Design Considerations

Permeable reactive weir (PRW) technology is ideal for treating surface water (rivers and streams), stormwater, industrial wastewater, and agricultural waste water. PRWs can be used as temporary or permanent stormwater quality control measures (e.g., best management practices - BMPs). PRWs can also be installed within existing treatment systems that use weirs to control flow.

The following design considerations are helpful in assessing whether PRW technology will be appropriate for your project:

• Where will the PRW be installed? PRWs can be installed within rivers and streams, canals, storm sewers, and inside catch basins and other water treatment devices.
  
• What is the chemistry of the water to be treated? Physical, chemical, and biological characterization of the water is necessary to determine the proper design of the weir and filter media. These parameters include pollutants of concern, hardness, pH, temperature, conductivity, redox potential, dissolved oxygen (DO), dissolved organic carbon (DOC or fulvic acid), turbidity, and suspended sediment concentration (SSC - recommended) or total suspended solids (TSS - not recommended due to small particle bias).
  
• What is the annual hydrograph of the water body to be treated? Baseflow and stormflow data are design parameters affecting the size and shape of the weir and the hydraulic conductivity of the filter media.
• What aquatic life is present? Does the water body contain threatened or endangered species?
• What permits are required for the project? Early coordination with appropriate regulatory agencies regarding the use of PRW technology will often shorten the project timeline. There may be local or regional restrictions on the use of PRW technology in certain waterbodies (i.e., rivers containing listed species).
• What is the extent of natural debris and trash in the water to be treated? If substantial debris is present, we will provide a debris removal system upstream of the PRW.
• What is the visibility of the project side? PRWs can be colored to blend into the natural environment. We can make artistic models that are shaped like fish and can serve as river crossings for the public. In the fish design, influent enters the mouth of the fish sculpture and clean effluent exits the gills.