The world of dredging has many purposes, including maintenance, land reclamation and port development. However, dredgers are also frequently used for the mining of minerals. In Jordan, Arab Potash Company (APC) is harvesting potassium-contained salts (potash) in the Dead Sea with two cutter suction dredgers. Potassium is extracted from the potash and used as a fertiliser in agriculture.
How does it work?
Water from the Dead Sea is pumped into the APC ponds for a few months each year. It flows slowly south through all ponds, and the salt settles in the first few to create extremely hard layers containing salt mushrooms. The other minerals do not settle, but flow to the southern ponds. After a few years, the northern ponds are silted up with salt to the extent that they block the water flow.
The Dead Sea is bordered by Jordan to the east and is the lowest body of water on the Earth’s surface –its shores lie 430.5m below sea level. Its high levels of salinity (it is 9.6 times more salty than the ocean) make it easy to float while swimming. However, this salinity results in a harsh environment in which plants and animals cannot flourish.
The salt content in the southern ponds decreases and the concentration of the potash increases because of the previously mentioned salt settling and water evaporating. This is exactly the purpose of this process. Finally, the potash content reaches a certain concentration level so that it also settles and is ready for harvesting.
The dredging of the potash in the southern ponds is a continuous process, but the APC harvesters are not able to reach the corners and sides of the ponds. The negative effects of this are that the ponds become smaller and the production decreases by 10%. This is why APC procured the cutter suction dredger (CSD) MUTAH. It is an IHC Beaver® 40 with a cutter power of 120kW, which is able to dredge the corners and sides of the ponds, and pump the potash directly to the harvesters. The potash is much softer than the salt and therefore less cutting power is needed.
To recover the northern ponds, another CSD (JARASH) dredges the salt to a depth of six metres. With a total installed power of 3,557kW, it is able to dredge and pump the salt ashore, creating tall heaps of material at the side of the Dead Sea.
The cutter suction dredger (CSD)
The CSD is a type of dredger that uses a rotating cutting tool to dislodge the soil in order for it to be drawn into a suction pipe. A CSD typically consists of a non-self-propelled pontoon with a pivoting ladder that houses the cutter and suction pipe. The types of soil it can handle include sand, gravel, clay, sandstone and soft rocks. CSDs are widely used for land reclamation projects, the construction of dams, dikes and breakwaters, the excavation of new harbour basins and canals, and improvements to the course of rivers.