Effect of hydraulic retention time on pollutant removal and sludge characteristics of multi-level A/O coupled biofilm reactor at low temperature

• Published in: Desalination and water treatment 2019-09, Vol.162, p.176-185
• Main Authors: Bian, Dejun, Nie, Zebing, Wang, Fan, Ai, Shengshu, Tian, Xi, Zhang, Li
• Format: Article
• Language: English
• Subjects: Activated sludge; Biofilm; Biological nitrogen removal; Hydraulic retention time; Low temperature
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2019.24355

The experiment used the three-level anoxic/oxic (A/O) coupled biofilm reactor as the object to investigate the effect of hydraulic retention time (HRT) on the removal of pollutants and sludge characteristics at low temperature. The low C/N value municipal wastewater was treated at the temperature was 10°C ± 1°C, the influent flow distribution ratio was 25:15:6, the total aeration was 6 L min–1, the sludge residence time was 43 ± 2 d and the sludge return ratio was 50%. The reactor was operated under three operating conditions with HRT were 12, 8 and 6 h, respectively. The results show that the denitrification effect was the best when HRT was 8 h, and the average removal rates of chemical oxygen demand, NH4+–N and total nitrogen were 85.08% ± 3.10%, 92.03% ± 4.51% and 72.02% ± 3.03%, respectively. At the same time, with the decrease of HRT, the values of sludge volume index, the contents of extracellular polymeric substances (EPS) and the values of dehydrogenises activity of the activated sludge and the EPS contents of the biofilm were increased. When the HRT was 8 h, the aerobic denitrification and aerobic simultaneous nitrification and denitrification of the coupling process were rationally utilized, so that the denitrification effect was better. The results enrich the theory of denitrification in multi-stage A/O coupling biofilm reactor under low temperature, and provide reference for engineering design and application.