Electrochemical wastewater treatment equipment for treating dyeing and printing wastewater.

I. Product Overview

Dyeing and printing wastewater is the most significant source of pollution in the textile industry, originating from processes such as desizing, scouring, bleaching, dyeing, printing, and finishing. It is one of the largest sources of industrial wastewater in terms of water consumption and discharge. Dyeing and printing wastewater is characterized by five major features: high concentration, high chroma, high pH, ​​recalcitrant degradation, and high variability. The wastewater has high COD, high chroma, high total solids content, and a pH value fluctuating between 5 and 10. It contains a large amount of sizing agents (polyvinyl alcohol PVA, starch, etc.), dyes (azo, anthraquinone, phthalocyanine, etc.), auxiliaries, surfactants, etc., making its composition extremely complex. The quality of wastewater varies significantly between different processes.

The treatment of dyeing and printing wastewater has long faced two core challenges: first, COD is difficult to effectively reduce—the wastewater contains a large amount of recalcitrant synthetic dyes and sizing agents, which are structurally stable and chemically inert, making conventional biological treatment ineffective; second, high-chroma wastewater is difficult to decolorize—the chromophores in dye molecules (azo bonds—N=N—, quinone groups, conjugated double bonds, etc.) are highly resistant to conventional oxidants. Traditional process routes typically follow a sequence of "grid → regulation → coagulation and sedimentation → hydrolysis and acidification → aerobic biological treatment → advanced treatment," but each stage has limitations: coagulation and sedimentation are ineffective at decolorizing water-soluble dyes; the biological treatment system has low removal rates for recalcitrant organic matter such as azo dyes; and the advanced treatment stage (Fenton/activated carbon) has high operating costs and generates large amounts of hazardous waste.

This system employs electrochemical oxidation technology, integrating multiple mechanisms of electro-oxidation degradation, electrocoagulation, and electroflotation, specifically targeting the high color, recalcitrant degradation, and high salinity characteristics of dyeing and printing wastewater: For decolorization of dyeing/printing wastewater—chromophores (azo bonds, quinone groups, conjugated double bonds, etc.) are directly oxidized and broken on the anode surface, or their conjugated structures are broken under the attack of hydroxyl radicals (·OH), achieving a color removal rate of 92%~99%, resulting in colorless and transparent effluent.

For the degradation of organic matter in desizing/scouring wastewater—PVA, starch slurry, and various auxiliaries are directly oxidized and mineralized on the anode surface. Large organic molecules break down their carbon chains, gradually decomposing into smaller organic acids and ultimately converting into CO₂ and H₂O, achieving a COD removal rate of 70%–94%.

For the resource utilization of high-salt dyeing wastewater—dyeing wastewater generally contains high concentrations of NaCl. Electrochemical methods utilize chloride ions in the wastewater to generate active chlorine, enhancing oxidation efficiency. The treated brine can be reused in the dyeing process.

The entire process consumes only electricity, without adding any chemical agents or generating large amounts of chemical sludge. The electrodes are salt-resistant and corrosion-resistant, adaptable to the complex conditions of high-salt and high-temperature (up to 60℃) dyeing wastewater, and operate safely at normal temperature and pressure.

II. Difficulties in printing and dyeing wastewater treatment and solutions of this equipment

III.Working Principle

After being screened, regulated, and settled to remove suspended solids, the dyeing and printing wastewater enters the electrochemical reactor, where it undergoes multi-mechanism synergistic purification under the action of electrodes:

(1) Direct electro-oxidation—chromophore breakage and organic mineralization (core pathway)

The chromophores of dye molecules in the dyeing and printing wastewater (azo bond—N=N—, quinone structure, conjugated double bond, aromatic ring, etc.) directly lose electrons and are oxidized on the anode surface:

Azo bond breakage: The chromophore core in the azo dye molecule is oxidized and broken, generating aromatic amine intermediates and then further mineralized.

Aromatic ring opening: The aromatic ring system of anthraquinone and triphenylmethane dyes is hydroxylated and then ring-opened on the anode surface.

Conjugated system destruction: The chromophore is oxidized and broken, resulting in the complete disappearance of color.

PVA/Starch Slurry Oxidation Chain Breaking: Polyvinyl alcohol and starch macromolecules in desizing wastewater are oxidized and broken down, gradually decomposing into small molecule organic acids and finally mineralizing into CO₂ and H₂O

(2) Indirect Electro-oxidation (dominated by ·OH and active chlorine)

Anodic electrolysis of water generates hydroxyl radicals (·OH), while utilizing the naturally occurring high concentration of chloride ions (NaCl salts) in dyeing wastewater to generate active chlorine (Cl₂, HOCl, OCl⁻):

Hydroxyl radicals indiscriminately oxidize dye molecules in the solution that have not directly contacted the anode

Active chlorine diffuses and oxidizes residual chromophores and organic matter

(3) Deep Decolorization and Disinfection

After the chromophores are completely broken down, the effluent is colorless and transparent. At the same time, the active chlorine generated by electrochemistry effectively inactivates pathogenic microorganisms in the wastewater, and the effluent microbial indicators fully meet the standards.

IV. Core Advantages (Targeting Dyeing and Printing Wastewater)

V.Technical Specifications (Customizable)

VI.Process Location

Option 1: Enhanced Pretreatment Before Biochemical Processing

Dyeing and printing wastewater (high-concentration processes such as desizing/scouring) → Bar screen/equalization tank → Electrochemical treatment equipment (COD reduction + decolorization + B/C enhancement) → Coagulation and sedimentation → Hydrolysis and acidification → Aerobic biological treatment → Discharge meeting standards

Option 2: Decolorization and Reuse of Dyeing Wastewater

High-salt dyeing wastewater → Filtration (removal of fiber debris) → Electrochemical equipment (decolorization + COD reduction + residual chlorine control) → Reuse in the dyeing process

Note: After electrochemical treatment, the high-salt wastewater generated in the dyeing process of dyeing and printing enterprises completely eliminates color and reduces COD to an acceptable level. The treated brine can be directly reused in the dyeing process.

Option 3: Deep Treatment of Biochemical Effluent

Comprehensive dyeing and printing wastewater → Pretreatment → Hydrolysis and acidification → Aerobic biological treatment → Secondary sedimentation tank → Electrochemical treatment equipment (removal of residual COD and color) → Discharge meeting standards/Reuse