A method to eliminate bromide interference on standard COD test for bromide-rich industrial wastewater

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Chemical oxygen demand (COD) is a critical water quality indicator.
• Bromide in industrial wastewater causes significant interference in standard COD tests.
• Existing methods for bromide interference elimination are unsatisfactory.

Purpose of the Study:

• To investigate strategies for suppressing bromide interference in COD testing.
• To evaluate the effectiveness of masking and correction methods.
• To develop a practical approach for accurate COD determination in bromide-rich samples.

Main Methods:

• Assessed silver ion for bromide masking via precipitation and complexation.
• Proposed a theoretical correction factor based on bromide's redox reaction.
• Validated the correction factor using synthetic, domestic, and industrial wastewater with varying bromide concentrations.

Main Results:

• Silver ion provided only partial masking of bromide interference.
• A theoretical correction factor of 0.1 g COD/g Br⁻ was derived.
• The correction factor proved effective for bromide concentrations up to 600 mg/L in diverse wastewater matrices.

Conclusions:

• The masking strategy with silver ion is insufficient for complete bromide interference elimination.
• The proposed correction factor offers a practical and effective solution for bromide interference in COD tests.
• This correction strategy enhances the reliability of COD measurements in bromide-containing wastewater.