B/C is the abbreviation for the ratio of BOD5 to COD, which can indicate the biodegradability of wastewater. If CODNB represents the non biodegradable portion of COD, then the proportion of organic matter in wastewater that cannot be biodegraded by microorganisms can be represented by CODNB/COD.
When BOD5/COD ≥ 0.45, non biodegradable organic matter accounts for less than 20% of all organic matter, while when BOD5/COD ≤ 0.2, non biodegradable organic matter accounts for more than 60% of all organic matter. Therefore, BOD5/COD values are often used as evaluation indicators for the biodegradability of organic matter. If BOD5/COD ≤ 0.3, it is empirically judged that the proportion of non degradable organic matter is high. Even if a biodegradation unit is used, chemical and other pretreatment steps need to be added before the biodegradation unit to ensure that its degradation efficiency is fully utilized.
