Characteristics of coal chemical wastewater

　　The following is an introduction to the characteristics of coal chemical wastewater. The prominent characteristics of coal chemical wastewater are "four highs", namely high COD (oils, phenols), high ammonia nitrogen, high chroma, and high inorganic pollutants (sulfide, cyanide, and salt).

　　(1) Coking wastewater

　　Typical wastewater contains phenol 1000-1400mg/L, ammonia nitrogen about 2000mg/L, COD3500-6000mg/L, and cyanide 7-70mg/L. It also contains oils mainly composed of polycyclic aromatic hydrocarbons, heterocyclic compounds such as pyridine, polycyclic aromatic compounds (PAHs) such as biphenyl and naphthalene, and heterocyclic compounds containing nitrogen, oxygen, and sulfur, as well as colloidal pollutants.

　　Among the organic matter components of coking wastewater, most phenols and benzene compounds are easy to biodegrade under aerobic conditions, pyridine, furan, naphthalene and thiophene can be slowly biodegraded under anaerobic conditions, while biphenyls, indoles and quinones are difficult to biodegrade. These difficult-to-biodegrade heterocyclic compounds and polycyclic aromatic compounds are highly stable and have high biological toxicity.

　　(2) Coal gasification wastewater

　　Its characteristics are high pollutant concentration, high concentration of phenols, oil and ammonia nitrogen, many biochemical toxic and inhibitory substances, and it is difficult to achieve complete degradation of organic pollutants during biochemical treatment. It is a typical high-concentration, highly polluting, toxic and difficult-to-degrade organic industrial wastewater.

　　(3) Coal liquefaction wastewater

　　Coal liquefaction wastewater mainly includes high-concentration phenol-containing wastewater and low-concentration oil-containing wastewater. High-concentration phenol-containing wastewater mainly includes phenol-containing and sulfur-containing wastewater discharged from coal liquefaction, hydrorefining, hydrocracking and sulfur recovery devices. The characteristics of its wastewater quality are low oil content and salt ion concentration, high COD concentration, high concentrations of polycyclic aromatic hydrocarbons, benzene and its derivatives, phenol, sulfur and other toxic substances, and poor biodegradability. It is a relatively difficult wastewater to treat.