Typical untreated wastewater is slightly ____

• A. Neutral
• B. Alkaline
• C. Acidic
• D. Slightly acidic

Answer: (B)

Untreated wastewater usually sits around neutral to mildly alkaline because of the buffering and the chemistry of what’s in sewage. As organic matter is degraded, ammonia forms, and ammonia in water acts as a base, pushing the pH upward. The water also contains buffering species like bicarbonates that smooth out pH changes, so the overall pH tends to be slightly above 7 rather than below. That’s why “slightly alkaline” is the best fit. Neutral would be exactly pH 7, and acidic or slightly acidic implies a pH below 7, which is less typical for raw sewage.