|
|
Animal Defenders of Westchester |
|
Home Page We advocate on all animal protection and exploitation issues, including experimentation, factory farming, rodeos, breeders and traveling animal acts. Animal Defenders of Westchester |
Articles
LEATHER TOXICITY REPORT FROM WWW.RSE.UQUEBEC.CA
Bibliographical record Yatrabi A. & A. Nejmeddine (2000). Fractionation and mobility of heavy
metals in soil receiving tannery waste waters. Rev. Sci. Eau 13 (3) :
203-212 [article in French] Original title: Fractionnement et mobilit� des m�taux lourds dans un sol
en amont des eaux us�es de tanneries. Summary In Morocco, the town of Marrakesh, as in other areas of the country, is
subject to multiple daily aggressions generated by industrial pollution, in
particular from tanneries. The tannery waste water is discharged directly
into the aquatic and terrestrial ecosystems without any preliminary
processing. In order to evaluate the danger that can be generated by tannery
effluents in the receiving ecosystems, and to study the ecotoxicological and
environmental impact resulting from that chemical treatment of these
effluents, we determined, before and after treatment, the inhibitory effect
of the two most polluted effluents originating from manufactured leather:
liming-deliming and chromium tanning. The purpose of our investigation was thus to evaluate the acute toxicity
of the chromium tanning and epilage-coat waste waters before and after
chemical treatment. The invertebrate Daphnia pulex was used for the toxicity
test and the toxicity due to these industrial waste waters was evaluated by
regression analysis. The processing carried out on the chromium tanning
waste water consisted of precipitation with sodium carbonate at different pH
values. The treatment of liming-deliming wastewaters consisted of an
elimination and recovery of the sulphide compounds without carrying out
their degradation. The chromium level was determined by atomic absorption spectrophotometry
with graphite furnace atomization. The results of the toxicity test showed
that the investigated chromium tanning and liming-deliming effluents
presented were toxic, with respective IC50- 24h values of 0.15 and 3.36
(expressed as dilution ratios). This toxicity could be explained by high
levels of chromium, sulphides and organic matter in these waste waters. It
is however difficult to correlate the IC50 values obtained with those of the
physical- chemical parameters. The tested effluents are very complex
matrices. On the other hand, we noticed a notable difference between these two
effluents. The mineral tanning effluent is contaminated with chromium and
organic matter, whereas the second is especially rich in organic matter and
sulphide. The total chromium concentration corresponding to the IC50-24h value of
the raw chromium tanning effluent is lower than that which would be expected
on the basis on the known toxicity of K2Cr2O7, showing the toxicity of raw
chromium waste waters is due not only to chromium, but also to other
chemicals used during the manufacturing process of leather. After processing by chemical precipitation, the IC50-24h values increased
from 0.15 to 26.6 and from 3.36 to 11.1 respectively, for the chromium
tanning and the epilage-coat effluents. Consequently, these treated sewages
can be classified as low toxicity wastes. The comparison of the results is
very difficult considering that the test conditions and the physicochemical
and heavy metal characteristics of the effluents vary enormously over time,
without forgetting the physicochemical composition of the experimental
solution used by standard OECD (fresh water) and the standard ISO (synthetic
water). From where necessity to vary tests for determining well the degree
of an effluent toxicity which the effects appear differently at various
levels trophic. The diminution observed in the toxicity of the effluents is linked to a
reduction of suspended matter (95 %), COD (55 %), Cr (90 %) and sulphides
(50 %). Hence, this treatment presents at least two advantages. The first is
environmental as just mentioned. The second is economic since chromium can
be recycled for reuse in leather tanning. The results suggest that the
recovered chromium is similar to commercial tanning chromium. These results
also show that the fixing of chromium does not depend on the nature of the
treated skin. In fact, a technical and economic analysis showed that
proposed treatment can be economically beneficial (3112,5 $ per 1000 tons of
skins). Author's address A. Nejmeddine, Laboratoire d'�cotoxicologie, D�partement de biologie, Fair Use Notice: This document may contain
copyrighted material whose use has not been specifically authorized by the
copyright owners. We believe that this not-for-profit, educational use on
the Web constitutes a fair use of the copyrighted material (as provided for
in section 107 of the US Copyright Law). If you wish to use this copyrighted
material for purposes of your own that go beyond fair use, you must obtain
permission from the copyright owner. |
Your comments and
inquiries are welcome
(d-8)
This site is hosted and maintained by:
The Mary T. and Frank L. Hoffman Family Foundation
Thank you for visiting all-creatures.org.
Since 