Biotreatment of sulfate-rich wastewater in an anaerobic/micro-aerobic bioreactor system

S. H. Chuang, T. Y. Pai, R. Y. Horng

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16 Scopus citations


The focus of this study was on sulfate-rich wastewater treatment in a novel anaerobic/ micro-aerobic bioreactor system. The system was composed of an upward-flow anaerobic sludge blanket (UASB) reactor and a floated bed micro-aerobic reactor, which was packed with elastic porous carriers and was controlled in a situation of dissolved oxygen below 0.5 mg l-1. The floated bed micro-aerobic reactor was developed for accumulating a higher amount of biomass in carriers with a short hydraulic retention time (HRT) for biological oxidation of hydrogen sulfide to elemental sulfur. During long-term steady state operation, experimental results showed that an average of 70±6% of sulfate was transformed to hydrogen sulfide in UASB reactor. Moreover, the overwhelming majority of sulfide was oxidized to elemental sulfur and sulfate in micro-aerobic reactor; and the recirculation of effluent to UASB reactor reduced effectively the degree of inhibition caused by sulfate-rich wastewater. In UASB reactor, chemical oxygen demand (COD) removal efficiency increased with COD loading, in contrast, the performance of sulfate removal decreased with the increase in sulfate loading in a range of 1.0-1.75 kg SO42- m--3 d-1. In micro-aerobic reactor, sulfide was removed almost completely under the operation of HRT 2.8 h. Furthermore, experimental results of continuous operations revealed that oxidation-reduction potential (ORP) was an adequate parameter for controlling biological oxidation of sulfide. When ORP was regulated in a lower range of -250 to -300 mV, the amount of regenerated sulfate was reduced significantly in micro-aerobic reactor.

Original languageEnglish
Pages (from-to)993-1002
Number of pages10
JournalEnvironmental Technology (United Kingdom)
Issue number9
StatePublished - Sep 2005


  • Micro-aerobic
  • Oxidation-reduction potential
  • Sulfate
  • UASB
  • Wastewater


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