Assessment of metallic mobile fraction bioavailable from different sewage sludge samples using leaching test

Analysis of metallic mobile fraction from sewage sludge wastewater treatment plants provides
very useful information about the possibility of metallic mobile forms to migrate on the
environment. Therefore, determination of total metallic mobile fraction, refers not only to
exchange fraction but also to bonded metals in sewage sludge structure which can usually be
removed with strong extractants. Together with leaching test are provided informations about
the bioavailability of toxic metals in normal environmental conditions. In this condition, for
assessing the risk of pollution induced by metals it is necessary to evaluate both, total and
mobile content available for environment. In this paper a leached extraction method according
to SR EN ISO 12457:2003 standard, that uses an extraction procedure (sludge-solution 1 -1 0
(m/v), 24 h, 40 rpm) was applied. As, Cd, Co, Cr, Cu, Mo, Ni, Pb, Se and Zn were detected in
extractible solution by ICP-EOS technique. The metals detected after leaching test were
compared with the values imposed by the current legislation and function of the results
obtained was indicated the possibility to storage the sludge as a non-hazardous waste or the
opportunity to use it as a fertilizer in agriculture.