Inhibition of the anammox activity by aromatic compounds

• Short-term effect of several aromatics was evaluated over granular anammox sludge.
• The higher the concentrations of the aromatics, the higher the reduction of the SAA.
• Depending on the aromatic compound, toxic or inhibitory effect was measured.
• Synergistic effects were observed when mixtures of aromatic compounds were studied.

The short-term effect of several aromatic compounds (o-cresol, p-nitrophenol, o-chlorophenol and quinoline) was evaluated over granular anammox sludge cultivated over 2 years in a Sequencing Batch Reactor (SBR). The anammox granular sludge had an average size of 1.0 ± 0.2 mm and was enriched in Brocadia sp. Specific Anammox Activity (SAA) batch tests with this granular biomass were carried out in the presence of o-cresol, p-nitrophenol, o-chlorophenol, quinoline and their mixtures. The anammox biomass was never exposed to the tested aromatic compounds, prior to the SAA tests. The concentration and the mixture of aromatic compounds had a strong effect over the loss of the anammox activity. The higher the concentrations of the aromatic compounds, the higher the reduction of the SAA. Quinoline and p-nitrophenol have a lower negative effect compared to o-cresol and o-chlorophenol. The Luong inhibition model seems to adjust better the inhibition of anammox biomass by the tested aromatic compounds. Depending on the aromatic compound, toxic or inhibitory effect was measured. o-Cresol and o-chlorophenol caused a toxic effect whereas p-nitrophenol and quinoline produced an inhibitory effect. In general, synergistic effects were observed when mixtures of aromatic compounds were studied.

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