RO and DI filters have different physical reactions that purify water. Reverse Osmosis is used to purify tap water, making it approximately 90% to 99% pure. Deionization (DI), filters convert positive hydrogen and negatively hydroxyl molecules into water contaminant molecules. Water polishing is sometimes used to describe DI filtering or other processes.
It is crucial to understand the differences between reverse osmosis and deionized water purification units for your laboratory. Laboratory workflows and daily operations are greatly facilitated by having access to high-quality water. You can make an informed decision about water purification systems by looking at the different ways of producing RO and DI water.
Reverse Osmosis Water
RO grade water or Type III water is the reverse of naturally occurring osmosis. Osmosis refers to the movement of water molecules through semipermeable membranes from low ion to high ion levels. Our cells use the osmotic process to maintain the intercellular osmotic equilibrium. It is as simple as increasing pressure on one side of the system to produce RO water. In the case of untreated or more dirty water, the system will apply additional pressure to the other side. The feedwater is then forced through semipermeable membranes, which results in purified water. The RO process can remove between 90 and 99 percent of contaminants. RO purification, although not perfect, is cost-effective because RO membranes can last years if they are used correctly.
Type II water is DI water. It is purified water with almost all of its mineral ions removed. This includes cations such as sodium, calcium, and iron as well as anions such as chloride and sulfate. Specially manufactured ion exchange resins are used to convert hydrogen (H+), hydroxyl (OH) ions into dissolved minerals. Then, they recombine to make water (H2O). The active H+- and OH- molecules of the DI resin are displaced by negatively and positively charged contaminants over time. At that point, the filter must be changed. The DI purification process can be used to supply Type II or DI when required. The ion-exchange resin is not a physical filter that captures pore size bacteria or dissolved organics. This makes it essential to know the production water requirements before selecting a water purification system.
There are many ways to determine the quality of purified water. Direct measurement of resistivity or electrical conductivity is the simplest way to determine water quality. When electrodes are placed in water, most dissolved inorganics can transmit an electric current. The conductivity or resistance of the water sample is affected by the number of ions present. Conductivity can be expressed in microsiemens/cm and is used for measuring water with many ions. Ocean saltwater, for example, is densely packed with inorganics and dissolved organics. This allows for an electrical current to pass through the water which corresponds to its 56,000 U/cm measurements. Ultrapure Type I water, however, has a ppm level in dissolved organics and inorganics which results in a conductivity (or resistivity) measurement of 0.055 or 18.2 m/cm.
This post was written by a water treatment expert at Paragon Water Systems. At Paragon Water Systems we are the Manufacturers of the best Carbon Block Filter! We know that the best product comes from the best materials. We manufacture home water solutions such as reverse osmosis systems, under sink water filtration systems, showerhead filtration systems, carbon cartridges, and a wide variety of other products. Our focus is to provide Americans with safe and clean water throughout the home.