Chemical Oxygen Demand (COD) Calculator

Your details

Choose milligrams per litre for most environmental and wastewater work; grams per litre for high-strength industrial samples.
Volume of ferrous ammonium sulfate titrant consumed in the blank (reagent-only) run.
mL
Volume of FAS titrant consumed when back-titrating the sample digest. Must be less than or equal to the blank volume.
mL
Equivalent concentration of the ferrous ammonium sulfate solution. Verify this value daily against a standard potassium dichromate solution.
eq/L
Volume of the original water or wastewater sample taken for digestion.
mL
CODPrimary effluent range
212

Chemical oxygen demand - oxygen equivalent of oxidisable matter in the sample

Result unitmg O₂/L
COD (mg O₂/L)212
FAS consumed by sample (A - B)5.3
Water quality classPrimary effluent range
212 mg O₂/L
Clean / surface water<20Secondary effluent20-60Discharge limit zone60-125Primary effluent125-400Raw wastewater+400+

COD is 212.0 mg O₂/L - primary effluent range.

  • This COD level is typical of partially treated wastewater. Additional biological or chemical treatment may be needed before safe discharge.
  • A COD/BOD ratio between 1.5 and 3.0 is typical of biodegradable municipal wastewater. Ratios above 3.5 suggest significant non-biodegradable content.
  • The EU Urban Wastewater Treatment Directive sets a discharge standard of 125 mg O₂/L (COD) for treated effluent - this sample exceeds that threshold.

Next stepPair COD with BOD5 and Total Suspended Solids (TSS) measurements for a complete effluent quality picture before discharge.

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