Naphthenic acids and surrogate naphthenic acids in methanogenic microcosms

• Published in: Water research (Oxford) 2001-08, Vol.35 (11), p.2595-2606
• Main Authors: Holowenko, Fervone M, MacKinnon, Michael D, Fedorak, Phillip M
• Format: Article
• Language: English
• Subjects: 3-cyclohexylpropanoic acid; 4-cyclohexylbutanoic acid; Acetates - metabolism; Applied sciences; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Biotechnology; Canada; Carboxylic Acids - analysis; Carboxylic Acids - chemistry; Environment and pollution; Euryarchaeota - growth & development; Euryarchaeota - metabolism; Exact sciences and technology; fine tailings; Fundamental and applied biological sciences. Psychology; Hydrogen - metabolism; Industrial applications and implications. Economical aspects; Industrial Waste - analysis; Industrial wastewaters; Methane - metabolism; methanogens; Molecular Structure; naphthenic acids; Petroleum; Pollution; Sewage - chemistry; Sewage - microbiology; sewage sludge; Silicon Dioxide - analysis; Silicon Dioxide - chemistry; Wastewaters; Water Purification - methods; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(00)00558-3

Naphthenic acids (NAs) are a complex mixture of naturally occurring acyclic and cyclic aliphatic carboxylic acids in petroleum. In the Athabasca oil sands, NAs have been identified as the largest component of dissolved organic matter in the tailings waters from oils sands extraction processes. They are the major contributor to the acute toxicity of the fine tailings wastewaters at the oil sands extraction plants in northeastern Alberta, Canada. In this study, three sources of NAs were studied, including commercially available NAs, those extracted from oil sands process-affected waters, and individual naphthenic-like surrogate compounds. Analysis by gas chromatography–mass spectrometry demonstrated differences between the commercial and extracted NAs. The NAs derived from the process-affected waters showed a short-term inhibition of methanogenesis from H 2 or acetate, but with time the populations resumed methane production. It has been postulated that microbial metabolism of the carboxylated side chains of NAs would lead to methane production. The two NA mixtures failed to stimulate methanogenesis in microcosms that contained either oil sands fine tailings or domestic sewage sludge. However, in microcosms with sewage sludge, methanogenesis was stimulated by some surrogate NAs including 3-cyclohexylpropanoic acid at 400–800 mg/L, 5-cyclohexylpentanoic acid at 200 mg/L or 6-phenylhexanoic acid at 200 and 400 mg/L. When added at 200 mg/L to methanogenic microcosms containing fine tailings, 3-cyclohexylpropanoic and 4-cyclohexylbutanoic acids produced methane yields that suggested mineralization of the side chain and the ring.