The treatment of landfill leachates in on-site aerated lagoon plants: Experience in Britain and Ireland

Abstract

Landfill leachate has been shown to be treatable in prototype demonstrations on landfill sites, without either excessive costs being incurred, or the use of systems that require sophisticated management. A full-scale, automated leachate treatment plant has been operated since mid 1983 at the Bryn Posteg Landfill Site, operated by Montgomery District Council in mid-Wales. The plant was designed by Aspinwall and Co., and has provided high quality data on both technical and economic aspects over 3 years of operation. The leachate treatment plant is centred on a large aerated lagoon with a long (> 10 days) mean period of retention; control systems enable treatment to be accomplished in an almost-completely automatic manner with minimal attention from on-site staff. During the first 30 months continuous operation of the plant, including 2 summers and 3 winters, the BOD of leachate being treated exceeded 10,000 mg l −1 for extended periods (flow weighted mean value 3700 mg l −1). The effluent BOD has rarely exceeded 50 mg l −1 (fwm value 18 mg l −1). Better than 97% removal of COD has been maintained, together with excellent removal of ammonia, iron, manganese and zinc. Treatment costs are outlined and summarised. Two other similar leachate treatment plants are briefly described, one of which is treating large volumes of a methanogenic leachate, at an older landfill with more complex leachate management problems. Results demonstrate that such schemes are technically and economically viable at landfills wherever they are required.