Passive Dewatering
Geotextile Dewatering Tubes
Dredging Solutions provides unparalleled experience in the deployment and use of GeoFlow geotextile dewatering tubes to passively dewater fine silts and sludges. The process of passive dewatering involves the filling of high strength woven polypropylene containers with a flocculated sludge feed. The 425 micron pores in the geotextile from which the tubes are manufactured retain the flocculated solids while allowing clear filtrate to escape.
A lined level, bunded area is required to house the GeoFlow dewatering tubes and sump collected filtrate is then returned via gravity or pumping to the respective dam or lagoon, or processed as required.
Due to the surface tension exhibited by full containers, rain cannot permeate the geotextile weave, allowing the contained solids to become progressively drier whilst remaining fully contained. The containers continue to consolidate and dewater to the required moisture level after the filling has finished and all other equipment has been removed from site.
Key benefits of passive dewatering:
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High filling rate – unlimited depending on project specifics
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Less time on site – lower operating costs
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Multiple manifolded containers can be filled concurrently
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High level of control over the moisture content of the final product
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Convenient on-site storage of biosolids – odour mitigation
Passive Dewatering Process
Civil Establishment
The nominated dewatering area should be level and have bund walls created to encase the area. An impervious liner is then installed, in addition to the creation of a spillway or a sump to assist with filtrate return.
GeoFlow Dewatering Tube Layout
GeoFlow dewatering tubes are laid out on the prepared dewatering area. Where multiple containers are required each tube is manifolded from the central dredge delivery line and able to be isolated via individual valves.
Pumping
The dredged sludge is pumped to the dewatering area and flocculated in line with a polymer dosed prior to entry into the dewatering containers. Flocculation effectiveness is checked via a sample tap just prior to entry into the GeoFlow dewatering tubes.
Dewatering
The clear filtrate percolates through the pores in the woven geotextile material and makes its way back to the nominated filtrate return point.
Consolidation & Removal
At the end of filling cycles, the GeoFlow dewatering tubes are taken offline for final dewatering and consolidation. Once a target solids content has been reached within the tubes material can then be excavated and transported offsite for beneficial reuse or to landfill.
