Creating the ideal environment for nitrification
As the lagoon effluent flows horizontally through the bed, the high-DO environment encourages nitrifying bacterial growth on the plentiful surface area provided by the clean stone. Influent distribution and effluent collection chambers prevent short-circuiting in the bed, and the bed itself is sized to enable full cBOD polishing as well as full nitrification, even in the cold. And to compensate for the slow nitrifier metabolism and reproduction in cold water, the SAGR’s patented Step-Feed process prebuilds and stores nitrifying bacteria while the water is warm so that they are already in place when winter comes. At the same time, the stone in the bed buffers the water temperature to prevent the cold influent from shocking the existing bacteria.
Using the patented Step-Feed process, the SAGR overcomes each of the four factors that would otherwise prevent nitrification:
- Oxygen: The stone bed is fully aerated, meaning there is plenty of dissolved oxygen for the nitrifying bacteria even in the dead of winter.
- Surface area: The clean stone is sized to optimize hydraulic conductivity as well provide ample surface area for the nitrifying bacteria to grow on.
- Competition from cBOD: SAGR beds are sized to provide cBOD polishing in addition to nitrification.
- Cold water temperatures: Because nitrifying bacteria grows much more slowly in cold water, the SAGR process prebuilds and stores nitrifying bacteria while the water is warm so that it is already in place once metabolism and reproduction slow in cold water.
How big is the SAGR?
The SAGR is designed based on a number of parameters, including loads and flows, available space, site dynamics, and more. For this reason, there are no "standard sizes" for the SAGR. In many cases it reduces the overall footprint of the lagoon system because the attached-growth environment allows for a higher concentration of helpful bacteria.
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