Which consequence is a typical result of inflow and infiltration (I&I) exceeding treatment plant capacity?

• A. Sanitary Sewer Overflows (SSO)
• B. Increased aerobic tank efficiency
• C. Reduced solids generation
• D. Lower treatment costs

Answer: (A)

When inflow and infiltration push the plant beyond what it was designed to treat, the system can’t process all the wastewater going in. The excess flows overwhelm the treatment capacity, so part of the wastewater is discharged before it’s fully treated. This is known as a sanitary sewer overflow. SSOs happen when storms or groundwater infiltration swell flows so much that overflows occur at manholes, pump stations, or even the treatment plant itself, often sending untreated or partially treated wastewater into streets or nearby water bodies. That’s a direct consequence of exceeding hydraulic capacity and is a major public health and environmental concern.

Other options don’t fit because I&I doesn’t magically improve treatment efficiency or cut costs; in fact, it tends to raise hydraulic loading and can lead to bypassing or overflows rather than better performance.