[COD Requirement for Biological Phosphorus Removal Granule System Under Different Phosphorus Concentrations].

Area of Science:

• Environmental Microbiology
• Water Treatment Engineering
• Biotechnology

Background:

• Biological phosphorus removal (BPR) is crucial for wastewater treatment.
• Granular sludge systems offer advantages in BPR efficiency.
• Understanding the impact of influent parameters like COD and phosphorus is vital for optimizing BPR.

Purpose of the Study:

• To investigate the effect of chemical oxygen demand (COD) loading on biological phosphorus removal granule systems.
• To determine the minimum COD concentration required for optimal BPR performance under varying total phosphorus (TP) conditions.
• To assess the impact of COD loading on granule characteristics and effluent quality.

Main Methods:

• Experimental investigation of a biological phosphorus removal granule system.
• Manipulation of influent concentrations of total phosphorus (TP) and COD.
• Analysis of effluent phosphorus and COD concentrations.
• Characterization of granule properties including particle size, SVI, PN, and PS content.

Main Results:

• The lowest effective COD concentrations were 175 mg·L⁻¹ (at 10 mg·L⁻¹ TP) and 150 mg·L⁻¹ (at 6 mg·L⁻¹ TP).
• Effluent TP was consistently below 0.5 mg·L⁻¹, and COD removal efficiency exceeded 83%.
• Decreased COD loading led to reduced granule size, increased SVI, and deteriorated structure and performance.

Conclusions:

• Optimal COD loading is essential for maintaining the structure and performance of biological phosphorus removal granules.
• Lowering COD concentrations, particularly under high influent TP, negatively impacts BPR efficiency.
• The study provides critical insights into managing COD loading for effective wastewater phosphorus removal.