Determination of Chemical Oxygen Demand (COD)-A Complete Procedure (Dichromate Mercury Free Method)

MicroChem's Experiments
23 Jul 202013:20

Summary

TLDRThis video provides a comprehensive guide to measuring Chemical Oxygen Demand (COD), a crucial indicator of water and wastewater quality. It outlines the three main steps: sample and blank preparation, digestion, and absorbance measurement. Viewers are introduced to the necessary materials, including COD reagent vials and a spectrophotometer, while receiving essential safety tips. The video also highlights the significance of the COD test in assessing organic water contaminants, concluding with a practical demonstration that showcases the ease of obtaining accurate COD values.

Takeaways

  • 🔬 The Chemical Oxygen Demand (COD) test measures the quality of water and wastewater, essential for monitoring treatment efficiency.
  • 🧪 The COD test consists of three main steps: sample preparation, sample digestion, and absorbance measurement.
  • 📏 Different COD reagent vials are available: medium-range for 0-1500 mg/kg and high-range for 0-15,000 mg/kg, depending on the expected COD levels.
  • 📝 Proper labeling of vials is crucial: label the sample vial with a sample ID and the blank vial as 'blank'.
  • 🔄 When preparing the sample, ensure thorough mixing by shaking and rotating the container before transferring it to the vial.
  • 🌡️ During the digestion phase, both sample and blank vials must be heated to 150°C for two hours in a COD reactor.
  • ❄️ After digestion, allow vials to cool to room temperature without shaking to avoid turbidity, which can affect results.
  • 📊 The spectrophotometer must be calibrated and set to the appropriate method for the COD analysis based on the chosen reagent range.
  • ⚖️ The absorbance reading from the spectrophotometer provides the COD value directly, eliminating the need for further calculations.
  • 🚨 Handle hot vials with care during the mixing process, and ensure proper technique to avoid contamination or inaccuracies.

Q & A

  • What is the Chemical Oxygen Demand (COD) test used for?

    -The COD test measures the amount of oxygen required to chemically oxidize organic contaminants in water and wastewater, helping to assess water quality.

  • Why is the COD test important for water treatment plants?

    -It is used to monitor the efficiency of water treatment plants by evaluating how effectively they remove organic pollutants from wastewater.

  • What are the three main steps involved in conducting a COD test?

    -The three main steps are sample and blank preparation, sample digestion, and measuring absorbance with a spectrophotometer.

  • What equipment is necessary to perform the COD test?

    -You will need a COD reactor heater, a spectrophotometer, a micropipette, and COD reagent vials (medium-range or high-range).

  • How do you prepare the sample for the COD test?

    -Shake and mix the sample thoroughly, then transfer 2 milliliters into a labeled reagent vial, and invert the vial to mix with the reagent.

  • What is the purpose of preparing a blank vial in the COD test?

    -The blank vial is used as a control to calibrate the spectrophotometer and to ensure accurate measurement by comparing the sample against a baseline of deionized water.

  • What temperature and duration are required for the digestion phase in the COD test?

    -The vials must be digested at 150 degrees Celsius for two hours.

  • What should you do after the digestion process is complete?

    -Allow the vials to cool to 120 degrees Celsius, mix them again, and then cool them to room temperature without shaking.

  • How do you set up the spectrophotometer for reading the COD sample?

    -Turn on the spectrophotometer, calibrate it using the blank vial, and then insert the sample vial to take the measurement.

  • What does the spectrophotometer display after reading the sample vial?

    -It displays the COD value directly, indicating the amount of oxygen demand in the water sample, such as a value of 263 mg/kg.

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Water QualityCOD TestingEnvironmental ScienceLaboratory ProcedureWater TreatmentScience ExperimentEducational ContentWastewater AnalysisChemical AnalysisResearch Methodology
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