Abstract:
To clarify the key regulatory conditions for the long-term stable operation of Fe
3+-enhanced aerobic granular sludge (Fe-AGS) and its practical applicability in wastewater treatment, this study employed a sequencing batch reactor (SBR) to cultivate Fe-AGS. It compared the effects of continuous Fe
3+ dosing versus cessation of dosing on the Fe-AGS system, investigated the regulatory role of operational parameters on system performance, tracked long-term wastewater treatment efficacy, and validated operational stability in practical wastewater treatment. Results indicate: under continuous Fe
3+ addition, granular sludge maintains intact morphology and stable treatment performance. Upon cessation of Fe
3+ addition, granular sludge undergoes significant disintegration, with extracellular polymeric substances (EPS) content markedly decreasing to 47.98 mg/g MLSS. Removal efficiencies for ammonia nitrogen (NH
4+-N) and total nitrogen (TN) decline significantly. Regarding operational parameter control, the Fe-AGS system demonstrated good adaptability across a range of hydraulic retention times (HRT) from 3 to 8 hours, aeration intensities from 1.2 to 2.8 L/min, and idle periods from 0 to 60 minutes. Treatment performance exhibited noticeable variations, indicating that optimizing operational parameters can meet wastewater treatment efficiency requirements under different scenarios. Long-term operational stability tests demonstrated that during 300 consecutive days of simulated domestic wastewater treatment, the Fe-AGS system maintained highly efficient and stable performance, achieving 90% COD removal and 94% NH
4+-N removal. In practical wastewater trials, continuous operation over 120 days revealed excellent sludge settling properties (SVI < 55 mL/g), with NH
4+-N removal exceeding 95%, COD removal exceeding 88%, total phosphorus removal around 40%, and EPS content stabilizing at approximately 110 mg/g MLSS. In summary, continuous Fe
3+ addition is the core regulatory factor for maintaining the morphological integrity and treatment stability of Fe-AGS. Fe-AGS demonstrates promising engineering applications in practical domestic wastewater treatment and can be adapted to different treatment requirements by optimizing operational parameters.