Simultaneous removal of silicon impurities and hardness from high-temperature heavy-oil-produced-water by chemical coagulation-assisted electrocoagulation: Performance, kinetics, optimization and operational costs

To illustrate the effectiveness and optimize the simultaneous removal of silicon impurities (SiI) and hardness from high-temperature heavy-oil-produced-water (HPW) by chemical coagulation-assisted electrocoagulation (CC-EC) process, the laboratory test was employed for revealing the performance, fitting the kinetics, analysis of the reaction process and optimization of reaction conditions, while a well operation pilot-scale test was evaluated for operational costs. As the result, after optimization the removal rate of SiI and hardness was 97.3 % and 98.4 % in laboratory test, respectively, which was better than 84.0 % and 96.0 % by traditional treatment method, respectively. The power consumption of CC-EC was not significantly increased, while the coagulant consumption was reduced by 78 % compared to the traditional treatment method. By reaction kinetics fitting with kinetic constant analysis, the synergy effect existed between CC and EC. The total operational costs of CC-EC process were 0.41 USD/m3 in the pilot-scale test, with a reduction of 34.86 % compared to the traditional treatment method. CC-EC is a reliable treatment method for HPW reclaimed, so it has strong application potential in the treatment and reclaim of oilfield produced water and similar wastewater. [Display omitted] •CC-EC can be used in removal of silicon impurities and hardness effectively at 80 ℃.•The analysis of kinetics show the synergy effect existing between CC and EC.•The suitable operation conditions for CC-EC process are revealed from optimization.•Coagulants are reduced by 78 % compared to the traditional treatment method.•Operational costs are reduced by 34.86 % compared to the traditional treatment method.