Efficient treatment of oil sands produced water: Process integration using ion exchange regeneration wastewater as a chemical coagulant

The potential of ion exchange regeneration wastewater (IERW) containing magnesium ions to act as a coagulant for steam-assisted gravity drainage (SAGD) boiler blowdown (BBD) water was investigated with the aim of reducing the water consumption in a SAGD plant. Conventional techniques for the treatment of BBD water require significant operational costs as they rely on the extensive use of chemical coagulants or electric power. Since the proposed process design in this study uses a wastewater stream for the treatment of the BBD water, operational costs and energy consumption are predicted to be minimized. The effect of temperature, the mixing ratio of BBD and the IERW water, and the stirring intensity on the removal of organic matter and dissolved minerals were investigated. Usage of IERW as the coagulant enhanced the removal of impurities; removal efficiency of 81.1% and 98.6% were obtained for organic matter and silica concentration, respectively. The treatment of BBD water by IERW, however, has led to an increase in the concentration of calcium in the effluent, which was effectively mitigated by soda ash softening. Furthermore, resource recovery from the coagulated sludge was explored by SEM, EDX, FTIR, XPS, and XRD, and revealed that the precipitated compounds were mostly composed of calcium, magnesium, and silica. Additionally, the successful usage of IERW for the treatment of another BBD wastewater with a higher concentration of organic matter was demonstrated. In conclusion, the IERW water proved to be highly effective in removing contaminants from SAGD produced water.