The Correlation Analysis And Normalized Expression Of Pollution Indexes In Coking Wastewater

The environmental problems caused by coking wastewater were standing a long time inChina. Coking wastewater is composed of many compounds with different forms andcombined-states. The transformation of every compounds in coking wastewater via treatingprocesses have a great influence on the pollution risk judgment and the choices of watertreatment processes. Aiming at these problems, the interdependent relationship of everyindexes, the composition of COD, TN, color and the rationality of the discharge standard havebeen analysed by combining the statistics data in 74 references about coking wastewatertreatment with previous works. The results showed that the water quality of cokingwastewater varied widely in different plants. TP, benzene, PAHs and Ba P were ignored innearly all coking plants and the control rates of COD and oil were only 16.67% and 28.57%.The concentration of thiocyanide, fluorinion and color were 259.37 mg/L, 135.66 mg/L and713.75 times. The detectable rates of these indexes were so high that is better to regardthiocyanide, fluorinion and color as controlling indexes. Among the references which wereinvestigated, the compositions of COD were volatile phenols(47.28%), thiocyanide(19.48%),sulfide(6.81%), cyanide(2.41%) and oil, organic amines, etc.(24.02%). The compositions ofTN were ammonia nitrogen(48.49%), organic nitrogen(35.89%), thiocyanide(12.27%),cyanide(2.35%),nitrate nitrogen and nitrite nitrogen(1%). The compositions of color weresome organics with color groups, color ionic groups and sulfide. All in all, COD, TN andcolor contain almost all components in coking wastewater. The indexes will be simplified bystandardization because contamination indexes can be grouped into three classes, which wasCOD, TN and color.Gauss normal distribution fitting was applied to some indexes whose data volume weremore than 20. The distribution of COD, BOD5, ammonia nitrogen, phenols in raw water andCOD in final effluent were accorded with normal distribution. The distribution can be areference base in coking plant in China. The distribution of cyanide showed little regulationbecause cyanide can be complexed easily. The distribution of every index showed littleregulation about the raw water being treated via biological treatment processes. The indexeswere grouped into three categories according their own characters. The concentration betweenCOD and phenols showed a linear relationship in three stages of water after normalizationprocessing, so did the concentration between ammonia nitrogen and phenols The relationshipof every indexes must be specific analyzed after normalization processing in practicalengineering.