Basic characteristics of coal chemical industry wastewater

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The wastewater discharged by coal chemical enterprises is mainly high-concentration gas washing wastewater, containing large amounts of toxic and harmful substances such as phenols, cyanides, oils, and ammonia nitrogen. In combined wastewater, the CODcr level is generally around 5000 mg/l, while the ammonia nitrogen level ranges from 200 to 500 mg/l. The organic pollutants present in this wastewater include phenols, polycyclic aromatic compounds, as well as heterocyclic compounds containing nitrogen, oxygen, and sulfur. It is a typical type of industrial wastewater containing difficult-to-degrade organic compounds. The readily biodegradable organic compounds in wastewater are mainly phenolic compounds and benzene compounds ； Pyrroles, naphthalenes, furans, and imidazoles belong to degradable organic compounds ； Difficult-to-degrade organic compounds mainly include pyridine, carbazole, biphenyl, terphenyl, etc. Currently, the primary technology used in China for treating coal chemical industry wastewater is biochemical treatment. This method is effective at removing phenols and benzene compounds from wastewater, but it is less effective against some difficult-to-degrade organic substances such as quinolines, indoles, pyridines, and carbazoles. As a result, the CODcr level of the wastewater discharged from this industry fails to meet the first-class standards. At the same time, coal chemical wastewater exhibits high colority and turbidity after biochemical treatment (due to the presence of various organic compounds that act as chromophores and auxochromes, such as 3-methyl-1,3,6-heptatriene, 5-norbornen-2-carboxylic acid, 2-chloro-2-norbornene, 2-hydroxybenzofuran, phenol, 1-methanesulfonyl-4-**, 3-**thiophene, naphthalene-1,8-diamine, etc.). Therefore, to treat such gasification wastewater to meet reuse or discharge standards, it is necessary to further reduce parameters such as CODcr, ammonia nitrogen, color, and turbidity.