Applications of high gravity technologies for wastewater treatment: A review

High gravity (Higee) has gained a great attention owing to its advantages of highly efficient mass transfer, energy saving and cost reduction. Higee technology has been studied extensively to improve mass transfer in the treatment of various wastewaters. Understanding the general theory and current status of the Higee-enhanced wastewater treatment will help with advancing this technology towards further development. In this review, the recent status of Higee development, various Higee configurations, working mechanisms of Higee technology in wastewater treatment have been introduced. The integration of Higee with other treatment technologies were described in detail, including coupling Higee with oxidants, electrolysis, advanced oxidation processes (AOPs), stripping, ozonation, electrochemical processes, photocatalytic oxidation, adsorption, or extraction. The effects of operating factors on the Higee coupled treatment systems were discussed with respect to the treatment efficiency, cost and facility. To move Higee technology towards practical applications, there is a need for improving the understanding of fundamental theories, investigation of residence time distribution, and more pilot studies of treating actual wastewater. The Higee-enhanced wastewater treatment can be promising to assist the conventional treatment with saving operational cost and improving treatment performance.