Favorite version! Complete Analysis of Knowledge Points in Classical Water Treatment

Favorite version! Complete Analysis of Classical Water Treatment Knowledge Points: 1. Several Basic Concepts in Water Treatment Systems: TDS, SDI, LSI, KSP

Answer:

TDS: Total dissolved solids (generally similar to mineralization)

SDI: The pollution index is an indicator that measures the pre-treatment effect of the system, with an SDI<6.7. For deep well water, the reverse osmosis device requires an inlet SDI<5.

LSI: Langelier Saturation Index, which measures the scaling tendency of reverse osmosis devices. If LSI=0, the system has no scaling or corrosion tendency; LSI>0, system tends to scale; LSI<0, the system has a tendency for corrosion. For reverse osmosis systems, the LSI value is required to be no greater than 0. The LSI value of the system can be reduced by adding acid or by reducing the water recovery rate of the system.

Ksp: solubility Equilibrium constant, the reverse osmosis device selectively penetrates the solvent and solute in the raw water, and concentration occurs due to the reduction of solvent at the concentrated water side. When the concentration product of dissolved solids at the concentrated water side is greater than the solubility Equilibrium constant, it will crystallize and precipitate, bringing harm to the reverse osmosis device. The Equilibrium constant of solubility of the system can be increased by adding scale inhibitor, which can increase the solubility of dissolved solids.

How can the 2LSI index be effectively controlled?

Answer: To effectively control the system's LSI index, the following aspects can be taken into account:

1. The system's LSI index can be reduced by reducing the system's water recovery rate.

2. The system LSI index can be reduced by adding acid.

3. The solubility of dissolved salts in the system can be increased by adding corresponding agents, such as TRISPE1000 scale inhibitor.

4. It is possible to reduce or pre remove easily structured ions in the water, such as softening the system inlet water through a softening column.

What pre-treatment equipment do you know? Answer: The pre-treatment equipment includes: mechanical filter, fiber filter, activated carbon filter, precision filter, ultrafiltration, microfiltration, sodium ion softener, iron and manganese removal filter, dosing device, raw water tank, and aeration tank.

What are the pre desalination equipment you know of?

Answer: Pre desalination equipment includes Electrodialysis device and reverse osmosis device.

Electrodialysis device

Reverse osmosis device

What are the deep desalination equipment you know of? Answer: Deep desalination equipment includes anion exchangers, cation exchangers, mixed ion exchangers, distillation units, and EDI units

How is the selection of 64 mechanical filters? What is its working principle?

Answer: The selection of mechanical filters is based on the total water inflow of the system to choose the size and combination method of the filters (if one mechanical filter is not enough, multiple parallel connections and backup quantities can be selected). The filler inside the mechanical filter is composed of many different particle sizes of refined quartz sand strictly arranged in order of size, thus forming a good quartz sand grading.

When a filter is first put into use, its filtering effect is often not very good because it does not form a "bridging" at the beginning. The so-called "bridging" refers to a interception network composed of suspended solids in water, which intercepts suspended solids of the same particle size, and then intercepts smaller suspended solids, forming a reverse particle filtration process that first intercepts large particulate matter and then intercepts small particulate matter. Once the filter forms a "bridge", the filtering effect is very good. As the operation time increases, the filtering accuracy becomes higher, the interception net becomes thicker, and the inlet and outlet pressure difference becomes larger. When the pressure difference reaches 1kg/cm2, the filter should be backwashed. During the backwashing process, compressed air should be equipped to scrub the quartz sand. General engineering experience is that mechanical filters with a diameter less than 2500mm do not need compressed air; Mechanical filters with a diameter greater than 2500mm must be scrubbed with compressed air to achieve satisfactory cleaning results; The backwash flow rate is generally 3-4 times the design capacity of the filter.

Quartz sand filter

Activated carbon filter

Fiber ball filter

Multi media filter

Fiber bundle filter

How are precision filters selected? How many methods are there for filter cartridges?

Answer: The selection of precision filters is matched with the total water inflow, and the diameter of the precision filter is selected based on the total water inflow. For a filter element with a filtration accuracy of 40 "5um, the water yield per unit is approximately 2m3/h.

The types of filter elements roughly include polypropylene filter elements, honeycomb filter elements, spray melt filter elements, folding filter elements, etc.

How to remove iron from water? Answer: The iron in groundwater is generally ferrous, so ferrous must be oxidized to ferric. The oxidation process is completed through aeration. The aeration device fully contacts the water with oxygen to produce Autoxidation; The aerated water undergoes the iron removal process through a iron and manganese removal filter. If most of the iron in the water is trivalent iron, it does not need to be aerated and directly enters the iron and manganese removal filter for removal.

Why do some water types need to be equipped with a carbon dioxide remover after passing through a cation exchanger?

Answer: The exchange of metal ions in water with H+ions on the cation resin results in H+ions entering the water. Therefore, the effluent of the cation exchanger is slightly acidic, causing most of the HCO3- in the water to be converted into H2CO3 and further into CO2 gas. Due to the low solubility of CO2 gas, it provides good conditions for degassing, and if degassing is not carried out, H2CO3 will be exchanged with the anion exchange resin, This increases the burden on the anion exchanger and shortens its water production cycle.

Usually, the carbon dioxide remover is placed after the cation exchanger, before the anion exchanger, and also before some pre desalination systems such as reverse osmosis. However, in some places, a carbon dioxide remover is not needed, all of which depend on the water quality and type of the user.

How many ways are there to prevent corrosion? Answer: There are various anti-corrosion methods such as rubber lining, epoxy, plastic lining, enamel, etc.

What are the main components of the 11 reverse osmosis device? Answer: The reverse osmosis device mainly consists of a high-pressure pump, a high-pressure pump outlet gate valve (manual or electric), a high and low pressure protection switch, an inlet flow meter (also optional), a permeate flow meter, a concentrated water flow meter, a permeate conductivity meter, membrane components (pressure vessels, reverse osmosis membrane components), a concentrated water electric valve, a concentrated water shut-off valve, an inlet pressure gauge, an inter section pressure gauge, a concentrated water pressure gauge, a concentrated water pressure gauge, a reverse osmosis support, and a reverse osmosis control panel Reverse osmosis sampling disk, rupture membrane, and corresponding pipelines, clamps, elbows, etc.

What types of instruments and meters must be used in the reverse osmosis system?

Answer: There are several necessary instruments and meters in the reverse osmosis system:

1. Pollution index meter: used to measure the SDI index of system preprocessing.

2. Concentrated water flow meter: used to measure the flow rate of concentrated water in the system, and used in conjunction with the production water flow meter to determine the system recovery rate.

3. Water flow meter: used to measure the flow rate of water produced by the system. Production water conductivity meter: used to measure the water quality (conductivity) of the system's production water

4. Pressure gauge: measures the inlet pressure, inter section pressure, concentrated water pressure, and produced water pressure of the system.

5. Inlet flow meter: used to measure the total inlet flow rate of the system.

6. Thermometer: used to measure the temperature at which the system operates.

7. Water inlet pH meter: used to measure the changes in the pH value of the system's water inlet.

8. Water inlet conductivity meter: used to measure the conductivity of the system's water inlet, and used in conjunction with the conductivity of the produced water to determine the desalination rate of the system.

9. Oxidation-reduction instrument: used to measure the amount of oxidizing substances in the system's inlet water to determine the degree of threat to system safety.

10. High and low voltage protection switch: used to protect the system from operating under low pressure (insufficient water supply) and high pressure conditions.

A reverse osmosis system is relatively complex, and the instruments and meters used are determined by process requirements and user investment. A normal reverse osmosis system only requires a production water flow meter, concentrated water flow meter, production water conductivity meter, pressure gauge, and high and low pressure protection.

13 What are the components of the Electrodialysis device? What are the characteristics and functions of each part?

Answer: The Electrodialysis device is composed of several parts: negative membrane, positive membrane, partition, electrode, clamping device, leak proof rubber plate, pickling system, flowmeter, pressure gauge, ABS pipe fittings, valves, and silicon controlled rectifier cabinet.

The selective permeability of anionic and cationic membranes to ions in water makes the system divided into concentrated water, fresh water, and polar water, which is the desalination part of the device.

The main material of the partition is polypropylene, which supports the amniotic membrane and forms a concentrated fresh water chamber with it.

The electrode mainly forms the electric field required for ion exchange membranes. The electrode is composed of a cloth head, a porous plate, and a PVC frame.

The clamping device mainly fixes the anion and cation exchange membrane, electrode, separator, etc. to form a whole.

The leak proof adhesive plate is located between the electrode and the partition, which prevents the system from leaking water at the edge of the electrode.

The pickling system is an indispensable part of the entire device. When the Electrodialysis device has abnormal phenomena such as the decrease of desalting rate, the decrease of water yield, the rise of operating pressure, etc., it is necessary to judge the reason why the system is formed by scaling, inorganic fouling, organic fouling, etc. and take corresponding chemical agents for chemical cleaning.

The thyristor rectifier cabinet is the energy feeding part of the device, which rectifies the power frequency AC power into a voltage adjustable DC voltage through the thyristor rectifier device. It is added to the electrode to form a DC electric field inside the membrane stack to traction the anions and cations in the solution to generate directional movement. The main parameters of the thyristor rectifier cabinet are: rectification voltage, working current, and rectification power. Flowmeter, pressure gauge, ABS pipe fittings and valves are accessories of Electrodialysis, which play the role of displaying various operating parameters of Electrodialysis device, connecting water chamber and switching water flow direction.

What are the advantages and disadvantages of Electrodialysis?

Answer:

The advantages of Electrodialysis are:

Low energy consumption and small footprint.

2. Simple operation and low noise.

The effluent quality is stable and there is no phase change during the desalination process.

4. Low pollution to the environment.

The application range of 5 is relatively wide, ranging from 200-40000mg/h.

The disadvantages of Electrodialysis are:

The installation is relatively complex.

The desalination effect is generally 75% if it is not thorough.

The low water recovery rate is generally 50%.

15 What is the desalting principle of Electrodialysis? Answer: The anion and cation exchange membrane in the Electrodialysis device has selective permeability. When the ions in the solution move directionally under the action of an electric field, concentrated water or fresh water is formed in different water chambers by using the selective permeability of the anion and cation exchange membrane or not through the corresponding exchange membrane.

What is the distribution ratio of Electrodialysis concentrated water, dilute water and extreme water? Answer: The distribution ratio of concentrated water, fresh water and polar water in the Electrodialysis device is about 4:4:2, so it is very meaningful to save polar water in the Electrodialysis desalination system; Commonly used measures to save extreme water include using some concentrated water as extreme water for discharge or using extreme water circulation; The specific method of polar water circulation system is to use softened water or desalinated water+NaCL solution as polar water circulation.

How to Choose a Good Anionic and Anionic Heterogeneous Ion Exchange Membrane

Answer: A high-quality heterogeneous ion exchange membrane must have the following characteristics:

1. Choose to have strong permeability. The selective permeability is the main index to measure the performance of the membrane. It directly affects the current efficiency and desalination effect of the Electrodialysis device, and its selective permeability is more than 85%.

2. Low film resistance. The Electrodialysis device consists of hundreds of pairs of ion exchange membranes, so the membrane resistance accounts for a large proportion of the total resistance. If the resistance is small, the operating voltage is low and the current efficiency is high.

3. Strong chemical stability. During the migration of anions and cations, a concentrated ion solution is formed in the concentrated water chamber; When polarization occurs, the PH value of the retention layer on both sides of the membrane will also change, especially when extreme water takes part in the chemical reaction, it will produce highly oxidizing oxygen and chlorine, so the membrane must have strong chemical stability to extend the service life of the Electrodialysis.

4. Strong mechanical strength and dimensional stability.

5. Lower diffusion performance.

6 pairs of strong electrolytes have high removal efficiency.

What material is the electrode of Electrodialysis made of? What are the specifications? What are the advantages and disadvantages of each?

Answer: The electrodes of Electrodialysis are divided into several types: titanium plated platinum electrode, titanium coated ruthenium electrode, graphite electrode, stainless steel electrode; The electrode varies according to the size of Electrodialysis body. Common engineering electrode specifications are 800 × 1600mm, 400 × 1600mm, 400 × 800mm, 340 × 640mm, etc.

Different electrode materials have different characteristics:

Titanium plated platinum electrode: It has excellent corrosion resistance and can be used under very harsh conditions, but the expensive price and limited resources of platinum limit its promotion in China.

Titanium coated ruthenium electrode: a compound of ruthenium (Ru), iridium (Ir), and titanium (Ti) is coated on a titanium substrate, and its mixed oxide is formed after high-temperature treatment; Since the Ionic radius of ruthenium (Ru), iridium (Ir) and titanium (Ti) are very close, and the lattice structure and Space group belong to the same type, the Solid solution of RuO2-IrO2-TiO2 can be formed during the co oxidation of heat treatment, which has excellent corrosion resistance and is very suitable for use as electrode materials.

Graphite electrodes: Graphite electrodes are prone to corrosion, mainly due to chemical corrosion and mechanical wear; When graphite is used as anode, due to anodic oxidation, graphite is oxidized to CO2 or CO, so that its crystal structure is damaged; In the Electrodialysis device, the loss of graphite electrode is mainly caused by mechanical action. The high flow rate of polar water has a strong scouring effect on graphite. On the other hand, the gas generated by electrode reaction has an impact on graphite. Combined with electrochemical corrosion, it often causes the graphite particles to peel off, pollute the water quality and even block the polar water channel; With the emergence of titanium coated ruthenium electrodes, graphite electrodes have gradually been phased out.

Stainless steel electrode: Generally speaking, stainless steel is only used as a cathode and cannot be used as an anode. Otherwise, due to the high content of chloride ions in natural water, it will cause the anodic dissolution of stainless steel to generate divalent iron, nickel, and chromium ions.

The correct selection of electrode materials is of great significance for extending the service life of the electrode, reducing system investment and operating costs. Different materials of electrodes can be selected for different water quality:

1. Titanium coated ruthenium electrodes can be preferred for natural water mainly composed of chlorides.

2. For natural water with sulfate as the main component, lead plate, stainless steel, and titanium coated ruthenium electrodes can be preferred.

3. For natural water mainly composed of calcium bicarbonate, stainless steel and titanium coated ruthenium electrodes can be preferred.

4. For natural water with mixed ions, titanium coated ruthenium, graphite, and titanium coated platinum electrodes can be preferred.

19 What is the concentration polarization phenomenon of Electrodialysis? What are the hazards of concentration polarization?

Answer: When the working current of Electrodialysis exceeds the limit current, Electrolysis of water is generated at the interface between the anion exchange membrane and fresh water, generating H+and OH - ions. Polarization occurs when these ions participate in charge transfer.

In short, the harm of polarization is to consume a kind of electric energy on Electrolysed water unrelated to demineralization, thus causing a waste of electric energy. Moreover, after OH ions enter the concentrated water chamber and CO32- and CaCO3 scale, the performance of membrane and Electrodialysis will decline.

During polarization, the concentration of electrolyte ions on the membrane surface of the desalination chamber is much lower than the concentration of the main solution, causing a high polarization potential. However, the concentration of electrolyte ions on the membrane surface of the concentrated water chamber is much higher than the concentration of the main solution, causing ions that are prone to precipitation in the water to precipitate on the membrane surface. As a result, the apparent resistance of the membrane increases significantly, the current density decreases, and the desalination rate decreases. The current efficiency decreases because a large portion of the current is consumed in the electrolysis of water, generating counter ions consumed by H+and OH - ions to transfer charges. If the negative membrane polarizes first, the H+ions generated by the water dissociation in the desalination chamber enter the concentrated water chamber through the positive membrane, making the membrane surface of the desalination chamber alkaline, easily causing Ca2+, Mg2+ions, and CO32- to form CaCO3 precipitation. If the positive membrane polarizes first, the OH - ions generated by hydrolysis in the desalination chamber enter the concentration chamber through the negative membrane, making the Ca2+and Mg2+ions blocked by the negative membrane easy to form scaling. The precipitation formed on the membrane surface not only results in an increase in membrane resistance, a significant increase in unit water and electricity consumption, and an increase in water flow resistance, but also shortens the service life of the ion exchange membrane due to corrosion caused by changes in the pH value of the solution.

How are 20 fresh water rooms, concentrated water rooms, and extreme water rooms distinguished? Answer: A positive membrane, a partition, and a negative membrane form a membrane pair. The middle of the positive membrane and negative membrane forms a water chamber. Under the action of an electric field, the ions in the water chamber move in a directional direction. When the ions in the water chamber leave the water chamber through traction and selective permeability of the membrane, the water chamber is called a fresh water chamber; On the contrary, when ions enter the water chamber through traction and selective permeability of the membrane, the water chamber is called a concentrated water chamber; The water chamber generated between the positive membrane, negative membrane, or separator and the electrode is called the polar water chamber.

How is the frequent automatic polarity reversal system for concentrated water circulation achieved? What is its significance?

Answer: In the current water treatment industry, the frequent automatic reversal system for concentrated water circulation is controlled by a programmable controller as the core, with the operating time of the system's water production process as the control function. It uses electric or pneumatic through valves and three-way valves to regularly switch the flow direction of concentrated fresh water, so that the fresh water always flows into the production water tank, and the concentrated water is fixedly discharged into the concentrated water circulation tank.

In today's increasingly scarce water resources, the frequent automatic reversal system of concentrated water circulation has profound significance. Firstly, the system has a high water recovery rate of up to 80% (depending on the inlet water quality), and the water-saving effect is very obvious in some large water treatment systems. Secondly, the cost of this system is relatively low, and the requirements for the quality of the system's incoming water are relatively low, making it easy to promote (it is more competitive in water treatment projects of some enterprises or mines that require high recovery rates but cannot invest a lot of funds).

The above is the complete analysis of "Collection Edition! Classic Water Treatment Knowledge Points" brought by Hongjie Water Services to everyone. We hope it can help you!

Shenzhen Hongjie Water Technology Co., Ltd. is an integrated high-tech enterprise specializing in product development, production, sales, engineering design, installation and commissioning, technical consultation, and sales of supporting materials in the field of industrial water treatment and drinking water treatment. Main products: design, manufacturing, installation, commissioning and maintenance of water treatment equipment such as pure water equipment, Ultrapure water equipment, reverse osmosis equipment, GMP purified water equipment, EDI deionized water equipment, domestic sewage equipment, industrial wastewater equipment, softened water equipment and reclaimed water reuse equipment.