In the present study, the quality of effluents
from a conventional wastewater treatment plant in Italy has
been analyzed. Residual level of contamination by 4-
n-nonylphenol,
mono- and di-ethoxylated nonylphenols has
been recorded in the effluents that resulted to be also
phytotoxic and genotoxic. The possibility of exploiting
phytoremediation as a sustainable tertiary treatment for the
depletion of the priority pollutants and for the reduction in
the residual toxicity has been verified at mesocosm scale.
The phyto-based treatment has been performed by the
exploitation of
Phragmites australis
by either a bacterialassisted
and not assisted approach. In relation to the bacterial-
assisted approach, two new bacterial strains, capable
of using the nonylphenols as a sole carbon source, have
been isolated. One was identified as a plant growth-promoting
rhizobacteria (PGPR) belonging to the
Stenotrophomonas
species, and the second one was classified as
a
Sphingobium
species strain. Both strains were independently
bioaugmented in the
P. australis rhizosphere. In
relation to the not assisted approach, the phyto-based
process determined 87, 70 and 87 % for 4-
n-nonylphenol,
mono-ethoxylated nonylphenols and di-ethoxylated
nonylphenols, respectively. The toxicological assessment
of the process evidenced the complete depletion of either
the phytotoxicity or the genotoxicity of the treated effluents.
With reference to the bacterial-assisted approach, the
PGPR
Stenotrophomonas species strain resulted to be
capable of significantly increasing the efficiency of the
phyto-based process in nonylphenol depletion up to
88 % for the 4-
n-nonylphenol, 84 % for the mono-ethoxylated
nonylphenol and 71 % for the di-ethoxylated
nonylphenol.
