[Effect of organic loading rate on granular SBR]

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Granular Sludge Systems

Context:

• Granular activated sludge sequencing batch reactors (SBRs) are widely used for wastewater treatment.
• The performance of these systems is sensitive to operational parameters, including organic loading rate.
• Understanding these sensitivities is crucial for optimizing treatment efficiency and stability.

Purpose:

• To investigate the impact of decreasing organic loading rates on the characteristics of granular sludge in SBRs.
• To evaluate the effects of reduced organic loading on pollutant removal efficiencies (COD, TP, ammonia, TN).
• To assess the influence on simultaneous nitrification and denitrification (SND) processes.

Summary:

• A gradual reduction in organic loading rate (from 1.8 to 0.67 kg/(m3 x d)) caused significant changes in granular sludge properties, including disintegration, reduced granulation, altered morphology, and increased color.
• Chemical Oxygen Demand (COD) and Total Phosphorus (TP) removal rates remained high (approx. 90% and 70%) irrespective of the loading rate.
• Simultaneous nitrification and denitrification (SND) performance was negatively affected, with ammonia and Total Nitrogen (TN) removal rates decreasing by 45% and 40%, respectively, at the lowest loading rate.

Impact:

• The study highlights the trade-offs between maintaining high nutrient removal and sludge stability in granular SBRs under varying organic loads.
• Findings indicate that while COD and TP removal are robust, nitrogen removal via SND is particularly vulnerable to reduced organic loading.
• This research provides critical insights for optimizing SBR operation to balance effluent quality and process stability in granular sludge systems.