What is a major environmental concern regarding heavy metals in wastewater treatment?

A primary environmental concern regarding heavy metals in wastewater treatment is the inhibition of microbial growth. Heavy metals, such as lead, mercury, cadmium, and chromium, are toxic to many forms of life, including the microorganisms that are crucial for effective wastewater treatment processes. These microorganisms play a vital role in breaking down organic pollutants and reducing biochemical oxygen demand (BOD) in the water.

When heavy metals are present in wastewater, they can disrupt microbial metabolism and growth, leading to decreased efficiency in biological treatment processes. This can result in insufficient treatment of wastewater, allowing harmful substances to remain in the effluent, which can negatively impact receiving water bodies and aquatic life.

Other options like an increase in dissolved oxygen levels, improvement of water clarity, and reduction of BOD levels do not represent major concerns associated with heavy metals. In fact, heavy metals are more likely to lead to water quality deterioration rather than any positive effects on water treatment metrics. The focus on microbial health and function illustrates why addressing heavy metal contamination is critical in environmental engineering and wastewater management.