Membrane systems filter wastewater and remove impurities. Water treatment facilities use membrane systems to separate impurities from water that needs to be recycled back into the distribution pipeline. These systems contain pumps and use several filtration methods, including reverse osmosis, nano-filtration, ultrafiltration and micro-filtration.
The technology behind membrane systems separates water from other substances, such as oil and gas. These systems do not typically use any chemicals to draw impurities out of the water. All types of water — including ground, waste and surface — are filtered in membrane systems. The systems are industrial size and are typically used in manufacturing plants or wastewater treatment facilities.
Within the system is a semi-porous wall that catches a certain degree of solid waste. The wall lets the water pass through, but still manages to trap heavier and thicker liquids. In some cases, not all pollutants are stopped by the wall, which is why some wastewater plants use additional treatments to eliminate hazardous substances.
Some types of membrane systems used in industrial environments are placed in water tanks, while others use a pressurized system that consists of several pumps. Depending on the make and model, the membrane technology can remove as much as 98 percent of water pollutants. There are different processing speeds and filtration methods that can be customized according to plant use.
Treatment plants typically use micro and ultra filtration methods to catch larger-sized solids. Pressure in these types of membrane systems tends to be lower, while the amount of water that it processes is quite high. This type of filtration might be used by plants that need to be as productive as possible and treat water that does not contain small foreign substances.
Nano-filtration and reverse osmosis might be used when smaller particles need to be removed from the water. Reverse osmosis is a filtration method that many bottled and spring water distributors use to purify drinking water. At-home filtration systems that attach to faucets will typically use reverse osmosis as well, since many of the impurities in drinking water are microscopic. The high pressure used in these filtration methods means that productivity tends to be lower.
Higher levels of selectivity are associated with membrane systems that are designed to eliminate small particles. Rather than separating the particles from the water through a semi-porous wall, nano-filtration and reverse osmosis use a technique called diffusion. This technique spreads the impurities apart by using a series of random movements.