Antiscalants for Reverse Osmosis Membrane Systems
For non-residential systems, another option to avoid calcium carbonate and calcium sulfate scaling is by the use of antiscalants. These are injected directly into the feed water upstream from the cartridge filter. Dosage of antiscalant depends on the feed water analysis but usually is between 2 to 5 ppm. In simplified terms, the antiscalants delay the scale formation process. This delay is sufficient to avoid precipitation of calcium carbonate and calcium sulfate on the membrane surface. As this delay is for a finite period, scaling can take place in systems on shut down. For this reason, it is a good practice to flush the membranes with permeate or feed water at shut down. By this flush, the concentrated solution in the membrane is displaced by the permeate or feed water.