Food Wastewater Decolorization

Food-processing wastewater can be highly biodegradable while still being difficult to clarify. Fermentation residues, proteins, sugars, colloidal particles and persistent color bodies can remain stable in water, creating problems for sedimentation, filtration and downstream biological treatment.

Bluwat Chemicals evaluated samples submitted from four food-processing applications. The customer identities are anonymized, and the work described here consists of laboratory-scale treatability studies rather than guaranteed plant-scale results.

• Corn fermentation wastewater
• Soy sauce wastewater
• Soybean protein wastewater
• Xylose-processing wastewater

The samples differed significantly in appearance and treatment demand. Corn fermentation wastewater was only pale yellow, while soybean protein wastewater appeared black. Soy sauce and xylose wastewater contained more persistent color bodies and required stronger decolorization or coagulation programs.

The laboratory work focused on four connected treatment functions:

• Color destabilization: Target color-forming and colloidal substances.
• Coagulation: Aggregate suspended and colloidal particles.
• Floc enlargement: Use PAM to build stronger, more separable flocs.
• Solid-liquid separation: Produce a clarified supernatant through settling.

CUSTOMER CASE 01

Corn Fermentation Wastewater

Initial condition: pH 7; pale yellow; recorded color value 29.9.

Data note: The source record does not specify the color test method or unit.

Step	Operation	Dose / Condition	Purpose
1	Add decoloring agent	BWD-01 Water Decoloring Agent, 50 g/t	Disrupt and remove chromophoric and colloidal substances.
2	Add coagulant	Polyaluminium Chloride (PAC), 100 g/t	Destabilize suspended solids, colloids and part of the dissolved organic load.
3	Add Flocculant	C20 Cationic Polyacrylamide; dose not recorded	Bridge microflocs into larger, denser aggregates.
4	Settle	2-3 min	Complete solid-liquid separation.

Observed result: Visible floc and a clear, colorless supernatant.

Figure 1. Corn fermentation wastewater during the laboratory treatment trial.

Technical Takeaway

This sample responded to relatively low recorded doses of BWD-01 and PAC. The result should not be treated as a standard dose for all fermentation wastewater because raw materials, fermentation conditions and solids loading can substantially change demand.

CUSTOMER CASE 02

High-Color Soy Sauce Wastewater

Initial condition: Strong color; recorded color value 61.8.

Data note: The source record does not specify the color test method or unit, and the PAM dose was not recorded.

Step	Operation	Dose / Condition	Purpose
1	Add decoloring agent	BWD-01 Water Decoloring Agent, 650 g/t	Disrupt the stability of colloids and chromophoric groups.
2	Add coagulant	PAC, 2.5 kg/t	Destabilize fine suspended matter and promote aggregation.
3	Add Flocculant	Cationic Polyacrylamide; dose not recorded	Bridge destabilized particles into larger flocs.
4	Settle	2-3 min	Complete solid-liquid separation.

Observed result: A clear, slightly yellow supernatant.

Figures 2-3. Treatment sequence and clarified samples for soy sauce wastewater.

Technical Takeaway

Compared with the corn fermentation sample, the soy sauce wastewater required much higher recorded inputs of both decoloring agent and PAC. BWD-01 targeted persistent color bodies before PAC completed coagulation and floc separation.

CUSTOMER CASE 03

Black Soybean Protein Wastewater

Initial condition: pH 7; black appearance.

Step	Operation	Dose / Condition	Purpose
1	Add decoloring agent	BWD-01 Water Decoloring Agent, 250 g/t	Disrupt color bodies and initiate coagulation.
2	Add coagulant	PAC, 500 g/t	Strengthen coagulation and capture suspended matter.
3	Add flocculant	Anionic polyacrylamide, 4 g/t	Promote floc growth and accelerate settling.
4	Settle	2-3 min	Complete solid-liquid separation.

Observed result: A clear, slightly yellow supernatant with dark solids concentrated in the settled phase.

Figure 4. Soybean protein wastewater before treatment and after clarification.

Technical Takeaway

Unlike the corn fermentation and soy sauce trials, this program used anionic PAM. The comparison demonstrates that PAM charge type should be selected from actual floc performance rather than from the industry name alone.

CUSTOMER CASE 04

PAC Dose Comparison for Xylose Wastewater

Initial condition: pH 7; yellow appearance.

Test design: Three PAC doses were compared while the remaining sequence was held constant.

Trial	BWD-01 Dose	PAC Dose	Cationic PAM	Settling
A	650 g/t	750 g/t	Dose not recorded	2-3 min
B	650 g/t	1.5 kg/t	Dose not recorded	2-3 min
C	650 g/t	2.5 kg/t	Dose not recorded	2-3 min

Observed result: Separable floc and clear, slightly yellow supernatants across the three screened PAC doses.

Figure 5. Xylose wastewater treated at three PAC dose levels.

Technical Takeaway

More PAC does not automatically deliver the best overall program. The optimum dose should be selected using residual color, turbidity, floc strength, settling velocity, sludge volume and total operating cost.

• Confirm actual water quality: Test representative samples across products, shifts and cleaning cycles.
• Repeat the jar test: Evaluate several doses around the best laboratory result.
• Optimize mixing: Use rapid mixing for BWD-01 and PAC, then gentler mixing for PAM-assisted floc growth.
• Evaluate sludge handling: Measure sludge volume, settling behaviour and dewaterability.
• Conduct a controlled plant trial: Scale up gradually and monitor both pretreatment and downstream biological performance.

These four cases demonstrate that staged treatment using BWD-01 Water Decoloring Agent, PAC and PAM can improve color reduction and clarification when the products are matched to the actual wastewater. The key result is not one universal dose, but a structured method for matching decolorant, coagulant, polymer charge and addition sequence.