A method and system for zero-discharge treatment of high-salinity wastewater

Abstract

The present invention relates to a high-salt wastewater zero-discharge treatment system, comprising a regulating tank, a reaction tank, a sedimentation tank, a multi-media filter, a security filter and a reverse osmosis device connected in sequence; and also comprising a deep-cold salt separation device, wherein the concentrated solution outlet of the reverse osmosis device is connected to the inlet of the deep-cold salt separation device, and the outlet of the deep-cold salt separation device is connected to the sewage inlet of the reverse osmosis device. The high-salt wastewater zero-discharge treatment device provided by the present invention does not require low-temperature evaporation equipment to separate brine, has low equipment cost, and does not require a heat source, and has a low cost per ton of water treatment in actual operation; has low operational difficulty and low failure rate, and the device does not remove salts in high-salt wastewater by evaporation, so there is no situation where a large amount of precipitation adheres to the inner wall of the heat exchange tube, and will not cause equipment failure and shutdown; the device does not require pretreatment, has low investment, and low maintenance cost.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method and system for zero-discharge treatment of high-salinity wastewater. Background Art

[0002] With the rapid development of industry, people's requirements for wastewater discharge are gradually increasing. At present, almost all high-salinity wastewater final treatment requires the use of low-temperature evaporators for brine separation. This method has the following technical problems:

[0003] 1. Low-temperature evaporation equipment is expensive, requires large investment, and requires a heat source. The cost of treating one ton of water is high in actual operation;

[0004] 2. The operation is difficult and failures are frequent and difficult to overcome. Due to the complex composition of high-salt wastewater, a large amount of precipitation is easily generated during the evaporation process, which is easy to adhere to the inner wall of the heat exchange tube to form complex and difficult-to-clean composite scale such as calcium sulfate and silicate, resulting in a decrease in heat exchange efficiency and a doubling of the cost per ton of water. It can even block the water inlet or outlet, causing equipment failure and shutdown.

[0005] 3. High pretreatment requirements, large investment and high maintenance costs. Summary of the invention

[0006] The object of the present invention is to provide a method and system for zero-discharge treatment of high-salinity wastewater to solve at least one of the above-mentioned technical problems.

[0007] A technical solution of the present application is: a high-salt wastewater zero-discharge treatment system, comprising a regulating tank, a reaction tank, a sedimentation tank, a multi-media filter, a security filter and a reverse osmosis device connected in sequence; and also comprising a deep-cold salt separation device, wherein the concentrated solution outlet of the reverse osmosis device is connected to the inlet of the deep-cold salt separation device, and the outlet of the deep-cold salt separation device is connected to the sewage inlet of the reverse osmosis device.

[0008] Preferably, an ultrafilter is provided between the security filter and the reverse osmosis device, the water inlet of the ultrafilter is connected to the outlet of the security filter, and the drain outlet of the security filter is connected to the water inlet of the reverse osmosis device.

[0009] Preferably, a nanofilter is arranged between the ultrafilter and the reverse osmosis device, the inlet of the nanofilter is connected to the drain outlet of the security filter, the drain outlet of the nanofilter is connected to the water inlet of the reverse osmosis device; the concentrated solution outlet of the nanofilter is connected to the reaction tank.

[0010] The high-salt wastewater zero-discharge treatment device provided by the present invention converts difficult-to-remove salts such as NaCl and Na2SO4 in the high-salt wastewater into NaOH, and utilizes the characteristic that the solubility of NaOH is greatly affected by temperature fluctuations. According to actual conditions, a refrigerator is configured to provide a refrigerant at -35 to 10°C to perform deep cooling and salt separation on the solution. The process is simple and the operation is convenient.

[0011] The high-salt wastewater zero-discharge treatment device provided by the present invention has the following advantages:

[0012] 1. No low-temperature evaporation equipment is required for brine separation, the equipment cost is low, and no heat source is required. The cost of treating one ton of water in actual operation is low;

[0013] 2. Low operating difficulty and low failure rate. The device does not use evaporation to remove salts from high-salinity wastewater. Therefore, there is no large amount of precipitation attached to the inner wall of the heat exchange tube, and it will not cause equipment failure and shutdown;

[0014] 3. The device does not require pretreatment, has small investment and low maintenance cost.

[0015] Another technical solution of the present application is: a method for treating high-salt wastewater with zero discharge, using the above-mentioned high-salt wastewater zero discharge treatment device, comprising the following steps:

[0016] Step 1, pumping high-salinity wastewater into a regulating tank for storage;

[0017] Step 2, introducing the high-salt wastewater from the regulating tank into the reaction tank, adding a mixture of lime and aluminum salt into the reaction tank, controlling the pH at 11-12, removing divalent and higher metal ions and acid radical ions, and forming an alkaline solution mainly composed of NaOH and a mixture of precipitates;

[0018] Step 3, introducing the mixture into a sedimentation tank to separate the precipitate from the solution, and after the mixture is separated by sedimentation, a supernatant containing NaOH as a main component is formed at the upper part of the sedimentation tank;

[0019] Step 4, filtering the supernatant through a multi-media filter and a security filter in sequence to form a filtered solution;

[0020] Step 5, the filtered solution is treated by a reverse osmosis device to form pure water, the concentrated solution produced during the treatment process is placed in a deep cold salt separation device for salt separation treatment to obtain a dilute solution and NaOH crystals, the dilute solution is again treated by a reverse osmosis device, and the water and salt are finally separated completely through repeated cycles, thereby achieving the final separation of salt and water in the high-salt wastewater.

[0021] Preferably, after step 4 and before step 5, the method further includes: step 41, filtering the filtered solution through an ultrafiltration filter.

[0022] Preferably, after step 41 and before step 5, the method further includes: step 42, a step of filtering the filtered solution through a nanofilter, wherein the concentrated solution produced by the filtration is introduced into a reaction tank for further treatment.

[0023] Preferably, the separation method in step 3 is: adding an inorganic flocculant such as PAC and a coagulant aid PAM into a sedimentation tank to flocculate and precipitate the precipitate in the reaction tank;

[0024] If there is excess lime and aluminum salt in the reaction tank, Na2CO3 can be added to precipitate and remove it;

[0025] If the waste liquid contains heavy metals, add heavy metal remover to remove the residual heavy metals.

[0026] The high-salinity wastewater zero-discharge treatment method provided by the present invention uses lime added in the precipitation method to precipitate and remove divalent or higher metal ions and weak acid ions, and calcium aluminum composite salt to precipitate and remove chloride ions and strong acid ions of sulfate, and then separates the solid and liquid in the sedimentation tank, separates the water from the solution through the reverse osmosis system, and obtains a dilute solution through deep cold crystallization of the concentrated solution, and the dilute solution returns to the reverse osmosis cycle for dehydration and deep cold crystallization, and finally realizes the separation of salt water. The NaOH crystals obtained by salt water separation are high-value byproducts and can be recycled.

[0027] The zero-discharge treatment method for high-salt wastewater provided by the present invention has the following advantages:

[0028] 1. No low-temperature evaporation equipment is required for brine separation, the equipment cost is low, and no heat source is required. The cost of treating one ton of water in actual operation is low;

[0029] 2. Low operating difficulty and low failure rate. The device does not use evaporation to remove salts from high-salinity wastewater. Therefore, there is no large amount of precipitation attached to the inner wall of the heat exchange tube, and it will not cause equipment failure and shutdown;

[0030] 3. The device does not require pretreatment, has small investment and low maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic structural diagram of a zero-discharge treatment device for high-salinity wastewater in Example 1, wherein arrows are used to schematically indicate the flow direction of the liquid;

[0032] The accompanying drawings are denoted by: regulating tank 1, reaction tank 2, stirring device 2-1, sedimentation tank 3, multi-media filter 4, security filter 5, reverse osmosis equipment 6, deep cold salt separation device 7, ultrafilter 8, nanofilter 9. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] The high-salt wastewater mentioned in this application refers to wastewater with a sodium chloride or sodium sulfate content between 10% and 20%, and also contains high concentrations of other salts.

[0035] Example 1. The present invention provides a high-salt wastewater zero-discharge treatment device, comprising a regulating tank 1, a reaction tank 2, a sedimentation tank 3, a multi-media filter 4, a security filter 5 and a reverse osmosis device 6 connected in sequence; and also comprising a deep-cold salt separation device 7, wherein the concentrated solution outlet of the reverse osmosis device is connected to the inlet of the deep-cold salt separation device, and the outlet of the deep-cold salt separation device is connected to the sewage inlet of the reverse osmosis device, wherein the reaction tank generally has a stirring device 2-1 to stir the liquid so that it reacts with the agent faster, and the above-mentioned various devices can transfer the liquid between adjacent devices by setting a height difference, and can also transfer the liquid between adjacent devices by setting a pump, which are all well known to those skilled in the art and will not be repeated here.

[0036] The above-mentioned high-salt wastewater zero-discharge treatment device converts difficult-to-remove salts such as NaCl and Na2SO4 in high-salt wastewater into NaOH, and utilizes the characteristic that the solubility of NaOH is greatly affected by temperature fluctuations. According to actual conditions, the refrigerant is configured to provide -35 to 10°C chilled water to deep-cold the solution for salt separation. The process is simple and easy to operate.

[0037] The high-salt wastewater zero discharge treatment device has the following advantages:

[0038] 1. No low-temperature evaporation equipment is required for brine separation, the equipment cost is low, and no heat source is required. The cost of treating one ton of water in actual operation is low;

[0039] 2. Low operating difficulty and low failure rate. The device does not use evaporation to remove salts from high-salinity wastewater. Therefore, there is no large amount of precipitation attached to the inner wall of the heat exchange tube, and it will not cause equipment failure and shutdown;

[0040] 3. The device does not require pretreatment, has small investment and low maintenance cost.

[0041] As a preferred embodiment, an ultrafilter 8 is provided between the security filter and the reverse osmosis device, the water inlet of the ultrafilter is connected to the outlet of the security filter, and the drain outlet of the security filter is connected to the water inlet of the reverse osmosis device. In this way, the impurities in the filtered solution can be further removed after further filtering, which is more conducive to the treatment of the reverse osmosis device.

[0042] As a preferred embodiment, a nanofilter 9 is arranged between the ultrafilter and the reverse osmosis equipment, the inlet of the nanofilter is connected to the drain outlet of the security filter, and the drain outlet of the nanofilter is connected to the water inlet of the reverse osmosis equipment; the concentrated solution outlet of the nanofilter is connected to the reaction tank, so that the concentrated solution generated by the nanofilter can be recycled and processed again to improve the generation of pure water.

[0043] Embodiment 2, a method for treating high-salinity wastewater with zero discharge, using the above-mentioned high-salinity wastewater zero discharge treatment device, comprises the following steps:

[0044] Step 1, pumping high-salinity wastewater into a regulating tank for storage;

[0045] Step 2, introducing the high-salt wastewater from the regulating tank into the reaction tank, adding a mixture of lime and aluminum salt to the reaction tank, controlling the pH at 11-12, removing divalent and higher metal ions and acid ions, and forming an alkaline solution and a precipitate mixture mainly composed of NaOH, wherein the removed acid ions include weak acid ions, chloride ions and sulfate ions, etc., the chloride ions are removed by forming a calcium aluminum chloride hydrate precipitate through a calcium aluminum mixture, and the sulfate ions are removed by forming a calcium aluminum sulfate hydrate precipitate through a calcium aluminum mixture;

[0046] Step 3, introducing the mixture into a sedimentation tank to separate the precipitate from the solution, and after the mixture is separated by sedimentation, a supernatant containing NaOH as a main component is formed at the upper part of the sedimentation tank;

[0047] Step 4, filtering the supernatant through a multi-media filter and a security filter in sequence to form a filtered solution;

[0048] Step 5, the filtered solution is treated by a reverse osmosis device to form pure water, and the concentrated solution generated during the treatment process is placed in a deep cold salt separation device for salt separation treatment using the principle that the solubility of NaOH changes with temperature to obtain a dilute solution and NaOH crystals, and the dilute solution is again treated by a reverse osmosis device, and the water and salt are finally completely separated by repeated cycles, thereby achieving the final separation of salt and water in the high-salt wastewater.

[0049] This treatment method uses lime added in the precipitation method to precipitate and remove divalent or higher metal ions and weak acid ions, and calcium aluminum complex salt to precipitate and remove chloride ions and strong acid ions such as sulfate, and then separates the solid and liquid in the sedimentation tank. The water is separated from the solution through the reverse osmosis system, and the concentrated solution is crystallized by deep cold to obtain a dilute solution. The dilute solution returns to the reverse osmosis cycle for dehydration and deep cold crystallization, and finally achieves brine separation. The NaOH crystals obtained from brine separation are high-value byproducts and can be recycled.

[0050] The high-salinity wastewater zero-discharge treatment method has the following advantages:

[0051] 1. No low-temperature evaporation equipment is required for brine separation, the equipment cost is low, and no heat source is required. The cost of treating one ton of water in actual operation is low;

[0052] 2. Low operating difficulty and low failure rate. The device does not use evaporation to remove salts from high-salinity wastewater. Therefore, there is no large amount of precipitation attached to the inner wall of the heat exchange tube, and it will not cause equipment failure and shutdown;

[0053] 3. The device does not require pretreatment, has small investment and low maintenance cost.

[0054] As a preferred implementation, after step 4 and before step 5, the following steps are further included:

[0055] Step 41 is a step of filtering the filtered solution through an ultrafiltration filter, so that the impurities in the filtered solution are further removed after further filtering, which is more conducive to the treatment of the reverse osmosis device.

[0056] As a preferred implementation, after step 41 and before step 5, the following steps are further included:

[0057] Step 42 is a step of filtering the filtered solution through a nanofilter, wherein the concentrated solution produced by the filtration is introduced into a reaction tank for further treatment. In this way, the concentrated solution produced by the nanofilter can be recycled for treatment again to increase the generation of pure water.

[0058] As a specific implementation method, the separation method in the above step 3 is: adding an inorganic flocculant such as PAC and a coagulant aid PAM into a sedimentation tank to flocculate and precipitate the precipitate in the reaction tank;

[0059] If there is excess lime and aluminum salt in the reaction tank, Na2CO3 can be added to precipitate and remove it;

[0060] If the waste liquid contains heavy metals, a heavy metal remover is added to remove the residual heavy metals. The heavy metal remover can be an organic sulfur heavy metal remover, which is well known to those skilled in the art and will not be described in detail here;

[0061] The residual cold of the dilute solution after cryogenic treatment can be exchanged with the water entering the cryogenic device through a heat exchanger to ensure cold recovery.

[0062] The following is a comparison table of using the high-salt wastewater zero-discharge treatment device and method of the present invention and using the existing high-salt wastewater zero-discharge treatment device and method to treat high-salt wastewater:

[0063]

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The words "first" and "second" are only used to distinguish the names and are not intended to limit the technical terms. For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating high-salt wastewater with zero discharge, using a high-salt wastewater zero discharge treatment device, the high-salt wastewater zero discharge treatment device comprising a regulating tank (1), a reaction tank (2), a sedimentation tank (3), a multi-media filter (4), a security filter (5) and a reverse osmosis device (6) connected in sequence, and also comprising a deep-cold salt separation device (7), wherein the concentrated solution outlet of the reverse osmosis device is connected to the inlet of the deep-cold salt separation device, and the outlet of the deep-cold salt separation device is connected to the sewage inlet of the reverse osmosis device; The high-salinity wastewater zero-discharge treatment method comprises the following steps: Step 1, pumping high-salinity wastewater into a regulating tank for storage; Step 2, introducing the high-salt wastewater from the regulating tank into the reaction tank, adding a mixture of lime and aluminum salt into the reaction tank, controlling the pH at 11-12, removing divalent and higher metal ions and acid radical ions, and forming an alkaline solution mainly composed of NaOH and a mixture of precipitates; Step 3, introducing the mixture into a sedimentation tank to separate the precipitate from the solution, and after the mixture is separated by sedimentation, a supernatant containing NaOH as a main component is formed at the upper part of the sedimentation tank; Step 4, filtering the supernatant through a multi-media filter and a security filter in sequence to form a filtered solution; Step 5, the filtered solution is treated by a reverse osmosis device to form pure water, the concentrated solution produced during the treatment process is placed in a deep cold salt separation device for salt separation treatment to obtain a dilute solution and NaOH crystals, the dilute solution is again treated by a reverse osmosis device, and the water and salt are finally separated completely through repeated cycles, thereby achieving the final separation of salt and water in the high-salt wastewater.

2. A method for zero-discharge treatment of high-salinity wastewater according to claim 1, characterized in that: An ultrafilter (8) is arranged between the security filter and the reverse osmosis device, the water inlet of the ultrafilter is connected to the outlet of the security filter, and the drain outlet of the security filter is connected to the water inlet of the reverse osmosis device.

3. A high-salinity wastewater zero-discharge treatment method according to claim 2, characterized in that: A nanofilter (9) is provided between the ultrafilter and the reverse osmosis device, the inlet of the nanofilter is connected to the drain outlet of the security filter, and the drain outlet of the nanofilter is connected to the water inlet of the reverse osmosis device; The concentrated solution outlet of the nanofilter is connected to the reaction tank.

4. A method for zero-discharge treatment of high-salinity wastewater according to claim 3, characterized in that: After step 4 and before step 5, the following steps are also included: Step 41 is a step of filtering the filtered solution through an ultrafilter.

5. A method for zero-discharge treatment of high-salinity wastewater according to claim 4, characterized in that: After step 41 and before step 5, the following steps are also included: Step 42 is a step of filtering the filtered solution through a nanofilter, wherein the concentrated solution produced by the filtration is introduced into a reaction tank for further treatment.

6. A method for zero-discharge treatment of high-salinity wastewater according to claim 1, characterized in that: The separation method in step 3 is: adding an inorganic flocculant into a sedimentation tank to flocculate and precipitate the precipitate in the reaction tank; If there is excess lime and aluminum salt in the reaction tank, add Na2CO3 to precipitate and remove it; If the waste liquid contains heavy metals, add heavy metal remover to remove the residual heavy metals.

Images