Immobilized-cell reactors applied to wastewater treatment offer which overall advantage compared with freely suspended-cell systems?

Introduction:
Immobilized-cell systems (biofilms, carriers, granules) are common in wastewater processes such as trickling filters, moving-bed biofilm reactors, and granular sludge reactors. Immobilization changes the hydraulics and biomass retention, which has direct implications for stability and throughput.

Given Data / Assumptions:

• Cells are attached to or entrapped within a support.
• Hydraulics allow high superficial velocities without biomass loss.
• Influent characteristics may vary over time.

Concept / Approach:
Retaining biomass on carriers increases effective biomass concentration, improving resilience to load shocks. Because cells are not washed out with effluent, systems tolerate higher dilution rates (hydraulic loading) before experiencing biomass loss. This yields more stable treatment performance compared with purely suspended systems at the same hydraulic conditions.

Step-by-Step Solution:

Verification / Alternative check:
Comparative pilot studies show higher volumetric removal rates and fewer upsets in immobilized systems at comparable loading, indicating improved washout resistance and stability.

Why Other Options Are Wrong:

• Each single advantage is true but incomplete; the comprehensive answer encompasses all.

Common Pitfalls:
Assuming immobilization solves all issues; diffusion limitations and carrier clogging can become rate-limiting if not managed.

Final Answer:
all of the above