Antiscalant is an additive injected in water before subjecting it to reverse osmosis. An antiscalant, as the name suggests, serves to delay the scaling of salts and particles such as calcium carbonate, calcium sulfate and barium sulfate. Scaling simply means the accumulation of the salt and particles on the membrane used in reverse osmosis, causing blockage. Most natural water will have high levels of salts and particles, and the addition of an antiscalant will make the process of reverse osmosis go smoother and faster.
Reverse osmosis in turn is the process of filtration in which large molecules and ions are removed from the water through pressurizing it and making it pass through a selective membrane. Only the solvent or purified water comes out on the other side. This process is usually used to purify ground water, salt water, or even tap water in homes.
Antiscalants inhibit precipitation reactions using three principles: threshold inhibition, crystal modification and dispersion. Antiscalants are cheaper compared to water softening, which is why it is a preferred choice in large scale reverse osmosis operations.