MOHAMAD ANUAR KAMARUDDIN, MOHD SUFFIAN YUSOFF, HAMIDI ABDUL AZIZ, and NUR KHAIRIYAH BASRI
Landfilling is the primary means of municipal solid waste disposal in many countries worldwide owing to its economic advantages and minimum technology being practiced. Contamination of surface and ground water through leachate; soil contamination through direct waste contact or leachate; air pollution through the burning of wastes and the uncontrolled release of methane by anaerobic decomposition of waste (Aziz et al. 2010) are some of the effects of landfilling activities. In addition, landfill leachate produced from landfill sites consists of contaminated pollutants that is very difficult to deal with (Umar et al. 2010). If not properly treated and safely disposed, leachate can migrate to soil and subsoils which might cause severe damage to eco-system of land and receiving water. Landfill
leachate contains pollutants that can be categorized into four groups [dissolved organic matter, inorganic macrocomponents, heavy metals, and xenobiotic organic compounds (Kjeldsen et al. 2002)] as consequence of the existing waste disposal practice. Organic content of leachate pollution is generally measured by chemical oxygen demand (COD) and biochemical oxygen demand (BOD5). Leachate is also rich in ammonia, halogenated hydrocarbons suspended solid, significant concentration of heavy metals and inorganic salts (Renou et al. 2008; Umar et al. 2010; Bashir et al. 2009; Aziz et al. 2010). According to Umar et al. (2010) for stabilized leachate, the COD content generally ranges between 5,000 and 20,000 mg/L. The BOD5/COD ratio provides a good estimate of the state of the leachate and this ration for young leachate is generally between 0.4 and 0.5 (Kurniawan et al. 2006). The presence of concentrated pollutants in leachate has become one of the major issues to the landfill operator in obeying strict regulations for the safe disposal of leachate. Normally, the existence of high levels of pollutants such as ammonia in landfill leachate over a long period of time leads to a motivated algal growth, decreased performance of biological treatment systems, accelerated eutrophication, promoted dissolved oxygen depletion, and increased toxicity of living organisms in water bodies (Aziz et al. 2010).