Membrane filtration can be explained as a method of allowing certain materials to permeate a surface while blocking others. For water, this means allowing clean water to flow through the membrane while eliminating sediments and other materials or pathogens. Membrane filtration is a multiple-step process which is considered to be one of the most cost-effective water treatments available.
Types of Membrane Filtration
There are two basic types of membranes used in water treatment. The properties of each type differ, along with the specific level of filtration. Basic filtration types are:
Micro and Ultra filtration
These types of membranes remove particles, similar to conventional media filters, but with a higher degree of reliability and robustness. Micro and ultrafiltration systems generally operate in “dead-end” mode, that is, all of the water is filtered, and then the membranes are periodically backwashed to waste.
Nanofiltration and Reverse Osmosis
These types of membranes uses a composite material that provides filtration of smaller ions. The nanofiltration and reverse osmosis membranes typically operate in a “cross-flow mode”, with a continuously produced waste stream.
How Membrane Filtration Systems Work
Membrane systems use pressure or vacuum to push or draw clean water through the membrane while rejecting and concentrating the contaminants for disposal. As the size of the contaminants to be removed decreases, the pressure required to separate the clean water increases. Micro and Ultrafiltration systems that remove particles can operate below 5 psi and up to 30 psi typically. Nanofiltration and brackish water reverse osmosis membranes that remove dissolved solids typically operate at 100 to 250 psi pressure. As the salinity of the water being treated increases the required pressure continues to increase. A seawater reverse osmosis system can operate at 800 to 1000 psi.
Designing membrane systems to optimize the hydraulics and minimize energy consumption is a key focus for Harn R/O to keep total system costs down.
At Harn R/O Systems we have been designing and installing membrane treatment systems since 1972. As one of the oldest, and most experienced membrane treatment companies in the industry, we offer services ranging from design/build contracts to maintenance and retrofitting existing systems. To find out more about our state of the art services, please contact us today.