This process is based on a fundamentally more conventional treatment method – chemical precipitation and flocculation, followed by sedimentation and filtration. The difference is that it combines much more compact lamella sedimentation with continuous sand filters, allowing higher flow rates than conventional filtration.
Higher flow rates over a smaller space
Lamella settling tanks can cope with significantly higher flow rates with the same space requirements and usually better results than conventional sedimentation. Thanks to the major advantage offered by the continuous filter – its ability to accumulate higher quantities of sludge – the lamella settling tank can be built to somewhat smaller dimensions than it could if backwashing sand filters were used.
The total amount of space needed can be reduced to around one third of the area required by a conventional system of a similar type.
The process is extremely robust and is particularly suited to treating surface water which shows significant variations in turbidity, or which needs large doses of precipitants.
At Nordic Water, we have installed systems based on this process in various water purification plants and industries worldwide, the oldest of which has now been operating without any problems for 15 years.
Typical values for Nordic Water’s turbid surface water treatment system:
Input values: Output values:
Turbidity: 0.5-1,000 FTU Turbidity: < 0.1 FTU Colour: 10-500 mg/l Pt Colour: < 5 mg/l Pt