REMOVAL OF DISSOLVED METHANE AND OTHER CONTAMINANTS FROM LANDFILL LEACHATES IN ENGINEERED WETLANDS

Abstract

This paper will present detailed design and operational data for a full-scale horizontal flow reed bed system, specifically designed for removal of dissolved methane from leachates at a closed landfill in the UK Midlands, near to the city of Birmingham. Since commissioning during the summer of 2013, as reeds have grown, extensive operational data have demonstrated successful and complete removal of dissolved methane to below required concentrations, for safe disposal into the public sewer. The Shirley reed bed is very successful at removing high initial levels of dissolved methane (>95% removal), as per the intended requirements. This ensures that methane within the discharged effluent remains below the 0.14mg/l consent concentration. Removal of methane has been achieved consistently for over 5 years from summer 2014 despite occasional increases in leachate flow rates above the design capacity for the reed bed. Additional removal of further contaminants is achieved by the reedbed, where the successful removal of high levels of iron and suspended solids from the leachate is observed. Monitoring has also noted significant seasonal nitrification of ammoniacal-N, although this was not part of the original purpose of the bed. Design, operational and monitoring data are presented and discussed, with discussion of how various practical issues were overcome during the six years of operation. The technology has wide application for many closed landfill sites throughout the world, and design loading data have been derived that will be valuable for operators to size reed beds appropriately at their sites.