Evaluation of landfill leachate in arid climate—a case study

https://doi.org/10.1016/S0160-4120(03)00018-7Get rights and content

Abstract

Generation of leachate from municipal solid waste (MSW) landfill in arid regions has long been neglected on the assumption that minimal leachate could be formed in the absence of precipitation. Therefore, a case study was conducted at two unlined MSW landfills, of different ages, in the state of Kuwait in order to determine the chemical characteristics of leachate and examine the mechanism of leachate formation. Leachate quality data were collected from both active and old (closed) landfills where co-disposal of MSW and other solid and liquid wastes is practiced. The analysis of data confirms that leachates from both landfills are severely contaminated with organics, salts and heavy metals. However, the organic strength of the leachate collected from the old landfill was reduced due to waste decomposition and continuous gas flaring. A significant degree of variability was encountered and factors which may influence leachate quality were identified and discussed. A water balance at the landfill site was assessed and a conceptual model was presented which accounts for leachate generation due to rising water table, capillary water and moisture content of the waste.

Introduction

The State of Kuwait lies at the northeast edge of the Arabian Peninsula at the head of the Arabian Gulf. It is an arid country with no “fresh” surface water and very limited resources of useable groundwater. The rapid urban and industrial development of Kuwait in recent years has created complex environmental problems that pose serious health hazards. The country generates large quantities of municipal solid waste (MSW) and its per capita solid waste generation rate is (among the highest) in the world (Hamoda and Al-Yaqout, 2001).

Sanitary landfilling is still the primary method of disposal of MSW in Kuwait. A large quantity of leachate is produced despite the arid climate due to the co-disposal of liquid and sludge waste with MSW. Leachate, that is generated by landfills, is likely to contain various types of pollutants that may enter the groundwater aquifers in the surrounding areas. The leachate takes up organic and inorganic constituents by means of physical, hydrolytic and fermentative processes Chian and DeWalle, 1976, Barlaz, 1989, thus, it contains a high concentration of organic matter and inorganic ions, including heavy metals. The generation and chemical characteristics of leachate in arid climate countries such as Kuwait, depends upon the MSW characteristics, moisture content, capillary action, water content of subsurface soil and ambient temperature which is usually in the range of 20–50 °C. The annual average rainfall in Kuwait is 110 mm, which is not a significant factor. Calculated values of climate water balance (w) based on the precipitation and Pan-evaporation data for the past 15 years were always negative even in the wettest seasons (Al-Yaqout and Townsend, 2001).

The chemical composition of leachate depends on many factors such as the initial composition of solid wastes, the particle size, the degree of compaction, the hydrology of the site, the climate, and finally the age of tip. The latter factor reflects the degree of stabilization of the wastes (Kouzeli-Katsiri et al., 1999). Surface conditions which may affect leachate generation in some regions, as is the case of Kuwait, include vegetation (mainly bush-like) cover material like local sand gatch, and its properties such as density, permeability, moisture content, surface topography, sand dunes, and impact of dry wind conditions and humidity in summer months. The effect of a rising water table in Kuwait cannot be neglected. Rising water table alone can be a major factor for producing large quantities of leachate in an arid climate. The disposal of liquid waste and solid waste with high water content in all the landfill sites in Kuwait produces more leachate with complex chemical characteristics. A conservative estimate shows that the share of liquid waste and sludge waste component of MSW is 42% (volume/volume basis), with 2 million tons disposed in four active landfills (Mina Abdullah, Al-Sulaybiya, Jahra and North Ring Road) during 8 years from 1993 to 2000. For example, annual quantities of liquid waste and sludge waste disposed at Al-Sulaybiya landfill from 1993 to 2000 are presented in Fig. 1.

The estimation of volume of leachate and the concentration profiles of the main contaminants is of particular importance for the proper design and operation of sanitary landfills. Such information will permit the manager of the site to correctly plan the facilities required for the collection and treatment of leachates, including recirculation of leachates back to landfill (Kouzeli-Katsiri et al., 1999).

Each of the above leachate generation factors can be measured with varying degree of accuracy and inserted into a new water balance equation for arid climate landfills (closed or active) which will account for the total liquid inputs and total liquid outputs from the landfill. This paper presents experimental data and a conceptual model that will shed light on various aspects of arid climate leachate such as its formation, chemical characteristics, hydrology and effect of seasonal variation on leachate characteristics.

Section snippets

Background

The current disposal practices of MSW in Kuwait are not safe for humans and the environment. The landfill site receives all kinds of wastes such as food wastes, oil products, debris, agricultural wastes, chemical materials, hospital waste, slaughterhouse waste and liquid wastes. The monthly waste composition and its disposal in the year 2000 at Al-Sulaybiya landfill site are presented in Table 1. There is no segregation of waste at the source and no specific landfill for each type of waste.

Monitoring boreholes

A truck-mounted rig was used to drill and install the monitoring boreholes. A 200 mm diameter casing was used to drill the wells and then install 100 mm diameter PVC pipe. The pipes extended to a depth of 6–23 m below the ground surface in the landfill site. The bottom of the pipe was capped with a PVC screen of fine mesh to sieve the incoming leachate and trap large objects as to prevent clogging. A sand filter was placed around the screened portion of the pipe. After the casing was driven to

Chemical analysis of leachate

Considerable variations in the quality of leachates produced from different landfills have been reported in the literature Johansen and Carlson, 1976, Chian, 1977, Booker and Ham, 1982, Kouzeli-Katsiri et al., 1993, Robinson, 1993, Gettinby et al., 1996. The results obtained in this study are shown in Table 2(a), Table 2(b) and Table 3(a), Table 3(b) for Al-Sulaybiya and Al-Qurain landfills, respectively.

Active landfill

Table 2(a), Table 2(b) present average monthly data for three periods, each of four months,

Conclusion

The landfill waste in Kuwait comes from many sources and include hazardous materials. Generally, it is expected that no leachate will be generated in arid climate landfills, but it was found in this study that considerable quantities of leachate are formed at landfill sites. The primary causes of leachate production despite the negative water balance are the improper disposal of liquid and sludge wastes as well as the rising of the groundwater table. A modified water balance model was developed

Acknowledgements

This study was partially supported by a research grant from Kuwait University through project EV 04/00. The authors wish to express their gratitude to Engineer Mohammed Zafar for his assistance in computer analysis.

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