The starting point in any discussion about UK/ EU leachate management techniques is to begin by stating the overriding rule upon which all landfills are operated, in compliance with the EU Landfill Directive.
That is that as far as practicable, the waste will be kept dry and all leachate generation will be minimised by doing this. So the uncovered areas of open landfilling cells are kept as small as possible, and capped as soon as practicable with low permeability materials.
Nevertheless, despite such measures, most landfills do still generate leachate, and the first and most obvious action, when leachate starts to appear, is to recirculate it by pumping it back on to the surface of the waste.
The aim that this leachate will soak into the wastes and not reappear. Certainly, this will be possible for a period of time, under most circumstances and the leachate that does re-appear is consistently, after passing through an anaerobic, methane producing landfill, of lower BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand). In other words it hasto bee a large extent anaerobically digested.
Other leachate management techniques which do not strictly comprise “treatment”, have been utilised by landfill owners and operators , such as:-
- Leachate irrigation on to nearby land or the restored landfill surface: to achieve volume loss by evaporation. This may work in arid climates overseas, and during UK dry summer weather. But leachate evaporation is not much use during the average UK winter, nor in poor UK summers!
- Dilution of leachate with surface water from the site, to bring contaminant concentrations below watercourse and sewer discharge consent levels and by so doing allow themselves the use of these disposal routes. This is not normally justifiable in the UK against sustainability criteria, and will now also be likely fail to comply with the principles of BAT (Best Available Technique) under Environmental Permitting controls (compliance with the IPPC Regulations);
- Leachate “pre-conditioning” which is our term for the chemical/physical modification of problematic contaminants in sewage. Such “pre-conditioning” might for example comprise the addition of hydrogen peroxide, or potassium permanganate to an odorous leachate to reduce smells, or the common use of Methane Stripping. Methane Stripping uses air and mixing, to dissipate dissolved methane to the atmosphere from leachate.
Other common practices include the continued acceptability of tankerage of leachate to sewage works licensed to accept industrial effluent, where there is not comprehensive treatment at the receiving sewage works, and also discharge to public sewers if these similarly lack sufficiently the facilities to treat all the major contaminants of leachate, rather than just diluting it.