What are some of the terms related to reverse osmosis systems? [Dry Goods]

What are the terms related to reverse osmosis systems?

        With the development of society, people pay more and more attention to water pollution, and reverse osmosis membrane equipment is becoming more and more popular. However, many professional terms are confusing, and it is often difficult to distinguish the differences between these terms. Today, let's learn together.

Reverse Osmosis Membrane: A functional semi-permeable membrane that allows solvent molecules to pass through but not solute molecules 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 pass through is called a nanofiltration membrane;

Membrane Element: The smallest unit that can achieve the separation of feed water and product water in the reverse osmosis or nanofiltration process by assembling the reverse osmosis or nanofiltration membrane sheet with the feed water flow channel grid, product water flow channel material, product water central pipe, and stress resistant device, etc., using adhesives, is called a membrane element;

Membrane Module: Membrane elements are installed in a pressurized pressure vessel shell to form a membrane module;

Membrane Device: A complete set of membrane equipment that can operate independently, consisting of membrane modules, instruments, pipelines, valves, high-pressure pumps, safety filters, on-site control panels, and racks, is called a membrane device. The reverse osmosis and nanofiltration processes are realized through this membrane device;

Membrane System: A complete membrane water treatment process designed for specific water source conditions and water production requirements, including pretreatment, chemical dosing devices, booster pumps, water tanks, membrane devices, and electrical instrument interlocking control, is called a membrane system.

Flow Rate: Flow rate refers to the inflow rate of water into the membrane element, often expressed in m3/h or gpm 。

Concentrate Flow Rate: Refers to the part of the “feed water ” flow rate that does not pass through the membrane element system. This concentrate contains soluble components brought in from the raw water source, often expressed in m3/h or gpm 。

Flux: The flow rate of permeate per unit membrane area, usually expressed in l/m2h or gfd 。

Dilute Solution: The purified aqueous solution, which is the product water of the reverse osmosis or nanofiltration system.

Concentrated Solution: The part of the solution that does not pass through the membrane, such as the concentrated water of the reverse osmosis or nanofiltration system.

Salt Content and Total Solids: Salt content refers to the solids in water that can dissociate into ions. The sum of the cations and anions 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 content 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 (generally using 0.1mol/L HCl standard solution). The alkalinity index is often used to evaluate the buffering capacity of water bodies and the solubility and toxicity of metals in them.

Hardness: Water hardness is divided into carbonate hardness and non-carbonate hardness, and the sum of the two is called total hardness.

Carbonate Hardness: Refers to the salts formed by calcium, magnesium, and other ions with bicarbonate ions in water. Because when water is heated, bicarbonate decomposes into carbonate, the solubility decreases, and precipitation is generated and precipitated. Therefore, it is also called temporary hardness.

Non-carbonate Hardness: Mainly refers to the hardness formed by sulfates, nitrates, and chlorides of calcium and magnesium. Because they do not form precipitates when water is heated to boiling under normal pressure, they are also called permanent hardness.

Conductivity: Conductivity is a numerical representation of the ability of a solution to conduct electricity. Pure water has very low conductivity. When water contains inorganic acids, bases, or salts, the conductivity of the solution increases. Conductivity is often used to indirectly estimate the total concentration of ions in water. The conductivity of an aqueous solution depends on the nature and concentration of ions, the temperature and viscosity of the solution. For every 10℃ 2% increase in temperature, the conductivity increases by about ～2.5% ，usually 25℃ is specified as the standard temperature for measuring conductivity. The standard unit of conductivity is S/m( Siemens / per ) meter ). The commonly used unit is 。

μS/cm ISO International standards define turbidity as the reduction in the transparency of a liquid due to the presence of insoluble matter. The turbidity value and unit obtained differ depending on the turbidity standard solution used in the test.

SDI Value: SDI （ Silt Density Index ）also known as the silt density index（ fouling index ）, is an important indicator characterizing the water quality of the feed water in a reverse osmosis system. Compared with turbidity, it represents water quality from a different perspective, but SDI the value is more accurate and reliable than turbidity. Turbidity measurement uses 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 ORP: Oxidation-Reduction Potential ORP is a parameter that characterizes the amount of oxidizing and reducing substances in water. Oxidation-reduction potential is generally expressed in millivolts（ mV ）. When the oxidation-reduction potential is positive, it indicates that the water contains oxidizing substances; when it is negative, it indicates that the water contains reducing substances.

Organic matter: There are many types of organic matter, and the composition in natural water varies greatly. At present, there is no accurate direct measurement method, and several indicators related to organic matter, such as oxygen consumption, weight loss after incineration of total solid residue, and total organic carbon, cannot accurately represent the content and composition of organic matter.