Metal finishing industries generally produce a waste that is low in which parameter?

• A. Total Suspended Solids
• B. Biochemical Oxygen Demand
• C. pH
• D. Color

Answer: (A)

Wastewater from metal finishing is mainly an aqueous solution full of dissolved metal ions and salts rather than free-floating particles. Suspended solids are the tiny particles that stay dispersed in water, and in these processes most solids exist as dissolved species, not as particulate matter. That’s why the effluent typically has a low concentration of total suspended solids—the solids that do form are usually captured and removed during treatment as sludge, leaving the discharged water with relatively few suspended particles.

Color in these streams often comes from dissolved metal ions, not from high levels of suspended solids, and organic matter that would drive biochemical oxygen demand (BOD) is usually limited, so BOD tends to be low as well. pH can vary widely depending on the bath chemistry, so it’s not a reliable indicator of solids content.