1. Common Basic Concepts 1 Conductivity: The number of ions that can move between two electrodes with an area of one square centimeter each and a distance of one centimeter apart, called conductivity, in µ s/cm.

2. Resistance: The reciprocal of conductivity, in M Ω • cm.

3. Hardness: Refers to the content of calcium and magnesium ions in the water source, usually expressed in particles per gallon (gpg).

4. pH value: The relative content of acid and alkali in the solution. The pH value is a unit of measurement of the negative logarithm (log) of hydrogen ion concentration in water. The pH value is divided into 0-14 levels, and a pH value of 7.0 indicates that water is neutral; If the pH value is less than 7.0, water is acidic; The pH value is greater than 7.0. Then water is alkaline.

5. Total solids (TS): refers to the sum of total dissolved solids (TDS) and total suspended solids (TSS).

6. Alkalinity: a general term used to describe the content of carbonate, Bicarbonate and hydroxide.

7. Total organic carbon (TOC): Total organic carbon (TOC) is the measurement unit of organic pollution in water in mg/l. TOC is the direct unit of measurement for oxidizable organic matter.

8. Activated carbon: Granular activated carbon used to remove odors, odors, chlorine gas, chloramine, and some organic compounds from water.

9. NTU: Scattered turbidity unit - measure the turbidity of low turbidity water using a scattering turbidity meter by passing a beam of light through the sample water.

10. Permeation: water flows naturally from the low concentration solution side to the high concentration solution side through the Semipermeable membrane until the energy reaches equilibrium.

11. SDI: Sand Density Index - used to measure the amount of suspended solids in the raw water used in the reverse osmosis system.

12. Resin: A specially manufactured polymer ball used in ion exchange systems to remove dissolved salts from aqueous solutions.

13. LSI: Langelier Saturation Index - A calculation formula used to predict calcium carbonate precipitation under specified conditions, temperature, pH value, TDS, hardness, and alkalinity.

14. Endotoxin: An antipyretic pyrogenic substance, especially a fatty polysaccharide found in the cell walls of living or inanimate bacteria.

15. Ozone: An unstable and highly active form of oxygen, which is generated by natural lightning or high-voltage charges passing through the air and is an excellent oxidant and disinfectant.

1. Basic treatment process 1. Precipitation

Precipitation is usually a multi-step process used to reduce turbidity and suspended solids in water. This multi-step process involves adding chemical coagulants or pH regulators to react to form flocs, which settle in the settling bucket due to gravity or filter out when water passes through a height difference filter. The precipitation process can effectively remove particles larger than 25 µ m.

2. Lime soda softening

The method of adding lime (CaO) and soda powder (Na2CO3) to water to reduce its calcium and magnesium content is called lime softening method. The goal is to precipitate Calcium hydroxide and Magnesium hydroxide (hardness) in water. This process costs less, but the effect is barely satisfactory. The hardness of the water usually produced is 50-120ppm (3-7gpg). The disadvantage of this process is that the pH value of the treated water is high, usually in the range of 8.5~10.0.

3. Mechanical filter (multi medium filter)

A mechanical filter is a pressure vessel filled with a specified thickness of filter material. When filling a single filter material, it is a single-layer mechanical filter, and when filling different types of filter materials, it is a double-layer or multi medium filter.

Function: In the water quality pre-treatment system, quartz sand with different particle sizes in the pressure vessel of the multi medium filter is filled in a certain level. The flocculated raw water passes through the filter material layer from top to bottom under a certain pressure, thereby intercepting and removing suspended solids in the water. The multi medium filter can effectively remove suspended solids, small particles, full valent iron and colloids, bacteria, algae, and organic matter in the raw water. Its effluent SDI15 (pollution index) is less than or equal to 5, which fully meets the inflow requirements of the reverse osmosis device.

The resin column of the soft water equipment contains treated ion exchange resin - polystyrene small particles. This resin particle initially adsorbs sodium ions during the regeneration process, and this resin has a much greater affinity for multivalent ions such as calcium and magnesium ions. Therefore, when hard water flows through the resin, calcium and magnesium ions will adsorb on the resin, while also desorbing ions until reaching an equilibrium state. At this point, the soft water equipment completes the exchange of sodium ions with calcium and magnesium ions in the water.

During regeneration, the NaCl solution flows through the resin, and hard ions are replaced with sodium ions. The use of high concentration salt water weakens the affinity between the resin and hard ions. This regeneration process can be infinitely repeated without damaging the resin.

Softeners are a simple ion exchange process that solves the extremely common form of water pollution: hardness. Using NaCl for regeneration is a simple but not expensive process that can achieve automatic regeneration without the need for strong chemical reagents.

4. Anion and cation exchangers

The anion and cation exchangers are exchangers filled with anion resin and cation resin respectively. Cation exchangers are used to remove positively charged ions (cations), while anion resins are used to remove negatively charged ions (anions).

Cation exchange resins replace H+ions with cations, such as calcium, magnesium, and sodium ions; Anion exchange resins replace OH ions with anions, such as chloride ions, sulfate ions, and bicarbonate ions. The replaced H+and OH - are synthesized to form water and remove ions from the water.

The exchange capacity of resin is limited, and regeneration must be carried out after its exchange capacity is depleted. When the exchange capacity is depleted and the adsorption ions reach an equilibrium state, the regeneration of cationic resin is treated with acid, usually using hydrochloric acid for regeneration, that is, filling with H+ions. The regeneration of anion resin generally uses sodium hydroxide, that is, OH ion filling. Regeneration can be carried out outside the column using regenerated exchange column deionization equipment, or inside the column by installing renewable deionization equipment, regeneration equipment, and chemical agents.

5. Mixed bed

Mixed bed is the abbreviation for mixed ion exchange column, which is a device designed for ion exchange technology. The so-called mixed bed refers to the mixing and filling of a certain proportion of cation and anion exchange resins in the same exchange device to exchange and remove ions from the fluid. Due to the higher specific gravity of the cation resin compared to the anion resin, the anion resin in the mixed bed is higher than the cation resin. The general filling ratio of cation and anion resins is 1:2, and there are also filling ratios of 1:1.5, which can be considered and selected according to different resins.

Mixed beds are also divided into internal synchronous regeneration mixed beds and external regeneration mixed beds. The synchronous regeneration mixed bed is operated and the entire regeneration process is carried out inside the mixed bed. During regeneration, the resin does not move out of the equipment, and both the cation and anion resins are regenerated at the same time. Therefore, it requires less auxiliary equipment and is easy to operate, with the following advantages:

(1) The effluent quality is excellent, and the pH value of the effluent is close to neutral.

(2) The effluent quality is stable, and changes in short-term operating conditions (such as inlet water quality or components, operating flow rate, etc.) have little impact on the effluent quality of the mixed bed.

(3) Intermittent operation has little impact on the effluent quality, and the time required to recover to the water quality before shutdown is relatively short.

(4) The exchange endpoint is obvious.

6. EDI

EDI works by exchanging hydroxyl ions or Hydroxide ion ions to remove unwanted ions, and then transport these ions to the waste water flow. The ion exchange reaction is carried out in the purification chamber of the module, where the anion exchange resin releases Hydroxide ion ions (OH -) and obtains anions from dissolved salts (such as chlorides and Cl -). Similarly, cation exchange resins release hydrogen ions (H+) and obtain cations from dissolved salts such as sodium and Na+.

A direct current (DC) electric field is applied through the anode (+) and cathode (-) placed at one end of the component. The voltage drives these absorbed ions to move along the surface of the resin ball and then pass through the thin film into the concentrated water chamber.

Negatively charged anions (such as OH -, Cl -) are attracted to the anode (+). These ions pass through the anion selective film and enter adjacent concentrated water chambers, without passing through the adjacent cation selective film and remaining in the concentrated water chamber, and are properly treated. Positive cations (such as H+, Na+) are attracted to the cathode (-) in the freshwater chamber. These ions pass through the cation selective film and enter the adjacent concentrated water chamber, where they are blocked by the adjacent anion selective film and properly treated.

In the concentrated water chamber, the electrical neutrality is still maintained. Ions transported from two directions neutralize each other. The current flowing from the power supply is proportional to the number of moving ions. Both streams of water (H+and OH -) trend ions are transported and added to the required current.

When water flows through two different types of chambers, the ions in the purification chamber are depleted and collected into adjacent concentrated water streams, which removes the removed ions from the components.

The use of ion exchange resins in purification and/or concentrated water chambers is a key aspect of EDI technology and patents. An important phenomenon also occurs in the purification room, where electrochemical "decomposition" can produce a large amount of H+and OH - ions in specific areas with high potential gradients. The H+and OH - ions generated in these regions can continuously regenerate the resin in a mixed ion exchange resin and form a thin film without the need for additional chemical reagents.

7. Reverse osmosis system

Reverse osmosis is a type of side flow filtration in which raw water passes through a membrane under pressure, with some of the raw water penetrating the membrane while the rest flows out of the system along the tangent direction of the membrane without being filtered. The filtered water flow is called "permeate water" due to its infiltration through the membrane; Another stream of water is called "concentrated water" because it carries away the concentrated pollutants blocked by the membrane. Because the raw water flow and concentrated water flow are parallel to the membrane, rather than perpendicular to the membrane, this process is called "side flow" or "tangential flow".

Reverse osmosis is the most widely used membrane separation process that utilizes pressure to allow water to penetrate the membrane, while soluble salts, colloids, organic matter, and microorganisms are trapped on the membrane surface and discharged with concentrated water. It can effectively remove all organic matter and 90%~99% ions.

8. Activated carbon filter

Activated carbon filter pressure vessel is a pressure vessel filled with coarse quartz sand cushion and high-quality activated carbon.

Function: In the water quality pre-treatment system, the activated carbon filter can adsorb residual chlorine that cannot be removed in the previous stage of filtration to prevent the oxidation and degradation of the subsequent stage reverse osmosis membrane. At the same time, it also adsorbs small molecule organic matter and other polluting substances leaked from the previous stage, and has a significant adsorption and removal effect on odor, colloids and pigments, heavy metal ions, COD, and other pollutants in the water. It can further reduce the SDI value of RO inlet water to ensure SDI< 5, TOC< 2. Oppm.

9. Softener

The ion exchange softening device is the most commonly used equipment in the water treatment process, which is used to remove calcium and magnesium ions that form scale in hard water. In many cases, the use of softened water equipment can remove soluble ions (iron ions). The standard soft water equipment has four main parts: resin column, resin, salt adding device, and valve controller.