Definitions for pretreatment

• Baffle - A device used to restrain water flow.
• BMP - Best Management Practice: one of many different structural or non–structural methods used to treat runoff, including such diverse measures as ponding, street sweeping, filtration through a rain garden and infiltration to a gravel trench.
• Forebay - An artificial pool or reservoir that slows/temporarily detains flow to allow sediments and other solids to settle out. (Synonyms; sediment forebay, sediment pool, small sediment basin, impoundment, basin, storage structure, excavated pit, upfront settling basin).
• Grass swale - A vegetated channel that conveys stormwater while allowing for settling of sediments and debris (Synonyms; Vegetated waterway, grass channel, drainage ditch).
• Grease - Oil based pollutant.
• Grit - Coarse sediments such as smaller, loose particles of sand and stone or other heavy solid materials that have specific gravities or setting velocities substantially greater than those of organic particles.
• Media filter - Filtration of stormwater through a variety of different filtering materials whose purpose is to remove pollution from runoff.
• Multiple chambers - A design consisting of several, separate structures (manholes, catch basins, tanks, chambers, etc.) intended to increase pollutant removal, treat higher flow rates, or both.
• Non-proprietary Settling Device - System that is installed in stormwater sewers and that utilizes a sump to settle out sediment and other solids while also providing protection to the outlet to contain floatables, oil and grit. (Synonyms; standard sump manhole, water quality inlet, deep sump catch basins, modified catch basins).
• Off-line - Installation in which flow is diverted from the main stormwater sewer system into a device, but diverted flow is limited so that devices are not flushed during large storm events.
• Orifice - An opening structure found in forebay designs to control flow rates.
• Proprietary devices - Devices that are privately developed and owned.
• Proprietary settling device - Privately developed systems that utilize a variety of mechanisms to settle out sediments and solids. The devices are installed along stormwater sewer systems and can contain multiple chambers and use more advanced technology than non-proprietary settling devices. (Synonyms; flow through structures, vortex separator systems).
• Rhizosphere - The region of soil in the vicinity of plant roots in which the chemistry and microbiology is influenced by their growth, respiration, and nutrient exchange.
• Screening - The process of removing sediments and solids from flowing stormwater via a screen. (Synonyms; Filtering)
• Scum - A dirt or froth layer on the water surface.
• Settling - The process of removing sediments and solids by slowing the velocity of flow to allow the pollutants to settle out of the water column.
• Solids - Particulate pollutants consisting of sediments, debris and/or trash.
• Stormwater hotspot - Activities or practices that produce relatively high levels of often specific stormwater pollutants.
• Structural best management practice - A stationary and permanent BMP that is designed, constructed and operated to prevent or reduce the discharge of pollutants in stormwater.
• Vegetated filter strip - Vegetated slopes that convey stormwater as sheet flow to allow settling of sediments and solids. (Synonyms; vegetated buffer, vegetated buffer strip, grassed filter strips, grass filters).
• Vortex separator systems - A mechanism used in many proprietary settling devices that uses the circular flow within a chamber to separate solids from the stormwater. (Synonyms; swirl separators, hydrodynamic separators, swirl concentrators, flow through structures).
• Weir - A flow or water level control device, often consisting of a thin plate (sharp-crested).

Related pages

• Pretreatment selection tool
• Overview and methods of pretreatment
• Overviews for different types of pretreatment practices
  • Overview for pretreatment settling devices
  • Overview for pretreatment screens
  • Overview for pretreatment vegetated filter strips
• Information for specific types of pretreatment practices
  • Design, construction, operation and maintenance specifications for pretreatment vegetated filter strips
  • Pretreatment - Hydrodynamic separation devices
  • Pretreatment - Screening and straining devices, including forebays
  • Pretreatment - Above ground and below grade storage and settling devices
  • Pretreatment - Filtration devices and practices
  • Pretreatment - Other pretreatment water quality devices and practices

To see the above pages as a single page, link here

Pretreatment sizing for basins and filters strips

Guidance for managing sediment and wastes collected by pretreatment practices

Tables

• Pretreatment tables - link to tabled information for pretreatment practices
• Hydrodynamic separator tables
• Screening and straining devices tables
• Above ground and below grade storage and settling tables
• Filtration tables
• Other water quality devices tables

Other information and links

• Pretreatment - Additional considerations
• Case studies for pretreatment
• References for pretreatment
• Links for pretreatment
• Definitions for pretreatment
• Supporting material for pretreatment
• Photo gallery for pretreatment