1. What pretreatment equipment do you know?

A: pretreatment equipment includes: mechanical filter, high efficiency 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.

2. What do you know about the pre desalination equipment?

Answer: the pre desalting equipment includes electrodialysis device and reverse osmosis device.

3. What deep desalination equipment do you know?

Answer: deep desalination equipment includes anion exchanger, cation exchanger, mixed ion exchanger, distillation unit and EDI unit

4. How is the mechanical filter selected? How does it work?

A: the selection of mechanical filter is based on the total water inflow of the system to select the size and combination mode of the filter (if one mechanical filter is not enough, multiple parallel use and standby quantity can be selected). For example, the total water inflow of the system can be obtained according to the ratio of the water recovery rate of the reverse osmosis system to the water yield of the system.

The filler in the mechanical filter is composed of many refined quartz sands with different particle sizes, which are configured in strict order from large to small, so as to form a good grading of quartz sand. When the filter is just put into use, the filtering effect is often not very good because the filter does not form a "bridge" at the beginning. The so-called "bridge" refers to an interception network composed of suspended solids in the water, which intercepts suspended solids with the same particle size, and then intercepts suspended solids with smaller particle size, forming a reverse particle size filtration process of intercepting large particles first and then small particles.

Once the filter forms a "bridge", the filtering effect is very good. With the extension of the operation time, the filtering accuracy is higher and higher, the interception net is thicker and thicker, and the inlet and outlet pressure difference is larger and larger. When the pressure difference reaches 1kg / cm2, the filter should be backwashed. In the process of backwashing, it is best to equipped with compressed air to scrub the quartz sand. The general engineering experience is that the mechanical filter with diameter less than 2500mm does not need compressed air; The mechanical filter with diameter more than 2500mm must be scrubbed with compressed air to achieve satisfactory cleaning effect; The backwashing flow is generally 3-4 times of the design capacity of the filter.

The old mechanical filters mostly use large pebbles as the foundation cushion, and the bottom is evenly perforated with convex steel plates, so that the water distribution is uneven, which is easy to produce large central filtration rate and small edge filtration rate; When the filter is backwashed, the phenomenon of quartz sand mixed layer will occur, so it is inevitable that the filter material will leak into the lower pipeline and precision filter, which poses a serious threat to the precision filter and reverse osmosis device.

After continuous practice and experiments, many manufacturers have improved the mechanical filter. The water distribution device adopts perforated plate and is equipped with a special form of ABS water cap. This kind of ABS water cap has different functions of two-way output, that is, the output is small during operation, and the backwashing output can be increased several times, so that the water distribution of the filter is more uniform during washing, more thorough during backwashing, and the water quality is greatly improved.

In order to prevent fine sand filter during operation or backwashing, the transmission gap of this kind of ABS water cap is very small, generally about 0.1-0.2mm. It should be noted that during the filling of filter filler, a certain amount of water must be injected into the filter to prevent large quartz sand from breaking the ABS water cap; In the process of installing the water cap, do not wear hard shoes to prevent crushing the ABS water cap.

The mechanical filter is equipped with backwashing water inlet limit butterfly valve to control and adjust the backwashing water flow. The backwashing strength shall expand the filter layer by 15-25%, and the backwashing compressed air strength is generally 10-18l / s.m2. If there is no compressed air, roots blower can be considered.

5. How is the precision filter selected? How many ways can the filter element be used?

Answer: the selection of precision filter is matched with the total water inflow. The diameter of precision filter is selected according to the total water inflow. For the filter element with 40 "5um filtration accuracy, the single water yield is about 2m3 / h. The types of filter elements include polypropylene filter element, honeycomb filter element, spray melting filter element, folding filter element, etc.

6. How to remove iron in 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 natural oxidation; The aerated water passes through the iron and manganese removal filter for iron removal. If most of the iron in the water is trivalent iron, it does not need aeration and directly enters the iron and manganese removal filter for removal.

7. Why do some water types have to add a carbon dioxide remover after passing through the cation exchanger?

Answer: as a result of the exchange between metal ions in water and H + ions on cation resin, H + ions enter the water. Therefore, the outlet water of cation exchanger is acidic, which converts most of HCO3 - in water into H2CO3 and further into CO2 gas. Due to the low solubility of CO2 gas, first, it provides good conditions for degassing; second, if degassing is not carried out, H2CO3 will be exchanged with anion exchange resin, It increases the burden of anion exchanger and shortens the water production cycle of anion exchanger.

Usually, the carbon dioxide remover is placed behind the cation exchanger, in front of the anion exchanger, or before some pre desalination systems such as reverse osmosis. However, in some places, the carbon dioxide remover is not added. All these depend on the water quality and water type of the user.

8. How many anti-corrosion methods are there?

A: the anti-corrosion methods include rubber lining, epoxy, plastic lining, enamel and other anti-corrosion methods.

9. What equipment does the reverse osmosis device mainly consist of?

Answer: the reverse osmosis device is mainly composed of high-pressure pump, high-pressure pump outlet gate valve (manual or electric), high-pressure and low-pressure protection switch, water inlet flowmeter (or not), water production flowmeter, concentrated water flowmeter, water production conductivity meter, membrane module (pressure vessel, reverse osmosis membrane element), concentrated water electric valve, concentrated water stop valve, water inlet pressure gauge, interstage pressure gauge, concentrated water pressure gauge, produced water pressure gauge, reverse osmosis support, reverse osmosis control panel Reverse osmosis sampling plate, bursting disc and corresponding pipes, clamps, elbows, etc.

10. What are the advantages and disadvantages of electrodialysis?

Answer: the advantages of electrodialysis are:

1. Low energy consumption and small floor area.

Low noise, simple operation 2.

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

4. Little environmental pollution.

5. Wide application range: 200-40000 mg / h.

The disadvantages of electrodialysis are:

1. The installation is complicated.

2. The desalination effect is not complete, generally 75%.

3. The water recovery rate is low, generally 50%.

11. What are the brands of Yin Yang heterogeneous ion exchange membrane? What are their characteristics?

Answer: Yin Yang heterogeneous ion exchange membranes mainly include Shanghai chemical plant Shuanghua heterogeneous ion exchange membrane, Lin'an heterogeneous ion exchange membrane, Beijing Shunyi heterogeneous ion exchange membrane, etc; A high-quality heterogeneous ion exchange membrane must have the following characteristics:

1. Strong permeability. Selective permeability is the main index to measure the performance of membrane. It directly affects the current efficiency and desalination effect of electrodialyzer. Its selective permeability is greater than 85%.

2. Low film 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 cation and anion migration, a concentrated ionic solution will be 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. In particular, the polar water participating in the chemical reaction will produce highly oxidizing oxygen and chlorine. Therefore, 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 has high removal effect on strong electrolyte.

12. What material is the electrode of electrodialysis made of? What are the specifications? What are the advantages and disadvantages of each?

A: electrodialysis electrodes are divided into several types: titanium Plated Platinum electrode, titanium coated ruthenium electrode, graphite electrode and stainless steel electrode; The electrode varies according to the size of electrodialysis body. The 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 good corrosion resistance and can be used under very harsh conditions, but the price of platinum is expensive and there are few resources, which limits its promotion in China.

Titanium coated ruthenium electrode: it is a compound coated with ruthenium (RU), iridium (IR) and titanium (TI) on the titanium substrate, and its mixed oxide is formed after high-temperature treatment; Because the ion radii 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 in the CO oxidation of heat treatment, which has superior corrosion resistance and is very suitable for being used as electrode material.

Graphite electrode: graphite electrode is easy to be corroded, 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 polar water has a strong scouring effect on graphite. On the other hand, the gas produced by electrode reaction has an impact on graphite. Combined with electrochemical corrosion, it often causes the peeling of graphite particles, pollutes the water quality and even blocks the polar water channel; With the appearance of titanium coated ruthenium electrode, graphite electrode has been gradually eliminated.

Stainless steel electrode: Generally speaking, stainless steel can only be used as cathode and not as anode. Otherwise, because there are many chloride ions in natural water, the anode of stainless steel will dissolve and form divalent iron, nickel and chromium ions.

The correct selection of electrode materials is of great significance to prolong the service life of the electrode and reduce the system investment and operation cost. Electrodes of different materials can be selected for different water quality:

1 for natural water with chloride as the main component, titanium coated ruthenium electrode can be preferred.

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

3 for natural water with calcium bicarbonate as the main component, stainless steel and titanium coated ruthenium electrode can be preferred.

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

13. How to distinguish fresh water chamber, concentrated water chamber and extreme water chamber?

A: a positive membrane, a diaphragm and a negative membrane form a membrane pair. The water chamber is formed between the positive membrane and the negative membrane. Under the action of 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 fresh water chamber; On the contrary, when ions enter the water chamber through traction and selective permeability of the membrane, the water chamber becomes a concentrated water chamber; The water chamber generated between the positive film, negative film or diaphragm and the electrode becomes an extreme water chamber.

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

A: the electrodialysis device is composed of several parts, including negative film, positive film, diaphragm, electrode, clamping device, leak proof rubber plate, pickling system, flowmeter, pressure gauge, ABS pipe fittings, valves and thyristor rectifier cabinet.

The selective permeability of anion and cation membranes to water ions makes the system divided into concentrated water, fresh water and extreme water, that is, the desalination part of the device.

The main material of the diaphragm is polypropylene, which plays the role of supporting the amniotic membrane and forming a concentrated fresh water chamber with it.

The electrode mainly forms the electric field required by the ion exchange membrane. The electrode is composed of cloth head, perforated plate and PVC frame.

The clamping device is mainly used to fix the cation and anion exchange membrane, electrode, partition plate, etc. to make it a whole.

The leak proof rubber plate is between the electrode and the diaphragm to prevent the system from leaking at the edge of the electrode.

Pickling system is an indispensable part of the whole plant. When the electrodialysis device produces abnormal phenomena such as the decrease of desalination rate, the decrease of water production and the increase of operating pressure, it should be judged what causes the system is composed of, such as scaling, inorganic pollution blocking, organic pollution blocking, etc., and corresponding chemical agents should be used for chemical cleaning.

The thyristor rectifier cabinet is the energy feeding part of the device. It rectifies the power frequency AC into a DC voltage with adjustable voltage through the thyristor rectifier device, which is added to the electrode to form a DC electric field in the membrane stack to pull the cation and anion in the solution to produce directional movement.

The main parameters of silicon controlled rectifier cabinet are: rectifier voltage, working current and rectifier 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.

15. What is the desalination principle of electrodialysis?

Answer: the cation anion exchange membrane in the electrodialysis device has selective permeability. When the ions in the solution move directionally under the action of the electric field, the selective permeability of the cation anion exchange membrane is used to form concentrated water or fresh water in different water chambers through or without the corresponding exchange membrane.

16. What is the distribution proportion of concentrated, light and extreme water in electrodialysis?

Answer: the distribution ratio of concentrated water, fresh water and polar water in electrodialysis device is approximately 4:4:2, so the measures to save polar water in electrodialysis desalination system are very meaningful; Common measures to save extreme water include discharging some concentrated water after being used as extreme water or adopting extreme water circulation; The specific mode of extreme water circulation system is that softened water or demineralized water + NaCl solution acts as extreme water circulation.

17. How to realize the automatic circulation of extremely concentrated water? What is its significance?

A: in the current water treatment industry, the automatic pole reversal system with frequent concentrated water circulation takes the programmable controller as the control core, takes the operation time of the system water production process as the control function, and uses the electric or pneumatic through valve and three-way valve to regularly switch the flow direction of concentrated fresh water, so that the fresh water always flows into the produced water tank, and the concentrated water is fixedly discharged into the concentrated water circulation tank.

In today's increasingly scarce water resources, the automatic pole reversal system with frequent concentrated water circulation is of far-reaching significance. First, the water recovery rate of the system is high, which can reach 80% (depending on the inlet water quality). The effect of water saving is very obvious in some large-scale water treatment systems.

Second, the cost of the system is relatively low, the requirements for the inlet water quality of the system are relatively low, and it is easy to promote (it is more competitive in the water treatment projects of some enterprises or factories and mines that require high recovery rate and can not invest more funds).

18. What kinds of pumps are needed in the water treatment system project? How to select pumps from different manufacturers?

Answer: ordinary pumps, booster pumps and anti-corrosion pumps are generally required in the water treatment system project. Ordinary pumps generally use is cast iron pumps; Stainless steel water pump is generally selected for booster pump, such as the high-pressure pump imported from granff, Denmark (depending on the specific situation); IH chemical pump or engineering plastic pump is generally selected as the anti-corrosion water pump.

The pump models of different manufacturers are different. First, select the flow of the pump according to the process requirements of the system; Secondly, select the head of the water pump according to the process requirements (1kg is about 10m head and 1MPa is about 10kg); Thirdly, select the material of the water pump according to the process requirements (mainly refers to the material of the pump head); Finally, according to the power consumption of various pumps, the pumps that can meet the process requirements and save the energy consumption of the system are selected.

19 several basic concepts in water treatment system: TDS, SDI, LSI, KSP

Answer:

TDS: total dissolved solids (generally similar to mineralization)

SDI: pollution index is an index to measure the pretreatment effect of the system, SDI < 6.7. For deep well water, the requirement of reverse osmosis device for inlet SDI is SDI < 5.

LSI: Langelier saturation index, which measures the scaling tendency of reverse osmosis device. LSI = 0, and the system has no scaling and corrosion tendency; LSI > 0, the system tends to scale; LSI < 0, the system has corrosion tendency. For reverse osmosis system, LSI value shall not be greater than 0. The LSI value of the system can be reduced by adding acid or reducing the water recovery rate of the system.

KSP: solubility equilibrium constant. The reverse osmosis device selectively permeates the solvent and solute in the raw water, resulting in concentration on the concentrated water side due to the reduction of solvent. When the concentration product of dissolved solids on the concentrated water side is greater than the solubility equilibrium constant, it will crystallize and precipitate, which will bring harm to the reverse osmosis device. To increase the solubility equilibrium constant of the system, scale inhibitor can be added, which can increase the solubility of dissolved solids.

20. How can the LSI index be effectively controlled?

A: to effectively control the LSI index of the system, the following aspects can be adopted:

1 the LSI index of the system can be reduced by reducing the water recovery rate of the system.

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

3. The solubility of dissolved salt in the system can be increased by adding corresponding agents, such as trispe1000 scale inhibitor.

4. Ions with easy structure in water can be reduced or pre removed, such as water entering the softening system through the softening column.

21. What kinds of instruments and meters must be used in the reverse osmosis system?

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

1 pollution index instrument: used to measure the SDI index of system pretreatment.

2 concentrated water flowmeter: it is used to measure the flow of concentrated water in the system and determine the recovery rate of the system in combination with the produced water flowmeter.

3 water production flowmeter: used to measure the flow of water production in the system. Produced water conductivity meter: used to measure the quality (conductivity) of produced water in the system

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

5 water inlet flowmeter: used to measure the total water inlet flow of the system.

6 thermometer: used to measure the temperature of system operation.

7 influent pH meter: used to measure the change of influent pH value of the system.

8. Water inlet conductivity meter: it is used to measure the water inlet conductivity of the system and determine the desalination rate of the system in combination with the produced water conductivity.

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

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

A reverse osmosis system is relatively complex, and the instruments used are determined by the process requirements and user investment. Normal reverse osmosis system only needs water production flowmeter, concentrated water flowmeter, water production conductivity meter, pressure gauge and high and low pressure protection.

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

Answer: "water hammer" is because there is air mixed in the pressure vessel. When starting the device, the necessary means are not used to remove the air in the vessel, so that the high-pressure water flow mixed with the air will produce violent vibration when moving into the vessel. In serious cases, it will smash the membrane element and bring unrecoverable losses. "Prevention first, prevention first", how to prevent the phenomenon of "water hammer" is very important. The general measures taken are:

1. The high-pressure pump adopts soft start mode to avoid, such as step-down start, variable frequency speed regulation start and series resistance start with automatic controller.

2 avoid in operation mode, such as closing or turning down the inlet valve during startup, and then slowly open the valve until the system working pressure is reached.

3 use control to prevent avoidance. For example, use PLC to control an electric slow door opening and open the valve within tens of seconds.

4 use the installation process to prevent. For example, a return pipe is set at the concentrated water discharge port, so that the highest point of the pipe exceeds the highest pressure vessel in the reverse osmosis device, so that the pressure vessel will be filled with water when the device stops running. The above points are the measures often used in engineering application, which can be adopted or adopted according to the actual situation. It is worth noting that no matter which project, point 4 is necessary.

23. Why must the reverse osmosis concentrated water discharge pipe be a little higher than the unit?

Answer: the concentrated water discharge valve is always open during reverse osmosis operation. In this way, when the reverse osmosis device stops operation, if the highest point of the discharge pipe is lower than the highest point of the pressure vessel, a "siphon" phenomenon will occur. The water in the pressure vessel will flow out of the reverse osmosis device through the concentrated water discharge pipe due to its own weight, and air is mixed into the pressure vessel. First, it is easy to cause water hammer, Second, during shutdown, the oxygen in the air will more or less oxidize the reverse osmosis membrane elements and affect the service life of the membrane elements.

24. Water inflow index of electrodialysis and reverse osmosis?

Answer: the influent indexes of 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 diaphragm), SDI is about equal to 0

Free chlorine: CL ≤ 0.3mg-0.5mg/l

The influent indexes of reverse osmosis include: iron content: Fe ≤ 1mg / L, free chlorine: CL ≤ 0.1mg

SDI: less than 4, temperature range: 5-45 ℃, turbidity: less than 1ntu

25. Water inlet and outlet indexes of mechanical filter, iron and manganese removal filter and carbon dioxide remover?

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

26. What is the concentration polarization phenomenon of electrodialysis? What are the hazards of concentration polarization?

A: when the working current of electrodialysis exceeds the limit current, water electrolysis is generated at the interface between anion exchange membrane and fresh water to generate H + and oh - ions, which produce polarization when they participate in charge transfer.

In short, the harm of polarization is to consume a kind of electric energy on electrolytic water unrelated to desalination, resulting in a waste of electric energy. Moreover, after oh - ions enter the concentrated water chamber and scale with CO32 - and CaCO3, the performance of membrane and electrodialysis will be reduced.

During polarization, the concentration of electrolyte ions on the membrane surface of the desalination chamber is much lower than that of the main solution, resulting in a high polarization potential, while the concentration of membrane surface of the concentrated water chamber is much higher than that of the main solution, which makes the ions easy to form precipitation in the water precipitate on the membrane surface. As a result, the apparent resistance of the membrane to 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 generate H + and oh - ions instead of the consumed counter ions to transfer charges. If the negative membrane is polarized first, the H + ions produced by water dissociation in the desalination chamber enter the concentrated water chamber through the positive membrane, making the membrane surface of the desalination chamber alkaline, which is easy to form CaCO3 precipitation from Ca2 +, Mg2 + ions and CO32 -.

If the positive membrane is polarized first, the OH - ions produced by hydrolysis in the desalination chamber enter the concentration chamber through the negative membrane, so that Ca2 + and Mg2 + ions blocked by the negative membrane are easy to form scaling. In addition to the increase of membrane resistance, the obvious increase of water and electricity consumption per unit production and the increase of water flow resistance, the precipitation formed on the membrane surface also shortens the service life of the ion exchange membrane due to the corrosion caused by the change of solution pH value.

27. How to control concentration polarization?

Answer:

1 strictly control the operating current, which means that electrodialysis operates under the condition of lower than the limit current density.

2. Strengthen the transmission process in the electrodialysis compartment, such as high-temperature electrodialysis with good turbulence effect.

3. Take measures such as regular pickling, adding scale inhibitor and changing electrodes to eliminate the precipitation caused by concentration polarization.

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

28. What are the characteristics of UV sterilizer?

Answer: the characteristics of ultraviolet sterilizer are as follows:

1. Ultraviolet sterilization has the advantages of fast speed, high efficiency and good effect.

2 ultraviolet radiation will not change the physical and chemical properties of water, and will not bring pollution such as additives to pure water.

3. It can be used under various water flows. It has the advantages of simple operation and convenient use. It only needs to clean the quartz glass tube sleeve regularly.

4 small size, light weight, low power consumption and long service life.

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

A: the factors affecting the germicidal efficacy of UV are the intensity of UV, the wavelength of UV spectrum and irradiation time. Precautions when using ultraviolet sterilizer are:

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

Flow: in the same sterilizer, when the ultraviolet radiation energy is constant and the bacterial content in the water changes little, the water flow through the sterilizer has a significant impact on the sterilization effect.

Physical and chemical properties of water: the chromaticity, turbidity and total iron content of water absorb ultraviolet rays in varying degrees, which reduces the effect of sterilization.

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

Medium temperature around the lamp tube: the radiation spectral energy of ultraviolet lamp tube is related to the temperature of lamp tube wall.

Quartz tube sleeve: the quality and wall thickness of the tube sleeve are related to the ultraviolet transmittance. The quartz tube sleeve has high purity and good efficiency.

Thickness of water layer: the thickness of water layer has a great relationship with the sterilization effect.

30. What are the characteristics of ozone sterilizer?

A: ozone is one of the most effective fungicides in water treatment. Only free chlorine can be compared with ozone. The advantage of ozone disinfection is its high sterilization efficiency. It is the most effective disinfectant so far, even for highly resistant microorganisms such as viruses and cysts.

It can reduce the smell, taste and chroma of water supply, and the only remaining material during decomposition is dissolved oxygen. In addition, the bactericidal ability of ozone is not affected by the change of pH value and ammonia. Ozone disinfection also has its disadvantages, because electricity must be used to produce ozone and cannot be stored. In case of changes in water quality and quantity, it is difficult to adjust the demand for ozone in time.

Experience has proved that ozone is most suitable for water plants with low water consumption and stable water consumption; In addition, although ozone is a strong oxidant, its oxidation ability is selective and does not generally produce oxidation. Substances that are easy to be oxidized, such as ethanol, are not easy to interact with ozone.

31. What problems should be paid attention to in water sample collection in water quality analysis?

Answer: in water quality analysis, the following problems should be paid attention to in water sample collection:

The sampling shall be representative, that is, the water sample taken can represent the water quality of the whole water body.

The water quality of water samples should be stable or have no obvious change between adoption and analysis. The sampling amount shall be 4-5 times of the sample amount required for the test items to ensure the amount of water samples for repeated analysis and re inspection. The minimum sampling amount shall be subject to the requirements to ensure the accuracy and accuracy of the analysis.

The contact time between the water sample and the sampling equipment shall be shortened as far as possible. The water sample shall flow through the pipeline at a high linear flow rate. If it is necessary to connect the intermediate flow path such as pipeline and valve, special attention shall be paid to the pollution of this intermediate link, and its material and cleaning requirements shall be consistent with those of the container.

For the items tested on site, such as pH value, dissolved oxygen, alkalinity, CO2, ferrous, ammonia nitrogen, residual chlorine, etc., the time interval from sampling to analysis shall be shortened as far as possible, and online analysis and detection shall be adopted as far as possible.

Use records shall be kept and labels shall be pasted on the sampling container, indicating the name, time, place, temperature, sampling volume, container and sampler, etc.