filtreringslag

Filtreringslag is a term used in water treatment and geotechnical contexts to describe a layer within a filtration system or a soil layer where filtration processes remove suspended particles and contaminants from a fluid as it passes through. In municipal water treatment and industrial filtration, the filtreringslag refers to the media layer, typically consisting of granular materials arranged in discrete levels. Common configurations use combinations such as coarse gravel at the bottom, with progressively finer media above it, for example anthracite, silica sand, and gravel. The media provide mechanical filtration by straining particles and offer increased surface area for adsorption and biological activity, aiding removal of turbidity, organic matter, and micro-organisms.

The filtration layer is usually preceded by pre-treatment steps like coagulation and flocculation to form larger aggregates that are easier to trap. It is followed by backwashing, a maintenance process that reverses flow to lift and suspend accumulated solids, thereby restoring porosity and hydraulic conductivity. The depth and composition of a filtreringslag depend on the required water quality, flow rate, and plant design.

In geotechnical or environmental applications, the term can also describe a natural or engineered layer in soil or a drainage system that reduces percolation speed, acts as a barrier to contaminants, or supports infiltration management. The performance of a filtreringslag is governed by particle size distribution, porosity, hydraulic conductivity, clogging tendency, and the integrity of the media.

Terminology and specifications may vary by country; in Swedish literature, filtreringslag commonly refers to the filtration media layer within filtration units.