Flocculant Treatment Systems

Each flocculant treatment system is designed to dose sediment laden stormwater with anionic polyacrylamide (PAM), mix and unfold the PAM molecules, settle out flocculated particles, and clarify water of suspended or floating solids prior to releasing cleaned water off-site. The specific structural components for each system are designed to meet anticipated flow rates and landscape features that are unique to each location, while adhering to the following general sequence and design criteria.

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Phase I: Dosing with Polyacrylamide

When using “Floc Logs”: turbidity laden stormwater is pumped through a sluiceway or dosing chamber, such that water flows over and around the Floc Logs at a velocity sufficient to break down and dissolve the logs into the water stream, at the desired concentration. Under ideal conditions, approximately one Floc Log for every 70 gallons of flow per minute will infuse the stormwater flow with about 10 parts per million (ppm) of polyacrylamide.  At lower water temperatures, or very high turbidity, dosing needs may vary.  

 

Phase II: Mixing and flocculant formation:

In this phase, stormwater that has been treated with PAM is slowly mixed, either by slow mechanical mixing or agitated water movement, such that the PAM molecules have adequate time to unfold and attach to the greatest number of soil particles, prior to settling out as precipitate.

 

Phase III: Primary Sedimentation

Due to the greatly enlarged particle size that is formed when soil particles bind to the polyacrylamide, the area, distance, and time required for sedimentation to occur is greatly reduced, compared to in conventional sedimentation basins.

 

Phase IV: Water Clarifier

Final water clarification takes place when colloidal solids that will not settle out by gravity, stick to choir logs, large pore jute particle curtains, or jute matting placed in the flow path. It is important to remember that the intent is not to filter the water but to maximize the contact surface within the flow path.

 

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