A resource-based treatment system and method for high-salt, high-ammonia-nitrogen wastewater

Abstract

This invention discloses a resource-based treatment system and method for high-salt, high-ammonia-nitrogen wastewater, belonging to the field of wastewater treatment technology. The system consists of a single-chamber electrolytic cell, a filtration device, and a double-chamber electrolytic cell connected in sequence. The electrolytic cell is equipped with inclined Z-shaped baffles and vertically clamped electrode plates, causing the wastewater to flow in reverse, avoiding air resistance and short-circuiting of the water flow. The single-chamber electrolytic cell performs electrolytic pretreatment to break down colloids and emulsions, solving the problem of evaporation, scaling, and clogging at the source. The double-chamber electrolytic cell's anode chamber undergoes multi-stage series degradation of ammonia nitrogen and COD, while the cathode chamber produces high-pH alkaline water. After treatment, the wastewater can be evaporated and crystallized to obtain high-purity salt, achieving simultaneous recovery of salt and alkali. This invention achieves an ammonia nitrogen removal rate of over 98%, extends the evaporator operating cycle by 5 times, and is suitable for the treatment and resource recovery of high-salt wastewater in industries such as chemical, printing and dyeing, and pesticides.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and resource recovery technology, specifically relating to a high-salt wastewater treatment system and process method containing potassium, sodium, chlorine, high concentration of ammonia nitrogen, COD, colloids, and emulsions. In particular, it relates to an integrated resource recovery technology that utilizes electrolysis to generate active chlorine to oxidize and degrade pollutants, break down colloids at the source, and simultaneously recover high-purity salt crystals and high-pH alkaline water. Background Technology

[0002] High-salt, high-ammonia-nitrogen wastewater is widely generated in industries such as pesticides, pharmaceuticals, printing and dyeing, and fine chemicals. This wastewater typically contains high concentrations of potassium chloride and sodium chloride, as well as high concentrations of ammonia nitrogen and COD, along with large amounts of colloids and emulsions. Currently, commonly used treatment processes in the industry include stripping, reverse osmosis, conventional evaporation crystallization, and breakpoint chlorination. These processes generally suffer from high energy consumption, large reagent dosages, difficulty in resource recovery of salts, and excessive residual chloride ions.

[0003] Triple-effect evaporation is the mainstream treatment process for high-salinity wastewater, but colloids in the wastewater are the core cause of scaling and clogging in the evaporator. During evaporation, colloids form viscous substances that adhere to salt particles and attach to the walls of heat exchange tubes and the inner walls of the equipment, forming a stubborn scale layer. This not only reduces heat transfer efficiency and shortens the equipment's operating cycle but also leads to salt crystallization and adhesion, quality degradation, and difficulty in effectively separating potassium and sodium components. A typical industrial case study: A chemical plant in Shanxi Province was equipped with a triple-effect evaporator designed for an evaporation capacity of 150 tons / day. When treating its own high-salinity, high-ammonia-nitrogen wastewater, the evaporator frequently experienced blockage due to the inability to pre-disinfect the colloids. The actual evaporation capacity dropped to 80-100 tons / day, only 53%-67% of the designed capacity; the equipment's operating cycle was only 3 days, requiring frequent shutdowns for physical cleaning; a large amount of viscous colloid remained at the bottom of the evaporator, with potassium and sodium salts encapsulated and adhered, making component separation impossible. Existing passive maintenance methods such as physical cleaning and scale inhibitor addition cannot solve the problem of colloidal blockage at its root. Colloidal blockage has become the core bottleneck restricting the stable operation of triple-effect evaporators in industrial applications.

[0004] Electrochemical oxidation technology can generate active chlorine by electrolyzing native chloride ions in wastewater, which then oxidizes and decomposes ammonia nitrogen, making it suitable for wastewater treatment. However, traditional electrolytic cell flow channel designs have significant flaws, easily leading to water flow short circuits and gas accumulation and blockage, directly reducing current utilization efficiency and resulting in incomplete pollutant degradation. At the same time, existing electrolysis processes cannot achieve simultaneous resource recovery of salt and alkali, resulting in low comprehensive utilization rates of water and salt resources. Summary of the Invention

[0005] I. The technical problem to be solved by the invention

[0006] Traditional electrolyzers have unreasonable flow channels, resulting in problems such as water flow short circuits, gas accumulation and gas blockage during electrolysis, low electrolysis current efficiency, and poor degradation and removal effects of ammonia nitrogen and COD.

[0007] Colloidal and emulsified substances in wastewater cannot be removed at the source, leading to scaling and blockage of evaporation equipment, halved production capacity, impure salt crystals, and inability to separate potassium and sodium salts. Common pain points in the industry: colloidal blockage results in the actual production capacity of triple-effect evaporators being only 53% to 67% of the design value, and the equipment operation cycle being shortened to 3 days. Conventional methods cannot solve the problem.

[0008] Potassium and sodium salts in wastewater cannot be efficiently graded and recovered, resulting in low resource utilization rates, high solid waste disposal costs, and serious resource waste.

[0009] Traditional electrolysis systems lack a control mechanism to adapt to water quality fluctuations, have high overall power consumption, and lack energy-saving operating modes.

[0010] II. Technical Solution

[0011] (I) Structure of Resource Utilization Processing System This processing system consists of a single-chamber electrolytic cell, a filtration device, and a double-chamber electrolytic cell connected sequentially by pipelines (see [link]). Figure 1 ).

[0012] Both the single-chamber and double-chamber electrolytic cells are sealed pressure-bearing structures, with multiple layers of inclined Z-shaped baffles arranged inside (see...). Figure 2 (Left side); the baffle plate is bent in a Z-shape along the horizontal direction, and the whole is inclined upwards at 5° to 30° relative to the horizontal surface, preferably at 15° to 25°; the baffle plate divides the cavity inside the tank into multiple closed baffle water chambers that are connected vertically. The tank is vertically arranged with clamp-type electrode plates, which are parallel to the straight section of the baffle plate, and the electrode plates are fixed at a distance of 20mm; the electrode plates adopt a back-connected conductive structure, and the positive and negative electrode plates form an independent closed water-passing jacket. The wastewater flows back and forth along the baffle channel of the electrode jacket from bottom to top. The electrolysis gas is carried and dissolved by the flowing water throughout the process, and there is no local gas accumulation, no waste gas overflow, and no water flow short circuit in the tank.

[0013] The dual-chamber electrolyzer is divided into independent anode and cathode chambers by a cation exchange membrane; both the anode and cathode chambers are equipped with the aforementioned inclined Z-shaped baffles and vertical clamping plates (see...). Figure 2 (Right side); The anode chamber is assembled from multiple electrolysis modules connected in series. The anode chamber inlet is connected to the filtrate outlet of the front-end filtration equipment and is equipped with an online active chlorine monitoring device; the cathode chamber is separately equipped with a clean water inlet and an alkaline water finished product outlet.

[0014] Both single-chamber and double-chamber electrolytic cells adopt a standardized modular design. A single set of equipment can be assembled in parallel from 2 to 6 sets of standardized modular units. The modules are connected by quick-release pipelines, which is suitable for water volume expansion and segmented operation and maintenance.

[0015] (II) Resource-based treatment methods for high-salinity and high-ammonia-nitrogen wastewater The above system is used to treat high-salt wastewater containing potassium ions, sodium ions, chloride ions, ammonia nitrogen, COD, colloids, and emulsions. The specific process steps are as follows: (a) Electrolytic pretreatment to break down the gel: The raw wastewater is fed into a closed single-chamber electrolytic cell for electrolytic pretreatment. Relying on the dual effects of electrolytic oxidation and electric field dissociation, the emulsion and colloidal macromolecular structure of the water body are broken down from the source, eliminating the negative effects of colloidal adhesion of salt particles, blockage of heat exchange surfaces, and obstruction of potassium and sodium separation; the electrolytic gas is carried away and dissolved by the water body, preventing gas accumulation and failure in the cell.

[0016] (b) Solid-liquid separation: The effluent from the single-chamber electrolytic cell is sent to the filtration equipment to retain the large molecular colloidal residue after pyrolysis, and a clean filtrate is obtained.

[0017] (c) Staged electrolytic degradation of pollutants: The filtrate is fed into a multi-stage series electrolysis module in the anode chamber of a dual-chamber electrolyzer. Active chlorine is generated through in-situ electrolysis of chloride ions in the water, progressively oxidizing and degrading ammonia nitrogen and COD. The anode chamber employs a gradient current reduction control mode: the first stage module current is 80%–100% of the full-load design current density (rated 100A), the second stage is 50%–75% (rated 75A), and the third stage is 30%–50% (rated 30A). Each series module has a pre-installed online sampling port. The current density of the module is controlled by a closed-loop regulation system based on the real-time concentration of ammonia nitrogen and COD in the effluent, adapting to fluctuations in the influent water quality. The operating current can be adjusted to a minimum of 30%–70% of the initial rated current.

[0018] (d) In-situ preparation of high-pH, low-potassium-sodium alkaline water: External clean water is continuously introduced into the cathode chamber. After energization, the cathode water is electrolyzed and dissociated to generate hydroxide ions. Trace amounts of potassium and sodium ions in the anode chamber migrate directionally through the cation exchange membrane to the cathode chamber and combine to generate low-potassium-sodium, high-pH finished alkaline water with a pH ≥ 13. The alkaline water production capacity can be matched by adjusting the clean water inlet flow rate. The alkaline water produced by the cathode chamber can maintain the water conductivity on its own without the need for external sodium hydroxide reagent.

[0019] (e) Alkali-assisted deep flocculation: Extract a portion of the alkaline water produced by the cathode and add it to the original wastewater or the filtrate from step (b) at a volume ratio of 1:0.5 to 1:2. After mixing, the overall pH of the water increases by ≤1, and the residual colloids in the water quickly flocculate and settle, resulting in the supernatant purified water.

[0020] (f) Evaporation and crystallization for salt separation: Purified water is sent to an evaporator crystallizer for evaporation, concentration and crystallization; because the colloid has been removed at the source, the produced salt crystals are white and loose, with independent particles and no adhesion. There is no problem of colloid sticking to the wall or encapsulating salt particles, and potassium chloride and sodium chloride can be directly separated.

[0021] (g) Resource reuse of alkaline water: The remaining self-produced alkaline water is collected and reused in a unified manner. It can be used as an industrial pH adjuster, heavy metal precipitant, water calcium and magnesium softener, flocculant, equipment descaling and cleaning agent, and soil conditioner.

[0022] Energy-saving bypass operation mode: If the pollutant indicators of the pretreated water from the single-chamber electrolyzer meet the standards, the double-chamber electrolysis process can be bypassed, and the filtrate can be directly reused / discharged in compliance with standards, or directly sent to the evaporation and crystallization unit to reduce electrolysis power consumption.

[0023] III. Beneficial Effects

[0024] Addressing the root cause of colloidal clogging: Unlike passive descaling methods such as scale inhibition and physical cleaning in the industry, this invention relies on a forced flow field with a slanted Z-shaped baffle to extend the hydraulic residence time. The combined action of coupled electric field dissociation and active chlorine oxidation directly breaks down large molecules of colloids and emulsions in the water, eliminating the problem of colloidal scaling and salt particle adhesion on the evaporation heat exchange surface from the root.

[0025] Excellent ammonia nitrogen degradation efficiency and strong industrial adaptability: Verified by industrial-scale joint tests in two major chemical plants in Jiangxi and Shanxi: In the Jiangxi plant, high-salt wastewater with initial ammonia nitrogen of 1000 mg / L was treated by a single-chamber electrolysis process and the effluent ammonia nitrogen was reduced to 6 mg / L, with an ammonia nitrogen removal rate of 99.4%; In the Shanxi plant, wastewater with initial ammonia nitrogen of 850 mg / L was treated by the entire system and the effluent ammonia nitrogen was reduced to 12 mg / L, with a removal rate of 98.6%.

[0026] Completely revitalize the capacity of existing evaporation equipment: The original 150-ton / day triple-effect evaporator in the Shanxi chemical plant was limited by colloidal blockage, with a long-term capacity of only 80-100 tons / day and an operating cycle of 3 days. After installing the pre-colloidal breaking unit of this system, the evaporator has been running continuously and stably for 15 days without significant scaling, the equipment cleaning cycle has been extended by 5 times, and the evaporation capacity has been restored to the rated 150 tons / day. The salt crystals in the evaporation are free from colloidal encapsulation, and potassium and sodium salts can be separated by conventional processes, filling the market gap in the industry where there is no radical cure for colloid-induced evaporation blockage.

[0027] Achieving efficient resource utilization of potassium and sodium salts: After conventional reagent pretreatment of wastewater, potassium and sodium mixed salts are encapsulated in colloids after evaporation, making them impossible to separate and utilize. This invention eliminates colloid interference at the source, resulting in independent and highly pure salt crystals. Potassium and sodium can be graded and purified using conventional stepwise crystallization and flotation processes, significantly increasing the economic added value of industrial salts.

[0028] Safe operation and no waste gas treatment costs: The entire electrolytic cell has a fully enclosed structure, and the electrolyzed hydrogen and chlorine dissolve in water in situ. There is no irritating waste gas overflow in the plant area, and no need for supporting tail gas absorption and treatment devices, which simplifies system matching and reduces operation and maintenance safety risks.

[0029] Gradient energy saving and controllable, adaptable to water quality fluctuations: The multi-level module gradient current reduction design of the anode chamber matches the concentration gradient of pollutants along the process of water degradation; combined with online closed-loop flow regulation of water quality and standard bypass energy saving mode, it takes into account both pollutant degradation effect and system electrolysis energy consumption.

[0030] The system features internal circulation of media and zero external addition of reagents: the cathode produces its own low-potassium, high-pH alkaline water, and deep colloid flocculation can be achieved with slight pH adjustment, eliminating the need to purchase flocculants or alkali-adjusting agents; the alkaline water can be reused in multiple scenarios to achieve closed-loop circulation of water treatment media.

[0031] Full-component resource utilization, cost reduction and efficiency improvement: The system simultaneously produces high-purity potassium / sodium salt and industrial high-pH alkaline water, reducing wastewater and solid waste, replacing purchased industrial reagents, and significantly reducing the cost of traditional process reagents and hazardous waste disposal.

[0032] Modular and easy to promote: The equipment is assembled in standardized modules, which can be connected in series and parallel as needed for expansion. It is easy to disassemble, install, and maintain, and is suitable for small to medium water volume to large-scale industrial wastewater treatment scenarios, making it highly practical. Attached Figure Description

[0033] Figure 1 The overall process flow diagram of this invention is as follows: The original wastewater (1) is electrolyzed and broken in the single-chamber electrolytic cell (2) and then enters the filter (3) for primary filtration and slag removal. The filtrate enters the anode chamber of the double-chamber electrolytic cell (4) for three-stage gradient electrolysis (current 100A→75A→30A). The effluent enters the secondary filter (5) and the filtrate is sent to the evaporator (6) for evaporation and salt separation, obtaining sodium salt (7), potassium salt (8), and recycled condensate (9). The clean water (11) is introduced into the cathode chamber of the double-chamber electrolytic cell (4) to produce a pH 13~14 finished liquid alkali (12). When the effluent from the single-chamber electrolysis meets the standards, it can be directly used as compliant water (10) for reuse and discharge, and the energy-saving bypass mode is activated.

[0034] Figure 2 Schematic diagram of the baffle plate structure of single-chamber and double-chamber electrolytic cells: The left side is a single-chamber electrolytic cell: The sealed cell body (1) is equipped with multiple layers of inclined Z-shaped baffle plates (2), with the baffle plate inclination angle of 5° to 30°; the anode plate (3) and cathode plate (4) are arranged vertically in pairs, and the back of the plate is connected to conduct electricity (5). There is a sealed water-passing interlayer (6) between the plates; the wastewater enters from the bottom (7) and exits from the top (8), and the electrolysis gas (9, 10) dissolves in the water without accumulation. The right side is a dual-chamber electrolytic cell: a cation exchange membrane (13) separates the anode chamber (14) and the cathode chamber (15); the two chambers are equipped with baffles (20, 21) and vertical plates (22, 23) respectively, the plate spacing is fixed at 20mm (25), the back wiring is (24), and the baffles are tilted at an angle of 5° to 30° (26); water enters from the bottom of the anode chamber (16) and exits from the top (18), clear water is added to the bottom of the cathode chamber (17) and alkaline solution is output from the top (19), producing liquid alkali with a pH ≥ 14.

[0035] Figure 3Diagram showing the effect of colloidal flocculation and sedimentation of self-produced alkaline water: A is the raw water, which is turbid and contains a large amount of colloids and emulsions; B is the water after single-chamber electrolysis, where the colloidal macromolecules are initially broken down and the water clarity is improved; C is the water after adding self-produced alkaline water, where the residual colloids quickly flocculate and settle, and the upper layer is a clean supernatant.

[0036] Figure 4 Comparison of salt samples before and after electrolytic pretreatment: The left side is the dried sample after treatment with raw water reagent: the bottom (1) is a viscous colloidal salt mixture, and the upper part (2) is a mixture of salt crystals that are stuck together, and potassium and sodium cannot be separated; the right side is the dried sample after electrolytic pretreatment of the present invention (3): the salt crystals are white and loose, with no colloidal residue, and the crystals are independent and can be directly sorted for potassium and sodium. Detailed Implementation

[0037] Example 1: Industrial-scale test at a Shanxi chemical plant (radical modification of existing triple-effect evaporator colloids)

[0038] Experimental background: A chemical plant in Shanxi has a 150-ton / day triple-effect evaporator. The wastewater colloids cannot be removed in the pre-treatment stage. The actual production capacity of the equipment is 80-100 tons / day, and the operating cycle is 3 days. The potassium and sodium salts in the evaporator are stuck together and cannot be separated. Physical cleaning and scale inhibitor addition cannot solve the problem effectively in the long term.

[0039] Experimental equipment configuration: The basic size of the single-chamber electrolytic cell is 800mm×1000mm, which can be enlarged as needed; the cell is equipped with 6 layers of 15mm thick inclined Z-shaped baffles with an inclination angle of 15°; the electrodes are titanium-based DSA anodes + titanium cathodes, vertically clamped, with a plate spacing of 20mm and back wiring for power supply; the filtration equipment is a 12m² plate and frame filter press with a filter cloth pore size of 5μm; the anode chamber of the double-chamber electrolytic cell is equipped with 3 sets of series electrolysis modules.

[0040] Water quality treated: The water is fed into the plant via a triple-effect evaporator. The mass ratio of potassium chloride to sodium chloride is 50:50, the total salinity is 8%, the ammonia nitrogen is 850 mg / L, the COD is 1200 mg / L, and it is rich in colloidal suspended flocs.

[0041] Operating parameters: single-chamber electrolytic cell current density 12mA / cm², hydraulic residence time 10min; the operating currents of the three-stage modules in the anode chamber are 100A, 75A, and 30A respectively.

[0042] Decolloid breaking effect: Compared with an equal volume of water sample after evaporation, the original water was rich in viscous colloids and salt particles were mixed and adhered at the bottom after evaporation; after electrolysis, the water sample was dried without colloidal residue, the salt crystals were independent, and the potassium and sodium salts crystallized independently and could be directly separated by stepwise crystallization.

[0043] Effluent and resource utilization indicators: The system effluent has an ammonia nitrogen content of 12 mg / L, a COD content of 45 mg / L, and no residual active chlorine in the water; the self-produced alkaline water at the cathode has a pH ≥ 14; when the alkaline water is mixed with the raw water at a volume ratio of 1:0.5, the pH increase of the water body is ≤ 1, the flocs completely settle in 10 minutes, and the supernatant is clean and transparent.

[0044] The transformation results: the evaporator capacity was restored to the rated 150 tons / day, the evaporation efficiency was increased by 50% to 87.5%, it operated continuously and stably for 15 days without scaling or clogging, the equipment cleaning cycle was extended by 5 times, and the industry problem of evaporation blockage induced by colloids was completely solved.

[0045] Example 2: Low ammonia nitrogen water quality energy-saving bypass operation mode

[0046] Applicable operating conditions: raw water ammonia nitrogen concentration ≤200mg / L; operation mode: after single-chamber electrolysis pretreatment meets the standards, the double-chamber electrolysis cell is shut down, and the water is directly filtered and evaporated or discharged in compliance with standards; operating energy consumption: the bypass mode consumes only 6.5kWh of electricity per ton of water, which greatly reduces the operation and maintenance costs of electrolysis.

[0047] Example 3: Verification Test of Micro-pH Adjustment and Flocculation with Self-Produced Alkaline Water

[0048] Experimental conditions: Take 100 mL of raw water from the plant area, with an initial pH of 7.2; add 50 mL of self-produced alkaline water; Experimental results: After mixing, the pH of the water body is 7.3, with a pH increase of 0.1 (increase ≤ 1); after mixing for 1 min, white flocs are quickly generated; after standing for 5 min, more than half of the flocs have settled; after 10 min, the supernatant is completely clear; high-efficiency colloidal flocculation can be achieved with low alkalinity and increased volume.

[0049] Example 4: Single Electrolytic Degradation Test of High-Concentration Ammonia Nitrogen at a Jiangxi Chemical Plant

[0050] Water quality treated: High-salt wastewater from Jiangxi fine chemical industry, with an initial ammonia nitrogen of 1000 mg / L; Treatment process: Single-chamber electrolytic cell single-electrolysis treatment only; Treatment results: Under normal operating conditions, the effluent ammonia nitrogen is as low as 6 mg / L, with a removal rate of 99.4%; Under low-configuration energy-saving operating conditions, the effluent ammonia nitrogen is 46 mg / L, which can be flexibly adapted to local graded discharge standards.

[0051] Industrial applicability

[0052] Applicable industries: Treatment of high-salt, high-ammonia-nitrogen, colloidal emulsified wastewater and salt resource recovery in the entire industry of pesticides, pharmaceuticals, printing and dyeing, and fine chemicals.

[0053] Suitable for specific scenarios: Existing evaporation equipment that has been put into use with triple-effect evaporation and MVR evaporation but whose production capacity has been halved due to colloidal blockage and has a high frequency of operation and maintenance can be retrofitted with this electrolytic colloidal breaking module to restore the rated production capacity of the equipment.

[0054] Equipment 0048 adaptability: Full range of standardized modular units, small testing machines and large industrial units can be customized; back-connected electrode plate with closed flow field structure, high operational stability, and convenient assembly and maintenance.

[0055] Verification from actual implementation: After long-term industrial trial operation in two major chemical plant areas in Jiangxi and Shanxi, the effects of debinding, denitrification, and salt separation are stable, achieving the triple benefits of wastewater compliance, salt quality improvement, and alkaline water reuse. It has outstanding economic and environmental value and is ready for large-scale industrial promotion.

Claims

1. A resource-based treatment system for high-salt, high-ammonia-nitrogen wastewater, used to break down colloids and emulsions in the wastewater and recover salt crystals, characterized in that, It includes a single-chamber electrolytic cell, a filtration device, and a double-chamber electrolytic cell connected in sequence; Both the single-chamber and double-chamber electrolytic cells are closed structures, with multiple layers of inclined Z-shaped baffles installed inside. The baffles are bent in a Z-shape along the horizontal direction and are inclined upward at 5° to 30° relative to the horizontal surface, dividing the space inside the cell into multiple closed baffled water passage chambers that are connected vertically. Vertically clamped electrode plates are arranged inside the cell, with the electrode plates and the straight sections of the baffles parallel to each other, and the spacing between the electrode plates is fixed at 20mm. The electrode plates adopt a back-connected conductive structure, and an independent closed water-passing interlayer is formed between the positive and negative electrode plates. The wastewater flows back and forth in the baffle channels of the electrode plate interlayer from bottom to top. The gas generated by electrolysis is carried and dissolved by the flowing water, and there is no local accumulation of gas or water overflow in the cell. The dual-chamber electrolytic cell is internally divided into an anode chamber and a cathode chamber by a cation exchange membrane. Both the anode chamber and the cathode chamber are equipped with the aforementioned inclined Z-shaped baffles and vertical electrode plates. The anode chamber is composed of multiple electrolysis modules connected in series. The anode chamber inlet is connected to the filtrate outlet of the filtration equipment. The anode chamber is equipped with an online active chlorine monitoring device. The cathode chamber is equipped with a clean water inlet and an alkaline water outlet. Both the single-chamber and double-chamber electrolytic cells can be composed of 2 to 6 standardized module units connected in parallel, with detachable pipelines connecting the modules.

2. The system according to claim 1, characterized in that, The single-chamber electrolytic cell is used for electrolytic pretreatment of raw wastewater. Electrolysis breaks down emulsions and decomposes colloids at the source, eliminating the adhesion interference of colloids to salt crystallization during subsequent evaporation and crystallization processes and the obstruction of potassium and sodium separation. The electrolytic gas is carried and dissolved by the flowing water, and there is no gas accumulation in the cell.

3. The system according to claim 1, characterized in that, The anode chamber of the dual-chamber electrolyzer consists of multiple electrolysis modules connected in series. The current density of each module decreases gradually along the water flow direction: the first stage is 80% to 100% of the designed full-load current density, the second stage is 50% to 70%, and the third stage is 30% to 50%. Sampling ports are set between the modules, and the current density is adjusted online by detecting the concentration of ammonia nitrogen and COD in the effluent to form a closed-loop control.

4. A method for the resource-based treatment of high-salt, high-ammonia-nitrogen wastewater, characterized in that, The system according to any one of claims 1 to 3 includes the following steps: (a) The raw wastewater containing potassium ions, sodium ions, chloride ions, ammonia nitrogen, COD, colloids and emulsions is passed into a closed single-chamber electrolytic cell for electrolytic pretreatment. Electrolysis is used to break down emulsions and decompose colloids from the source, eliminating the adhesion interference of colloids to salt crystallization during subsequent evaporation and crystallization and the obstruction of potassium and sodium separation. The electrolysis gas is carried and dissolved by the flowing water, avoiding gas accumulation in the cell. (b) The pretreated effluent is sent to a filtration device to complete solid-liquid separation and obtain filtrate; (c) The filtrate sequentially enters the multi-stage series electrolysis modules in the anode chamber of the dual-chamber electrolyzer, where active chlorine generated by chloride ion electrolysis is used to oxidize and degrade ammonia nitrogen and COD in stages. The current density of each module decreases progressively along the water flow direction: the first stage is 80%–100% of the designed full-load current density, the second stage is 50%–70%, and the third stage is 30%–50%. Sampling ports are set between modules, and the current density is adjusted online by detecting the concentration of ammonia nitrogen and COD in the effluent, forming a closed-loop control. At the same time, the current density can be adjusted in real time according to the concentration of pollutants in the influent, and can be reduced to as low as 30%–70% of the initial current. (d) Clean water is continuously introduced into the cathode chamber. After the power is turned on, the water on the cathode side is electrolyzed to generate hydroxide ions. A small amount of potassium and sodium ions in the anode chamber migrate through the cation exchange membrane to the cathode chamber and combine to generate low potassium and sodium high pH alkaline water with pH ≥ 13. The alkaline water production is controlled by adjusting the amount of clean water introduced. After the cathode chamber is started, the conductivity is maintained by the self-produced alkaline water, and there is no need to continuously add sodium hydroxide. (e) Take a portion of the self-produced alkaline water and add it to the original wastewater or filtrate at a volume ratio of 1:0.5 to 1:

2. After mixing, the pH of the system will increase by no more than 1 unit. The colloids in the wastewater will quickly flocculate and precipitate visible flocs. After the flocs settle, purified water is obtained. (f) The purified water is sent to the evaporator crystallizer for evaporation and crystallization. Since the colloid has been broken down at the source, the salt crystals are white, with distinct particles and loose state, without the phenomenon of colloidal stickiness. High-purity salt crystals are obtained, which lays the foundation for subsequent potassium and sodium separation. (g) The remaining alkaline water is recycled and can be used as a pH adjuster, heavy metal precipitant, calcium and magnesium softener, flocculant, equipment cleaning medium or soil conditioner.

5. The method according to claim 4, characterized in that, When the effluent from the single-chamber electrolyzer meets the standards, the double-chamber electrolysis process can be skipped directly, and the filtrate can be sent to the evaporator crystallizer to achieve energy-saving operation.

6. The method according to claim 4, characterized in that, The alkaline water produced by the cathode chamber is a low-potassium, high-sodium alkaline water with a pH ≥ 13. The alkaline water is added to the original wastewater or filtrate at a volume ratio of 1:0.5 to 1:

2. After mixing, the pH of the system increases by no more than 1 unit. The colloids in the wastewater quickly flocculate and precipitate visible flocs. After the flocs settle, purified water is obtained.

7. The method according to claim 4, characterized in that, After being treated in a single-chamber electrolytic cell, the water sample was white, with distinct and loose particles, and no colloid stickiness after evaporation. Untreated wastewater, after evaporation, left behind viscous colloids, and the salt crystals were sticky and indistinct.

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