Sludge and Sediment Dewatering - Nautilus Dragados

Sludge is generated in processes across various economic sectors, and its proper disposal often entails significant technical challenges: sediment can clog navigation channels; industrial mining operations produce large volumes of waste that require environmentally friendly treatment; and a huge amount of sludge is produced daily worldwide as a result of drinking water and wastewater treatment processes. Furthermore, lagoons and ponds, once used as storage solutions, now represent a major problem.

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Generally speaking, all types of sludge require a drying process as part of any treatment. Various procedures can be used in this process.

By providing a fast and cost-effective means of sludge dewatering, geotextile tubes are the ideal treatment solution for most applications. The large tubes have high volumetric capacity and optimal filtration performance, while occupying a relatively small area. Geotextile modules can also be used for permanent containment of the sludge cake resulting from dewatering.

The removal of sludge, sediment, and various wet wastes from mines, industrial plants, construction sites, and water treatment systems is generally laborious and expensive.

For these reasons, drying these materials prior to final disposal tends to be the most economical solution.

Geotextile tubes offer a fast, cost-effective, and viable dewatering solution for a variety of materials.

Geotextile tubes provide a fast and economical way to dewater sludge and sediment. The large modules provide high operating capacity and optimal dewatering performance, while occupying a relatively small area.

Made from geotextiles, high-tech fabrics manufactured for this specific application, the tubes can be stacked in multiple levels to further improve the system’s storage capacity. Significant cost savings can be achieved in terms of energy, fuel, and maintenance costs associated with sludge transportation and dewatering, as is typical with other systems.

Geotextile tubes can also be used for permanent confinement of dried and consolidated material without any risk of rehydration (e.g. rain), even during periods of prolonged operation.

As a result, a higher amount of dry solid waste is achieved compared to, for example, drying beds. Geotextile tubes not only act as a durable and reliable containment system, but also somewhat minimize the emission of the characteristic unpleasant odor of sludge.

Several factors must be considered when choosing the best sludge dewatering and disposal system for a specific application.

Decision criteria include the required dewatering capacity and operating speed; water quality; reuse possibilities (sludge or percolate); available space; and maintenance requirements. In addition to the above, and equally important, the capital investment associated with system implementation must be considered. Generally speaking, system efficiency is the most decisive factor in most projects. It is important that sludge be removed from problem areas as quickly as possible, enabling a rapid reduction in volume and facilitating disposal, while simultaneously contributing to a reduction in overall project costs.

These three crucial factors are illustrated by the following project example for a sludge volume of 100,000 m3 and a dredged volume of 345,000 m3.

Nautilus Dragados España, headquartered in Málaga, Spain, specializes in the dredging and cleanup of ports, beaches, and other aquatic environments. Originally founded in Norway, the company has accumulated extensive experience in cleanup and restoration projects there. We operate along the entire Mediterranean coast of Spain and part of the Atlantic, covering the entire coast of Spain and Portugal, as well as Morocco. Our commitment to sustainability and the environment is at the core of our mission. We utilize advanced technologies such as polymer/Geobag dewatering to ensure our operations are efficient and environmentally friendly. At Nautilus Dragados, we pride ourselves on providing innovative solutions to address marine environmental challenges.

What is a geotextile tube?

Geotextile tubes are large sludge dewatering bags or geo-containers constructed from high strength, permeable geotextiles. They work with any material that is hydraulically transported. In most applications, the use of polymers is recommended to enhance the dewatering process. Geotextile tubes are cost-effective, fast, and efficient and have minimal environmental impact.

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.

With competitive price and timely delivery, PENNPLAN sincerely hope to be your supplier and partner.

• 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

US Fabrics' EcoTubes™ Geotextile Tubes

US Fabrics' EcoTubes™ 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.

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.

In most cases, the EcoTube™ 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 tube flat on level ground
• Make sure tube is constrained and secured
• Place tube on an impermeable geomembrane if erosion is a concern
• Connect and secure pump hose to filling port sleeve
• Monitor geotextile tube during filling for possible ruptures
• Utilized repeated cycles of filling and dewatering
• Deposit filled tube properly in a landfill or cut 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.

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 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 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. 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 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.

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 an EcoTube™for your project.

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

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.

If you want to learn more, please visit our website dewatering geobag.