Pretreatment for capacitive deionization: Feasibility tests using activated filter media and granule activated carbon filtration

•Novel and alternative pretreatment methods were proposed to reduce fouling in CDI•Salt removal efficiency decreased with increasing turbidity & organic matter content•Ca2+ had no noticeable effect on CDI pretreatment performance•Fe2+ and Fe3+ noticeably affected CDI electrode fouling•CDI pretreatment can be optimized as green technology to manage wastewater