STUDY ON THE EFFECT OF WATER SPRINKLING FOR REMOVAL OF
CHEMICALS FROM WASTES DISPOSED IN CLOSED SYSTEM LANDFILL SITES

Yoshikazu Otsuka1, Kazuei Ishii2, Masataka Hanashima3, Tohru Furuichi4
Working of fundamental investigation for waste stabilization,
Research group for control, Research Committee for Closed System Landfill sites
Chateau Takanawa 401, 3-23-14 Takanawa, Minato-ku, Tokyo 108-0074
1 Vice-Chief, 2 Group Leader, 3 Chairman, 4 Vice-Chairman

ABSTRACT

these two approaches that use the stabilization models, theFor the closed system landfill sites, the roof that covers theformer (column) test studied the phenomenon at microscopic

facilities prevents rain water from permeating the layers oflevel treating incineration ash particles, and the latter test

disposed waste. Thus, this type of waste landfill sites allows

treated individual landfill sites as an experimental model tocontrol of water sprinkling parameters such as time (hours),

study the phenomenon at macroscopic level.

intensity and interval. Our study found that these parameters

In this study, we examined the salt removing property ataffect the mode of transfer of organic substances and salts

the macroscopic level based on the measurements obtained

from the layers of buried wastes. The water sprinkling time isfrom existing open type landfill sites. As a result, we were

defined as the hours of continuous water sprinkling per day

able to verify quantitatively that the salt removing property(hours/day), and the water sprinkling intensity is defined as
the amount of sprinkled water permeated into unit area ofwaste layers per hour (mm/hour・m2). The water sprinklinginterval is the period of time (hours or days) in which thewater sprinkling is stopped. Our study conducted two kinds

varies among several landfill sites that contain different types
of wastes. This research paper introduces two types ofchemicals removing models and reports the results of
examination of the macroscopic model.

of water sprinkling tests; the test using a small scale column
and the test using a relatively large scale experiments. From

1

INTRODUCTION

the results of former test, we obtained knowledge that higher

The purpose of this study is to resolve technical issues thatwater sprinkling intensity produces higher efficiency ofoccur in planning and designing the closed system landfill

removal of salts and organic matters contained in the wastes

sites, such as what specifications we should establish forand that daily water sprinkling is more efficient than weekly

water sprinkling facility for stabilizing the buried wastes andwater sprinkling. On the other hand, we utilized the data

how we should control the facility, which are uncertain now.

obtained in the latter experiment to attempt calculation of

To achieve this purpose, we conduced fundamental studies

chlorine ion concentration of leachate at arbitrary time on thewith regard to the method of acceleration of waste

assumption that the phenomenon can be represented by astabilization, such as laboratorial experiment on thesimple linear function on a time series plot because eluting

stabilization of wastes and examination of stabilization

action of salt presumptively depends on time dominantly. Inmodel simulation through formulation of numerical models

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

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposiumin the period from fiscal years 2002 to 2006. From fiscal year

2.1 Microscopic chemicals removal model

2008, we implement the studies on multilateral point of view

The microscopic chemicals removal model is defined here,

such as arrangement and analysis of leachate property data

in a limited sense, as an analytical model that allows

collected from existing landfill sites for their temporal

simulation of eluting properties of organic components andchanges, and examination of the target values of thesalts in a relatively small domain for small waste particles

stabilization from the point of view of utilization of closed

such as incineration ashes. This microscopic model is a threedisposal facility sites andphase (fluid phase, unmovable water phase and solid phase)

disposal methods that allow earlier stabilization of the wastes,chemicals removal model that allows relatively accurate

aiming at “establishment of concrete techniques for

simulation of eluting properties of organic components

designing the closed system landfill sites.

(TOC) and chlorine ion as a result of water sprinkling in a

For the methods of water sprinkling effective for theclosed system landfill sites, we examined them based on thedomain ranging from several centimeters to several tens ofcentimeters from the surface of waste layer.

results of removal of chemicals through the column tests andThis model has the following three issues to be verified attest using relatively large scale elements. From the results ofpresent; (1) the consistency of this model with eluting

former tests, we obtained knowledge that higher water

properties of chemicals from actual waste layers (more thansprinkling intensity produces higher efficiency of removal ofseveral meters), (2) knowledge about unsaturated infiltration

salts and organic matters contained in the wastes and thatproperty of waste layers that influences pore fluidity ofdaily water sprinkling is more efficient than weekly waterflowing water during water sprinkling, and (3) knowledge

sprinkling. On the other hand, we utilized the data obtained

about effect of microbial degradation (other than eluting

in the latter experiment to attempt calculation of chlorine ion

properties).

concentration of leachate at arbitrary time on the assumptionthat the phenomenon can be represented by a simple linear
function on a time series plot because eluting action of saltpresumptively depends on time dominantly. In these two
approaches that use the stabilization models, the former

2.2 Macroscopic chemicals removal model
The macroscopic chemicals removal model is defined
here, in a limited sense, as an analytical model that allows
simple simulation of eluting properties of organic(column) test studied the phenomenon at microscopic levelcomponents and salts in entirety of waste layer of actual

treating incineration ash particles, and the latter test treatedlandfill sites. The macroscopic chemicals removal model

individual landfill sites as an experimental model to study theallows quantitative simulation of eluting properties ofphenomenon at macroscopic level.

chemicals from wastes such as organic components (such as

The following chapters reports the results of our study that

COD, BOD and TOC), chlorine ion and nitrogen by utilizing

succeeded in obtaining the chemicals eluting properties ofdata of buried waste, leachate and precipitation (water

individual landfill sites by estimating the eluting properties ofsprinkling). Refer to Figure 1. Concretely describing, thechlorine ion of each disposal facility using a macroscopic

amount of leachate discharged from a disposal facility Qn ismodel.

estimated based on the precipitation In (statistic data) thatflows into the facility at a year Nth from the beginning of the2

CHEMICALS REMOVING MODEL
When designing a chemicals removing model, weconstruct the following two types of models to verify actual
phenomenon multilaterally, aiming at obtaining the models
that allow highly accurate simulation.

operation, and the amount of substance removed from waste
by precipitation (leachate) Wn is estimated by using actual
measurement of concentration data of the substance removed
from leachate. The amount of individual substances

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
contained in the buried waste accumulated in the landfill sites

extracted from the literatures that record properties of

Sn is estimated by using the data of amount of buried wasteleachate of the facilities, and type and amount of wastes

during the years of operation and content of individual

buried in the facilities for approximately five years.

substances.
3.2. Material balance of microscopic model
Buried waste (measurement),, content(data book)
埋立物（実測値），含有量（文献値）

We obtained the material balance with regard to the buried
wastes and leachate based on the measurement data collected

Nth Nyear’s
precipitation
年目降水量
In In
(statistic data)（統計値）

Leachate
coefficient C (data book)
浸出係数 C（文献値）

Nth N
year’swaste buried
年目の搬入量Sn Sn

from existing landfill sites. The annual infiltration of
precipitation (I) of each facility (Q [m3/y]) that is equal to the

Accumulated waste buriedΣSn-1
これまでの搬入量ΣS
n-1

Leachate
amount Qn
浸透水量

Leachate properties
Leachate properties

annual infiltration minus annual evaporation was obtained by

X:
COD, BOD, TOC,Cl,N
X：COD、BOD、TOC、Cl、N
Nth year’s leachate
N 年目浸出水濃度
concentration XnX(measurement)n（実測値）

using the rational formula (1). C [nondimensional], I [mm/y]

Nthyear’s leachate amount Qn
N 年目浸出水量
Q

Disposal
area
埋立面積
A A

n

Nth year’s chemicals removal amount Wn

N 年目洗出し量

Wn（＝Qn×Xn）

Nth year’accumulation= Sn – Wn
N 年目蓄積量＝Sn－Wn

and A [m2] of this formula represent the leachate coefficient,annual precipitation, and area of disposal respectively. For
the value of C, annual mean value of the leachate coefficientnear the relevant disposal facility that is presented in

Figure 1 Macroscopic chemicals removal model“Construction of Waste Landfill sites; Planning and Design
3

Guide” was used. The amount of leachate discharged finallyDATA OF EXISTING LANDFILL SITES

out of the landfill sites was assumed to be equal to the

3.1. Outline of landfill sites surveyed
Before applying the macroscopic model for the analysis,amount of infiltration (Q) (assuming that all infiltrated water

we surveyed literatures that describe the results of continuous

is discharged as leachate). The amount of chemicals removed

monitoring of temporal change of properties of leachatefrom wastes (W [t]) was calculated as load that is given bysamples obtained from the disposal sites that are in operation

the formula (2). In the formula (2), X [mg/L] represents theand that closed the operation. The literatures that wereconcentration of object substance contained in the leachate,surveyed were the reports issued by “Landfill Systems &which is the concentration of chloride ion (Cl-) contained inTechnologies Research Association of Japan, NPO”. Table

the leachate. The content of chloride contained in the buried

1 shows the state of landfilling of six landfill sites (A to F)

waste was assumed to have the ratio shown in Table 2.

Table 1 State of landfilling of landfill site surveyed
Landfilling information
State oflandfillingType of waste

landfill site
Ａ

Ｂ

Ｃ

Ｄ

Ｅ

Ｆ

Began in

1994

1979

1978

1993

1994

1988

Completedin operation

1997

in operation

1996

Incineration ash

37%

－

76%

－

12%

50%

Combustible

－

63%

－

－

53%

－

54%

37%

24%

100

21%

50%

9%

－

－

－

14%

－

operation inmaterials
Incombustible
materials
Sludge

4

Q=

1
C×I× A
103

(1)

W=

1
Q× X
106

(2)

ANALYSIS OF DATA・ As an index that indicates the amount of chloride
accumulated in landfill sites, exposed to rain and then%Annual mean precipitation[mm/y] 1,509 1,106 1,363 1,440 2,304 1,599

removed from the wastes, we used the numerical value
equivalent to liquid-solid ratio (L/S) that is utilized for

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

Table 2 Content of chlorine in buried waste
Buried waste

Content of chlorine

Principal incineration ash
Flying incineration ash
Note: Ratio of principal ash to flying ash ＝9:1
Incombustibles
Combustibles

Reference

0.8%
20%

8kg-Cl/ton of buried waste
200kg-Cl/ton of buried waste

0.15%
0.3～0.8%

1.5kg-Cl/ton of buried waste
3～8kg-Cl/ton of buried waste

*1
*2
*1
*3

*1：“2003 research report”, Research Committee for Closed System Landfill sites, 2004
*2：“Disposal standard of specially controlled domestic waste”, Japan Waste Research Foundation, 1993, P.71
*3：“Garbage-Disposal Facility Design Scheme redaction in 2006”, Japan Waste Management Association, 2006, P.33

column tests or dissolution tests. The LS here is the ratio

chloride ion in the waste buried in the entire facility is

between the following two factors; total amount of

more than twice of the facility F, meaning that otherleachate infiltrated into disposal site in a given period (Lfactors can exist. Figures 3 and 4 show correlation[m3]), and total volume of wastes buried in the same

between the chloride ion and L/S ration for the facilities

3

period (S [m ]). The value of L is obtained from the

C and F that showed the tendency of significant

precipitation of a disposal site (I) multiplied by mean

reduction of chloride ion concentration after theirleachate coefficient of the site (C). As an index that

operation was closed. The facilities C and F shows low

indicates the amount of chloride accumulated in landfill

value of L/S ratio when they are in operation, but aftersites, exposed to rain and then removed from the wastes,

they closed their operations, the ratio started to increase,

we used the numerical value equivalent to liquid-solidand as the ratio increase, the concentration of Cl-

ratio (L/S) that is utilized for column tests or dissolution

reduces. The landfill sites A and D showed no increase

tests. The LS here is the ratio between the following twoof L/S ratio, and thus, showed no such tendency clearly.

factors; total amount of leachate infiltrated into disposalsite in a given period (L [m3]), and total volume of3

wastes buried in the same period (S [m ]). The value of5

CHEMICALS ELUTING PROPERTY
To analyze the difference of elution of chemicals among

L is obtained from the precipitation of a disposal site (I)the facilities A to F quantitatively, we compared them bymultiplied by mean leachate coefficient of the site (C).

using a simple macroscopic model as described below.

Figure 2 shows the results of measurement ofconcentration of chloride ion contained in the leachate

As an index for the analysis, we defined the single year Cl
elution factor ACl1 as given by the formula (1).

produced in the landfill sites A to F (“A” to “F” are

A Cl 1 ( i ) =codes that represent individual facilities). From these

C Cl ( i )C Cl 100 ( i )(1)results, it is known that the facilities other than C and F

where;

elute chloride ion with the concentration less than 1000

ACl1(i)：Elution factor [nondimensional] of Cl in any one year

mg/L. It can be estimated that level of the elution
depends on the content of chloride ion in the buried
waste, but, for the facility E, the estimated content of(i th year from burying, the same for the following
explanations),
CCl(i)：Concentration of Cl(i) elution in any one year [mg/L],
andAPLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium

Concentration of chlorine ion contained inleachate [mg/L]

7000
Landfill site A
Landfill site B
Landfill site C
Landfill site D
Landfill site E
Landfill site F

6000
5000
4000
3000
2000
1000
0

1

6

11
16
Period for landfill [year]

21

Figure 2 Temporal change of chlorine ion oflandfill sites
Period after completionof operation

4.0
L/S
Cl-

3.5

L/S[-]

3.0

6000
5000

2.5

4000

2.0
3000

1.5

2000

1.0

2003

2001

1999

1997

1995

1993

1990

1988

1986

0
1984

0.0
1982

1000
1980

0.5

Leachate Cl- concentration [mg/L]

7000

Year

Figure 3 Temporal change of Cl- and L/S oflandfill site C

7000

Period after completionof operation

L/S
Cl-

3.5

6000
5000

2.5

4000

2.0
3000

1.5

2000

1.0

2004

2003

2002

2001

1999

1998

1997

1996

1995

1994

1993

1992

0
1991

0.0
1990

1000
1989

0.5
1988

L/S（-）

3.0

Year

Figure 4 Temporal change of Cl- and L/S oflandfill site F

Leachate Cl- concentration [mg/L]

4.0

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
Table 3 Results of calculations using the simple chemicals removal stabilization model
Landfill site
Max A Cl1
L/S
C Cl100 [mg/L]

A
0.099
2.428
4,157
1
0.016
0.294
33,07511

Period for landfill [year]

Min A Cl2
L/S
C Cl100 [mg/L]
Period for landfill [year]

B
C
0.677
0.329
2.348
3.646
1,255
7,570
2
1
0.044
0.011
0.112
0.096
16,922 147,052
24
18

D
1.006
6.037
248
1
0.049
0.388
1,792
12

E
0.035
0.397
9,583
4
0.009
0.405
9,718
3

completed

CCl100(i)：Concentration of Cl elution in any one year when

F
Max.
0.449
1.006
1.472
6.037
8,901
9,583
1
4
0.022
0.049
0.158
0.405
50,762 147,052
17
24

Min.
0.035
0.397
248
1
0.009
0.096
1,792
3

Average
0.433
2.721
5,286
1.7
0.025
0.242
43,22014.2

completedformula (5).

all Cl(i) contained in the buried waste is eluted completely[mg/L].

W (i )⎛ 1 ⎞WCl (i ) = ⎜ 6 ⎟C Cl (i ) w
ρw⎝ 10 ⎠The result of analysis of leachate that was actually measured(5)

at the sites was used as the value of Cl(i) as described

where;

previously.

ρw：Density of leachate [tons/m3], which is assumed “1.0”CCl100(i) was obtained from the following formula (2).
⎛ W (i ) ⎞(2)⎟( i ) = 10 6 ⎜ TCl
C

for the calculation.
The ratio of Ww(i)/WS(i) is defined as the single year

⎜ W (i ) ⎟w⎝⎠

Cl 100liquid-solid ration (L/S(i)), which is given by the following

where;
WTCl(i)：Total weight of Cl contained in the buried wastes inany one year [tons],
Ww(i)：Weight of water infiltrated into buried wastes in any
one year [tons], andformula (6).
L / S (i ) =Ww (i )
WS (i )

(6)

The results from these calculations are shown in Table 3
and Figures 5 and 6. Figure 5 shows correlation between L/S

WTCl(i) and Ww(i) are obtained by using the followingthat is given by the formula (6) and ACl1, and Figure 6 shows

formulas (3) and (4) respectively.

correlation between CCl100 and ACl1. These results
WTCl (i ) = WTCl (i − 1) + ACl 2 (i )WS (i ) − WCl (i − 1)

(3)

quantitatively demonstrate that properties of elution of Cl

Ww (i ) = Aw (i )Wwr (i )(4)from waste layers vary among individual disposal sites.

where;
WTCl(i-1)：Weight of total Cl content of buried wastes at i-1 thyear after burying [tons],
ACl2(i)：Rate of content of Cl in waste [nondimensional],

Concretely analyzing the results, ACl1 of Cl component ofleachate that is eluted from wastes distributes very widely inthe range from (disposal site A) to 1.006 (disposal site D).
This wide distribution of ACl1 may be due to difference ofWs(i)：Total weight of wastes buried in period up to i th year,

waste type, precipitation conditions, and permeability ofWwr(i)：Weight of rain water that falls in a disposal site during

buried waste layers of individual facilities. It is confirmed

one year of i th year [tons],

that there is a very strong correlation between both L/S andWCl(i-1): Weight of Cl that elutes during one year of i-1 thACl1 and CCl100 and ACl1 for the facilities except E. As for theyear [tons]

difference of elution property between the operating period

Aw(i)：Leachate coefficient [nondimensional]
WCl in any one year is obtained by using the followingof the facilities and the period after completion of theoperation, the facilities show a higher elution property inAPLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
initial stage of operation because the precipitation is larger

individual substances in existing landfill sites by applying

than the amount of waste buried in such period, and then,this approach to many other landfill sites, and then to apply

show a lower elution property after completing the operation

this approach to the water sprinkling method for closed

because the precipitation is smaller than the amount of wasteburied. As for full elution property of the facilities, the results
show that the elution property is affected not by CCl100 but by
the precipitation.

system landfill sites. In the future, we would like to continue
to examine the water sprinkling method that is required
during the period of disposal and after completion of theoperation of the facilities, by sorting out and analyzing theleachate property data of existing landfill sites for theirincineration ash, inflammable materials and incombustibles

6

CONCLUTION

and analyzing actual elution activities of organic substancesThis study implemented an approach that evaluates andand chlorine from wastes, aiming at improving the accuracy

validates the elution property of substances from existingof the stability model. Also, we would like to examine,

disposal sites quantitatively, which has never been conducted.

through surveying literatures, the effect of microbial

As a result, we succeeded in understanding the elution

degradation that is deemed contributing to the stabilization ofproperty of chlorine ion in individual landfill sites. From now

buried wastes as well as the water sprinkling effect.

on, we are planning to work out the elution activities of

APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium
We think that, through suchstudies,site A）we are able to understand, to some extent, the macroscopic elution property using a simple（Landfill（Landfill site B）

0.12

0.80
elutionfactorsimulation model withregardto the method of analysis of data of existing
landfill sites.
In thefuture, we are planning to work out
elutionfactorlinear approximation

0.10

log approximation

the elution activities of individual substances in existing landfill sites by0.60
applying this approach to many other landfill sites, and
0.08

then to apply this approach to the water sprinkling method for closed system landfill sites, thinking of proposing disposal methods
A Cl1 0.40
A Cl1 0.06
including pretreatment of wastes that accelerates
stabilization of wastes.
0.04
0.02

A Cl1 = 0.1971Ln(L/S) + 0.4036

0.20

A Cl1 = 0.0366(L/S) + 0.0106

2

R = 0.956

2

R = 0.979

0.00

0.00
0.0

1.0

2.0

0.0

3.0

1.0

L/S

4.0

1.20

elution factor
log approximation

0.30

3.0

（Landfill site D）（Landfill site C）
0.35

2.0

L/S

elution factor
log approximation

1.00

0.25

0.80

0.20

A Cl1 0.60

A Cl1 0.15

0.40

0.10

A Cl1 = 0.0867Ln(L/S) + 0.1813

0.05
0.00
0.0

1.0

2.0

3.0

Distribution after completion ofoperation

0.04
0.03

4.0

0.0

0.50
elution factor

0.30

A Cl1 0.02

A Cl1 0.20

0.01
0.01

0.10

0.00

0.00

0.02

0.2

0.4

0.6

0.8

1.0

2.0

4.0

6.0

8.0

L/S
（Landfill site F）
elution factor
linear approximation

0.40

0.03

0.0

2

R = 0.9424

0.00

L/S
（Landfill site E）

0.04

Acl1 = 0.2959Ln(L/S) + 0.3717

0.20

2

R = 0.949

A Cl1 = 0.3136(L/S) + 0.0048
2

R = 0.9724
0.0

L/S

0.5

1.0

1.5

2.0

L/S

Figure 5 Relationship between L/S and ACl1 of disposal facilities A to F
from existing landfill sites. We express our appreciation for
their cooperation very much.
ACKNOWLEDGMENTS
This paper summarizes the results of research on

REFERENCES

fundamental concepts of waste stabilization by the Research

1) K. Ishii, T. Furuichi and N. Tanikawa (2003). Promotion

Group for Control, Research Committee for Closed System

of Waste Stabilization for Design of Community andLandfill sites in the fiscal year 2007. Through the study, weControllable Closed System Landfill sites by Using aobtained many valuable advices from Mr. Yajima of Fujita

Washout Model, Proceedings Sardinia 2003, Ninth

Corporation, Mr. Abe of Kajima Corporation, and others

International Waste Management and Landfill Symposium.

who are the members of this working group when we2) Ricardo C. de Abreu, Enrique J. La Motta and Kenneth L.

established the macroscopic model and collected the data

McManis (2004). Facultative Landfill Bioreactors (FLB):APLAS Sapporo 2008, The 5th Asian-Pacific Landfill Symposium（Landfill site A）
0.12

elution factor
exponential approximation

0.10（Landfill site B）

0.80

elution factor
exponential approximation

0.60

0.08
-0.7107

A Cl1 = 32.494C Cl100

A Cl1 0.06

2

R = 0.9134

A Cl1 = 1451.6C Cl100

A Cl1 0.40

-1.06682

R = 0.995

0.20

0.04
0.02

0.00
0

0.00
0

10000

20000

30000

5000

C Cl100 [mg/L]（Landfill site C）

0.35
0.25

2

R = 0.9148

A Cl1 0.15

0.80

A Cl1

A Cl1 = 740.33(L/S)

0.60

0.10

0.40

0.05

0.20

0.00

20000

elution factor
exponential approximation

1.00

A Cl1 = -0.1085Ln(L/S) + 1.2717

0.20

15000

（Landfill site D）

1.20

elution factor
log approximation

0.30

10000

C Cl100 [mg/L]

40000-1.17132

R = 0.8731

0.00
0

50000

100000150000

C Cl100 [mg/L]（Landfill site E）

0.04
0.04

2000000Distribution after completion ofoperation

elution factor

0.03

0.50

500

1000

2000

2500

3000

（Landfill site F）
elution factor
log approximation

0.40

0.03

1500

C Cl100 [mg/L]

0.30

A Cl1 0.02

A Cl1 = -0.1438Ln(L/S) + 1.6535

A Cl1 0.20

0.02

2

R = 0.8248

0.01

0.10

0.01
0.00
0

5000 10000 15000 20000 25000 30000

C Cl100 [mg/L]

0.00
0

40000

Figure 6 Relationship between CCl100 and ACl1 of disposal facilities A to F
Results of a Pilot-Scale Study, Proceedings of GSP 142
Waste Containment and Remediation.
3) Hupe, K., Heyer, K.-U. and Stegman, R. (2003). Water
Infiltration for Enhanced in situ Stabilization, Proceedings of
Sardinia 2003, pp. 400-401.
4) Kazuei Ishii, Tohru Furuichi, and Noboru Tanikawa;
Proposal of Watering Method for Waste Stabilization in
Closed System Landfill sites by Using a Washout Model,
Proceedings of the Third Asian-Pacific Landfill Symposiumin Kitakyusyu 2004,pp253-260(2004).

80000

C Cl100 [mg/L]

120000