Slide 4 of 52
Notes:
The filter media is incorporated into the filter bed. The three key properties of the bed are its surface area, depth, and profile. The required surface area for a filter is usually calculated based on the amount of impervious area treated and the media itself, and may vary due to regional rainfall patterns and local criteria for water quality treatment volumes. The depth of most filtering systems ranges from one to four feet. A relatively shallow filter bed is generally preferred for hydraulic and cost reasons, and because most pollutants are trapped in the top few inches of the bed. Each design also utilizes a slightly different profile through the bed. This slide illustrates the variation in sand filter profiles. Each design has slightly different surface protection and layering through the bed.