Industrial wastewater microbiology — Which organism is classically associated with forming dense flocs and accumulating in factory or industrial wastes during activated-sludge treatment?

Introduction / Context:
Activated-sludge systems rely on microbial flocs that settle efficiently. Certain bacteria produce extracellular polymeric substances (EPS) that bind cells and particles into compact masses. Recognizing key floc-formers helps diagnose bulking, poor settling, and process stability issues in industrial effluent treatment.

Given Data / Assumptions:

• Industrial effluents often contain organics that foster EPS production.
• Good floc formation aids secondary clarification and effluent quality.
• Not all heterotrophs are primary floc-formers.

Concept / Approach:
Zoogloea ramigera is a classic floc-forming bacterium producing abundant EPS (zoogloeal matrix), common in activated-sludge and certain factory waste streams. While species like Pseudomonas degrade diverse organics, they are not the prototypical floc formers referenced in foundational wastewater microbiology texts.

Step-by-Step Solution:

Verification / Alternative check:
Microscopic examination of healthy sludge often reveals branched zoogloeal structures; process guides cite Z. ramigera for stable floc formation.

Why Other Options Are Wrong:

• P. aeruginosa and P. putida: versatile degraders but not the classic floc archetype.
• Thiobacillus (Acidithiobacillus): sulfur oxidizers in acidic environments.
• V. cholerae: human pathogen, not associated with activated-sludge flocs.

Common Pitfalls:
Equating high COD removal strictly with floc formation; degraders and floc-formers can be distinct guilds in the biomass.

Final Answer:
Zoogloea ramigera