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Sewage sludge ash 123

In many countries, there is a continuous increase in the requirements concerning
wastewater discharge and more restrictive control regulations about SS disposal
options have been observed. In 2005, the total production of SS in the European
Union was 10Mt, and in the United States it was 7 Mt (Cyr et al., 2007). Several
disposal options may be developed for enhancing the management of these huge
amounts. Initially, SS was applied, directly or indirectly, to the soil for agriculture
and forestry activities, or alternately disposed by landfilling. Many restrictions due
to the presence of heavy metals and pathogenic agents diminished the application
of SS as a soil amendment or fertilisation. Additionally, many regulations tried to
reduce the amount of landfilled SS. For example, according to the European direc-
tive EU 99/13/EC, it was obligatory to reduce 75% of biodegradable waste to land-
fills by the end of 2010 with respect to the amount produced in 1995 (Stasta et al.,
2006). Certainly, the feasible SS disposal alternatives, such as thermal treatments
(incineration, pyrolysis, gasification) will gain importance in the future because
they offer an important reduction in volume (up to 90%) and mass (up to 70%).
Additionally, the final product is sterile and odourless, and in many cases, it can be
considered as an inert residue (Tay et al., 1991; Lynn et al., 2015).
Cyr et al. (2007) provided a summary of the SS disposal for European countries,
Canada and the United States. Fig. 5.1 depicts that some countries, such as the
Netherlands, Austria, Switzerland and Canada incinerated more than 40% of SS.
Also, Denmark, USA, Germany, United Kingdom and Belgium incinerated between
20% and 40% of SS.

Figure 5.1 Disposal proportions of sewage sludge ash in European countries, Canada and
the United States (Cyr et al., 2007).