Assessing the effects of intra-granule precipitation in a full-scale industrial anaerobic digester

H. Feldman, X. Flores-Alsina, P. Ramin, K. Kjellberg, U. Jeppsson, D. J. Batstone, K. V. Gernaey*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


In this paper, a multi-scale model is used to assess the multiple mineral precipitation potential in a full-scale anaerobic granular sludge system. Reactor behaviour is analysed under different operational conditions (addition/no addition of reject water from dewatering of lime-stabilized biomass) and periods of time (short/long term). Model predictions suggest that a higher contribution of reject water promotes the risk of intra-granule CaCO3 formation as a result of the increased quantity of calcium arriving with that stream combined with strong pH gradients within the biofilm. The distribution of these precipitates depends on: (i) reactor height; and (ii) granule size. The study also exposes the potential undesirable effects of the long-term addition of reject water (a decrease in energy recovery of 20% over a 100-day period), caused by loss in biomass activity (due to microbial displacement), and the reduced buffer capacity. This demonstrates how both short-term and long-term operational conditions may affect the formation of precipitates within anaerobic granules, and how it may influence methane production and consequently energy recovery.
Original languageEnglish
JournalWater Science and Technology
Issue number7
Pages (from-to)1327-1337
Publication statusPublished - 2019


  • ADM1
  • Biofilm
  • Industrial wastewater
  • Multiple mineral precipitation
  • Physico-chemical modelling
  • Space competition within granules


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