Maximized Physicochemical Pretreatment for Extremely Low Biodegradability Synthetic Fiber Wastewater

Project Background

A synthetic fiber manufacturer in India encountered severe difficulties in treating its production wastewater due to extremely poor biodegradability, high emulsified oil content, and persistent color.

The customer collected a real wastewater sample and delivered it to Bluwat Chemicals’ laboratory for detailed analysis and treatability testing, aiming to identify an effective solution before full-scale implementation.

Influent Wastewater Characteristics

The raw wastewater analysis showed the following characteristics:

• TDS: 600 – 800 mg/L

• TSS: 500 – 700 mg/L

• COD: 2000 – 2500 mg/L

• BOD: < 50 mg/L

• Oil & Grease: 250 – 300 mg/L (highly emulsified)

• pH: ~4.5

The calculated BOD/COD ratio was below 0.05, clearly indicating extremely poor biodegradability and a high proportion of refractory organic compounds.

ETP Process Overview

The customer operates a 1200 KLD Effluent Treatment Plant, including screening, equalization and neutralization, cooling, DAF, biological treatment, membrane systems, RO, evaporation, and sludge dewatering.

Despite this advanced configuration, the influent wastewater posed significant challenges to the biological system due to its poor biodegradability and high oil loading.

Bluwat’s Technical Strategy: Maximizing Pretreatment Performance

Bluwat’s technical team proposed a physicochemical pretreatment strategy designed to maximize removal of non-biodegradable and inhibitory substances, rather than relying on biological treatment alone.

Chemical dosing was implemented directly into the DAF system via pipeline injection, using a three-step program:

Step 1 – Water Decoloring Agent

• Breaks complex dye molecules

• Destabilizes emulsified oil

• Reduces color and refractory COD

Step 2 – Polyaluminium Chloride (PAC)

• Enhances coagulation of fine suspended solids

• Improves oil–water separation efficiency

Step 3 – Polyacrylamide (PAM)

• Strengthens floc structure

• Improves flotation and sludge separation

• Reduces sludge volume

This approach ensured that physicochemical pretreatment performance was maximized before biological treatment.

Treatment Results and Technical Evaluation

After optimized pretreatment, the wastewater quality showed significant improvements in color, oil removal, and TSS reduction.
However, despite these improvements, the BOD/COD ratio remained relatively low, indicating that biodegradability was still limited.

This outcome confirmed that:

• The pretreatment system had removed most easily separable refractory components

• The remaining COD was still dominated by biologically resistant organics

Bluwat’s Engineering Recommendations

Based on the full-system evaluation, Bluwat’s technical team provided further operational recommendations:

• Increase aeration intensity in the biological tanks to enhance microbial activity

• Supplement external carbon sources to improve the BOD/COD ratio and support stable biomass growth

• Gradually optimize biological loading under controlled conditions

These recommendations aim to support biological treatment rather than overloading it, ensuring long-term stability of the ETP.

Conclusion

This case demonstrates that for extremely low-biodegradability synthetic fiber wastewater, maximizing physicochemical pretreatment is essential to protect downstream biological processes.

Bluwat’s solution focuses on:

• Removing refractory organics and emulsified oil to the greatest extent possible

• Creating the best possible conditions for biological treatment

• Providing realistic, engineering-based recommendations rather than short-term fixes

Bluwat Chemicals delivers not only chemicals, but process understanding and practical wastewater treatment solutions for complex industrial effluents.