Removal of Silica from in-Situ Produced Water By Electrocoagulation

Abstract

Compared to water treatment by chemical coagulation, electrocoagulation produces less sludge, leads to only a small change of pH, and can have lower operating costs. Operating costs are a combination of operating labour, electrical power and replacemnt of the consumable metal electrodes. In this study we report the performance of EC for silica removal from in-situ produced water and blowdown, including the energy and metal consumption required per unit volume of treated water, under a range of operating conditions. The use of polarity reversal to control electrode fouling is investigated, as well as some novel operating conditions. With polarity reversal, the particle size distribution of precipitated coagulant changes depending on the frequency of the reversal. At high frequency there is less electrode fouling, but the particle size formed is smaller, so separation of the solids becomes more challenging. We use laser scanning confocal microscopy with pH sensitive fluourescent dyes to observe the precipitation process occuring in the pH boundary layer at the electrode surface. This approach reveals the influence of polarity reversal and mass transport on the coagulation process.