Coking waste water quantity is large, complex, containing tar, benzene, phenol, fluoride, ammonia, sulfides and other pollutants is a typical industrial waste water contains large amounts of toxic and harmful substances. Li Yijiu  the study found that by using ferric chloride as coagulants, PAM as coagulant, new compound chlorine dioxide dose SD101 catalytic oxidizers, 30C 6.5~7.0 in pH and water temperature under 3 hours, can effectively reduce the wastewater color.
Wu Dunhu  by coagulation decolorization found that pH 4. 5~6. 5、COD 6000~17000/ mg· Chromaticity 100~350 times, SS L-1, 200~6500/mg · L-1, the appearance of blue-purple ink waste water, coagulant polyferric chloride, dosage for 100/mg · Scope L-1,pH 4. 8~5.5. Coagulant for the cationic polyacrylamide, molecular weight of 15 million, ion-40, dosage 0.4/mg · L-1, the treated wastewater decolorization rate of 97.0% or more.
Because of pulping middle-stage wastewater contains a large number of difficult to degrade lignin derivatives, make it difficult for pulping middle-stage wastewater deep shade and microbial decolorization. Mo Lihuan  found that coagulation is effective method to reduce the wood pulp bleaching effluent color, but need further research and development of high efficiency and low price of coagulant, especially organic and inorganic compound high efficient coagulant deserves more attention.