Chemical Oxygen Demand (COD): Monitoring Water Pollution with Precision

Chemical Oxygen Demand (COD) is a fundamental parameter for assessing water and wastewater quality. It provides a fast, reliable measure of the organic and inorganic pollutants present in water, helping laboratories, industries, and environmental agencies monitor treatment efficiency, ensure regulatory compliance, and protect aquatic ecosystems.

COD quantifies the oxygen required to chemically oxidize pollutants in water. Elevated COD values indicate high levels of oxidizable substances, which can deplete dissolved oxygen, harm aquatic life, and signal inefficiencies in wastewater treatment. Its broad applicability makes COD essential for:

• Wastewater treatment monitoring – track influent and effluent quality
• Environmental surveillance – assess pollution trends in rivers, lakes, and industrial effluents
• Industrial quality control – monitor food, beverage, and chemical production processes

Reliable COD Determination

COD tests are based on chemical oxidation with strong oxidizing agents like potassium dichromate in the presence of sulfuric acid and a silver catalyst. The mixture is heated, typically to 160 °C, in sealed vials to ensure complete oxidation. Results can be measured colorimetrically (change in color intensity) or titrimetrically (quantifying remaining oxidant), expressed in mg O₂/L.

Reliable results require precise temperature control, uniform heating, and safe reagent handling, all while complying with standardized methods such as ST-COD, ISO 15705, EPA 410.4, and IRSA–CNR No. 5130.

Velp RESPIROMETRIC Sensor: Precision and Ease of Use

COD tests are based on chemical oxidation with strong oxidizing agents like potassium dichromate in the presence of sulfuric acid and a silver catalyst. The mixture is heated, typically to 160 °C, in sealed vials to ensure complete oxidation. Results can be measured colorimetrically (change in color intensity) or titrimetrically (quantifying remaining oxidant), expressed in mg O₂/L.

Reliable results require precise temperature control, uniform heating, and safe reagent handling, all while complying with standardized methods such as ST-COD, ISO 15705, EPA 410.4, and IRSA–CNR No. 5130.

Velp Solutions and Benefits for COD Analysis

ECODryBlock Dry Block Heaters provide stable, uniform heating, reaching up to 165 °C with ±0.5 °C homogeneity. Programmable temperature ramps ensure smooth, reproducible digestion—ideal for diverse environmental water matrices.

Micro Digestion Options:

• COD-W24-D160-A Block: 24 vials of 16 mm diameter for low-volume, reduced reagent analysis
• COD-W20-COMBO Block: 18 vials of 16 mm + 2 vials of 22 mm for flexible micro digestion workflows

Test Tube Digestion:

• COD-W04-D420-A Block allows simultaneous digestion of four large-volume samples (200 mL) and can be applied for wet digestion of metals and other elements in soils, sediments, and industrial samples

Digestion Units:

• DK 6, DK 20 (semi-automatic) and DKL 20 (automatic) units provide uniform heating, long-term stability, and programmable temperature ramps
• DKL 20 reduces operator workload through automation, enhancing throughput and consistency

Main benefits:

• Accurate and reproducible results thanks to stable, uniform heating
• Flexible configurations for micro or large-volume digestion
• Safe and user-friendly with sealed vials, air condensers, and PTFE accessories
• Enhanced workflow efficiency through semi-automatic or fully automatic digestion units

Ready to optimize your COD workflow?

Contact our specialists to explore how our solutions can enhance your water and wastewater analysis.