TenCate Geosynthetics Netherlands bv

In-Barge Dewatering Application Offers Innovative Solution Where Lay Down Area Is Unavailable - Case Study


Courtesy of TenCate Geosynthetics Netherlands bv

Tight space constraints are solved by customized Geotube   units in floating barges.

Geotube dewatering technology has been used to deliver high performance solutions all over the world in more than 50 countries. Over 2,000 dewatering projects have taken advantage of Geotube containers since 1991. These have involved both small and large situations for lagoon cleanout, dewatering process waste, and even environmental remediation.

TenCate, manufacturer of Geotube materials, develops and produces materials that function to increase performance, reduce cost, and deliver measurable results by working with our customers to provide advanced solutions.

Land-based Geotube systems have been very effective in reducing the volume of collected materials by as much as 90 percent. The remaining solids can be buried on site or disposed of in landfills.

New Challenge and Creative Solution

A New York City power generating plant faced a difficult problem. Sitting on the East River in Brooklyn, the plant's cooling water intake tunnel was clogged with years of silt from the river-Limited access and workspace complicated this tricky situation. The plant had no available land at their location to serve as a dewatering cell. Traditional methods had been slow, costly, and created effluent water that clouded the river with silt from the dewatering efforts.

TenCate proposed a new solution — one the plant's owner was skeptical of at first. This plan required only four Geotube containers to be placed in two barges in the East River. The 50' x 140' barges were anchored adjacent to the plant above the silt-clogged intake tunnel.

'This in-barge dewatering application is a great example of TenCate's philosophy of providing our customers with problem-solving solutions,' said Mark Gunzenhauser, Vice President Sales -Geosystems. 'This involved a brand new way of creating a dewatering cell.'

Using 6-inch suction lines, divers went under¬water in the confined tunnel to remove and collect the silt that was then pumped to the SmartFeed system, a technology that chemically conditions sediment to enhance dewatering and tracks production and process parameters. From there the sediment was pumped to the Geotube units placed in the barges. As the silt dewatered within the Geotube containers, filtered effluent water drained into the hold of the barge. From there it was pumped back into the East River without any secondary treatment

Polymer Mix Plays Key Role

An important component of the Geotube system is the evaluation of an appropriate polymer program using the TenCate RDT Rapid Dewatering Test and the TenCate GDT Geotube Dewatering Test to optimize the dewatering process.

'The right polymer mix program greatly improves the efficiency of the dewatering stage,' explained Vicki Ginter, TenCate Market Manager. 'This project involved a constantly changing level of silt solids and flow — ranging from 4% to 11 % solids and from 400-1,500 gpm. Careful monitoring was needed here. We worked closely with Mineral Processing Services, our installation specialist, and their SmartFeed chemical conditioning system.'

As the silt was removed from the intake tunnel, it was first pumped to a SmartFeed mobile chemical feed system where an automated polymer mixing system injected the polymer into the slurry before it was pumped into the Geotube units.

Taking place at real-time dredging rates, the SmartFeed system monitored changes in solids and flow. It tracked the real-time performance data and adjusted polymer injection to the optimum level every 15 seconds. The computer-controlled polymer dosage system injected the slurry through an in-line regulated mixing chamber to insure proper flocculations. This maintained the customer's permit requirements for solids consolidation and effluent water quality. This polymer mixing with the collected silt sped up the dewatering process and improved the clarity of the effluent water.

The power plant was especially pleased with the effluent results. A representative remarked: 'Any environmental concerns evaporated when we saw the water solids separation process continue in the Geotube units. It became clear that the effluent water was much cleaner than the natural water of the East River.' And, the SmartFeed daily process records proved it.

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