Partial denitrification in rope-type biofilm reactors: Performance, kinetics, and microflora using internal vs....

Area of Science:

• Environmental Science
• Microbiology
• Wastewater Treatment Engineering

Background:

• Partial denitrification (PDN) is crucial for efficient anammox processes.
• Limited research exists on internal wastewater carbon sources for PDN and associated biofilm dynamics.
• Understanding biofilm community evolution and enzyme formation is key to optimizing PDN.

Purpose of the Study:

• To assess the feasibility of the PDN process using primary effluent and anaerobically pretreated wastewater as internal carbon sources.
• To investigate biofilm community evolution and functional enzyme formation in rope-type biofilm reactors.
• To compare the performance of internal carbon sources with external acetate under varying pH and biofilm thicknesses.

Main Methods:

• Rope-type biofilm media reactors were employed.
• Primary effluent and anaerobically pretreated wastewater were used as internal carbon sources.
• Acetate served as the external carbon source for comparison.
• Experiments were conducted under varied pH and biofilm thicknesses with a controlled sCOD:NO3-N ratio of 3.

Main Results:

• Internal wastewater carbon sources led to thinner biofilms but achieved modest nitrite accumulation (0.24 g/m²/d) only at elevated pH.
• The highest nitrite accumulation (0.79 g/m²/d) was observed in the acetate-fed reactor with controlled biofilm thickness.
• Acetate-fed biofilms were porous and dominated by the denitrifier Thauera, showing an imbalance in Nar, Nap, and Nir reductases.

Conclusions:

• Utilizing internal wastewater carbon sources presents a sustainable option for implementing the PDN process.
• Optimization of pH and biofilm management is necessary when using internal carbon sources for effective nitrite accumulation.
• Further research into microbial community structure and enzyme activity can enhance PDN efficiency in full-scale applications.