Chemical Oxygen Demand Calculator
Calculate COD for water quality assessment and wastewater treatment monitoring
Calculate Chemical Oxygen Demand
Volume of ferrous ammonium sulfate for blank run
Volume of ferrous ammonium sulfate for sample
Normality of ferrous ammonium sulfate solution
Volume of original water sample tested
COD Analysis Results
Formula: COD = (A - B) × N × 8000 / Sample Volume
Calculation: COD = (0 - 0) × 0 × 8000 / 0 = 0.0 mg/L
Assessment: Very clean water with minimal organic pollution
Typical Applications:
- •Drinking water
- •Aquaculture
- •Swimming
Example Calculation
Municipal Wastewater Sample
FAS Blank Volume (A): 30.0 mL
FAS Sample Volume (B): 12.9 mL
FAS Normality (N): 0.25 N
Sample Volume: 50.0 mL
Calculation Steps
COD = (A - B) × N × 8000 / Sample Volume
COD = (30.0 - 12.9) × 0.25 × 8000 / 50.0
COD = 17.1 × 0.25 × 8000 / 50.0
COD = 34,200 / 50.0
COD = 684 mg/L
Typical COD Values by Water Type
Drinking Water
Range: < 10 mg/L
Treated municipal water
Surface Water
Range: 5-25 mg/L
Rivers, lakes (unpolluted)
Groundwater
Range: 2-10 mg/L
Wells, springs
Swimming Pool
Range: 2-5 mg/L
Chlorinated pool water
Municipal Wastewater
Range: 200-600 mg/L
Before treatment
Industrial Wastewater
Range: 500-5000 mg/L
Food processing, chemicals
COD Quality Standards
Drinking Water
≤ 20 mg/L
WHO standard
Surface Water
5-25 mg/L
Clean rivers/lakes
Discharge Limit
≤ 125 mg/L
EU urban wastewater
Raw Sewage
200-800 mg/L
Before treatment
COD Formula
A = FAS blank volume (mL)
B = FAS sample volume (mL)
N = FAS normality
V = Sample volume (mL)
8000 = Oxygen equivalent
(mg O₂/meq)
COD vs BOD
Understanding Chemical Oxygen Demand
What is COD?
Chemical Oxygen Demand (COD) measures the amount of oxygen required to chemically oxidize organic matter in water. It's a critical parameter for assessing water quality and the effectiveness of wastewater treatment processes.
Key Applications
- •Water quality monitoring and assessment
- •Wastewater treatment efficiency evaluation
- •Industrial discharge compliance monitoring
- •Environmental impact assessment
Environmental Significance
High COD levels indicate organic pollution that can deplete dissolved oxygen in water bodies, threatening aquatic life and ecosystem health. COD testing is essential for protecting water resources and ensuring environmental sustainability.
COD Test Procedure
COD = (A - B) × N × 8000 / Sample Volume
Result in mg/L (ppm)
Test Steps
- 1. Sample Preparation: Collect representative water sample
- 2. Digestion: Heat sample with K₂Cr₂O₇ and H₂SO₄
- 3. Cooling: Allow digested sample to cool
- 4. Titration: Titrate with FAS solution
- 5. Calculation: Apply COD formula
Note: COD tests use strong oxidizing agents and should be performed in properly equipped laboratories following safety protocols.
Applications and Standards
Drinking Water
WHO recommends COD ≤ 20 mg/L for safe drinking water. Lower values indicate minimal organic contamination.
Wastewater Treatment
Monitor treatment efficiency by comparing influent and effluent COD levels. Typical removal: 80-95%.
Industrial Monitoring
Ensure compliance with discharge limits and assess impact of industrial processes on water quality.