OUR SPECIALISATION > Filtration and dewatering

Surface filtration (filter presses)
Depth filtration (sand filters)
ENVITES solutions


This concerns separation of liquid suspensions by means of a liquid flow through a permeable barrier. The suspended solids are entrapped in the barrier or on its surface.

The main filtration methods used in water and slurry management of water and wastewater treatment plants are
surface and depth filtration.

Surface filtration (dewatering)

Suspended solids are separated from the liquid on the surface of the filtration partition.

During surface (cake) filtration, the first entrapped particles are of a bigger size than the size of holes in the porous layer – during the cloth filtration they are bigger than the mesh of the filtration cloth (mesh sieve). The basic layer of settled particles formed on the cloth retains smaller and very small particles. If their concentration in the suspension is higher, these particles create clusters („vaults“) in front of the filtration partition and the basic layer of the slurry cake is formed. The thickness of the slurry cake increases with the filtration time.

The objective of the dewatering process is to achieve the highest possible dry solids content of the filtration cake while achieving the cleanest possible filtrate. What appears as an optimum solution for such separation (filtration) is in many cases the use of the filter press.

Depth filtration

Fine suspended particles are separated from the liquid in the porous area of granular or filamentous layer.

The depth filtration is usually used in the process of technical treatment of water for elimination of fine mechanical impurities from water flowing usually through a sand layer.

Fine particles settle in the pores of the granular inhomogeneous filter layer at a low flow rate of concentrated suspension. The entrapped particles help separate very fine particles of suspended solids. The depth filtration process imitates surface water treatment in the environment.

The depth filters are used prevailingly for water and wastewater treatment in water management and power plants or for additional treatment of sanitary sewage and industrial wastewater. In practice, water treatment and post-treatment of water is usually ensured by filtration in open or closed (pressure) sand filters.

ENVITES solutions

The company ENVITES produces and delivers the following filtration equipment:

For surface (chamber) filtration:

For depth (sand) filtration: