How should reverse osmosis membrane system operate safely and stably?

2020/10/21

Reverse osmosis is a precise membrane liquid separation technology, which can block almost all dissolved salts and organic substances with molecular weight > 100, but allow water molecules to pass through. The retention rate of reverse osmosis membrane is generally more than 98%, which is widely used in the fields of seawater and brackish water desalination, boiler feed water, industrial pure water, drinking water preparation and reclaimed water reuse, and has a wide range of applications.

Reverse osmosis uses the selective separation of materials to realize the separation, purification and concentration of different components of the feed liquid. It differs from traditional filtration in that the membrane can be separated in the molecular range, and this process is a physical process without phase changes and addition of additives. The system has the advantages of good water quality, low energy consumption, no pollution, simple process and simple operation.

Safe and Stable Operation of Reverse Osmosis Membrane System

During the reverse osmosis treatment process, the content of various salts in the permeate (reverse osmosis water) decreases, while the content of various salts in the concentrated water increases sharply, resulting in a large amount of salts exceeding their solubility in water and precipitating, mainly including carbonate, sulfate, phosphate, metal oxide, silicide, etc.

These deposits will adhere to the surface of reverse osmosis membrane, reduce reverse osmosis water yield and desalination rate, increase water production pressure, and even lead to equipment damage. Usually, this kind of problem can be alleviated by adding film scale inhibitor.

Film scale inhibitor is a kind of agent that can disperse insoluble inorganic salts in water, prevent or interfere with the precipitation and scaling of insoluble inorganic salts on the metal surface, and maintain good heat transfer effect of metal equipment.

Its mechanism of action includes chelating solubilization, threshold effect, condensation and dispersion, crystal distortion, regeneration-self-release membrane hypothesis, electric double layer mechanism, etc. The following is a brief introduction to chelating solubilization, threshold effect and crystal distortion:

Chelating solubilization:

This effect means that the scale inhibitor can form stable soluble chelates with cations such as calcium and magnesium in water, thus increasing the allowable concentration of calcium ions and magnesium ions in cooling water and relatively increasing the solubility of calcium and magnesium salts.

Threshold effect:

Adding scale inhibitor (order of magnitude ppm) to water can stabilize calcium ions much higher than stoichiometric ratio in water;

Lattice distortion effect:

During the growth of calcium carbonate microcrystals, if the crystal is adsorbed with scale inhibitor and doped in the lattice, the crystal will be distorted or the stress inside the large crystal will increase, thus making the crystal easy to crack and hindering the growth of deposited scale.

By adding scale inhibitor, reverse osmosis membrane scaling can be effectively prevented, water yield and quality can be improved, membrane cleaning period can be reduced, and safe and stable operation of equipment can be maintained.

Boneng high-efficiency film scale inhibitor

Boneng-membrane scale inhibitor produced by Changlong Technology is an efficient membrane scale inhibitor developed for nanofiltration membrane and reverse osmosis membrane. Compared with scale inhibitors on the market, it has good scale inhibition performance, can effectively control scaling of carbonate, sulfate, phosphate, metal oxides and other substances, has a wide scale inhibition spectrum, is effectively applied to scale inhibition treatment of various reverse osmosis membrane equipment, improves equipment operation time, and reduces operation energy consumption and water consumption.