stabilization of incineration residue and shredded
STABILIZATION OF INCINERATION RESIDUE AND SHREDDED INCOMBUSTIBLE WASTE USING ARTIFICIAL WATERING IN CLOSED SYSTEM DISPOSAL FACILITIES K. ISHII*, T. FURUICHI** AND M. HANASHIMA** * Faculty of Enfineering, Hokkaido University, N13, W8, Kita-ku, Spporo, 0608628, Japan ** The Landfill Systems and technolgoies Research Association of Japan, NPO, 401 Chateau Takanawa, 3-23-14, Takanawa, Minato-ku, Tokyo, 108-0074, Japan
SUMMARY: In Japan, the number of closed system disposal facilities (CSDFs) with roofs to prevent precipitation infiltrating into waste layers have increased because they are accepted by residents who are concerned about environment pollution around landfill sites. However, in CSDFs watering is needed to stabilize the landfilled waste. Watering promotes washing and biodegradation of pollutants within the landfilled wastes. This study describes the results from analysis of long-term monitoring data in actual CSDFs to verify whether landfilled wastes have been really stabilized or not, and to investigate how much water is really needed for waste stabilization and improvement in quality of leachate. The results of elution tests for landfilled waste, sampled for about 10 years and relationships between the quality of leachate and the ratio of leachate generation to landfilled waste in weight, are presented. This study shows that the cumulative discharge of pollutants, such as chemical oxygen demand, total nitrogen and chloride ion, thorugh leachate per cumulative waste, can be a useful index to compare the progress of waste stabilization among CSDFs.
1. INTRODUCTION It has become increasingly difficult recently to construct new landfill sites in Japan because of opposition from residents concerned about subsequent environmental pollution. Problems have arisen from groundwater pollution due to the leakage of leachate through landfill liners. Closed system disposal facilities (CSDFs) (Hanashima, 1990; Furuichi, 1998), which have roofs to prevent rainfall infiltrating waste layers, have gained popularity in Japan as environmental awareness has increased. At present, there are more than 60 CSDFs in Japan, including those under construction. Long-term post-closure care has been problematic and costly (e.g., leachate must be treated over a long period until it satisfies the Japanese effluent standard) at normal landfill sites (which we refer to as "open system disposal facilities; OSDFs) other than CSDFs. In CSDFs, conditions such as watering are controllable, which suggests the possibility of promoting the stabilization of waste or carrying out a less expensive operation in the leachate treatment facility (Ishii & Furuichi, 2011). If stabilization of the landfilled waste is accelerated by appropriate watering, the
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
amount of leachate to be treated might be reduced. At the present time, the desing of watering is based on the ratio of leachate generation (m 3) to waste (m3), according to “the points of planning, design and operation for landfill sites in Japan”, which shows all requirements for structure, liner systems, leachate treatment process and environmental monitoring in landfill sites. For example, the ratio of leachate to waste should be 1.5 to 3.0 until chemical oxygen demand (COD) concentration in the leachate decreases to 20 mg/L for incineration residue with less than 10% in ignition loss. However, the actual relationship between the ratio of leachate to waste and pollutant concentrations in leachate has not been observed yet, based on the observation data in actual CSDFs. We have collected a large quantity of field data on real CSDFs for over 10 years to investigate the degree of stabilization of landfilled waste (Ishii et al, 2009, 2011, 2013, 2016). The collected field data are, for example, data on the annual amount of landfilled waste, the amount of watering, the temperature within the waste layer, landfill gases, elution tests of waste samples, and leachate quality. The objectives of this study are 1) to assess waste stabilization processes in real CSDFs by sampling landfilled waste and 2) to clarify relationships between the ratio of leachate to waste and quality of leachate in terms of decrease in pollutants.
2. OBJECTIVE CSDFS AND METHOD OF DATA ANALYSIS 2.1 Objective CSDFs in this study CSDFs have a barrier, such as a roof, which prevents rainfall from infiltrating waste during operational and post-closure periods, as shown in Figure 1 (Furuichi et al., 2001, Ishii et al, 2009). For waste stabilization, artificial watering is conducted. Consequently, the generation of leachate is controlled, resulting in a lower likelihood of groundwater pollution due to the temporary storage of leachate within waste layers. Boundary
Rain
Wind Artificial rainfall and ventilation Temperature, Factors humidity dust Water odor, etc.
Waste controlled in terms of quantity and quality
Sunlight
Landfill gas Storage Recycling Vertical wall
waste liner
Stabilization
leachate
Groundwater
Vertical wall Base
Figure 1. Schematic diagram of a CSDF This study investigated seven CSDFs receiving incineration residue (bottom ash and fly ash), as shown in Table 1, which provided us with sufficient data for analysis. Especially in the B, C and D CSDFs, the same quality of waste has been landfilled because the incineration facility and shredding facility has been commonly used by the three municipalities.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Table 1. Description of objective closed system disposal facilities in this study Name of
B
CSDFs 2
Area (m ) 3
Volume (m ) Averaged depth (m)
C
D
E
F
G
H
1,770
900
1,000
11,700
2,100
4,128
4,808
5,982
3,825
4,000
77,700
15,657
27,000
37,000
3.8
4.3
4.0
6.6
7.5
6.5
7.7
4
4
5
24
13
3
15
2002
2002
2003
2005
2005
2008
2008
Capacity of leachate treatment 3
(m /d) Commence ment (FY)
Incineration residue
Landfilled waste
Incombustible residue and
Shredded incombustible
Treatment of
others
Organic chelator
fly ash
No answer
Organic chelator
Circulation of treated
No
No
No
No
Yes
Yes
Yes
Approx.1.5
Approx. 4
Approx. 2
Approx. 5.5
Approx. 9
Approx. 1.6
Approx. 15
leachate Watering 3
(m /d)
2.2 Method of data collection and analysis 2.2.1 Data common in all CSDFs The following data were collected from all CSDFs. § Annual amount of landfilled waste and waste type § Annual amount of watering, leachate generation and treated water § Quality of leachate, such as chemical oxygen demand employed manganese (COD(Mn)),
total nitrogen (T-N) or ammonia nitrogen and nitrate/nitrite nitrogen, and chloride ion All data were organized according to each fiscal year. For example, concentration data in leachate were averaged every fiscal year if there were multiple sets of data. If there was no data for specific fiscal years, the data was interpolated from those in the previous and subsequent fiscal years. 2.2.2 Data common only in C and D CSDFs Waste samples were collected from C and D CSDFs and elution tests (solid:liquid = 1:10, 6 hours shaking) were conducted. The sampling points were set at almost the same points as in the previous sampling. The waste samples were collected at a designated depth of the waste layer using a backhoe. In the elution test, total organic carbon (TOC) and the chloride ion concentration were determined. Landfill gas was also investigated, but the amount of landfill gas generation was very low because the landfilled waste is incineration residue and shredded incombustibles with a small
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
amount of biodegradable organic compounds. 2.2.3 Ratio of leachate to waste This study applied two definitions in the ratio of leachate to waste: 1) the ratio of leachate to waste based on a cumulative amount of landfilled waste and 2) the ratio of leachate to waste based on the capacity in planning. The ratio of leachate to cumulative waste is calculated from eq. (1). Ratio of leachate to cumulative waste in x FY= the cumulative amount of leachate generation (t) until x FY / the cumulative amount of landfilled waste until x FY (t)
(1)
During landfilling, if a constant amount of leachate is generated according to the amount of landfilled waste, the ratio of leachate to cumulative waste will not be changed. If the amount of leachate decreases due to a decrease in the amount of watering, the ratio will decrease. In the period of post-closure after completion of the landfilling, the ratio will increase if the watering constantly continues. The ratio of leachate to waste in planning is calculated by eq. (2). Ratio of leachate to waste based on the capacity in planning = the cumulative amount of leachate generation (t) until x FY / the capacity of landfill site in planning (t)
(2)
This ratio of leacahte of waste in planning defines in x FY how much watering must be done to reach the goal set in planning. In the post-closure period, the two ratios above of leachate to waste are the same.
3. RESULTS AND DISCUSSION 3.1 Elution tests of landfilled wastes Figure 2 shows the vertical distributions of TOC and chloride ion concentrations in the elution tests for waste sampled at each depth in D CSDF. In all the points from Point 1 to Point 4, from which waste was sampled, a survey clarified the time where waste had been landfilled from before 2010 to the summer of 2013. Both TOC and chloride ion concentrations decreased as time passed because of watering. Figures 3 and 4 show the vertical distributions of the TOC and chloride ion concentrations in C and D CSDFs, respectively. The waste was sampled from almost the same points from 2005 to 2012 in C CSDF, and from 2005 to 2014 in D CSDF. TOC concentrations in the elution test were relatively low because the landfilled waste is incineration residue and shredded incombustible waste but the concentration tended to decrease to less than 5 mg/L, as time passed. The decreasing mechanism was considered to be washing. Chloride ion concentration had a similar tendency to decrease to a few hundred mg/L over time. However the decreasing rate was slower than those for the TOC concentrations. Artificial watering is effective in decreasing TOC and chloride ion concentration within waste layers in CSDF.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Period of Landfilling - Point 1: 2013 summer - Point 2: 2013 spring - Point 3: 2012 - Point 4: before 2010
Height from the bottom (m)
5
6 5
Height from the bottom (m)
6
4 Point 1
3
Point 2 Point 3
2
Point 4
4 Point 1
3
Point 2 Pointt 3
2
Point 4
1
1
0
0 0
20
40
0
60
500
1000
1500
2000
Cl- concentration (mg/L)
TOC concentration (mg/L)
3
6
2.5
5
Investigation year 2 2005 2006
1.5
2007 2008
1
2010 2012
0.5
Height from the bottom (m)
Height from the bottom [m]
Figure 2. Results of elution tests in the investigation of D CSDF in 2014.
2005 2006
4
2007 2008
3
2010 2012 2013
2
2014① 2014③
1
2014⑤ 0 0
5
10
15
20
25
TOC concentration [mg/L]
2014②
0 0
20
40
60
TOC concentration (mg/L)
(a) C CSDF (b) D CSDF Figure 3. Distribution of TOC concentration in C and D CSDFs.
3
6
2.5
5
2 2005 2006
1.5
2007 2008
1
2010 2012
0.5
Height from the bottom (m)
Height from the bottom [m]
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
2005 2006
4
2007 2008
3
2010 2012 2013
2
2014① 2014③
1
2014⑤ 2014②
0
0 0
500
1000
0
1500
1000 2000 3000 4000 5000
Cl- concentration (mg/L)
Cl- concentration [mg/L]
(a) C CSDF (b) D CSDF Figure 4. Distribution of chloride ion concentration in C and D CSDFs. 3.2 Ratio of leachate to waste
Ratio of leachate of cumulative waste (t/t)
Figures 5 and 6 show the changes in the ratio of leachate to cumulative waste and to waste in planning, respectively. These graphs provide information on annual watering. In B, C and H CSDFs, the ratio of leachate to cumulative water was kept relatively high. Especially in C CSDF, the aomount of water supplied over the last few years has been three times the amount of waste. In G CSDF, very little water was supplied. With regards to the ratio of leachate to waste in planning, in C CSDF, the water already supplied is about 1.2 times the volume of the capacity of the landfill site. On the other hand, in G CSDF, the water supplied into the waste layer was less than 10%. 4 3.5 3 2.5 2
1.5 1 0.5 0 0
1 B
2
3 4 5 6 7 8 9 10 11 Elapsed time from commencement (y) C
D
E
F
Figure 5. Change in the ratio of leachate to cumulative waste
12 G
13
14 H
15
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Ratio of leachate of waste in planning (t/t)
1.4 1.2 1
0.8 0.6 0.4 0.2 0 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Elapsed time from commencement (y) B
C
D
E
F
G
H
Figure 6. Change in the ratio of leachate to waste in planning 3.3 Relationship between leachate quality and the ratio of leachate to waste
COD(Mn) concentration (mg/L)
Figures 7, 8 and 9 show the relationships between COD, nitrogen concentration and chloride ion concentration and the ratio of leachate to cumulative waste, respectively. These pollutant concentrations are determined by pollutant transfer rate to the liquid phase and the amount of leachate generation. In many cases, where the pollutant transfer rate to the liquid is limited, the pollutant concentration in leachate will decrease with an increase in the ratio of leachate to cumulative waste. According to Figures 7,8 and 9, the COD, nitrogen and chloride ion concentrations tended to decrease with an increase in the ratio of leachate to cumulative waste as expected. For example, COD concentration in leachate decreased to less than 50 mg/L when the ratio of leachate to cumulative waste reached 1.0. However, even when the ratio of leachate to cumulative waste reached 2.0 or 3.0, the COD concentration did not decrease as significantly. It is noted that movement of the landfilled waste within the facility caused a peak in the COD concentration with the ratio of leachate to cummlative waste of around 1.4 in D CSDF. All data was obtained during the period of landfilling, and not pos-tclosure after the completion of the landfilling. It is possible that the concentration may decrease further after the completion of the landfilling. 250
200 150 100 50 0
0
0.5
1
1.5
2
2.5
3
3.5
4
Ratio of leachate of cumulative waste (t/t) B
C
D
E
F
G
H
Figure 7. Relationship between COD(Mn) concentration and the ratio of leachate to cumulative waste
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Nitrogen concentration (mg/L)
Nitrogen concentration, such as total nitrogen or ammonia, nitrate and nitrite nitrogen, had the same tendency to decrease with an increase in the ratio of leachate to cumulative waste, as is shown in Figure 8. When the ratio of leachate to cumulative waste reached 2.0, the nitrogen concentration decreased to 40 mg/L, However, in C CSDF, although the ratio was high at around 3.0, the nitrogen concentration was still high and more than the 60 mg/L which is the effluent standard in Japan. The nitrogen components were mainly nitrate and the T-N concentration was almost the same as for nitrate, which means the organic nitrogen concentration was expected to be very low. The reason why the nitrogen concentration was so high in C CSDF should be clarified by further investigations. 160 140 120 100 80 60 40 20 0 0
0.5
1
1.5
2
2.5
3
3.5
4
Ratio of leachate of cumulative waste (t/t) B
C
D
Ammonia, nitrate and nitrite nitrogen
E
F
G
Total nitrogen
Figure 8. Relationship between nitrogen concentration and the ratio of leachate to cumulative waste
Chloride ion concentration (mg/L)
Chloride ion concentration also had the same tendency to decrease with an increase in the ratio of leachate to cumulative waste, as is shown in Figure 9. In Japan, the effluent standard of chloride ion concentration from landfill sites is not set. However, in cases where downstream river water is used for agriculture, a chloride concentration limit of 500 mg/L for discharge into river is often applied. If 500 mg/L is applied as a reference, a ratio of more than 3.0 will not be able to decrease the chloride concentration in leachate to less than 500 mg/L. Further watering is needed to reach this value . 25,000 20,000 15,000
10,000 5,000 0 0
0.5 B
1 1.5 2 2.5 3 Ratio of leachate of cumulative waste (t/t) C D E
3.5
4
Figure 9. Relationship between chloride ion concentration and the ratio of leachat to cumulative waste Figure 10 shows the relationship between the cumulative discharge of COD(Mn) and the ratio of leachate to waste in planning. This relationship gives the transfer rate of pollutants to
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Cumulative discharge of COD(Mn) (kg)
leachate. If the gradient of the plots becomes small, the transfer rate also decreases, which means that discharge of COD from the waste through leachate will countine in all CSDFs. The cumulative discharge of COD in E, G and H CSDFS appeared to be larger than those in other CSDFs. However, this relationship did not consider the amount of landfilled waste and we cannot compare the data of the CSDFs. The cumulative discharge of COD should be changed to the cumulative discharge of COD per cumulative waste, as shown in Figure 11, in order to compare the transfer rate of COD to the liquid phase among CSDFs. In Figure 11, the trasnfer rate of COD to the liquid phase in C CSDF was the largest. Movement and mixing of landfilled waste within the facility was often conducted, which may promote the trasnfer of COD to the liquid phase. There is a sudden increase of about 0.7 in the ratio of leachate of waste in planning in D CSDF, this is because the landfilled waste was moved and relocated within the facility. The value of the cumulative discharge of COD per cumulative waste seems to be a sitespecific value, determined by the kinds of landfilled wastes and operations such as landfilling works, compaction, watering, etc. 700 600 500
400 300 200 100
0 0
0.2 B
C
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) D
E
F
G
1.2
1.4
H
Cumulative discharge of COD (Mn) based on cummlative waste (kg/t)
Figure 10. Relationship between cumulative discharge of COD(Mn) and the ratio of leachate to waste in planning 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 0
0.2 B
C
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) D
E
F
G
1.2
1.4
H
Figure 11. Relationship between cumulative discharge of COD(Mn) per cumulative waste and the ratio of leachate to waste in planning
Figure 12 shows the relationship between the cumulative discharge of nitrogen and the ratio of leachate to waste in planning, which also shows nitrogen discharge through leachate will
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Cumulative discharge of Nitrogen (kg)
continue. As shown in Figure 13, the cumulative discharge of nitrogen per cumulative waste in C CSDF was also the largest among the CSDFs. In C and D CSDFs, most nitrogen was nitrate, which seemed to be generated by mineralization of organic nitrogen within the landfilled waste. On the other hand, T-N in E, F and G CSDFs might be derived from organic chelate used for the treatment of fly ash to prevent heavy metals from leaching. In prticular, the cumulative discharge of nitrogen per cumulative waste in F CSDF continued to increase as landfilling progressed. 600 500
400 300 200 100 0 0
0.2 B
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t)
C
D
E
Ammonia, nitrate and nitrite nitrogen
F
1.2
1.4
G
Total nitrogen
Cumulative discharge of nitrogen based on cummlative waste (kg/t)
Figure 12. Relationship between cumulative discharge of nitrogen and the ratio of leachate to waste in planning 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 0
0.2 B
C
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) D
Ammonia, nitrate and nitrite nitrogen
E
F
1.2
1.4
G
Total nitrogen
Figure 13. Relationship between cumulative discharge of nitrogen per cumulative waste and the ratio of leachate to waste in planning Figure 14 shows the relationship between cumulative discharge of chloride ion and the ratio of leachate to waste in planning in B, C, and D CSDFs, where sufficient data was obtained. Chloride ion will also continue to discharge through leachate in future. These three facilities received the same quality of wastes from the incineration facility and shredding facility. We can therefore easily compare the transfer rate of chloride ion to the liquid phase. As shown in Figure 15, the cumullative discharges of chloride ion per cumulative waste in B and C CSDFs were almost the same, but that in D CSDF was marginally lower. This fact seemed to reflect actual and site-specific landfilling operations. For example, the density of landfilled waste in D CSDF seemed to be larger than that in C CSDF because the heavy machines used for working in D CSDF are larger than those in C CSDF. Further investigation will be required to clarify these differences between the CSDFs with reagard to the site-specific values of the cumulative discharge of pollutants per cumulative waste.
Cumulative discharge of chloride ion (kg)
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 0
0.2
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) B
C
1.2
1.4
D
Cumulative discharge of chloride ion based on cummlative waste (kg/t)
Figure 14. Relationship between cumulative discharge of chloride ion and the ratio of leachate to waste in planning 14.00
12.00 10.00 8.00 6.00
4.00 2.00 0.00
0
0.2 B
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) C
1.2
1.4
D
Figure 15. Relationship between cumulative discharge of chloride ion per cumulative waste and the ratio of leachate to waste in planning
4. CONCLUSIONS The study resulted in the following conclusions from the analyses of long-term monitoring field data in actual CSDFs. 1. Artificial watering is effective for decreasing TOC and chloride ion that can be eluted from landfilled waste in CSDFs. 2. The relationships between the leachate quality, such as COD(Mn), nitrogen and chloride ion concentrations, and the ratio of leachate generation to waste were clarified based on the field data. 3. In particular, the curve of the cumulative discharge of pollutants through leachate vs the ratio of leachate to waste in planning can be used to evaluate the degree of continuous discharge in the future. Considering leachate generation, this will help the prediction of the leachate quality in CSDFs. 4. The cumulative discharge of pollutants per the cumulative waste is a site-specific index that can be affected by the kinds of landfill wastes, landfilling operations such as compaction,
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
daily covers, watering (quantity and frequency), and regional conditions such as climate conditions.
ACKNOWLEDGEMENTS Field data was collected by the nonprofit Landfill Systems Association (LSA). We thank all administrators at the CSDFs referred to in this study and also members of the CSDF research group.
REFERENCES Furuichi, T. (1998): Concept of Community Based Landfill, Journal of Japan Waste Management Association (JWMA), Vol. 51, No. 225, pp. 347- 353. Furuichi, T., Ishii K., and Kotani, K. (2001). Feasibility Studies on Community and Controllable Closed System Disposal Facilities, Proceedings of Sardinia 2001, Vol. 1, pp. 329-338. Hanashima, M. (1990): Proposal of the Closed System Disposal Site, Waste Management Research, Vol. 1, No. 1, pp. 38-42. Ishii, K., Furuichi, T., and Tanikawa N. (2009). Numerical Model for a Watering Plan to Wash out Organic Matter from the Municipal Solid Waste Incinerator Bottom Ash Layer in Closed System Disposal Facilities, Waste Management, 29, pp. 513-521. Ishii, K., Furuichi, t. (2011). Field Studies of Stabilizing the Waste in Closed System Disposal Facilities, The Proceedings of Sardinia 2011, CD-ROM, 2011. Ishii, K., Wakabayashi, H., Shoji, S., Furuichi T. and Hanashima, M. (2013). Field Investigation on Stabilizing Waste in Closed System Disposal Facilities in Japan, The Proceedings of Sardinia 2013, CD-ROM, 2013. Ishii, K., Furuichi, T. and Hanashima, M. (2016). Analysis of Long-term Data on Stabilization of Incineration Residue and Shredded Incombustible Waste in Closed System Disposal Facilities, Ninth Intercontinental Landfill Research Symposium, Noboribetsu, Japan, 2016. Feng J. and Johnston D. (1991). Electrocatalysis of anodic oxygen - transfer reaction: titanium substrates for pure and doped Lead dixide film. J. Electrode Soc., vol. 138, n. 11, 3328-3337. Fraser J.A.L. and Sims A.F.E. (1984). Hydrogen peroxide in municipal landfill and industrial effluent treatment. Effluent Water Treat., vol. 24, 184-188. Cit. in Kylefors, 1997. Kylefors K. (1997). Landfill Leachate Management. Licentiate Thesis, The Landfill Group, Lulea University of Technology, 1997, 16 L. Li-Choung Chiang, Juu-En Chang and Ten-Chin Wen (1995). Indirect oxidation effect in Electrochemical oxidation treatment of landfill leachate, Wat. Res., vol. 29, n. 2, 671-678. Steensen M. (1993). Removal of non biodegradable organics from leachate by chemical oxidation. Proceedings Sardinia 93, Fourth International landfill Symposium, CISA publisher, Cagliari, vol. I, 945-958.
SUMMARY: In Japan, the number of closed system disposal facilities (CSDFs) with roofs to prevent precipitation infiltrating into waste layers have increased because they are accepted by residents who are concerned about environment pollution around landfill sites. However, in CSDFs watering is needed to stabilize the landfilled waste. Watering promotes washing and biodegradation of pollutants within the landfilled wastes. This study describes the results from analysis of long-term monitoring data in actual CSDFs to verify whether landfilled wastes have been really stabilized or not, and to investigate how much water is really needed for waste stabilization and improvement in quality of leachate. The results of elution tests for landfilled waste, sampled for about 10 years and relationships between the quality of leachate and the ratio of leachate generation to landfilled waste in weight, are presented. This study shows that the cumulative discharge of pollutants, such as chemical oxygen demand, total nitrogen and chloride ion, thorugh leachate per cumulative waste, can be a useful index to compare the progress of waste stabilization among CSDFs.
1. INTRODUCTION It has become increasingly difficult recently to construct new landfill sites in Japan because of opposition from residents concerned about subsequent environmental pollution. Problems have arisen from groundwater pollution due to the leakage of leachate through landfill liners. Closed system disposal facilities (CSDFs) (Hanashima, 1990; Furuichi, 1998), which have roofs to prevent rainfall infiltrating waste layers, have gained popularity in Japan as environmental awareness has increased. At present, there are more than 60 CSDFs in Japan, including those under construction. Long-term post-closure care has been problematic and costly (e.g., leachate must be treated over a long period until it satisfies the Japanese effluent standard) at normal landfill sites (which we refer to as "open system disposal facilities; OSDFs) other than CSDFs. In CSDFs, conditions such as watering are controllable, which suggests the possibility of promoting the stabilization of waste or carrying out a less expensive operation in the leachate treatment facility (Ishii & Furuichi, 2011). If stabilization of the landfilled waste is accelerated by appropriate watering, the
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
amount of leachate to be treated might be reduced. At the present time, the desing of watering is based on the ratio of leachate generation (m 3) to waste (m3), according to “the points of planning, design and operation for landfill sites in Japan”, which shows all requirements for structure, liner systems, leachate treatment process and environmental monitoring in landfill sites. For example, the ratio of leachate to waste should be 1.5 to 3.0 until chemical oxygen demand (COD) concentration in the leachate decreases to 20 mg/L for incineration residue with less than 10% in ignition loss. However, the actual relationship between the ratio of leachate to waste and pollutant concentrations in leachate has not been observed yet, based on the observation data in actual CSDFs. We have collected a large quantity of field data on real CSDFs for over 10 years to investigate the degree of stabilization of landfilled waste (Ishii et al, 2009, 2011, 2013, 2016). The collected field data are, for example, data on the annual amount of landfilled waste, the amount of watering, the temperature within the waste layer, landfill gases, elution tests of waste samples, and leachate quality. The objectives of this study are 1) to assess waste stabilization processes in real CSDFs by sampling landfilled waste and 2) to clarify relationships between the ratio of leachate to waste and quality of leachate in terms of decrease in pollutants.
2. OBJECTIVE CSDFS AND METHOD OF DATA ANALYSIS 2.1 Objective CSDFs in this study CSDFs have a barrier, such as a roof, which prevents rainfall from infiltrating waste during operational and post-closure periods, as shown in Figure 1 (Furuichi et al., 2001, Ishii et al, 2009). For waste stabilization, artificial watering is conducted. Consequently, the generation of leachate is controlled, resulting in a lower likelihood of groundwater pollution due to the temporary storage of leachate within waste layers. Boundary
Rain
Wind Artificial rainfall and ventilation Temperature, Factors humidity dust Water odor, etc.
Waste controlled in terms of quantity and quality
Sunlight
Landfill gas Storage Recycling Vertical wall
waste liner
Stabilization
leachate
Groundwater
Vertical wall Base
Figure 1. Schematic diagram of a CSDF This study investigated seven CSDFs receiving incineration residue (bottom ash and fly ash), as shown in Table 1, which provided us with sufficient data for analysis. Especially in the B, C and D CSDFs, the same quality of waste has been landfilled because the incineration facility and shredding facility has been commonly used by the three municipalities.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Table 1. Description of objective closed system disposal facilities in this study Name of
B
CSDFs 2
Area (m ) 3
Volume (m ) Averaged depth (m)
C
D
E
F
G
H
1,770
900
1,000
11,700
2,100
4,128
4,808
5,982
3,825
4,000
77,700
15,657
27,000
37,000
3.8
4.3
4.0
6.6
7.5
6.5
7.7
4
4
5
24
13
3
15
2002
2002
2003
2005
2005
2008
2008
Capacity of leachate treatment 3
(m /d) Commence ment (FY)
Incineration residue
Landfilled waste
Incombustible residue and
Shredded incombustible
Treatment of
others
Organic chelator
fly ash
No answer
Organic chelator
Circulation of treated
No
No
No
No
Yes
Yes
Yes
Approx.1.5
Approx. 4
Approx. 2
Approx. 5.5
Approx. 9
Approx. 1.6
Approx. 15
leachate Watering 3
(m /d)
2.2 Method of data collection and analysis 2.2.1 Data common in all CSDFs The following data were collected from all CSDFs. § Annual amount of landfilled waste and waste type § Annual amount of watering, leachate generation and treated water § Quality of leachate, such as chemical oxygen demand employed manganese (COD(Mn)),
total nitrogen (T-N) or ammonia nitrogen and nitrate/nitrite nitrogen, and chloride ion All data were organized according to each fiscal year. For example, concentration data in leachate were averaged every fiscal year if there were multiple sets of data. If there was no data for specific fiscal years, the data was interpolated from those in the previous and subsequent fiscal years. 2.2.2 Data common only in C and D CSDFs Waste samples were collected from C and D CSDFs and elution tests (solid:liquid = 1:10, 6 hours shaking) were conducted. The sampling points were set at almost the same points as in the previous sampling. The waste samples were collected at a designated depth of the waste layer using a backhoe. In the elution test, total organic carbon (TOC) and the chloride ion concentration were determined. Landfill gas was also investigated, but the amount of landfill gas generation was very low because the landfilled waste is incineration residue and shredded incombustibles with a small
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
amount of biodegradable organic compounds. 2.2.3 Ratio of leachate to waste This study applied two definitions in the ratio of leachate to waste: 1) the ratio of leachate to waste based on a cumulative amount of landfilled waste and 2) the ratio of leachate to waste based on the capacity in planning. The ratio of leachate to cumulative waste is calculated from eq. (1). Ratio of leachate to cumulative waste in x FY= the cumulative amount of leachate generation (t) until x FY / the cumulative amount of landfilled waste until x FY (t)
(1)
During landfilling, if a constant amount of leachate is generated according to the amount of landfilled waste, the ratio of leachate to cumulative waste will not be changed. If the amount of leachate decreases due to a decrease in the amount of watering, the ratio will decrease. In the period of post-closure after completion of the landfilling, the ratio will increase if the watering constantly continues. The ratio of leachate to waste in planning is calculated by eq. (2). Ratio of leachate to waste based on the capacity in planning = the cumulative amount of leachate generation (t) until x FY / the capacity of landfill site in planning (t)
(2)
This ratio of leacahte of waste in planning defines in x FY how much watering must be done to reach the goal set in planning. In the post-closure period, the two ratios above of leachate to waste are the same.
3. RESULTS AND DISCUSSION 3.1 Elution tests of landfilled wastes Figure 2 shows the vertical distributions of TOC and chloride ion concentrations in the elution tests for waste sampled at each depth in D CSDF. In all the points from Point 1 to Point 4, from which waste was sampled, a survey clarified the time where waste had been landfilled from before 2010 to the summer of 2013. Both TOC and chloride ion concentrations decreased as time passed because of watering. Figures 3 and 4 show the vertical distributions of the TOC and chloride ion concentrations in C and D CSDFs, respectively. The waste was sampled from almost the same points from 2005 to 2012 in C CSDF, and from 2005 to 2014 in D CSDF. TOC concentrations in the elution test were relatively low because the landfilled waste is incineration residue and shredded incombustible waste but the concentration tended to decrease to less than 5 mg/L, as time passed. The decreasing mechanism was considered to be washing. Chloride ion concentration had a similar tendency to decrease to a few hundred mg/L over time. However the decreasing rate was slower than those for the TOC concentrations. Artificial watering is effective in decreasing TOC and chloride ion concentration within waste layers in CSDF.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Period of Landfilling - Point 1: 2013 summer - Point 2: 2013 spring - Point 3: 2012 - Point 4: before 2010
Height from the bottom (m)
5
6 5
Height from the bottom (m)
6
4 Point 1
3
Point 2 Point 3
2
Point 4
4 Point 1
3
Point 2 Pointt 3
2
Point 4
1
1
0
0 0
20
40
0
60
500
1000
1500
2000
Cl- concentration (mg/L)
TOC concentration (mg/L)
3
6
2.5
5
Investigation year 2 2005 2006
1.5
2007 2008
1
2010 2012
0.5
Height from the bottom (m)
Height from the bottom [m]
Figure 2. Results of elution tests in the investigation of D CSDF in 2014.
2005 2006
4
2007 2008
3
2010 2012 2013
2
2014① 2014③
1
2014⑤ 0 0
5
10
15
20
25
TOC concentration [mg/L]
2014②
0 0
20
40
60
TOC concentration (mg/L)
(a) C CSDF (b) D CSDF Figure 3. Distribution of TOC concentration in C and D CSDFs.
3
6
2.5
5
2 2005 2006
1.5
2007 2008
1
2010 2012
0.5
Height from the bottom (m)
Height from the bottom [m]
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
2005 2006
4
2007 2008
3
2010 2012 2013
2
2014① 2014③
1
2014⑤ 2014②
0
0 0
500
1000
0
1500
1000 2000 3000 4000 5000
Cl- concentration (mg/L)
Cl- concentration [mg/L]
(a) C CSDF (b) D CSDF Figure 4. Distribution of chloride ion concentration in C and D CSDFs. 3.2 Ratio of leachate to waste
Ratio of leachate of cumulative waste (t/t)
Figures 5 and 6 show the changes in the ratio of leachate to cumulative waste and to waste in planning, respectively. These graphs provide information on annual watering. In B, C and H CSDFs, the ratio of leachate to cumulative water was kept relatively high. Especially in C CSDF, the aomount of water supplied over the last few years has been three times the amount of waste. In G CSDF, very little water was supplied. With regards to the ratio of leachate to waste in planning, in C CSDF, the water already supplied is about 1.2 times the volume of the capacity of the landfill site. On the other hand, in G CSDF, the water supplied into the waste layer was less than 10%. 4 3.5 3 2.5 2
1.5 1 0.5 0 0
1 B
2
3 4 5 6 7 8 9 10 11 Elapsed time from commencement (y) C
D
E
F
Figure 5. Change in the ratio of leachate to cumulative waste
12 G
13
14 H
15
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Ratio of leachate of waste in planning (t/t)
1.4 1.2 1
0.8 0.6 0.4 0.2 0 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Elapsed time from commencement (y) B
C
D
E
F
G
H
Figure 6. Change in the ratio of leachate to waste in planning 3.3 Relationship between leachate quality and the ratio of leachate to waste
COD(Mn) concentration (mg/L)
Figures 7, 8 and 9 show the relationships between COD, nitrogen concentration and chloride ion concentration and the ratio of leachate to cumulative waste, respectively. These pollutant concentrations are determined by pollutant transfer rate to the liquid phase and the amount of leachate generation. In many cases, where the pollutant transfer rate to the liquid is limited, the pollutant concentration in leachate will decrease with an increase in the ratio of leachate to cumulative waste. According to Figures 7,8 and 9, the COD, nitrogen and chloride ion concentrations tended to decrease with an increase in the ratio of leachate to cumulative waste as expected. For example, COD concentration in leachate decreased to less than 50 mg/L when the ratio of leachate to cumulative waste reached 1.0. However, even when the ratio of leachate to cumulative waste reached 2.0 or 3.0, the COD concentration did not decrease as significantly. It is noted that movement of the landfilled waste within the facility caused a peak in the COD concentration with the ratio of leachate to cummlative waste of around 1.4 in D CSDF. All data was obtained during the period of landfilling, and not pos-tclosure after the completion of the landfilling. It is possible that the concentration may decrease further after the completion of the landfilling. 250
200 150 100 50 0
0
0.5
1
1.5
2
2.5
3
3.5
4
Ratio of leachate of cumulative waste (t/t) B
C
D
E
F
G
H
Figure 7. Relationship between COD(Mn) concentration and the ratio of leachate to cumulative waste
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Nitrogen concentration (mg/L)
Nitrogen concentration, such as total nitrogen or ammonia, nitrate and nitrite nitrogen, had the same tendency to decrease with an increase in the ratio of leachate to cumulative waste, as is shown in Figure 8. When the ratio of leachate to cumulative waste reached 2.0, the nitrogen concentration decreased to 40 mg/L, However, in C CSDF, although the ratio was high at around 3.0, the nitrogen concentration was still high and more than the 60 mg/L which is the effluent standard in Japan. The nitrogen components were mainly nitrate and the T-N concentration was almost the same as for nitrate, which means the organic nitrogen concentration was expected to be very low. The reason why the nitrogen concentration was so high in C CSDF should be clarified by further investigations. 160 140 120 100 80 60 40 20 0 0
0.5
1
1.5
2
2.5
3
3.5
4
Ratio of leachate of cumulative waste (t/t) B
C
D
Ammonia, nitrate and nitrite nitrogen
E
F
G
Total nitrogen
Figure 8. Relationship between nitrogen concentration and the ratio of leachate to cumulative waste
Chloride ion concentration (mg/L)
Chloride ion concentration also had the same tendency to decrease with an increase in the ratio of leachate to cumulative waste, as is shown in Figure 9. In Japan, the effluent standard of chloride ion concentration from landfill sites is not set. However, in cases where downstream river water is used for agriculture, a chloride concentration limit of 500 mg/L for discharge into river is often applied. If 500 mg/L is applied as a reference, a ratio of more than 3.0 will not be able to decrease the chloride concentration in leachate to less than 500 mg/L. Further watering is needed to reach this value . 25,000 20,000 15,000
10,000 5,000 0 0
0.5 B
1 1.5 2 2.5 3 Ratio of leachate of cumulative waste (t/t) C D E
3.5
4
Figure 9. Relationship between chloride ion concentration and the ratio of leachat to cumulative waste Figure 10 shows the relationship between the cumulative discharge of COD(Mn) and the ratio of leachate to waste in planning. This relationship gives the transfer rate of pollutants to
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Cumulative discharge of COD(Mn) (kg)
leachate. If the gradient of the plots becomes small, the transfer rate also decreases, which means that discharge of COD from the waste through leachate will countine in all CSDFs. The cumulative discharge of COD in E, G and H CSDFS appeared to be larger than those in other CSDFs. However, this relationship did not consider the amount of landfilled waste and we cannot compare the data of the CSDFs. The cumulative discharge of COD should be changed to the cumulative discharge of COD per cumulative waste, as shown in Figure 11, in order to compare the transfer rate of COD to the liquid phase among CSDFs. In Figure 11, the trasnfer rate of COD to the liquid phase in C CSDF was the largest. Movement and mixing of landfilled waste within the facility was often conducted, which may promote the trasnfer of COD to the liquid phase. There is a sudden increase of about 0.7 in the ratio of leachate of waste in planning in D CSDF, this is because the landfilled waste was moved and relocated within the facility. The value of the cumulative discharge of COD per cumulative waste seems to be a sitespecific value, determined by the kinds of landfilled wastes and operations such as landfilling works, compaction, watering, etc. 700 600 500
400 300 200 100
0 0
0.2 B
C
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) D
E
F
G
1.2
1.4
H
Cumulative discharge of COD (Mn) based on cummlative waste (kg/t)
Figure 10. Relationship between cumulative discharge of COD(Mn) and the ratio of leachate to waste in planning 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 0
0.2 B
C
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) D
E
F
G
1.2
1.4
H
Figure 11. Relationship between cumulative discharge of COD(Mn) per cumulative waste and the ratio of leachate to waste in planning
Figure 12 shows the relationship between the cumulative discharge of nitrogen and the ratio of leachate to waste in planning, which also shows nitrogen discharge through leachate will
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Cumulative discharge of Nitrogen (kg)
continue. As shown in Figure 13, the cumulative discharge of nitrogen per cumulative waste in C CSDF was also the largest among the CSDFs. In C and D CSDFs, most nitrogen was nitrate, which seemed to be generated by mineralization of organic nitrogen within the landfilled waste. On the other hand, T-N in E, F and G CSDFs might be derived from organic chelate used for the treatment of fly ash to prevent heavy metals from leaching. In prticular, the cumulative discharge of nitrogen per cumulative waste in F CSDF continued to increase as landfilling progressed. 600 500
400 300 200 100 0 0
0.2 B
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t)
C
D
E
Ammonia, nitrate and nitrite nitrogen
F
1.2
1.4
G
Total nitrogen
Cumulative discharge of nitrogen based on cummlative waste (kg/t)
Figure 12. Relationship between cumulative discharge of nitrogen and the ratio of leachate to waste in planning 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 0
0.2 B
C
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) D
Ammonia, nitrate and nitrite nitrogen
E
F
1.2
1.4
G
Total nitrogen
Figure 13. Relationship between cumulative discharge of nitrogen per cumulative waste and the ratio of leachate to waste in planning Figure 14 shows the relationship between cumulative discharge of chloride ion and the ratio of leachate to waste in planning in B, C, and D CSDFs, where sufficient data was obtained. Chloride ion will also continue to discharge through leachate in future. These three facilities received the same quality of wastes from the incineration facility and shredding facility. We can therefore easily compare the transfer rate of chloride ion to the liquid phase. As shown in Figure 15, the cumullative discharges of chloride ion per cumulative waste in B and C CSDFs were almost the same, but that in D CSDF was marginally lower. This fact seemed to reflect actual and site-specific landfilling operations. For example, the density of landfilled waste in D CSDF seemed to be larger than that in C CSDF because the heavy machines used for working in D CSDF are larger than those in C CSDF. Further investigation will be required to clarify these differences between the CSDFs with reagard to the site-specific values of the cumulative discharge of pollutants per cumulative waste.
Cumulative discharge of chloride ion (kg)
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 0
0.2
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) B
C
1.2
1.4
D
Cumulative discharge of chloride ion based on cummlative waste (kg/t)
Figure 14. Relationship between cumulative discharge of chloride ion and the ratio of leachate to waste in planning 14.00
12.00 10.00 8.00 6.00
4.00 2.00 0.00
0
0.2 B
0.4 0.6 0.8 1 Ratio of leachate of waste in planning (t/t) C
1.2
1.4
D
Figure 15. Relationship between cumulative discharge of chloride ion per cumulative waste and the ratio of leachate to waste in planning
4. CONCLUSIONS The study resulted in the following conclusions from the analyses of long-term monitoring field data in actual CSDFs. 1. Artificial watering is effective for decreasing TOC and chloride ion that can be eluted from landfilled waste in CSDFs. 2. The relationships between the leachate quality, such as COD(Mn), nitrogen and chloride ion concentrations, and the ratio of leachate generation to waste were clarified based on the field data. 3. In particular, the curve of the cumulative discharge of pollutants through leachate vs the ratio of leachate to waste in planning can be used to evaluate the degree of continuous discharge in the future. Considering leachate generation, this will help the prediction of the leachate quality in CSDFs. 4. The cumulative discharge of pollutants per the cumulative waste is a site-specific index that can be affected by the kinds of landfill wastes, landfilling operations such as compaction,
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
daily covers, watering (quantity and frequency), and regional conditions such as climate conditions.
ACKNOWLEDGEMENTS Field data was collected by the nonprofit Landfill Systems Association (LSA). We thank all administrators at the CSDFs referred to in this study and also members of the CSDF research group.
REFERENCES Furuichi, T. (1998): Concept of Community Based Landfill, Journal of Japan Waste Management Association (JWMA), Vol. 51, No. 225, pp. 347- 353. Furuichi, T., Ishii K., and Kotani, K. (2001). Feasibility Studies on Community and Controllable Closed System Disposal Facilities, Proceedings of Sardinia 2001, Vol. 1, pp. 329-338. Hanashima, M. (1990): Proposal of the Closed System Disposal Site, Waste Management Research, Vol. 1, No. 1, pp. 38-42. Ishii, K., Furuichi, T., and Tanikawa N. (2009). Numerical Model for a Watering Plan to Wash out Organic Matter from the Municipal Solid Waste Incinerator Bottom Ash Layer in Closed System Disposal Facilities, Waste Management, 29, pp. 513-521. Ishii, K., Furuichi, t. (2011). Field Studies of Stabilizing the Waste in Closed System Disposal Facilities, The Proceedings of Sardinia 2011, CD-ROM, 2011. Ishii, K., Wakabayashi, H., Shoji, S., Furuichi T. and Hanashima, M. (2013). Field Investigation on Stabilizing Waste in Closed System Disposal Facilities in Japan, The Proceedings of Sardinia 2013, CD-ROM, 2013. Ishii, K., Furuichi, T. and Hanashima, M. (2016). Analysis of Long-term Data on Stabilization of Incineration Residue and Shredded Incombustible Waste in Closed System Disposal Facilities, Ninth Intercontinental Landfill Research Symposium, Noboribetsu, Japan, 2016. Feng J. and Johnston D. (1991). Electrocatalysis of anodic oxygen - transfer reaction: titanium substrates for pure and doped Lead dixide film. J. Electrode Soc., vol. 138, n. 11, 3328-3337. Fraser J.A.L. and Sims A.F.E. (1984). Hydrogen peroxide in municipal landfill and industrial effluent treatment. Effluent Water Treat., vol. 24, 184-188. Cit. in Kylefors, 1997. Kylefors K. (1997). Landfill Leachate Management. Licentiate Thesis, The Landfill Group, Lulea University of Technology, 1997, 16 L. Li-Choung Chiang, Juu-En Chang and Ten-Chin Wen (1995). Indirect oxidation effect in Electrochemical oxidation treatment of landfill leachate, Wat. Res., vol. 29, n. 2, 671-678. Steensen M. (1993). Removal of non biodegradable organics from leachate by chemical oxidation. Proceedings Sardinia 93, Fourth International landfill Symposium, CISA publisher, Cagliari, vol. I, 945-958.
