Paint and varnish industry wastewater is highly toxic with low biodegradability. Plants produce both water-based and solvent-based paints — each with distinct effluent profiles.
Paint wastewater COD reaches 2,000-15,000 mg/L with a low BOD/COD ratio (~0.2), indicating biological treatment alone is insufficient. Heavy metals (Pb, Cd, Zn, Cu) 5-50 mg/L and solvents (toluene, xylene, MEK) 100-2,000 mg/L.
Arsistek paint sector solutions combine Fenton oxidation, chemical precipitation, air stripping, activated carbon adsorption and biological polishing. The multi-barrier approach degrades even refractory organics to meet discharge limits.
Fenton Advanced Oxidation
Fenton is among the most effective methods for degrading refractory organics in paint wastewater. H2O2 + Fe2+ generates hydroxyl radicals (•OH) that attack even the most stable molecules.
Optimum: pH 3-4, Fe2+/H2O2 ratio 1:5-1:10, reaction time 60-120 min. After reaction pH is raised to 8-9 to precipitate iron.
Fenton removes 70-90% COD in paint wastewater, enabling downstream biological treatment. It raises BOD/COD from 0.2 to 0.5-0.6.
Water-Based vs Solvent-Based
Water-based: Pigment, acrylic resin, thickener. Higher biodegradability. Color removal is the main challenge.
Solvent-based: Toluene, xylene, MEK. Air stripping + activated carbon mandatory.
Heavy Metal Precipitation
Zn, Pb, Cr, Cd come from pigments. Alkaline precipitation at pH 9-10 forms metal hydroxides.
Polymer flocculant accelerates settling. Lamella clarifier or DAF separates the precipitate.
Multi-Barrier System Design
No single method suffices for paint industry. Layered barriers are used:
- Equalization: 12-24 h buffer for pH/COD spikes
- Air stripping: Stripping column + activated carbon for volatile solvents
- Fenton AOP: Refractory organics degradation
- Neutralization: Acidic Fenton outlet adjusted to pH 7-8
- Heavy metal precipitation: Alkaline pH
- Biological polishing: Activated sludge or MBR
- GAC polishing: Final toxicity removal
Paint Sector Solution Advantages
Paint Industry References
8 images coming soon — stay tuned for our reference projects and facility photos.
Frequently Asked Questions
Paint wastewater has BOD/COD ~0.2 — most organics are non-biodegradable (refractory). Fenton hydroxyl radicals break these refractory molecules, enabling biological polishing.
After alkaline precipitation (pH 9-10): Zn < 2, Pb < 0.5, Cr < 1 mg/L. Sulfide precipitation or ion exchange for stricter limits.
2-5 kg DS/m³ from Fenton + metal precipitation. Classified as hazardous waste — licensed disposal required.
Yes, but solvent-based must first go through air stripping; otherwise volatiles poison the biological stage.
Fenton + biological usually suffices. Ozone or PAC is added for stricter color limits.
CAPEX/OPEX is 30-50% higher than standard industrial WWTP due to multi-barrier needs. Still economical vs OSB connection fees or closure penalties.