Sediment and Sludge Treatment

Vacuum consolidation Kluizendok (Gent, Belgium)

This project was part of the construction of the Kluizendok complex along the Gent-Terneuzen canal. This required the accelerated consolidation of a disposal site for dredged sediment. This was done by adding a drainage network of sludge basins, after which an injected sand layer provided the required overburden.

Instead of covering these basins with a layer of sand - to make them accessible to machines – and installing vertical drainage blades, we opted - for the first time - to install these blades horizontally. A new rig and working method was thought of to do this.

Horizontal blades are just as efficient as vertical blades and this method also has numerous benefits. For example, the top load can be added all at once and the dewatering system is greatly simplified.

To be able to horizontally install the drainage blades a new rig was developed. The "Pashkin Mes” was conceived and developed entirely within the company. It was constructed from a supply system and a central beam supplied with twelve guiding ducts that end in removable wings. With the blade, twelve blades (2 rows of 6) can also be positioned with an individual spacing of 1 m (both vertically and horizontally). Thanks to the special construction, the blades are positioned with a precision of 5 cm.

The blade is carried by a hydraulic excavator. So that these can move along the sludge surface, the sludge basins are submerged under water and the excavator is positioned on a pontoon. On two dykes facing each other, a winch is positioned that pulls the pontoon over the sludge basins. By placing the blade at the desired depth during this trip, the blades are inserted in the sludge. Upon departure and arrival, the ends of blades were secured to the bank and later incorporated in the dewatering system. Thus the drainage water was drained to the discharge point. DEC positioned some 500,000 m horizontal drains in four sediment basins.

After installing the blades, an eight-metre-thick sand layer was injected as a top layer, pushing the water in the blades. After one year, the accelerated consolidation was complete.