The production of paints, coatings and pigments is a complex industrial process that involves a large number of raw materials, chemical reactions and physical processing steps. A central aspect of this industry is the treatment of the resulting wastewater, which is often highly contaminated with organic, inorganic and coloring substances. In particular, chemical-physical plants(CP plants) and chamber filter presses play a key role in the effective cleaning and treatment of this wastewater.

Processes in paint production

Paint production typically involves the following steps:

1. Raw material preparation

   • Use of pigments, binders, solvents and additives.
   • Pigments: Inorganic (e.g. titanium oxide) and organic compounds.
   • Binders: Polymers such as acrylates, alkyd resins or epoxies.

2. Mixing and dispersing

   • Uniform distribution of the pigments in the carrier liquid.
   • Use of high-performance stirrers or ball mills.
   • Formation of emulsions and suspensions.

3. Reaction and filtration

   • Chemical reactions such as polymerization or esterification.
   • Filtration to remove insoluble residues.

4. Filling

   • Finished products are filled into containers and prepared for dispatch.

Characteristics of wastewater from paint production

The wastewater from paint production is highly complex and contains the following impurities:

• Organic substances: solvents, binder residues and additives.
• Inorganic substances: pigments, heavy metals (e.g. from catalysts or dyes).
• Particles and suspended solids: Undissolved pigments and solids.
• High COD and BOD: Indicator for organic pollution.
• Color-intensive substances: Pigments and dyes that are hardly soluble in water.

Waste water treatment in paint production

The treatment of this highly contaminated wastewater requires robust and adaptable technologies. Chemical-physical plants(CP plants) and chamber filter presses are essential to effectively remove the pollutants and comply with legal discharge limits.

1. chemical-physical plants (CP plants)

How the CP system works: The CP system combines several chemical and physical processes to remove pollutants from wastewater:

• Neutralization: Adjustment of the pH value to optimize the chemical reactions. The pH value is usually adjusted to 6.5-8.5.
• Felling: Addition of Precipitants such as iron(III) chloride or aluminum sulfate for converting dissolved substances into insoluble compounds.
  • Heavy metals and phosphates are converted into poorly soluble hydroxides.
• Flocculation: Use of flocculants such as polymers to form stable flocs that are easier to separate.
• Sedimentation: settling of the flocs in a sedimentation tank or a lamella clarifier.

Advantages of the CP system:

• Flexible adaptation to different wastewater compositions.
• Effective removal of heavy metals, pigment residues and paint particles.
• Pre-treatment for downstream processes such as filtration or flotation.