Which of the following is a key characteristic of a Steel Mill industrial waste?

• A. BOD and COD
• B. Color and Odor
• C. Oil & Grease and pH
• D. Temperature

Answer: (C)

Steel mill wastewaters are defined by hydrocarbon contamination from lubricants, cutting fluids, and coolants, along with processing chemicals that push the effluent to extreme acidity or basicity. Oil and grease signal the presence of hydrocarbons from metalworking fluids, making oily separations and skimming a primary treatment concern. The pH describes whether the water is strongly acidic or alkaline, which drives corrosion risk, equipment compatibility, and the need for neutralization before discharge. These two factors—oil & grease and pH—stand out as the most characteristic features of this industrial waste, more so than general measures of organic load, color/odor, or temperature, which can vary across other processes but don’t define the steel mill wastewater signature.