Comparing the performance and operation stability of an SBR and MBBR for single-stage nitritation-anammox treating wastewater with high organic load

Abstract

Single stage nitritation-anammox reactors have gained increasing attention for their application in municipal and industrial wastewater treatment. The most commonly used system in municipal reject water treatment is at present the sequencing batch reactor (SBR), the moving-bed biofilm reactor (MBBR) is the second most common. However, little is known about their applicability to industrial wastewaters with high C/N ratios. This study presents a comparative approach to evaluate the performance of these two systems by changing the influent from reject water (C:N ratio 1:1) stepwise to an industrial wastewater (C:N ratio 3:1). An intentionally induced temperature drop that led to nitrite accumulation was also tested. The results showed that the MBBR (1.9 kg-N m⁻³ d⁻¹) was superior to the SBR (0.5 kg-N m⁻³ d⁻¹) with at maximum up to four times higher volumetric nitrogen removal rates. Both systems accumulated nitrite (>100 mg-N L⁻¹) during the temperature drop from 30°C to as low as 18°C (MBBR) and 20°C (SBR), which subsequently resulted in almost complete loss in the removal capacities. However, the previous removal rates could be re-established in both systems within approximately 40 days. In comparison, the MBBR showed the more stable and higher performance even though higher nitrite concentrations (up to 500 mg-N L⁻¹) were encountered. Overall, MBBR operation and handling was also easier and the system was more robust to disturbances compared to the SBR.

Keywords:

• nitritation-anammox
• biofilm
• COD/N ratio
• nitrite inhibition
• temperature impact