Leachate characterization in semi-aerobic and anaerobic sanitary landfills: A comparative study
Introduction
Solid waste disposal methods include open dump, sanitary landfill, incineration, composting, grinding and discharge to sewer, compaction, hog feeding, milling, dumping, reduction, and anaerobic digestion. Sanitary landfill is the most common municipal solid waste (MSW) disposal method due to such advantages as simple disposal procedure, low cost, and landscape-restoring effect on holes from mineral workings (Bashir et al., 2010a, Davis and Cornwell, 2008). However, the production of highly contaminated leachate is a major drawback of this method (Wiszniowski et al., 2007, Kurniawan et al., 2006).
Leachate is liquid formed primarily by the percolation of precipitation water through an open landfill or through the cap of a completed site. Leachates may contain large amounts of organic contaminants measured as chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammonia, halogenated hydrocarbons suspended solid, significant concentration of heavy metals, and inorganic salts (Foul et al., 2009, Aziz et al., 2009, Renou et al., 2008, Uygur and Kargi, 2004). It is also rich in phenol, nitrogen, and phosphorus. If not treated and safely disposed, landfill leachate could be a potential source of surface and ground water contamination, as it could seep into soils and subsoils, causing severe pollution to receiving waters (Oman and Junestedt, 2008, Lin et al., 2008, Sanphoti et al., 2006, Tatsi et al., 2003). Generally, the risks of the leachate on the natural environment are determined by comparing leachate quality with Malaysia standards.
Presently, there are over 230 landfills in Malaysia, mostly old dumpsites. Most are simply dumping grounds without any environmental protection. The resulting leachate is discharged directly into water courses without any treatment, which can threaten the surrounding ecosystem, particularly in cases where landfills are located upstream of water intakes. This study focuses on characterizing landfill leachate generated from anaerobic and semi-aerobic landfill.
According to Yamamoto (2002) and Matsufuji et al. (1993), in an anaerobic landfill, solid wastes are dumped in an excavated area of a plane field, which is filled with water in an anaerobic condition. Typically, anaerobic sanitary landfills are recognized by its sandwich-shaped cover. On the other hand, semi-aerobic landfills have a leachate collection duct. The opening of the duct is surrounded by air, and the duct is covered with small crushed stones. Moisture content in solid waste is small, and oxygen is supplied to the solid waste from the leachate collection duct. The schematic diagram of anaerobic and semi-aerobic (Fukuoka method) landfills is demonstrated in Fig. 1 (JICA, 2005).
A comparison of leachate characteristics at semi-aerobic and anaerobic sanitary landfills in a tropical country such as Malaysia is not available in the literature. This study reviews, analyzes, and compares the results of leachate compositions in two landfills in the northern region, namely, the semi-aerobic Pulau Burung sanitary landfill (PBLS) (unaerated pond and intermittently aerated pond) and the anaerobic Kulim sanitary landfill. Twenty parameters were considered in the present study. The obtained results were compared with data published by previous researchers and the Malaysia Environmental Quality Act 1974 (MDC Sdn. Bhd., 1997). The results are essentially required in order to propose an adequate technique for treating the studied landfill leachate that considers all the measured pollutants.
Section snippets
Site characteristics
PBLS is situated within the Byram Forest Reserve at 5°24′ N Latitude, 100° 24′ E Longitude in Penang, Malaysia, approximately 20 km southeast of Penang Island (Aghamohammadi et al., 2007). The total landfill site area is 63.4 ha, but only 33 ha is currently operational in receiving 2200 ton of solid waste daily. The depth of solid waste is between 10 and 30 m. This site was developed as a semi-aerobic sanitary landfill Level II by establishing a controlled tipping technique in 1991(landfill age
Result and discussion
Table 2 shows the characterization of leachate and the range and average values for the mentioned parameters at each leachate pond at the semi-aerobic PBLS (unaerated and intermittently aerated) and the anaerobic Kulim landfill.
Conclusions
Twenty parameters of landfill leachate were investigated in this study for two different landfill sites in the northern part of Malaysia to compare semi-aerobic and anaerobic landfill leachate quality. The results are necessary to formulate a suitable technique for treatment. In this study, aeration has a significant effect on reducing the concentration of several contaminants in PBLS leachate. Therefore, the concentration of these contaminants from leachate collected from the intermittently
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