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Denitrification on poly-beta-hydroxybutyrate in microbial granular sludge sequencing batch reactor
1Division of Environmental and Water Resources Engineering, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Water Research
|May 10, 2005
Summary
Microbial granules in sequencing batch reactors (SBRs) efficiently remove carbon and nitrogen. Poly-beta-hydroxybutyric acid (PHB) can be used for denitrification, but its capacity is limited.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
- Bioreactor engineering
Background:
- Microbial granules are effective in removing organic carbon and nitrogen in sequencing batch reactors (SBRs).
- Denitrification efficiency in anaerobic phases is dependent on external carbon availability.
- Poly-beta-hydroxybutyric acid (PHB) accumulation and utilization within granules are key metabolic processes.
Purpose of the Study:
- To investigate the role and limitations of poly-beta-hydroxybutyric acid (PHB) as an internal carbon source for denitrification in microbial granules.
- To understand the interplay between organic carbon, nitrogen removal, and PHB metabolism under different operational conditions in an alternating aerobic-anaerobic SBR.
Main Methods:
- Cultivation of microbial granules in an alternating aerobic-anaerobic sequencing batch reactor (SBR).
- Monitoring of organic carbon and nitrogen removal efficiencies.
- Analysis of poly-beta-hydroxybutyric acid (PHB) accumulation and utilization.
- Controlled addition of external carbon sources and nitrate.
Main Results:
- High ammonium conversion to nitrite and nitrate occurred in the aerobic phase.
- Denitrification efficiency in the anaerobic phase was directly correlated with external carbon source availability.
- Complete denitrification was achieved with sufficient external carbon; partial denitrification occurred without it.
- In the absence of external carbon, accumulated PHB was utilized for cell maintenance and limited denitrification.
- PHB's contribution to denitrification was found to be limited, with less than 28 mg nitrate-nitrogen l(-1) denitrified using internally accumulated PHB.
Conclusions:
- The capacity of internally accumulated PHB as a reducing source for denitrification by microbial granules is limited.
- External carbon sources are crucial for achieving complete denitrification in SBRs treating nitrogenous wastewater.
- Understanding PHB metabolism is important for optimizing SBR performance in nutrient removal.