Coagulation, precipitation process is involved with which of the following?

• A. Suspended solids removal
• B. Common metal removal
• C. Nitrification
• D. Biochemical oxygen demand reduction

Answer: (B)

Coagulation and precipitation target dissolved metals by turning them into insoluble solid forms. When coagulants are added, metals and metal complexes are destabilized and, with the right pH, form metal hydroxide precipitates (for example, Fe(OH)3, Al(OH)3, or other metal hydroxides). These precipitates are then removed by sedimentation or filtration. This makes the process especially effective for removing common metals from water or wastewater, such as iron, manganese, copper, chromium, and others.

Nitrification is a biological process that oxidizes ammonia to nitrate, not something driven by coagulation or precipitation. Reducing biochemical oxygen demand (BOD) involves biological degradation of organic matter, which again is not the primary goal of coagulation/precipitation. While coagulation can help with very fine suspended solids, the scenario described is most closely associated with metal removal via precipitation.