Chitin and Chitosan Production Wastewater Treatment: Acid-Alkali Cycles, Protein and Salt

Chitin and chitosan are made from shrimp and crab shells in a sequence of chemical baths: acid to remove the minerals, alkali to remove the protein and to deacetylate, then washing between every step. The water that leaves is a chemical industry's effluent wearing a food industry's coat. It is acidic in places and alkaline in others, it carries dissolved shell protein at high strength, and the salt from the neutralisation of those baths is the part that shapes the treatment design. The streams are individually simple and collectively hostile, and the plant that segregates and neutralises at source ends up with a far smaller treatment plant than the one that mixes first and asks questions later.

Baths That Become Water

The demineralisation bath is hydrochloric acid in most plants, and the spent acid carries dissolved calcium carbonate from the shell along with a share of the acid itself. It is the most acidic stream in the plant.

The deproteinisation and deacetylation bath is sodium hydroxide at temperature, and the spent alkali carries dissolved protein, pigments and some of the chitin fragments that escaped. It is the strongest stream by organic load.

The washes between the baths are the volume of the plant: dilute, warm, and carrying whatever the previous bath left on the shell.

Neutralisation of the spent baths produces salt. That salt is the constraint, because it is added at the rate the chemistry demands and it leaves only in the effluent.

Segregate and Neutralise

Acid and alkali streams are collected separately and neutralised at source. Mixing them in one drain produces a salt load with no headroom and a pH that swings with the bath schedule, and the treatment plant inherits both problems.

Neutralisation at source also protects the sewer, the pipes and the operators, and it is the single most consequential choice in this industry's water design.

The segregated strong streams are then metered into the general flow over hours rather than dumped in an hour. The biology sees a diet rather than a shock.

Protein and Solids

Dissolved shell protein is removed best by coagulation. A polyelectrolyte sweep at controlled pH collapses the protein and the pigments together, and dissolved-air flotation lifts the floc out.

The removed solids are protein-rich and have value as a feed ingredient where the local market exists, which turns a disposal cost into a small credit.

Screens ahead of flotation catch the chitin fragments that escaped the baths. They are small in volume and large in consequence for the pumps.

Biology and the Salt Ceiling

After neutralisation and protein removal, the remaining carbon is modest and the salt is the question. Conventional biology works where the salt ceiling allows it, and salt-acclimatised biomass with a generous sludge age runs for years where it does not.

Where the salt is high, the biological route is limited to a polishing duty behind a membrane or evaporation step, and the design is honest about that from the start. A related discussion worth reading here is ion exchange and softener regeneration wastewater.

Removal Rates Across Our Installed Base

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.

Operators watch nitrification as the early warning. It fades first when salt creeps up, and the fade is visible in the effluent trend weeks before it is visible anywhere else. A related discussion worth reading here is Brackish Water Reverse Osmosis.

Neutralise at the bath, not at the plant. An hour of neat alkali costs days of biology, and the recovery is paid for in the consent results.

Keep the acid and alkali drains apart. One combined salt load with no headroom is the hardest thing a treatment plant can be asked to handle. For the reuse angle specifically, Snack and Convenience Food Wastewater Treatment system goes further than we can here.

Look for a salt loop before a salt treatment. A process that needs brine back is the rare case where reuse beats removal. A related discussion worth reading here is gelatin and collagen production wastewater treatment.

Why Choose Baihuipu as Your Manufacturer

Picking a supplier for this kind of plant is mostly about who carries the risk when something goes wrong. We have built this equipment for more than twenty years, and we are the ones who fabricated it, programmed the controls and will still answer the phone three years from now.

Own Factory, Real Capacity

Tanks, skids, control panels and membrane housings are built in our own Guangdong facility. Nothing critical is subcontracted, which is why we can commit to delivery dates and hold quality across a batch instead of hoping the shop floor gets it right.

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.

Two Decades of Field Data

Food and beverage, chemicals, electroplating, textile dyeing, mining, municipal work — we have commissioned across all of them. The useful part is not the project count, it is having seen how plants fail in year seven and designing those failures out.

Complete Units and Turnkey Plants

Whether you need a single package unit or a turnkey installation with civil works, we deliver the entire treatment scheme. Our engineering team covers process, mechanical, electrical and automation so one party owns the outcome.

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.

Talk to Our Engineers

Send through your raw water data and we will advise on the viable process route and realistic operating cost before you commit to anything. We can be reached on WhatsApp: +86 13631765076 or through hkbhp.com.

WhatsApp: +86 13631765076

Frequently Asked Questions

How do you handle sludge from this process?

Sludge handling is where most budgets quietly blow out. We size dewatering against realistic solids production, and we usually recommend a filter press for this duty. The disposal route — landfill, incineration, or a licensed contractor — should be confirmed before commissioning.

What does it cost to run, per cubic metre?

Energy dominates, then chemicals, then sludge disposal. We give you a per-cubic-metre breakdown during proposal so you can compare it against your sewer charge — treating too aggressively is a common and expensive mistake.

What information do you need to quote?

Water analysis for your worst-case stream, peak and average flows, discharge limits, available footprint and utilities. If you do not have a full analysis yet, we can start from a partial one and flag the gaps.

Can the plant be modified later if our production changes?

Yes, if you tell us about likely expansion up front. Leaving room in the civil works and oversizing the equalisation tank costs far less than retrofitting later. Chitin and Chitosan Production Wastewater Treatment rarely fails because of bad chemistry — it usually fails because nobody planned for the second production line.

What spare parts should we hold on site?

Critical spares are pumps, dosing valves, instrumentation sensors and any specialty media. We ship a recommended spares kit with the plant and hold stock for everything we supply, so lead times on replacements stay short.