US Fabrics' EcoTubes™ Geotextile Tubes
Due to their cost-effectiveness, speed, efficiency and minimal environmental impact, sludge dewatering tubes (geotextile tubes) are increasing in popularity for municipal water & waste water treatment, marine dredging operations, agricultural remediation, construction dewatering and shoreline protection.
As an alternative to sludge lagoons, wet hauling, sand drying beds, wedge wire systems, presses and other mechanical dewatering methods, sludge dewatering 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.
US Fabrics’ EcoTubes™ are sludge dewatering tubes that will work with any material that is hydraulically transported. The list of materials that have been dewatered by geotextile tubes includes, but is not limited to: municipal water treatment and wastewater sludge, contaminated dredged material, agricultural animal waste and fine-grained, inorganic industrial sludge and shale gas fracking. For shoreline protection applications, the geotextile tube is filled with structural material such as beach or river sand.
US Fabrics' EcoTubes™ are constructed of high strength, permeable geotextiles and are resistant to ultra-violet light and the stresses associated with filling and placement including: abrasion, tearing, puncturing and flattening.
- Minimal environmental impact
- Small footprint
- Optimize land usage
- Work with a large variety of sediments, sludge and sand
- High-strength, permeable geotextile
- Tough, UV resistant
EcoTubes™ 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.
The EcoTube™ will be delivered to the site on a skid, rolled up on a pipe core in most cases. 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.
Polypropylene and Polyester
US Fabrics’ manufactures EcoTube™ sludge dewatering tubes from polypropylene and polyester. Polypropylene is a high strength material that dewaters quicker and more efficiently than polyester. It also deals with high pH levels better. It is, by far, the most common material used for manufacturing geotextile tubes for dewatering applications.
Polyester geotextile tubes are mainly used in beach and shoreline protection applications. For these applications, polyester offers several advantages. Polyester holds its shape better than polypropylene, making it better suited for use as a sandbag. Also, polyester can be coated easier and by a wider variety of materials than polypropylene. Since shoreline applications are long-term applications, if the material is not coated, a sacrificial shroud of a polypropylene geotextile or a covering of sand will be needed to protect the polyester from UV damage.
In addition, polyester achieves higher seam strengths (in excess of 1,000 pounds). Polyester geotextiles can also be produced in much higher strengths than polypropylene (in excess of 3,000 pounds). This makes polyester geotextile tubes suitable for projects where very high strengths are required.
Every geotextile tube project is unique. As such, 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.
EcoTubes™ 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 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 EcoTube™, 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. Experience has demonstrated that it is possible to fill sludge dewatering tubes to 70%-80% of their theoretical volume, but 50%-60% is more 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 EcoTube™ 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 EcoTube™ 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.
For large volume projects or on sites with a limited dewatering area, US Fabrics’ EcoTubes™ 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.
20 & 30 Yard Dumpster Bags
When space is extremely limited and time 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 jobsite to the proper landfill facility.
The Importance of Using Polymers
The use of polymers is highly recommended to enhance the dewatering process in most applications. If some fines or color is acceptable in the filtrate, then a polymer may not be required.
Polymers help the solids bind together and speed up the separation process. The proper polymer will improve the rate of dewatering, increase the rate and percentage of suspension of solids and improve the clarity of the effluent. Coagulants and flocculants are the main options. Selecting the right polymer is critical.
Parameters that must be checked 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 Hanging Bags to test your sludge.
For more info on polymers please see: Power Point Presentation: Polymer & Sludge Bags