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Quality evaluation and improvement of mechanically–biologically treated municipal solid waste in view of a possible recovery
Di Lonardo, M. C.; Lombardi, F. & Gavasci, R.
Abstract
This study aimed to identify possibilities to
improve the quality of the stabilized biowaste coming from
the mechanical–biological treatment of municipal solid
waste produced in Rome for possible recovery rather than
landfilling. The waste sampled before and after the first and
the fourth week of aerobic biodegradation as well as different
particle size classes composing the biostabilized materials
were characterized in order to investigate the content and
distribution of contaminants. Results showed, firstly, that the
stabilized biowaste was not biologically stable after 4 weeks
of biostabilization process, presenting dynamic respiration
index >1,000 mg O2 kg VS-1 h-1. Heavy metal (Cd, Cr,
Cu, Ni, Pb, Zn) content fulfilled the requirements for utilization,
but by contrast, their release in water phase was quite
high and not complying with Italian regulatory limits for
waste recovery. In order to raise the quality, the biological
process management should be improved by increasing the
water amount to add to the rotting waste since the output
material had moisture (19.7 % WM) lower than the recommended
content for an optimized aerobic biodegradation
(>40 %). Furthermore, fractions having particle size higher
than 10 mm, composed of high content of impurities and
heavy metals, should be separated by obtaining a reduction in
chemical–physical contamination. Finer waste flow
(<10 mm) can be recovered in environmental remediation
activities, whereas coarser fractions (>10 mm) can be used in
waste-to-energy plants, given the great content of high calorific
value materials and the compliance with characteristics
defined for solid recovered fuels.
Keywords
Biological stability; Heavy metals; Mechanical–biological treatment; Municipal solid waste; Particle size distribution; Stabilized biowaste
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