1.What pretreatment equipment do you know?

Answer:The pretreatment equipment includes:mechanical filters,high-efficiency fiber filters,activated carbon filters,precision filters,ultrafiltration,microfiltration,sodium ion softeners,iron and manganese removal filters,dosing devices,raw water tanks,and aeration tanks.

2.What are the pre-desalination equipment you know?

Answer:The pre-desalination equipment has an electrodialysis device and a reverse osmosis device.

3.What deep desalination equipment do you know?

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

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

Answer:The selection of mechanical filters is based on the total water intake of the system to select the size of the filter and the combination method(one mechanical filter is not enough,you can choose multiple parallel use and the number of spare parts),for example,the total water intake of the system is obtained based on the ratio of the water recovery rate of the reverse osmosis system to the water produced by the system.The filler in the mechanical filter is made of many refined quartz sand of different particle sizes strictly arranged in the order from large to small,thus forming a good quartz sand grading.

When the filter is first put into use,the filtration effect is often not very good,because the filter did not form a“bridge”at the beginning.The so-called“bridge”refers to an interception net composed of suspended solids in the water.The interception net intercepts suspended solids of the same particle size,and then intercepts suspended solids with smaller particle sizes,forming an anti-particle size filtration process that first intercepts large particulate matter and then small particulate matter.

Once the filter forms a“bridge”,the filtration effect is very good.As the time is put into operation,the filtration accuracy is getting higher and higher,the interception net is getting thicker and thicker,and the pressure difference between the import and export is getting bigger and bigger.When the pressure difference reaches 1kg/cm2,the filter should be backwashed.In the process of backwashing,it is best to be equipped with compressed air to scrub quartz sand.The general engineering experience is that mechanical filters with a diameter of less than 2500mm do not require compressed air;mechanical filters with a diameter greater than 2500mm must be scrubbed with compressed air to achieve a satisfactory cleaning effect;the backwash flow rate is generally the filter's 3-4 times the design capacity.

Most old-fashioned mechanical filters use large pebbles as the basic cushion,and convex steel plates are used at the bottom to evenly mark the permeable holes,so that the water distribution is uneven,which is prone to large central filtration rates and small edge filtration rates;Quartz sand mixing will occur when the filter is backwashed,so it is inevitable that the filter material will leak into the lower pipes and precision filters,which poses a serious threat to precision filters and reverse osmosis devices.

After continuous practice and experiments,many manufacturers have improved the mechanical filter.The water distribution device adopts a porous plate and a special form of ABS water cap.This kind of ABS water cap has the function of different two-way output,that is,the output during operation is small,and the backwash output can be increased several times,so that the filter is more evenly distributed during the washing,and the water is more thoroughly during the backwash,and the quality of the water is greatly improved.In order to prevent fine sand from passing through the filter during operation or backwashing,the passage gap of this kind of ABS water cap is very small,generally about 0.1-0.2mm.It is worth noting that in the process of filling 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;in the process of installing the water cap,you cannot wear hard shoes to prevent the ABS water cap from being crushed.

The mechanical filter is equipped with a backwash water inlet limit butterfly valve to control and adjust the backwash water flow.The backwash strength should expand the filter layer by 15-25%,and the backwash compressed air strength is generally 10-18L/S.m2.If there is no compressed air,consider using Roots fans.

5.How is the precision filter selected?How many ways are there to filter the filter element?

Answer:The selection of precision filters is matched with the total water inlet volume,and the diameter of the precision filter is selected according to the total water inlet volume.For a filter element with a 40"5um filtration accuracy,the water output of a single filter element is approximately 2m3/h.The types of filter elements are roughly polypropylene filter elements,hive filter elements,melt-in-melt filter elements,folding filter elements,etc.

6.How to remove iron from water?

Answer:The iron in groundwater is generally divalent ferrous iron,so the divalent ferrous iron must be oxidized to trivalent iron.The oxidation process is completed by aeration.The aeration device fully contacts the water with oxygen to produce natural oxidation;the water after aeration is removed through the iron and manganese removal filter for the iron removal process.If most of the iron in the water is trivalent iron,it does not need to be aeration and directly enters the iron and manganese removal filter for removal.

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

Answer:The result of the exchange of metal ions in the water with H+ions on the positive resin causes H+ions to enter the water.Therefore,the effluent of the cation exchanger is acidic,so that most of the HCO3-in the water is converted into H2CO3 and further converted into CO2 gas.Due to the low solubility of CO2 gas,one is to provide good conditions for degassing,and the other is that if degassing is not carried out,H2CO3 will be exchanged with the anion exchange resin,which increases the burden on the anion exchanger and shortens the water production cycle of the anion exchanger.Usually the carbon dioxide remover is placed behind the cation exchanger,in front of the anion exchanger,and in front of some pre-desalination systems such as reverse osmosis,but in some places there is no need to add a carbon dioxide remover.All of these depend on the user's water quality and water type.

8.How many ways are there to prevent corrosion?

Answer:There are various anticorrosive methods such as rubber lining,epoxy,plastic lining,enamel,etc.

9.What equipment is the reverse osmosis device mainly composed of?

Answer:The reverse osmosis device is mainly composed 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(or optional),a water-producing flow meter,a concentrated water flow meter,a water-producing conductivity meter,membrane components(pressure vessel,reverse osmosis membrane element),concentrated water electric valve,concentrated water globe valve,water inlet pressure gauge,inter-segment pressure gauge,concentrated water pressure gauge,water-producing pressure gauge,reverse osmosis bracket,reverse osmosis control panel,reverse osmosis sampling panel,blasting membrane 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 footprint.

2The operation is simple and the noise is low.

3The water quality of the effluent is stable,and there is no phase change during the desalination process.

4 The pollution of the environment is small.

5 The applicable range is wide,200-40000mg/h.

The disadvantages of electrodialysis are：

1 Installation is more complicated.

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

3The low water recovery rate is generally 50%.

11.What brands of yin-yang heterogeneous ion exchange membranes are there?What are their characteristics?

Answer:Yin-yang heterogeneous ion exchange membranes mainly include Shanghai Chemical Plant Shuanghua brand heterogeneous ion exchange membrane,Lin'an heterogeneous ion exchange membrane,Beijing Shunyi heterogeneous ion exchange membrane,etc.;Good quality heterogeneous ion exchange membrane must have the following characteristics：

1 Choose strong transmittance.Selective permeability is the main indicator to measure membrane performance.It directly affects the current efficiency and desalination effect of the electrodialysis device,and its selective permeability is greater than 85%.

2 The film resistance is small.The electrodialysis device is composed 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.In the process of anionic ion migration,the concentrated water chamber will form a large concentration of ion solution;when polarization occurs,the PH value of the retention layer on both sides of the membrane will also change,especially the polar water participating in the chemical reaction will produce highly oxidizing oxygen and chlorine gas,so it is necessary to require the membrane to have strong chemical stability to extend the service life of the electrodialysis device.

4 Strong mechanical strength and dimensional stability.

5 Lower diffusion performance.

6 It has a high removal effect on strong electrolytes.

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

Answer:There are several types of electrodes for electrodialysis:titanium platinum-plated electrodes,titanium ruthenium-coated electrodes,graphite electrodes,and stainless steel electrodes;the electrodes vary according to the size of the electrodialysis body.Common engineering electrode specifications are:800×1600mm,400×1600mm,400×800mm,340×640mm,etc.

13.How is the distinction between fresh water chamber,concentrated water chamber,and polar water chamber?

Answer:A positive film,a separator,and a negative film form a membrane pair.The middle of the positive film and the negative film form a water chamber.Under the action of an electric field,the ions in the water chamber move in a directional manner.When the ions in the water chamber leave the water chamber through traction and the selected permeability of the membrane,the water chamber is called the fresh water chamber;on the contrary,when the ions enter the water chamber through traction and the selected permeability of the membrane,the water chamber becomes a concentrated water chamber;the water chamber generated between the yang film,the yin film or the separator and the electrode becomes the polar water chamber.

14.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,female membrane,male membrane,separator,electrode,clamping device,leak-proof rubber sheet,pickling system,flowmeter,pressure gauge,ABS pipe fittings,valve,SCR rectifier cabinet.

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

15.What is the principle of desalination of electrodialysis?

Answer:The anionic ion exchange membrane in the electrodialysis device has selective permeability.When the ions in the solution move in a directional manner under the action of an electric field,the selective permeability of the anionic ion exchange membrane is used to pass through or not through the corresponding exchange membrane.Concentrated water or fresh water is formed in different water chambers.