System and process for removing nitrate from water during the diversion period

Abstract

The application provides a system and process for removing nitrate from water in dry season. The process for removing nitrate from water in dry season comprises the following steps: step S1, judging the water period of raw water; when the concentration of nitrate in raw water changes in the range of 30-90 mg / L, the raw water is in wet season; when the concentration of nitrate in raw water changes less than 30 mg / L, the raw water is in dry season; step S2, pretreatment of raw water; step S3, nitrate removal treatment of raw water; step S31, when the raw water is in dry season, dry season treatment process is used for nitrate removal treatment of raw water; step S31', when the raw water is in wet season, wet season treatment process is used for nitrate removal treatment of raw water; step S4, physical separation and impurity removal of raw water after nitrate removal treatment in step S3; step S5, the raw water after impurity filtration treatment in step S4 is process water, and the process water is stored.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a system and process for removing nitrate from water during water diversion period. BACKGROUND

[0002] According to the detection results of rural drinking water in recent years, the nitrate content of water source in rural areas is seriously excessive. High nitrate content in drinking water can increase the risk of cancer and the rate of fetal malformation. At present, the residents in the villages where the nitrate content exceeds the standard use single household water purifiers, and the waste water amount is as high as 80%, which is directly discharged, causing serious waste of water resources.

[0003] Currently, effective methods for removing nitrate from drinking water include denitrification, ion exchange and physical and chemical methods. Biological denitrification uses denitrifying bacteria to reduce nitrate to nitrogen under anaerobic conditions, but the process is complex and the cost is high. Chemical denitrification uses reducing agents to reduce nitrate in water to nitrogen for removal, but its practicability is limited due to mass transfer.

[0004] The most commonly used methods on the market are ion exchange and physical and chemical methods. Ion exchange method has high treatment precision and can achieve below 1 ppm; the adsorption capacity is large, and the saturated adsorption capacity of nitrate (calculated as N) can reach more than 10 g / L; the resin preferentially exchanges nitrate, and the exchange capacity of nitrate is not affected by the content of sulfate in water, but the cost of ion exchange resin is high. Physical and chemical method mainly uses reverse osmosis method, which is simple and convenient, but has no selectivity for nitrate removal and produces a lot of concentrated inorganic salt wastewater.

[0005] Therefore, it is necessary to find an effective and economical way to remove nitrate from water. The Chinese patent document with publication number CN209567955U discloses a system for removing nitrate particles from mine water, which forms two-stage concentration reduction through two-stage reverse osmosis devices, improves the concentration of nitrate ions in concentrated water, and connects an A / O pool for preliminary nitrogen removal treatment, then uses an ion exchanger for nitrogen removal treatment again, and then mixes the treated water with the water produced by the reverse osmosis unit in the water production pool, and discharges after meeting the standard. The Chinese patent application with publication number CN115611462A discloses a method for recycling and treating ammonium calcium nitrate and ammonium nitrate condensate wastewater, which pretreats the ammonium calcium nitrate and ammonium nitrate condensate wastewater, then feeds it into a heat exchanger for heat exchange, then transports the wastewater after heat exchange to a precision filter to filter out suspended substances, and then sequentially transports it to a first reverse osmosis device and a second reverse osmosis device for deep treatment and discharge.

[0006] The common methods for removing nitrate in water on the market include ion exchange method, reverse osmosis method and the like. In order to remove nitrate to a dischargeable concentration range, ion exchangers and reverse osmosis devices are usually used in series, so that the wastewater is treated for multiple times to reach the standard before being discharged. However, the concentration of nitrate in raw water varies with different water periods, and especially in the wet period of raw water, the nitrate index fluctuates greatly. For this case, the method of refluxing multiple times is usually used to remove nitrate, which is extremely high in anion exchange resin and electricity consumption, and the operation cost is high. When it is in the dry period, the original system is continued to be used, which is not conducive to the operation of the system. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a system and process for removing nitrate in water in different water periods. The process can treat raw water differently according to different water periods, saving cost and time for removing nitrate.

[0008] The first aspect of the present application provides a process for removing nitrate in water in different water periods, which comprises the following steps:

[0009] Step S1, judging the water period of raw water:

[0010] When the concentration of nitrate in raw water varies in the range of 30 mg / L to 90 mg / L, the raw water is in the wet period,

[0011] When the concentration of nitrate in raw water varies less than 30 mg / L, the raw water is in the dry period;

[0012] Step S2, pretreatment of raw water;

[0013] Step S3, nitrate removal treatment of raw water:

[0014] Step S31, when the raw water is in the dry period, a dry period treatment process is used to remove nitrate from the raw water;

[0015] Step S31', when the raw water is in the wet period, a wet period treatment process is used to remove nitrate from the raw water,

[0016] Step S31', when the raw water is in the wet period, a wet period treatment process is used to remove nitrate from the raw water,

[0017] Step S4, physical separation and impurity removal of the raw water after the nitrate removal treatment in the above step S3;

[0018] Step S5, the raw water after the impurity filtration treatment in the above step S4 is used as process water, and the process water is stored.

[0019] Further, the dry period treatment process in step S31 comprises:

[0020] Step S31-1, contact-mixing ion exchange treatment is performed on raw water;

[0021] Step S31-2, the ion exchange resin saturated in step S31-1 is transported to perform ion exchange resin regeneration;

[0022] Step S31-3, the ion exchange resin regenerated in step S31-2 is transported to perform contact-mixing ion exchange treatment on raw water, wherein

[0023] The step S31-1, step S31-2 and step S31-3 are performed synchronously and form a cycle.

[0024] Further, the treatment process in the step S31' includes:

[0025] Step S31'-1, nitrate in raw water is preliminarily removed;

[0026] Step S31'-2, reverse osmosis treatment is performed on the raw water after the above step.

[0027] Further, the process for removing nitrate in water in the dry period also includes: step S6, backwashing process.

[0028] According to the second aspect of the present application, a system for removing nitrate in water in the dry period is provided, the dry period includes a dry period and a wet period, the nitrate concentration of raw water in the dry period changes in the range of less than 30 mg / L, the nitrate concentration of raw water in the wet period changes in the range of 30 mg / L to 90 mg / L, the system includes: a control unit, and a raw water process unit, a pretreatment unit, a dry period treatment unit, a wet period treatment unit, a physical separation unit and a product water process unit electrically connected with the control unit; the dry period treatment unit and the wet period treatment unit are arranged in parallel downstream of the raw water process unit, the physical separation unit is located downstream of the wet period treatment unit and the dry period treatment unit, and the product water process unit is located downstream of the physical separation unit; wherein

[0029] The raw water process unit is provided with a nitrate concentration detection device;

[0030] The dry period treatment unit includes a contact-mixing ion exchange treatment module and a resin regeneration module.

[0031] Further, the contact-mixing ion exchange treatment module includes a treatment tank, a stirrer installed inside the treatment tank and a stirrer motor connected to the upper end of the stirrer, a first raw water inlet, a process water outlet, a resin inlet, a resin outlet and a desalted water outlet are arranged on the treatment tank, and the contact-mixing ion exchange treatment module is provided with at least two groups.

[0032] Further, the resin regeneration module comprises a resin collection part, a resin regeneration part and a resin supply part arranged in series through pipelines, the resin collection part is communicated with the resin outlet, the resin supply part is communicated with the resin inlet, and wherein

[0033] The resin regeneration part comprises a regenerant supply device and a regeneration reaction tank, and the regeneration reaction tank is provided with a first process water inlet communicated with the water production process unit through a pipeline;

[0034] The regenerant supply device comprises a regenerant stock solution storage tank, a regenerant preparation and supply tank, a regenerant recovery tank and a water jet, wherein the water jet is provided with a desalted water inlet, a regenerant inlet and a mixed liquid outlet, the desalted water inlet is connected with the desalted water outlet through a desalted water discharge pipeline, the regenerant inlet is connected with the regenerant stock solution storage tank through a pipeline, the regenerant preparation and supply tank is provided with a mixed liquid inlet communicated with the mixed liquid outlet through a pipeline, a second process water inlet communicated with the water production process unit through a pipeline and a regenerant outlet communicated with the regeneration reaction tank through a pipeline, and the regenerant recovery tank is communicated with the regeneration reaction tank through a pipeline.

[0035] Further, the dry season treatment unit further comprises a constant temperature oscillator arranged upstream of the contact-mixing ion exchange treatment module.

[0036] Further, the wet season treatment unit comprises a resin tank and a reverse osmosis treatment device arranged downstream of the resin tank, the resin tank is provided with a third raw water inlet, the reverse osmosis treatment device is provided with a second water outlet, and the reverse osmosis treatment device is provided with an RO membrane.

[0037] Further, a backwashing unit is arranged between the physical separation unit and the water production process unit, and the pretreatment unit comprises a filter tank and a desorption tank.

[0038] Based on the existing experience, the nitrate index fluctuation in wet season and dry season is different, in the case of large change of nitrate concentration in wet season, the ion exchange treatment needs to be backflowed for multiple times, the cathode ion resin and electricity consumption are large, and the operation cost is high, while in the dry season, the continuous cost is high when the reverse osmosis device is used for treatment due to small change of nitrate index, therefore, a method which can improve the removal rate of nitrate and reduce the operation cost is needed.

[0039] Based on this, the system and process for removing nitrate in water in the water period provided by the application distinguish whether the raw water is in the wet season or the dry season by detecting the concentration change range of nitrate in the raw water through the control unit, and then distribute the raw water to different processing units according to the different water periods for processing in different ways. The problem of large fluctuation of nitrate index of groundwater, poor treatment effect of raw water with different nitrate indexes by using one system, and high economic cost are solved.

[0040] The system for removing nitrate in water in the water period of the application adopts parallel arrangement of the wet season processing unit and the dry season processing unit, distributes the raw water to the above different units for processing according to the different water periods, wherein the dry season processing unit adopts the contact mixed type exchange processing device, the wet season processing unit adopts the reverse osmosis processing device, and the processing mode is automatically switched through the control unit, based on the "dynamic monitoring, data platform analysis" technology, and a combined processing mode of two processes is constructed. The resin regeneration module is also arranged in the dry season processing unit, and the ion exchange resin is regenerated and processed according to the saturation degree and regeneration period of the ion exchange resin, so as to improve the stability of the processing unit and the use efficiency of the ion exchange resin.

[0041] In the application, the dry season processing unit uses the contact mixed type ion exchange processing module, adopts the mixed form of silver ion exchange resin and cation exchange resin, can completely remove nitrate and other ions in water, and achieves the purpose of completely purifying water. The water production process unit in the system not only serves as a storage unit for the water to be discharged, but also is connected with the regeneration reaction tank and the regeneration agent preparation supply tank through a pipeline, and can also backwash the physical separation unit, so as to utilize the treated purified water, save the cost, and greatly save the resources.

[0042] The process for removing nitrate in water in the water period provided by the application distinguishes whether the raw water is in the wet season or the dry season according to the fluctuation of the concentration change range of nitrate, and then removes nitrate in the raw water by using different processing methods. The design scheme will be concentrated at the water source, the backwash tail water and the treatment tail water of the water treatment equipment are collected to the nearby wetland, and are reused as landscape, fire-fighting, and road dust water, so as to improve the surrounding ecological environment and save water obviously. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The overall schematic diagram of the system for removing nitrate in water in the water period of the application is shown;

[0044] Figure 2 The schematic diagram of the contact mixed type ion exchange processing module of the application is shown;

[0045] Figure 3 The schematic diagram of the resin regeneration module of the application is shown;

[0046] Figure 4 A schematic diagram of the water jet of the present application is shown;

[0047] Figure 5 A schematic diagram of the wet period treatment unit of the present application is shown;

[0048] Figure 6 A schematic diagram of the test curve of the influence of the contact-mixed ion exchange resin dosage on the nitrate removal effect of the present application is shown.

[0049] Figure legend: 1-control unit, 2-raw water process unit, 21-nitrate concentration detection device, 3-wet period treatment unit, 31-ion exchange treatment module, 311-treatment tank, 3111-first raw water inlet, 3112-process water outlet, 3113-resin inlet, 3114-desalinated water outlet, 3115-resin outlet, 312-stirrer, 313-stirrer motor, 314-constant temperature oscillator, 32-resin regeneration module, 321-resin collection part, 322-resin regeneration part, 3221-regeneration reaction tank, 32211-first process water inlet, 3222-regenerant stock solution storage tank, 3223-regenerant preparation and supply tank, 32231-second process water inlet, 32232-regenerant outlet, 3224-regenerant recovery tank, 3225-water jet, 32251-desalinated water inlet, 32252-regenerant inlet, 32253-mixed liquid outlet, 32254-desalinated water discharge pipeline, 323-resin supply part, 4-dry period treatment unit, 41-resin tank, 411-third raw water inlet, 42-reverse osmosis treatment device, 421-second outlet, 422-RO membrane, 5-physical separation unit, 6-water production process unit, 7-backwashing unit, 8-pre-treatment unit, 81-filtration tank, 82-desorption tank. DETAILED DESCRIPTION

[0050] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. The principles and characteristics of the present application described below in conjunction with the accompanying drawings need to be explained that the embodiments and the features in the embodiments in the present application can be combined with each other without conflict. The embodiments are only used to explain the present application, and are not used to limit the scope of the present application.

[0051] Glossary:

[0052] Raw water: refers to the natural water source collected in nature, including groundwater, mountain spring water, reservoir water and other natural water sources in nature, which has not been purified by any artificial purification treatment and is ready for nitrate removal treatment.

[0053] The water period: refers to the river flow mainly depends on rainfall or snowmelt replenishment period, generally in the rainy season or the period of continuous rising temperature in spring; the water period in the original water nitrate index usually changes in a larger range, usually 30mg / L~90mg / L, for example, the nitrate concentration in the original water is 30mg / L~120mg / L, 50mg / L~100mg / L, 60mg / L~130mg / L, etc., the fluctuation range of the upper limit and the lower limit is wide, and the nitrate concentration is high, the nitrate concentration in the original water is 45mg / L~150mg / L.

[0054] The dry period: refers to the surface water in the basin is exhausted, mainly depends on the period of groundwater recharge water source. In a year, the duration of the dry period is long or short, which varies with the natural geographical and meteorological conditions; the nitrate index in the original water in the dry period usually changes in a small range, usually less than 30mg / L, for example, the nitrate concentration in the original water is 30mg / L~55mg / L, 35mg / L~40mg / L, 45mg / L~60mg / L, etc., the fluctuation range of the upper limit and the lower limit is narrow, and the nitrate concentration is low, the nitrate concentration in the original water is 30mg / L~60mg / L.

[0055] It should be noted that the above-mentioned nitrate index change range refers to the change of nitrate content in the original water, although the same or close nitrate concentration value in the original water may occur in the dry period and the water period, but the nitrate concentration changes differently in the two water periods. Generally, the nitrate content in the original water is different according to the distribution of water source, and the nitrate content in the original water for domestic water is different, generally 30mg / L-150mg / L, the nitrate index detected in the present application is not the instantaneous nitrate content, but the change of nitrate content in a certain period of time, for example, 1 day, 3 days, 7 days, 15 days, etc.

[0056] Because the nitrate index in the original water in some areas fluctuates greatly according to the water period, according to the water quality detection results in different periods in recent years, the nitrate index in the water period is 30mg / L-120mg / L, the nitrate index fluctuates greatly, the nitrate index in the dry period is 30mg / L-55mg / L, the nitrate index is relatively stable, but does not meet the 20mg / L limit value requirement of "Drinking Water Health Standards" (GB5749-2006), and there is no alternative qualified water source around.

[0057] Based on the existing experience, when the nitrate index fluctuates greatly in the wet season, ion exchange treatment needs to be treated multiple times, the cathode ion resin and electricity consumption are large, and the operation cost is high, while the reverse osmosis treatment process has stable effluent. Compared with ion exchange, when the nitrate index fluctuates greatly in the wet season, the operation electricity and consumable cost of reverse osmosis treatment are reduced by 15%. In the dry season, when the nitrate index is stable, the contact mixed ion exchange is adopted. The combination of the two treatment devices ensures that the effluent water quality is stable and qualified, and the operation cost is greatly reduced compared with the conventional treatment device and process.

[0058] Based on this, the first aspect of the present application provides a process for removing nitrate from water in different water periods, which comprises the following steps: S1, judging the water period of raw water: when the concentration of nitrate in raw water changes in the range of 30 mg / L to 90 mg / L, the raw water is in the wet season, and when the concentration of nitrate in raw water changes less than 30 mg / L, the raw water is in the dry season. Specifically, the change index of the concentration of nitrate in raw water is detected by a nitrate concentration detection device 21, and whether the raw water is in the dry season or the wet season is determined by a control unit 1. The process can be judged by the control unit, and the control unit can control the following processes and adjust each process.

[0059] Step S2, pretreatment of raw water, which comprises: step S2-1, filtering treatment of raw water to remove impurities such as silt and colloid in raw water, which can be carried out by physical filtration method, such as using zeolite, filter and other devices to filter raw water, thereby removing insoluble impurities in water; step S2-2, removing colored pollutants and COD in raw water, which can be carried out by adsorption method to remove pollutants with certain solubility in raw water, thereby reducing the influence of these pollutants on ion exchange resin and RO membrane and other materials in the subsequent treatment process, and further purifying raw water.

[0060] Step S3, nitrate removal treatment of raw water: S31, when the raw water is in the dry season, the dry season treatment process is adopted for the nitrate removal treatment of raw water, S31', when the raw water is in the wet season, the wet season treatment process is adopted for the nitrate removal treatment of raw water. According to the judgment of the control unit 1, different processes are selected for raw water treatment.

[0061] Step S4, the raw water treated by the nitrate removal treatment in the above step S3 is transported to a physical separation unit 5 for impurity filtering treatment. The nitrate in the raw water treated by the dry season treatment or the wet season treatment is removed, and then physical impurity removal is carried out, which can filter the ion exchange resin particles entrained in the process water by sand, activated carbon, zeolite and other substances to avoid the presence of ion exchange resin particles in the process water.

[0062] Step S5, the raw water after the filtering of the impurities in step S4 is used as process water, and the process water is stored. The process water after storage meets the use standard of nitrate and other pollutants, and can be stored for subsequent use or directly supplied to the user's home.

[0063] The dry season treatment process and the wet season treatment process will be described in detail below. In some embodiments of the present application, the dry season treatment process in step S31 includes the following steps: S31-1, contact-mixing ion exchange treatment of raw water: unlike the fixed bed process of the prior art, in which ion exchange resin is fixed in the treatment device and the raw water can only be treated once after flowing through the fixed bed, the present application uses a contact-mixing ion exchange process, and a stirring device is provided in the device for the dry season treatment process. During the treatment process, when the raw water is treated by the dry season treatment process, the stirring is started to make the raw water fully and repeatedly contact with the ion exchange resin, which can completely remove the nitrate in the raw water and greatly improve the removal rate of nitrate in the raw water. S31-2, transporting the saturated ion exchange resin in step S31-1 to regenerate the ion exchange resin: when the nitrate on the surface of the ion exchange resin in step S31-1 reaches a certain degree after mixing with the raw water, the ion exchange resin is saturated, at which time the ability of the ion exchange resin to remove nitrate is greatly reduced or even lost. Directly discarding the ion exchange resin will not only pollute the environment but also cause a large amount of waste and increase the cost. Therefore, the present application uses a regeneration process of ion exchange resin to regenerate the saturated ion exchange resin, so as to remove the nitrate thereon and replenish chlorine ions on the surface of the ion exchange resin. In this way, the ion exchange resin after the regeneration treatment can be reused.

[0064] In some embodiments of the present application, the regeneration treatment includes a preparation of a regenerant process, a regeneration reaction process of the resin, and a supply process of the regenerated resin. The regenerant provided by the present application is actually a saturated sodium chloride solution. When the saturated ion exchange resin used in step S31-1 contacts with the saturated sodium chloride solution, the chlorine ions and the nitrate ions are exchanged again, so as to displace the nitrate ions on the surface of the ion exchange resin, thereby achieving the effect of regeneration. The preparation process of the saturated sodium chloride can use the traditional configuration method, for example, deionized water as a solvent and table salt as a solute for configuration. After the regeneration of the ion exchange resin meets the requirements for reuse, the ion exchange resin can be transported to continue the treatment of the raw water. Thus, step S31-3, transporting the regenerated ion exchange resin in step S31-2 to perform contact-mixing ion exchange treatment of the raw water.

[0065] The steps S31-1, S31-2 and S31-3 are performed synchronously and form a cycle, that is, in the actual processing, after the low water period processing process is started, the raw water is subjected to the contact-mixing ion exchange treatment, after a certain processing time, the ion exchange resin gradually approaches saturation, at this time, the ion exchange resin is output for regeneration. In this case, the entire contact-mixing ion exchange treatment process does not need to be stopped to transport the ion exchange resin, and the ion exchange resin can be transported alone by using a water jet, a particle transport pump or the like. In the initial stage, the amount of ion exchange resin required for the reaction process can be met by supplementing new ion exchange resin from the outside, and after the operation is stable, the regenerated ion exchange resin can be gradually supplemented to the contact-mixing ion exchange treatment stage, thereby forming a cycle for the entire low water period processing process. The raw water can be continuously treated without the need to stop the treatment process of the raw water to regenerate the ion exchange resin as in the fixed bed. Thus, the low water period processing process provided by the present application greatly saves the treatment cost of the raw water, improves the treatment efficiency, and increases the nitrate removal rate of the raw water, achieving three goals at once.

[0066] In addition, after the low water period processing process described above is performed for a certain time, the ion exchange resin with low regeneration effect can be discharged and uniformly treated, and new ion exchange resin is supplemented.

[0067] The above describes the low water period processing process when the raw water is in the low water period stage, and the following will describe the processing process when it is detected that the raw water is in the high water period. As described above, the nitrate concentration of the raw water in the high water period changes in a wide range and the nitrate content is high, so the contact-mixing ion exchange process alone can not completely remove the nitrate in the raw water, and thus the present application provides a high water period processing process.

[0068] In some embodiments of the present application, the high water period processing process in step S31' described above includes: step S31'-1, preliminary removal of nitrate in the raw water. Since the nitrate concentration of the raw water in the high water period changes in a wide range and the nitrate concentration is high, only one way of removing nitrate can lead to incomplete removal of nitrate in the raw water, so the nitrate in the raw water is first preliminarily removed, and the raw water from which part of the nitrate is removed enters the next step; S31'-2, reverse osmosis treatment of the raw water after the above step. Since the nitrate concentration of the raw water in the high water period changes greatly and the nitrate content is high, a large amount of ion exchange resin is required for direct treatment in the same way as in the low water period, and the cost is extremely high, so the present application uses a treatment method combining ion exchange resin and reverse osmosis for the raw water in the high water period, which not only reduces the processing cost but also improves the economic benefit, and the treated process water can meet the drinking water standard.

[0069] Thus, the process for removing nitrate in water in the water period provided by the present application is combined with the contact mixed ion exchange and reverse osmosis to remove nitrate in groundwater, and the real-time index of the nitrate concentration detection device is automatically switched by the control unit to change the processing mode. When the nitrate concentration changes in the range of 30 mg / L to 90 mg / L in the wet season, the nitrate concentration is usually above 40 mg / L, and the reverse osmosis treatment process is used to avoid multiple treatment of ion exchange treatment process, reduce the consumption of cathode ion resin and electricity, reduce the operation cost, and improve the stability of the process effluent. When the nitrate index changes in the range of less than 30 mg / L in the dry season, the nitrate concentration is usually in the range of 30 mg / L to 60 mg / L, and the contact mixed ion exchange process is used when the change is relatively stable, and compared with the traditional ion exchange process, the treatment efficiency is improved by 30%.

[0070] In some embodiments of the present application, the process for removing nitrate in water in the water period further comprises a backwashing process, which is to use the treated process water to backwash the device for physical separation and impurity removal, so as to avoid the ion exchange resin particles carried in the process water from blocking the device.

[0071] Thus, the process for removing nitrate in water in the water period provided by the present application is combined with the contact mixed ion exchange and reverse osmosis to remove nitrate in groundwater, and the real-time index of the nitrate concentration detection device is automatically switched by the control unit to change the processing mode. When the nitrate concentration changes in the range of 30 mg / L to 90 mg / L in the wet season, the nitrate concentration is usually above 40 mg / L, and the reverse osmosis treatment process is used to avoid multiple treatment of ion exchange treatment process, reduce the consumption of cathode ion resin and electricity, reduce the operation cost, and improve the stability of the process effluent. When the nitrate index changes in the range of less than 30 mg / L in the dry season, the nitrate concentration is usually in the range of 30 mg / L to 60 mg / L, and the contact mixed ion exchange process is used when the change is relatively stable, and compared with the traditional ion exchange process, the treatment efficiency is improved by 30%.

[0072] According to the second aspect of the present application, a system for removing nitrate in water in the water period is provided. As described above, the water period includes the wet season and the dry season, the nitrate concentration of the raw water in the wet season changes in the range of 30 mg / L to 60 mg / L, and the nitrate concentration of the raw water in the dry season changes in the range of less than 30 mg / L. The different water periods can be determined by measuring the change range of the nitrate concentration, and different devices are selected to remove the nitrate according to the characteristics of the raw water in different water periods, which greatly saves the cost and processing time.

[0073] Specifically, as shown in Figure 1 , the system for removing nitrate in water in the water period comprises a raw water inlet, a raw water outlet, a first device, a second device, a first nitrate concentration detection device, a second nitrate concentration detection device, a control unit, and a water outlet. Figure 1The middle dotted line represents an electrical connection, and the thick solid line represents a pipeline connection, and the pipeline is provided with a solenoid valve. The system provided by the application comprises a control unit 1 and a raw water process unit 2, a pretreatment unit 9, a dry season treatment unit 3, a wet season treatment unit 4, a physical separation unit 5 and a product water process unit 6 which are electrically connected to the control unit 1; the wet season treatment unit 4 and the dry season treatment unit 3 are arranged in parallel downstream of the raw water process unit 2, the physical separation unit 5 is located downstream of the wet season treatment unit 4 and the dry season treatment unit 3, the product water process unit 6 is located downstream of the physical separation unit 5, and the raw water process unit 2 is provided with a nitrate concentration detection device 21; the dry season treatment unit 3 comprises a contact-mixed ion exchange treatment module 31 and a resin regeneration module 32.

[0074] The system provided by the application combines a contact-mixed ion exchange device and a reverse osmosis device in parallel, thereby eliminating the complex process in the prior art which needs to be used in series and repeatedly backflowed to meet the discharge standard. The nitrate concentration detection device 21 in the raw water process unit 2 detects the nitrate concentration in raw water, when the detected nitrate concentration in raw water ranges from 30 mg / L to 60 mg / L, the control unit 1 determines that the water season of raw water is a wet season; and when the detected nitrate concentration in raw water is less than 30 mg / L, the control unit 1 determines that the water season of raw water is a dry season.

[0075] After the determination, the raw water process unit pumps raw water to the pretreatment unit for pretreatment. In some embodiments of the application, the pretreatment unit 8 comprises a filter tank 81 and a desorption tank 82, the filter tank 81 can be provided with devices such as filter membranes and quartz sand filters, which are used to remove impurities such as silt and colloids in water to avoid the influence of solid particles on other treatment units in the subsequent process. The desorption tank 82 can be provided with devices such as flocculants and gratings, thereby removing impurities such as COD and colored pollutants in water, thereby avoiding the influence on ion exchange resins or RO membranes, and further improving water quality.

[0076] Subsequently, the raw water is pumped to the wet season treatment unit 4 for treatment according to the determined dry season and wet season, at this time the dry season treatment unit 3 is in a closed state; or the raw water is pumped to the dry season treatment unit 3 for treatment, at this time the wet season treatment unit 4 is in a closed state. Thus, the effect of treating raw water in different seasons is achieved.

[0077] The raw water treated by the dry season treatment unit 3 or the wet season treatment unit 4 is transported to a downstream physical separation unit 5, and solid particle impurities in the raw water are removed by the physical separation unit 5. After the raw water treated by the physical separation unit 5 reaches the use (discharge) standard, the water reaching the standard is transported to a water production process unit 6, which is provided with a water storage clean water tank or other water storage device, and the water reaching the standard is stored in the water production process unit 6, and then is distributed to users as needed by a water supply pump or is applied to other units in the system.

[0078] Further, as shown in Figure 2 The dry season treatment unit 3 of the present application includes a contact-mixing ion exchange treatment module 31 and a resin regeneration module 32. The contact-mixing ion exchange treatment module 31 provided by the present application enables the raw water to be fully contacted with ion exchange resin particles under low-speed stirring in a treatment tank 311, so that nitrate in the water can be fully removed, and the treatment rate of nitrate reaches more than 90%.

[0079] The system provided by the present application integrates a contact-mixing ion exchange water treatment system, a resin regeneration system, a water supply system, and a reverse osmosis treatment system, and forms a "smart water platform" by being regulated by the control unit 1, so that full-automatic control, treatment, regeneration, fault analysis, and operation and maintenance records of the water treatment equipment are realized, and the human resource cost of later operation and maintenance is greatly saved.

[0080] The structure and working principle of each unit will be described in detail below.

[0081] In some embodiments of the present application, the control unit 1 can be arranged in the system or at a place outside the system for the convenience of operation by an operator, and is provided with an input module, an output module, a data analysis module, a touch module, a display module, etc. (not shown in the figure). The control unit 1 is electrically connected with other units, so that data information from each unit can be received by the input module, and after being analyzed by the data analysis module, instructions are provided to each unit by the output, in addition, the operator can set parameters of each unit of the system and start or stop the operation of each unit through the touch module and the display module.

[0082] Furthermore, the raw water process unit 2 is equipped with a nitrate concentration detection device 21, an outlet pipe 23, and a raw water pump 22. Additionally, the raw water process unit 2 can also be equipped with a raw water storage device, or the source of a deep well or spring water can be directly used as the raw water storage device, connected directly to the subsequent treatment unit via the outlet pipe 23. When the raw water process unit 2 is equipped with a raw water storage device, the nitrate concentration detection device 21 is installed within the raw water storage device. When the raw water process unit 2 is not equipped with a raw water storage device, the nitrate concentration detection device 21 can be directly installed at the raw water source, such as underwater in a deep well or at the outlet of a spring water source, using a float or similar device. Thus, the nitrate concentration detection device 21 can monitor the nitrate concentration in the raw water in real time and transmit the data to the control unit 1 for data analysis. The raw water pump 22 can be installed inside the outlet pipe 23 of the raw water process unit 2, pumping the raw water into the system of this invention.

[0083] The nitrate concentration detection device 21 transmits the detected nitrate concentration in the raw water to the control unit 1. When the control unit 1 receives a nitrate concentration change range of less than 30 mg / L, it determines that the raw water is in the dry season and controls the raw water process unit 2 to transport the raw water to the dry season treatment unit 3. When the control unit 1 receives a nitrate concentration change range of 30 mg / L to 60 mg / L, it determines that the raw water is in the wet season and controls the raw water process unit 2 to transport the raw water to the wet season treatment unit 4.

[0084] like Figure 2 As shown, the contact mixing ion exchange treatment module 31 in the dry season treatment unit 3 includes a treatment tank 311, a stirrer 312 installed inside the treatment tank, and a stirrer motor 313 connected to the upper end of the stirrer 312. The treatment tank 311 is provided with a first raw water inlet 3111, a process water outlet 3112, a resin inlet 3113, a resin outlet 3115, and a demineralized water outlet 3114.

[0085] When the contact-mixing ion exchange treatment module is started, raw water enters the treatment tank 311 through the first raw water inlet 3111. The capacity of the treatment tank 311 can be determined according to the use, for example, according to the user's high water demand, and the treatment tank can generally be made of 304 stainless steel, with a pressure of not less than 2.0 MPa. The treatment tank 311 is provided with ion exchange resin. Unlike the current ordinary ion exchange method, the dry season treatment unit of the present application adopts a contact-mixing ion exchange treatment module. The ion exchange resin is in a free moving state in the treatment tank. When the raw water enters the treatment tank, it can fully contact the ion exchange resin under the action of stirring. The chlorine ions on the surface and pore size of the ion exchange resin can be fully replaced by nitrate ions, so as to remove the nitrate in the water. Thus, the exchange reaction is completely carried out, and the water quality is greatly improved.

[0086] Further, the amount of ion exchange resin is determined according to the water consumption. Generally, the amount of ion exchange resin is 0.5 g / L to 5 g / L, preferably 2.5 g / L. The ion exchange resin used in the present application can be Pruolite A 520E ion exchange resin (Pruolite) or Purolite A 300E ion exchange resin (Pruolite), preferably Pruolite A 520E ion exchange resin (Pruolite).

[0087] On this basis, the present application removes ions in raw water by fully contacting raw water with ion exchange resin. After the stirring motor 313 on the treatment tank 311 is started, the stirrer 312 is driven to rotate at a low speed. The low-speed rotation speed is 15 to 30 rpm. Low-speed stirring can make the raw water and ion exchange resin fully mixed and contacted, so as to achieve the purpose of ion exchange. In addition, the control unit 1 can control the rotation speed of the motor 313 of the stirrer, so as to control the degree of contact mixing, and maximize the contact area between the ion exchange resin and the raw water, so as to fully carry out the ion exchange reaction. Therefore, compared with the fixed bed in the prior art, the contact-mixing ion exchange module provided by the present application can greatly improve the removal rate of nitrate and greatly improve the removal efficiency.

[0088] In the contact-mixing ion exchange process described above, the ion exchange resin will reach saturation after being used for a period of time, in order to achieve the highest economic benefits, the ion exchange resin will be sent to the resin regeneration module for ion exchange resin regeneration, the regenerated ion exchange resin can also be discharged into the treatment tank 311 to continue the contact ion exchange reaction. It should be noted that the ion exchange resin has a fixed saturation period, which can be preset in the control unit. When the preset period is reached, the saturated ion exchange resin is discharged into the resin regeneration module for resin regeneration.

[0089] Based on this, as shown in Figure 3 The resin regeneration module 32 includes a resin collection part 321, a resin regeneration part 322 and a resin supply part 323 connected in series by pipes. The resin collection part 321 communicates with the resin outlet 3115, and the resin supply part 323 communicates with the resin inlet 3113. When the ion exchange resin in the treatment tank 311 of the contact-mixing ion exchange treatment module 31 is saturated, the control unit 1 controls the saturated ion exchange resin to be discharged into the resin collection part 321 through the resin outlet 3115, as shown in Figure 2 The resin outlet 3115 is preferably arranged at the bottom or lower part of the treatment tank 311. After the resin is saturated, the stirring operation is stopped, and the resin will settle at the bottom of the treatment tank 311, so that the resin can be discharged. The resin outlet 3115 is connected to the resin collection part 321 by a pipe, and a jet device (not shown) can be installed on the pipe. The resin can be discharged into the resin collection part 321 through the jet device. The discharged resin can be temporarily stored in the resin collection part 321. Then the saturated resin in the resin collection part 321 is transported to the resin regeneration part 322 for regeneration treatment.

[0090] In some embodiments, as shown in Figure 3 The resin regeneration part 322 includes a regenerant supply device and a regeneration reaction tank 3221. The regeneration reaction tank 3221 is provided with a first process water inlet 32211, which communicates with the water production process unit 6 through a pipe. Further, the regenerant supply device includes a regenerant stock solution storage tank 3222, a regenerant preparation and supply tank 3223, a regenerant recovery tank 3224 and a water jet device 3225.

[0091] As shown in Figure 4As shown, the water jet 3225 is provided with a desalinated water inlet 32251, a regenerant inlet 32252 and a mixed liquid outlet 32253. The desalinated water inlet 32251 is connected to the treatment tank 311 through a desalinated water discharge pipeline 32254. It should be noted that the desalinated water refers to product water obtained by removing impurities such as suspended solids, colloids and inorganic cations and anions in water through various water treatment processes. In this application, the desalinated water refers to water that has been treated by ion exchange resin in the treatment tank but has not been discharged into the product water process unit 6. The desalinated water can be directly used for resin regeneration, thereby accelerating the treatment rate.

[0092] When the water jet 3225 is constricted, the static pressure can be converted into kinetic energy. When the desalinated water passes through the water jet 3225 at a high speed, a low pressure area is generated at the constricted end, and the regenerant in the regenerant stock solution tank 3222 can be sucked into the water jet 3225. After mixing with the desalinated water, a regenerant solution with a certain concentration is formed and is delivered to the regenerant preparation and supply tank 3223. The regenerant preparation and supply tank 3223 is provided with a mixed liquid inlet 32233 connected to the mixed liquid outlet 32253 through a pipeline, a second process water inlet 32231 connected to the product water process unit 6 through a pipeline and a regenerant outlet 32232 connected to the regeneration reaction tank 3221 through a pipeline. The mixed liquid enters the regenerant preparation and supply tank 3223 through the mixed liquid inlet 32233. The regenerant preparation and supply tank 3223 is preferably also provided with a regenerant concentration detection device (not shown). If the concentration of the regenerant detected by the regenerant concentration detection device is high, the regenerant is discharged into the process water through the second process water inlet 32231, so as to configure the regenerant to an appropriate concentration. Subsequently, the regenerant is discharged into the regeneration reaction tank 3221 through the regenerant outlet 32232.

[0093] In some embodiments of the present application, the regenerant stock solution can be a saturated sodium chloride solution. The saturated ion exchange resin discharged from the resin collection part 321 enters the regeneration reaction tank 3221 for regeneration treatment. The efficiency of the regenerated resin can reach 80%. The regenerated ion exchange resin is discharged into the resin supply part 323 through a pipeline for storage. Subsequently, after the saturated ion exchange resin in the treatment tank 311 is discharged again, the regenerated ion exchange resin in the resin supply part 323 is supplied to the treatment tank 311. In this way, the saturated ion exchange resin in the treatment tank 311 can be reused, thereby greatly reducing the cost of ion exchange resin.

[0094] The concentration of the regenerant after reaction in the regeneration reaction tank 3221 changes, and a large amount of nitrate and other ions are contained therein. Therefore, the regenerant needs to be recovered. The used regenerant is discharged into the regenerant recovery tank 3224 through a pipeline for unified treatment after recovery.

[0095] In some embodiments, the resin supply part 323 is further provided with a new resin opening (not shown) for supplementing unused new ion exchange resin into the resin supply part 323 for subsequent ion exchange treatment process.

[0096] In some embodiments, the dry season treatment unit 3 of the present application further comprises a constant temperature oscillator 314 arranged upstream of the contact-mixing ion exchange treatment module 31. The constant temperature oscillator 314 is used to oscillate the raw water for 24 hours before the raw water enters the contact-mixing ion exchange treatment module 31, so as to completely reduce the nitrite in the water body. After the nitrite is completely reduced to nitrate, the raw water is treated by the contact-mixing ion exchange treatment module 31 to remove the nitrate.

[0097] In some embodiments of the present application, the treatment tank 311 of the present application is provided with at least two groups of ion exchange treatment modules arranged in parallel to simultaneously treat the raw water to remove the nitrate, thereby greatly improving the treatment efficiency. In addition, the contact-mixing ion exchange device of the present application can improve the treatment efficiency by 30% compared with the conventional ion exchange device, and the water quality of the effluent is stable. The change of the water quality or components of the influent, the running flow rate and the like have little effect on the water quality of the effluent of the mixed bed, and the later operation is simple.

[0098] The above dry season treatment unit of the present application can continuously treat the raw water, remove the nitrate, regenerate the saturated ion exchange resin, and discharge the ion exchange resin in the treatment tank to the regeneration unit. The regenerated ion exchange resin can be timely supplemented to the treatment tank, and the ion exchange resin does not need to be removed for regeneration while the treatment of the raw water is stopped. The whole treatment process does not need to be carried out in stages, but only needs to be continuously operated. The treatment efficiency is improved, and the treatment cost is reduced.

[0099] Therefore, the raw water in the dry season is treated to remove the nitrate, and when the raw water is in the wet season, the nitrate index fluctuates greatly. The wet season treatment unit 4 is used to remove the nitrate in the raw water.

[0100] In some embodiments, as shown in Figure 5 The wet season treatment unit 4 comprises a resin tank 41 and a reverse osmosis treatment device 42 arranged downstream of the resin tank 41. The resin tank 41 is provided with a third raw water inlet 411, the reverse osmosis treatment device 42 is provided with a second effluent outlet 421, and the reverse osmosis treatment device 42 is provided with an RO membrane 422. When the control unit 1 determines that the raw water is in the wet season, the raw water is pumped to the third raw water inlet 411 through the raw water outlet. The raw water is first treated to remove part of the nitrate by the resin tank 41, and then treated by the RO membrane 422 to completely remove the nitrate in the water.

[0101] In some embodiments, the resin tank 41 can be filled with ion exchange resin. The raw water can react with the ion exchange resin to remove part of the nitrate in the water. The resin tank 41 can be different from the above-mentioned contact-mixed ion exchange treatment module, which uses ordinary ion exchange instead of contact-mixed ion exchange. The resin tank 41 can also be the same as the contact-mixed ion exchange resin described above, which contains not only a treatment tank but also an ion exchange resin regeneration module, thereby increasing the efficiency of nitrate removal and improving the utilization rate of ion exchange resin. In the preferred embodiment of the present application, the ion exchange resin in the resin tank 41 is the same as the contact-mixed ion exchange resin in the dry season treatment unit.

[0102] Because the nitrate concentration in the raw water during the wet season fluctuates greatly and is relatively high, if the dry season treatment unit is still used to remove nitrate, a large amount of ion exchange resin is needed to completely remove the nitrate in the raw water during the wet season, which is a waste. Therefore, the present application converts the treatment of raw water during the wet season to the removal of nitrate by the wet season treatment unit. From the perspective of removing nitrate, a small amount of ion exchange resin in the resin tank 41 is used to remove part of the nitrate in the water, and then the raw water is transported to the RO membrane 422 to start removing the nitrate in the raw water. The concentrated water after removal is collected and treated.

[0103] The nitrate concentration in the raw water during the wet season varies widely and the nitrate content is usually high, so the combination of ion exchange and reverse osmosis can improve the efficiency of nitrate removal. During the dry season, the nitrate concentration in the raw water varies within a small range and the nitrate content in the raw water is relatively low, so the combination of ion exchange and reverse osmosis is not economical. Therefore, the present application provides a dry season treatment unit connected in parallel with the wet season treatment unit. To further improve the removal of nitrate, the dry season treatment unit of the present application uses a contact-mixed ion exchange module to increase the removal rate of nitrate.

[0104] Next, the raw water treated by the dry season treatment unit 3 or the wet season treatment unit 4 is transported to the physical separation unit 5. During the treatment process in the above two units, the treated water flowing out may be entrained with ion exchange resin and other solid impurities involved in the reaction, so the remaining solid impurities in the water are further separated in the physical separation unit 5. The physical separation unit 5 can be a quartz sand filter, a zeolite filter, an activated carbon filter, and other physical separation and / or adsorption type filters, which can improve water quality and remove impurities in the water.

[0105] The nitrate content in the treated clean water via the physical separation unit 5 reaches the use standard, so that the clean water is discharged to the water production process unit 6, which is also connected to the regeneration reaction tank 3221 and the regeneration agent preparation supply tank 3223, and the treated water can be used for regeneration agent preparation and resin regeneration. In addition, in some embodiments, a backwashing unit 7 is arranged between the physical separation unit 5 and the water production process unit 6, which applies a certain pressure to the process water in the water production process unit 6, so as to discharge the process water to the physical separation unit 5 for backwashing, thereby improving the use efficiency of the physical separation unit 5.

[0106] In some embodiments, a disinfection device is also arranged in the water production process unit 6, which contains sodium hypochlorite. When the water production process unit 6 needs to supply water to users, the disinfection device disinfects the process water in the water production process unit 6, and then supplies it to a variable frequency water supply pump (not shown in the figure), and then pumps it to the user's home.

[0107] In addition, it should be noted that the system for removing nitrate from water in the dry season provided by the present application is provided with an electromagnetic valve on each pipe, and the electromagnetic valves are electrically connected to the control unit, so as to control the flow of each pipe, and further control the flow of raw water and process water.

[0108] The system for removing nitate from water in the dry season provided by the present application is combined with the reverse osmosis treatment process on the basis of the contact-mixed ion exchange process, and based on the "dynamic monitoring and data analysis" technology, two combined process modes are constructed, and the control unit 1 can automatically switch to the suitable treatment process according to the nitrate index of raw water and the saturation and regeneration period of ion exchange resin. The system of the present application integrates the ion exchange treatment system, the resin regeneration system, the reverse osmosis system, the physical separation system and the water supply system, and is a "only water platform", which realizes the functions of full-automatic control, treatment, regeneration, fault analysis and operation and maintenance record of the water treatment equipment.

[0109] Test Example 1

[0110] In order to determine the optimal dosage of ion exchange resin in the treatment tank 311 in the contact-mixed ion exchange treatment module 31 in the dry season treatment unit 3, when the nitrate index of groundwater quality (nitrate concentration change range) is 45 mg / L, after oscillation for 24 h by the constant temperature oscillator 314, the denitrification test is carried out, and the above two kinds of resins are tested respectively, and the test results are shown in Table 1. Figure 6

[0111] ​The results show that the concentration of nitrate in groundwater decreases with the increase of resin dosage. For groundwater with NO3-N (nitrate nitrogen) concentration of 45 mg / L, when the resin dosage of Purolite A 300E and Purolite A 520E is 2.5 g / L, the concentration of NO3-N (nitrate nitrogen) can be reduced to below 10 mg / L. Therefore, in order to achieve the most economic effect, the dosage of ion exchange resin can be set at 2.5-5 g / L, preferably 2.5 g / L.

[0112] Test Example 2

[0113] Next, by selecting the drinking water source of Zhaigezhuang Village, Wangxinzhuang Town, Pinggu District, Beijing as the test raw water, the efficiency of the process provided by the application for removing nitrate from raw water is tested. According to the water quality test results in different periods in recent years, the nitrate concentration of the drinking water source of Zhaigezhuang Village is 30 mg / L-120 mg / L in the wet season, the nitrate index fluctuates greatly to 90 mg / L, the nitrate index is 30 mg / L-55 mg / L in the dry season, the nitrate index fluctuates less to 15 mg / L, and the difference is relatively large. The process of the application is used to remove nitrate from the above water source.

[0114] The process indexes are set as shown in the following table:

[0115]

[0116] From the above results, it can be seen that the mixed tail water after the process of removing nitrate from groundwater by combining contact mixing ion exchange with reverse osmosis reaches the direct discharge standard after detection, and can be used as landscape and greening water.

[0117] In the description of the application, it should be understood that the orientations or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and the direction of the end plate fixing the outlet pipe is defined as the front direction unless otherwise specified, and the front and back can also be interchanged in the case of special specification; this is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0118] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connecting", "fixed", "fixedly connected", "connection", "fixedly connected", "connected", "fixed", and the like should be construed broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, can be internal communication of two elements or interaction relationship between two elements, unless specifically defined otherwise. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0119] In the present application, unless specifically defined otherwise, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0120] It should be understood that although the terms "first", "second", etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, the first element discussed below can be called a second element without departing from the teachings of the present application. Similarly, the second element can also be called a first element.

[0121] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples, without contradiction.

Claims

1. A process for the removal of nitrate from water during the draw period, characterized in that, The process comprises the following steps: Step S1, judging the water period of raw water: When the concentration of nitrate in raw water changes in the range of 30 mg / L~90 mg / L, the raw water is in the wet period, When the concentration of nitrate in raw water changes in the range of less than 30 mg / L, the raw water is in the dry period; Step S2, pretreatment of raw water; Step S3, nitrate removal treatment of raw water: Step S31, when the raw water is in the dry period, the dry period treatment process is used for nitrate removal treatment of raw water; Step S31', when the raw water is in the wet period, the wet period treatment process is used for nitrate removal treatment of raw water, Step S4, the raw water treated by the nitrate removal treatment in the above step S3 is physically separated and impurities are removed; Step S5, the raw water treated by the physical separation and impurity removal treatment in the above step S4 is used as process water, and the process water is stored; The dry period treatment process in step S31 comprises: Step S31-1, contact mixing ion exchange treatment of raw water; Step S31-2, delivery of saturated ion exchange resin in step S31-1 for ion exchange resin regeneration; Step S31-3, delivery of regenerated ion exchange resin in step S31-2 for contact mixing ion exchange treatment of raw water, wherein, The steps S31-1, S31-2 and S31-3 are performed synchronously and form a cycle; The wet period treatment process in step S31' comprises: Step S31'-1, preliminary removal of nitrate in raw water; Step S31'-2, reverse osmosis treatment of raw water after the above step.

2. The process for removal of nitrate from water at the water shed according to claim 1, wherein, The process for removing nitrate in water in the water period further comprises a backwashing process.

3. A system for implementing the process for removing nitrate from water during low-water periods according to claim 1 or 2, said water periods comprising low-water periods and high-water periods, the nitrate concentration of raw water varying by less than 30 mg / L during the low-water periods and by between 30 mg / L and 90 mg / L during the high-water periods, characterized in that, The system comprises a control unit and a raw water process unit, a pretreatment unit, a dry period treatment unit, a wet period treatment unit, a physical separation unit and a product water process unit electrically connected with the control unit; the dry period treatment unit and the wet period treatment unit are arranged in parallel downstream of the raw water process unit, the physical separation unit is located downstream of the wet period treatment unit and the dry period treatment unit, and the product water process unit is located downstream of the physical separation unit; wherein, The raw water process unit is provided with a nitrate concentration detection device; The dry period treatment unit comprises a contact mixing ion exchange treatment module and a resin regeneration module.

4. The system of claim 3, wherein, The contact mixing ion exchange treatment module comprises a treatment tank, a stirrer installed inside the treatment tank and a stirrer motor connected to the upper end of the stirrer, and a first raw water inlet, a process water outlet, a resin inlet, a resin outlet and a desalted water outlet are arranged on the treatment tank, wherein the contact mixing ion exchange treatment module is provided with at least two groups.

5. The system of claim 4, wherein, The resin regeneration module comprises a resin collection part, a resin regeneration part and a resin supply part connected in series by pipelines, the resin collection part is in communication with the resin outlet, the resin supply part is in communication with the resin inlet, and wherein, The resin regeneration unit comprises a regenerant supply device and a regeneration reaction tank, and the regeneration reaction tank is provided with a first process water inlet which is communicated with the water production process unit through a pipeline; The regenerant supply device comprises a regenerant stock solution storage tank, a regenerant preparation and supply tank, a regenerant recovery tank and a water jet, wherein the water jet is provided with a desalted water inlet, a regenerant inlet and a mixed liquid outlet, the desalted water inlet is connected with the desalted water outlet through a desalted water discharge pipeline, and the regenerant inlet is connected with the regenerant stock solution storage tank through a pipeline; the regenerant preparation and supply tank is provided with a mixed liquid inlet communicated with the mixed liquid outlet through a pipeline, a second process water inlet communicated with the water production process unit through a pipeline and a regenerant outlet communicated with the regeneration reaction tank through a pipeline; and the regenerant recovery tank is communicated with the regeneration reaction tank through a pipeline.

6. The system of claim 4, wherein, The dry season treatment unit further comprises a constant temperature oscillator, and the constant temperature oscillator is arranged upstream of the contact-mixing ion exchange treatment module.

7. The system of claim 5, wherein, The dry season treatment unit further comprises a constant temperature oscillator, and the constant temperature oscillator is arranged upstream of the contact-mixing ion exchange treatment module.

8. The system of claim 3, wherein, The wet season treatment unit comprises a resin tank and a reverse osmosis treatment device arranged downstream of the resin tank, the resin tank is provided with a third raw water inlet, the reverse osmosis treatment device is provided with a second water outlet, and the reverse osmosis treatment device is provided with an RO membrane.

9. The system of any one of claims 3-8, wherein, A backwashing unit is arranged between the physical separation unit and the water production process unit, and the pretreatment unit comprises a filter tank and a desorption tank.

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