In recent years, ecotoxicological tests have become a essential
tool to evaluate the environmental impact of chemicals released
into the environment, since in these tests the (eco)toxicity of the
contaminants is measured, taking into account chemical speciation
and bioavailability of contaminants, and synergistic or antagonistic
effects of the mixture constituents [1–4]. However, in most
regulations worldwide, the (eco)toxicity potential of wastes is
derived from classical chemical analysis interpretation, which is
used to determine the most appropriate destination or means
of disposal for waste material, according to its classification as
hazardous/non-hazardous and inert/non-inert properties. In Brazil,
federal guidelines classify the hazard status of industrial waste
based on the chemical constituents and on leaching and solubility
tests [5], similarly to the USA Code of Federal Regulations (CFR
Title 40, Part 260–265). Thus, Brazilian waste regulations classify solid wastes as hazardous (Class I) or non-hazardous (Class
II), Class II being split into Class II A (non-inert) and Class II B
(inert). In the European Union, the Hazardous Waste Council Directive
91/689/EEC has defined a set of 14 properties allowing waste
classification and one of them is the ecotoxicity property (H14),
which is defined as substances and preparations which present
or may present immediate or delayed risks for one or more sectors
of the environment [6]. However, in this directive there is no
reference to specific methods for ecotoxicity evaluation. In this context,
an experimental test strategy based on a battery of biotests
for waste toxicity characterization was published some years
ago [7].
On the other hand, the stabilization/solidification (S/S) of sludge
originating from wastewater treatment can provide an alternative
to waste disposal, and can originate products in a safe and profitable
manner. In this regard, technology involving the S/S processes is
currently being used to treat a wide variety of wastes containing
contaminants such as metals, organic compounds and soluble salts
[8–10], but it is most suitable for treating wastes that are predominantly
inorganic, as these are considered to be more compatible
with the types of cementitious materials normally used [11].