CN115710068A - Treatment method suitable for water quality of high-hardness and high-alkalinity drinking water - Google Patents
Treatment method suitable for water quality of high-hardness and high-alkalinity drinking water Download PDFInfo
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Abstract
The invention relates to a method for treating high-hardness and high-alkalinity drinking water, which belongs to the technical field of environment-friendly water treatment and comprises the following steps: lime descaling; (2) ultrafiltration: adopting external pressure type ultrafiltration to entrap suspended matters and bacteria and viruses in water; and (3) nano-filtering to remove hard scale and organic pollutants in water. The invention has the advantages that: aiming at the quality of drinking water with high hardness and easy scaling caused by water boiling, the front-end lime coagulation reduces the hardness and the alkalinity, so that the back-end nanofiltration operation pressure and the scaling risk are reduced, the recovery rate is higher, and the energy consumption is lower; the shorter process flow is that the lime is coagulated and then directly enters ultrafiltration, so that the medium filtration of the traditional water treatment after coagulation is reduced, and the investment is more saved and more economical; lime coagulation and ultrafiltration are used as pretreatment of nanofiltration, nanofiltration operation is more stable, pressure is lower, organic matters, hardness, alkalinity and the like in water are efficiently removed, the problem of obvious scaling of water heating is solved, and better product water quality is obtained.
Description
Technical Field
The invention relates to a drinking water treatment method, in particular to a treatment method suitable for the water quality of high-hardness and high-alkalinity drinking water, which aims at advanced treatment of the drinking water with obvious scale phenomenon in boiling water, can remove scaling substances in the water, improve the taste and the appearance of the drinking water, improve the safety of the drinking water and obtain the higher-quality drinking water, and belongs to the technical field of environment-friendly water treatment.
Background
The water quality requirement of drinking water can be divided into three stages of sanitation, safety and health. At present, the water quality safety stage is being realized, and the concept of healthy drinking is sprouting and developing.
In recent years, the national requirements on drinking water standards are continuously increased, and people not only meet the requirements on safety and sanitation of drinking water, but also require better taste and nutrition. The healthy water is safe and healthy, namely high-quality water, and retains natural nutrient substances beneficial to human bodies in source water on the basis of removing toxic and harmful pollutants in the water. However, with the rapid development of modern industry and agriculture and urbanization, the organic pollution of source water is increased, and the water has a serious threat to the safety of drinking water.
Water is a source of life, the quality of drinking water is closely related to human health, and drinking water safety is mainly divided into chemical safety and microbial safety, wherein firstly, the microbial safety needs to be ensured.
In the traditional disinfection process, pathogenic microorganisms in water are killed by a strong oxidant (mainly chlorine), but the traditional disinfection process is a main means for limiting the growth of bacteria in a pipe network by reducing the content of organic matters in factory water; although the effective chlorine content in the water is increased, the growth of bacteria can be controlled to a certain degree, but the growth cannot be avoided; moreover, the amount of added chlorine increases, and the amount of disinfection by-products increases greatly, which undoubtedly lowers the safety of drinking water.
Therefore, the content of organic matters in water is fully reduced, the dosage of chlorine can be reduced, disinfection by-products can be reduced, and the water quality safety in a pipe network can be better ensured.
The inorganic salt ions in the water are too high and harmful to human bodies, so that the content of organic matters in the factory drinking water is reduced, and the biological safety is ensured; and the content of over-standard inorganic salt ions such as sulfate, hardness, heavy metal and the like in the drinking water is also reduced sufficiently, so that the safety of the drinking water is guaranteed.
Regarding scale or hydrokali phenomena: when people boil water with tap water, white precipitates and white foam floating in the water are generated, and the white precipitates and the white foam can be accumulated at the bottom and the periphery of the kettle, and the kettle looks like being coated with a white shell after a long time. The white precipitates are so-called scale or water alkali, and the main components are substances such as calcium carbonate and magnesium carbonate, and the scale can cause uneven heating of a water heater, a boiler and a kettle, reduce heat transfer efficiency, is difficult to clean and can cause worry of people about the quality of tap water. The water scale and the calcium ions in the water are related to the content of the magnesium ions, the water scale is large, which indicates that the content of the calcium ions and the content of the magnesium ions in the water are high, and simultaneously, a certain amount of bicarbonate radicals and hydroxyl radicals exist in the water, namely, the alkalinity is high, the water scale is mainly formed because the pH value in the water rises when the water temperature rises, and the calcium ions and the magnesium ions in the water are easy to generate calcium carbonate and magnesium carbonate with the carbonate radicals hydrolyzed in the water, so that the scale is formed.
In recent years, with the concern of people on water quality and safety and health, micro-polluted organic matters in drinking water and disinfection byproducts generated by disinfection process treatment also cause harm to the safety of drinking water, and in the face of the problems, the membrane filtration technology has good advanced treatment effect advantage, the membrane filtration technology is gradually developed into a third-generation water purification technology, and at present, the membrane filtration technology widely applied to the field of water treatment mainly comprises microfiltration, ultrafiltration, nanofiltration and reverse osmosis.
Nanofiltration and reverse osmosis in membrane filtration technology are mainly used to remove organic pollutants and salt ions, and ultra (micro) filtration is usually used as a pretreatment of the former to reduce pollutants such as suspended matters and bacterial microorganisms in water. Wherein, the reverse osmosis membrane filtration technology has large operation pressure, high energy consumption, lower water yield than nanofiltration, and the recovery rate is usually only 75-80%. The nanofiltration intercepted molecular weight is between the ultrafiltration membrane and the reverse osmosis membrane, most harmful substances in water, including polycyclic aromatic hydrocarbon and disinfection byproducts, can be effectively removed, meanwhile, a proper amount of mineral elements beneficial to human health are reserved, the pressure is between the ultrafiltration membrane and the reverse osmosis, the water production flux is greater than the reverse osmosis, and the nanofiltration is more suitable for the treatment of drinking water.
For drinking water with low salt and low hardness and micro-pollutants, the membrane filtration technology has good treatment effect and higher recovery rate, however, for drinking water with high hardness and high alkalinity and the like generating scale, the high-recovery rate operation of nanofiltration or reverse osmosis can be maintained through a scale inhibitor with higher concentration, compared with the pressure and energy consumption required by the water quality of conventional drinking water, when low-pressure nanofiltration is selected, the generated water still generates obvious scale, and when high-desalination nanofiltration or reverse osmosis is selected, the energy consumption is higher, so that the system operation is not facilitated.
In the field of drinking water, no technology for removing scale is provided at present, and therefore, it is an urgent technical problem in the technical field to develop a treatment device and method suitable for the quality of high-hardness and high-alkalinity drinking water to remove scale substances therein, solve the scaling problem of boiling water, reduce organic pollutants in water, improve water safety and improve the quality of healthy drinking water.
Disclosure of Invention
One purpose of the invention is to provide a treatment device suitable for the water quality of high-hardness and high-alkalinity drinking water, which solves the scaling problem of high-hardness and high-alkalinity drinking water during boiling, reduces organic pollutants and produces higher-quality healthy and safe drinking water.
The above purpose of the invention is realized by the following technical scheme:
the utility model provides a be fit for processing apparatus of high basicity drinking water quality of high rigidity which characterized in that: comprises a lime coagulation water inlet pump, a lime coagulation device, an ultrafiltration water inlet tank, an ultrafiltration device, an ultrafiltration water inlet pump, a nanofiltration water inlet tank, a nanofiltration water inlet pump, a security filter and a nanofiltration device; the lime coagulation water inlet pump is connected with the lime coagulation device, the lime coagulation device is connected with the ultrafiltration water inlet tank, the ultrafiltration water inlet tank is connected with the ultrafiltration device through a pipeline and the ultrafiltration water inlet pump, the ultrafiltration device is connected with the nanofiltration water inlet tank through a pipeline, the nanofiltration water inlet tank is connected with the nanofiltration water inlet pump through a pipeline, the nanofiltration water inlet pump is connected with the security filter through a pipeline, and the security filter is connected with the nanofiltration device through a pipeline.
Preferably, the lime coagulation device is further provided with a lime mixer, and hand valves are arranged in front and at the back of the lime coagulation device.
Preferably, the lime coagulation device sets up 3 regions, be fast mixing district, slow mixing district and settling zone respectively, and the bottom in slow mixing district is equipped with the pipeline and deposits the district intercommunication.
Preferably, the lime coagulation device is also provided with a lime dosing device which comprises a lime dosing stirring dosing device, a coagulant stirring dosing device and a hydrochloric acid/sulfuric acid dosing device.
Preferably, the bottom of the rapid mixing zone of the lime coagulation device is provided with a rapid stirrer, and the rotating speed of the rapid stirrer ranges from 100 rpm to 200rpm.
Preferably, a feeding point of polyaluminium chloride (PAC) is arranged 30-40cm below the water surface at the top of the rapid mixing zone, and water automatically flows from the top of the rapid mixing zone, enters the slow mixing zone and is stirred for reaction.
Preferably, the slow mixing zone is also provided with an agitator, the agitation speed is 30-50rpm, and the reaction time is about 10min.
Preferably, the effluent at the bottom of the slow mixing zone flows into a settling zone, the settling zone is provided with an inclined pipe, and the settling residence time is 1.5-2 hours.
Preferably, the produced water of the lime coagulation device passes through an ultrafiltration device (ultrafiltration membrane) to obtain the produced water with turbidity of less than 0.1 NTU.
Preferably, the ultrafiltration device selects external pressure type ultrafiltration, and the membrane material is PVDF hollow fiber ultrafiltration.
Preferably, the ultrafiltration device operates at a flux of 60-80LMH, operates in a full-scale filtration mode, and has a recovery rate of >93%.
Preferably, the ultrafiltration device runs for 40-120 minutes, then backwashing is carried out, the running time is 5-15 days, and backwashing with sodium hypochlorite is carried out for 1 time.
Preferably, the filter element of the cartridge filter is a wire-wound filter element with the filtering precision of 5 um.
Preferably, the nanofiltration device is in a first-stage three-section structure, and each section is provided with 6-7 nanofiltration membranes, which can be adjusted according to the water production capacity.
Preferably, the nanofiltration membrane of the nanofiltration device is a low-pressure high-desalination nanofiltration membrane, the membrane material is a polyamide composite material, and the operating pressure is 0.3-0.7MPa.
The invention also aims to provide a treatment method suitable for the quality of high-hardness and high-alkalinity drinking water, which can deeply remove scale substances and organic pollutants, ensure that the drinking water is safer and healthier, reduce the energy consumption of membrane operation and improve the membrane recovery rate to 88-90% in stable operation.
The above purpose of the invention is realized by the following technical scheme:
a treatment method suitable for the quality of high-hardness and high-alkalinity drinking water comprises the following steps:
(1) Lime descaling: adding lime into the inlet water through a lime mixer, controlling the pH value of the lime-added mixing part to be 10-10.5, entering a rapid mixing zone, adding a coagulant PAC, carrying out coagulation reaction with lime and other suspended matters, and reacting for 10-20 min; entering a slow mixing area, and then entering a settling area through a central pipe for settling;
(2) And (3) ultrafiltration: adopting external pressure type ultrafiltration to entrap suspended matters and bacteria and viruses in water;
(3) Nano-filtration for removing hardness and scale and organic pollutants in water: and (2) selecting a low-pressure high-desalination polyamide composite nanofiltration membrane, wherein water firstly enters a nanofiltration section to produce water, the remaining section of concentrated water enters a second section to filter the produced water, and the second section of concentrated water enters a third section to filter the produced water to obtain high-quality produced water with the concentration of 88-90%.
Preferably, in the step (1), after the coagulation reaction, 20% of total hardness and 50-70% of total alkalinity in water are reduced.
Preferably, in step (1), the turbidity of the effluent is controlled to be less than 5NTU, and the pH value of the final effluent is 6.8-7.5.
Preferably, in the step (2), the turbidity of the outlet water is less than 0.1NTU, and the SDI value of the inlet water for nanofiltration is ensured to be less than 3.
Preferably, in the step (2), the ultrafiltration membrane module is a PVDF hollow fiber ultrafiltration membrane module.
Preferably, in step (2), the full-scale filtration operation mode is adopted, and the operation flux is 60-80LMH.
Preferably, in step (2), periodic backwashing and chemical dosing backwashing are adopted.
Preferably, in the step (2), the backwashing period is 40-120min, and the chemical dosing backwashing period is 5-15 days.
Preferably, in step (2), the backwashing process comprises air washing and water washing.
Preferably, in step (2), the backwash dosing agent is sodium hypochlorite in a chemically dosed backwash.
After the method is suitable for treating the water quality of high-hardness and high-alkalinity drinking water, the desalting rate is more than 90 percent, the removal rate of substances such as Ca and Mg causing scale formation is more than 95 percent, the removal rate of alkalinity in the water is also more than 80 percent, and the removal rate of organic matters in the water reaches over 75 percent, so that the water quality of produced water is obviously improved.
The desalting rate of the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water is more than 90 percent, the removal rate of substances such as Ca and Mg causing scaling is more than 95 percent, the removal rate of the total alkalinity and bicarbonate radical is more than 80 percent, and the removal rate of organic matters in the water reaches more than 75 percent, so that the water quality of the produced water is obviously improved. Under the condition of being matched with the scale inhibitor for adding, the recovery rate of the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water reaches 88-90 percent.
Has the advantages that:
the device and the method for treating the water quality of the high-hardness and high-alkalinity drinking water can solve the problem of scaling of the high-hardness and high-alkalinity tap water during boiling, remarkably improve the water quality of the tap water, obtain the drinking water which is safer, healthier and more sanitary, and meet and be better than the standard of domestic drinking water (GB 5749-2022).
The invention has the advantages that: 1) Aiming at the quality of drinking water with high hardness and high alkalinity and easy scaling when water is boiled, the system process is adopted, the front-end lime coagulation reduces the hardness and the alkalinity, so that the back-end nanofiltration operation pressure and the scaling risk are reduced, the recovery rate is higher, and the energy consumption is lower; 2) The shorter process flow is that the lime is coagulated and then directly enters ultrafiltration, so that the medium filtration (such as sand filtration) of the traditional water treatment after coagulation is reduced, and the investment is more saved and more economical; 3) Lime coagulation and ultrafiltration are used as pretreatment of nanofiltration, nanofiltration operation is more stable, compared with reverse osmosis operation, the pressure is lower, organic matters, hardness, alkalinity and the like in water are efficiently removed, the problem of obvious scaling of water heating is solved, and better product water quality is obtained.
The invention is further described below by means of the figures and the detailed description, without the embodiments of the invention being limited thereto. It should be understood that the embodiments described in this specification are only for explaining the invention and are not for limiting the invention patent.
Drawings
Fig. 1 is a schematic structural diagram of a treatment device suitable for the quality of high-hardness and high-alkalinity drinking water according to the present invention.
Description of the main reference numerals:
1 lime coagulating water inlet pump 2 lime coagulating device
3 ultrafiltration water inlet tank 4 ultrafiltration water inlet pump
5 ultrafiltration device 6 nanofiltration water inlet tank
7 receive and strain 8 safety filter of intake pump
9 nanofiltration device
Detailed Description
The components and the like in the following embodiments are, unless otherwise specified, conventional ones, and unless otherwise specified, all of the components and the like used in the present invention are commercially available.
Example 1
Fig. 1 is a schematic structural diagram of a device suitable for treating high-hardness and high-alkalinity drinking water according to the present invention; the system comprises a lime coagulation water inlet pump 1, a lime coagulation device 2, an ultrafiltration water inlet tank 3, an ultrafiltration device 4, an ultrafiltration water inlet pump 5, a nanofiltration water inlet tank 6, a nanofiltration water inlet pump 7, a security filter 8 and a nanofiltration device 9, wherein the lime coagulation water inlet pump 2 is connected with the ultrafiltration water inlet tank 4; the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water comprises a lime coagulation water inlet pump 1, a lime coagulation device 2, an ultrafiltration water inlet tank 3, an ultrafiltration device 4, an ultrafiltration water inlet pump 5, a nanofiltration water inlet tank 6, a nanofiltration water inlet pump 7, a security filter 8 and a nanofiltration device 9; high-hardness and high-alkalinity drinking water to be treated enters a lime coagulation device 2 for treatment through a lime coagulation water inlet pump 1, the lime coagulation device 2 is connected with an ultrafiltration water inlet tank 3, the ultrafiltration water inlet tank 3 is connected with an ultrafiltration device 5 through a pipeline and an ultrafiltration water inlet pump 4, the ultrafiltration device 5 is connected with a nanofiltration water inlet tank 6 through a pipeline, the nanofiltration water inlet tank 6 is connected with a nanofiltration water inlet pump 7 through a pipeline, the nanofiltration water inlet pump 7 is connected with a security filter 8 through a pipeline, and the security filter 8 is connected with a nanofiltration device 9 through a pipeline;
the lime coagulation device 2 is provided with 3 areas, namely a fast mixing area, a slow mixing area and a settling area, wherein the bottom of the slow mixing area is provided with a pipeline communicated with the settling area;
the lime coagulation device 2 is also provided with a lime dosing device which comprises a lime dosing stirring dosing device, a coagulant stirring dosing device and a hydrochloric acid/sulfuric acid dosing device;
the bottom of the rapid mixing area of the lime coagulation device 3 is provided with a rapid stirrer, and the rotating speed of the stirrer is 100-200rpm;
a polyaluminium chloride (PAC) feeding point is arranged 30-40cm below the water surface at the top of the rapid mixing zone, and water automatically flows from the top of the rapid mixing zone, enters the slow mixing zone and is stirred for reaction;
a stirrer is also arranged in the slow mixing area, the stirring speed is 30-50rpm, and the reaction time is about 10min;
the effluent water at the bottom of the slow mixing zone flows into a settling zone, the settling zone is provided with an inclined pipe, and the settling residence time is 1.5-2 hours;
lime is added through a lime mixer and is mixed with source water, the number of the lime mixers is 2, one lime mixer is used for standby, hand valves are arranged in front and at the back of the lime mixers, and switching and maintenance are facilitated;
the produced water of the lime coagulation device passes through an ultrafiltration device (ultrafiltration membrane) to obtain the produced water with turbidity less than 0.1 NTU;
the ultrafiltration device selects external pressure type ultrafiltration, and the membrane material is PVDF hollow fiber ultrafiltration;
the ultrafiltration operation flux is 60-80LMH, the full-scale filtration mode is adopted for operation, and the recovery rate is more than 93 percent;
after the ultrafiltration operation is carried out for 40-120 minutes, backwashing is carried out, the operation is carried out for 5-15 days, and backwashing with sodium hypochlorite is carried out for 1 time;
the filter element of the security filter 8 is a wire-wound filter element with the filtering precision of 5 um;
the nanofiltration device 9 is a first-stage three-section nanofiltration membrane, and each section is provided with 6-7 nanofiltration membranes which can be adjusted according to the production water amount;
the nanofiltration membrane is a low-pressure high-desalination nanofiltration membrane, the membrane material is a polyamide composite material, and the operating pressure is 0.3-0.7MPa.
The invention also aims to provide a treatment method suitable for the water quality of high-hardness and high-alkalinity drinking water, which can deeply remove scale substances and organic pollutants, ensure that the drinking water is safer and healthier, reduce the energy consumption of membrane operation and improve the membrane recovery rate to 88-90% in stable operation.
The above purpose of the invention is realized by the following technical scheme:
a treatment method suitable for the quality of high-hardness and high-alkalinity drinking water comprises the following steps:
(1) Lime descaling: adding lime into inlet water through a lime mixer, controlling the pH value of a lime adding mixing part to be 10-10.5, entering a rapid mixing area, adding a coagulant PAC, carrying out coagulation reaction with lime and other suspended matters, and reducing the total hardness of about 20% and the total alkalinity of 50-70% in the water after the reaction for 10-20min so as to reduce the risk of scaling of water boiling and nanofiltration concentrated water; entering a slow mixing area, entering a precipitation area through a central pipe, precipitating, controlling the turbidity of effluent to be less than 5NTU, finally adding acid into the effluent, and controlling the pH value to be 6.8-7.5;
(2) And (3) ultrafiltration: external pressure type ultrafiltration is adopted to intercept suspended matters and bacteria and viruses in water, the turbidity of outlet water is less than 0.1NTU, and the SDI value of inlet water of nanofiltration is ensured to be less than 3; the membrane component is a PVDF hollow fiber ultrafiltration membrane component;
adopting a full filtration operation mode, wherein the operation flux is 60-80LMH;
maintaining stable operation of ultrafiltration by periodic backwashing and chemical dosing backwashing, wherein the backwashing period is 40-120min, the chemical dosing backwashing period is 5-15 days, the backwashing process comprises air washing and water washing, and in the chemical dosing backwashing, sodium hypochlorite is selected as a main backwashing dosing agent;
(3) Nano-filtration for removing hardness and scale and organic pollutants in water: the method comprises the steps of selecting a low-pressure high-desalting polyamide composite nanofiltration membrane, wherein water firstly enters a first-stage nanofiltration water production section, the remaining first-stage concentrated water enters a second-stage nanofiltration water production section, the second-stage concentrated water enters a third-stage nanofiltration water production section, and the front end of the second-stage concentrated water is provided with lime coagulation and ultrafiltration as nanofiltration pretreatment guarantee, and high-quality water production of 88-90% is obtained after nanofiltration is subjected to first-stage and third-stage treatment.
After the method is suitable for treating the water quality of high-hardness and high-alkalinity drinking water, the desalting rate is more than 90 percent, the removal rate of substances such as Ca and Mg causing scale formation is more than 95 percent, the removal rate of alkalinity in the water is also more than 80 percent, and the removal rate of organic matters in the water reaches over 75 percent, so that the water quality of produced water is obviously improved.
The desalting rate of the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water is more than 90 percent, the removal rate of substances such as Ca and Mg causing scaling is more than 95 percent, the removal rate of the total alkalinity and bicarbonate radical is more than 80 percent, and the removal rate of organic matters in the water reaches more than 75 percent, so that the water quality of the produced water is obviously improved. Under the condition of being matched with the scale inhibitor, the recovery rate of the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water reaches 88-90 percent.
Application example 1
A water source adopted by a certain water plant in Jiangsu has the characteristics of high hardness and high alkalinity, after the water source is subjected to traditional coagulation, precipitation and filtration treatment, white scaling substances appear in boiled water after external supply to users, the appearance and the taste are influenced, the long-term use of a water heater and a heat exchanger is influenced, particularly for tap water produced by external supply beverage enterprises, due to the reasons of high hardness, high alkalinity and the like, the water quality needs to be improved through advanced treatment, and therefore the device disclosed by the invention is used for carrying out advanced treatment.
Total water inflow of 15m 3 The method comprises the following steps that (h) tap water of a water plant is subjected to advanced treatment, the tap water enters a device through a lime coagulation water inlet pump and then enters a lime coagulation, ultrafiltration and nanofiltration system, and the water quality before and after treatment is as shown in the following table 1:
TABLE 1
As can be seen from Table 1, after the treatment by the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water, the conductivity is reduced from 1070us/cm to 85us/cm, the desalination rate reaches 92%, the removal rate of the total hardness and the total alkalinity respectively reaches 96% and 91%, the removal rate of CODmn indexes representing organic pollutants also reaches more than 87%, water is produced by nanofiltration, scale does not appear in boiled water, the water quality is obviously improved, and the treatment device can be directly used by beverage enterprises.
Application example 2
The hardness and alkalinity of inlet water of a certain water plant are higher, the pH value of source water is 8.0-8.5, and the amount of suspended substances in the source water is more, the turbidity is as high as 10NTU, and when drinking water is externally supplied for boiling, obvious white scaling substances appear, so that the surface of hot water becomes turbid, and the use worry of residents is caused; the water plant carries out a pilot test of upgrading and transforming the traditional drinking water treatment process, adopts the process of the invention to carry out advanced treatment, and carries out the following steps of 1:1 blending.
The testing is carried out by using the treatment device suitable for the water quality of the high-hardness and high-alkalinity drinking water, which is disclosed by the invention:
the water inflow is 12m 3 The water quality of inlet and outlet water is shown in the following table 2 after being treated by the treatment device suitable for the water quality of high-hardness and high-alkalinity drinking water.
TABLE 2
As can be seen from table 2, after the treatment device suitable for the water quality of the high-hardness high-alkalinity drinking water disclosed by the invention is used for treating the incoming water, the total desalination rate, the total hardness removal rate and the total alkali removal rate of nanofiltration produced water are all more than 90%, the removal rate of CODmn is also more than 80%, and the water quality of the produced water is obviously improved; even with ultrafiltration water production 1:1, the blended effluent can still be ensured not to generate scale when being boiled after blending, the problem of scale formation caused by high hardness and high alkalinity in water is solved, and safer and healthier drinking water quality is obtained.
The invention has the advantages that: aiming at the quality of drinking water with high hardness and easy scaling caused by water boiling, the front-end lime coagulation reduces the hardness and the alkalinity, so that the operating pressure and the scaling risk of nanofiltration at the rear end are reduced, the recovery rate is higher, and the energy consumption is lower; the process flow is shorter, the lime is directly subjected to ultrafiltration after coagulation, the medium filtration of the traditional water treatment after coagulation is reduced, and the investment is more saved and more economical; lime coagulation and ultrafiltration are used as pretreatment of nanofiltration, nanofiltration operation is more stable, pressure is lower, organic matters, hardness, alkalinity and the like in water are efficiently removed, the problem of obvious scaling of water heating is solved, and better product water quality is obtained.
The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims.
Claims (10)
1. A treatment method suitable for the quality of high-hardness and high-alkalinity drinking water comprises the following steps:
(1) Lime descaling: adding lime into the inlet water through a lime mixer, controlling the pH value of the lime-added mixing part to be 10-10.5, entering a rapid mixing zone, adding a coagulant PAC, carrying out coagulation reaction with lime and other suspended matters, and reacting for 10-20 min; entering a slow mixing area, and then entering a settling area through a central pipe for settling;
(2) And (3) ultrafiltration: adopting external pressure type ultrafiltration to entrap suspended matters and bacteria and viruses in water;
(3) Nano-filtration for removing hardness and scale and organic pollutants in water: and (2) selecting a low-pressure high-desalination polyamide composite nanofiltration membrane, wherein water firstly enters a nanofiltration section to produce water, the remaining section of concentrated water enters a second section to filter the produced water, and the second section of concentrated water enters a third section to filter the produced water to obtain high-quality produced water with the concentration of 88-90%.
2. The method for treating drinking water with high hardness and high alkalinity as claimed in claim 1, wherein in step (1), after coagulation reaction, the total hardness of water is reduced by 20% and the total alkalinity is reduced by 50-70%.
3. The method for treating the water quality of the drinking water with high hardness and high alkalinity as claimed in claim 2, wherein in the step (1), the turbidity of the outlet water is controlled to be less than 5NTU after the coagulation reaction.
4. The method for treating the quality of the drinking water with high hardness and high alkalinity as claimed in claim 3, wherein in the step (1), the pH value of the final effluent after coagulation reaction is 6.8-7.5.
5. The method for treating high hardness and high alkalinity drinking water quality according to claim 4, wherein in step (2), the effluent turbidity is less than 0.1NTU, and the inlet SDI value of nanofiltration is less than 3.
6. The method for treating the quality of the drinking water with high hardness and high alkalinity as claimed in claim 5, wherein, in the step (1), after the coagulation reaction, the ultrafiltration membrane component is a PVDF hollow fiber ultrafiltration membrane component.
7. The method for treating the quality of the drinking water with high hardness and high alkalinity as claimed in claim 6, wherein in the step (1), after the coagulation reaction, the backwashing period is 40-120min, and the chemical dosing backwashing period is 5-15 days; the backwashing process comprises air washing and water washing; in chemical dosing backwash, the backwash dosing agent is sodium hypochlorite.
8. The method for treating the water quality of the drinking water with high hardness and high alkalinity as claimed in claim 7, wherein in the step (2), a full-filtering operation mode is adopted, and the operation flux is 60-80LMH.
9. The method for treating the quality of the drinking water with high hardness and alkalinity according to claim 8, wherein in the step (2), periodic backwashing and chemical dosing backwashing are adopted.
10. The method for treating the quality of the drinking water with high hardness and high alkalinity as claimed in claim 9, wherein in the step (2), external pressure type ultrafiltration is selected, and the membrane material is PVDF hollow fiber ultrafiltration; in the step (3), the nanofiltration adopts a first-stage three-section, and each section is provided with 6-7 nanofiltration membranes; the nanofiltration membrane is a low-pressure high-desalination nanofiltration membrane, the membrane material is a polyamide composite material, and the operating pressure is 0.3-0.7MPa.
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