i with toxic organic and inorganic compounds. However, sludge

          i           
Sewage
Sludge

Course solids and bio solids accumulated in a
wastewater treatment process must be treated and disposed of in safe and
effective manner-creating sewage sludge. This material may be inadvertently
contaminated with toxic organic and inorganic compounds. However, sludge ash
has been investigated in the production of concrete. Results of several studies
have indicated the benefits of using sewage slag ash in concrete such as
compressive strength, freeze- thaw resistance and good hardening properties.
Sewage sludge ash may be used as a mineral filler substitute or as a portion of
the fine aggregate in hot mix asphalt paving.

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Course solids and bio solids accumulated in a
wastewater treatment process must be treated and disposed of in a safe and
effective manner-creating sewage sludge. This material may be inadvertently
contaminated with toxic organic and inorganic compounds. However, sludge ash
has been investigated in the production of concrete. Results of several studies
have indicated the benefits of using sewage slag ash in concrete such as
compressive strength, freeze- thaw resistance and good hardening properties.
Sewage sludge ash may be used as a mineral filler substitute or as a portion of
the fine aggregate in hot mix asphalt paving.

Currently, clay is widely used to produce LWA and
sludge can be used as a partial replacement for clay in the manufacture of LWA.
Production of LWA from different types of sludge is considered to be a very satisfactory
economic and environmental alternative, since a starting material with no value
becomes a product with important industrial application.

Dried sludge can be converted into artificial
lightweight aggregates, slags or bricks for the construction industry.
Different properties and destinations for these materials depend on different
process variables and operating conditions.

As of the use of dewatered sludge, the production of
Portland cement injecting the sludge directly into cement klins seems the most
appealing one. The major elements present in Portland cement are in fact Ca,
Si, Al and Fe, which compare reasonably well to the elements present in sewage
sludge.

Sludge can be exploited in construction industry in
other different forms such as dried sludge powder or incinerated ash, as will
be seen in next chapter.

Many technically feasible processes have been studied
and tested, but most of the techniques are not economically viable because of a
high production cost, if compared to market price (Bonfiglioli, 2014).