Membrane Technology


Microfiltration ( MF ) is commonly used to remove suspended solids, bacteria and cysts from the water. Ultrafiltration ( UF ) removes viruses alongside too , macromolecules and colloids . 
MF and UF is mostly a pressure driven membrane process . Under the influence of differential pressure across the membrane , water is pressed through the membrane . Particles larger than the pore diameter can be retained by the membrane and remain in the retentate . For MF , the pore diameter 0.1-5 uM , for UF it is 0.02 to 0.1 microns.

Nanofiltration (NF) is used for removal of multivalent ions ( almost entirely ) , monovalent ions ( partially) , color, odor and flavorings and dissolved organic compounds such as pesticides. Reverse osmosis (RO) has in relation to nano- filtration, a greater removal efficiency , in particular with regard to monovalent ions.

A pump presses the fluid through a membrane in reversed flow direction compared to osmosis . By applying a pressure difference across a semi-permeable membrane, this can work as a filter : the solvent will then move to the side where the sum of the external pressure and the osmotic pressure is the lowest. If the external pressure on the side of the concentrated solution is large enough, tyhe pure solvent ( without taking with it the dissolved substances ) will be pressed to the other side of the membrane . In simple language , this means that water is pressed very hard through a sieve with microscopic holes.

A semi-permeable membrane ensures that only very small molecules, such as water , can pass the membrane . The pore size for NF is > 1 nanometer , the pore size for RO is  <1 nm.

Komt voor in

Biological treatmentBiological treatment
Effluent polishingEffluent polishing
Waste to valueWaste to value