[Hongjie Water] Basic knowledge of reverse osmosis | Related terms

Reverse osmosis membrane: A functional semi permeable membrane that allows solvent molecules to penetrate but does not allow solute molecules to penetrate is called a reverse osmosis membrane;

Nanofiltration membrane: A functional semi permeable membrane that allows solvent molecules or certain low molecular weight solutes or low valent ions to penetrate is called a nanofiltration membrane;

Membrane element: The smallest unit that can achieve the separation of inlet and outlet water in the reverse osmosis or nanofiltration process by assembling the reverse osmosis or nanofiltration membrane membrane with the inlet flow channel grid, the production flow channel material, the production center pipe, and the stress resistance device using adhesives, is called a membrane element;

Membrane component: The membrane component is installed inside the shell of a pressure vessel under pressure to form a membrane component;

Membrane device: A complete set of membrane equipment consisting of membrane components, instruments, pipelines, valves, high-pressure pumps, security filters, local control panels, cabinets, and racks that can operate independently is called a membrane device. The reverse osmosis and nanofiltration processes are achieved through this membrane device.

Membrane system: A complete membrane water treatment process designed for specific water source conditions and production requirements, controlled by pre-treatment, dosing device, booster pump, water tank, membrane device, and electrical instrument interlocking, is called a membrane system.

Flow rate: Flow rate refers to the inlet flow rate of the membrane element. Usually expressed in m ³/ H or gpm.

Concentrated water flow rate: refers to the "inlet" flow rate of the non permeable part of the membrane leaving the membrane element system. This portion of concentrated water contains soluble components brought in from the raw water source, usually expressed in m ³/ H or gpm.

Flux: The flow rate of liquid passing through a unit membrane area, usually expressed in 1/m ² H or gfd.

Dilute solution: Purified aqueous solution, produced by reverse osmosis or nanofiltration systems.

Concentrated solution: The portion of solution that does not penetrate the membrane, such as concentrated water from reverse osmosis or nanofiltration systems.

Salt content and total solids: Salt content refers to solids that can dissociate into an ionic state in water, and the sum of their anions and cations is called salt content. The conductivity and resistance of water are related to the salt content. Generally, the higher the salt content, the higher the conductivity and the lower the resistance. Acidity: Acidity refers to the amount of acidic substances in water that can react with strong bases (such as NaOH, KOH).

Alkalinity: Alkalinity refers to the content of alkaline substances in water that can react with strong acids (usually 0.1moI/L HCI standard solution). Alkalinity indicators are commonly used to evalsuate the buffering capacity of water bodies and the solubility and toxicity of metals in them.

Hardness: The hardness of water is divided into two types: carbonate hardness and non carbonate hardness, and the sum of the two is called the total hardness.

Carbonate hardness: refers to the salt composed of calcium, magnesium plasma, and bicarbonate ions in water. Due to the heating of water, bicarbonate decomposes into carbonate, and its solubility decreases, resulting in precipitation and precipitation. Therefore, it is also known as temporary hardness.

Non carbonate hardness: mainly refers to the hardness formed by sulfates, nitrates, and chlorides of calcium and magnesium. Due to the fact that water is heated to boiling under normal pressure, it does not generate precipitation, hence it is also known as permanent hardness.

Conductivity: Conductivity is the ability of a solution to conduct current in numerical terms. The conductivity of pure water is very low, and when the water contains inorganic acids, bases, or salts, the conductivity of the solution increases. Conductivity is commonly used to indirectly estimate the total concentration of ions in water. The conductivity of an aqueous solution depends on the properties and concentration of ions, as well as the temperature and viscosity of the solution. For every 10 ℃ increase in temperature, the conductivity increases by about 2%~2.5%, usually at 25 ℃. The standard temperature for measuring conductivity. The standard unit of conductivity is S/m (i.e. Siemens per meter)

Turbidity: The ISO international standard defines turbidity as the decrease in liquid transparency caused by the presence of insoluble substances. The turbidity values and units obtained vary depending on the turbidity standard solution used in the test.

SDI value: SDI (Silt Density Index), also known as the sludge density index, is an important indicator that characterizes the inlet water quality of the reverse osmosis system. Compared to turbidity, it represents water quality from different perspectives, but SDI values are more accurate and reliable than turbidity. The determination of turbidity is achieved by using spectrophotometry or visual turbidimetry to determine the content of particulate impurities in water, but it cannot accurately measure some non photosensitive colloidal particles in water.

Oxidation-reduction potential 0RP: The oxidation-reduction potential ORP is a parameter that characterizes the amount of oxidizing and reducing substances in water. The redox potential is generally measured in millivolts (mV). When the redox potential is positive, it indicates the presence of oxidizing substances in the water. When the redox potential is negative, it indicates the presence of reducing substances in the water.

Organic matter: There are various types of organic matter, and their composition in natural water is ever-changing. Currently, there is no accurate direct measurement method, and several indicators related to organic matter, such as oxygen consumption, weight loss on ignition of total solid residue, and total organic carbon, cannot accurately represent the content and composition of organic matter.