Which pollutant is commonly associated with wastewater from leather tanning?

Chromium is the correct answer because it is a significant pollutant commonly found in wastewater from leather tanning processes. During tanning, chromium compounds, particularly trivalent chromium, are frequently used to preserve and enhance the durability of leather. This results in chromium being introduced into wastewater streams.

The presence of chromium in wastewater is concerning due to its potential toxicity and environmental impact. If not properly treated, chromium can contaminate water bodies, affecting aquatic life and water quality. Regulations in many jurisdictions therefore emphasize the importance of monitoring and controlling chromium levels in wastewater from tanning facilities to mitigate its harmful effects.

The other pollutants listed, while they may also be found in industrial applications, are not as prominently associated with the leather tanning process as chromium is. Thus, the identification of chromium as a key pollutant directly related to this industry underscores its significance in wastewater management practices.