Controlling biosolids phosphorus content in enhanced biological phosphorus removal reactors

Area of Science:

• Environmental Engineering
• Environmental Chemistry
• Wastewater Treatment

Background:

• Biosolids from enhanced biological phosphorus removal (EBPR) plants often have high phosphorus content.
• Reducing phosphorus in biosolids is crucial for environmental sustainability and resource recovery.

Purpose of the Study:

• To investigate a methodology for reducing phosphorus in biosolids.
• To optimize the mixing ratios of waste activated sludge (WAS) with primary sludge or supernatant for maximum phosphate release.

Main Methods:

• Mixing phosphate-rich WAS with primary sludge or supernatant under anaerobic conditions.
• Conducting bench-scale experiments to determine optimal mixing ratios (volume and VSS/VFA).
• Analyzing phosphate release and volatile fatty acid (VFA) availability.

Main Results:

• A mixing ratio of 1:1 (volume) of WAS to primary sludge or supernatant yielded the highest phosphate release.
• Phosphate release was proportional to WAS content below 50%; VFA availability limited release above 50% WAS.
• Optimal ratios for the Nine Springs plant: 1.02 kg VSS/kg VSS (primary sludge) or 0.028 kg VFA/kg VSS (supernatant).

Conclusions:

• The proposed method can significantly reduce biosolids phosphorus content (35% with primary sludge, 32% with supernatant).
• The process is effective in releasing phosphorus from WAS for subsequent removal.
• Optimized mixing ratios are key to maximizing phosphorus reduction in wastewater treatment biosolids.