Pilot-scale study on the reverse osmosis treatment of oil sands tailings pond water: Impact of pretreatment on process performance

The oil sands industry has recently focused on both reducing their freshwater usage and maximizing the reuse of process water. This study is one of the few pilot-scale investigations reporting the ability of reverse osmosis (RO) to treat recycle water (RCW) from an oil sands facility. Two distinct treatment trains were assessed to evaluate the impacts of pretreatments on the RO performance. Treatment train 1 consisted of coagulant addition, ceramic ultrafiltration (CUF), antiscalant, and a single-pass RO system operated at natural pH, while the treatment train 2 included softening, coagulant addition, CUF system, weak acid cation ion exchange, antiscalant addition, and an RO system operated at alkaline pH. RO permeate fluxes normalized to 25 °C of approximately 31–39 L/m2·h at 72% recovery and 38–52 L/m2·h at 85% recovery were recorded for treatment trains 1 and 2, respectively. At these conditions, the two treatment trains resulted in total dissolved solids lower than 18 mg/L, while the dissolved sodium concentrations were below 7 mg/L. During the pilot tests, clean-in-place procedures were not required for both treatment configurations, highlighting the effectiveness of the pretreatment steps to reduce the RO membrane foulants. © 2015 Elsevier B.V. All rights reserved.

This pilot-scale study investigated the role of different treatment steps on the performance of RO membranes when treating RCW from an oil sands facility. The two treatment trains assessed in this study resulted in nearly complete solids removal. In addition, the TDS and sodium levels were well below the target values, with TDS values lower than 18 mg/L and dissolved sodium concentrations below 7 mg/L. The results indicated that the CUF membrane could accomplish the removal of TSS and turbidity without any extensive pretreatment as showed by treatment train 1. As such, CUF systems without intensive physico-chemical pretreatment could have promising applications for RCW treatment, resulting in huge benefits to the oil sands industry. The treatment train 2 provided extensive pretreatment by including softening, a CUF system and ion exchange, resulting in the reduction of hardness-causing ions to negligible levels. CIP procedures were not required for both treatment configurations, highlighting the effectiveness of the pretreatment steps to reduce the RO membrane foulants. The goal of this pilot-scale study was to produce fit-for-purpose water. It is noteworthy that the pHs of the RO permeates were 6.5 and 9.6 for treatment trains 1 and 2, respectively. Therefore, pH adjustment may be required when opting for one treatment configuration. Moreover, the selection of one treatment train will depend not only on the purpose of the treated water, but also on economic considerations such as chemical doses, resin regeneration, frequency of cleaning procedures, energy, operating labor, maintenance, and capital-related items, among others. Acknowledgments The operational support provided by EPCOR Utilities Inc. and the technical feedback provided by Veolia Water Technologies are greatly appreciated. The authors also acknowledge Lockerbie Stanley Inc. for the construction and maintenance of the pilot facility. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.desal.2014.12.045.