Summary:
The use of mineral-based materials is an emerging new application in the
treatment of sewage sludge with the aim of fulfilling the quality requirements
for heavy metals, organic compounds and pathogens. In this way, sewage sludge
from municipal waste water treatment plants can be beneficially reused
providing a long-term sustainable waste management solution. The treatment
technology has to be effective and affordable.
This MSc Thesis presents a laboratory scale application of attapulgitic clay
for treatment of sewage sludge from the municipal wastewater treatment plant of
Kamari, Thera. The study objectives were to assess the effectiveness of two
attapulgitic clay samples with different grain size distribution, mixed in two
different proportions with the sludge material. Geochemical parameters were
thoroughly studied before and after treatment of the sludge with the
attapulgitic clay by measuring the total parameters prescribed by the Council
Decision 2003/33/EC. Leached concentrations of all parameters were determined
by applying the L/S=10 leaching procedure according to EN 12457-4. Furthermore
the sludge samples were studied by X ray diffraction (XRD) and scanning
electron microscopy (SEM) techniques. Lastly, the sludge samples were measured
for their possible radioactive content.
The only mineralogical phases in the sludge sample, identified by XRD, were
quartz and calcite. Several grains containing the elements Fe, Mn, Pb, Cu, Zn,
Cr, Ti, Ba, and Al were identified by SEM. Analytical results of treated sludge
collected one month after the application of attapulgitic clay showed a
significant reduction of water leachable fraction for several parameters: As
38%, Cu 64%, Hg 100%, Mo 52%, Pb 50%, Se 51%, Zn 38%, phenols 80%. With respect
to pathogens, a significant reduction up to 99.9% for E. coli and fecal
coliforms was observed. Mixing also reduced the moisture content of treated
material and preserved pH values under certain conditions.
It is proposed that the method is further applied in a pilot scale field
experiment combined with aerobic digestion and composting in order to further
reduce the organic component and pathogens in sludge. Overall, the developed
laboratory scale method using attapulgitic clay as an additive is a promising
sludge treatment technique at a competitive cost under present market
conditions.
Keywords:
Sewage sludge, Attapulgitic clay, Treatment, Leaching experiments, Santorini Greece
