What is the primary reason metal finishing wastes require chemical treatment?

Metal finishing wastes often contain various heavy metals, solvents, and other toxic substances that are resistant to biological treatment processes. Biological treatment typically relies on microorganisms to break down organic matter; however, the presence of these harmful substances can inhibit microbial activity or even lead to the death of microorganisms, making biological treatment ineffective.

Therefore, chemical treatment is necessary to effectively remove or neutralize these hazardous components before any wastewater can be safely treated further or discharged. This chemical treatment may involve precipitation, coagulation, or oxidation processes specifically designed to target and manage these resistant contaminants present in the waste.

The other options do not reflect the primary reason for treating metal finishing wastes. For example, high-temperature sensitivity is not a predominant characteristic of these wastes, nor is biological compatibility a focus since the contaminants are typically not compatible with biological processes. Lastly, the concentration of contaminants in metal finishing wastes tends to be high, not low, further necessitating the need for chemical treatment.