TUTCRIS - Tampereen teknillinen yliopisto


Bioengineering optimization and microbial characterization of elemental sulfur-fueled denitrifying biofilms



TilaJulkaistu - 6 joulukuuta 2018
OKM-julkaisutyyppiG5 Artikkeliväitöskirja


Nowadays, the increasing human population and limited water resources create a demand for sustainable wastewater treatment technologies. Chemically synthesized elemental sulfur (S0)-based denitrification is an effective and cost-efficient biotechnology for nitrate (NO3-) removal from organic-deficient wastewaters. However, the hydrophobic properties of S0 limit its application for denitrification. Thus, the goal of this project is to optimize the performance and explore the treatment mechanisms of S0-fueled denitrification in biofilm systems, and the understanding of the associated microbial communities.

To address the limitation of the chemically synthesized S0-driven denitrification applications, S0 solubilization prior to S0-driven denitrification was studied in batch bioassays. The kinetic experiments showed that the achieved denitrification and denitritation rates were 20.9 and 10.7 mg N/L∙d, respectively. Microbiological analysis detected the presence of the Helicobacteraceae family onto S0 particles, that was likely responsible for the S0 solubilization. A mathematical model of microbially-catalyzed S0 hydrolysis and subsequent two-step denitrification was developed. The sensitivity analysis identified the dominance of the hydrolysis-related parameters, and suggested that microbially-catalyzed surface-based S0 hydrolysis is the rate-limiting step during S0-driven denitrification.

Autotrophic denitrification with biosulfur (ADBIOS), a by-product of biological gas desulfurization, was investigated in batch bioassays as an alternative technological solution for treating NO3- pollution in wastewaters. Denitrification and denitritation rates of 49.4 mg NO3--N/L·d and 73.0 mg NO2--N/L·d, respectively, were obtained. The Thiobacillus, Moheibacter and Thermomonas genera were dominating the ADBIOS microbial community.

Two duplicate moving-bed biofilm reactors (MBBRs) with AnoxKTM K1 (K1) and AnoxKTM Z-200 (Z-200) carriers were operated for 309 days. The effect of the nitrate loading rate on the ADBIOS performance was studied by decreasing hydraulic retention time (HRT) from 72 to 21 h. The denitrification rates of 236 and 234 mg NO3--N/L·d were achieved at an HRT of 24 h for K1 and an HRT of 21 h for Z-200 carrier, respectively. Based on RNA analysis, the same active bacteria, belonging to Thiobacillus, Truepera, Flavobacterium and Hyphomonas genera, were dominating MBBRs with K1 and Z-200 carriers.

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