Abstract

Landfill leachates from municipal landfills are usually heavily contaminated and thus require treatments before direct discharge into natural waters. Selecting the appropriate technology for leachate treatment is still a major challenge for operations in municipal landfills. Biodegradation is effective for treating young leachates, whereas old leachates require processes such as chemical oxidation, coagulation–flocculation, chemical precipitation, ozonation, activated carbon adsorption, and reverse osmosis. Recently, the combination of biological pretreatments followed by physico-chemical processes has been shown to be very efficient. Here we review the efficiency of biological treatment in combination with reverse osmosis to clean landfill leachates. We studied in particular processes including a membrane bioreactor, activated sludge, a rotating biological contactor, and up-flow anaerobic sludge blanket treatments, followed by reverse osmosis. We found a 99–99.5% removal of the chemical oxygen demand (COD), and a 99–99.8% removal of N–NH4+ using reverse osmosis and activated sludge. Using reverse osmosis with a rotating biological contactor, we observed 99% removal of COD, biochemical oxygen demand and N–NH4+. The combination of reverse osmosis, activated sludge and rotating biological contactor removed 98–99.2% of Cl− and 99–99.7% of Pb. Total suspended solids are best removed, up to 99%, by either a combination of reverse osmosis with membrane bioreactor, or reverse osmosis with activated sludge.

Highlights

  • A major issue arising from solid waste landfilling is the generation of landfill leachates

  • Leachate produced in young landfills is characterized by the high BOD/chemical oxygen demand (COD) ratio, which is used as a measure of leachate biodegradability

  • The use of reverse osmosis as a second step of leachate treatment improves the efficiency of nitrogen compounds (N–NH4+, N–NO3−) removal Values of influent and effluent in mg/L except for pH and EC, removal effect in % RO reverse osmosis, MBR membrane bioreactor, TSS total suspended solids, EC electroconductivity, n.a. data not available of treated leachate from 7.4 to 0.02 mS giving over 99% removal effect

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Summary

Introduction

A major issue arising from solid waste landfilling is the generation of landfill leachates. With time leachate goes through the successive aerobic, acetogenic, methanogenic, and stabilization stages of organic waste degradation, in which its properties such as chemical oxygen demand, biological oxygen demand, BOD/COD ratio, ammonium nitrogen, and pH vary widely (Ahmed and Lan 2012; Kjeldsen et al 2002). These parameters have their typical ranges depending on leachate/landfill age, which is commonly classified into three stages: young (lower than 5 years), medium/intermediate (5–10 years), and old/stabilized (more than 10 years) (Table 1) (Kurniawan et al 2006; Alvarez-Vazquez et al 2004; Ahmed and Lan 2012; Foo and Hameed 2009). Ammonia nitrogen is present in leachate in young landfills owing to the deamination of amino acids during destruction of organic compounds

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