The concept of load ratio applied to bioelectrochemical systems for ammonia recovery

Mariana Rodríguez Arredondo, Philipp Kuntke, Annemiek ter Heijne*, Cees J.N. Buisman

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

16 Citations (Scopus)


BACKGROUND: The load ratio is a crucial parameter to optimize the current driven recovery of total ammonia nitrogen (TAN) from urine. The load ratio is the ratio between the current density and the TAN loading rate. It is currently not known if the load ratio concept applies to a bioelectrochemical system (BES) because the current density and TAN loading rate cannot be controlled independently. RESULTS: We found a clear increasing trend in TAN removal efficiency with respect to load ratio in the BES for both human and synthetic urine. The maximum TAN removal efficiency was 60.9% at a load ratio of 0.7, corresponding to a TAN transport rate of 119 gN m −2 day −1 at an electrical energy input of 1.9 kWh kgN −1 (synthetic urine). Low load ratios (<1) were obtained, indicating that the current was not enough to transport all the TAN across the membrane. CONCLUSIONS: BES and ES show the same general relationship between TAN removal efficiency and load ratio. Therefore, given a stable current density, the concept of load ratio can also predict the TAN removal efficiency in BES. Higher current densities, and insights into the factors limiting current, are needed to increase the load ratio and therefore the TAN removal efficiency.

Original languageEnglish
Pages (from-to)2055-2061
JournalJournal of Chemical Technology and Biotechnology
Issue number6
Early online date5 Mar 2019
Publication statusPublished - Jun 2019


  • ammonia recovery
  • ammonia removal
  • bioelectrochemical systems
  • urine treatment


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