Activated carbon columns
Granular activated carbon is defined as the activated carbon being retained on a 50-mesh sieve. Carbon can now be produced with a variety of materials, methods and degrees of activation to produce activated carbons designed to meet the demands of a wide array of applications. Intensive research into the use of activated carbons for water and wastewater treatment purposes has been made for decades. As leachates are normally very complex matrixes, their treatment using activated carbons is not as common as in other wastewater treatments.
Nevertheless, due to current stringent technical requirements regarding leachate composition, combined processes using activated carbon are being studied with more emphasis. The use of activated carbon as a single-step treatment is rarely found. However, studies have shown that the single-step treatment of recalcitrant leachates might be effective. Activated carbons are currently more often used as a pre-treatment, combined treatment or final unit treatment process for landfill leachates.
In pre-treatment processes, activated carbon is more commonly used to reduce the levels of COD and heavy metals with the objective of allowing for a final biological step. Its application for the reduction of high levels of ammoniacal nitrogen is also usual. Combined processes, such as the use of granular activated carbon in biological fluidised beds, moving-bed biofilms or activated sludge reactors have been applied with good results to reduce BOD, COD, heavy metals and ammoniacal nitrogen, to levels allowing direct discharge of leachate into natural watercourses. The use of activated carbon as a final treatment step is also commonly used to reduce to an acceptable level the concentrations of non-biodegradable organic and chlorinated organic compounds, as well as to treat the leachate colour.
It is currently considered in that many site-specific situations it is reasonable to consider activated carbon as a suitable adsorbent to reduce leachate discharge to acceptable levels where recalcitrant compounds in different kinds of leachate matrixes are present.