Key words
• Biological water purification: natural microorganisms can purify contaminated water biologically. In the food chain they are, so to speak, the cleaning team for water purification and are deployed for this purpose in water purification installations. Bacteria feed on the contaminated materials in the water thus ensuring a biological purification process, which is completed faster in an installation than in the wild owing to the higher concentration of bacteria and the higher level of oxygen.
• Density: thickness. The density of a substance is expressed as a volume unit.
• Filter cake: a filter cake has the appearance of solid matter and is the final product in the AMORAS installation. Once the sludge has been treated and as much water as possible has been extracted, the remaining mass is pressed into a specific shape, a 'cake", ready for transport and storage or reuse.
• Physico-chemical water purification: as in the case of most water used for industrial purposes, the water released from the AMORAS installation requires more than a biological water purification process. The water contains insoluble substances, oils, fats, contaminated matter or excessive concentrations of salt that cannot be treated by the cleaning team. Nonetheless, the water can be treated with physical or chemical processes. Subsequent to the physico-chemical water purification stage, the process is continued with biological water purification.
• Scrubbers: scrubbers are used in industry to remove air or gas from specific substances. The scrubber absorbs contaminated matter – in this case ammonia – so the airflow is purified.
• Suspended active sludge system: a suspended active sludge system works with active sludge separated from the purified waste water. It is called ‘suspended’ because it is a mixture of two substances where the one substance is mixed in very small particles with the other one. The active sludge and purified water may be separated by means of membranes or resettling tanks.
• Hydraulic: hydraulic is a drive system using a fluid (generally oil) to drive appliances under pressure, or start up a mechanism.
• Hydrocyclone: a cyclone – a cylinder that changes into a conical shape – uses intense rotation to separate material centrifugally on the basis of differences in density. The one material leaves the cyclone underneath and the other at the top in the hydrocyclone. Vacuum cleaners without a dust bag also operate according to this principle.
• Thickening basins: in the thickening basins the dilution water is removed again from the dredging spoil, so the matter is thicker and easier to treat.
• Disposal site: a disposal site is an embankment created by the discharge of material, in this case sludge.
• Membrane chamber filter presses: chamber filter presses pump (“press”) the sludge under increased pressure into an enclosed space (“chamber”), where the water is then squeezed out. It is forwarded along filter cloths or membranes to the water purification system.
• Microns: one thousandth of a millimetre.
• Maintenance dredging material: the dredging material hauled up during normal maintenance work is called “maintenance dredging material ”. This is sludge entering the port docks via the locks, for example. Consequently, this does not involve deepening operations but dredging so as to guarantee a ‘regular’ draught everywhere.
• Underwater cell: an underwater cell is a cavity established in the bottom of a port dock, for example, that is also blocked off, to create a ‘cell’ under water, where dredging material may be deposited without spreading over the bottom again.
• Dewatering: dewatering involves extruding water from material so that what is left is a dry mass.
• Desanding or sand separation: desanding involves treating a substance so the sand is separated from the rest of the material.
• Gantry: a gantry spans an open space.
• Process water: process water is water used for an (industrial) process. In the case of AMORAS this refers to all the water used to transport and treat sludge.
• Shelter dock: a shelter dock is a (smaller) dock where vessels may seek shelter when they drop anchor.
• Sludge: sludge is formed by particulate matter in flowing water that settles on the bottom. It forms a kind of clay, generally very fertile as soil.
• Tonne of dry matter: unit of measurement for the quantity of dredging material.
• Water purification: water purification is the general term for the removal of organic and chemical material from water. This may be based on a natural process (biological water purification) or an artificial one (such as physico-chemical water purification).