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Phosphorus (P) losses from agricultural fields through leaching are the main contributors to eutrophication of lakes and rivers in North America. Adoption of P-retaining strategies is essential to improve the environmental quality of water bodies. The main objective of this study is to evaluate lime as a soil amendment in reducing phosphorus concentration in the leachate from three common soil textures with neutral to alkaline pH. Phosphorus leaching from undisturbed soil columns (10 cm in diameter and 20 cm deep) as well as small repacked columns was investigated and compared in this study. Lime (high calcium hydrated lime) at the rate of 1% by air-dried soil mass was applied to the topsoil of the columns. Both sets of experiments followed a full factorial design with two factors of soil texture at three levels (sandy loam, loam, and clay loam) and treatment at two levels (control and limed) with three replicates. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was performed on the control and limed soil samples to confirm the formation of calcium phosphate compounds. For both intact and repacked columns, dissolved reactive phosphorus (DRP) concentrations in the leachates from limed sandy loam and limed loam soil columns was significantly reduced, while DRP in the limed clay loam column leachates was not changed. Elemental mapping demonstrated that in limed sandy loam and loam soils, the calcium loadings on the soil surface were always linked with phosphorus. The formation of calcium phosphate compounds and the increased phosphate adsorption on the soil surface through Ca bridging could be the two main phosphorus-lime retention mechanisms. Total dissolved phosphorus (TDP) in the leachates of limed loam and limed clay loam indoor intact and repacked columns was reduced, while there was no change in that of the sandy loam soil. In finer textured soils, lime can increase TDP retention through the immobilization of organic phosphates. The impact of lime application on DRP and TDP varied with the soil texture. The lime-induced reduction in the DRP and TDP was variable between the intact and repacked columns demonstrating the importance of soil structure on phosphorus and lime interactions in the soil. Overall, lime application at the studied rate can be considered a promising soil amendment in mitigating phosphorus loss from non-calcareous neutral to alkaline soils.

Oil sands tailings have a limited ability to dewater and can also release toxic water, so finding a cost-effective tailings reclamation strategy has been challenging. End pit lakes (EPLs) are being examined as one potential approach to reduce fluid fine tailings (FFT) inventories for the oil sands industry. This study investigated the effect of adding lime (650 to 4000 ppm) on FFT dewatering and improving cap water quality under the simulated EPL scenario. The results illustrated that a high lime dose of 3500 ppm achieved the highest FFT water recovery, decreased the cap water alkalinity at the end of the experiment (after 90 d), and increased the possibility of cation exchange (at day 0). In contrast, the degradation of petroleum hydrocarbons was slightly enhanced at low lime dose of 650 ppm in comparison to high doses. In addition, the 650 ppm dose resulted in minimal change in the microbial cell counts at day 90, compared with high lime doses that resulted in a large reduction in the cell counts. Comparisons of toxicity of the FFT pore water after lime addition exhibited higher toxic effects for lime dosages >1600 ppm. Nevertheless, at all lime doses, low cap water toxicity (i.e.

Over 80% of Athabasca, Alberta, Canada oil sands deposits are suitable for in-situ bitumen recovery processes. Steam assisted gravity drainage and cyclic steam stimulation processes are commercially implemented with current bitumen production capacity of about 850,000 bbl/d, which is projected to exceed 5000,000 bbl/d in the next two decades. Efficiency of these processes would be improved by reducing the steam-to-bitumen ratio. For this purpose addition of light hydrocarbons into steam as a solvent to reduce bitumen viscosity has been studied for decades with a limited commercial success. As an alternate strategy to solvent co-injection with steam, reduction of bitumen–water interfacial tension by co-injection of a surfactant, such as biodiesel (fatty acid methyl esters), with steam was proposed ( Babadagli et al., 2009 . Use of biodiesel as an additive in thermal recovery of heavy-oil and bitumen. In: Paper 049 Presented at the Canadian International Petroleum Conference (CIPC), 16–18 June, Calgary, Alberta, Canada; Babadagli and Ozum, 2012 . Oil Gas Sci. Technol.: Rev. IFP Energies Nouvelles 67 (3), 413–421). The present study focuses on three issues: (i) viscosity of bitumen in the neighborhood of the edge of the steam chamber using heat conduction models, where bitumen mobility should be controlled by viscosity and bitumen–water interfacial tension; (ii) generate bitumen recovery data, operating the steam chamber as a pressure cooker; where bitumen mobility should be controlled mainly by viscosity rather than bitumen–water interfacial tension, since the influence of the creeping flow of water-condensed steam is marginally small; and, (iii) measure bitumen content at different heights of the pressure cooker test spent core samples to predict bitumen mobility and permeability. Pressure cooker tests were performed using steam, steam and pentane as a solvent at 5%, 10% and 15% of bitumen by mass, and steam and biodiesel as a surfactant additive at 0.2% and 0.3% of bitumen by mass dosages. Our test results showed that solvent, such as pentane, addition reduced bitumen recovery as the dosage of solvent addition increased from 5% to 15% of bitumen. This observation is interpreted that while solvent addition reduces bitumen viscosity it also increases bitumen–water interfacial tension; the overall effect of which results in reduction of bitumen recovery efficiency. When biodiesel was used as a surfactant additive at 0.2% and 0.3% of bitumen by mass dosage, a slightly increase in bitumen recovery efficiency was observed. Bitumen mobility and bitumen permeability values predicted in this study were one order of magnitude smaller than that of the values reported in the literature; probably resulting from reduced bitumen–water interfacial tension, by the activation of natural surfactants contained in bitumen, promoting bitumen mobility in the field operations. Result of the present study suggests that further tests and modeling studies are needed to understand effects of bitumen viscosity reduction by solvent co-injection and bitumen–water interfacial tension reduction by surfactant co-injection with steam on the efficiency of steam assisted bitumen recovery processes.

In Alberta, Canada bitumen is commercially produced by in-situ processes at about 830,000 bbl/d capacity, production capacity is projected to exceed 5,000,000 bbl/d in the next two decades. Steam assisted gravity drainage (SAGD) process is one of the in-situ bitumen recovery processes; the economics and efficiency of which would be improved by reducing the steam to bitumen ratio. For this purpose, the addition of light hydrocarbon solvents into steam as a solvent to reduce bitumen viscosity has been studied; however, several decades of research efforts has resulted in only limited commercial success. More recently, as an alternative to solvent addition, the use of biodiesel (fatty acid methyl esters) with steam as a surfactant additive reducing bitumen-water interfacial tension was proposed and studied experimentally (Babadagli et al, 2009; Babadagli and Ozum, 2010). In the present study, experiments were performed at typical reservoir pressure conditions to evaluate the performance of solvent (pentane) addition with steam to reduce viscosity and biodiesel addition with steam to reduce bitumen-water interfacial tension to improve bitumen recovery efficiency. The results showed that bitumen recovery efficiency may decrease with the addition of hydrocarbon solvent if the solvent is added after a certain period of steam injection. Solvent addition to the steam was tested at 5% and 15% of bitumen mass dosages. Steam assisted bitumen recovery tests with biodiesel addition under 2-g/kg-bitumen dosage showed an increase in bitumen recovery efficiency. To further investigate the reasons behind the lowered recovery with solvent addition, an analytical model was developed to predict heat transfer and pressure fields in the reservoir causing Darcy flow, and therefore, bitumen mobility. The distribution of the aqueous and solvent phases injected in time and space considering the phase change (steam and solvent condensation) effect with respect to steam chamber were clarified for different injection conditions and scenarios. The results and observation will be useful in defining the appropriate application conditions for both solvent as a viscosity reducer and biodiesel as an interfacial tension reducer additive in SAGD operations.