How does the efficiency of an industrial RO systems vary with the quality of feed water?

When unfamiliar with the technical language used to explain various elements of RO system performance and the connections between these operational variables, reverse osmosis (RO) technology can be difficult to grasp.

This blog describes some of these critical concepts and gives a brief review of the variables, i.e feed water quality, that impact the performance of RO membranes. So, let’s get going…..

Feed Water Pressure Impact:

The water flow and salt rejection of RO membranes are both impacted by feedwater pressure. Water flows through a membrane by osmosis from the diluted side to the concentrated solution side. In order to counteract the osmotic pressure created by the feedwater stream, reverse osmosis technology applies pressure to the stream. The concentrated solution is subjected to pressure that is greater than the osmotic pressure, which causes the water flow to be reversed. The concentrated solution side's purified product water is produced by forcing a portion of the feedwater (concentrated solution) through the membrane.

An increase in feedwater pressure causes a direct increase in water flow across the membrane. Salt levels also rise when feedwater pressure rises. The association between increasing feedwater pressure and greater salt rejection is also present, although it is not as clear-cut as it is for water flow. As ineffective barriers to dissolved salts in feedwater, RO membranes allow some salt to flow through them at all times. This salt route becomes progressively blocked when feedwater pressure is raised because water can move through the membrane more quickly than salt can.

The quantity of salt that can be excluded by raising feedwater pressure has a maximum limit, though. As seen by the plateau in the salt rejection curve, salt rejection stops increasing at a particular pressure level, and some salt flow is still linked with water passing through the membrane.

Feed Water Temperature Effect

Temperature fluctuations in the feedwater have a significant impact on membrane production. Because water diffuses across the membrane more quickly at higher temperatures, water flux rises approximately linearly as water temperature rises.

Lower salt rejection or higher salt passage are other effects of increasing feedwater temperature. The capacity of a membrane to withstand high temperatures expands its working range and is crucial during cleaning operations since it enables the use of more powerful and efficient cleaning methods.

Influence of salt content

The kind and quantity of salts or organics in feedwater determine the osmotic pressure. Osmotic pressure rises as salt concentration does. Thus, the quantity of salt in the feedwater has a significant impact on the amount of driving pressure required to change the osmotic flow's natural direction. A higher salt content causes a reduced membrane water flow if feed pressure is constant. The feedwater driving pressure is balanced by the rising osmotic pressure.

Effects of healing

When feedwater pressure is applied, the natural osmotic flow between a concentrated solution and a dilute solution is reversed, resulting in reverse osmosis. The salts in the residual feed become increasingly concentrated as the percentage of recovery rises (and feedwater pressure stays the same), and the natural osmotic pressure rises until it equals the applied feed pressure. As a result, the driving impact of feed pressure may be negated, resulting in a reverse osmosis process that is slowed or stopped and a decrease or cessation of permeate flow and salt rejection.

Any RO system's maximum percent recovery is often determined by the quantity of salts present in the feedwater and their propensity to precipitate on the membrane, rather than a limiting osmotic pressure.

Result of pH

Different kinds of RO membranes can have quite different tolerances to pH. Thin-film composite (TF)membranes offer higher operational latitude since they are generally stable over a wider pH range than cellulose acetate (CA) membranes. The pH affects the effectiveness of membrane salt rejection. The flow of water may also be impacted. For Thin Film membranes, the water flow and salt rejection are basically constant throughout a wide pH range.

Please call the technical support professionals at Netsol water solutions at +91-9650608473 or mail at enquiry@netsolwater.com if you require any more details, professional advice, application instructions, treating reverse osmosis membranes.