Erosion and Sediment Control Tip #25

 

Polyacrylamide can be used in different forms to flocculate suspended soil particles and reduce turbidity.  One such form is a polymer block or log which is used in channelized flows or other concentrated flows. These can be used in flows that are gravity fed or created by pumping or other mechanical devices. Polymer logs are solid forms that slowly release polymer into the water stream binding sediment through flocculation. It is very important to understand how to properly use this type of flocculant to set up correct application for desired treatment.  Here are a few suggestions offered by Seva Bray of Applied Polymer Systems, Inc.

Site specific testing is always suggested to ensure the correct log is selected that will meet NTU, TSS, and other discharge limits. (Reaction time is also found from the sample and this will determine treatment time needed before discharge)

• Polymer logs must be placed directly in the flow of water so there is full contact between the polymer log and the turbid water.
• Polymer logs should be placed closest to the source of flow. Example: Close to pump or at the top of the ditch.
• Full mixing and reaction time needs to be completed. Once mixing and reaction is done and flocs have fully formed particulate can be captured or settled so only clarified water is discharged.
• Make sure you have the correct dosage and reaction time. The right number of polymer logs are needed for the expected flow rates. (Manufacturer can help with this)

Other important factors for successful polymer log treatment systems:

• It is very important to keep the polymer logs hydrated whenever possible. This will allow the logs to continue to release a steady dose of polymer as water flows over and around them.
• Place polymer logs out of mud or sediment. Blinding can occur when a polymer log is placed in mud or sediment. This is where sediment coats the log and impairs the ability of the polymer log to dissolve.
• If any blinding/sediment coating has occurred use a wire brush to remove sediment from the polymer log so it may continue to dissolve.
• No new sediment can enter the ditch system once water has contacted the polymer logs and has been treated. If new sediment enters after polymer log treatment it will create new turbidity and compromise the treatment.

 

Thanks Seva and Applied Polymer Systems, Inc. for the help with this TIP.

 

 

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