thick and has K not exceeding
1nm/sec, should be covered with a lining sheet.

2025

The non-woven fabric surface covered withdouble lining sheets. Non woven fabric must beplaced in between the double lining sheets sothat both sheets will not be damaged at the sametime.
d) (Exceptional provision) A structure consisting ofa mortar sprayed slope covered with a lining
sheet or rubber asphalt is acceptable in the caseof slopes where the slope angle exceeds 50% andthe risk of leachate storage does not exist.
As for CS, the same specification of the Joint Orderis applied. Figure 5(a) shows the structure statistics ofwaterproofing systems for the bottom of CS. The
figure illustrates that CS with double liner sheets
have the highest percentage of share 58%, and aconcrete plus a liner sheet structure follows.
Figure 5(b) depicts a statistic data for structures ofwaterproofing systems for side wall and slope faces.
The figure shows that CS having double liner sheetson the side wall and CS with concrete plus a liner
sheet have a share of 44%. It has been discussed
whether concrete could be added or omitted, as awaterproofing structure or not, but the conclusion has
not yet been decided. Anyway, when the concrete
structure is designed as a waterproofing structure,some technical consideration and measures should betaken into consideration for the concrete wall.
Figure 5(c) shows the setting method of liner sheet
for side walls. The case of using flat bar is 44%
followed by fixing with concrete.

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium(a)Structure of water proofing
system(bottom)
double liner
sheets2558%

concrete+liner
sheet

1228%

asphalt+liner
sheet

5%

2others

4 9%051015202530(b)Structure of water proofing system(side wall and face of slope)
double liner
sheets44%

19

concrete+liner
sheet

44%

19

asphalt+liner
sheet

012%

others0551015

Waste stabilization systems
The waste stabilization is one of the important
technical issues in CS. Figure 6 illustrates thestructure of CS from the viewpoint of waste
stabilization. The figure shows the semi-aerobicsystem, which is the most common in Japan and has
the largest share of 79%. The semi-aerobic system
supplies air which is necessary for the stabilization
reaction in waste, through the leachate collection
pipes located at the bottom of waste layer and thenatural air flow caused by an ascending current ofwarmed air through the biological reaction in waste.
So as to enhance stabilization reaction in waste, someCS adopted aerobic systems that are equipped withblowers to send air artificially from the bottom of thewaste layer.
Because CS is not exposed to natural rain fall,controlled water supply is usually required for thestabilization and flushing of contaminants in thewaste.

20(c) Seeting method of liner sheet

flat bar

1844%

concrete

079%

22%

9510aerobicsystem
1521%

8200

Figure 5311434%otherssemiaerobicsystem

Structure of waterproofing system for CS

Figure 6102030Waste stabilization systems

40

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
Figure 7 shows the destination of treated leachate.
For five(5) CS, leachate is treated and desalinated byelectro dialysis or reverse osmosis, and thendesalinated water is reused for sprinkling usually
without the discharge of water to the outside. This
type of leachate treatment is applied for CS whose
deposited waste includes incinerated residues whichcontains high inorganic salt.
Nine(9) CS are recycling their leachate after
treatment without desalination. In this case, waste
deposited in the CS is mainly incombustibles,
incinerated residue is not dumped and the salinity ofleachate is low.
In eight(8) CS, the leachate volume is very small,then leachate is transferred to other facilities such as
sewage treatment plants and so consequently leachate
is not discharged to public waters from the CS.
Sixteen(16) CS treat leachate and discharge treatedleachate into the public waters.
From the statistics, 22 of 41 CS adopt no-discharge
system for leachate.

【Facility data】
Area of landfill
800m2
Capacity of landfill
6,333m3
Buried wastes
incinerated residue
and incombustibles (25%)
Operation began inApril, 2002

(75%)

Figure 8 shows the measurements of properties of theleachate produced by the facility that began theoperation in April, 2002.
The facility was closed in June, 2005, and then, theroof was removed in March, 2006
The trend of properties of the leachate is as describedbelow.
・The BOD and COD reached their maximum values

no-discharge(recycled afterdesalinated)

5

12%

no-discharge(recycled aftertreated)

22%

no-discharge(carried to otherplace)20%

in the early time of the disposal when the amount ofdisposed wastes is low and water is sprinkled steadily.
・T-N increased slowly until the facility was closed.

9・Cl- is steady at approximately 20,000mg/L during
the facility is in service.
・Every property reduced their level due to water8discharge forpublic waterssprinkling of high intensity after completion of39%

no splinkling 7%
0Figure 7

Trend of properties of leachate (Example cases offacilities that completed their service)
Of existing fifty (50) CS, only a few of themcompleted their operation. This section describes thetrend of properties of leachate produced by a facility
that completed their operation.

16

operation of the facility.
・The facility maintains steady properties even after theroof was removed.

351015

Destination of treated leachate

20

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
100

BOD：mg／L8060
40
200

2002/4

2003/4100

2004/4

2005/4

2006/4

2007/4

2004/4

2005/4

2006/4

2007/4

2004/4

2005/4

2006/4

2007/4

2004/4

2005/4

2006/4

2007/4

COD：mg／L

80
60
40
200

2002/4

2003/4100

T-N：mg／L

80
60
40
200
2002/4

2003/4Cl-：mg／L

40,00030,00020,00010,0000
2002/41,000

2003/4amount or water sprinkled（m3）800amount of rain-fall（m3）

600
400
200
0
2002/48,000

2003/4

2004/4

2005/4

2006/4

2007/4amount of waste disposed：tons

6,000

operationcompleted

4,000

roof removed

2,000
0
2002/4

2003/4

2004/4

Figure 8

2005/4

2006/4

Results of leachate analysis

2007/4

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
CONCLUSIONS(1) We continued investigation of works by sending
inquiries to consultants and general contractors, andby visiting CS in service to collect useful information
on emerging issues to devise proper solutions.
Hereby we reported some statistics to introduce thesituation of CS in Japan.
(2) Statistics show most CS deposit incineration
residue plus incombustibles or incombustibles only.
CS depositing of partial combustibles should takemuch care to proceed with stabilization of waste andto control indoor environmental conditions.
(3) The capacity of most CS is 10,000m3 or smaller,
and the largest one has a capacity of 195,000m3.
Those CS are separated into one to six blocks.
(4) Steel plates are used mainly for materials of thecovering system and some CS use plastic sheets. The
roof span is usually less than 20m, but roofs having aspan of 40m or more have already been constructed.
(5) As for the waterproofing system, double liner
systems and concrete plus liner sheet are used.
(6) Semi-aerobic systems are adopted for waste
stabilization for almost CS and some CS use aerobicsystems.
(7) The example case facility that completed theoperation shows low concentration of the leachate
after closing the site and after removing the roof. Thismeans that the water sprinkling during the disposal
period functions effectively.
ACKNOLEDGEMENTS
The paper reports are the results of the investigative
work of Review and Investigatitiven Work on Closed
System Disposal Facilities in Service (RIWCS).
Members of RIWCS in Research Committee for CS
are Nishiyama,K., /CTI Engineering Co., Ltd.,
Yazawa,N.,Yoshimura,T.,/Kumagai
GumiCo.,Nakaya,Y.,/Maeda Corporation, Matsumoto,S.,/Japan
Engineering Consultants Co., Ltd.,REFERENCES
Matsumoto,S.,
Nishiyama,K.,Ushikoshi,K.,
Hanashima, M., Furuichi, T., (2006) “Review andInvestigative Work on Closed System Disposal

Facilities in Service for an Improvement of Disposal
Technology( Ⅱ )”, Proceedings of the APLAS
Shanghai 2006,pp.