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Appl. Environ. Microbiol., Nov 1995, 3889-3893, Vol 61, No. 11
BA Donlon, E Razo-Flores, JA Field and G Lettinga
N-substituted aromatics are important priority pollutants entering the
environment primarily through anthropogenic activities associated with the
industrial production of dyes, explosives, pesticides, and pharmaceuticals.
Anaerobic treatment of wastewaters discharged by these industries could
potentially be problematical as a result of the high toxicity of
N-substituted aromatics. The objective of this study was to examine the
structure-toxicity relationships of N-substituted aromatic compounds to
acetoclastic methanogenic bacteria. The toxicity was assayed in serum
flasks by measuring methane production in granular sludge. Unacclimated
cultures were used to minimize the biotransformation of the toxic organic
chemicals during the test. The nature and the degree of the aromatic
substitution were observed to have a profound effect on the toxicity of the
test compound. Nitroaromatic compounds were, on the average, over 500-fold
more toxic than their corresponding aromatic amines. Considering the facile
reduction of nitro groups by anaerobic microorganisms, a dramatic
detoxification of nitroaromatics towards methanogens can be expected to
occur during anaerobic wastewater treatment. While the toxicity exerted by
the N-substituted aromatic compounds was closely correlated with compound
apolarity (log P), it was observed that at any given log P, N- substituted
phenols had a toxicity that was 2 orders of magnitude higher than that of
chlorophenols and alkylphenols. This indicates that toxicity due to the
chemical reactivity of nitroaromatics is much more important than
partitioning effects in bacterial membranes.
Copyright © 1995, American Society for Microbiology
Toxicity of N-substituted aromatics to acetoclastic methanogenic activity in granular sludge
Department of Environmental Technology, Wageningen Agricultural University, The Netherlands.
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