Silk Degumming Wastewater Treatment: Sericin, Soap and the Hot Alkaline Bath

A silk mill boils the raw fibre in a hot soap and soda bath to remove the sericin that holds the filament together, then rinses, dries and often dyes the result. The water it leaves is a protein effluent with an alkaline edge. The degumming bath itself is the load: hot, soapy, alkaline and rich in dissolved sericin. Rinsing carries the residual soap and alkali forward. Where the mill dyes in-house, the dye bath and its rinse add colour and chemicals. The effluent is warm, foamy and fully biodegradable, and the design that works recovers the sericin where a market exists, cools the hot streams and treats the protein as the strong carbon it is.

Where the Water Comes From

The degumming bath is the load of the plant. Hot, soapy and alkaline, it carries the sericin that has been dissolved off the fibre, and it is replaced rather than discharged in most efficient mills.

Rinsing carries the residual soap, alkali and sericin forward. It is the continuous stream of the plant and the one that sets the average load. For the reuse angle specifically, Rice Wash, Lees and the Press Water goes further than we can here.

Where the mill dyes in-house, the dye bath and its rinses add colour and fixing agents. They are intermittent, chemically different and belong in their own line. If your site also runs this kind of duty, Energy Drink Production Wastewater Treatment system covers the cost side of the decision in more depth.

Equipment and floor washing adds volume rather than load, and its contribution is the hydraulic design of the whole plant.

Sericin Recovery

Sericin is a protein, and it is recoverable. Where the local market exists for sericin powder in cosmetics or textiles, the degumming liquor is worth treating as a product stream rather than a waste stream.

Recovery is a filtration and precipitation step, not a treatment plant. A mill that recovers sericin removes most of its organic load at the source and the treatment plant becomes a formality. Where several streams need joint treatment, sour cream production wastewater treatment is the more detailed reference.

Where there is no market, the sericin goes to the biological stage. It is a strong, fully biodegradable load and the biology handles it without special equipment.

The decision is economic rather than technical. The sericin is the same material either way; the question is whether the recovered product pays for the equipment.

Soap and Alkali

The soap in the bath is what carries the sericin off the fibre, and it arrives in the rinse water as a surfactant load. Surfactants foam, and foam is the operational signature of a silk mill.

Alkali from the soda ash arrives as a pH load. It is mild compared with a mercerising stream, but it is continuous, and the equalisation tank is where it is levelled. A related discussion worth reading here is Separation, Wash and the Butterfat Line.

Foam control starts with gentle mixing in the equalisation tank. A defoamer line is standard where the tank is aerated, and the dosing is small but permanent.

Surfactants slow the settling of solids in the flotation step. The coagulant is selected with the soap load in mind, because a floc that will not sink is a floc that will not clarify. A related discussion worth reading here is Cane Sugar Mill Wastewater Treatment system.

Heat and Biology

The degumming bath runs hot, and the rinse water carries that heat forward. Biology tolerates a steady warm stream; it does not tolerate a hot slug, and the mix point is where that is decided.

Heat recovery on the bath is standard where the mill counts its steam. The recovered heat pre-warms the next bath and the treatment plant never sees the peak.

Sericin protein is a strong carbon and nitrogen source together. The biological stage is sized on the protein, and the sizing is usually smaller than operators expect because the recovery step already took most of it.

What Our Project Data Actually Shows

Across 42 commissioned plants where we hold complete COD records, influent COD ranged from 200 to 172,000 mg/L and treated effluent from 50 to 5,000 mg/L. Average removal across that set is 87.1% — not a marketing figure, but the measured mean.

That average is worth pausing on. It sits well below the 95%-plus numbers most suppliers quote, because the set includes genuinely difficult streams. On some electroplating and municipal duties the installed configuration only reaches about half the influent COD, and saying that up front is more use to you than a number the plant will never hold.

Where the mill dyes, the colour and fixing agents are the fraction that decides whether the biological stage is enough. Reactive dyes and their rinses usually are.

Treat the degumming bath as a product stream first. The sericin is worth more than the treatment it avoids.

Cool the hot streams before the tank. A warm steady feed is fine; a hot slug is not.

Size the biology on the residual load after recovery. A mill that recovers sericin has a much smaller plant than one that does not.

Why Choose Baihuipu as Your Manufacturer

Two decades in this industry teaches you that most treatment problems are procurement problems in disguise. Someone bought the cheapest skid, nobody checked the equalisation volume, and eighteen months on the plant cannot hold its consent limit. We build differently.

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.

Documentation You Can Actually Audit

Each system ships with as-built drawings, material certificates, welding records and a functional specification. If a client's own consultant wants to review the process calculation basis, we hand it over rather than treating it as proprietary.

20+ Years Across Dozens of Industries

Experience matters most when your waste stream behaves nothing like the textbook example. We have dealt with toxic organics, heavy metals, extreme salinity and refractory COD in food processing, chemical manufacturing, electroplating, mining and municipal projects.

Twenty-Plus Export Markets

We have shipped to the United States, Canada, Russia, Indonesia, India, Nigeria and Vietnam among others. Crating, export documentation and certificates are handled in-house, which keeps customs surprises to a minimum.

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.

After the Handover

Spares for everything we install are held in stock. Remote telemetry is available on most systems, and our service engineers commission, train your operators and turn out for emergencies.

Getting Started

Send us a water analysis and your production profile and we will tell you honestly what the process should look like and roughly what it costs to build and run. Reach our engineering team on WhatsApp: +86 13631765076 or via hkbhp.com.

WhatsApp: +86 13631765076

Frequently Asked Questions

How much operator attention does the system need day to day?

Automatic control handles dosing, backwash and level control. Realistically your team spends time on chemical top-up, sample testing and sludge handling — maybe one to two hours per shift on silk degumming duty, less if you opt for remote monitoring.

Can you work with our existing equipment?

Often yes. We regularly integrate into existing civil structures where the concrete is sound, replacing internals and controls rather than starting over. We will tell you honestly when legacy kit is beyond economic repair.

How long does a silk degumming system take to deliver?

Standard units ship in about 10 to 11 weeks. Custom trains with sericin recovery included run longer — plan for 15 to 23 weeks once detailed engineering starts. Site installation and wet commissioning add another few weeks.