Which water quality issue can be considered both a chemical and biological issue?

• A. Tastes and colors
• B. Nitrification
• C. Color
• D. E. Coli

Answer: (A)

Both chemical and biological factors can influence water quality issues, and tastes and colors are a prime example. Tastes and odors in water can come from chemical substances such as metals or organic compounds, as well as from biological activity that produces odor-causing compounds (for instance, algal blooms or microbial byproducts). Because this issue can arise from either origin, it can be considered both chemical and biological. In contrast, nitrification is a biological process driven by bacteria, E. coli is a biological contaminant, and color is typically a chemical attribute unless linked to a specific biological source, so they don’t capture the dual nature as clearly.