Antiscalant

Antiscalant is a chemical that is dosed before the water from the pre-treatment enters the reverse osmosis membranes.

It prevents the reaction of calcium (Ca++), magnesium (Mg++) and bicarbonate (HCO3) ions and prevents precipitate formation on membranes.

If antiscalant is not used, poorly soluble salts accumulate on the membrane surface and precipitate is observed on the membrane surface. The most common precipitate types are calcium carbonate (CaCO3), calcium sulfate (CaSO4), barium sulfate (BaSO4), strontium sulfate (SrSO4). Occasionally silica and calcium fluoride (CaF2) precipitates are also observed.

Table 1 shows the relationship between precipitation formation and Reverse Osmosis System performance. When precipitation formation starts, there is a slow decrease in system performance for a while. But with the increase of precipitation, the performance decreases rapidly. The rate of decrease in system performance varies according to the type of precipitate.

As can be seen from the table, Calcium Carbonate-induced precipitation caused a faster performance decrease than Sulfate-induced precipitation. Precipitate formation on the membrane surface causes a decrease in effluent capacity and causes damage to the membranes.