Summary of 31 pure water process problems

1. What pretreatment equipment do you know?

Answer: Pretreatment equipment includes: mechanical filter, high-efficiency fiber filter, activated carbon filter, precision filter, ultrafiltration, microfiltration, sodium ion softener, iron and manganese removal filter, chemical dosing device, raw water tank, aeration tank.

2. What desalination pretreatment equipment do you know?

Answer: Desalination pretreatment equipment includes electrodialysis and reverse osmosis devices.

3. What deep desalination equipment do you know?

Answer: Deep desalination equipment includes anion exchangers, cation exchangers, mixed ion exchangers, distillation units, and EDI units.

4. How is a mechanical filter selected? What is its working principle?

Answer: The selection of a mechanical filter is based on the total system inflow to select the size and combination of filters (if one mechanical filter is not enough, multiple filters can be used in parallel and the number of backups can be selected), such as determining the total system inflow based on the water recovery rate and the ratio of system water production.

The filler inside the mechanical filter is composed of many refined quartz sands of different particle sizes, strictly arranged in order from large to small, thus forming a good quartz sand gradation. When the filter is first put into use, the filtration effect is often not very good, because at the beginning, the filter has not formed a "bridge." The so-called "bridge" refers to an interception network formed by suspended substances in the water. This interception network intercepts suspended substances of similar particle size, and then intercepts smaller suspended substances, forming an inverse particle size filtration process that first intercepts large particles and then intercepts small particles.

Once the filter forms a "bridge," the filtration effect is very good. As the operation time increases, the filtration accuracy becomes higher and higher, the interception network becomes thicker and thicker, and the inlet and outlet pressure difference becomes larger and larger. When the pressure difference reaches 1 kg/cm2, the filter should be backwashed. During the backwashing process, it is best to use compressed air to scrub the quartz sand. General engineering experience is that mechanical filters with a diameter less than 2500 mm do not need compressed air; while mechanical filters with a diameter greater than 2500 mm must be scrubbed with compressed air to achieve satisfactory cleaning results; the backwashing flow rate is generally 3-4 times the design capacity of the filter.

Old mechanical filters mostly use large cobblestones as the base layer, and the bottom uses convex steel plates with evenly punched water-permeable holes, resulting in uneven water distribution, easily causing the central filtration rate to be large and the edge filtration rate to be small; when the filter is backwashed, sand mixing will occur, which inevitably leads to filter material leakage into downstream pipelines and precision filters, posing a serious threat to precision filters and reverse osmosis devices.

Through continuous practice and experiments, many manufacturers have improved mechanical filters. The water distribution device uses a perforated plate with a special ABS water cap. This ABS water cap has the function of different output in two directions, that is, the output is smaller during operation, and the backwashing output can be increased several times, making the water distribution more uniform during normal washing and more thorough during backwashing, greatly improving the water quality.

To prevent fine sand from penetrating the filter during operation or backwashing, the gap of this ABS water cap is very small, generally around 0.1-0.2 mm. It is worth noting that during the filling of the filter filler, a certain amount of water must be injected into the filter to prevent large quartz sand from crushing the ABS water cap; during the installation of the water cap, hard shoes cannot be worn to prevent crushing the ABS water cap.

The mechanical filter has a backwash water inlet limit butterfly valve to control and adjust the backwash water flow rate. The backwash intensity should make the filter layer expand by 15-25%, and the backwash compressed air intensity is generally 10-18 L/S.m2. If there is no compressed air, a Roots blower can be considered.

5. How is a precision filter selected? What are the types of filter elements?

Answer: The selection of a precision filter is matched with the total inflow, and the diameter of the precision filter is selected according to the total inflow. For a 40" 5um filter element, the single water production is approximately 2 m3/h. The types of filter elements are mainly polypropylene filter elements, honeycomb filter elements, melt-blown filter elements, and pleated filter elements.

6. How to remove iron in water?

Answer: The iron in groundwater is generally ferrous iron, so ferrous iron must be oxidized to ferric iron. The oxidation process is completed through aeration. The aeration device allows the water to fully contact with oxygen to produce natural oxidation; the aerated water is then passed through an iron and manganese removal filter for iron removal. If most of the iron in the water is ferric iron, aeration is not necessary, and it can be directly entered into the iron and manganese removal filter for removal.

7. Why is a carbon dioxide remover necessary after a cation exchanger for some water types?

Answer: The exchange of metal ions in water with H+ ions on the cation resin results in H+ ions entering the water, so the effluent from the cation exchanger is acidic, causing most of the HCO3- in the water to be converted to H2CO3 and further converted to CO2 gas. Due to the low solubility of CO2 gas, it provides good conditions for degassing. Secondly, if degassing is not performed, H2CO3 will exchange with the anion exchange resin, increasing the burden on the anion exchange resin and shortening the water production cycle of the anion exchange resin.

Usually, the carbon dioxide remover is placed after the cation exchanger and before the anion exchanger. It can also be placed before reverse osmosis and other desalination pretreatment systems. However, some places do not need to add a carbon dioxide remover. All of these depend on the water quality and type of the user.

8. What are the types of corrosion protection?

Answer: Corrosion protection methods include rubber lining, epoxy lining, plastic lining, enamel, and other methods.

9. What equipment mainly constitutes a reverse osmosis device?

Answer: A reverse osmosis device mainly consists of a high-pressure pump, a high-pressure pump outlet gate valve (manual or electric), high and low-pressure protection switches, an inlet flow meter (can also be omitted), a product water flow meter, a concentrate flow meter, a product water conductivity meter, a membrane assembly (pressure vessel, reverse osmosis membrane element), a concentrate electric valve, a concentrate shut-off valve, an inlet pressure gauge, interstage pressure gauges, a concentrate pressure gauge, a product water pressure gauge, a reverse osmosis support, a reverse osmosis control panel, a reverse osmosis sampling panel, a burst membrane, and corresponding pipes, clamps, elbows, etc.

What are the advantages and disadvantages of electrodialysis?

Answer: The advantages of electrodialysis are:

1. Low energy consumption and small footprint.

2. Simple operation and low noise.

3. Stable effluent water quality, no phase change during desalination.

4. Low environmental pollution.

5. Wide range of applications: 200-40000mg/h.

The disadvantages of electrodialysis are:

1. Relatively complex installation.

2. Desalination effect is not thorough, generally 75%.

3. Low water recovery rate, generally 50%.

What brands of heterogeneous ion exchange membranes are there? What are their characteristics?

Answer: The main brands of heterogeneous ion exchange membranes include Shuang Hua brand heterogeneous ion exchange membranes from Shanghai Chemical Factory, Lin'an heterogeneous ion exchange membranes, and Beijing Shunyi heterogeneous ion exchange membranes, etc.; High-quality heterogeneous ion exchange membranes must have the following characteristics:

1. Strong selective permeability. Selective permeability is the main indicator to measure membrane performance, which directly affects the current efficiency and desalination effect of the electrodialyzer, and its selective permeability is greater than 85%.

2. Small membrane resistance. The electrodialyzer is composed of hundreds of pairs of ion exchange membranes, so the membrane resistance accounts for a large proportion in the total resistance. If the resistance is small, the operating voltage is low and the current efficiency is high.

3. Strong chemical stability. In the process of anion and cation migration, a high-concentration ion solution will be formed in the concentrate chamber; when polarization occurs, the pH value of the stagnant layer on both sides of the membrane will also change, especially the participation of the electrode water in the chemical reaction will produce highly oxidizing oxygen and chlorine, so the membrane must have strong chemical stability to prolong the service life of the electrodialyzer.

4. Strong mechanical strength and dimensional stability.

5. Low diffusion performance.

6. High removal effect on strong electrolytes.

What materials are the electrodes of electrodialysis made of? What are the specifications? What are the advantages and disadvantages of each?

Answer: Electrodialysis electrodes are of several types: titanium-plated platinum electrodes, titanium-coated ruthenium electrodes, graphite electrodes, and stainless steel electrodes; The electrode size varies depending on the size of the electrodialysis unit. Common engineering electrode specifications include: 800×1600mm, 400×1600mm, 400×800mm, 340×640mm, etc.

Different electrode materials have different characteristics:

Titanium-plated platinum electrodes: They have excellent corrosion resistance and can be used under very harsh conditions, but the price of platinum is expensive and resources are scarce, limiting its promotion in China.

Titanium-coated ruthenium electrodes: Ruthenium (Ru), iridium (Ir), and titanium (Ti) compounds are coated on the titanium substrate, and after high-temperature treatment, their mixed oxides are formed; Because the ionic radii of ruthenium (Ru), iridium (Ir), and titanium (Ti) are very close, and the lattice structure and space group belong to the same type, a solid solution of RuO2-IrO2-TiO2 can be formed in the co-oxidation of heat treatment, which has excellent corrosion resistance and is very suitable as electrode material.

Graphite electrodes: Graphite electrodes are easily corroded, mainly due to chemical corrosion and mechanical wear; When graphite is used as the anode, due to anodic oxidation, graphite is oxidized to CO2 or CO, destroying its crystal structure and causing damage; In electrodialysis devices, graphite electrode loss is mainly caused by mechanical action. The high-velocity electrode water has a strong scouring effect on graphite. On the other hand, the gas generated by the electrode reaction has an impact on graphite. Coupled with electrochemical corrosion, graphite particles often fall off, polluting the water quality or even blocking the electrode water channel; With the advent of titanium-coated ruthenium electrodes, graphite electrodes have gradually been eliminated.

Stainless steel electrodes: Generally speaking, stainless steel can only be used as the cathode and not as the anode, otherwise, because natural water contains many chloride ions, it will lead to the anodic dissolution of stainless steel to generate divalent iron, nickel and chromium ions.

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

1. For natural water with chlorides as the main component, titanium-coated ruthenium electrodes are preferred.

2. For natural water with sulfates as the main component, lead plates, stainless steel, and titanium-coated ruthenium electrodes are preferred.

3. For natural water with calcium bicarbonate as the main component, stainless steel and titanium-coated ruthenium electrodes are preferred.

4. For natural water with mixed ions, titanium-coated ruthenium, graphite, and titanium-plated platinum electrodes are preferred.

How are the dilute water chamber, concentrate water chamber, and electrode water chamber distinguished?

Answer: One cation exchange membrane, one diaphragm, and one anion exchange membrane constitute a membrane pair. The water chamber between the cation exchange membrane and the anion exchange membrane is formed. Under the action of the electric field, the ions in the water chamber move directionally. When the ions in the water chamber leave the water chamber due to the traction and selective permeability of the membrane, the water chamber is called the dilute water chamber; Conversely, when ions enter the water chamber due to the traction and selective permeability of the membrane, the water chamber becomes the concentrate water chamber; The water chamber formed between the cation exchange membrane, anion exchange membrane or diaphragm and the electrode is called the electrode water chamber.

What parts does an electrodialysis device consist of? What are the characteristics and functions of each part?

Answer: The electrodialysis device consists of several parts: anion exchange membrane, cation exchange membrane, diaphragm, electrode, clamping device, anti-leakage rubber plate, acid washing system, flow meter, pressure gauge, ABS pipe and fittings, valve, thyristor rectifier cabinet.

The anion exchange membrane and cation exchange membrane have selective permeability to ions in the water, resulting in the separation of concentrate water, dilute water, and electrode water, which is the desalination part of the device.

The main material of the baffle is polypropylene, which supports the anion exchange membrane and forms a concentrated and dilute water chamber with it.

The electrodes mainly form the electric field required for the ion exchange membrane. The electrodes consist of a water distribution head, a porous plate, and a PVC frame.

The clamping device mainly fixes the anion and cation exchange membranes, electrodes, and baffles to form an integral whole.

The leak-proof rubber plate is located between the electrode and the baffle, preventing water leakage from the system at the electrode edges.

The acid washing system is an indispensable part of the entire device. When the electrodialysis device exhibits abnormal phenomena such as decreased desalination rate, decreased water production, and increased operating pressure, the cause of the problem (e.g., scaling, inorganic fouling, organic fouling) should be determined, and appropriate chemical cleaning agents should be used.

The thyristor rectifier cabinet is the energy input part of the device. It rectifies the industrial frequency AC power into a DC voltage that can be adjusted via thyristor rectifier components. This voltage is applied to the electrodes to form a DC electric field within the membrane stack, driving the anions and cations in the solution to move directionally.

The main parameters of the thyristor rectifier cabinet are: rectification voltage, operating current, and rectification power. Flow meters, pressure gauges, ABS pipes and fittings, and valves are auxiliary accessories of electrodialysis, displaying various operating parameters of the electrodialysis device, connecting water chambers, and switching the water flow direction.

15 What is the desalination principle of electrodialysis?

Answer: The anion and cation exchange membranes in the electrodialysis device have selective permeability. When ions in the solution move directionally under the action of an electric field, the selective permeability of the anion and cation exchange membranes allows certain ions to pass through while others do not, forming concentrated water or dilute water in different water chambers.

16 What is the approximate distribution ratio of concentrated water, dilute water, and polar water in electrodialysis?

Answer: The approximate distribution ratio of concentrated water, dilute water, and polar water in the electrodialysis device is 4:4:2. Therefore, saving polar water in the electrodialysis desalination system is very meaningful. Common measures to save polar water include using part of the concentrated water as polar water before discharge or using polar water circulation. The specific method for the polar water circulation system is to use softened water or desalted water + NaCl solution as the polar water circulation.

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

Answer: In the current water treatment industry, the frequent automatic polarity reversal system for concentrated water circulation uses a programmable logic controller (PLC) as the control core and the system's water production process operation time as the control function. It uses electric or pneumatic direct-through valves and three-way valves to periodically switch the flow direction of concentrated and dilute water, ensuring that dilute water always flows into the water production tank, while concentrated water is fixedly discharged into the concentrated water circulation tank.

In today's world of increasingly scarce water resources, the frequent automatic polarity reversal system for concentrated water circulation has far-reaching significance. Firstly, this system has a high water recovery rate, which can reach 80% (depending on the influent water quality), and the water-saving effect is very significant in some large-scale water treatment systems.

Secondly, the system has a relatively low cost, relatively low requirements for the influent water quality, and is easy to promote (it is more competitive in water treatment projects for enterprises or factories with high recovery rate requirements but limited investment funds).

18 What types of pumps are needed in water treatment system engineering? How should pumps from different manufacturers be selected?

Answer: Water treatment system engineering generally requires ordinary pumps, booster pumps, and corrosion-resistant pumps. Ordinary pumps generally use IS-type cast iron pumps; booster pumps generally use stainless steel pumps such as high-pressure pumps imported from Grundfos, Denmark (depending on the specific situation); corrosion-resistant pumps generally use IH-type chemical pumps or engineering plastic pumps.

The pump models of different manufacturers vary. First, select the pump flow rate according to the system's process requirements; second, select the pump head according to the process requirements (1 kg is approximately equal to 10 meters of head, 1 MPa is approximately equal to 10 kg); third, select the pump material according to the process requirements (mainly referring to the material of the pump head); finally, select the pump based on the power consumption of various pumps, ensuring that it meets the process requirements while saving system energy consumption.

19 Several basic concepts in water treatment systems: TDS, SDI, LSI, Ksp

Answer:

TDS: Total Dissolved Solids (generally similar to mineralization)

SDI: Silt Density Index, an indicator for measuring the pretreatment effect of the system. For deep well water, SDI < 6.7, and the reverse osmosis device requires SDI < 5 for influent water.

LSI: Langelier Saturation Index, an index for measuring the scaling tendency of the reverse osmosis device. LSI = 0 indicates no scaling or corrosion tendency; LSI > 0 indicates a scaling tendency; LSI < 0 indicates a corrosion tendency. For reverse osmosis systems, the LSI value should not exceed 0. The LSI value of the system can be reduced by adding acid or reducing the water recovery rate.

Ksp: Solubility product constant. The reverse osmosis device selectively permeates the solvent and solute in the raw water. Due to the reduction of the solvent on the concentrated water side, concentration occurs. When the concentration product of dissolved solids on the concentrated water side exceeds the solubility product constant, crystallization will occur, which will harm the reverse osmosis device. The solubility product constant of the system can be increased by adding scale inhibitors, which can increase the solubility of dissolved solids.

20 How can the LSI index be effectively controlled?

Answer: The LSI index of the system can be effectively controlled through the following aspects:

1 Reduce the system's water recovery rate to lower the LSI index.

2 Add acid to lower the LSI index.

3 Add appropriate chemicals to increase the solubility of dissolved salts in the system, such as adding TRISPE1000 scale inhibitor.

4 Reduce or pre-remove easily structured ions in the water, such as softening the system's influent water through a softener.

21 What instruments and meters are required in a reverse osmosis system?

A: Several instruments and meters are essential in a reverse osmosis system:

1. Pollution Index Meter: Used to measure the SDI index of the system's pretreatment.

2. Concentrate Flow Meter: Used to measure the flow rate of the concentrate water in the system, and used in conjunction with the permeate flow meter to determine the system recovery rate.

3. Permeate Flow Meter: Used to measure the flow rate of the permeate water in the system. Permeate Conductivity Meter: Used to measure the water quality (conductivity) of the system's permeate water.

4. Pressure Gauge: Measures the system's feed water pressure, inter-stage pressure, concentrate pressure, and permeate pressure.

5. Feed Water Flow Meter: Used to measure the total feed water flow rate of the system.

6. Thermometer: Used to measure the operating temperature of the system.

7. Feed Water PH Meter: Used to measure changes in the PH value of the system's feed water.

8. Feed Water Conductivity Meter: Used to measure the conductivity of the system's feed water, and used in conjunction with the permeate conductivity meter to determine the system's desalination rate.

9. Oxidation-Reduction Meter: Used to measure the amount of oxidizing substances in the system's feed water to determine the threat level to system safety.

10. High and Low Pressure 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 the process requirements and user investment. A normal reverse osmosis system only needs a permeate flow meter, concentrate flow meter, permeate conductivity meter, pressure gauge, and high and low pressure protection to suffice.

22. What is water hammer? How to solve this problem?

A: "Water hammer" is caused by air mixed in the pressure vessel. When the device is started, the necessary measures to remove the air from the vessel are not adopted, so that when the high-pressure water flow mixed with air moves into the vessel, violent vibrations are produced. In severe cases, the membrane elements can be shattered, resulting in irreparable losses. "Prevention first, prevention is the key". How to prevent the occurrence of "water hammer" is very important. Generally adopted measures include:

1. The high-pressure pump adopts a soft start method to avoid water hammer, such as reduced pressure start, variable frequency speed regulation start, and series resistance start with an automatic controller.

2. Avoid water hammer in the operation method, such as closing or partially closing the inlet valve during startup, and then slowly opening the valve until the system reaches the operating pressure.

3. Use control to prevent water hammer, such as using a PLC to control an electric slow-opening door to open the valve within tens of seconds.

4. Use installation technology to prevent water hammer, such as setting a return pipe at the concentrate discharge port, so that the highest point of the pipe exceeds the highest pressure vessel in the reverse osmosis device. In this way, when the device stops running, the pressure vessel will be filled with water. The above points are commonly used measures in engineering applications. They can all be adopted or several points can be adopted according to the actual situation. It is worth noting that point 4 is necessary for any project.

23. Why must the reverse osmosis concentrate discharge pipe be slightly higher than the device?

A: The concentrate discharge valve is always open during the operation of the reverse osmosis device. Therefore, when the reverse osmosis device stops running, if the highest point of the discharge pipe is lower than the highest point of the pressure vessel, a "siphon" phenomenon will occur, and the water in the pressure vessel will flow out of the reverse osmosis device through the concentrate discharge pipe due to its own weight. Air will be mixed into the pressure vessel, which will easily cause water hammer and the oxygen in the air will have more or less oxidation effect on the reverse osmosis membrane elements, affecting the service life of the membrane elements.

24. Feed water indicators for electrodialysis and reverse osmosis?

A: The feed water indicators for electrodialysis are:

Temperature range: 4-40℃ Iron and manganese content: Fe≤0.3mg/l, Mn≤0.1mg/l

Turbidity: Less than 0.3mg/l (for 0.9mm thick partition) SDI approximately equals 0

Free chlorine: CL≤0.3mg-0.5mg/l

The feed water indicators for reverse osmosis are: Iron content: Fe≤1mg/l Free chlorine: CL≤0.1mg

SDI: Less than 4 Temperature range: 5-45℃ Turbidity: Less than 1NTU

25. Inlet and outlet indicators for mechanical filter, iron and manganese removal filter, and carbon dioxide remover?

A: The inlet suspended solids of the mechanical filter ≤20mg/l, and the outlet suspended solids ≤5mg/l. The inlet iron content of the iron and manganese removal filter ≤30mg/l, and the outlet iron content ≤0.3mg/l. The inlet carbon dioxide content of the carbon dioxide remover ≤330mg/l, and the outlet carbon dioxide content ≤5mg/l.

26. What is concentration polarization in electrodialysis? What are the harms of concentration polarization?

A: When the working current of electrodialysis exceeds the limiting current, water electrolysis occurs at the interface between the anion exchange membrane and the fresh water, generating H+ and OH- ions. When these ions participate in charge transfer, polarization occurs.

In short, the harm of polarization is that a certain amount of electrical energy is consumed on water electrolysis unrelated to desalination, resulting in waste of electrical energy. Moreover, after OH- ions enter the concentrate chamber, they react with CO32- and CaCO3 to form scale, reducing the performance of the membrane and electrodialysis.

During polarization, the concentration of electrolyte ions on the membrane surface of the desalination chamber is much lower than that of the main solution, causing a high polarization potential, while the concentration on the membrane surface of the concentrate chamber is much higher than that of the main solution, causing ions that are easy to precipitate 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 part of the current is consumed in the electrolysis of water to produce H+ and OH- ions to transfer charges instead of counterions. If the anion membrane is polarized first, the H+ ions produced by water dissociation in the desalination chamber pass through the cation membrane into the concentrate chamber, making the membrane surface of the desalination chamber alkaline, which easily causes Ca2+, Mg2+ ions and CO32- to form CaCO3 precipitation.

If the anion exchange membrane is polarized first, the OH- ions produced by hydrolysis in the desalination chamber pass through the anion exchange membrane into the concentration chamber, making it easier for the Ca2+ and Mg2+ ions blocked by the anion exchange membrane to form scale. The precipitation formed on the membrane surface not only increases the membrane resistance and the unit water production power consumption, but also increases the water flow resistance. In addition, the change in the solution pH value corrodes the ion exchange membrane, shortening its service life.

27 How to control concentration polarization?

Answer:

1. Strictly control the operating current, and the electrodialysis operates under the condition of less than the limiting current density.

2. Strengthen the transfer process in the electrodialysis compartment, such as using a screen with good turbulent effect and high-temperature electrodialysis.

3. Adopt measures such as regular acid washing, adding scale inhibitors, and reversing electrodes to eliminate the precipitation caused by concentration polarization.

4. Appropriate pretreatment can be used to improve the water quality of the system.

28 What are the characteristics of ultraviolet sterilizers?

Answer: The characteristics of ultraviolet sterilizers are as follows:

1. Ultraviolet sterilization is fast, efficient, and effective.

2. Ultraviolet irradiation does not change the physical and chemical properties of water, and will not introduce pollution from additional substances into pure water.

3. It can be used under various water flow rates, is simple to operate, and is easy to use. Only the quartz glass tube sleeve needs to be cleaned regularly.

4. Small size, lightweight, low power consumption, and long life.

29 What are the factors affecting the effect of ultraviolet sterilizers and matters needing attention?

Answer: The factors affecting the sterilization effect of ultraviolet rays are the intensity of ultraviolet rays, the wavelength of the ultraviolet spectrum, and the irradiation time. Matters needing attention when using ultraviolet sterilizers are:

Installation location: The closer the installation location of the ultraviolet lamp is to the point of use, the better, but there should also be space for installing or removing the quartz tube sleeve and replacing the lamp tube from one end.

Flow rate: In the same sterilizer, when the radiation energy of ultraviolet rays is constant and the bacterial content in the water does not change significantly, the size of the water flow rate passing through the sterilizer has a significant impact on the sterilization effect.

Physicochemical properties of water: The chromaticity, turbidity, and total iron content of water all absorb ultraviolet rays to varying degrees, resulting in a reduction in the sterilization effect.

Lamp power: The ignition power of the lamp has a great impact on the sterilization efficiency.

Ambient temperature of the lamp tube: The ultraviolet lamp tube radiation spectrum energy is related to the temperature of the lamp tube wall.

Quartz tube sleeve: The quality and thickness of the quartz tube sleeve are related to the transmittance of ultraviolet rays. The higher the purity of the quartz tube sleeve, the better the efficiency.

Water layer thickness: The thickness of the water layer is closely related to the sterilization effect.

30 What are the characteristics of ozone sterilizers?

Answer: Ozone is one of the most effective bactericides in water treatment, and only free chlorine can compare with the bactericidal ability of ozone. The advantages of ozone disinfection are its high bactericidal efficiency. Even for highly resistant microorganisms such as viruses and spores, it is the most effective disinfectant to date.

It can reduce the smell, taste, and chromaticity of water, and the only remaining substance when it decomposes is dissolved oxygen. In addition, the bactericidal ability of ozone is not affected by changes in pH value and ammonia. Ozone disinfection also has disadvantages, because ozone must be generated by electricity and cannot be stored. When encountering changes in water quality and water volume, it is difficult to adjust the ozone demand in time.

It has been verified that ozone is most suitable for water plants with low and stable water consumption; in addition, although ozone is a strong oxidizing agent, its oxidizing ability is selective and does not universally produce oxidation. Substances such as ethanol that are easily oxidized are not easily reacted with ozone.

31 What should be paid attention to when collecting water samples in water quality analysis?

Answer: The following points should be noted when collecting water samples in water quality analysis:

Sampling should be representative, that is, the collected water sample should represent the water quality of the entire water body.

The water quality of the water sample should remain stable or unchanged between sampling and analysis, or there should be no significant changes. The sampling volume should be 4-5 times the required sample volume for the test items to ensure the sample volume for repeated analysis and re-examination. The minimum sampling volume should be determined according to the accuracy and precision requirements of the analysis.

Minimize the contact time between the water sample and the sampling equipment. The water sample flowing through the pipeline should adopt a high linear flow rate. If pipelines and valves are needed during sampling, special attention should be paid to the pollution problem of this intermediate link. The material and cleaning requirements should be consistent with the sampling container.

For on-site test items such as pH, dissolved oxygen, alkalinity, CO2, ferrous iron, ammonia nitrogen, and residual chlorine, the time interval from sampling to analysis should be minimized, and online analysis and detection should be used as much as possible.

Sampling records should be kept, and labels should be affixed to the sampling containers, indicating the sampling name, time, location, temperature, sampling volume, sampling container, and sampler.