Oxidation flocculation ultrafiltration treatment process for low-level radioactive wastewater

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process which comprises the following steps: a pretreatment unit: obtaining wastewater without larger impurities; the oxidation / flocculation unit is used for obtaining wastewater with radionuclide flocculate; an intermittent operation mode is adopted; the ultrafiltration unit is used for obtaining radionuclide purified wastewater; a continuous operation mode is adopted; and the de-ion exchange system is used for carrying out deep purification treatment on the ultra-filtered radionuclide wastewater to obtain purified water meeting national standard discharge requirements. The pretreatment unit, the oxidation / flocculation unit, the ultrafiltration unit and the de-ion exchange system are used in cooperation, multiple treatments are achieved, the pretreatment unit can be used for conducting pre-filtration treatment on wastewater, then the oxidation / flocculation unit is used for conducting oxidation, PH adjustment and flocculation treatment on the wastewater in sequence, and the wastewater treatment efficiency is improved. And then the wastewater is filtered in cooperation with an ultrafiltration unit, and water which does not meet the discharge requirement can be conveyed to a de-ion exchange system for deep purification.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to an oxidation flocculation ultrafiltration treatment process for low-level radioactive wastewater. Background Art

[0002] Wastewater treatment refers to the use of physical, chemical and biological methods to treat wastewater, with the aim of purifying wastewater, reducing pollution, and even achieving wastewater recovery and reuse, and making full use of water resources. In the treatment of low-level radioactive wastewater, the main treatment processes include chemical precipitation, ion exchange, membrane filtration, and biological treatment.

[0003] After searching, the patent number is CN103745759B, and the name is Invention of a method and device for treating radioactive wastewater. The radioactive wastewater is treated by a disc-tube reverse osmosis membrane assembly. Through research and analysis, it is found that although the effects of high decontamination factor and high concentration multiple are achieved at the same time, the following disadvantages still exist to a certain extent.

[0004] For example, the device uses a three-stage disc-tube reverse osmosis membrane assembly to concentrate and purify the waste liquid. The disc-tube membrane assembly has a low membrane packing density and a limited membrane area per unit volume. To achieve a certain processing capacity, a large number of membrane columns are required, and each disc-tube membrane assembly has 400 sealing rings. Once there is a leak, the column must be dismantled for inspection and replacement. In the case of radioactive operations, frequent inspections are impractical, and it is impossible to have the functions of oxidation, pH adjustment, flocculation and ultrafiltration. In order to solve the above technical problems, we have designed an oxidation flocculation ultrafiltration treatment process for low-level radioactive wastewater. Summary of the invention

[0005] The purpose of the present invention is to provide an oxidation flocculation ultrafiltration treatment process for low-level radioactive wastewater, which has the advantages of multiple treatments and solves the problems that the basic treatment process cannot have the functions of oxidation, pH adjustment, flocculation and ultrafiltration, and has a low concentration multiple and general purification efficiency for low-level radioactive wastewater.

[0006] To achieve the above object, the present invention provides the following technical solution: a low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process, comprising the following steps: A: Pre-treatment unit: The radioactive wastewater is treated by filtering to obtain wastewater without large impurities; B: Oxidation / flocculation unit: add oxidant to the filtered wastewater for reaction, then add NaOH to adjust the pH value of the wastewater, and finally add flocculant to form wastewater with precipitate, thus obtaining wastewater with flocculants; the wastewater is treated in intermittent operation; C: Ultrafiltration unit: The flocculated wastewater is separated and purified again using an ultrafiltration membrane to obtain purified wastewater; it is operated continuously; D: Deionized exchange system: The wastewater after ultrafiltration is deeply purified by using ion exchange resin to obtain the re-purified water.

[0007] Preferably, in the step A, the filtration aperture of the pretreatment unit is 1-5 μm.

[0008] Preferably, in the step B, by using multiple dosing pumps, the FeSO4 solution and the KMnO4 solution are put into the filtered wastewater, and the reaction time is 4-7 min; the HNO3 solution is put into the wastewater, and the reaction time is 4-8 min.

[0009] Preferably, in the step B, by using a dosing pump, the NaOH solution is put into the wastewater, and the reaction time is 5-7 min; the flocculant is put into the wastewater, and the reaction time is 5-10 min, and the standing time is 2-4 min.

[0010] Preferably, in the step B, during operation, the motor drives the paddle to stir, and the motor speed is and is combined with an air compressor for aeration treatment.

[0011] Preferably, in the step C, the aperture specification of the ultrafiltration membrane is 10-100 nm, and an air compressor is used for aeration treatment.

[0012] Preferably, in the step D, the ion exchange resin includes strongly basic styrene anion exchange resin of model 201X7 and macroporous strongly acidic styrene-based cation exchange resin of model D001.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: By using the pretreatment unit, oxidation / flocculation unit, ultrafiltration unit and deionized exchange system in combination, the present invention has multiple treatments, and can pre-filter the wastewater by using the pretreatment unit, and then the oxidation / flocculation unit sequentially performs oxidation, pH adjustment and flocculation treatment on the wastewater, and then cooperates with the ultrafiltration unit to filter the wastewater, and finally transmits the filtered water to the deionized exchange system for deep purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the process flow chart of the present invention; Figure 2 is the process schematic diagram of the present invention; Figure 3 is the floor plan of the present invention; Figure 4 is the schematic diagram of the oxidation / flocculation unit of the present invention; Figure 5 is the schematic diagram of the membrane separation unit of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Implementation: Please refer to Figures 1-5 , the oxidation flocculation ultrafiltration treatment process for low-level radioactive wastewater, including the following steps: A: Pretreatment unit: Treat the radioactive wastewater by filtration to obtain wastewater without large impurities; B: Oxidation / flocculation unit: Add an oxidant to the filtered wastewater for reaction, then add NaOH to adjust the pH value of the wastewater, and finally add a flocculant to form wastewater with precipitates, obtaining wastewater with flocs; The designed flow rate of the oxidation / flocculation unit is 1 m³ / h, the effective volume of the reactor is 0.5 m³, and the intermittent operation mode is adopted during wastewater treatment. The main material of this treatment unit is stainless steel. The main devices include 1 inlet pump, 1 outlet pump, and 1 mechanical stirrer. The appearance is as shown in the attached drawings of the specification Figure 4 shown, with dimensions of Φ900mm × 2000mm. The device operates with aeration to improve the reaction rate; C: Ultrafiltration unit: Use an ultrafiltration membrane to further separate and purify the flocculated wastewater to obtain purified wastewater; The designed flow rate of the ultrafiltration unit is 1 m³ / h, and the effective volume of the reactor is 0.5 m³; The continuous operation mode is adopted; The designed membrane flux is 27 L / (㎡·h), and the appearance is as shown in the attached drawings of the specification Figure 5 shown, with dimensions of Φ1600mm × 2000mm. The air compressor of the device aerates the device to improve the ultrafiltration rate and extend the service life of the membrane; D: Ion exchange system: Use ion exchange resin to deeply purify the ultrafiltered wastewater to obtain re-purified water; In step A, the filtration pore size of the pretreatment unit is 3 mm; In step B, use multiple dosing pumps to put FeSO4 solution and KMnO4 solution into the filtered wastewater, and the reaction time is 5 min; Put HNO3 solution into the wastewater, and the reaction time is 5 min; In step B, use a dosing pump to put NaOH solution into the wastewater, and the reaction time is 5 min; Put the flocculant into the wastewater, and the reaction time is 6 min, and the standing time is 2.5 min; In step B, during operation, the motor drives the paddle to stir, and the motor speed is and cooperate with the air compressor for aeration treatment; In step C, the pore size specification of the ultrafiltration membrane is 10 - 100 nm, and aeration treatment is carried out using an air compressor; In step D, the ion exchange resin includes strongly basic styrene anion exchange resin of model 201X7 and macroporous strongly acidic styrene cation exchange resin of model D001; All equipment in this process adopts PLC automatic control and reserves interfaces for subsequent expansion. The two component units adopt intermittent and continuous operation modes respectively. To ensure the stable operation of the system, a reasonable control timing needs to be designed to maximize the efficiency of each equipment during the wastewater treatment process; The oxidation / flocculation treatment unit is equipped with a liquid level sensor. When the reactor is at a low liquid level, the influent pump is started to add wastewater into the reactor, and when it reaches a high liquid level, the influent pump is closed, and this cycle continues; The ultrafiltration unit is equipped with a liquid level sensor and a timer. When the reactor is at a low liquid level, water enters. When it reaches a high liquid level, the influent pump is closed, and then the effluent pump of the ultrafiltration unit is opened. It operates in a mode of discharging water for 10 minutes and being idle for 2 minutes. During this period, aeration continues until the ultrafiltration unit is at a low liquid level, and this cycle continues; This treatment process is applicable to radioactive waste liquid with a concentration multiple of not less than 600, and its structure meets the requirements for installation in a mobile cabin.

[0016] During use, the radioactive wastewater is pretreated by the pretreatment unit and then enters the oxidation / flocculation unit of the treatment component. Under acidic conditions, potassium permanganate can oxidize organic substances such as surfactants and oils in the wastewater, and then neutralize with sodium hydroxide. At the same time, ferrous ions reduce the excessive potassium permanganate, and the generated ferric ions hydrolyze into ferric hydroxide colloids, which can strongly adsorb radionuclides such as uranium, plutonium, and americium in the wastewater and form large particle flocs. Subsequently, it enters the ultrafiltration unit after being pressurized by a water pump, and the residual radioactive nuclides in the wastewater are further removed by ultrafiltration.

[0017] In summary, this oxidation - flocculation - ultrafiltration treatment process for low - level radioactive wastewater, by setting up a pretreatment unit, an oxidation / flocculation unit, an ultrafiltration unit, and a deionized exchange system, solves the problems that the basic treatment process cannot have the functions of oxidation, pH adjustment, flocculation, and ultrafiltration at the same time, and has a low concentration multiple for low - level radioactive wastewater and a general purification efficiency.

Claims

1. Low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process, characterized in that: The following steps are involved: A: Pre-treatment unit: The radioactive wastewater is treated by filtering to obtain wastewater without large impurities; B: Oxidation / flocculation unit: adding an oxidant to the filtered wastewater for reaction, then adding NaOH to adjust the pH value of the wastewater, and finally adding a flocculant to form wastewater with precipitates, thereby obtaining wastewater with flocculants; C: Ultrafiltration unit: The flocculated wastewater is separated and purified again using an ultrafiltration membrane to obtain purified wastewater; D: Deionization exchange system: The wastewater after ultrafiltration is deeply purified using ion exchange resin to obtain purified water again.

2. The low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process according to claim 1 is characterized by: In the step A, the filter pore size of the pre-treatment unit is 1-5 μm.

3. The low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process according to claim 1 is characterized by: In the step B, FeSO4 solution and KMnO4 solution are added into the filtered wastewater by using multiple dosing pumps, and the reaction time is 4-7 minutes; HNO3 solution is added into the wastewater, and the reaction time is 4-8 minutes.

4. The low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process according to claim 1 is characterized by: In the step B, NaOH solution is added into the wastewater by using a dosing pump, and the reaction time is 5-7 minutes; flocculant is added into the wastewater, and the reaction time is 5-10 minutes, and the standing time is 2-4 minutes.

5. The low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process according to claim 1 is characterized by: In the step B, during operation, the motor drives the blades to stir, the motor speed is and cooperates with the air compressor to perform aeration treatment.

6. The low-level radioactive wastewater oxidation flocculation ultrafiltration treatment process according to claim 1, characterized in that: In the step C, the pore size of the ultrafiltration membrane is 10-100 nm, and an air compressor is used for aeration treatment.

Images