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Effect of temperature on selenium removal from wastewater by UASB reactors
Paolo Dessì1, Rohan Jain2, Satyendra Singh3
1UNESCO-IHE, Institute for Water Education, Westvest 7, 2611AX, Delft, The Netherlands; DICAAR, Dept. of Civil-Environmental Engineering and Architecture, Piazza d'Armi, 09123, Cagliari, Italy; Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 10, FI-33720, Tampere, Finland.
Water Research
|March 4, 2016
Summary
Thermophilic conditions enhance selenium removal in upflow anaerobic sludge blanket (UASB) reactors compared to mesophilic conditions. This is due to improved microbial activity and reduced biogenic elemental selenium nanoparticle formation.
Area of Science:
- Environmental microbiology
- Biotechnology
- Wastewater treatment
Background:
- Selenium contamination in wastewater poses environmental risks.
- Upflow anaerobic sludge blanket (UASB) reactors are effective for wastewater treatment.
- Temperature significantly influences microbial processes in anaerobic digestion.
Purpose of the Study:
- To investigate the effect of temperature on selenium removal efficiency in UASB reactors.
- To compare the performance of thermophilic and mesophilic UASB reactors in treating selenate and nitrate-containing wastewater.
- To analyze the characteristics of biogenic elemental selenium nanoparticles (BioSeNPs) formed under different temperature conditions.
Main Methods:
- Comparison of thermophilic (55 °C) and mesophilic (30 °C) UASB reactors.
- Treatment of synthetic wastewater containing selenate and nitrate with excess lactate as an electron donor.
- Analysis of total selenium removal efficiency and effluent selenium concentrations.
- Characterization of biogenic elemental selenium nanoparticles (BioSeNPs) using microscopy.
- Microbial community analysis using molecular techniques.
Main Results:
- Thermophilic UASB reactors achieved higher total selenium removal efficiencies (94.4%) than mesophilic reactors (82.0%) when treating selenate alone.
- Under combined selenate and nitrate treatment, thermophilic reactors still showed better selenium removal (70.1%) compared to mesophilic reactors (43.6%).
- Higher effluent selenium concentrations in mesophilic reactors were attributed to increased biogenic elemental selenium nanoparticle (BioSeNPs) formation, with different shapes (nanospheres vs. nanorods).
Conclusions:
- Thermophilic operation of UASB reactors is superior for selenium removal from wastewater.
- Temperature influences the formation and characteristics of biogenic elemental selenium nanoparticles (BioSeNPs).
- The microbial community in UASB reactors includes key microorganisms for selenate respiration and denitrification.
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