Investigation of Scaling and Inhibition Mechanisms in Reverse Osmosis Spiral Wound Elements

Understanding of crystal formation and growth conditions in reverse osmosis membrane channels enables us to develop efficient tools to control scaling in membrane facilities and increase their recoveries. Crystals are formed in dead areas and subsequently get out of them and sediment on membrane surface. Adsorption of polymeric inhibitor molecules to crystal surface was investigated as well as antiscalant behaviour throughout nucleation in dead areas and growth of crystals sedimented on membrane surface. Experimental dependencies of antiscalant adsorption rates on the antiscalant dosage values were determined. Examination of SEM images of crystals demonstrated that their size and amount depend on the supersaturation value reached in the dead areas. More efficient antiscalants delay the beginning of nucleation and reduce the rate of crystal growth due to adsorption and blockage of crystal growth process. Antiscaling property of inhibitors is also attributed to their ability to provide certain amount of adsorbent to block crystal growth during nucleation. A test procedure is described that enables us to predict concentrate composition in the dead areas and calculate supersaturation values that correspond to beginning of nucleation.

Automated summary

Understanding the formation and growth conditions of crystals in reverse osmosis membrane channels is important for controlling scaling and increasing recovery. Crystals form in dead areas and sediment on the membrane surface. This study investigated the adsorption of polymeric inhibitor molecules on crystal surfaces and the antiscalant behavior during nucleation and growth of crystals on the membrane surface. The results showed that the adsorption rate of antiscalants depends on the dosage values and the size and amount of crystals depend on the supersaturation value in the dead areas.