Organic matter removal in a simultaneous nitrification-denitrification process using fixed-film system.

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Engineering
• Bioreactor Technology

Background:

• Swine wastewater presents significant treatment challenges due to high organic matter (OM) and nitrogen (N) loads.
• Efficient removal of OM and N is crucial for environmental protection and resource recovery.

Purpose of the Study:

• To evaluate the efficacy of two support media, polyurethane foam (R1) and polyethylene rings (R2), in an Upflow Anaerobic Sludge Blanket (UASB) reactor for swine wastewater treatment.
• To assess the contribution of biofilm and suspended biomass to OM and N removal, focusing on nitrification and denitrification processes.

Main Methods:

• UASB reactors were operated with swine wastewater using polyurethane foam (R1) and polyethylene rings (R2) as support media.
• Maximum specific nitrification (MSNA) and denitrification (MSDA) activity tests were performed on both biofilm and suspended biomass.
• Microbial diversity analysis was conducted to identify key microbial communities involved in the treatment process.

Main Results:

• The R2 system (polyethylene rings) demonstrated superior performance, achieving 77±8% OM removal and 98±4% N removal.
• Higher specific denitrifying activity (5.3±0.34 g NO3-N/g TVS∙h) was recorded in the R2 system.
• Suspended biomass accounted for at least 70% of N removal, with simultaneous nitrification and denitrification (SND) transforming 40±5% of initial N into molecular nitrogen.
• The genus Pseudomonas dominated the prokaryotic community (54.4%), indicating its significant role in the N removal process.

Conclusions:

• Polyethylene rings are a more effective support medium than polyurethane foam for OM and N removal in UASB reactors treating swine wastewater.
• Suspended biomass plays a dominant role in nitrogen removal, primarily through simultaneous nitrification and denitrification.
• The microbial community, particularly the genus Pseudomonas, is crucial for the observed nitrogen removal efficiencies.