Fast Granulation by Combining External Sludge Conditioning with FeCl₃ Addition and Reintroducing into an SBR

Area of Science:

• Environmental Engineering
• Biotechnology
• Wastewater Treatment

Background:

• Rapid granulation in sequencing batch reactors (SBRs) is crucial for efficient wastewater treatment.
• Early stages require effective sludge separation and floccular sludge aggregation.
• Current methods face challenges in optimizing these critical early-stage processes.

Purpose of the Study:

• To investigate a novel method for improving sludge separation and granulation in SBRs.
• To evaluate the impact of external sludge conditioning with FeCl3 addition on sludge properties.
• To determine the effect of reintroducing conditioned sludge on aerobic granular sludge (AGS) formation.

Main Methods:

• Effluent sludge was externally conditioned with FeCl3 addition (0.1 g Fe3+ (g dried sludge (DS))-1).
• Conditioned sludge aggregates were reintroduced into the SBR daily from day 13 to day 15.
• Sludge properties (EPS, moisture, SOUR, MLSS, SVI30) and granule size were monitored.

Main Results:

• External conditioning significantly increased extracellular polymeric substances (EPS) and sludge retention efficiency.
• Moisture content and specific oxygen uptake rate (SOUR) sharply decreased within 24h.
• Mature AGS (5.636 g/L MLSS, 45.5 mL/g SVI30, 2.5 mm diameter) were obtained by day 17.
• COD and NH4+-N removal efficiencies reached 96% and 95%, respectively.

Conclusions:

• External sludge conditioning with air-drying and Fe3+ enhances EPS production, promoting rapid aggregation and sludge retention.
• This method effectively jump-starts granulation, shortening the time to obtain mature AGS.
• The approach improves both sludge separation and pollutant removal in SBRs.