ONE OF Europe's busiest ports is seeking approval to build a prototype dewatering plant that will squeeze dredged material dry.
Antwerp Port Authority is hoping to reap huge benefits by mechanically dewatering the 350,000t of dry matter weight (TDM) of material dredged each year through maintenance. This is normally dried in huge lagoons but mechanised drying is expected to be quicker and will consequently need less space.
Antwerp wants to free up close to 100ha of lagoons to develop a massive new container handling yard.
'The dewatering plant is critical to port expansion, ' said project engineer Liv Duerinckx of MWH, which is carrying out design of the plant and handling the port's planning application.
MWH and Belgian partner Seghers Kappel Group estimate the Port Authority's land take can be reduced from around 120ha to 20ha by using mechanised dewatering.
Dredged material has historically been dumped either at sea or in landfill sites. Disposal at sea is becoming more difficult under new environmental regulation.
For land disposal it is necessary to dry the dredgings to make them easier to handle and to reduce landfill costs. Water content is typically reduced from 80% to 85% to 70% to 60%.
In lagoons this can take up to a year.
The prototype mechanical process will use a combination of centrifugal tanks to settle out sand and heavy fines, chemical flocculation, and a series of chamber filters, which will sieve silts from the water.
Drying will take a matter of hours. Total project cost is expected to be E28M.
Even through the mechanical process is energy-intensive MWH predicts that it will reduce treatment costs to E26-E30/TDM compared to E30-E45/TDM for lagoons.
Because the mechanical process will produce material with engineering properties the port also stands to sell dry material on to the construction industry.