Chemical oxygen demand (COD) is a measure of the oxygen equivalent of material oxidized by a specified test. COD concentration tells you how strong the wastewater is. The load tells you how much reaches the plant during a stated period.
Turn concentration into load
COD mass (kg) = volume (m³) × representative COD (mg/L) ÷ 1,000. Match the concentration and volume to the same interval. A grab sample during a batch dump describes that moment. A suitable representative sample supports the interval estimate.
- Shift A. 600 m³ × 700 mg/L ÷ 1,000 = 420 kg in 8 h.
- Shift B. 760 m³ × 900 mg/L ÷ 1,000 = 684 kg in 8 h.
- Both shifts. 1,104 kg in 1,360 m³ gives a flow-weighted COD of about 812 mg/L over 16 h.
Use EQ to read the next few hours
EQ can spread a production shock over time when capacity and mixing are available. At ET-01, 180 m³ of operating liquid volume at a steady 75 m³/h gives a nominal retention time of 2.4 h. Actual retention depends on the flow pattern and changing levels. To estimate how much extra water the tank can receive, check the free usable volume and the net filling rate. That is a separate calculation from retention time. A conversation with production before a large discharge gives the operator time to use the available buffer.
Further reading · IFC textile wastewater guidance
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