Sludge Dewatering Geotextile Tubes

What is a geotextile tube?

A geotextile tube is an innovative engineering solution designed for various applications in environmental and hydraulic engineering. It is essentially a large, tubular bag made from permeable geotextile fabric. These tubes are filled with materials like sand, soil, or dredged sediments, and they serve multiple purposes, including erosion control, shoreline protection, and dewatering projects.

• Purpose: The primary purpose of geotextile tubes is to provide a cost-effective, environmentally friendly method for protecting and stabilizing shorelines, creating breakwaters, and managing sediments. They are also used in dewatering applications, where they allow water to filter out while retaining solids, thus concentrating the solid material for disposal or use in other applications.
• Construction: Geotextile tubes are constructed from strong, durable, and permeable fabrics that can withstand the pressures of the materials they contain and the environmental conditions they are exposed to. The fabric’s permeability allows water to escape while retaining the solid particles, making them ideal for dewatering and sediment containment.
• Applications: These tubes are widely used in coastal and shoreline protection projects, where they act as barriers against erosion and help in land reclamation. In dewatering applications, they are used to treat wastewater, manage sludge from industrial or municipal sources, and control sediment in water bodies. Geotextile tubes are also employed in the construction of artificial islands, reefs, and underwater structures.

The versatility and effectiveness of geotextile tubes make them a preferred choice for engineers and environmentalists looking to solve complex problems related to water management, erosion control, and environmental restoration.

What materials can a geotextile tube dewater?

The list of materials that can been dewatered by geotextile tubes includes:

• Municipal water treatment and wastewater sludge
• Contaminated dredged material
• Marine dredgings
• Agricultural animal waste
• Fine-grained, inorganic industrial sludge
• Construction dewatering
• Shale fracking waste water

What are the advantages of geotextile tubes?

As an alternative to sludge lagoons, wet hauling, sand drying beds, wedge wire systems, presses and other mechanical dewatering methods, geotextile tubes offer significant cost savings. And they are environmentally friendly. Often, the decanted water can be reused or discharged into local water tables, streams or storm drainage systems. Because they dewater faster than open-air pits and do not require standard heavy equipment, they create a smaller foot-print, increasing the number of potential dewatering sites and optimizing land usage when the area for containment and dewatering is limited. Sludge dewatering tubes are made from tough, UV resistant geotextiles.

• Cost-effective alternate to traditional methods
• Minimal environmental impact
• Small footprint
• Optimize land usage
• Dewater faster
• Work with a large variety of sediments, sludge and sand
• High-strength, permeable geotextile
• Tough, UV resistant

Geofantex Geotextile Tubes

Geofantex geotubes are manufactured from high strength polypropylene geotextiles and are permeable and resistant to ultra-violet light and the stresses associated with filling and placement including: abrasion, tearing, puncturing and flattening.

Geofantex geotextile tubes are made to the desired diameter from standard width geotextiles. The length of the sludge dewatering tube is limited only by its weight. Filling ports are regularly spaced along the length of the tube at appropriate intervals.

In most cases, the geotubes will be delivered to the site on a skid, rolled up on a pipe core. Alternate packaging, such as accordion folding, may be used. Although sturdy, geotextile tubes can be damaged during loading, off-loading and shipping. It is very important that any shipment be thoroughly inspected for rips and punctures before signing any shipping documents. In the case of damage, all problems should be noted on the shipping documents and the delivery refused. Once a damaged tube has been received and the shipping documents signed, it is nearly impossible to seek remedy from the shipping company.

How do I use geotextile tubes?

• Inspect geotextile tube for shipping damage
• Unroll the tube flat on level ground
• Make sure the tube is constrained and secured
• Place the tube on an impermeable geomembrane if erosion is a concern
• Connect and secure the pump hose to the filling port sleeve
• Monitor the geotextile tube during filling for possible ruptures
• Utilized repeated cycles of filling and dewatering
• Deposit the filled tube properly in a landfill or cut it open and remove solids

Every geotextile tube project is unique. As such, only general guidelines can be described, but each project requires consultation with a geotextile tube expert to identify the project’s singular attributes and to design the sludge dewatering process accordingly.

Proper site preparation is of utmost importance. Geotextile tubes can roll, especially during filling. It is important that they are constrained and placed on level ground. Once properly deployed and secured in place, the geotextile tube is hydraulically filled with dredged materials using a cutter head and suction dredge or with sludge materials using a feed pump.

Geofantex Geotubes have a “shirt-sleeve” style filling port. Simply place the hose into the port and secure it with a hose clamp, tie-wire, or duct tape.

Once the pumping begins, clear, effluent water will drain from the geotextile tube through the small openings in the permeable geotextile fabric. Often the decanted water can be reused or returned to waterways without additional treatment. During pumping, the elevation or height of the tube needs to be monitored to prevent ruptures.

A large volume of water may be released from the tubes during the operation and can cause erosion around the tube. As such, the rate at which the water is decanted must be monitored. The sludge dewatering tube bottom will develop a filter cake quickly, so the water will decant mainly out of the sides and top of the tube. Therefore, it may be beneficial to cover the deployment area in plastic such as Visqueen, and deploy sump pumps at all four corners of the dewatering area to collect the effluent. The effluent can then be returned creating a “closed-loop” system. If the tube will be exposed to external moving water, a scour apron made from an impermeable geomembrane liner with an attached anchor tube may be required.

Since the dewatering process will happen more slowly than the rate of hydraulically transported sludge entering the Geofantex Geotubes, repeated cycles of filling and dewatering will be required. After the final cycle, the solids in the geotextile tube will continue to densify further as residual water vapor escapes through the geotextile fabric. Typically over 99% of solids are captured.

Geotextile tubes fill to a complex, elliptical shape. As such, the tube will not fill to its theoretical volume. Typically 50%-60% is a realistic expectation.

When full, the entire sludge dewatering tube and its contents can be deposited in a landfill, remain on site, or the bag can be opened and the solids removed. To remove the solids, cut open the top of the Geofantex Geotubes with a box-cutter and fold back the geotextile. Use a front-end loader or excavator to scoop the material and load it into a dump truck or apply it directly to land if appropriate. The used Geofantex Geotubes can be hauled off to a solid waste facility.

The nature of the material and federal, state, and local regulations will help determine the acceptable procedure. Always get approval from the local regulatory agency before disposing of the sludge and the sludge dewatering tube.

Can I stack geotextile tubes?

For large-volume projects or on sites with a limited dewatering area, geotextile tubes can be stacked in layers. Stacking tubes requires addressing the unique issues affiliated with the project and project site. Proper site preparation and safety issues must be followed in addition to other considerations.

Do I need to use polymers with geotextile tubes?

Often a polymer coagulant or flocculant is required to improve the dewatering process. Polymers help the solids bind together. The proper polymer improves the rate of dewatering, increases the rate and percentage of suspension of solids, and improves the clarity of the effluent. Selecting the right polymer is critical. If some fines or color is acceptable in the filtrate, then a polymer may not be required.

Parameters that must be considered include sludge flow, sludge concentration, flocculent flow, flocculent concentration, post-dilution water flow, and injection points. It’s always best to consult with a professional polymer supplier and conduct bench tests to determine the correct products, optimum dosage, and proper methods for setting up a polymer mixing and injection system. US Fabrics offers small, hanging bags to test your sludge before purchasing Geofantex Geotubes for your project.

For more info on polymers please see: PowerPoint Presentation: Polymer & Sludge Bags

20 & 30 Yard Dumpster Bags

When space is extremely limited and time is of the essence, US Fabrics’ Dumpster Bags are the perfect solution. Designed to fit into a standard 20 or 30-yard dumpster, these smaller sludge dewatering tubes take up little space and once full, are ready to be hauled from the job site to the proper landfill facility.