Study of the Aggregation Behavior of Silica and Dissolved Organic Matter in Oil Sands Produced Water Using Taguchi Experimental Design

Plant equipment fouling is one of the major problems affecting the performance of steam assisted gravity drainage (SAGD) bitumen extraction processes. The produced water that is treated and reused as boiler feedwater contains high concentration of silica and dissolved organic matter (DOM), and silica and carbon have been found to be principle components of steam generator and heat exchanger foulants. The interactions between silica and SAGD DOM were studied in this research to provide insight into possible fouling mechanisms and mitigation methods. The effects of physicochemical process parameters such as different types of organics, salts, and colloids in the silica–DOM co-precipitation are studied at different concentrations and pHs. In order to study the effects of all physicochemical process parameters at three different levels with a minimum number of experiments, Taguchi experimental design is employed. Analysis of variance is performed to evaluate the contribution of each parameter in the silica–DOM aggregation process. The study revealed that the rate of silica organic co-precipitation varies mainly with the nature of the organics. Further, at higher ionic strength and lower pH of the solution, an enhanced silica–organic aggregation is observed. Multivalent cationic salt is found to be a good coagulating agent to remove humic-like DOM fraction from SAGD produced water.