What pH threshold defines acidic waste?

• A. pH < 3
• B. pH < 2
• C. pH 4
• D. pH 7

Answer: (B)

Acidity is determined by how many hydrogen ions are in solution, and pH is a log scale that runs from 0 (very acidic) to 14 (very basic), with 7 being neutral. The lower the pH, the higher the acidity and the greater the potential for corrosion and hazards in handling waste. In hazardous waste management, a strict cutoff is used: waste with pH less than 2 is considered acidic. This threshold identifies solutions that are extremely corrosive and require special handling or neutralization to protect people and the environment. Values around pH 4 are acidic but not at that extreme level, and neutral waste sits around pH 7, so they don’t meet the stricter criterion. So pH below 2 is the defining threshold for acidic waste.