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Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge
Published on: November 6, 2016
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Startup strategy for nitrogen removal via nitrite in a BAF system.
Jordi Gabarró1,2, Miriam Guivernau1, Laura Burgos1
1GIRO, Institute of Agrifood Research and Technology (IRTA), Torre Marimon, Caldes de Montbui, E08140, Barcelona, Catalonia, Spain.
Bioprocess and Biosystems Engineering
|October 28, 2018
Summary
This study shows that a biological aerated filter (BAF) can remove nitrogen via nitrite. Combining low empty bed contact time (EBCT) with high organic loading rate (OLR) effectively starts up BAFs for this process.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
- Nitrogen removal processes
Background:
- Biological aerated filters (BAFs) are effective for removing COD and suspended solids.
- Nitrogen removal via the nitrite pathway is an alternative to traditional nitrification-denitrification.
- Microbial activity assessment is crucial for understanding treatment performance.
Purpose of the Study:
- To determine a strategy for nitrogen removal via nitrite using a BAF pilot plant.
- To assess microbial activity using RNA/DNA analysis to support chemical results.
- To investigate the impact of empty bed contact time (EBCT) and organic loading rate (OLR) on nitrogen removal.
Main Methods:
- Operation of a two-reactor (aerobic and anoxic) BAF pilot plant.
- Monitoring of chemical oxygen demand (COD), suspended solids, nitrite, and nitrate concentrations.
- Quantitative PCR (qPCR) of the amoA gene from RNA and DNA extracts of aerobic biofilm.
- RNA/DNA analysis to assess microbial activity (Ammonia Oxidizing Bacteria - AOB).
Main Results:
- The BAF pilot plant achieved COD and suspended solids removal within 13 days.
- Nitrogen removal via nitrite was observed after 130 days with an EBCT of 0.71 h.
- Nitrite was detected in the effluent, but nitrate was consistently absent.
- qPCR confirmed the presence of AOB from the start, with activity increasing over time and stabilizing by day 124.
- Low EBCT and high OLR were identified as key factors for successful BAF startup for nitrite-based nitrogen removal.
Conclusions:
- A BAF startup strategy combining low EBCT and high OLR is feasible for nitrogen removal via nitrite.
- Ammonia oxidizing bacteria (AOB) require time and specific operational conditions to become active in BAF systems.
- The nitrite pathway offers a potential alternative for nitrogen removal in wastewater treatment.
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