Caustic Recovery & ZLD for
Textile & Dyeing Industry
Textile dyeing mills face two major effluent streams — highly alkaline mercerising washwater (8–12% NaOH) and high-TDS coloured dye bath wastewater. Rototech provides caustic recovery plants and ZLD evaporation systems that recover chemicals, reduce costs, and achieve CPCB compliance.
Textile Effluent Challenges
Caustic Soda Loss
Mercerising processes consume 8–15% NaOH solution. Wash water carrying 2–5% residual caustic is often discharged — representing both a chemical cost loss and a severe environmental violation.
High Colour & COD
Reactive and vat dyes create highly coloured wastewater (colour 5,000–20,000 Pt-Co units) with COD 3,000–15,000 mg/L that cannot meet discharge standards through biological treatment alone.
Salt-Laden Discharge
Dyeing processes use 60–100 g/L sodium sulfate or sodium chloride as exhausting agents. This high-TDS effluent (20,000–80,000 mg/L) cannot meet the CPCB ZLD requirement through conventional treatment.
Recover Caustic. Achieve Zero Discharge.
Rototech separates the two effluent streams and treats them optimally — maximising caustic NaOH recovery from mercerising wash while concentrating and drying the dye bath wastewater to achieve true ZLD.
- Stream 1 — Caustic Recovery: Triple-effect MEE concentrates dilute NaOH (2–5%) up to 18–22% for direct reuse — cutting caustic purchase by 60–80%.
- Stream 2 — Dye Bath ZLD: Forced Circulation MVR/MEE handles coloured, high-TDS dye bath effluent — colour stays in concentrate, condensate is reusable.
- Final Drying: ATFD converts the concentrated residue into a dry sodium sulfate/chloride cake with potential by-product sale value.
- Compliance: Combined system achieves CPCB ZLD norms — zero liquid discharge to drain or waterbody.
Core Technologies for Textile Industry:
Textile ZLD Questions
Can Rototech recover caustic soda from mercerising effluent?
Yes. Our Caustic Recovery Plant concentrates weak NaOH (2–5%) from mercerising washers up to 18–22% using triple-effect MEE. Recovered caustic is returned directly to the mercerising process — cutting NaOH procurement costs by 60–80% and eliminating alkaline discharge.
How is high-colour dye bath wastewater handled in the evaporator?
Colour-laden reactive dye streams can foul falling film tubes. We use Forced Circulation configurations for these streams — high slurry velocity keeps the heating surface clean. The evaporation concentrates colour and salts into a small-volume cake, while the recovered condensate is colour-free and reusable.
Is sodium sulfate recovered from textile ZLD systems saleable?
In many cases yes. When the effluent source is predominantly sodium sulfate (from sulfate-based exhausting dyes), the dried salt cake from the ATFD can meet the purity standards for recovered Glauber's salt — which has a commodity market value, offsetting some operating costs.
What CPCB/PCB regulations apply to textile dyeing effluent?
Textile units in critically polluted areas (including Surat, Tirupur, Bhilwara clusters) are mandated to achieve Zero Liquid Discharge under CPCB general conditions. The combined Caustic Recovery + MEE/MVR + ATFD system from Rototech is designed to meet these statutory ZLD requirements.
Cut Caustic Costs & Achieve Textile ZLD
Share your mercerising and dye bath effluent volumes with Rototech and receive a full caustic recovery + ZLD system proposal with payback analysis.