Baihuipu Decolors Dye Printing Wastewater for Reuse
Baihuipu has decolored dye printing wastewater for a textile park in the Yangtze delta, where the print washes produced a vivid effluent that the municipal plant refused during colour inspections. The decolorization and reuse train was commissioned in May and treats 150 m3/h of mixed print and wash water. Coagulation pulls out the disperse and reactive dyes, biological treatment removes the biodegradable COD, and an activated carbon stage strips the last colour, returning over 60 percent of the flow as process water below 30 mg/L COD and barely visible colour. The park chose reuse because the colour limit left no room to expand discharge, and the reclaimed water was cheaper than the city supply it was buying.
Key Features and Benefits
Coagulation Targets the Dye First
Reactive and disperse dyes are designed to resist washing out, which is exactly why they survive biological treatment and show up in the river. A coagulation stage with the right coagulant and pH drops the colour by most of the load before the biology, because flocculating the dye and settling it is far cheaper than oxidizing every molecule. A related discussion worth reading here is Circulating Cooling Water Upgrade.
We set out the wider process route in pesticide wastewater treatment.
The coagulant dose and pH were tuned on the actual mixed print liquor, not a single dye, because the park runs a carousel of shades and the blend changes daily. The sludge from coagulation is dewatered and sent for treatment rather than allowed to re-suspend. We have written about the downstream implications separately in Baihuipu Expands Evaporation Crystallization Production.
Biology for the Biodegradable COD
After colour removal the water still carries the thickener, sizing and wash auxiliaries that are biodegradable, so a biological stage takes the COD down before the polishing step. The culture was selected to tolerate the residual surfactant load, which is what lets the reactor hold rate through the daily product changeovers. The process logic sits close to what is described in Baihuipu Upgrades Chemical Dosing and Online Monitoring, particularly on the pretreatment side.
Anoxic and aerobic zones handle the nitrogen from the auxiliaries, and the reactor is metered against the colour plant output so it is not asked to treat more than the equalization can blend. Online COD and colour surrogate readings guide the dose between laboratory checks.
Activated Carbon for the Last Trace of Colour
A granular activated carbon stage strips the residual colour and the adsorbable organics that coagulation and biology leave, taking the water from faintly tinted to clear enough for process reuse. The carbon is regenerated off site on a schedule set by the colour load, not by the calendar.
The reclaimed water returns to the print washing and the cooling circuits, and the park meters the reuse against the city supply it replaced. The discharge portion meets the colour limit with margin, which is what ended the inspection refusals.
Technical Specifications
Print wash water quality through the decolorization train:
| Parameter | Raw Print Wash | Reuse Water |
|---|---|---|
| Colour | high, vivid | barely visible |
| COD | 500 to 1,200 mg/L | below 30 mg/L |
| Suspended solids | high | below 10 mg/L |
| Surfactants | present | removed in biology |
| Reuse rate | baseline | above 60 percent of flow |
Why Choose Baihuipu as Your Manufacturer
Choosing a manufacturer here comes down to one question: who is still accountable once the commissioning team flies home. Our answer is that we build and programme our own equipment, then stand behind it for the life of the plant.
In-House Fabrication
Our Guangdong works produces everything from standard modular units to fully bespoke lines. Building in-house keeps cost, schedule and quality under our own control rather than a subcontractor's goodwill.
Experience Built the Hard Way
Since the early 2000s we have commissioned plants for food and beverage processors, chemical works, electroplaters, textile mills, mines and municipalities. The lessons that stick are scaling, fouling and sludge handling — those inform every design we issue.
Certification and Export Practice
CE marking is standard and we work to ISO 9001 procedures. Where a project calls for specific material grades, pressure vessel certification or ATEX-rated equipment, we build to that standard and ship the full documentation pack.
Complete System Responsibility
One supplier, one process guarantee. We take the plant from preliminary screening through to membrane separation, evaporation and brine management, with process, mechanical, electrical and controls engineering handled internally.
Spares, Service and Commissioning
Membranes, dosing pumps, diffusers, instrumentation and blowers are stocked for the systems we sell. Our control systems support remote diagnostics, and we can put an engineer on site for commissioning, training or an unplanned shutdown.
Let's Look at Your Numbers
Share your water analysis and site constraints and we will give you a straight assessment of the process route and the realistic operating cost before you commit to anything. Contact our engineers at WhatsApp: +86 13631765076, or find us at hkbhp.com.
WhatsApp: +86 13631765076
Customer FAQs
Why will biological treatment not remove dye colour?
Reactive and disperse dyes are engineered to resist breakdown, so they mostly pass through a bioreactor unchanged. Coagulation flocculates the dye for settling, and activated carbon adsorbs the residual colour; biology handles the biodegradable auxiliaries separately.
Can dye wastewater be reused after treatment?
Yes, once colour and COD are brought down. This train returns over 60 percent as process water for washing and cooling below 30 mg/L COD and near-clear colour, which is cheaper than buying city supply.
What happens to the dye sludge?
The coagulation sludge carrying the flocculated dye is dewatered and sent for appropriate treatment rather than discharged. It concentrates the colour off site instead of releasing it to the river.
How is the carbon regeneration timed?
By the colour load it has adsorbed, not by a fixed date. The park runs colour surrogate readings online and sends the carbon for regeneration when the breakthrough point approaches, which keeps the reuse water consistently clear. The operating detail behind this sits in tannery wastewater treatment.
For adjacent technical angles, baihuipu publishes desalination energy cost benchmark and cost control on sic and gan wastewater projects covers the same equipment from a different duty.
