Byline : John W. Salm, III, P.E.

Part 2
The treatment system consists of three distinct beds; the Nitrification Bed, the Denitrification Bed and the Reaeration Bed.  These beds are mixed and matched in different combinations and sizes to provide the exact, right amount of treatment required for each application.   This overlapping and reinforcing of treatment steps provides for a vigorous system which is much more reliable than single bed wetland systems.

The Nitrification Bed accepts the flow processes it downslope via shallow subsurface flow.  The water flows through several types of mineral and organic material, each with different characteristics.  In addition, the water moves through the intercalated root system of at least four types of emergent aquatic plants.  These roots help remove pollutants from the water by providing aerobic mircrosites for biochemical reactions. The Nitification Bed is very effective at removing pollutants, which may itself provide a full treatment in the warmer months. However, in the cold season when the plants are dormant, its treatment performance is more limited and, therefore, is usually followed by other treatment steps, such as the Denitrification Bed and the Reaeration Bed.

The Denitrification Bed simulates a natural swamp wetland environment.  Abundant microbiological activity occurs in the slowly moving water and in the organic surface layer.  Water is pulled through this layer and filtered prior to being discharged or redistributed to the Reaeration Bed.  At this point, most pollutants have been removed to acceptable levels.

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