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Effect of N/S ratio on anoxic thiosulfate oxidation in a fluidized bed reactor: Experimental and artificial neural network model analysis

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Original languageEnglish
Pages (from-to)171-181
JournalProcess Biochemistry
Early online date1 Jan 2018
Publication statusPublished - 2018
Publication typeA1 Journal article-refereed


Anoxic thiosulfate (S2O3 2−) oxidation using autotrophic denitrification by a mixed culture of nitrate reducing, sulfur oxidizing bacteria (NR-SOB) was studied in a fluidized bed reactor (FBR). The long-term performance of the FBR was evaluated for 306 days at three nitrogen-to-sulfur (N/S) molar ratios (0.5, 0.3 and 0.1) and a hydraulic retention time (HRT) of 5 h. S2O3 2− removal efficiencies >99% were obtained at a N/S ratio of 0.5 and a S2O3 2− and nitrate (NO3 ) loading rate of 820 (±84) mg S-S2O3 2− L−1 d−1 and 173 (±10) mg N-NO3 L−1 d−1, respectively. The S2O3 2− removal efficiency decreased to 76% and 26% at N/S ratios of 0.3 and 0.1, respectively, and recovered to 80% within 3 days after increasing the N/S ratio from 0.1 back to 0.5. The highest observed half-saturation (Ks) and inhibition (KI) constants of the biofilm-grown NR-SOB obtained from batch cultivations were 172 and 800 mg S-S2O3 2− L−1, respectively. Thiobacilus denitrificans was the dominant microorganism in the FBR. Artificial neural network modeling successfully predicted S2O3 2− and NO3 removal efficiencies and SO4 2− production in the FBR. Additionally, results from the sensitivity analysis showed that the effluent pH was the most influential parameter affecting the S2O3 2− removal efficiency.


  • Anoxic thiosulfate oxidation, Artificial neutral network, Kinetic constants, Nitrate reducing-sulfur oxidizing bacteria, Thiobacilus denitrificans

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