Glossary
Reverse Osmosis
Reverse osmosis is a membrane separation operation that uses pressure difference as a driving force to separate solvents from a solution.
Apply pressure to the liquid on one side of the membrane, and when the pressure exceeds its osmotic pressure, the solvent will undergo reverse osmosis in the direction of natural osmosis.
Thus, the solvent that permeates through the low-pressure side of the membrane, namely the permeate, is obtained;
The concentrated solution is obtained on the high-pressure side, namely the concentrated solution.
If reverse osmosis is used to treat seawater, fresh water is obtained on the low-pressure side of the membrane, and brine is obtained on the high-pressure side.
Reverse Osmosis Membrane
An artificial semi permeable membrane with certain characteristics made by simulating biological semi permeable membranes is the core component of reverse osmosis technology.
The principle of reverse osmosis technology is to separate substances from water based on the fact that other substances cannot pass through a semi permeable membrane under the action of a pressure higher than the osmotic pressure of the solution.
The pore size of reverse osmosis membrane is very small, so it can effectively remove dissolved salts, colloids, microorganisms, organic matter, etc. from water.
The system has the advantages of good water quality, low energy consumption, no pollution, simple process, and easy operation.
Raw Water
It refers to untreated natural water or urban tap water, etc.
Water Production Rate
The production capacity of a reverse osmosis system, which refers to the amount of water that passes through the membrane per unit time, is usually expressed in tons per hour (t/h) or gallons per day (g/d).
Recovery Rate
The ratio of the flow rate of product water produced by the system to the inflow flow rate.
Desalination Rate
The parameters that reflect the performance of the membrane, usually the desalination rate of the first stage RO membrane system is above 97%.
It can be simply calculated as: (conductivity of raw water – conductivity of product water)/conductivity of raw water.
TDS Value
Total Dissolved Solids (TDS) refers to the total content of dissolved solids in water, which is commonly used to measure the water quality of source water. The measuring tool is a TDS pen, and the measurement principle is actually to indirectly reflect the TDS value by measuring the conductivity of water.
The more soluble solids dissolved in water, the higher its TDS value and the higher its conductivity. Typically, the TDS value is about half of the conductivity test value.
Note: TDS value and water salinity (also known as mineralization) are two different concepts. TDS value is usually greater than water salinity because TDS not only includes the dissolved salt content of water, but also dissolved organic matter.
Only when the water is clean and the organic matter content is low, can TDS value be used to approximate the salt content (or mineralization) of water. Overall, TDS value, mineralization, and salinity are directly proportional to the water content.
Saltness
The salt content of water, also known as mineralization, refers to the amount of salts present in the water.
Due to the fact that various salts in water generally exist in the form of ions, the salt content can also be expressed as the sum of the amounts of cations and anions in water.
Pure water
Refers to the removal of strong electrolytes such as silica and carbon dioxide that are easy to remove from water, as well as weak electrolytes that are difficult to remove, to a certain extent.
The salt content of pure water is below 1.0mg/L, and the conductivity is less than 3 μ s/cm.
Ultrapure water
Also known as high-purity water, it refers to water in which almost all conductive media are removed from the water, and colloidal substances, gases, and organic matter that do not dissociate from the water are removed to a very low degree,.
The salt content of ultrapure water is below 0.1mg/L, and the conductivity is less than 0.1 μ s/cm.
turbidity
Due to the presence of suspended and colloidal particles in water, turbidity occurs, and the degree of turbidity is called turbidity (in degrees). The turbidity level of 1 liter of water containing 1mg of SiO2 (silicon dioxide) is 1 degree, and the turbidity requirement for national standard drinking water is less than 5 degrees.
Hardness
The hardness of water refers to the content of metal salts such as calcium and magnesium dissolved in water (with calcium salts accounting for about 85%, magnesium salts 10-15%, and other metal salts 1-3%), mainly referring to the content of Ca2+and Mg2+ions in water. The Ca2+/Mg2+in water mainly comes from the dissolution of calcium and magnesium salts (CaCO3/MgCO3) in rocks. When there is a high content of CO2 gas in water, the dissolution process will be greatly accelerated.
Hardness is divided into temporary hardness (carbonate hardness can be removed by heating precipitation) and permanent hardness (non carbonate hardness, cannot be removed by heating boiling), and the sum of the two is called total hardness.
The hardness unit for international water is German hardness. One liter of water contains 10mg of CaO (calcium oxide), which is equivalent to 1 German hardness. Water with a hardness greater than 8 degrees (equivalent to 200ppm) is considered hard water.
SDI
Pollution index – used to measure the amount of suspended solids in the raw water used in reverse osmosis systems
Flocculant
An agent that can cause coagulation bridging and flocculation of colloidal particles.
Scale inhibitor
It is a type of agent that can disperse insoluble inorganic salts in water, prevent or interfere with the precipitation and scaling of insoluble inorganic salts on metal surfaces, and maintain good heat transfer performance of metal equipment.