Geotube

Installation of Geotube® units or containers for dewatering starts with the preparation of a level area. An impermeable membrane is placed within the dewatering cell to contain and control the effluent. Nonwoven fabric and drainage media are placed directly below the TenCate Geotube® units to allow drainage from the bottom of the unit. The Geotube® unit is then unrolled with the access and vent ports on the top. Discharge and effluent return lines and valves are installed. Pumping of the slurry can then be started, and the slurry should have a relatively high water content to assist in pumping. Dewatering may take weeks as the walls of the Geotube® units filter out the solids and release water. Once the dewatering is complete, the Geotube® is cut open, and solids can be disposed of at an approved landfill. Installation of Geotube® units in underwater applications may be accomplished by lowering the Geotube® unit or container to the sea or lake floor in a steel frame and then filling it in place.

Layfield has design assistance available for both dewatering type projects and marine and shoreline applications of Geotubes®. The support includes specialized software capable of analyzing Geotube® sizes, quantities required, stresses, dewatered volumes, dry weight, pumping days, stacking arrangements and filtration fabric required. For Dewatering applications, Layfield can assist in determining an optimum dewatering solution with Geotube® technology. This includes the use of chemical testing to select and identify the benefits of mixing coagulants and flocculants with the sludge to speed up the dewatering. This testing also helps to estimate the dewatering time and size and number of Geotube® units required. Chemical conditioning of the sludge is usually required to obtain the fastest dewatering times. Chemical conditioning consists of the addition of polymers (coagulants and flocculants) into the sludge during pumping into the Geotube® units. For dewatering applications, Layfield has two dewatering tests available to assist in the design and estimating of the project. The RDT (Rapid Dewatering Test) helps to determine how the sludge dewaters through the Geotube's geotextile. A representative sample of about 500 ml is required and mixed with various concentrations and types of polymers and poured through a section of geotextile. The results determine the efficiency of the potential polymers, measures the volume of effluent removed from the sludge during dewatering, the time involved, and the quality of the water extracted. The GDT (Geotube® Dewatering Test) demonstrates the dewatering process using a small Geotube container (GDT bag). A sample size of about 60 to 90 litres is required. This test is essentially a small scale Geotube® test. The GDT test helps to visualize the dewatering process, further evaluate the preferred polymer from the RDT test, analyze the water effluent and estimate the achievable percent solids. The sludge is mixed with the polymer and filtered through the Geotube® unit material, and samples of the effluent are taken. Sampling is typically taken at 24 hours, one week, two weeks and three weeks.

Geotube® units or containers are manufactured with a special high strength woven geotextile that is ideal for various types of sludge dewatering, including sludge from paper mills, chemical companies, industrial plants, municipal facilities and hazardous contaminated sediments. The geotextile material is not affected by most sludges. Contact your Layfield representative with details on your application.