Pilot-scale study on an advanced Fe-Cu process for refractory wastewater pretreatment

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Refractory wastewater, characterized by extreme pH, high color, and poor biodegradability, poses significant challenges for conventional biological treatment.
• Separate discharge of acidic chemical and alkaline dyeing wastewater complicates treatment processes.

Purpose of the Study:

• To investigate and apply an advanced Fe-Cu process for pilot-scale pretreatment of refractory wastewater.
• To address the limitations of biological treatment by improving wastewater characteristics.

Main Methods:

• Utilized an advanced Fe-Cu process involving redox reactions and spontaneous coagulation for wastewater pretreatment.
• Applied the process to pilot-scale treatment of separately discharged acidic chemicals and alkaline dyeing wastewater (flow rate: 2000 m³·day⁻¹).
• Employed Fe-Cu internal electrolysis for mixed wastewater coagulation.

Main Results:

• Increased pH of acidic chemical wastewater (influent pH ~2.0) to ≥5.0.
• Achieved 10.0% chemical oxygen demand (COD) and 30.8% color removal from chemical wastewater, enhancing the BOD5/COD ratio from 0.21 to 0.38.
• Neutralized pretreated chemical wastewater for effective coagulation with alkaline dyeing wastewater, eliminating the need for additional alkaline chemicals.
• Generated average nascent Fe(II) concentrations of 925.6 mg·L⁻¹ for mixed wastewater coagulation, resulting in 70.3% color removal and 49.5% COD removal.
• Demonstrated superior COD removal and BOD5/COD enhancement compared to FeSO₄·7H₂O coagulation without secondary pollution.

Conclusions:

• The advanced Fe-Cu process is a green, effective, and easily implemented solution for refractory wastewater pretreatment.
• The process successfully addresses challenges posed by extreme pH, high color, and poor biodegradability.
• This method enhances wastewater suitability for subsequent biological treatment.