Commonly Used Professional Terms in Chemical Water Treatment

Analysis of commonly used professional terms in the field of chemical water treatment:

1. Surface water

Refers to water that exists on the surface of the earth's crust exposed to the atmosphere; it is the collective term for rivers, glaciers, lakes, and swamps, also known as "land water".

2. Groundwater

Is stored in the unsaturated zone (the unsaturated zone refers to the geological medium below the earth's surface and above the water table) including water in rock pores, fissures, and caves. Groundwater exists in the cracks of the earth's crust or soil pores.

3. Raw water

Refers to water collected from nature, including but not limited to groundwater and reservoir water, which is visible in nature and has not undergone any artificial purification treatment.

4. PH

Represents the numerical value of the acidity and alkalinity of a solution, pH = -lg[H+], which is the negative value of the common logarithm of the hydrogen ion concentration.

5. Total alkalinity

The total amount of substances in water that can neutralize strong acids. These substances include strong bases, weak bases, and strong base weak acid salts, etc.

6. Phenolphthalein alkalinity

Is the alkalinity measured using phenolphthalein as an indicator (titration endpoint pH = 8.2～8.4).

7. Methyl orange alkalinity

Is the alkalinity measured using methyl orange as an indicator (titration endpoint pH = 3.1～4.4).

8. Total acidity

Acidity refers to the total amount of substances in water that can neutralize strong bases, including inorganic acids, organic acids, and strong acid weak base salts, etc.

9. Total hardness

In general natural water, it is mainly Ca2+ and Mg2+, the content of other ions is very low, usually the total content of Ca2+ and Mg2+ in water is called the total hardness of water.

10. Temporary hardness

Due to the water containing Ca(HCO3)2 and Mg(HCO3)2, the hardness formed can be removed by boiling. This hardness is called carbonate hardness, also known as temporary hardness.

11. Permanent hardness

Due to the water containing CaSO4 (CaCl2) and MgSO4 (MgCl2) and other salt substances, the hardness formed cannot be removed by boiling. This hardness is called non-carbonate hardness, also known as permanent hardness.

12. Dissolved substances

Exist in the form of simple molecules or ions in water (or other solvents) solutions the particle size is usually only a few tenths to several nanometers, invisible to the naked eye, and there is no Tyndall phenomenon. It cannot be seen with an optical microscope.

13. Colloids

Particle groups formed by the combination of several molecules or ions the size is usually tens of nanometers to tens of micrometers, invisible to the naked eye, but the Tyndall phenomenon will occur. Small colloidal particles cannot be seen with an optical microscope, but large ones can be seen.

14. Suspended solids

Are small particles visible to the naked eye formed by the combination of a large number of molecules or ions the size is usually tens of micrometers or more, and can be clearly seen with an optical microscope. Suspended solids can settle after a long time of standing.

15. Total salt content

The total amount of ions in water is called the total salt content. It is obtained by adding up the amounts of all cations and anions obtained from the complete water quality analysis, and the unit is mg/L (formerly also used PPM).

16. Turbidity

Also known as turbidity. In a technical sense, turbidity is a water quality surrogate parameter used to reflect the content of suspended solids in water. The main suspended solids in water are generally soil. With 1 mg of silicon dioxide in 1 L of distilled water as the unit of standard turbidity, expressed as 1 PPm.

17. Total dissolved solids

TDS, also known as the total amount of dissolved solids, the measurement unit is mg/L (mg/L), which indicates how many milligrams of dissolved solids are dissolved in 1 liter of water.

18. Resistance

According to Ohm's law under a certain water temperature, the size of the water resistance value R is inversely proportional to the vertical cross-sectional area F of the electrode and directly proportional to the distance L between the electrodes.

19. Conductance

The strength of the water's ability to conduct electricity is called conductance S (or conductance).

20. Conductivity

The conductivity of water, which is the reciprocal of the resistance of water, is usually used to indicate the purity of water.

21. Resistivity

The resistivity of water refers to the side length at a certain temperature The resistance between two opposite sides of a 1cm³ cube of water, measured in ohm-centimeters (Ω*CM), is a common parameter for indicating the quality of ultrapure water.

22. Softened Water

Refers to water in which the hardness (mainly calcium and magnesium ions) has been removed or reduced to a certain extent. During water softening, only the hardness is reduced, while the total salt content remains unchanged.

23. Desalted Water

Refers to water in which salts (mainly strong electrolytes dissolved in water) have been removed or reduced to a certain extent. Its conductivity is generally 1.0–10.0 μs/cm, resistivity (25℃) 0.1–1000000 Ω.cm, and salt content is 1.5 mg/L.

24. Pure Water

Refers to water in which strong and weak electrolytes (such as SiO2, CO2, etc.) have been removed or reduced to a certain extent. Its conductivity is generally 1.0–0.1 μs/cm, and resistivity is 1.0–1000000 Ω.cm. Salt content < 1 mg/L.

25. Ultrapure Water

Refers to water in which conductive media have been almost completely removed, and non-dissociated gases, colloids, and organic substances (including bacteria, etc.) have also been removed to a very low level. Its conductivity is generally 0.1–0.055 μs/cm, resistivity (25℃) > 10 × 1000000 Ω.cm, and salt content < 0.1 mg/L. Ideal pure water (theoretically) has a conductivity of 0.05 μs/cm and a resistivity (25℃) of 18.3 × 1000000 μs/cm.

26. Deoxygenated Water

Also called deoxygenated water, it refers to water with dissolved oxygen removed, generally used for boiler water.

27. Ion Exchange

A method of separation that utilizes the different ion exchange capabilities between the exchangeable groups in the ion exchanger and various ions in the solution.

28. Cation Resin

Possesses acidic groups. In aqueous solution, acidic groups can ionize to generate H+, which can undergo ion exchange with cations in water.

29. Anion Resin

Contains alkaline groups that ionize in aqueous solution and undergo ion exchange with anions.

30. Inert Resin

Has no active groups and no ion exchange function. Its relative density is generally controlled between the anion and cation resins to separate the anion and cation resins, avoiding cross-contamination during regeneration and ensuring more complete regeneration.

31. Microfiltration

MF, also known as microporous filtration, belongs to precision filtration. Microfiltration can filter out micrometer- or nanometer-level particles and bacteria in the solution.

32. Ultrafiltration

UF, one of the membrane separation technologies driven by pressure. It aims to separate macromolecules from small molecules, with a pore size between 20–1000 Å.

33. Nanofiltration

NF, a pressure-driven membrane separation process between reverse osmosis and ultrafiltration, with a pore size of several nanometers.

34. Osmosis

Osmosis is the phenomenon of water molecules diffusing through a semipermeable membrane. It occurs from a region of high water molecule concentration (i.e., low concentration solution) to a region of low water molecule concentration (i.e., high concentration solution).

35. Osmotic Pressure

For a semipermeable membrane with different water solution concentrations on both sides, the minimum additional pressure applied to the high-concentration side to prevent water from permeating from the low-concentration side to the high-concentration side is called osmotic pressure.

36. Reverse Osmosis

RO, reverse osmosis uses artificial pressure to force water from a concentrated solution to a low-concentration solution. The RO reverse osmosis membrane has a pore size as small as the nanometer level. Under certain pressure, water molecules can pass through the RO membrane, while inorganic salts, heavy metal ions, organic matter, colloids, bacteria, viruses, and other impurities in the source water cannot pass through the RO membrane.

36. Dialysis

Also known as dialysis. A membrane separation operation driven by concentration difference, utilizing the selective permeability of the membrane to different solutes to achieve separation of solutes with different properties.

37. Electrodialysis

ED, when dialysis is carried out under an electric field, the phenomenon of charged solute particles (such as ions) migrating through the membrane is called electrodialysis.

38. EDI

Also known as continuous electro-deionization technology, it is a pure water production technology that combines ion exchange technology, ion exchange membrane technology, and ion electromigration technology.

39. Recovery Rate

Refers to the percentage of feed water converted into product water or permeate in the membrane system.

40. Desalination Rate

The percentage of total soluble impurities removed from the system feed water through the reverse osmosis membrane, or the percentage of specific components such as divalent ions or organic matter removed through the nanofiltration membrane.

41. Salt Passage Rate

The opposite of the desalination rate; it is the percentage of soluble impurities in the feed water that pass through the membrane. Permeate: purified product water produced by the membrane system.

42. Flux

The flow rate of permeate per unit membrane area, usually expressed in liters per square meter per hour ( l/m²h) or gallons per square foot per day (gfd).

43. Product Water

Purified aqueous solution, the product water of reverse osmosis or nanofiltration systems.

44. Concentrate

That portion of the solution that passes through the membrane, such as the concentrated water of reverse osmosis or nanofiltration systems.