Validation of a Modified Procedure for the determination of Chemical Oxygen Demand using standard dichromate method in industrial wastewater samples with high calcium chloride content

Background/ Objectives: Chemical Oxygen Demand (COD) is a widely used aggregate organic pollutant index in national discharge standards and one of the critical parameters for water quality assessment. The conventional COD determination by wet oxidative method encounters problem chloride interference samples with high content. dichromate reflux oxidizes 85-95% matter also 100% ions samples, without an appropriate masking strategy. standard cannot measure accurately containing more than 2000 mg L-1 chloride. present study demonstrates validates modified procedure industrial sample calcium content low load. Method: Petrochemical industries manufacturing Propylene Oxide Glycol via chlorohydrin route generate wastewater Due to content, analysis could not produce reliable data values known precision accuracy. based on was modified, additional mixing step specified time enhance mercuric sulphate. Undiluted (20 mL) mixed required amount sulpahte maintain 10:1 ratio 10 mL sulphuric acid at 150-175 RPM 20 minutes room temperature increase contact time/ masking. Method validation attributes were assessed found be complying acceptance criteria. Findings: We developed chemical oxygen demand rich An introduced sulphate amended resulted accurate load, modifiedmethod successfully validated. Novelty: satisfactory determining chloride-rich effluent. Keywords: (COD); Chloride interference; Modification method; Wastewater analysis; Calcium chloride; Validation