Membrane concept for valorization of bicarbonate in sulfate-reduced effluent

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Bicarbonate and toxic hydrogen sulfide are generated in sulfate-reducing bacterial processes in the presence of suitable bacteria and conditions. They are often preferably eliminated from the solutions rather than utilized. However, hydrogen sulfide could be utilized for precipitation of metal products, whereas bicarbonate could be considered as a precursor for a calcium precipitation chem-ical. This study focused on the valorization of bicarbonate-containing mine water effluent from a sulfate-reducing bacterial process, called biosolution, using membrane concentration as the main technology in the concept. Concentration was found to be an essential step for the utilization of bio-solution in calcium precipitation. Good quality water was produced at the same time, for reuse or safe discharge. Biosolutions contained residual concentrations of sparingly soluble sulfides, which caused problems for membrane filtration performance. This study revealed that microfiltration to stop the biological sulfate-reducing process by removing bacteria, aeration to oxidize residual sulfides, and microfiltration to remove suspended solids were needed for sufficient pre-treatment prior to membrane concentration. Both nanofiltration and reverse osmosis worked well as a bicar-bonate concentration technology. Concentrated bicarbonate solution was then converted to effective calcium precipitation chemical by adjusting the pH, as a result of which the chemical balance favored the effective carbonate instead of the ineffective bicarbonate. This membrane concept is a step towards the closed-loop processes of the circular economy.

Original languageEnglish
Pages (from-to)117-124
Number of pages8
JournalDesalination and Water Treatment
Volume208
DOIs
Publication statusPublished - Dec 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • Bicarbonate
  • Calcium precipitation
  • Circular economy
  • Membrane concept
  • Mine water
  • Nanofiltration
  • Sulfate removal
  • Sulfide
  • Wastewater

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