R/O In water Treatment

In wastewater treatment, reverse osmosis is a water purification technology that, like ultrafiltration, uses a semipermeable membrane to remove larger particles from drinking water. But in reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential, a thermodynamic parameter.

Reverse osmosis removes many type molecules and ions from solutions, including bacteria, and is used in both industry and potable-water production.

In use, solute is retained on the pressurized side of the membrane and the pure solvent passes through it. The membrane “selectively” allows smaller component solutions, such as the solvent, to pas feely, while not allowing large molecules or ions through the pores.

When forcing water through a semi-permeable membrane, pressure is applied to the solution, usually by a pump, allowing water and other molecules with low molecular weights (less than about 200 grams per mole) to pass through micro-pores in the membrane.

Most reverse-osmosis installations use a cross-flow to allow the membrane to continually clean itself. As fluid passes through the membrane the rejected species is swept away from the membrane.

Reverse osmosis in industrial and commercial applications, where large volumes of treated water are required at a high level of purity, typically operates at pressures between 100 psig and 1,000 psig, depending on the membranes chosen and the quality of water treated. Most commercial and industrial applications use multiple membranes in series. Processed water from the first treatment stage can pass through additional membrane modules to achieve greater levels of treatment for the finished water. The reject water also can be directed into successive membrane modules for greater efficiency, though flushing will still be required when concentrations reach a level where fouling is likely to occur.