Membrane Technology: Emerging Technology in Water Purification

Membrane Technology a generic term for a number of different, very characteristic separation processes. These processes are of the same kind, because all of these use semi-permeable membrane. It works without addition of chemicals and with low energy use. Separation process based on the presence of a semi-permeable membrane.

Membrane acts as a very specific filter that will let water flow through, while it catches suspended solids and other substances.

Benefits of Membrane Technologies over Existing Water Purification Methods

• Process can take place while temperatures are low


• Uses smaller space requirements (footprint); membrane equipment requires 90 to 95% less space than conventional plants


• Most of the energy that is required is used to pump liquids through the membrane, therefore, there is lower energy costs


• The process can easily be upgraded or expanded

MEMBRANE TECHNOLOGIES

Reverse Osmosis

A high-pressure, cross flow process, which separates dissolved solids from water through the use of a semi-permeable membrane.

In Osmosis, water flows from a column with low dissolved solids content to a column with a high dissolved solids content to attain equilibrium. Osmotic pressure is the pressure that is used to stop the water from flowing through the membrane, in order to create balance. By pursuing pressure that exceeds the osmotic pressure, the water flow will be reversed; water flows from the column with a high dissolved solids content to the column with a low dissolved solids content; thus the term Reverse Osmosis.

Nanofiltration

Nanofiltration is a pressure-related process, however, feed pressure is generally lower compared to RO Systems.

Process is the same as reverse osmosis in terms of concept and operation. However, while Reverse Osmosis removes the monovalent ions at 98-99% level at 200 psi, Nanofiltration membranes’ removal of monovalent ions varies between 50% to 90% depending on the material and manufacture of the membrane.

Microfiltration

MICROFILTERS membranes with pore size ranging from 0.1 to 10 microns. Microfiltration is a low pressure (10-100 psig) process for separating larger size solutes from aqueous solutions by means of a semi-permeable membrane. It removes bacteria and partially filters out viruses.

Ultrafiltration

Utilize filter membranes with pore size ranging from 0.005 to 0.1 micron. It is a low pressure (5-150 psig) process for separating larger size solutes from aqueous solutions by means of a semi-permeable membrane. Removes suspended solids, colloidal particles, bacteria and viruses and retains oils, particulate matter, bacteria and suspended solids, macromolecules and proteins.