Canadian Journal on Environmental, Construction and Civil Engineering Vol. 2, No. 5, June 2011 118 Organic Contaminant Destruction from Landfill Leachate by Optimizing Fenton Treatment Process Kashif Mahmud, Sarder M. Yahya, Ehteshamul H. Navid and Sayed M. Hossain Abstract — This research was undertaken to investigate various operating conditions of Fenton treatment process for minimizing the sludge production and maximizing COD as well as colour removal from landfill leachate. Sample was collected from Matuail landfill site, one of the major landfill sites of Dhaka City Corporation. For optimum pH value of 5 and optimum dosages of Fenton reagents having H 2 O 2 /Fe 2+ molar ratio of 1.3 the highest removal of COD and colour were found 68% and 87% respectively with massive sludge production of 75%. The COD and colour removal efficiencies with a three-step dosing of reagents were 11% and 7% higher respectively with 17% less sludge production than those with single dosing of individual Fenton treatment process. Also recycling of Fenton sludge enhanced COD removal efficiency by 6% having similar colour removal efficiency and reduced sludge production significantly by 38%. With all optimum parameters, the highest removal of COD and colour were found 84% and 93% respectively with sludge production of 30% through multiple dosing of Fenton reagents with sludge recirculation. Conversely pretreatment with extended aeration before Fenton process provided the achievement of 89% COD and 97% colour removals having less sludge volume reduction. Key Words — biological treatment, chemical treatment, coagulation, extended aeration, Fenton reagent, leachate. I. INTRODUCTION Surface water that percolates through the landfill and leaches out organic and inorganic constituents from the solid waste is termed as leachate. Landfill leachate production starts at the early stages of the landfill and continues several decades even after landfill closure. Landfill leachate is mainly generated by the infiltrating water which passes through the solid waste fill and facilitates transfer of contaminants from solid phase to liquid phase. Leachate usually varies widely in composition depending on the landfill age, the quality and quantity of solid waste, the biological and chemical processes, the amount of precipitation and percolation. It can contain both dissolved and suspended material. Landfill receives a mixture of municipal, commercial and mixed industrial waste but excludes significant amounts of concentrated specific chemical waste. Landfill leachate may be characterized as a liquid having four groups of contaminants such as dissolved organic matter, inorganic macro components, heavy metals and xenobiotic organic. Due to the inhomogeneous nature of the waste and because of the different compaction densities that will be encountered, water will be able to percolate through and appear as leachate at the base of the site [1]. The physical appearance of leachate when it emerges from a typical landfill site is yellow or blackish coloured and the smell is acidic and offensive. Leachate concentrations may exceed permissible levels over a long period of time. So leachate is one of the most important issues in the management of a landfill. If no remedial measures are taken to prevent continual inputs of water to the wastes, this could pose adverse environmental impacts. Landfill leachate is high strength wastewater which contains high concentrations of organic matter and ammonium nitrogen. There is a fluctuation in the composition of organic, inorganic and heavy metal components in the leachate making them more difficult to be dealt with. When the leachate containing high strength organic matter and ammonia is discharged without treatment, it can stimulate algae growth through nutrient enrichment, deplete dissolved oxygen, and cause toxic effects in the surrounding water environment. Landfill design and operation have a major impact and influence on the leachate generation. This leachate varies from landfill to landfill and over time and space. It fluctuates over short and long-term periods due to climatic, hydrogeology and waste composition variations [2]. Generally, leachate contaminants are measured in terms of chemical oxygen demand (COD) and biological oxygen demand (BOD). In addition, leachate usually contains high concentrations of inorganic salts: mainly sodium chloride, carbonate and sulfate and is dependent on the waste composition landfilled. Landfill leachate is generated from sanitary landfill and contains various contaminants, making the treatment of leachate difficult. Leachate treatment has inevitably become a much more widespread requirement at landfills. The main environmental problem experienced at landfills has resulted from a loss of leachate from the site and the subsequent contamination of surrounding land and water. Improvements in landfill engineering has been aimed at reducing leachate production, collecting and treating leachate prior to discharge and thereby limiting leachate infiltration to the surrounding soil [3]. However a need exists to develop reliable, sustainable options to effectively manage leachate generation and treatment. In designing a leachate treatment scheme, the process must reflect the possibility that treatment techniques which work well for a young leachate may become wholly inadequate as the landfill age increases [4]. There are difficulties concerned with the treatment of leachate due to the variability and strength of leachate. Selection of a leachate treatment method is generally based on the characteristic of organic matter in leachate, generally expressed as the ratio of