Heavy metals removal on leachate for use as fertilizers
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abstract
Municipal landfill leachates typically contain high ammonium and organic concentration which could
contribute to its use in agriculture, leading to the reduction of costs for the respective waste treatment
plants. However, due to the nature of the leachates, they may contain phytotoxic substances. The
landfillleachate samples differ by many factors such as the composition of the treated waste, elapsed
time, geochemical and weather conditions [1-3]. Taking into account these considerations, leachate
samples from a storage tank at the "Residuos do Nordeste, ElM" mechanical and biological treatment
plant, were collected in February 2019, and stored :at 4°C. The leachate samples were processed using
activated carbon adsorbents produced from the compost of the referred company, and H2S04 activated
clays obtained from a partnership with a Kazakhsta1n institution. The leachate samples were mixed with
the adsorbents for 48 hours, centrifugated and the supernatant was reserved. TOC analysis in a
Shimadzu TOC-L equipment and metals quantification by atomic absorption spectroscopy using a
Varian SpectrAA 220 apparatus were carried out. :Selected results are presented in Fig. 1. The original leachate presents an organic carbon content closer to the requirements of the EU
legislation for liquid organo-mineral fertilizers. The activated carbon promoted greater TOC removal in
comparison with the activated clays. Both materials showed interaction with the heavy metals.
However, Cr still remains present in higher conten1ts and K presents lower values than the legislation
requirements. Overall, the activated carbons presented a greater potential for heavy metals removal.
However, ion-exchange resins will be tested for a more efficient heavy metals removal to minimize
possible secondary elimination of components sue:h as nutrients and organic carbon.
This work was financially supported by: Project VALORCOMP, funded by FEDER through Programme INTERREG V-A Spain- Portugal {POCTEP) 2014-2020 and Associate Laboratory LSRE-LCM UID/EQU/50020/2019 - funded by national funds through FCT/MCTES {PIDDAC).
