Inhibition and biotransformation potential of naphthenic acids under different electron accepting conditions

Naphthenic acids (NAs) are a complex group of alkyl-substituted acyclic, monocyclic and polycyclic carboxylic acids present in crude oil, oil sands process water and tailings ponds, as well as in refinery wastewater. Bioassays were performed to investigate the biotransformation potential and inhibit...

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Bibliographic Details
Published in:Water research (Oxford) 2013-01, Vol.47 (1), p.406-418
Main Authors: Misiti, Teresa, Tandukar, Madan, Tezel, Ulas, Pavlostathis, Spyros G.
Format: Article
Language:English
Subjects:
Applied sciences
Bacteria
Bacteria - metabolism
bioassays
Biodegradation
Biological and medical sciences
Biological treatment of waters
Biotechnology
Biotransformation
Carbon
carbon dioxide
Carboxylic Acids - chemistry
Carboxylic Acids - metabolism
Culture
Degradation
Denitrification
energy
Environment and pollution
Exact sciences and technology
Fermentation
Fundamental and applied biological sciences. Psychology
Hydrogen-Ion Concentration
Industrial applications and implications. Economical aspects
Industrial wastewaters
Inhibition
Methane
methane production
Methanogenesis
methanogens
mixed culture
naphthenates
Naphthenic acids
nitrate reduction
Nitrification
nitrogen
oil sands
oils
Pollution
ponds
population size
Time Factors
volatile fatty acids
wastewater
Wastewaters
Water Pollutants, Chemical - chemistry
Water Pollutants, Chemical - metabolism
Water treatment and pollution
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Summary:Naphthenic acids (NAs) are a complex group of alkyl-substituted acyclic, monocyclic and polycyclic carboxylic acids present in crude oil, oil sands process water and tailings ponds, as well as in refinery wastewater. Bioassays were performed to investigate the biotransformation potential and inhibitory effect of a commercial NA mixture to nitrification, denitrification and fermentation/methanogenesis using mixed cultures not previously exposed to NAs. NAs inhibited nitrification in a mixed aerobic heterotrophic/nitrifying culture at concentrations as low as 80 mg NA/L, whereas, an enriched nitrifying culture was only affected at 400 mg NA/L. The lower nitrification inhibition in the latter assay is attributed to the higher population size of nitrosofying and nitrifying bacteria compared to the mixed heterotrophic/nitrifying culture. The NA mixture was not inhibitory to denitrifiers up to 400 mg/L. At higher NA concentrations, cell lysis was pronounced and lysis products were the main source of degradable carbon driving denitrification in culture series prepared without an external carbon source. In the presence of a degradable external carbon source, no difference was observed in nitrate reduction rates or nitrogen gas production at all NA concentrations tested. Methanogenesis was completely inhibited at NA concentrations equal to or higher than 200 mg/L. Methanogenic culture series amended with 80 mg NA/L were transiently inhibited and methane production in culture series prepared with NAs and an external carbon source or NAs only recovered in 136 and 41 days, respectively. Accumulation of volatile fatty acids was observed at inhibitory NA concentrations; however, carbon dioxide production was not affected by NAs, indicating that fermentation and acidogenesis were not affected by NAs. NAs were not degraded under nitrate-reducing or fermentative/methanogenic conditions used in the present study, regardless of the presence or not of another, degradable carbon/energy source. ► NAs ≥80 mg/L inhibited nitrifiers in a nitrifying/heterotrophic aerobic culture. ► An enriched nitrifying culture was inhibited by NAs only at 400 mg/L. ► Denitrifiers were not inhibited by NAs up to 400 mg/L. ► Methanogens were completely inhibited at 200 mg NA/L or higher. ► NAs were degraded by aerobic heterotrophs but not by denitrifiers or methanogens.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2012.10.019