Induction of denitrification in a pilot-scale trickling filter by adding nitrate at high loading rate

Area of Science:

• Environmental Engineering
• Microbial Ecology
• Wastewater Treatment

Background:

• Biofilms facilitate organic matter removal through aerobic degradation and nitrification.
• Anoxic zones within biofilms enable denitrification for further organic matter removal.
• High organic loading rates can limit aerobic processes due to insufficient oxygen supply.

Purpose of the Study:

• To investigate the induction of denitrification by external nitrate addition in a highly loaded trickling filter.
• To assess the impact of induced denitrification on substrate removal capacity.
• To validate a biofilm model for describing experimental results.

Main Methods:

• A pilot-scale trickling filter was operated under high organic loading conditions.
• A pulse of nitrate was added to the filter to induce denitrification.
• Off-gas measurements (CO2, O2) and substrate removal were monitored.
• A mixed-culture biofilm model was extended and used for data analysis.

Main Results:

• Denitrification was successfully induced by nitrate addition at high loading conditions.
• A considerably increased substrate removal capacity was achieved.
• Increased CO2 production confirmed denitrification without significant changes in O2 consumption.
• The extended biofilm model accurately described the experimental outcomes.

Conclusions:

• External nitrate addition is an effective strategy to induce denitrification in biofilms.
• This approach significantly enhances the organic matter removal capacity of trickling filters.
• Mathematical modeling can effectively simulate and predict biofilm processes under varying conditions.