1. What is Chemical Oxygen Demand?

Chemical Oxygen Demand (COD) is a measure of the amount of oxygen required to chemically oxidize organic and inorganic matter in water. It's an important water quality parameter that indicates the degree of pollution in water samples.

2. How Does the Calculator Work?

The calculator uses the COD equation:

Where:

• \( C \) — Constant (dimensionless)
• \( V_b \) — Blank volume (mL)
• \( V_s \) — Sample volume (mL)
• \( V_{sample} \) — Sample volume (mL)
• \( DF \) — Dilution factor (dimensionless)

Explanation: The equation calculates the oxygen equivalent of the organic matter in water that can be chemically oxidized.

3. Importance of COD Measurement

Details: COD is crucial for assessing water quality, monitoring wastewater treatment efficiency, and ensuring compliance with environmental regulations.

4. Using the Calculator

Tips: Enter all required values in the specified units. The constant C depends on the specific test method used. The dilution factor is 1 for undiluted samples.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between COD and BOD?
A: COD measures all chemically oxidizable matter, while BOD (Biochemical Oxygen Demand) only measures biologically oxidizable organic matter.

Q2: What are typical COD values?
A: Clean surface water: 10-50 mg/L, untreated sewage: 250-1000 mg/L, industrial wastewater: up to 100,000 mg/L.

Q3: Why use a blank in COD testing?
A: The blank accounts for any oxygen demand from the reagents themselves, ensuring accurate sample measurements.

Q4: What affects COD accuracy?
A: Sample homogeneity, reagent quality, digestion time/temperature, and presence of chloride interference.

Q5: When is dilution needed?
A: When COD exceeds the method's range (typically 0-1500 mg/L for standard methods), samples must be diluted.