Water & Wastewater Treatment

WWT October 2018

Water & Wastewater Treatment Magazine

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Page 22 of 43

Getting to Grips with… landfi ll leachate Liquid that oozes from landfi lls can be among the most challenging of wastewaters to treat, but technology is now available that can deal with it in an energy-effi cient manner The Knowledge www.wwtonline.co.uk | WWT | OCTOBER 2018 | 23 BY MARK HARDIMAN, DIRECTOR, LAT WATER Q: What is landfi ll leachate and how is it created? A: Leachate is the liquid that is formed in landfi lls and drains or "leaches" to the bottom of the landfi ll. It is formed from the natural rotting and decomposition of the organic matter that is buried combined with water that enters the landfi ll together with dissolved material from other solid matter. It is always present in a landfi ll and gradually seeps to the bottom. Modern landfi lls are sealed at the bottom so the leachate has to be extracted to prevent it from saturating the landfi ll. The make-up varies depending on the composition of the landfi ll but comprises in general a mix of dissolved Q&A salts, organic compounds, frequently quite high levels of dissolved ammonia and various levels of metal ions. Basically anything that has been buried in the landfi ll can end up dissolving and being present in the leachate. The volume that is created varies depending on the size and age of the landfi ll but even a er the landfi ll is closed and sealed it remains biologically active, hence producing leachate that requires management for decades a er being sealed. Q: What particular treatment challenges does it present? A: Leachate is one of the most challenging contaminated liquids to treat. Treatment at the site creates problems for conventional water treatment methods as the volume

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