A variety of natural and derived processes have been used over the centuries to treat water and achieve an acceptable treated water quality. Filtration through naturally occurring rocks and sand evolved into commercial multimedia filtration in which tanks house varying layers of media to capture undesirable constituents and allow cleaner water to pass. Boiling water evolved into commercial thermal processes that employ extreme heat to separate water from salts and contaminants. More recently, Nature’s demand for equilibrium helped inspire the concept of reverse osmosis (RO) and the use of a semi permeable membrane to separate water from solids at the ionic level. In less than 50 years, membrane filtration technologies are among the fastest growing advanced technologies in the world.
The concept of filtering water via osmosis came to commercial fruition in San Diego, California in the late 1960’s when General Atomic (ROGA) developed a semi permeable membrane under a United States federal government project. Industry Pioneers soon perfected reverse osmosis (RO) and nanofiltration (NF) membranes and found commercial uses for the processes. Microfiltration (MF) and ultrafiltration (UF) membranes soon followed under private development with each establishing a unique treatment niche based on specific properties and field experience.
Most contemporary RO membranes are aromatic polyamides. NF membranes are a polyamide variant and the most common UF and MF materials of construction are Polyethersulfone (PES) and Polyvinylidene Fluoride (PVDF). Ceramic membranes with porosities in the MF and UF range are made of inorganic materials. In general, RO is used to reject dissolved ions, NF rejects dissolved divalent ions and high molecular weight organics, UF rejects high molecular weight colloids (100,000 to 150,000 Daltons) and MF rejects particulates and pathogens. More specific properties of each of these processes can be found in the AMTA Fact Sheets.
Membrane filtration has become a viable and recognized method of water treatment, producing a water quality safe for human consumption, improving the properties of a waste stream destined for downstream waterways, and offering a multitude of additional process advantages.
AMTA is the only industry organization that focuses specifically on membrane processes including reverse osmosis (RO), nanofiltration (NF), microfiltration (MF), ultrafiltration (UF), electrodialysis reversal desalination (EDR), and membrane bioreactors (MBR). The AMTA website offers a wide range of proprietary Fact Sheets and a complete Digital Library of presentations, posters, and papers on all topics related to membrane treatment, membrane systems, and regulatory and compliance topics.