Typical pH of fresh domestic sewage: Which of the following best represents the usual pH range of freshly collected sewage before significant septicity sets in?

Introduction / Context:
pH influences corrosion, odor generation, and biological treatment efficiency. Fresh sewage characteristically shows a slightly alkaline reaction due to bicarbonate alkalinity and the nature of domestic wastewaters.

Given Data / Assumptions:

• Freshly collected domestic sewage (little or no septic decomposition).
• No major industrial acidic discharges.
• Ambient temperature conditions.

Concept / Approach:

Fresh sewage commonly exhibits pH in the range 7.2–8.0 (slightly alkaline). As it turns septic, pH can drop due to acid formation. Thus, for “fresh” sewage, values greater than 7 are most representative.

Step-by-Step Solution:

Verification / Alternative check:

Operational measurements at inlet works routinely record pH above 7 for municipal influents, barring unusual industrial inputs.

Why Other Options Are Wrong:

Neutral or acidic values are uncommon for fresh sewage; pH cannot be zero; very low pH would indicate unusual conditions or industrial waste.

Common Pitfalls:

Confusing septic (older) sewage with fresh; overlooking the impact of industrial waste streams.

Final Answer:

more than 7 (slightly alkaline)