Characteristics of Coking Wastewater​ The pollutants contained in coking wastewater include phenolic compounds, polycyclic aromatic compounds, and heterocyclic compounds containing nitrogen, oxygen, and sulfur. It is a typical industrial wastewater containing refractory organic compounds.​ The easily degradable organic matter in coking wastewater mainly includes phenolic compounds and benzene compounds, while pyrrole, naphthalene, furan, and imidazole belong to degradable organic matter. The refractory organic matter mainly includes pyridine, carbazole, biphenyl, and terphenyl. The quality of coking wastewater varies greatly depending on the technological processes and production operation methods of different plants.​ The pretreatment methods before biological treatment are usually physical and chemical methods, such as air flotation, stripping, coagulation sedimentation, and breakpoint chlorination. The main purpose is to make the influent of the secondary biochemical treatment process meet the range of biodegradable treatment.

Coking wastewater is generated during coking, gas purification, and product processing. It has a wide range of sources, complex components, and high toxicity. Besides phenolic compounds, it also contains refractory heterocyclic compounds, aliphatic compounds, and polycyclic compounds; its inorganic components include cyanides, sulfides, and ammonia nitrogen, making it a type of high-concentration refractory organic wastewater.​

A large amount of wastewater containing toxic and harmful substances such as phenol, cyanide, oil, and ammonia nitrogen is discharged during the coking production process. Coking wastewater mainly comes from the coking, gas purification processes, and the refining process of chemical products, among which the residual ammonia water produced during the ammonia distillation process is the main source.​

Ammonia distillation wastewater refers to the wastewater discharged after the distillation of mixed residual ammonia water.​

Residual ammonia water is an important source of phenol-cyanide wastewater in coking plants. It is high-concentration phenol water containing ammonia, which is discharged by the circulating ammonia water pump in the condensation and blast section and sent to the residual ammonia water storage tank.​

Residual ammonia water is mainly composed of three parts:​

• The free moisture on the surface of coal charged into the coke oven;​

• The combined water generated from the dry distillation of coal charged into the coke oven;​

• The oily process wastewater added to the gas suction pipeline and the circulating ammonia water pump in the gas collector.​

The total amount of residual ammonia water can be calculated as 14% of the coal charged into the coke oven.​

After residual ammonia water is mixed in the storage tank with process wastewater from other production equipment, it is called mixed residual ammonia water.​

There are several destinations for mixed residual ammonia water: some is directly subjected to ammonia distillation; some undergoes phenol removal first before ammonia distillation; some is combined with rich ammonia water for ammonia distillation; and some is combined with desulfurization-rich liquid for acid removal and ammonia distillation. Before acid removal and ammonia distillation, filtration and oil removal must be carried out.​

Coking plants also produce some other types of wastewater, but they account for a small proportion and have relatively low pollution indicators, so they will not be introduced here.​

Characteristics of Coking Wastewater​

The pollutants contained in coking wastewater include phenolic compounds, polycyclic aromatic compounds, and heterocyclic compounds containing nitrogen, oxygen, and sulfur. It is a typical industrial wastewater containing refractory organic compounds.​

The easily degradable organic matter in coking wastewater mainly includes phenolic compounds and benzene compounds, while pyrrole, naphthalene, furan, and imidazole belong to degradable organic matter. The refractory organic matter mainly includes pyridine, carbazole, biphenyl, and terphenyl. The quality of coking wastewater varies greatly depending on the technological processes and production operation methods of different plants.​

The pretreatment methods before biological treatment are usually physical and chemical methods, such as air flotation, stripping, coagulation sedimentation, and breakpoint chlorination. The main purpose is to make the influent of the secondary biochemical treatment process meet the range of biodegradable treatment.