Federal and state law require any system with a daily average flow of ___ or more to have an industrial waste ordinance (IWO) in accordance with the __ __ program.

• A. 3 mgd / national pretreatment
• B. 5 mgd / national pretreatment
• C. 5 mgd / state pretreatment
• D. 10 mgd / national pretreatment

Answer: (B)

Federal and state rules require a municipal wastewater system that treats 5 million gallons per day (mgd) or more and accepts industrial wastewater to have an industrial waste ordinance. That ordinance must align with the national pretreatment program, which provides the standard framework for regulating industrial discharges to POTWs. The 5 mgd threshold triggers the need for an IWO so industrial users can be permitted, monitored, and limited to protect treatment works and public health.

Why the other options don’t fit: the 3 mgd or 10 mgd figures aren’t the established threshold, and while some states run their own pretreatment programs, the required ordinance is specified to be in accordance with the national pretreatment program, not a different program.