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Landfill leachate is the liquid that percolates through the solid wastes in the landfill and leaches or draws chemicals or constituents from the waste. It contains high concentrations of organics, inorganics, ammonia-nitrogen, heavy metals and xenobiotic organic compounds (Kjeldsen et al., 2002). The chemical composition of landfill leachate depends on waste composition, climatic conditions, degradation rate of solid waste and the age of the landfill (Stefanakis, Tsihrintzis, & Constructed, 2014). Landfill leachate poses serious threat to surface and ground water. Common leachate treatment technologies include leachate recirculation, treatment in municipal wastewater plant, biological, and physico-chemical processes. Due to regulations continuously becoming stricter on discharge limits and standards and the ageing of landfill sites with more and stabilized leachates, conventional treatments are not sufficient to reach the level of treatment needed. In addition, operational challenges pose serious threat due to variable loads and flows during drought and seasonal precipitation, elevated temperatures (75- 115 F) and presence of numerous inhibitory compounds poses serious threat to the performance of conventional treatment processes. In recent years, more effective treatments based on pressure-driven membrane technology, such as nanofiltration (NF) and reverse osmosis (RO), have emerged as a viable treatment alternative. RO has been most widely used due to its ability to retain both organic and inorganic contaminants dissolved in the leachates with high efficiency. Despite this high efficiency, membrane fouling and disposal of large volumes of concentrate streams generated from pressure-driven membrane processes are regarded as the two main draw backs of treating landfill leachate using membrane-based processes. Membrane fouling results in short membrane lifetime, decreases process productivity, and requires extensive membrane pretreatment or chemical cleaning, while generation of large volume of concentrate requires further treatment or costly disposal of the leachate. 

The objective of this research was to investigate alternative technologies for landfill leachate management. Municipal landfill leachate discharge poses significant threat to landfill operators as leachate characteristics vary dramatically over time. Surplus leachate is frequently discharged to municipal wastewater treatment facilities because of cost and complexity of onsite treatment. Due to high nutrient loading, interference with UV disinfection or capacity challenges, municipal wastewater treatment plants have stopped accepting leachate. Therefore, more effective treatment method (i.e., membrane-based technologies) were investigated for better management practices. This study systematically investigated integrated membrane systems that utilizes a forward osmosis (FO) process and a membrane distillation (MD) process compared to a more conventional RO reconcentration process. FO operates on a gradient of osmotic pressure. This osmotic pressure gradient drives fresh water to diffuse across a selectively permeable membrane from a feed solution of relatively low ionic concentration (landfill leachate) into a solution with a higher concentration of ions. Because of the absence of pressure, in FO, membrane fouling is usually much lower than in pressure driven systems such microfiltration or RO. MD is a thermally driven water treatment process. A hot feed solution is separated from a cold distillate solution by a hydrophobic microporous membrane and, in the case of air gap MD (AGMD), a stagnant air gap is maintained between the membrane and the condenser channel by using a condenser foil which functions as a thermal insulation layer. A vapor pressure gradient exists across this membrane, the hot solution having a higher vapor pressure than the cold solution. This vapor pressure gradient drives transfer of water vapor across the hydrophobic membrane ii 

into the cold distillate solution. As this process is driven by thermal gradient, it is especially suited when low grade “waste” heat is available. In this study, the operating conditions were optimized for treatment of landfill leachate. Rejection performances of organic carbon (TOC), specific conductivity (μS/cm), ammonium nitrogen and volatile organics were investigated in the integrated systems.