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Toxicity and mutagenecity of urban wastewater treated with
different purifying processes
José Daniel Sánchez Mata, Virginia
Fernández, Andrés Chordi, Carmen Tejedor*
Departamento de Microbiología
y Genética, Universidad de Salamanca, Av. Campo Charro
s/n, 37003 Salamanca, España
* Corresponding author email ctg@gugu.usal.es
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Abstract
The toxicity and mutagenecity of 1000-fold concentrates
of 5 litre samples of wastewater from five different towns (containing
500, 600, 15000, 50000 and 190000 inhabitants) with different sewage
treatment processes were determined. Two kinds of samples, including
municipal wastewater entering the sewage treatment plants and the
effluents discharged into the environment were analysed. After concentration
through resins, overall toxicity was evaluated using the bioassay
employing Photobacterium phosphoreum and samples were classified
according to Vasseur et al. (1986) as 'Non-toxic', 'Slightly toxic',
'Toxic' or 'Highly toxic'. Mutagenecity was evaluated using the
mutagenecity index determined by the Ames test, and samples were
classified as 'Non-mutagenic', 'Slightly mutagenic', or 'Mutagenic',
according to the 'two-fold' rule. The results obtained varied considerably;
such that in some plants the toxicity values decreased during treatment
whereas in others they remained unmodified or increased. None of
the extracts analysed proved to be mutagenic. The data on toxicity
and mutagenecity of the samples are apparently not correlated.
Keywords: Sewage, Ames test, bioluminescence
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