Efficient nitrogen removal and recovery from real digested sewage sludge reject water through electroconcentration

Veera Koskue, Stefano Freguia, Pablo Ledezma, Marika Kokko

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Reject waters from the dewatering of anaerobically digested municipal sewage sludge are nitrogen-rich (ca. 1 gNH4-N L−1) wastewater streams. They account for up to 25% of the total nitrogen load of wastewater treatment due to their internal recirculation within treatment plants. In this study, nitrogen was effectively removed and recovered from real reject water using a novel electrochemical setup combining electroconcentration and stripping. High nitrogen removal (≤ 94 ± 0.7%) and recovery (≤ 87 ± 8.5%) efficiencies from real reject water were obtained while simultaneously reducing the influent nitrogen concentration of 913 ± 14 mgNH4-N L−1 to 57 ± 6.7 mgNH4-N L−1 in the effluent. Most of the nitrogen recovery took place via electroconcentration into a liquid concentrate (≤ 82 ± 5.7%), while stripping contributed little to the removal and recovery (≤ 5 ± 2.8%). The reported removal and recovery efficiencies are the highest to date for a system utilising three-chamber electroconcentration. Furthermore, the concept of cation load ratio (the ratio between applied current density and cation loading rate) was introduced as a more precise parameter than the widely used and simpler NH4-N load ratio for predicting the performance of a (bio)electrochemical nutrient removal and recovery system.

Original languageEnglish
Article number106286
Number of pages9
JournalJournal of Environmental Chemical Engineering
Issue number5
Publication statusPublished - Oct 2021
Publication typeA1 Journal article-refereed


  • Centrate
  • Electrochemistry
  • Electroconcentration
  • Nitrogen cycle
  • Nutrient recovery
  • Nutrient removal

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Waste Management and Disposal
  • Pollution
  • Process Chemistry and Technology


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