What pH threshold defines alkali waste?

• A. pH 7
• B. pH > 2
• C. pH > 12.5
• D. pH 10

Answer: (C)

alkali waste is defined by a very high basicity that poses strong corrosive hazards. On the pH scale, anything above 12.5 is considered highly caustic and requires special handling and neutralization before disposal. Neutral substances sit at pH around 7, and many basic wastes are above 7, but only those above 12.5 are categorized as alkali waste in safety guidelines. A pH of 10 is basic but not sufficiently caustic, and pH thresholds like 7 or just “greater than 2” don’t distinguish highly alkaline waste. So the defining threshold is pH greater than 12.5.