What is the typical daily wastewater contribution per person given for sanitary sewer planning?

• A. 100 gpd
• B. 50 gpd
• C. 150 gpd
• D. 200 gpd

Answer: (A)

In sanitary sewer planning, the amount of wastewater assumed per person per day is the key figure used to size mains, laterals, and treatment capacity. For typical residential use, about 100 gallons per day per person is the standard design value. It reflects the daily water that becomes wastewater from toilets, sinks, showers, laundry, and other household activities, while staying conservative enough to cover variations in water use and future growth.

Choosing 50 gpd would understate actual use and risk undersized sewers that can't handle peak flows. Going higher, like 150 or 200 gpd, would overestimate the typical load and lead to unnecessarily oversized, more expensive infrastructure unless the community has unusually high water use or nonresidential demand.