This paper presents guidelines for the selection and use of polyaluminum chloride (PACl) coagulants and alum in terms of raw water quality and treatment method. The concentration of natural organic matter (NOM) was found to be the most important parameter affecting coagulant dose. The nature of the NOM, as measured by the specific ultraviolet absorbance (SUVA), was useful for predicting the degree of NOM removal expected. Raw water turbidity and NOM did not influence the type of coagulant that was most effective. Raw water alkalinity, as it relates to the pH of coagulation, was found to be very important for choosing one coagulant type over another.PACl basicity should be matched to raw water alkalinity, so that coagulation pH is as close as possible to the pH of minimum solubility of the coagulant. The solids separation process used for treatment was also found to be important for coagulant selection. Raw waters coagulated with PACls containing sulfate were found to have the best settling characteristics, but showed the highest headloss rates in direct filtration applications. Dissolved air flotation (DAF) performance was relatively insensitive to coagulant type.

Steam assisted gravity drainage (SAGD) boiler blow-down (BBD) water contains high concentrations of dissolved organic matter (DOM) and total dissolved solids (TDS). A detailed understanding of the BBD chemistry, particularly the DOM composition, is important for better management and recycle of this water. In this study, we fractionated the dissolved organic matter in the BBD using DAX-8, Dowex, and Duolite resins into hydrophobic and hydrophilic fractions of acid, base, and neutral compounds. Additionally, the DOM was fractionated on the basis of size by filtering the BBD through a series of membranes with progressively tighter molecular weight cutoffs of 10, 3, and 0.5 kDa. Fluorescence excitation−emission matrix spectroscopy (EEMs), specific UV absorbance (SUVA), and FTIR were used to characterize the water samples and the different fractions. The ion exchange fractionation revealed that the DOM contained a high percentage of hydrophobic acids (39%) and hydrophilic neutrals (28.5%). The different ion exchange fractions had distinct fluorescence excitation−emission signatures. The permeate samples from the membrane fractionation, on the other hand, did not reveal any significant difference in the fluorescence EEM spectra, indicating that the hydrophilic and hydrophobic constituents of the DOM could not be separated on the basis of pore size by these membranes. The SAGD boiler blow-down water was found to be significantly concentrated in DOM compared to oil sands mining process affected water.

A B S T R A C TCross-flow ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) were applied for the first time on a produced water obtained from a thermal in situ bitumen recovery process called steam-assisted gravity drainage (SAGD), with the intent to remove salt, silica, and dissolved organic matter (DOM) so that the produced water could be re-used as highquality boiler feedwater. It was found that more hydrophilic and more negatively charged membranes were less susceptible to fouling. The UF membrane tested rejected a maximum of 30% of the salt and silica and 50% of the DOM. Nanofiltration with loose membranes removed more than 70% of the salt and DOM. The tight NF membranes tested removed more than 86% of the salt, silica, and DOM, and consumed less energy than RO, which showed almost the same rejection. An instantaneous increase in water flux resulting from a step change in feedwater pH demonstrated the critical role of pH in flux recovery and in fouling mitigation. Analysis of the fouled membranes indicated presence of silica, iron, and calcium in the foulant material. Feed and permeate characterization showed that mainly hydrophilic DOM passed through the membrane. The study provides valuable insights regarding the suitability of membranes as alternatives to conventional SAGD water treatment methods, especially in terms of producing higher quality recycled water.

In thermally enhanced oil recovery operations, particularly in steam-assisted gravity drainage (SAGD), boiler blowdown (BBD) containing high concentrations of dissolved organic matter (DOM), dissolved silica, and total dissolved solids (TDS) is generated. To develop efficient tools for managing this blowdown, a detailed understanding of its chemistry is required. In this study, BBD was evaporated to yield ∼66% condensate and ∼33% concentrate blowdown (CBD). Detailed characterization of the BBD and CBD water was conducted. The effect of acidification was also studied. The acidification coprecipitates the silica and DOM, with over 90% of the silica and over 40% of the DOM precipitating at pH 4. Ultrafiltration treatment was also examined, and a major fraction of the silica and DOM in the CBD was found to foul a 100 kDa ultrafiltration membrane in the pH range of 7.5 to 9. The analysis revealed that the dominant fouling mechanism was cake filtration, indicating the formation of a silica−DOM precipitate layer on the membrane surface. These studies can provide insight regarding management options for SAGD disposal water.

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