Silt Bags and the Sludge Dewatering Process
Bag Filters for Water Treatment Plants
Question: I'm interested in using silt bags at a water treatment plant. I have recently heard of your products and would like some information about using them in the sludge dewatering process to filter backwash at our water treatment plant. We typically hire a sludge dredge contractor for sludge removal and dewatering. Will silt bags or dewatering tubes work as well and be cheaper?
I would guess that the percent of solids is at 25% with a volume is roughly 700 cubic yards (wet) total. I will also need input on how best to get the slurry into the geotextile bag. Do you recommend slurry pumps? How do you mix to re-suspend solids prior to transfer pumping?
Answer: Yes, silt bags and dewatering tubes are designed to help filter out materials on your site. Dewatering bags for silt are typically designed to be more economical and less work than standard dewatering equipment.
Determining the right dewatering product can depend on several different factors. We have a dewatering questionnaire to help determine the proper solution for your situation. We can send you this questionnaire and walk you through selecting the best option for the sludge dewatering process.
Some questions on the dewatering questionnaire include:
- What amount of liquid needs to be dewatered?
- Percent of solids in situ?
- Will polymers be used?
- How many gallons will be pumped into the bag per minute?
- How long is the project?
For water treatment plants and long term projects, we typically recommend the use of a geotextile tube instead of the geotextile bag. These dewatering products are larger in size to help contain and dewater large amounts of materials.
Geotextile Tube Features
- Lengths from 50 to 250 Feet
- Circumference Range: 15-90 Feet
- Woven Polypropylene Geotextile Material
- Fill Port for Every 50 Feet of Tube
- Can Be Used with Polymers
Geotextile Tube Benefits
- Minimal Equipment Required
- Bags can Operate 24/7
- No Complicated Components or Parts
Geotextile Tube Considerations
- Slurry / Sludge solids content
- Even placement of ports for distribution of sludge in each tube
- Drainage from each tube to appropriate retention area
- Stability of additional layers of geotextile tubes
- Slope and potential hazards of tube placement area
Slurry Pumps and Mixing
Slurry pumps are useful to transfer the mixture from the holding area to the tube during the sludge dewatering process. There are a variety of pumps available, depending on the slurry contents, consistency, and volume. Many pumps have an agitator attached to re-suspend the solids as the mixture is being pumped into the geotextile tube. For particularly coarse or heavy slurry particles, a standalone or side-mounted mixer will stir any sediment build-up.