Effects of recirculation rate of nitrified liquor and temperature on biological nitrification–denitrification process using a trickling filter

Abstract

In the modified Ludzack–Ettinger process, high‐energy input is required in a nitrification tank. To address this issue, a new biological nitrification–denitrification system was constructed with a trickling filter for nitrification. The effects of recirculation rate of nitrified liquor and temperature through the treatment of municipal wastewater were evaluated. The highest DN removal efficiency was observed at 6.5 h of hydraulic retention in the denitrification tank and 350% of recirculation rate of nitrified liquid against the influent flow rate. The DN removal efficiencies did not reach theoretical values for all conditions tested because the COD/N ratios in the influent often decreased to less than 5 g‐COD/g‐N and temperatures dropped to less than 15°C in winter. The former inhibited the denitrification process and the latter significantly decreased the bioactivity of nitrifying bacteria. As such, this system is suitable in tropical and subtropical areas with annual minimum temperatures of over 15°C.

Modeling a Three-Stage Biological Trickling Filter Based on the A2O Process for Sewage Treatment

“…In the actual operation of urban sewage treatment plants in cold regions in winter, it was found that the activity of PAOs still exists in low-temperature environments; some inhibitory microorganisms grow rapidly, and nitrates have a strong inhibitory effect on anaerobic phosphorus release. Therefore, phosphorus removal capacity would have a certain tendency to decline under low-temperature conditions [4,52,53]. On the one hand, low temperature reduces the activity and metabolism of microorganisms in the anaerobic biological treatment process, which reduces methane production and COD removal efficiency.…”

Use of expanded polystyrene (EPS) as a support media for trickling filters applied to wastewater treatment

“…However, there is still a need for further studies that seek to increase its nitrification efficiency by effluent recirculation (Kanda et al 2016;Bressani-Ribeiro et al 2018) and to use new support media with larger specific area and low cost to replace gravel (Bressani-Ribeiro et al 2018). For this reason, several types of support media have been studied, from pall rings (Metcalf & Eddy, Inc. 2003) to alternative materials such as: corn cob, biochar, granular activated carbon, zeolites, slag, coal cinder, and tire rubber (Ali et al 2017;Forbis-Stokes et al 2018;Zhao et al 2013;Naz et al 2016).…”