The removal of COD from coking wastewater using extraction replacement-biodegradation coupling

► Extraction replacement-biodegradation coupling technique was used in the experiment. ► Refractory organics in the wastewater were replaced with easily biodegraded organics. ► The most effective replacement solvent from different organic solvents was chosen. ► The optimal processing parameters were investigated. ► BOD5/CODcr and CODcr reduction efficiencies of the wastewater in SBR were improved.