What products can be used to treat dyehouse wastewater?

Dyehouse wastewater contains high concentrations of dyes, auxiliaries, heavy metals, and recalcitrant organic matter, so treatment requires a combination of methods. The following are commonly used treatment products and technical solutions:

1. Physical treatment agents

Coagulants

Polyaluminum chloride (PAC) FU5535, ferrous sulfate, and polyferric sulfate (PFS): Remove suspended solids and some color.

Polyacrylamide (PAM) FU5531G (anionic/cationic): Serves as a coagulant to enhance flocculation.

Adsorbents

Activated carbon: Highly efficient for adsorbing recalcitrant dye molecules (such as reactive dyes).

Bentonite or modified diatomaceous earth: Low-cost adsorbents suitable for pretreatment.

2. Chemical oxidants

Advanced oxidation processes (AOPs):

Fenton's reagent (H₂O₂ + Fe²⁺): Degrades organic pollutants but is pH-sensitive (requires pH ≈ 3).

Ozone (O₃): Directly oxidizes dye molecules and is suitable for advanced treatment. Persulfate (activated permonosulfate, PMS): Generates strong oxidizing free radicals through heat/UV/cobalt activation.

Sodium hypochlorite (NaClO): Suitable for decolorization, but may produce chlorinated byproducts.

3. Biological Treatment Agents

Microbial Agents

Anaerobic bacteria (e.g., hydrolytic acidifying bacteria): Decompose large organic molecules (e.g., PVA slurry).

Aerobic bacteria (e.g., activated sludge): Treat biodegradable organic matter (COD/BOD).

Specialized decolorizing bacteria (e.g., white-rot fungi): Target azo dye degradation.

Enzymes

Laccase, lignin peroxidase: Specific for the degradation of dye molecules.

4. Membrane Separation Technology

Ultrafiltration (UF) + Reverse Osmosis (RO): Advanced treatment of recycled water, but membrane fouling must be prevented.

Ceramic membranes: High-temperature, acid- and alkali-resistant, suitable for pretreatment of high-concentration dye wastewater.

5. Electrochemical Treatment

Electrocoagulation (aluminum/iron electrodes): Removes color and heavy metals. Electrocatalytic oxidation (boron-doped diamond electrode): Efficient mineralization of organic matter.

6. Recommended Combined Processes

Pretreatment: Screen → pH adjustment → Coagulation and sedimentation (PAC + PAM) → Hydrolysis and acidification.

Core treatment: Biological contact oxidation/activated sludge process → Fenton oxidation (or ozone).

Advanced treatment: Activated carbon adsorption → Membrane filtration (e.g., RO) → Standardized discharge/reuse.

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