Color removal from pulp and paper mill effluents — Which biological options are documented to decolorize such effluents?

Introduction / Context:
Pulp and paper mill effluents contain lignin-derived chromophores and recalcitrant organics. White-rot fungi produce extracellular oxidative enzymes (laccases, manganese peroxidase, lignin peroxidase) capable of decolorizing and transforming these compounds.

Given Data / Assumptions:

• Enzyme-mediated oxidation is key for color removal.
• Immobilization (e.g., alginate entrapment) can stabilize fungal biocatalysts.
• Nitrifiers do not target lignin chromophores.

Concept / Approach:
Trametes versicolor (syn. Coriolus versicolor) and Phanerochaete chrysosporium are model organisms for lignin degradation and effluent decolorization. Both free and immobilized forms have been reported to reduce color and COD in pulp mill wastewaters by attacking aromatic structures.

Step-by-Step Solution:

Verification / Alternative check:
Numerous studies demonstrate color reduction using these fungi in batch and continuous setups, with enzyme assays correlating activity to decolorization metrics.

Why Other Options Are Wrong:

• Nitrosomonas europaea: oxidizes ammonia; unrelated to chromophore breakdown.
• Physical sedimentation alone does not remove dissolved color-causing organics.

Common Pitfalls:
Expecting standard activated sludge to remove color efficiently; specialized oxidative systems are often needed for lignin-derived compounds.

Final Answer:
Both (a) and (b)