3 Sep 2021

Blog Bite 2: TenCate Geotube® Slurry Dewatering - How Dry is Dry?

By Norhisam Omar

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TenCate Geotube® dewatering technology results in high volume reduction and retention of solids. Engineers evaluating Geotube® dewatering systems often ask, how dry is dry when discussing the properties of dewatered cake within the tubes.  In our first blog bite, we listed some factors that would determine this, namely the types of slurry and its composition. Let's move on now to the second Bite.




Tube Design

Ideally, the size, shape and fill port configuration of Geotube® dewatering units should be supplied in a form that suits the type and volume of slurry to be dewatered.

As an example, slurry that has a high SG or is more granular in composition does not flow down the tubes in the same way as a biosolid waste would. So, whilst some projects can be undertaken using off-the-shelf standard tubes, others will require bespoke design and supply, to facilitate uniform filling and optimized dry solids capture.

Impacts of Polymer and Weather

Whilst some slurry types do not need polymer dosing, the use of polymers significantly enhances the dewatering process by efficiently clumping particles together and facilitating the release of clear effluent out through the tube fabric.

Relatively simple tests on representative sample of slurry are undertaken to determine the polymer type and dose rate needed for optimized dewatering.

As a general statement, the volume of polymer required per ton of slurry is significantly less for Geotube® dewatering systems than mechanically dewatered systems. Geotube®, being a static system requires a single polymer prior to the slurry entering the tubes.  

Based on experiences with dewatering projects in tropical climates, dewatering operations and processes can still proceed in rainy conditions. The solids contained within a Geotube® unit is generally unaffected by rainfall, while hot and sunny weather will naturally speed up the drying process.  

A pilot tube trial is worth considering when a project involves huge or extreme quantities of slurry to be dewatered. Simulated to actual process conditions, the pilot tube trial can be used to predict final solids concentration or dryness achievable and may indicate the dewatering time required.


Dewatered gold slurry extracted after 21 days for reprocessing to recover residual mineral content


Dewatered gypsum waste after 5-6 weeks with solids concentration over 55% . Typical process of the pilot tube trial


Example of environmental dredging of river sludge after 4-5 weeks of drying with solids concentration of 30% to 35% 


Dewatered sludge from lake cleaning at a national zoo after 4-5 weeks of drying with solids concentration of 30% to 35% 


TenCate Geotube® dewatering system is highly effective in producing high solids retention for a wide variety of industrial, agricultural, wastewater and mining and mineral slurries. Geotube® units can be sized to suit the type and volume of slurry, from small bulker-bag type containers to super large units capable of retaining more than 3,000 m3 of dry cake.

To validate the evaluation on solids concentration and the optimum polymer dosage required, various dewatering tests can be carried out, such as Rapid Dewatering Test, small pillow bag test or Geotube® Dewatering Test. These are useful preliminary assessment tools.

If you'd like to know more, email us at info.asia@tencategeo.com 

We hope you have enjoyed Blog Bite #2. If you have missed the first Bite on "How Dry is Dry", here's a quick link to Bite #1 . Till next time, stay safe and stay tuned to Blog Bites.

TenCate Geosynthetics Asia
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