One-stage reverse osmosis + EDI ultrapure water equipment scheme

1. Design basis and water treatment standards:

1. The external requirements of the system:

  1. Water inlet pipe: The water inlet pipe is connected to the inlet of the original water tank.
  2. Power supply cable: According to the calculated capacity, the user sends the power to the operation control cabinet.
  3. Outlet pipe: to the water point.
  4. Foundation requirements: foundation bearing capacity ≥ 5 tons/square
  5. Wastewater treatment: Discharge to the inner ditch of the workshop (considered by users).
  6. System water temperature: normal temperature.
  7. Floor area: 30 square meters, L*B=6*5.

2. Design basis

  1. Raw water: municipal tap water
  2. Product water use: ultrapure water for LCD
  3. Water production: RO effluent ≥1.25 m3/h; EDI effluent ≥1.0 m3/h
  4. Water quality of effluent: effluent resistivity ≥10MΩ.CM; terminal effluent resistivity ≥17MΩ.CM
  5. System configuration: pretreatment + reverse osmosis desalination + EDI fine desalination + fine mixed bed desalination + terminal treatment
  6. Operation mode: automatic control operation
  7. Design boundary: from the outlet of the original water tank to the point of use
  8. The technical parameters of the equipment meet the “Design Specification for Softening and Desalination of Industrial Water” (GBJ109-87);
  9. The installation and commissioning of equipment shall meet the “Construction Acceptance Specification for Water Supply and Drainage Engineering” (GB1328-1995).
  10. Other involved design basis conditions will be determined in technical discussions

2. the process description

This process includes pretreatment part, reverse osmosis part and EDI part.

1. Composition and purpose of pretreatment and reverse osmosis: Provide qualified influent water for reverse osmosis device.

(1). Reverse osmosis system inlet water requirements:

  1. Pollution index SDI≤4
  2. Free chlorine <0.1 ppm
  3.  Turbidity <1NTU
  4. Water supply Fe3+ ≤0.01ppm
  5. The suitable range of water supply water temperature is 10~30℃
  6. Calcium carbonate saturation index LSI 0

(2). Pretreatment is to make the reverse osmosis influent meet the above requirements through filtration, adsorption, exchange and other methods to achieve the following purposes:

  • Prevent scaling on the reverse osmosis membrane surface (including CaCO3, CaSO4, SrSO4, CaF2, SiO2, iron and aluminum oxides, etc.);
  • Prevent colloidal substances and suspended solid particles from fouling the reverse osmosis membrane;
  • Prevent the fouling and degradation of the reverse osmosis membrane by organic substances;
  • Prevent microbial fouling of reverse osmosis membrane;
  • Prevent oxidative damage to reverse osmosis membrane by oxidizing substances;

(3). The composition of the preprocessing system:

  • Raw water contains a variety of impurities, such as suspended solids, colloids, organic and inorganic substances. In order to remove suspended solids, colloids, organic matters, etc. in the water, mechanical filters, activated carbon filters, softeners, security filters and other devices are installed in the raw water pretreatment part.
  • Mechanical filters and activated carbon columns can effectively remove impurities such as suspended solids, colloids, and organic matter in water, and absorb humus, chroma, odor, residual chlorine, etc. in tap water, which can reduce the turbidity and pollution index of water. The water is clean and has no peculiar smell, which is called clear water. The mechanical filter is filled with anthracite and quartz sand, and the activated carbon filter is filled with high-quality activated carbon. The softener uses sodium ion exchange resin to replace calcium and magnesium ions in the raw water. resin. Shenyang water treatment equipment, Shenyang pure water equipment

2. Raw water pretreatment part:

Raw water contains a variety of impurities, such as suspended solids, colloids, organic and inorganic substances. In order to ensure the normal operation of the reverse osmosis pre-demineralization part of the system, the suspended solids, colloids, organic substances, etc. in the water must be removed first, so that the reverse osmosis influent water meets the requirements, so the system is equipped with a raw water pretreatment part. The raw water pretreatment part includes mechanical filter, activated carbon filter, softener, security filter, PH dosing and other devices.

(1). Mechanical filter:

The reverse osmosis equipment has high requirements on the turbidity of the influent water, especially the pollution index SDI value of the reverse osmosis influent water is required to be less than 4, and the turbidity is less than 1NTU. The filter material in the multi-media filter includes five specifications of quartz sand, which is used to remove the suspended solids in the raw water and the destabilized colloid. It is sent to activated carbon filter and security filter for further treatment as the influent of reverse osmosis equipment.

(2). Activated carbon filter

The reverse osmosis equipment requires that the residual chlorine content of the influent water is less than 0.1mg/l, so the activated carbon filter is used to remove the residual chlorine in the raw water to prevent the reverse osmosis membrane from being polluted. At the same time, it can further adsorb organic matter in raw water. The activated carbon filter is filled with refined shell-type activated carbon, which is used to adsorb residual chlorine, organic matter, some pigments and harmful substances in the raw water, and reduce the chemical oxygen consumption COD. Activated carbon is widely used in the purification of domestic water and industrial water such as food industry and chemical industry. Due to the large specific surface area of ​​activated carbon, its surface is covered with micropores with an average of 20-30 angstroms. Therefore, activated carbon has a high adsorption capacity. ability. In addition, there are a large number of functional groups such as hydroxyl and carboxyl on the surface of activated carbon, which can chemically adsorb organic substances of various properties, as well as electrostatic attraction. Therefore, activated carbon can also remove humic acid, fulvic acid, lignosulfonic acid, etc. Organic substances can also remove substances such as residual chlorine that are harmful to the reverse osmosis membrane and prevent the reverse osmosis membrane from being oxidized. Usually, it can remove 63%-86% of colloidal substances, about 50% of iron, and 47-60% of organic substances. The process of removing residual chlorine from activated carbon is a simple redox process. This process may break the activated carbon, but the broken activated carbon does not affect the effect of removing residual chlorine, so the effect of removing residual chlorine from activated carbon is very strong.

(3). Water softener

The calcium and magnesium ions in the raw water are replaced by sodium ion exchange resin, and the softened water with extremely low hardness flows out through the equipment. When the resin absorbs a certain amount of calcium and magnesium ions, it must be regenerated: soak the resin with saturated brine to replace the calcium and magnesium ions in the resin, restore the softening and exchange capacity of the resin, and discharge the waste liquid. The entire regeneration process includes: backwashing – loosening the resin layer, salt absorption regeneration – exchange reaction, flushing (forward washing) – flushing calcium and magnesium ions exchanged by chemical reaction, water injection – for the next regeneration.

(4). Security filter

The security filter is a microfiltration device, which plays an insurance role in the pretreatment system. When the mechanical filter is not working properly, it is checked to ensure that qualified water supply can be provided under any circumstances, and particles in the water and pipelines can be prevented from entering the water pump and reverse osmosis. The system is specially equipped with a security filter as a filtering device. When the pressure difference between the inlet and outlet of the filter is greater than 0.1Mpa, the filter element needs to be replaced (because the filtered medium directly enters the gap of the microporous membrane, it is difficult to restore the flux through acid-base cleaning). The filter structure can meet the requirements of quick replacement of the filter element.

3. Reverse osmosis desalination part:

The water contains various inorganic salts, which cannot be removed by ordinary filtration. However, traditional ion exchange method is used to remove them, but it faces the problems of large consumption of acid and alkali, short regeneration cycle, high labor intensity of workers and serious environmental pollution. Osmosis technology is an emerging high-tech in the past two decades. It utilizes the principle of reverse osmosis and adopts a reverse osmosis membrane with high selective permeability, which can make the removal rate of inorganic salts in water reach 99%. Therefore, it has the advantages of simple operation, low energy consumption and no pollution, and is widely used in the preparation of pure water.

The composition and function of the reverse osmosis desalination system:

(1) High pressure pump
The setting of the high-pressure pump is to make the reverse osmosis water reach a certain pressure, so that the reverse osmosis process can be carried out, that is, to overcome the osmotic pressure so that the water molecules can pass through the reverse osmosis membrane to reach the fresh water layer.

(2) Reverse osmosis membrane modules and pressure vessels
The reverse osmosis device can remove most of the inorganic salts, particles, bacteria, viruses and other soluble substances in the water.
The reverse osmosis membrane element adopts ESPA2-4040 high-salt-rejection low-pressure membrane produced by American Hyde Energy Company, which is made of aromatic polyamide composite membrane.
The operating conditions of the membrane element are: high temperature 45OC, pH range 2.0-11.0, high operating pressure 4.16MPa, pressure loss 0.07 Map, high pollution index SDI of influent water 5, high influent turbidity 1.0NTU, high influent water The residual chlorine content is 0.1ppm, and the flow ratio of single concentrated water and permeated water is 5:1.
Under normal use, the average service life of the membrane element is 3 years.
The design working pressure of the membrane element is in the range of 1.4-2.2 Map.
The pressure vessel is the shell that provides the working pressure environment for the reverse osmosis membrane element. The stainless steel 4″-1W pressure vessel is used, and the rated working pressure is 300PSI, that is, 2.0Mpa. One pressure vessel can hold one reverse osmosis membrane element.

(3) Automatic flushing device:
During the operation of reverse osmosis, the concentration process and concentration polarization will cause the solid content concentration of the raw water in contact with the membrane surface to be much greater than the bulk concentration of the raw water. Therefore, an automatic low-pressure flushing device is equipped to perform regular low-pressure flushing on the reverse osmosis membrane before starting, after shutting down or continuously running for an adjustable period, and flushing away a small amount of pollutants attached to the membrane surface. After flushing, the system automatically returns to the state before flushing was started. The reverse osmosis device is equipped with an automatic low-pressure flushing protection device made in Germany. When the reverse osmosis is turned on, the device automatically flushes the membrane to ensure that the membrane pollution is reduced to a minimum. Shenyang water treatment equipment, Shenyang pure water equipment

4. EDI refined desalting part:

The fine desalination part consists of a booster pump, a TOC remover, an EDI device, a pure water tank, a variable frequency pure water pump, a fine mixed bed, an ultraviolet sterilizer, and a terminal membrane filter.

(1) TOC remover

The system is equipped with a UV-1T TOC remover, built-in imported UV lamp, wavelength 185nmUV, which can decompose the total organic carbon in RO pure water, and then remove it in the precise screening program.

(2) 0.45μm membrane filter

It is filtered with a 0.45μm microporous folded membrane filter element to remove the fine particles and bacterial corpses that may exist in the ultrapure water. The system is equipped with one MF-1T-01 type microporous membrane filter, with an output of 1T/H.

(3) Booster water pump

The role of the EDI water pump is to deliver qualified RO water to the EDI device.
This system is equipped with 1 pure water pump, and the normal output of the pure water pump is 1m3/h.

(4) EDI device

EDI (Electrodeionization) is removed by exchanging residual salts in RO water with hydrogen ions or hydroxide ions and sending them to a concentrated water stream. The exchange reaction takes place in the module’s purification chamber, where anion exchange resins exchange their hydroxide ions (OH-) for anions (such as chloride ions, Cl-) in dissolved salts. Correspondingly, cation exchange resins exchange their hydrogen ions (H+) for cations (eg Na+) in dissolved salts. A DC electric field is applied between the anode (+) and cathode (-) located at both ends of the module. The electrical potential causes the ions exchanged to the resin to migrate along the surface of the resin beads and through the membrane into the concentrate compartment. The anode attracts negatively charged ions (such as Cl-, OH-), and these ions enter the adjacent concentrated water flow through the anion selective membrane, but are blocked by the cation selective membrane, thereby remaining in the concentrated water flow. The cathode attracts cations (eg Na+, H+) in the concentrated water stream. These ions enter the adjacent concentrated water stream through the cation selective membrane but are blocked by the anion selective membrane and remain in the concentrated water stream. As water flows through these two parallel chambers, ions are removed in the pure water chamber and collect in the adjacent concentrated water flow, which is then carried away from the module by the concentrated water flow.
The use of ion exchange resin in pure water and concentrated water is the key to EDI technology. An important phenomenon occurs in the ion exchange resin in the pure water compartment. In the local area where the potential difference is high, the water decomposed by the electrochemical reaction produces a large amount of H+ and OH-. The local H+ and OH- generation in the mixed-bed self-care exchange resin enables continuous regeneration of the resin and membrane without the addition of chemicals. Shenyang water treatment equipment, Shenyang pure water equipment
Main economic and technical indicators
1) EDI product water resistivity ≥ 15MΩ·cm
2) EDI product water flow rate ≥ 1T/h
3) EDI water utilization rate ≥ 90%
4) EDI service life: 3-5 years

5. Back-end finishing part

(1) Polishing mixed bed

The function of the polishing mixed bed is to further remove the residual cations and anions in the EDI effluent. The polishing resin in the polishing mixed bed adopts the nuclear grade resin produced by the German joint venture, and the effluent resistivity can reach 18MΩ·cm.
The system is equipped with a D200×1200 polishing mixed bed, the bed is made of glass fiber reinforced plastic tank, lined with PE, and the filling volume of polishing resin in a single tank is 30L.

(2) Pure water tank

The EDI produced water has a certain pressure and can enter the pure water tank for temporary storage. The pure water tank is used to store the produced water of the EDI electric regeneration system. The purpose is to ensure the stability of the water supply and water pressure. The liquid level of the water tank controls the start and stop of the ultrapure water pump, and adjusts the flow rate of the produced water in the system.

(3) Frequency conversion pure water pump

The function of the frequency conversion pure water pump is to transport the qualified ultrapure water to the water point at a constant pressure. This system is equipped with 1 ultra-pure water pump, the normal output is 1m3/h, and it is made of 316 material.

(4) Ultraviolet sterilizer

Ultraviolet light is a type of electromagnetic wave. When electrons in atoms jump from high energy level to low energy level, they will release excess energy as electromagnetic waves. The stronger the energy of the electromagnetic wave, the shorter the wavelength, the wavelength that the human eye can see is 400nm-780nm (1nm=10-9m), to the naked eye, the electromagnetic wave of 400nm is displayed in blue and purple, and the electromagnetic wave of 780nm is displayed in orange and red . Ultraviolet rays refer to electromagnetic waves whose wavelengths are shorter than 400 nm. Because their spectrum is outside the violet region, it is called ultraviolet (Ultraviolet, UV for short). Ultraviolet light is an electromagnetic wave with a wavelength of 100-400nm, which cannot be seen by human eyes. Shenyang water treatment equipment, Shenyang pure water equipment
This system is equipped with a UV-1T type ultraviolet sterilizer, built-in imported ultraviolet lamp, wavelength 245nmUV, which can kill microorganisms in ultrapure water, and then remove them in a 0.22U screening program.

(5) 0.22μm membrane filter

It is filtered with a 0.22μm microporous folded membrane filter element to remove fine particles and bacteria present in ultrapure water.
The system is equipped with one MF-01 type microporous membrane filter, with an output of 1T/H.

Xi’an CHIWATEC Water Treatment Technology is a high-tech enterprise specialized in various water processing devices. Aside from these individual products, which cover a number of types and series, we can also help with related comprehensive engineering projects. Thanks to our hard work and dedication upon our founding, we are now one of the fastest-developing water treatment equipment manufacturers in Western China.

Further reading:

RO Plant Water Purification Remove SS TDS

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