CHAPTER ONE INTRODUCTION 1.1 Background of study Environment, whether physical, biological or chemical, is composed of discrete components that are either biotic or abiotic, and are extremely related and dependent on each other for optimal functioning. Therefore, any interference with the natural state of these components, especially to an extreme condition, often leads to ecosystem disruption, ecological imbalance/stress and even global deterioration. Such interferences most often stem from the quest to satisfy one need or the other at the expense of another, without due caution on the potential consequences. However, such consequences when they occur have ways of attaining solutions, executing corrections and potentially itching for reclamations. Most environmental consequences arise from the phenomenon known as “Pollution”, which is the occurrence of contaminants within a pre-existing natural environment with the aftermath effect of initiating adverse change. And considering the three basic domains of the earth; air, water and soil, pollution have been an age long concern. Regardless of the source of contaminants or point of contamination, pollution whether it is air, water or soil, can be borderless; hence the reason for the associated global impacts. In fact, air, water and soil pollutions in forms of particulate matter emissions, sea oil spills and polychlorinated biphenyls-impacted soil, respectively abound. These do occur to the magnitude that questions have been asked- ‘what/who is the cause?” Definitely, the answer is humans- the embodiment of the biological part of the ecosystem that is saddled with the utmost responsibility of resource utilization and management. The wants of humans are insatiable and with rapid growth in population, 1 increase in demands and supply become inevitable. Changing lifestyle, globalization, infrastructural developments, renewed income earning trends and some other socio- cultural/economic inclinations have driven a different wave of anthropogenic activities against the backdrop of what is obtainable in the past, especially before the “March to civilization” era. Such wave of anthropogenic activities do not only help to attain economic empowerments and societal developments but have as well become the bane of most environmental pressure of which pollution is part of it. However, among the various aspects of anthropogenic activities that cause problems to our immediate environment, waste generated is of significant interest. Environmental pressures from the generation and management of waste include but not limited to emissions to air (including greenhouse gases), water and soil, all with potential impacts on human health and nature (Fauziah et al., 2013; Emenike et al., 2012a). A number of waste management options are being used in the contemporary era to ensure disposal and treatment of waste, among which includes, composting, incineration, land/seafilling, and recycling. Whereas the developed economies of the world adopt more advanced, cleaner and sustainable principles towards waste minimization and handling, the developing societies are yet to embrace nascent technologies pivotal to managing waste in a manner that has less/or zero negative impact on the immediate environment. Landfilling of waste is one of such management options that involve less technology and energy dissipation in comparison to other systems that are more expensive, time consuming and high-tech oriented. Yet, the issue is whether there is any negative side to landfilling? 2 Therefore, landfilling remains the dominant waste disposal method in most Asian and developing countries. About 75% of the municipal waste generated in Malaysia is landfilled and this has significant pressure on the environment, as only 5% is recycled, while the rest are either burned or dumped into rivers or at illegal sites (Agamuthu et al., 2009). All landfills produce leachate which is liquid produced by the action of “leaching” when rain water percolates through any permeable material. As such, streams and other forms of water bodies are contaminated with leachate due to the vertical and lateral migration of leachate (Jaffar et al., 2009), if there are no geomembrane liners. Groundwater and other forms of water course are precious part of the ecosystem and in order to prevent or minimize the possibility of water pollution, the degree of planning, engineering, waste stream control and management undertaken at municipal waste landfills has increased dramatically in recent years. The potential and degree of risk posed to groundwater, soil and even aquatic life by landfill leachate is extremely difficult to assess (Emenike et al., 2012a). Leachate composition varies based on the materials present in landfill, i.e. dissolved organic matters (alcohols, acids, aldehydes, and short chain sugars), inorganic macro components (common cations and anions including sulphate, chloride, and ammonium), heavy metals (Pb, Ni, Cu, Hg), xenobiotic organics and polychlorinated biphenyls (PCBs) (Ludwig et al., 2003; Christensen et al., 2001). Therefore, the need for a critical study of the composition of ‘modern’ municipal waste landfill leachate had been evaluated (Murray & Beck, 1990). The study opined that leachates may contain toxic and hazardous compounds, hence there is need to properly evaluate leachates from municipal waste landfills. Such investigation is absolutely necessary as landfilling is the predominant method of 3 municipal waste disposal in most industrialized countries (Carra & Cossu, 1990) and developing nations as well. Due to the composition of wastes, during storage or disposal of municipal solid waste (MSW), wastewater is separated and is polluted by organic materials, heavy metals, and other toxic substances. The amount of leachate depends on the initial water content of the MSW, and the storage or disposal conditions such as temperature, humidity, and ventilation (Selic et al., 2007). Leachate is the potentially polluting liquor that accumulates beneath a landfill site resulting from the infiltration and percolation of rainfall, groundwater, runoff, or flood water into and through an existing or abandoned solid waste landfill site. Landfill leachate is characterized by high levels of salts and NHx-N, as well as, high organic concentration. Higher organic loading yields greater substrate availability for planktonic and epiphytic bacteria, and may induce inhibitory effect on sedimentary bacteria (Wendong et al., 2007). More than 200 organic compounds have been identified in municipal landfill leachate (Schwarzbauer et al, 2002), with about or more than 35 compounds having the potential to cause harm to the environment and human health (Paxeus, 2000). High level of ammonia is present in many older landfills, and is toxic to many living organisms in surface water and contributes to eutrophication, and dissolved oxygen depletion (Bae et al., 1997). In terms of solid waste management, Malaysia is characterized with many uncontrolled landfills without appropriate bottom liners and leachate collection systems, and there are about 291 landfills of different sizes and ages recognized officially with an estimated 4 three times more illegal dumps (Emenike et al., 2012; Fauziah & Agamuthu, 2010). At the exception of a few, most of the landfills are devoid of sanitary status as they are characterized of none or inadequate leachate collection and/or treatment facilities and also lack infrastructure to exploit landfill gas (Fauziah & Agamuthu, 2010). Toxicological evaluations of the landfill leachate are in great demand, to ensure safe discharge of leachate from landfills. Now, it has gradually begun to be incorporated into the environmental legislations in some countries (Eun-ah et al., 2009). Chemical oxidation has been developed as a method for the early-stabilization of landfills. However, by-products that are difficult to detect by chemical analysis can be compensated by toxicological evaluation. Therefore, toxicity tests have become useful tools for detecting the changes of leachate quality to complement the chemical oxidation method (Eun-ah et al., 2009). Both mortality and behavioural effect of landfill leachate on Cyprinus caprio had been evaluated (Jaffar et al., 2009). Toxicity of municipal dump leachate was tested on zebra fish (Brachydanio rerio) (Sisinno et al., 2000), while different concentrations of leachate were utilized to analyze the survival ability of tilapia (Sarotherodon mossambicus) (Wong, 1989). Another study had used larve and adult of Japanese Medaka (Oryzias latipes) to test the toxic potency of landfill leachate (Osaki et al, 2006). However, the absence of landfill toxicity data on a number of fresh water local fishes is a subject of concern due to their dominance and high economic value in the tropical and some temperate countries (Emenike et al., 2012a). More so, some of the toxicants associated with leachate have the potential of building up within the living systems in form of bioaccumulation. 5 In as much as, acute mortality and chronic conditions are vivid impacts of most effluents on the aquatic life, yet some other effects might be initiated without any observable changes. One of such effects is bioaccumulation. A number of toxicants are built up in living systems as a result of exposure. Therefore, bioaccumulation tests are used as a means of assessing and evaluating the potential build up of these toxicants within a given species with the view of extrapolating the tendency of absorption by another level