Stormwater Treatment with Permeable Reactive Weirs

Erick McWayne, Intracep Engineering, LLC
January 16, 2019

Introduction: Permeable reactive weirs (PRWs) are hollow dams that contain filter media and other water treatment equipment. Permeable reactive weirs can improve stormwater quality by removing pollutants and increasing dissolved oxygen by creating cascades. Water treatment equipment within the weir may be selected to remove a wide variety of pollutants including agrochemicals (e.g., herbicides and insecticides), heat, metals, nitrogen, phosphorus, pathogens, petroleum, salts, surfactants, suspended solids, nanoparticles, halogenated hydrocarbons, and other toxic organics.

Permeable reactive weirs may be installed in a variety of configurations including linear, labyrinth, piano key, or arched designs. These configurations may be selected to reduce upstream pool depth and improve pollutant removal efficiency. 

Powered PRWs and Remote Operation: PRWs may be connected to an electrical power source to energize water treatment equipment and performance monitoring equipment within the weir. Performance monitoring equipment may relay telemetry via wireless internet connection. The internet connection may allow remote monitoring, flow control via servo-valves, and maintenance cycling (e.g., bubble scrubbing and back flushing).

Water treatment equipment may include reactive media filters, membranes, electrocoagulators, electrodeionizers, and nontoxic chemical oxidizer generators (e.g., ozone generators). Valves on the influent ports control the water flow rate through the weir. Multiple permeable reactive weirs may be used in series to improve stormwater pollutant removal. Screened hoods and drawdown orifices may be installed on the influent ports to prevent clogging by floating debris.

Technology Scalability and Applications: Permeable reactive weirs are scalable and configurable to site conditions. PRWs may be installed within stormwater conveyance and treatment systems (i.e., best management practices [BMPs]). PRWs may be located downstream of stormwater outfalls or within storm sewer systems. PRWs may be used as weirs, level spreaders, and check dams within stormwater BMPs (shown below).

For more information on how PRWs can improve stormwater treatment, or to request a project proposal please contact Erick McWayne, at  (800) 684-6634 or

Intracep Engineering
Auburn, Washington
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