Effects of single and combined olive mill wastewater and olive mill pomace on the growth, reproduction, and survival of two earthworm species (Aporrectodea trapezoides, Eisenia fetida)
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Date
2021
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Abstract
The extraction processes of olive oil produce huge amounts of by-products, such as olive mill wastewater
(OMWW) and olive mill pomace (OMP), these by-products have significant polluting properties related to their
undesirable color and odor, high organic load, acidic pH, high phenolic compounds, high salinity, while their
effect on soil organisms is unclear. The study into the effects of these by-products on soil bioindicators, such as
earthworms should therefore be prioritized. Indeed, the purpose of this study was to evaluate the effect of
environmentally realistic concentrations of olive mill wastewater and olive mill pomace on the growth, reproduction,
and
survival
of
the
earthworms
Aporrectodea
trapezoides,
and
Eisenia
fetida.
Bioindicators
were
exposed
under
laboratory
conditions
to
increasing
doses
(12.5%,
25%,
50%,
75%,
and
100%
w/w)
of
OMWW
and
OMP
separately
and
in
combination.
The
results
showed
a
higher
growth
rate
on
Eisenia
fetida
when
exposed
to
12.5%
OMP,
with a neutral effect on reproduction and survival. Toxicological effects were found at higher doses,
namely: there was no cocoon production, growth inhibition, and mortality; these effects were probably due to the
higher level of phenolic compounds and higher salinity. In general OMP was found to have toxicity higher than
OMWW, the combination of both by-products showed stronger effects on some earthworm endpoints.
Comparative responses between the two species showed that Aporrectodea trapezoides proved to be more tolerant.
Dilution and bioremediation of these by-products is recommended as a possible solution to reduce their toxicity.