Iron reduction from closed landfill leachate

Abstract

Iron is usually present in landfill leachate in its soluble form (Fe2+ ions), Aging leachate
often contain hif+l+
levels of total iron, If an uncontrolled
3+
discharge enters oxygenated
surface water Fe ions will oxidise into its insoluble state Fe ions, or rust Resulting in
the depletion of oxygen and a detrimental impact on aquatic life.The poster discusses the
problems associated with iron in an aging landfill leachate and the issues that need to be
addressed in order to safely dispose of the leachate to surface water,
A successful case study of a leachate treatment plant in Mid Wales, UK, shows how the
problem was overcome at minimal cost to the Local Authority. The plant also had to be
capable of treating high ammonia levels, by converting ammonia to nitrate and reducing
the nitrate loading using a series of reed and gravel beds.Previous experience
demonstrated that soluble iron II ions infiltrate the pore spaces in gravel beds, before
oxidising and blocking the pores with (solid) iron III. It was therefore essential that the
majority of the iron was removed prior to the leachate entering the gravel beds.This was
achieved by constructing two aeration towers filled with a lightweight polypropylene
media, with a large surface area to volume ratio. Leachate was pumped through the
towers at a high flow rate, Fe
2+
<•v was rapidly oxidised to Fe3\s)
, the resulting iron III
deposits as a film on the media. Finer iron sediments precipitate out in two underground
storage tanks. With the majority of the iron removed the leachate could pass for further
treatment before being discharged under consent to surface water.