Factors That Affect the Degradation of Naphthenic Acids in Oil Sands Wastewater by Indigenous Microbial Communities

Abstract

Abstract-The acute toxicity of wastewater generated during the extraction of bitumen from oil sands is believed to be due to naphthenic acids (NAs). To determine the factors that affect the rate of degradation of representative NAs in microcosms containing wastewater and the acute toxicity of treated and untreated wastewater, the effects of temperature, dissolved oxygen concentration, and phosphate addition on the rate of 14 CO 2 release from two representative naphthenic acid substrates, (linear) U-14 C-palmitic acid (PA) and (bicyclic) decahydro-2-naphthoic acid-8-14 C (DHNA), were monitored. Tailings pond water (TPW) contained microorganisms well adapted to mineralizing both PA and DHNA: PA was degraded more quickly (10-15% in 4 weeks) compared to DHNA (2-4% in 8 weeks). On addition of phosphate, the rate of NA degradation increased up to twofold in the first 4 weeks, with a concurrent increase in the rate of oxygen consumption by oil sands TPW. The degradation rate then declined to levels equivalent to those measured in flasks without phosphate. The observed plateau was not due to phosphate limitation. Decreases in either the dissolved oxygen concentration or the temperature reduced the rate. Phosphate addition also significantly decreased the acute toxicity of TPW to fathead minnows. In contrast, Microtox analyses showed no reduction in the toxicity of treated or untreated TPW after incubation for up to 8 weeks at 15ЊC.

Tree Swallows (Tachycineta Bicolor) Nesting on Wetlands Impacted by Oil Sands Mining Are Highly Parasitized by the Bird Blow Fly Protocalliphora Spp.

“…Mine tailings are transferred from settling basins into excavated areas such as mined-out pits and constructed wetlands, where they are subsequently capped with a layer of clean water (Gulley and MacKinnon, 1993). It is anticipated that most of the acute toxicity to aquatic organisms will be mitigated by natural processes such as microbial biodegradation (Lai et al, 1996). However, the longterm ecological impacts of this reclamation strategy are still unknown.…”

Biodegradation Kinetics of Geometric Isomers of Model Naphthenic Acids in Athabasca River Water

“…NAs from the Athabasca Oilsands have been characterized according to their z group (0,2, -4, -6, etc. ) and carbon number distribution (C, to Cro) (Lai et al, 1996). In general, NAs are believed to be relatively persistent in natural waters and have thus been utiiized as tracers or biomarkers for determining the maturation of petroleum sources in oil exploration (CONRAD, 1998).…”

Ácidos naftênicos no petróleo

“…4,22,29,30 Outros ácidos, tais como, dicarboxílicos ou contendo anéis aromáticos, podem estar presentes em pequena quantidade. 4,26,31 Os ácidos naftênicos seguem, predominantemente, a estrutura representada na Figura 1(A), na qual m representa o nú-mero de grupos (-CH 2 -), n o número de anéis e R a cadeia alquílica.…”

“…2,4,5,27,31,55,56 Derivados de ácidos naftênicos solúveis em água são responsáveis por reduzir a qualidade da água de rejeito no processo de extração do betume em Atabasca. 45 Esses ácidos naftênicos têm sido citados, em vários trabalhos, como tóxicos para peixes, animais e plantas, [55][56][57][58] embora não exista um método de rotina para identificar ou isolar os componentes específicos responsáveis pela toxicidade.…”