Performance of a sulfide-oxidizing expanded-bed reactor supplied with dissolved oxygen

Area of Science:

• Environmental biotechnology
• Biochemical engineering
• Wastewater treatment

Background:

• Sulfide oxidation is crucial for wastewater treatment.
• Conventional bioreactors face challenges with biomass retention and settling.
• Developing efficient methods for sulfide removal is essential.

Purpose of the Study:

• To evaluate a new expanded-bed bioreactor for sulfide oxidation.
• To investigate the formation and properties of sulfur sludge.
• To determine the maximum sulfide loading rates achievable.

Main Methods:

• Spatially separating liquid phase aeration from the sulfide oxidation bioreactor.
• Utilizing an expanded-bed configuration to retain sulfur sludge.
• Operating under autotrophic conditions and assessing sludge settling velocities.
• Comparing performance with conventional free-cell suspension systems.

Main Results:

• The bioreactor successfully formed well-settleable sulfur sludge (92% elemental sulfur, 2.5% biomass).
• Sludge exhibited excellent settling properties, with 90% settling above 25 m/h after 50 days.
• Achieved a maximum sulfide loading rate of 14 g HS(-) L(-1) d(-1), significantly higher than free-cell systems (6 g HS(-) L(-1) d(-1)).
• Influent supplementation with volatile fatty acids led to system deterioration due to microbial imbalances.

Conclusions:

• The new bioreactor design effectively immobilizes biomass in settleable sulfur sludge.
• Spatial separation of aeration and reaction enhances performance and settling.
• The system demonstrates superior sulfide removal capacity compared to conventional methods.
• Maintaining autotrophic conditions is critical for optimal performance.