3009
Geo-environmental problems in landfills of MSW with high organic content
Problèmes géo-environnementaux dans les sites d'enfouissement de déchets urbains à hautes
teneurs organiques
Chen Y.M., Zhan L.T., Xu X.B., Liu H.L.
MOE key Laboratory of Soft Soils and Geo-environmental Engineering, Zhejiang University, Hangzhou 310058, China
ABSTRACT: The municipal solid wastes (MSWs) in China are high in organic and moisture content, as compared with the MSWs in
developed countries. Large amounts of leachate and landfill gas are generated and significant settlement takes place during the
decomposition process of the MSWs. A build-up of leachate mound and gas pressure might take place in the landfills of MSWs.
Waste stability is highly concerned for such landfills having excessive pore-water and pore-gas pressure. A bio-hydro-mechanical
coupled model is presented in this paper, based on laboratory and in-situ investigations, to predict leachate production, gas pressure
and settlement. Based on the prediction obtained by the proposed model, discussions are made on the geo-environmental problems in
landfills of MSW with high organic content. The work is valuable for the development of bioreactor landfilling technologies in the
Asian developing countries such as China.
RÉSUMÉ : Les déchets urbains en Chine ont des teneurs élevées en matières organiques et en humidité, par rapport aux déchets
produits dans les pays développés. De grandes quantités de lixiviats et de gaz sont dégagées et un tassement significatif apparait lors
du processus de décomposition des déchets. Il peut se produire dans les décharges une augmentation de l’accumulation des lixiviats et
de la montée en pression des gaz. La stabilité de l’entreposage de ces déchets est fortement impactée par l’augmentation de pression
du fluide et du gaz dans les vides. Un modèle couplé bio-hydro-mécanique est proposé dans cet article, basé sur des études
expérimentales de laboratoire et in situ, pour prévoir la production de lixiviat, la pression de gaz et le tassement. Sur la base des
résultats obtenus par le modèle proposé, les discussions portent sur les problèmes géo-environnementaux dans les sites
d'enfouissement de déchets à hautes teneurs organiques. Le travail est très utile pour le développement des technologies de
bioréacteurs dans les pays asiatiques en voie de développement telle que la Chine.
KEYWORDS: MSW, organic content, gas, leachate, settlement, stability
1 INTRODUCTION.
Municipal Solid Wastes (MSWs) contain biodegradable
component, which results in the difference in engineering
property between MSWs and traditional soil. Landfilling will
remain the dominant disposal method for MSWs in China for
the foreseeable future. An understanding of engineering
characteristics of MSWs and landfill behavior is important for
the planning, design, and operation of landfills.
The MSWs in China contain much more putrescible organic
waste and higher initial moisture content than the MSWs
generated in developed countries (Chen et al. 2010a). In this
paper, engineering properties of MSWs with high organic
content are discussed, and a Bio-Hydro-Mechanical (BHM)
coupled model is proposed to estimate a series of coupled
phenomena in such landfills. Based on the simulation results,
geo-environmental problems associated with this kind of
landfills of MSWs were discussed. The work is valuable for the
development of bioreactor landfilling technologies in the Asian
developing country such as China.
2 ENGINEERING PROPERTIES OF MSW WITH HIGH
ORGANIC CONTENT
2.1
MSW composition
MSW typically consists of food and vegetable wastes, paper
products, plastics, textiles, wood, cinder, and soils. Table 1
shows a comparison of waste composition among China, India,
Korea, Singapore, UK, and USA as of 2000. The MSWs in
China and India contain much more putrescible organic wastes
(i.e., kitchen food and vegetable wastes which account for 40-
50%) than the MSWs generated in UK, and USA. The content
of mineral materials (i.e., cinder, dust, concrete, etc.) in China
and India is also higher than that in UK and USA. These
differences are likely attributable to the differences in cooking
styles and the living standard among the countries.
Table 1. Comparison of MSW composition among China, India, Korea,
Singapore, UK, and USA generated in 2000 (%) (Chen and Zhan 2007)
Country Food
Vegetable
Dust
Cinder Paper
Plasitc
Textile
Wood
Rubber
Metal
Glass Others
China
43.6
23.1
6.7
16.7
3.4
6.5
India
41.8
40.3
5.7
8.2
4.0
0
Korea
24.6
NA
25.8
NA
13.5
NA
Singapore 23.5
17.1
21.6
11.1
24.0
2.7
UK
20.0
12.0
34.0
21.0
15.0
0
USA
15.3
10.9
29.8
29.4
12.7
1.9
2.2
Initial moisture content and moisture retention
characteristic of the MSWs
For Chinese MSWs, more than 40% of the waste in wet weight
is occupied by moisture for most of the data reported, as
illustrated in Figure 1. At the rainy seasons, the initial moisture
content (wet/wet) of the waste may reach 70% in the humid
regions of southern China (Chen et al. 2010a). Compared with
Chinese wastes, the MSWs of developed countries commonly
have a lower initial moisture content (< 30%, Qian et al. 2002).
High content of organic component (see Table 1) is the main
factor that contributes to the high initial moisture content of
Chinese MSW.
According to the literatures, the field capacity of wastes is
generally assumed to be equivalent with the water content
