Biological sulfide oxidation in a fluidized bed reactor

Area of Science:

• Environmental microbiology
• Biotechnology
• Chemical engineering

Background:

• Biological sulfide oxidation is key for wastewater treatment.
• Formation of well-settleable sludge is desirable for efficient solid-liquid separation.
• Fluidized bed reactors offer advantages for microbial processes.

Purpose of the Study:

• To assess the feasibility of a lab-scale fluidized bed process for biological sulfide oxidation to elemental sulfur.
• To determine the influence of operational parameters on sulfide oxidation products and sludge characteristics.
• To optimize conditions for elemental sulfur production and biogranule formation.

Main Methods:

• Laboratory-scale fluidized bed reactor experiments.
• Controlled variation of dissolved oxygen concentration, sulfide loading rate, and upflow velocity.
• Analysis of oxidation products (sulfur, sulfate) and biogranule morphology.

Main Results:

• Sulfide oxidation is highly dependent on oxygen concentration, sulfide loading rate, and upflow velocity.
• At dissolved oxygen concentrations (DOr) > 0.1 mg/l, sulfate was the main product; at DOr < 0.1 mg/l, elemental sulfur was favored.
• High sulfide conversions (>90%) achieved at loading rates of 0.13-1.6 kgS m⁻³ d⁻¹.
• Biogranules with 65-76% elemental sulfur formed at upflow velocities of 16-26 m h⁻¹ and loading rates of 0.9-1.6 kgS m⁻³ d⁻¹.

Conclusions:

• A fluidized bed process is feasible for biological sulfide oxidation to elemental sulfur and well-settleable sludge.
• Operational parameters significantly influence the product distribution and efficiency of sulfide conversion.
• Optimized conditions enable high elemental sulfur production and the formation of sulfur-rich biogranules.