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Application of dynamic current density for increased concentration factors and reduced energy consumption for concentrating ammonium by electrodialysis

Journal Article (2019)
Author(s)

Niels Van Linden (TU Delft - Sanitary Engineering)

H. Spanjers (TU Delft - Sanitary Engineering)

J.B. van Lier (TU Delft - Sanitary Engineering)

Research Group
Sanitary Engineering
Copyright
© 2019 N. van Linden, H. Spanjers, J.B. van Lier
DOI related publication
https://doi.org/10.1016/j.watres.2019.114856
More Info
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Publication Year
2019
Language
English
Copyright
© 2019 N. van Linden, H. Spanjers, J.B. van Lier
Research Group
Sanitary Engineering
Volume number
163
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Abstract

Ammonium (NH4+) can be recovered from water for fertiliser production or even energy production purposes. Because NH4+ recovery is more effective at increased concentrations, electrodialysis (ED) can be used to concentrate NH4+ from side streams, such as sludge reject water, and simultaneously achieve high NH4+ removal efficiencies. However, the effect of osmosis and back-diffusion increases when the NH4+ concentration gradient between the diluate and the concentrate stream increases, resulting in a limitation of the concentration factor and an increase in energy consumption for NH4+ removal. In this study, we showed that operation at dynamic current density (DCD) reduced the effect of osmosis and back-diffusion, due to a 75% decrease of the operational run time, compared to operation at a fixed current density (FCD). The concentration factor increased from 4.5 for an FCD to 6.7 for DCD, while the energy consumption of 90% NH4+ removal from synthetic sludge reject water at DCD remained stable at 5.4 MJ·kg-N−1.