Biological denitrification at low temperature in the MBBR system: a study of the effect of bioaugmentation

The removal of nitrogen in wastewater treatment systems is temperature-sensitive, with lower temperatures inhibiting the activity of nitrogen-removing bacteria. To mitigate this during cold seasons, a combined approach of bioaugmentation and mud-film symbiosis technology was applied to domestic wastewater secondary effluent. Biological agents A (nitrifying bacteria) and B (denitrifying bacteria) were introduced at 6–8 °C, with a 7-day incremental dosing regimen. The outcomes revealed significant enhancements in Total Nitrogen, NH_3–N, NO₃–N removal rates, and simultaneous nitrification–denitrification (SND) efficiency by 30.73%, 37.55%, 32.25%, and 43.69%, respectively, compared to untreated low-temperature conditions.

High-throughput sequencing analysis demonstrated an increased abundance of nitrifying and denitrifying microbial communities, including Nitromonas, Nitrobacterium, Truepera, Dechloromonas, and Unclassified Aeromycetes, in the floating biofilm and activated sludge. This augmentation of nitrogen removal capacity underscores the importance of bioaugmentation in strengthening the SND process, ensuring effective nitrogen removal in cold winter conditions for wastewater treatment systems. The findings provide valuable insights into enhancing nitrogen removal efficiency in wastewater treatment during cold periods.