Water is the source of life, water accounts for 70% of the human body composition. Scientific research shows that the average daily water demand of adults is more than 2500ml, which can be said that water quality is the basic guarantee of health.

Turn on the tap and the tap water flows out slowly. While enjoying the convenience brought by modern life, have we ever thought about the process of these tap water flowing into thousands of households from rivers and lakes to thousands of households. Sometimes the water flowing out is as white as milk, and there are a lot of bubbles in it, which gives out the flavor of disinfection water, How did these phenomena form, which took a few minutes to recover from clarity?

Friends from the countryside may know that there was no running water before. There was a big water tank in the family. My father leaned and his shoulder was squeaky. He picked water from the pond and went home, poured it into the water tank and put alum to rest for a while, and the bottom of the tank began to precipitate. This is the most primitive water treatment technology in the countryside.

Later, we found that the water tanks were concentrated together, and the special personnel uniformly beat alum, which was more efficient. The bigger the water tank was, the more water tank became a water plant, and the more efficient medicine gradually replaced alum.

At present, most water plants adopt the methods of unified disinfection, sedimentation and filtration from the water source water pumping and water plants, and finally pump them to the user's house, among which the following 6 drugs are mainly used:

1. HClO hypochlorite is generated by adding chlorine gas in the chlorine reservoir into water, which has strong sterilization and disinfection ability. According to the different places of dosing, it can be divided into pre chlorination and post chlorination.

Figure 1. chlorine storage

2. PAC polyaluminium chloride is stored in the dosing room, pumped to the mixing tank and fully stirred with water. The purpose is to make the fine suspended particles and colloid ions in water unstability, gather, flocculation, coagulation and precipitation, and achieve the purification treatment effect.

Ozone O3, produced by oxygen discharge of O2, is a strong oxidant. It can be used to sterilize and disinfect algae cells and reduce their content. According to the position of the dosing, it can be divided into pre (front) ozone and post ozone dosing point.

There are many advantages of using ozone for water treatment, such as good sterilization effect, poor stability and easy decomposition, without toxic residue, but a large number of use brings problems, such as corrosion of metal pipes, and more importantly, a certain amount of bromate is produced. You know, this is potential carcinogen. The current treatment method of water plant is to use a certain amount of H2O2 to deal with it, It will be mentioned later.

Figure 2. the carburetor of oxygen tank is frosted even in summer

Figure 3. ozone generator (oxygen is powered to produce ozone)

Figure 4. ozone dosing point in the pool

4. H2O2 hydrogen peroxide, strong oxidant, has the ability of sterilization, but it is mainly used to deal with bromate. After adding water, it can form a competitive relationship with O3, so as to avoid bromate formation. It is often added in the month with poor water quality.

Bromate is a potential carcinogen, but it is easy to decompose when heated. It is not only tap water, but also exists in most bottled water on the market. It is meaningless to talk about toxicity when it is separated from dose. It is the most hygienic to be calm and cool.

Figure 5. hydrogen peroxide dosing system

5. KMnO4 potassium permanganate, which is used to oxidize organic matter, sterilize and sterilize. If more water is added, it will turn red, and the dosage shall be strictly controlled.

6. PAM polyacrylamide, flocculant, is only used in the balance tank of sludge system, because it is expensive.

After understanding some chemicals in the water treatment process, there are three problems in front of you:

Where does the water come from?

What does water do here?

Where is the water going?

Please fasten your seat belt and drive ahead.

1. water source - water intake pump house - water purification plant, in a word, high lift, high-power water pump is waiting for three types of water that meet the requirements of national standards. When selecting the water pump, consider some head loss and control the incoming water quantity according to the user demand.

Fig. 6. water intake pump room in a place

2. potassium permanganate pre ozone pre chlorination, in which potassium permanganate and chlorine are added by setting up the adding point on the main inlet pipe, and pumping the drug directly to the pipeline for mixing with water. There are separate structures for pre ozone. The tank body is fully mixed and the tail gas shall be recycled and destroyed.

Figure 7. pre ozone contact pool

Figure 8. ozone dosing device

Figure 9. chlorine dosing machine

3. mechanical mixing mixing tank, PAC polychloride is added in the tank, and the mixer is mixed mechanically.

Figure 10. the hula ring in the water is the annular dosing pipe, and the mixer is obvious

4. flocculation flat flow sedimentation tank, folding plate type and rotary diaphragm type are all available. Fine suspended particles and colloid ions in water will flocculate and precipitate here. Special structure will increase the flow length, increase contact area and time, increase collision probability, and improve the polymerization sedimentation effect. The supernatant will flow into the filter through the collecting tank.

Figure 11. folding plate type, upper shading to reduce moss breeding, with general effect

Figure 12. rotary diaphragm type

Figure 13. sedimentation tank

Figure 14. flocculation and sedimentation (snowflake point)

So friends asked, this flocculation sedimentation tank is not easy to dirty, do you wash the pool regularly? At this time, they realized the wisdom of these water workers, who invented mud scraper, mobile black technology, and the mud deposited at the bottom of the pool was nowhere to hide.

Figure 15. mud scraper

Figure 16. mud scraper

Figure 17. mud water from mud scraper is discharged to sludge system

5. filter (2 general speed, 1 V-type), after flocculation and sedimentation, water enters the filter, and the filter material is quartz sand, which can filter out suspended substances in water.

Figure 18. filter

6. the water potential energy of the lifting pump room and ordinary sand filter is low, and it cannot flow into the ozone contact tank and activated carbon filter by gravity. In this case, the larger potential energy needs to be obtained by the lifting pump so as to successfully complete the subsequent process.

Fig. 19. axial flow lifting pump (about 2m high, q=4800m3/h, 6 sets in total)

7. ozone contact pool, the water flowing after upgrading will be put into the ozone contact pool, and ozone will be added for sterilization and disinfection. This stage is post ozone.

8. the activated carbon filter is 2.2m thick activated carbon +0.5m quartz sand +0.2m thick supporting layer from the top to the bottom. The activated carbon filter material can greatly improve the water quality. After filtration, the water is distributed to the clean water tank through the confluence of the central channel of the pipe gallery.

Figure 20. the water after activated carbon treatment is very clear. It can be seen that blue-green is the reason for refraction.

9. the water from the clean water tank suction well secondary pump house, the water flow of the clean water tank enters the suction well, the pump in the secondary pump room is ready for standby, and press to start. Clean and sanitary tap water is transported to thousands of households through the municipal water supply pipe.

Figure 21. secondary pump house

The above is the process of water treatment plant. Is it possible to re understand the water king? Let's compare the changes of water quality from scratch:

Figure 22. raw water enters the plant without any treatment, and it is turbid and blackened

Figure 23. is the water after flocculation and sedimentation slightly acceptable

Figure 24. water to be delivered to the user's home is clean and sanitary

But this is not all. After you have seen it, would you like to ask:

In the case of long-term filtration, whether quartz sand or activated carbon will become dirty, how to clean up the suspended matter mixed in the filter material?

Where is the sludge water from the scraper?

Don't worry. Let's start with two concepts:

Backwash system   Sludge disposal system

First, the filter water flows from top to bottom in space, and the backwash system is bottom-up, generally with water flushing + gas flushing.

The water of the water flushing system comes from the clean water pool. Why is it so wasteful to use clean water? This is because if you brush the bowl with dirty water, it is not clean. Even if the appearance is clean, you dare not directly bring rice.

Air flushing is to blow air compression into the bottom of filter material by air compressor. Bubbles will roll up and down the filter material during the rising process in water, and then clean impurities out. After backwashing, water enters the recovery tank. After water quality detection reaches the standard, it can be re connected to the main water inlet pipe of the water plant, and then go through the above process again. Therefore, it is named recovery tank. In case of emergency, the valve can also be switched into rainwater system.

As for sludge disposal system, as the name implies, it is used to treat sludge water produced by water plant.

It is mainly produced by the sludge scraper in the sedimentation tank. The sludge water discharged by the scraper enters the drainage and discharge tank, then pumps it to the distribution well, which is distributed to the concentration tank. The sludge water is deposited in the concentration tank. The water with low sludge content in the upper part will be discharged to the rainwater system. The sludge water in the lower part is too large, and it will be combined into the balance tank, and then pumped into the centrifuge in the dewatering room, and the mud water is separated, The water is discharged by the rainwater system, and the mud cake is piled up in the sludge shed for regular cleaning.

Figure 25. buried drainage and mud drainage pool, underground pool body, surface green grassland

Figure 26. thickener and annular track mud scraper

Figure 27 centrifuge

Figure 28. sludge shed being cleaned

The process pipelines and valves of water plant are complex. Different tasks need different valve opening and closing combinations. Now these can be controlled remotely. It is necessary to say that the progress of technology greatly improves the productivity, and the water treatment process will be more excellent in the future.

Figure 29. remote monitoring of water treatment

The production system, backwash system and sludge system of water purification plant simply understand here. The key and difficult point of water plant operation is to continuously output the qualified purified water under the condition of variable raw water quality, and it is a dynamic management. When the seasons, temperature, microorganisms and other external conditions change, the raw water composition also changes, such as the arrival of summer, the algae and microbial content erupt, The chlorine content added should be increased correspondingly, but to what extent can we guarantee that it can not only play the role of sterilization and disinfection, but also not excessive residual chlorine. These are not only calculated by theory, but also the accumulated experience of numerous water workers all the year round. Here I salute all water workers, and it is your efforts to benefit the society.

Many friends of the strange mushroom shaped building in the picture have seen it. This is the sign of water plant. The progress of science and technology makes it gradually withdraw from the historical stage until all of them disappear. The previous backwashing process is to pump the water to the top of the water tower to store high potential energy. After opening the gate, gravity backwashing is used for the benefit. Now, the process is directly backwashed by water pump and no longer passes through the water tower.

Finally, I return to the following questions:

Turn on the tap and find that water is like milk. This is because air is mixed into the pipeline when water is stopped for maintenance. When water supply is again, the water pressure is too large to press the air into the water body. When the light is released from the tap, it looks milky white due to the refraction of light, and it can be kept for two minutes without any influence.

The water body has 84 disinfection water taste, which is the taste of HClO. In order to ensure that the water body is continuously free from bacterial pollution in municipal pipelines, chlorine is still added before being sent to the user's house. There is residual chlorine (chlorine element) in the water, and it is unnecessary to worry. These are all indicators of water quality monitoring. The dosage will be strictly controlled and it will not taste after two minutes of standing.

Drinking water is drinking water, can not be a nutritional product, can not expect to supplement trace elements, iron deficiency is more used in hot pot fried vegetables, what mineral water, alkaline water gimmicks on the market is more than practical significance, not necessarily better than cold open.

Normal tap water is colorless and transparent. If the water is red and there is obvious precipitation after being put in place, the rate is probably due to the mixing of sediment after the pipeline has been rusted or damaged for a long time, and it should be reported to the water company in time.