Substrate dynamics on anammox inhibition during domestic wastewater treatment under controlled and ambient temperature

Abstract

This study investigates the kinetic behavior and operational performance of an Anammox-based Moving Bed Biofilm Reactor (MBBR) treating synthetic and real domestic wastewater under varying COD/N ratios and hydraulic retention times (HRTs). The objective was to evaluate substrate removal kinetics for total nitrogen (TN) and chemical oxygen demand (COD), assess model applicability, assess and quantify the rates of reactions and identify constraints affecting anammox activity during real domestic wastewater treatment. Three kinetic models: first-order, Grau's second-order, and modified Stover–Kincannon were applied to quantify COD and TN removal. Results showed that while the first-order model provided limited accuracy (R² = 0.36 for COD), both the Grau's model (R² > 0.98) and Stover–Kincannon model (R² > 0.98) demonstrated strong predictive performance for both COD and TN removal. The reactor achieved up to 96 % TN removal and COD removal as high as 92 %, at 24 h HRT. However, higher COD/N ratios (>8) substantially suppressed Specific Anammox Activity (SAA), with up to 92 % inhibition at COD/N = 15, especially under ambient conditions. Comparisons of performance with synthetic and real domestic wastewater further revealed the impact of environmental fluctuations and complex organics on system stability, with TN removal declining from 89 % to 82 % from controlled to ambient scenarios. The study underscores the importance of COD/N ratio management, operational flexibility, and model-guided reactor design in sustaining anammox performance. These findings offer new insights into optimizing Anammox-MBBR reactor for synthetic and real domestic wastewater treatment in decentralized wastewater treatment applications.