Apr. 18, 2018 EPA Announcement

New Rulemaking Process for Blending

Today, EPA announced a new rulemaking process surrounding the use of “blending” by wastewater treatment plants. Blending is used to manage high flow events at wastewater treatment plants while maintaining compliance.

EPA announced their intent in this new process is to provide regulatory clarity and certainty with respect to the use of blending. Their goal is to help facilities optimize wastewater treatment during wet weather.

Rain and snowmelt can take Publicly Owned Treatment Works (POTWs) offline when excess water enters the wastewater collection system and exceeds the POTW’s capacity to treat all incoming wastewater. POTWs often manage excess wet weather flow by routing some of the incoming water around the secondary (biological) treatment units and then “blending” it back in with secondary treatment effluent for disinfection prior to discharge.

This, in turn, should allow an operator to avoid a possible shutdown or damage to the water treatment plant.

EPA also announced they will be reaching out to gather input prior to issuing a proposed rulemaking.

WEF will work to develop comments and engage with EPA on this rulemaking.

For more information, visit

If you have any questions, please contact WEF Senior Director Claudio Ternieden at