Process Scale-up for Rapid Naphthenic Acid Removal from Oil sands Process Waters (OSPW).

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With worldwide production of light crude oil reserves expected to last ~50 yrs, there is a need to exploit alternative fuel resources e.g. oil sands. The vast oil-sand resources in N & S America are already being exploited, resulting in large-scale environmental pollution. During bitumen extraction from oil sands, large volumes of wastewaters (tailings) are produced that are stored in vast settling ponds. Currently ~840 million m3 of tailings have accumulated in Canada alone. There are several problems with tailings ponds: vast amounts of biogenic greenhouse gases are emitted (e.g. 43,000 m3 / day CH4 from one pond), they have very slow consolidation (settling) of the fine tailings solids, which may take decades. Tailings storage poses huge environmental risks due to the presence of high concentrations of toxic compounds known as naphthenic acids (NAs). NAs are complex mixtures of aliphatic & aromatic acids that are highly toxic to many organisms including humans. NAs also block/ corrode pipes/ processing equipment causing further pollution and billion-dollar losses to the industry. Thus, removing NA contamination is important to the global economy, environment and human health. Microbial treatment of NAs has clear cost-environmental advantages. However, the transformation of NAs is complex and influenced by a combination of microbial interactions, biogeochemical factors and the physical-chemical properties of the NAs. Our previous work showed the more recalcitrant NAs have high molecular weights, and are highly branched. This is of environmental concern as these more highly branched NAs may accumulate in the environment. Recently, we developed a bioreactor that achieved 87% NA removal within days. Our bioreactor treatment also increased tailings sedimentation rates. Although our prototype gravel bed bioreactor is a significant advance for the rapid removal of NAs on a lab-scale, we lack information as to whether it can operate as efficiently (for both NA removal & detoxification) under field-scale processing conditions and with several different waste feeds. Since each operator uses a different NA extraction method, the resulting wastewaters have different physical-chemical characteristics and contain different NA compositions/concentrations. It is thus crucial to test the bioreactor technology in a scale-up process and measure the efficacy of NA removal, detoxification and increased sedimentation, in relation to different wastewaters. Once validated under field-scale trials, the technology will allow operators to recycle wastewater, increase sedimentation rates and reduce the amount of stored tailings, thus reducing capital/ storage costs and environmental risk. Our proposed project involves an international collaboration that integrates the process-scale-up facilities and expertise at the Oil Sands Tailings Research Facility (OSTRF), University of Alberta (UoA), expertise and facilities in process-scale up modeling and analytical chemistry, University of Calgary (UoC), access to field sites and different process feeds (DuPont, Syncrude, Suncor (via UoC), Shell Canada pus other operators (via Alberta Environmental (AE) and expertise for implementing the technology to end users via the Albertan Government Regulator, AE. Overall aim: to develop our optimized bioreactor technology and process into a cost-effective system, that can remove NAs (both amount & toxicity) from different wastewaters at the field-scale. Specific Aims: 1) To quantify bioreactor effectiveness for NA removal and NA detoxification (including metabolite toxicity) from different wastewaters (i.e. from different operators) at lab-, intermediate and field-scale; 2) To investigate the effectiveness of the bioreactor technology for increasing sedimentation rates at each scale; 3) Characterize changes in microbial community structure during treatment (at each scale) to ensure microbial community integrity is maintained throughout.