Metal finishing wastes are usually treated chemically because the contaminants are frequently what?

Metal finishing wastes contain various contaminants, including heavy metals, acids, and other toxic substances that can be quite harmful to biological treatment systems. These contaminants are often resistant to biological treatment processes because many of them do not easily break down or are not biodegradable by microorganisms.

Biological treatment relies on the metabolic processes of microorganisms to degrade organic materials and reduce pollutants in wastewater. However, when the contaminants are persistent and do not support microbial growth or activity, they can inhibit the effectiveness of biological processes. This resistance necessitates the use of chemical treatment methods, which can neutralize or remove these contaminants more effectively than biological systems.

Understanding the properties of the contaminants typically found in metal finishing wastes is crucial for selecting the appropriate treatment method, as relying solely on biological treatment could lead to inadequate treatment and potential environmental harm.