Research Needs in Leachate Treatment for Remediation of Aquatic Environment
In recent years, our society has been dealing with one of the most serious challenges in maintaining good quality of water supply. Due to the seepage of landfill leachate (Figure 1), the groundwater in several areas that are close to open dumps have been seriously polluted, causing environmental degradation (Kurniawan et al., 2006a). To overcome this environmental problem, various treatments have been undertaken to treat this contaminated wastewater. Several types of individual and/or combined physico-chemical techniques, biological treatments, and advanced oxidation processes (AOP) have been explored for this purpose in laboratory scale and on-site (Kurniawan et al., 2006b; 2006c; Kurniawan, 2008).
Figure 1. Generation of landfill leachate from solid waste decomposition
Although the individual and/or integrated treatments have improved the treatability and biodegradability of the leachate, it is evident that neither type of treatment employed is universally applicable and/or highly effective in removing a high strength of recalcitrant compounds and NH 3-N from the leachate. The treated effluents were still unable to comply with the requirements of the maximum discharge limits strictly imposed by local environmental legislation (COD: less than 200 mg/L; NH 3-N: lower than 5 mg/L). Since current treatment options are still unable to maximize the removal of target contaminants in landfill leachate, there is a growing need to develop other cost-effective and environmentally sound technologies to enhance their treatment performance (Kurniawan, 2008).
The diverse applications of nanotechnology across a number of multidisciplines in recent years have stimulated environmental researchers to address the need for an efficient and effective treatment for landfill leachate. In spite of its unproven track record in environmental applications so far, researchers have found that nanotechnology could play a key role in pollution control strategies (Rassaei et al., 2007). They further argued that groundbreaking research in the field of nanoscience and engineering in recent years has provided various approaches and opportunities to synthesize and develop state-of-the-art, cost-effective and environmentally benign nanomaterials (Figure 2) for facilitating environmental remediation.
Figure 2. Potential nanoparticles for environmental remediation
Nanoparticles are a fascinating form of substances with behavior lying between that of individual atoms and molecules and the bulky state (Rassaei et al., 2008a). Due to their large surface area and high reactivity, nanoparticles with sizes ranging from 1 to 100 nm have the potential to be applied in wastewater treatment to remove refractory compounds from landfill leachate. For this reason, integrating nanosized materials with different functionalities into a composite material is of great interest to environmental researchers worldwide. This material is able to integrate one or more individual components to exhibit the best properties of each component.
Promoting nanomaterials as adsorbents presents opportunities to develop local solutions for tackling global water pollution. When being applied in tandem with engineering approaches, nanomaterials may address a variety of the world's most pressing problems in the areas of water, energy, health, agriculture, and biodiversity (WEHAB). During the 2002 UN Summit on Sustainable Development in Johannesburg (South Africa), these five priority areas were identified to be able to facilitate us to attain the UN Millenium Development Goals.
In recent years, research on nanoparticles has been pursued extensively due to their interesting fundamental properties and diverse applications. Cutting-edge research is being undertaken to synthesize and develop cost-effective and environmentally benign nanomaterials for environmental remediation (Rassaei et al., 2008b). It is anticipated that the applications of this nanoparticle for leachate treatment have revolutionized the ways in dealing with global water pollution in sustainable ways (Figure 3). Wastewater operators may shift their paradigm in treating contaminated wastewater using less costly, renewable and environmentally benign manufactured products, while improving resource efficiency. As nano-adsorbents have facilitated an effective removal of target pollutants from contaminated water, it is expected that they may no longer employ physico-chemical treatments that cost almost a half of total treatment cost.
Figure 3. Diverse applications of nanotechnology in today's life
Further reading
Kurniawan, T.A., Lo, W.H. Lo, Chan, GYS. (2006a). Radicals-catalyzed oxidation for degradation of recalcitrant compounds from landfill leachate. Chemical Engineering Journal 125(1): 35-57.
Kurniawan, T.A., Lo, W.H. Lo, Chan, GYS. (2006b). Physico-chemical treatments for removal of recalcitrant contaminants from landfill leachate. Journal of Hazardous Material 129(1-3): 80-100.
Kurniawan, T.A., Lo, W.H. Lo, Chan, GYS. (2006c) Degradation of recalcitrant compounds from stabilized landfill leachate using a combination of ozone- GAC adsorption treatment. Journal of Hazardous Material 137(1): 443- 455.
Kurniawan, T.A. (2008). Removal of Recalcitrant Contaminants from Stabilized Landfill Leachate by a Combination of Advanced Oxidation Processes ( AOP) and Granular Activated Carbon (GAC) Adsorption. PhD Dissertation, The Hong Kong Polytechnic University, Hong Kong.
Rassaei, L., Sillanpää, M., Bonné M. and Marken, F., Carbon Nanofiber – Polystyrene Composite Electrodes for Electroanalytical Processes, Electroanalysis, 19 (2007) 1461-1466.
Rassaei, L., Sillanpää, M. and Marken, F., Carbon Nanoparticle – Chitosan Thin Film Electrodes: Physisorption versus Chemisorption, Electrochim. Acta, 53 (2008a) 5732-5738.
Rassaei, L., Bonné, M., Sillanpää, M. and Marken F., Binding Site Control in a Layer- by-Layer Deposited Chitosan-Carbon Nanoparticle Film Electrode, New J. Chem., 32 (2008b) 1253-1258.
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